{"1": {"fulltext": "", "height": "2620", "width": "1747", "jp2-path": "roperscatechismf00rope_0001.jp2"}, "2": {"fulltext": "Class JLI^Jp,\\nBook__S_:]_l^\\nGoipglit^l?\\nCOPyRIGHT DEPOSIE", "height": "2824", "width": "1778", "jp2-path": "roperscatechismf00rope_0002.jp2"}, "3": {"fulltext": "", "height": "2824", "width": "1778", "jp2-path": "roperscatechismf00rope_0003.jp2"}, "4": {"fulltext": "", "height": "2845", "width": "1804", "jp2-path": "roperscatechismf00rope_0004.jp2"}, "5": {"fulltext": "m\\n26 ^90^\\n/5", "height": "2845", "width": "1804", "jp2-path": "roperscatechismf00rope_0005.jp2"}, "6": {"fulltext": "ROPER^S\\nPractical Hand -Books\\nFor Engineers and Firemen.\\nNEW REVISED AND ENLARGED EDITION.\\nHANDY-BOOK FOR STEAM ENGINEERS\\nAND ELECTRICIANS.\\nPRICE, $3.50.\\npRice.\\nRoper^s Catechism for Steam Engineers and Electric-\\nians, $2.00\\nRoper s Questions and Answers for Steam Engineers\\nand Electricians, 2.00\\nRoper s Hand-Book of Land and Marine Engines, 3.50\\nRoper s Care and Management of the Steam Boiler, 2.00\\nRoper s Use and Abuse of the Steam Boiler, 2.00\\nRoper s Young Engineers Own Book, 2,50\\nRoper s Hand-Book of the Locomotive, 2.50\\nRoper s Instructions and Suggestions for Engineers\\nand Firemen, 2.00\\nRoper s Hand-Book of Modern Steam Fire Engines, 3.50\\nDAVID MCKAY, Publisher,\\n1022 Market Street, Piiiladelpiiia, Pa.", "height": "2838", "width": "1854", "jp2-path": "roperscatechismf00rope_0006.jp2"}, "7": {"fulltext": "ROPER S CATECHISM\\nFOR\\nSTEAM ENGINEERS\\nAND\\nELECTRICIANS\\nINCLUDING THE CONSTEUCTION AND MANAGEMENT OF\\nSTEAM ENGINES, STEAM BOILERS AND\\nELECTRICAL PLANTS\\nWITH ILLUSTRATIONS\\nEDWIN R. KELLER, M.E.\\nAND\\nCLAYTON W. PIKE, B. S.\\nPHILADELPHIA\\nDAVID McKAY, Publisher,\\n1022 Market Street", "height": "2838", "width": "1804", "jp2-path": "roperscatechismf00rope_0007.jp2"}, "8": {"fulltext": "Offlcoofthe\\n600 33\\nEntered, according to Act of Congress, in the year 1873, by\\nSTEPHEN ROPER,\\nin the Office of the Librarian of Congress, at Washington.\\nEntered, according to Act of Congress, in the year 1884, by\\nE. CLAXTON COMPANY,\\nin the Office of the Librarian of Congress, at Washington.\\nCopyright by DAVID McKAY, 1897.\\nCopyright by DAVID McKAY, 1899.\\nSECOND copy.\\n^3", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0008.jp2"}, "9": {"fulltext": "PREFACE TO THE TWENTY-FIRST EDITION.\\nThe great value of a catechism lies in the fact\\nthat judicious questioning emphasizes the more\\nimportant points of a subject and also stimulates\\nthe mind of the student to think more definitely\\nand clearly upon the subject than would be the\\ncase in merely reading about it. In these respects\\nthe written catechism is the best substitute for\\noral teaching, and the authors trust that this\\nvolume will be found of value for this purpose.\\nThe enactment of State laws requiring the\\nlicensing of engineers has imposed upon many\\nthe necessity of passing examinations for license.\\nThe authors likewise hope that it will prove\\nuseful to engineers in preparing for such exam-\\ninations.\\nEdw^in R. Keller,\\nClayton W. Pike.\\nPhiladelphia, September, 1899.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0009.jp2"}, "10": {"fulltext": "", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0010.jp2"}, "11": {"fulltext": "CONTENTS.\\nFor Alphabetical Index to Subjects, see page 359.\\nMechanics. p^^j.\\nThe Six Mechanical Elements of Machinery, 1\\nForce, 1\\nInertia, 2\\nMotion, 3\\nVelocity, 4\\nAcceleration, 4\\nFalling Bodies, 5\\nMass and its Relation to Force and Acceleration, 6\\nMomentum, 7\\nEnergy or Work, 8\\nPower, 10\\nHorse-power, 10\\nParallelogram of Forces, 11\\nMoment or Statical Moment, 11\\nThe Lever, 13\\nThe Wheel and Axle, 16\\nThe Wedge, 16\\nThe Pulley, 16\\nThe Screw, 17\\nTransmission and Measueement of Powee.\\nMethods of Transmitting Power, 18\\nShafting, 18\\nBelting, 20\\nvii", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0011.jp2"}, "12": {"fulltext": "Vlll CONTENTS.\\nPAGE\\nVelocity of Belts, 20\\nPower Transmitted by Belts, 20\\nCalculation of Width of Belt for a Given Horse-\\npower, 20\\nCalculation of Length of Belt Needed, 21\\nRope Driving, 22\\nGearing, 23\\nSpur Gears, 24\\nFriction Clutches, 25\\nPneumatic Transmission of Power, 25\\nCompound Compressor, 26\\nThe Intercooler, 27\\nReservoirs or Receivers, 27\\nFlow of Compressed Air Through Pipes, 28\\nEfliciency of Compressed Air Systems, 28\\nElectric Transmission of Power, 29\\nTypes of Motors, 30\\nCalculation of Line, 31\\nLubricants, 32\\nBest Lubricants for Different Purposes, 32\\nOil Separators, 32\\nMeasurement of Power, 33\\nDifferent Methods Available, 33\\nIndicator Method, 33\\nElectrical Method, 34\\nProny Brake Method, 35\\nHEAT, FUEL, GASES, WATER, AND STEAM.\\nHeat.\\nNature of Heat, 37\\nTemperature, 37\\nThe Thermometer, 38", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0012.jp2"}, "13": {"fulltext": "CONTENTS. IX\\nPAGE\\nThermometer Scales, 39\\nDiagram for Changing from Centigrade to Fahren-\\nheit Degrees, 39\\nSpecific Heat, 41\\nLatent Heat, 41\\nUnit of Heat, 41\\nMechanical Equivalent of Heat, 42\\nMethods of Transferring Heat Radiation, 42\\nConduction of Heat, 42\\nConducting Power (for heat) of Various Substances, 42\\nCombustion and Fuels.\\nNature of Combustion, 44\\nSmoke, 44\\nFuel, Nature and Constituents of, 45\\nCarbon, 45\\nAir Required to Burn 1 Pound, 47\\nValue of Wood as Fuel Compared to Coal, 47\\nHeat Evolved from Various Fuels, 48\\nHydrogen in Fuel, 49\\nLiquid Fuels Petroleum, 49\\nAlE.\\nOxygen, Nitrogen, and Hydrogen, 51\\nAir\u00e2\u0080\u0094 the Atmosphere, 52\\nAtmospheric Pressure, 52\\nVolume of Air at Various Temperatures, 53\\nThe Barometer, 54\\nMeasurement of Heights by the Barometer, 55\\nWater.\\nComposition of Water and Its Properties, 56\\nSpecific Gravity of Water, 56", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0013.jp2"}, "14": {"fulltext": "X CONTENTS.\\nPAGE\\nPhysical States, 67\\nWeight of a Cubic Foot of Water, 57\\nBoiling Point, 58\\nSpecific Heat, 59\\nFlow of Water, Head, 60\\nCalculation of Pressures Corresponding to Various\\nHeads, 61\\nFlow from an Orifice in the Bottom of a Tank, 61\\nFlow of Water Through Pipes, 62\\nLoss of Head by Friction in Pipes, 63\\nSteam.\\nSteam and its Properties, 64\\nVolume of Steam 64\\nSaturated Steam, 65\\nSuperheated Steam, 65\\nLatent Heat of Steam, 66\\nTotal Heat of Steam, 67\\nWhat the Gauge Indicates, 68\\nCondensation of Steam, 68\\nTHE STEAM BOILER.\\nPlain Cylindrical Boiler, 75-77\\nCornish Boiler, 77\\nLancashire Boiler, 79\\nGalloway Boiler, 80\\nFire-tube Boilers, 81\\nWater-tube Boilers, 84\\nAdvantages of Water- tube Boilers, 84\\nMarine Boilers, 87\\nLocomotive Boilers, 89\\nHorse-power Rating of Boilers, 91", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0014.jp2"}, "15": {"fulltext": "CONTENTS. XI\\nPAGE\\nEvaporative Power, 92\\nGrate and Heating Surface, 95\\nBoiler Materials, 100\\nMethods of Riveting, 100\\nStrength of Boilers, 102\\nBoiler Setting, 109\\nCaee and Management of Boilers.\\nWater Level, Ill\\nFiring, 112\\nCleaning and Blowing Off, 116\\nScale Formation and Corrosion, 123\\nFoaming, 125\\nPriming, 127\\nADJUNCTS OF STEAM BOILERS.\\nThe Safety Valve.\\nSafety Valves, 128\\nSpring-pop Valves, 130\\nRules and Formulae for Safety Valves, 131\\nSteam Pressure Gauges, 138\\nWater Columns and Gauge Cocks, 138\\nVacuum Gauges, 139\\nSalinometer, 141\\nThe Econometer, 141\\nImportance of Correct Supply of Air to the Boiler\\nFurnace, 142\\nPumps and Injectors.\\nClassification of Pumps, 142\\nPower Required to Raise Water, 145\\nCapacity of a Pump, Calculation of, 145", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0015.jp2"}, "16": {"fulltext": "L CONTENTS.\\nPAGE\\nBoiler Feed Pumps, 145\\nPumps for Hot Water, 146\\nInjectors and Their Action, 146\\nFailure of Injectors to Work, 149\\nSetting up Injectors, General Directions, 150\\nInspirators, 151\\nEjector or Lifter, 151\\nComparison of Pumps with Injectors, 152\\nAdvantages of Heating Feed-water, 153\\nClosed Type of Feed-water Heaters, 1 55\\nOpen Feed- water Heaters, 155\\nEconomizers, 159\\nFurnaces and Flues, Pressure Eequired to Collapse, 1 60\\nMethods of Strengthening, 162\\nGrates, 163\\nShaking Grates, 164\\nAutomatic Firing, 165\\nChimneys and Stacks, 167\\nProportioning Stacks, 168\\nTable of Sizes of Chimneys for Various Sizes of\\nBoilers, 170\\nSteam Separators, 171\\nSteam Traps, 173\\nTHE STEAM ENGINE.\\nClassification and General Description.\\nInvention, 175\\nHorse-power of Engines, 177\\nMean Effective Pressure, Calculation of, 180\\nClassification of Engines, 188\\nSimple and Multiple Expansion Engines, 191", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0016.jp2"}, "17": {"fulltext": "CONTENTS. Xlll\\nPAGE\\nHigh-speed Engines, 194\\nThrottling and Automatic Cut-off Engines, 195\\nValves and Valve Geaes.\\nVarious Kinds of Valves and Valve Gears, 197\\nThe Slide Valve and Its Action, 199\\nThe Zeuner Valve Diagram, 202\\nHow to Set Valves, 2U5\\nBalanced Valve, 207\\nCorliss Gear, 207\\nPiston Valve, 207\\nSeparate Valves for Admission and Exhaust, 207\\nSteam Engine Goveenoes,\\nGeneral Principles of Operation, 209\\nThrottling Governors, 209\\nMethod of Action of Fly-wheel Governors, 211\\nInstallation, Caee, and Management.\\nFoundations, 213\\nHow to Set Up an Engine, 214\\nPiping Engines, 216\\nInstructions for Care of Engines, 217\\nPiston-rod and Valve Packing, 218\\n3 of Knocking and Remedies, 221\\nADJUNCTS OF THE STEAM ENGINE.\\nThe Steam Engine Indicatoe.\\nDescription of, o 224\\nTabor s Indicator, 225\\nHow to Attach the Indicator, 226", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0017.jp2"}, "18": {"fulltext": "XIV CONTENTS.\\nPAGE\\nAnalysis of Indicator Diagrams, 228\\nMean Effective Pressure, 229\\nHow to Calculate the Horse-power from a Card, 231\\nCONDENSEES.\\nObject of a Condenser, 233\\nSurface Condenser, 233\\nJet Condensers^ 233\\nThe Vacuum, 234\\nPower Gained by Using Condenser, 234\\nMATERIALS AND THEIR PROPERTIES.\\nComposition and General Peoperties.\\nElements of Matter, 236\\nAtoms and Molecules, 237\\nProperties of Metals, 238\\nSpecific Gravity, 239\\nIron Wrought and Cast, 240\\nSteel, 241\\nEffect of Rise of Temperature on Tensile Strength\\nof Iron, 242\\nCopper, 242\\nVariation of Strength with Rise of Temperature, 242\\nAlloys, 243\\nStrength of Mateeials.\\nTensile and Crushing Strength, 244\\nWrought Iron Tensile and Crushing Strength, 245\\nStrength of Woods, 245\\nFactors of Safety, 245\\nBeams, 246\\nColumns, 247", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0018.jp2"}, "19": {"fulltext": "ELECTRICITY.\\nFundamental Experiments, Properties, and Units.\\nPAGE\\nFundamental Experiments, 248\\nAmpere s Rule, 252\\nResistance, 252\\nLines of Magnetic Force, 254\\nMagnetic Lines of Force Due to a Current, 256\\nGalvanometer, 258\\nElectric Pressure Produced by Induction, 259\\nFleming s Rule for Direction of Induced Currents, 260\\nElectro-motive Force, 266\\nUnits, 267\\nThe Ampere, Volt, Ohm, and Watt, 268\\nResistance, 270\\nConductivity, 270\\nResistances in Multiple, 271\\nResistances in Series, 271\\nSpecific Resistance, 272\\nTable of Relative Resistances of Conductors, 273\\nPractical Use of Conductors and Insulators, 274\\nCurrent Effects Heating, 274\\nElectrolytic Effects, 277\\nElectro-motive Force, Methods of Producing, 278\\nOhm s Law and Its Application, 280\\nCalculation of Current in Divided Circuits, 282\\nElectrical Measurement.\\nQuantities to be Measured and Instruments\\nNeeded, 285\\nMeasurement of Current, 285\\nMeasurement of Electro-motive Force, 287", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0019.jp2"}, "20": {"fulltext": "XVI CONTENTS.\\nPAGE\\nMeasurement of Resistance, 288\\nMeasurement of Power, 291\\nElectric Batteries.\\nChemical Generators, 292\\nSecondary or Storage Batteries, 292\\nPrimary Batteries, 293\\nOpen-circuit Cells, 293\\nClosed-circuit Cells, 295\\nDaniellCell, 295\\nBichromate Cell, 296\\nDry Cells 296\\nDynamos,\\nFunction of a Dynamo, 297\\nIdeal Simple Dynamo, 297\\nThe Armature, 299\\nRing Armatures, 299\\nDrum Armatures, 299\\nArmature Cores, 300\\nThe Field, 300\\nClassification of Dynamos\u00e2\u0080\u0094 Series, Shunt, and\\nCompound, 300\\nRegulation of Shunt Dynamos, 302\\nDistribution of Electrical Energy.\\nAnalogy to Water System, 303\\nThe Switchboard and Its Uses, 304\\nCircuit Breakers, 304\\nGround Detector, 306\\nRunning Generators in Multiple, 307\\nSystems of Distribution, 308\\nSeries System, 308", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0020.jp2"}, "21": {"fulltext": "CONTENTS. XVll\\nPAGE\\nParallel System, 309\\nModified Systems, Three-wire, 311\\nAdvantages of Using High Pressures, 312\\nSize of Conductors Needed, 312\\nSafe Carrying Capacity of Wires, 313\\nTable of Properties of Copper Wire, 315\\nMethods of Carrying Conductors, 316\\nElectric Lighting.\\nArc Lamps Classification, 320\\nRequirements for Successful Operation, 320\\nConstant Potential Arcs, 321\\nOpen Arcs, 322\\nClosed Arcs, 322\\nIncandescent Lamps, 323\\nThe Filament, 324\\nCandle Powers in Commercial Use, 325\\nLife and Efficiency of Lamps, 326\\nEecteic Motors.\\nThe Motor a Dynamo Reversed, 327\\nUses of Series, Shunt, and Compound Motors, 328\\nRegulation of Speed, 328\\nProtective Devices, 330\\nSize and Speed of Motors, 332\\nMotor Generators, 333\\nThe Storage Battery.\\nThe Chloride Battery, 334\\nPhenomena of Charge and Discharge, 335\\nPrincipal Sources of Trouble, 336\\nAdvantages in the Use of Cells, 336\\nCapacity of Storage Cells, 337", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0021.jp2"}, "22": {"fulltext": "XVlll CONTENTS.\\nPAGE\\nEfficiency, 337\\nMethod of Connecting Batteries, 338\\nElecteic Signals.\\nElements of all Signal Systems, 341\\nElectric Bells Single Stroke, 342\\nVibrating Bells, 342\\nCommon Arrangements of Bells, 343\\nThe Annunciator, 344\\nFire Alarm Attachment, .345\\nBurglar Alarm Systems, 346\\nWatchmen s Time Systems, 347\\nBatteries Eequired for Signal Systems, 349\\nThe Telephone.\\nProperties of Sound, 350\\nTelephonic Transmission of Speech Receiver and\\nTransmitter, 35 1\\nMagneto Receiver, 352\\nBattery Transmitter, 353\\nImproved Forms of Transmitter, 354\\nThe Induction Coil, 354\\nThe Magneto Call, 355\\nTelephone Systems, Intercommunicating, 355\\nExchange Systems, 35(3", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0022.jp2"}, "23": {"fulltext": "ROPER S CATECHISM\\nFOR\\nSTEAM ENGINEERS\\nAND\\nELECTRICIANS.\\nMECHANICS.\\nQ. Of what elements are all machines made up?\\nA. Of six, known as the six mechanical ele-\\nments. These are the lever, pidley, wheel and axle,\\ninclined plane, ivedge, and the screw.\\nQ. For w^hat is machinery nsed\\nA. To make force available for practical pur-\\nposes. Machinery does not create force, but trans-\\nmits it, diffusing it, concentrating it, or changing\\nits direction.\\nQ. What is force\\nA. Force is that which produces motion or\\ntends to produce it. If a force acting on a body\\nmeets with a resistance equal and opposite to it,\\nno motion results, but pressure is exerted on the\\nparticles of the body. But if the force is not\\nbalanced, motion will take place.\\n1 1", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0023.jp2"}, "24": {"fulltext": "A roper s catechism for\\nQ. What two varieties of force are there?\\nA. External and internal. External forces are\\nthose exerted by bodies on other bodies. Internal\\nforces are those exerted by the particles of a body\\non neighboring particles. The force of steam\\nagainst the walls of the pipe or vessel containing\\nit, is external. Each particle of steam exerts an\\nequal amount of force on its neighbor, and this is\\nan example of internal force.\\nQ. What is the difference betAveen force and\\npressure\\nA. Pressure is a particular case of force. An\\nexternal force which, on account of a balancing\\nresistance does not produce motion, is generally\\nreferred to as a pressure.\\nQ. What is weight?\\nA. The weight of a body is the force exerted by\\nthe earth on it (an equal amount of force is\\nexerted by it on the earth). When a body rests\\non another body the upper body exerts upon the\\nlower body a pressure or foixe equal to its iveight.\\nThe lower body exerts, of course, an equal and\\nopposite force on the upper.\\nQ. What is meant by inertia\\nA. That property of matter by virtue of which\\nit tends to resist a change of state. Thus, if a\\nbody is at rest its inertia makes it offer a resist-\\nance to any attempt to put it in motion. If a", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0024.jp2"}, "25": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 6\\nbody is in motion its tendency is to keep moving,\\nand it will do so unless some force is applied to it\\nto bring it to rest.\\nQ. What is motion\\nA. Motion is that property which matter has\\nwhile it is changing its position.\\nQ. How would you understand the term abso-\\nlute motion f\\nA. As a change of position, with reference to\\nsome fixed point in space.\\nQ. What does relative motion signify\\nA. Change of position, with reference to some\\nother body which we are for the moment consider-\\ning. Thus two cars in the same train have rela-\\ntive motion with regard to the station which they\\nhave left. They have, however, no motion rela-\\ntive to each other.\\nQ. What is uniform motion\\nA. Uniform motion is that in which equal\\nspaces are always passed over in equal amounts\\nof time.\\nQ. W^hat is variable motion?\\nA. That in which equal spaces are passed over\\nin unequal amounts of time.\\nQ. What is accelerated motion\\nA. That in which the space passed over in one\\nsecond is continually increasing or diminishing.\\nQ. AVhat are Newton s laws of motion", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0025.jp2"}, "26": {"fulltext": "4 ROPER S CATECHISM FOR\\nA. First. A body at rest will remain at rest, or\\nif in motion will continue to move uniformly in\\na straight line till it is acted upon by some force.\\nSecond. If a body be acted upon by several\\nforces it will obey each, as if the others did not\\nexist, and this will be the case whether the body\\nbe at rest or in motion.\\nThird. If a force act to change the state of a\\nbody with respect to rest or motion, the body will\\noffer a resistance equal to and directly opposed to\\nthe force. Or to every action there is opposed an\\nequal and opposite reaction.\\nQ. What is perpetual motion and why is it im-\\npossible\\nA. See explanation in Roper s Engineers\\nHandy-Book, pages 6 and 7.\\nQ. What is velocity\\nA. Velocity is the rate at which motion takes\\nplace. If a body moves over a distance of 100\\nfeet in 10 seconds, its velocity is 10 feet per second.\\nQ. What is uniform velocity\\nA. Velocity is uniform when equal spaces are\\npassed over in equal times. If this is not the\\ncase the velocity is said to be variable.\\nQ. What is acceleration\\nA. Acceleration is the rate at which the velocity\\nchanges, that is, the gain (or loss, as the case may\\nbe) in velocity in 1 second.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0026.jp2"}, "27": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 5\\nQ. What case of accelerated motion can you\\nmention?\\nA. That of a freely falling body which starts\\nfrom rest, falls 16.1 feet the first second, 48.3 feet\\nthe next second, and so on.\\nQ. What are the simple formulae which enable\\nus to calculate the performance of falling bodies,\\nwhen the influence of the friction of the air is\\nconsidered of no importance\\nA. v l/64.4 h and h 16.1 i\\\\\\nQ. What is the meaning of the letters in these\\nformulae\\nA. V velocity in feet per second;\\nh height through which the body has\\nfallen, in feet;\\nt number of seconds required to fall\\nthrough the distance h.\\nQ. If a body falls from a height of 100 feet,\\nwhat velocity will it have when it reaches the\\nearth s surface?\\nA. v V 64.4 X 100 1/ 6440 80.2 feet\\nper second.\\nQ. How long will it take for the body to fall\\nthrough 100 feet?\\nA. h= 16.1 t or t therefore\\nlb. 1\\nt \\\\j^ 2.49 seconds.\\n100\\n16.1", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0027.jp2"}, "28": {"fulltext": "6 roper s catechism for\\nQ. What is the acceleration produced by gravity?\\nA. It is at the surface of the earth, about 32.2\\nfeet per second, and diminishes as we go up from\\nthe earth s surface.\\nQ. What is the mass of a body\\nA. It is the quotient of the weight of the body\\ndivided by the value of the acceleration due to\\ngravity.\\nQ. Is the weight of a body everywhere the\\nsame?\\nA. No; it diminishes as we rise from the earth s\\nsurface.\\nQ. Is the mass always the same\\nA. Yes; for though the weight changes, the\\nvalue of the acceleration due to gravity changes\\nto the same extent; therefore the quotient of the\\ntwo is constant, and this by definition is the mass.\\nQ. When a force is applied to a body at rest\\nwhat is the effect\\nA. The body is put in motion which is uni-\\nformly accelerated. The acceleration produced is\\nproportional to the force, as double the force act-\\ning on the same body will produce twice as much\\nacceleration.\\nQ. If the same force is applied to a bod} weigh-\\ning 10 pounds and to another weighing twice as\\nmuch, on which will it produce the greater acceler-\\nation", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0028.jp2"}, "29": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 7\\nA. On the 10-pound body it will produce\\ndouble the acceleration that it will on the 20-\\npound body.\\nQ. What general rule can you give for the rela-\\ntion between force, mass, and acceleration\\nA. The force (in pounds) the mass X accel-\\neration or with sufficient accuracy for most pur-\\nthe weisfht in pounds\\nposes, the lorce X the\\nacceleration in feet per second.\\nQ. What acceleration will a force of 20 pounds\\nproduce if applied to a body weighing 20 pounds\\nA. F (force) v q X A (acceleration),\\n32.2 X F\\nox A^\\nW\\n32.2 X 20\\n32.2 feet per second.\\n20\\nThis case is that of a freely falling body where\\nthe force due to its weight acts upon its mass tend-\\ning to accelerate it.\\nQ. What is the momentum of a moving body\\nA. It is the force which acting upon it for 1\\nsecond will bring it to rest. It is equal to the\\nproduct of the mass of the body by its velocity.\\nQ. Has a body at rest any momentum\\nA. No; for its velocity is zero, and hence the\\nproduct of mass times velocity is zero also.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0029.jp2"}, "30": {"fulltext": "O ROPER S CATECHISM FOR\\nQ. What is work in the science of Mechanics?\\nA. Work involves two things, force and space,\\nand the amount of work is equal to the product\\nof force by space. If either is absent no work is\\ndone.\\nQ. What is the unit of work\\nA. The foot-pound, which is the amount of work\\nperformed in raising a weight of 1 pound through\\na height of 1 foot.\\nQ. What example can you give of forces acting\\nwithout work being done\\nA. A weight resting on a table exerts force, but\\nas there is no motion no work is being done by\\nthe weight.\\nQ. Was work done in placing the weight on the\\ntable?\\nA. Yes; if the height of table is 4 feet and the\\nweight is 10 pounds, the amount of work done\\nwas 40 foot-pounds.\\nQ. What is energy\\nA. Energy is the power of doing work. For\\nexample, the weight on the table has the power\\nto do w^ork if it is allowed to fall from the height\\nof the table.\\nQ. How many forms of energy are there\\nA. Two, potential energy and kinetic energy.\\nThe energy in the weight above mentioned is a\\ncase of potenticd energy. A body in motion has also", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0030.jp2"}, "31": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 9\\nthe capacity for doing work stored up in it, and the\\nenergy resident in moving bodies is called kinetic\\nenerg}^\\nQ. Can you give other examples of potential\\nenergy\\nA. A spring in tension or compression, a tank\\nof water at a height, a reservoir of compressed\\nair, a piece of coal.\\nQ. Give some examples of kinetic energy.\\nA. A moving train, a cannon ball, a fly-wheel,\\na stream of water, the waves of the ocean, heat,\\nelectric -current flow.\\nQ. What is the formula for the energy in a\\nmoving body?\\nM X V\\nA. E (energy in foot-pounds) where\\nM is the mass and V the velocity of the moving\\nbody in feet per second. In more convenient form,\\nTT X F^\\nE where W is the weight in pounds.,\\nQ. How much energy is stored up in the piston\\nand piston-rod of an engine if the speed of the\\npiston is 600 feet per minute, and their weight is\\n100 pounds?\\n100 X 60 X 60 _\u00e2\u0080\u009e\u00e2\u0080\u009e\\nA. E ^^^-j 5590 foot-pounds.\\nQ. What is the primary source of energy on the\\nearth", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0031.jp2"}, "32": {"fulltext": "10 roper s catechism for\\nA. The rays of the sun which raise water from\\nsea-level to the clouds from which it falls in rain,\\nand which causes the growth of plants from which\\nhas come our coal.\\nQ. What is the principle of conservation of\\nenergy\\nA. That the amount of energy in the universe\\nis fixed and cannot be changed by man. He can\\ntransmit it and alter the form in which it appears,\\nas from potential to kinetic, but can in no wise\\ncreate or destroy it.\\nQ. What is power\\nA. Power is the rate at which work is done, or\\nat which energy is changed from one form to\\nanother; thus, if a man lifts in one hour 100\\nweights of 100 pounds each to a height of 4 feet,\\nhe has done work at the rate of 100 X 100 X 4,\\nor 40,000 foot-pounds per hour.\\nQ. What is meant by a horse-power\\nA. Doing work at the rate of 33,000 foot-\\npounds per minute.\\nQ. In the example above, what horse-power is\\nthe man doing?\\nA. 40,000 foot-pounds per hour foot-\\npounds per minute, or 666f foot-pounds per\\n*See also Roper s Engineers Handy-Book, images 14\\nand 15.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0032.jp2"}, "33": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 11\\n2\\nminute 666f -v- 33,000 j^ horse-power\\nvery nearly.\\nQ. What is the rule for obtaining the horse-\\npower\\nA. To obtain the work done multiply the force\\nin pounds by the distance in feet.\\nTo obtain the power divide this product by the\\ntime required to do the work, in minutes.\\nTo obtain the horse-power divide further by\\n33,000.\\nQ. How can forces be conveniently represented\\nso as to calculate the effect which they will pro-\\nduce on a body\\nA. We represent each force by a line whose\\ndirection represents the direction of the force, and\\nwhose length is proportional to the amount of the\\nforce.\\nQ. What is the principle known as the paral-\\nlelogram, of forces f\\nA. If two forces acting on a body be represented\\nby two lines forming two adjacent sides of a\\nparallelogram (their lengths being proportional to\\nthe strength of the forces and their directions the\\nsame as those of the forces), the diagonal of the\\nparallelogram will represent what is called the\\nresultant of the two forces, namely, a force which\\nacting alone would produce on the body the same", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0033.jp2"}, "34": {"fulltext": "12 roper s catechism for\\neffect as would the two forces. The direction of\\nthe diagonal represents the direction of the result-\\nant or equivalent force, and its length represents\\nthe strength of that force.\\nQ. What is the resultant force which will equal\\ntwo forces of 3 and 4 pounds, acting at the same\\npoint and at an angle of 90 degrees\\nA. Lay out the line A B with 4 units of length\\nto represent the force of 4 pounds, and A C with\\n3 units of length at right angles to A B, to repre-\\nsent the other force.\\nComplete the parallelo-\\ngram by drawing B D\\nand C D; then the diag-\\nonal A D will represent\\nthe resultant, and if\\nmeasured or calculated\\nits length will be found to be 5 units. The result-\\nant force will then be 5 pounds exerted at an\\nangle of 36\u00c2\u00b0 53^ to the hne A B.\\nQ. What will be the resultant of a force of 10\\npounds in one direction and a force of 5 pounds\\nacting in the same line but in the opposite direc-\\ntion\\nA. 10 less 5, or 5 pounds. When the forces are\\nparallel or in the same line no parallelogram can\\nbe formed.\\nQ. What is the moment of a force", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0034.jp2"}, "35": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 13\\nA. It is the number which represents its ten-\\ndency to cause rotation about a certain point. For\\nexample, if a stick 5 feet long is pivoted at one\\nend and if a force of 5 pounds be applied at the\\nother end, the force would tend to make the stick\\nrotate about the pivot point. This tendency\\nwould be greater if the force were greater or if the\\nlength of the stick were greater. It is, in fact,\\nproportional to the product of the force by the\\nperpendicular distance from the pivot point to\\nthe line of direction of the force, and this product\\nis technically known as the moment of the force\\nabout the pivot point.\\nQ. What is the particular value of the idea of\\nmoments\\nA. It gives a simple treatment of levers and\\nquestions governing the rotation of bodies.\\nQ. AVhat is the general principle of moments\\nas applied to levers\\nA. When two forces are acting at different\\npoints in the same body, if the moments, taken\\nabout a given point, of the forces are equal and\\nopposed in direction, the body will be at rest,\\notherwise the body will be set in motion. When\\nthere are more than two forces they may be\\ndivided into two sets, one set tending to rotate\\nthe body in one direction about the point, and the\\nother set tending to rotate the body in the other", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0035.jp2"}, "36": {"fulltext": "14 roper s catechism for\\ndirection. If the sum of the moments of the\\nfirst set of forces is equal to the sum of the\\nmoments of the second set, the body will be at\\nrest; but if the sums of the moments of the two\\nsets of forces are unequal, the body will be set in\\nmotion.\\nQ. How does this principle apply to levers\\nA. In the use of levers, as, for example, the case\\nof a man trjdng to raise a rock by means of a\\ncrowbar, we have three forces applied at three\\ndifferent points of the crowbar, one force the\\nstrength of the man, another the weight of the\\nrock, and the third the upward thrust of the point\\nof support. By taking moments about the point\\nof support, the moment of the third force becomes\\nzero, since its lever arm is zero, and the bar is in\\nequilibrium under the action of two equal moments.\\nIf one force is known, as, for example, the weight\\nof the rock, we can calculate the force which must\\nbe applied by the man. If the moment of the\\nforce used by the man is the greater, he will move\\nthe rock; if less, he cannot do so.\\nQ. What three classes of levers are there\\nA. First Those in which the fulcrum or point\\nof support is between the applied force and the\\nresisting force.\\nSecond. Those in which the resisting force is\\nbetween the applied force and the fulcrum.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0036.jp2"}, "37": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 15\\nThird. Those in which the apphed force is\\nbetween the fulcrum and the resisting force.\\nQ. With a lever of the first class, 10 feet long,\\nwhat force must be applied at the end to lift a\\nweight of 9000 pounds, if the fulcrum is distant\\nfrom the weight 1 foot?\\nA. Call the force F. Then by the principle of\\nmoments, when the applied force is just sufficient\\nto balance the weight, i^ X 9 9000 X 1, or i^\\n9000 9 1000 pounds.\\nQ. Is any power gained by using a lever, or,\\nmore accurately speaking, is any energy gained\\nA. No; the same expenditure of work is re-\\nquired to raise a weight of 9000 pounds, whatever\\nmay be the machinery used to perform the work.\\nA lever merely allows a person, too weak to lift a\\ncertain weight with the hands, to do so by taking\\na longer time to perform the act. Looked at from\\nthe standpoint of work, if the 9000 pounds is\\nlifted 1 foot in height, 9000 foot-pounds of work\\nare done. The end of the lever at which the\\nforce of 1000 pounds is applied, moves through a\\ndistance of 9 feet if the other end moves through\\n1 foot. Therefore, the work done, which is always\\nthe product of force times distance through which\\nthe force is exerted, is 1000 X 9, or 9000 foot-\\npounds, the same as if the stone were lifted\\ndirectly.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0037.jp2"}, "38": {"fulltext": "16\\nROPER S CATECHISM FOR\\nIn one sense it may be said that we gain force\\nby the use of the lever, in that we can, by taking\\na longer time to do the work, get along with a\\nsmaller force.\\nQ. How does the wheel and axle differ from a\\nlever\\nA. The wheel and axle may be considered as a\\nlever in which the points of support and resist-\\nance are continually renewed. The center of the\\naxis is the fulcrum, the radius of the wheel is the\\nlong arm and the radius of the axle the short\\narm of the lever.\\nQ. What is the relation between the applied\\nforce and the resulting force in the case of a wedge\\nA. If a force of F pounds be applied at the\\npoint B in the direc-\\ntion B A, the resulting\\nforce W (in a direction\\nperpendicular to A B)\\nwill have the follow-\\ning relation\\nW_ _ len gth A B\\nF length C D*\\nQ. What two kinds of pulleys are there\\nA. The fixed, which only turns on its axis, and\\nthe movable, which moves up and down as well as\\nturns on its axis.\\nQ. What is the use of a fixed pulley?", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0038.jp2"}, "39": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 17\\nA. Merely to change the direction of force.\\nQ. What advantage is gained by a movable\\npulley\\nA. It enables us to raise a weight by the appli-\\ncation of a force half as great as the weight,\\nalthough we take twice as long to do the work.\\nQ. With two movable pulleys what would be\\nthe gain\\nA. We should need a force of only one-quarter\\nthe weight.\\nQ. Does it make any difference whether the\\nmovable pulleys are separate or consist of sheaves\\nmounted in the same case\\nA. No.\\nQ. Give the general rule for finding the force\\nnecessary to lift a certain weight with the ordinary\\nblock and tackle.\\nA, Divide the weight by the number of sheaves\\nhi the movable pulley.\\nQ. What is the rule for finding the force which\\nmust be applied at the end of the lever of a jack-\\nscrcAv in order to lift a certain weight\\nA. Multiply the weight by the pitch of the\\nscrew, in inches, and divide by 6.2832 times the\\nlength of the lever, also expressed in inches.*\\n*For complete explanation, see Eoper s Engineers\\nHandy-Book, pages 23 and 24.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0039.jp2"}, "40": {"fulltext": "18 roper s catechism for\\nPOWER TRANSMISSION AND\\nMEASUREMENT*\\nSHAFTING.\\nQ. What are the principal methods of trans-\\nmitting power\\nA. By shafting with pulleys and belts.\\nBy rope driving.\\nBy gear wheels.\\nHydraulic.\\nPneumatic, by compressed air.\\nElectrical, b}^ dynamos, line, and motors.\\nQ. Why is shafting now made of steel instead\\nof iron?\\nA. Because a steel shaft for the same weight\\nand size is stronger with respect to the twisting\\nstrain, and stiffer as regards transverse strains due\\nto the weight of pulleys and pull of belts.\\nQ. What two requirements must be met by\\nshafting\\nA. It must be large enough to transmit the\\nrequired power at the given speed without being\\ntwisted too much. It must also have sufficient\\nsize to stand the transverse pull due to its own\\nweight, the weight of the pulleys, and the weight\\nand pull of the belts.\\nQ. What general rule should guide the location\\nof hangers?", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0040.jp2"}, "41": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 19\\nA. They should be as near as possible to the\\npulleys, and should not be over 8 feet apart for\\nlight shafting.\\nQ. Give the rule for calculating the diameter of\\na shaft to transmit a certain horse-power at a cer-\\ntain number of revolutions per minute.\\nA. Multiply the horse-power by 70 and divide\\nby the number of revolutions per minute, and\\nextract the cube root of the quotient. The result\\nwill be the diameter of the shaft in inches.\\nQ. What is the rule for obtaining the greatest\\nallowable distance between hangers for a certain\\nsize of shaft?\\nA. Multiply the square of the diameter in\\ninches by 140 and extract the cube root. The\\nresult will be the distance in feet.\\nQ. What is the rule for finding the number of\\nhorse-power which a shaft of a certain diameter\\nwill transmit at a certain speed?\\nA. Multiply the cube of the diameter in inches\\nby the number of revolutions per minute and\\ndivide the product by 70.\\nQ. Can these rules be depended upon for all\\ncases\\nA, No; only for ordinarily heavy pulleys. For\\nany very heavy pulleys the diameters given by\\nthese rules would be too small.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0041.jp2"}, "42": {"fulltext": "20 roper s catechism for\\nBELTING.\\nQ. What are the advantages of leather over\\nrubber belts\\nA. Leather belts have a longer life, and are less\\naffected by oil and by heat and cold. They will\\nstand being run through shifters or crossed.\\nWhen worn they can be cut up into narrower\\nbelts, whereas rubber belts when worn are of no\\nuse.\\nQ. What two points determine the width of a\\nbelt for transmitting a certain horse-power\\nA. The speed at which the belt runs and the safe\\nworking-strain of the belt, which may be taken\\nas 45 pounds per inch width for single belting.\\nQ. How much more power will a belt transmit\\nwhen running at 6000 feet per minute than at a\\nspeed of 3000 feet per minute\\nA. Twice as much.\\nQ. At about what speed is it best to run belts\\nA. Between 4000 and 5000 feet per minute.\\nQ. What is a common rule for determining the\\nwidth of belt to transmit a certain horse-power\\nA. That a belt 1 inch wide, at a speed of 1000\\nfeet per minute, will transmit 1 horse-power; a 2-\\ninch belt will transmit 2 horse-power, and so on.\\nQ. Is this rule a safe one to follow\\nA. Yes; for the most favorable cases, where the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0042.jp2"}, "43": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 21\\nbelts are open and horizontal, with a long distance\\nbetween centers, a narrower belt may be used.\\nQ. Will a belt 30 feet long transmit more power\\nthan the same belt 20 feet long\\nA. Yes, if it is horizontal; for owing to the\\ngreater weight of the longer belt it will sag down\\na little more in the center and give a little greater\\narc of contact on the pulleys.\\nQ. What is the objection to vertical belts?\\nA. The weight of the belt tends to pull it away\\nfrom contact with the lower pulley and, therefore,\\nto transmit a given power a vertical belt must be\\nrun tighter than if it were horizontal. Moreover,\\nwith a horizontal belt the upper side tends to sag\\ndown owing to its weight, and this increases the\\narc of contact with the pulley.\\nQ. Why do the formulae of different authors\\nfor finding the width of belts differ so much\\nA. Because some use a greater permissible ten-\\nsion on the belt than others, which shortens the\\nlife of the belt and renders repairs more frequent.*\\nQ. What is the rule for obtaining the length of\\nan open belt?\\nA. Multiply the sum of the diameters of the\\ntwo pulleys by 3.1416 and divide by 2. To the\\nquotient add twice the distance between centers.\\n*See Belting, Roper s Engineers Handy-Book, pages\\n34-43.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0043.jp2"}, "44": {"fulltext": "22 roper s catechism for\\nQ. Is this rule strictly accurate\\nA. Yes, if the diameters of the pulleys are the\\nsame; if not, the result is slightly too small.\\nQ. How would you measure the length of a belt\\nin a coil\\nA. Add the outside diameter to the diameter of\\nthe hole and divide by 2. This would give the\\nmean diameter which should be expressed in feet.\\nThen multiply this by 3.1416 and the product by\\nthe number of coils in the roll.\\nQ. How would you determine the proper size of\\na driven pulley to run at a certain number of\\nrevolutions per minute, having given the diameter\\nand speed of the driving pulley\\nA. Multiply the diameter of the driver by the\\nnumber of revolutions which it makes per minute\\nand divide the product by the number of revolu-\\ntions which the driven pulley is to make.\\nQ. In arranging for belting, which side should\\nbe the loose side, the upper or lower\\nA. The upper, so that the weight of the belt\\nmay make it sag down and thus make a longer arc\\nof contact between belt and pulleys.\\nQ. What advantages does rope transmission\\nhave over belt driving\\nA. The cost of rope is less than that of belting,\\nand the pulleys do not have to be so accurately\\nlined up.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0044.jp2"}, "45": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 23\\nQ. What are the two general methods of using\\nropes\\nA. First. To put ropes on hke so many parallel\\nspliced belts, one working in each groove of the\\npulley.\\nSecondly. To wrap the rope around the pulleys\\nas many times as there are grooves, then to carry\\nit through idlers so arranged that the tension can\\nbe varied, and then to carry the rope back to the\\nstarting-point and to splice it.\\nQ. What is the objection to the first method?\\nA. The separate ropes do not all pull equally.\\nQ. How is this partially overcome\\nA. By making the grooves of the smaller pulley\\nwith a sharper angle.\\nQ. At what speeds do the ropes run\\nA. At speeds varying from 25 to 100 feet per sec-\\nond, the most common practice being about 80 feet.\\nQ. Can you give any figures showing what\\nhorse-power is transmitted by a certain size rope\\nA. A 1-inch rope at a velocity of 5000 feet per\\nminute will transmit about 13 horse-power.\\nTOOTHED AND FRICTION GEARING.\\nQ. What is the pitch of a gear wheel\\nA. The distance measured along the pitch circle\\nfrom a point on one tooth to the corresponding\\npoint on the next tooth.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0045.jp2"}, "46": {"fulltext": "24 eoper s catechjsm for\\nQ. What is the thickness of a gear tooth\\nA. Its width measured along the pitch circle.\\nQ. What is the space f\\nA. The difference between its pitch and its thick-\\nness.\\nQ. What is backlash f\\nA. The amount by which the space is greater\\nthan the thickness.\\nQ. What are spur gears used for\\nA. To connect parallel shafts.\\nQ. When are bevel gears used\\nA. When it is desired to connect shafts making\\nan angle with each other.\\nQ. What are the two principal forms of gear\\nteeth\\nA. The cycloid and the involute, the latter being\\nused when the number of teeth is small.\\nQ. How would you calculate the diameter or\\nnumber of teeth in a driven wheel to run a certain\\nspeed having given the diameter or number of\\nteeth of the driver?\\nA. Just as the diameter of a driven pulley is\\ncalculated.\\nQ. For what are friction-clutch connections\\nprincipally used\\nA. To take the place of tight and loose pulleys,\\n*See also Roper s Engineers Handy-Book, pages\\n50-52.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0046.jp2"}, "47": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 25\\nand to connect two or more sections of a line of\\nshafting so that the sections may be disconnected\\nor thrown together without, stopping the shaft.\\nQ. Describe the general principle on which most\\nfriction clutches are constructed.\\nA. A pulley is mounted so as to turn freely on\\na sleeve in which the shaft turns. This pulley\\nhas either a special rim attached to the arms or\\nelse a disk attached to the hub, which is gripped\\nbetween the jaws of the clutch device. The\\nclutch is mounted on and keyed to the shaft. The\\njaws of the clutch are made to open or shut by\\nmoving the clutch collar in one direction or another\\nalong the shaft by a fork handle. The motion of\\nthe clutch collar operates some kind of toggle joint\\nwhich moves the jaws; when the jaws are closed\\nso as to grip the rim or disk, the pulley is made\\nto turn with the shaft.\\nCOMPRESSED AIR.\\nQ. What are some of the purposes for which\\ncompressed air is used as a means of transmitting\\npower\\nA. For operating cranes, hoists, drills, rivet-\\ning-machines, coal-mining machinery, railroad\\nsignals, shop tools, sand blasts, brakes, etc.\\nQ. Describe the general method of power trans-\\nmission by compressed air.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0047.jp2"}, "48": {"fulltext": "26 roper s catechism for\\nA. Air is compressed by some form of piston\\npump driven by a steam engine, water wheel,\\nelectric motor, or anj;^ convenient source of power.\\nPipes carry the compressed air to the point where\\nit is to be used, where it is led into the air motor\\nor other machine in which it is to be used.\\nQ. What is the general nature of the air motor\\nA. An ordinary steam engine or steam pump\\nmay be used as a compressed air motor, according\\nas rotary or reciprocating motion is desired. Com-\\nmercial motors differ from these only in form and\\ndetail.\\nQ. Why in steam-driven air compressors is the\\nduplex or compound type used so largely\\nA. With a single steam and single air cylinder\\nthe maximum steam pressure is at the beginning\\nof the stroke, while in the air cylinder the great-\\nest pressure is at the end of the stroke. This is\\nequalized to a great extent by having two cylinders\\nof different sizes and performing the first part of\\nthe compression in the larger and finishing it in\\nthe smaller cylinder.\\nQ. Has the compound compressor any other\\nadvantage\\nA. Yes; it is more efficient, i. e., it com^Dresses\\na greater quantity of air with a given amount of\\nsteam than would a simple compressor.\\nQ. What is the intercooler", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0048.jp2"}, "49": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 27\\nA. A tank containing coils through which runs\\ncold water. This tank is so connected between\\nthe large and small air cylinders that after the\\nair has received the first part of its compression it\\nis led through the intercooler before it passes into\\nthe second compressing cylinder.\\nQ. What is the advantage of the intercooler\\nA. The air being cooled after the first com-\\npression it does not reach so high a temperature\\nin the second cylinder, so that lubrication is much\\neasier moreover, it is found that by using the\\nintercooler a given quantity of air can be com-\\npressed with the use of a less quantity of steam\\nthan would be the case without it.\\nQ. How much of a saving in steam is attained\\nby the cooling of the air?\\nA. About 10 per cent, by the intercooler and 5\\nper cent, by the water jackets around the air-com-\\npressing cylinders.\\nQ. How is the regulation of air pressure main-\\ntained\\nA. By a balanced valve operating a little piston\\nwhich in turn operates another controlling the\\nsteam supply for the steam cylinder of the com-\\npressor.\\nQ. What are receivers and why are they used\\nA. They are steel tanks of suitable size and\\nstrength, placed one near the compressor and one", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0049.jp2"}, "50": {"fulltext": "28 roper s catechism for\\nnear the point where the air is to be used. Their\\nobject is to prevent fluctuations of pressure in the\\nsystem. They thus preserve a steady flow of air\\nin the pipe hne and keep the loss of pressure by\\nfriction down to a minimum.\\nQ. AVhat is a common pressure for compressed-\\nair systems\\nA. 80 pounds.\\nQ. How does the loss of pressure due to fric-\\ntion of air flowing through pipes vary\\nA. In proportion to the length of pipe and in\\nproportion to the square of the velocity or quan-\\ntity per minute which goes through the pipe.\\nQ. Can you give any figures showing the num-\\nber of cubic feet of compressed air used by air\\nmotors\\nA. In small motors of, say, one horse-power\\nabout 700 cubic feet per horse-power per hour;\\nwith large motors as low as 500 cubic feet per\\nhorse-power per hour.\\nQ. What percentage of the power put into the\\nair compressor would j^ou expect to get out of the\\nair motors? In other words, what would be the\\nefficiency of a complete pneumatic transmission\\nsystem\\nA. From 35 to 55 per cent.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0050.jp2"}, "51": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 29\\nELECTRIC TRANSMISSION OF POWER.\\nQ. Describe the general method of transmitting\\npower electrically.\\nA. The energy of a steam engine, water wheel,\\nor other source of power is used to drive an elec-\\ntrical generator or dynamo, which changes energy\\nfrom the mechanical form into the electrical form.\\nThis electrical energy is conveyed from the gener-\\nator by insulated copper wires of suitable size to\\nthe point where it is desired to use the energy.\\nAt that point electric motors or other electric\\ndevices are attached to the wires and change the\\nenergy back again intf the mechanical form.\\nQ. What two classel of transmission are there?\\nA. Transmission by direct current and trans-\\nmission by alternating current.\\nQ. In the electrical transmission of power when\\nwould you, generally speaking, use an alternating\\ncurrent transmission, and why\\nA. When the distance is over 1500 feet, be-\\ncause it requires a smaller conductor to transmit\\na certain power if the pressure used be high than\\nif it be low, and alternating currents can more\\nreadily be changed from high to low pressure than\\ncan direct currents, and are therefore more con-\\nvenient to use when high pressures are employed.*\\n*See also Roper s Engineers Handy-Book, page 65.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0051.jp2"}, "52": {"fulltext": "30 roper s catechism for\\nQ. What three types of direct-current motors\\nare there\\nA. The shunt wound, the series wound, and\\nthe compound wound.*\\nQ. For what class of service are these types\\nused?\\nA. The series motor is used on hoists and\\nstreet-car motors, where constancy of speed is not\\nnecessary, but where a strong starting-torque is\\ndesired. The shunt motor is used for the greater\\npart of the work requiring constant speed, the\\ncompound motor being used in a few special\\ncases.\\nQ. What type of direct-current motor is gener-\\nally used for driving machine tools\\nA. The shunt-wound motor, because it naturally\\nruns at nearly constant speed at all loads.\\nQ. Suppose, as with a lathe, we wish to get\\nseveral different speeds, how is this accomplished\\nA. By a regulating rheostat or controller.\\nQ. What is the gain, in size of wire used on\\nthe line, if we employ a 220-volt system instead\\nof a 110-volt system?\\nA. The 220-volt system requires but one-quarter\\nthe weight of copper in the line.\\nQ. Do any disadvantages occur to you\\nA. The 220-volt line and motor are a little\\nFor a description of these types see page 300.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0052.jp2"}, "53": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 31\\nmore difficult to insulate from the earth, and they\\nare therefore slightly more liable to cause trouble\\nfrom leakage-currents and accidental shocks.\\nQ, Is the shock from 220 volts dangerous\\nA. Not unless taken by a person in exceedingly\\ndelicate health.\\nQ, Is the shock from 550 volts dangerous\\nA. It is exceedingly severe, although rarely, if\\never, fatal.\\nQ. What determines the size of wire to be used\\nfor connecting a generator and motor\\nA. The power to be transmitted, the pressure\\nused, the distance, and the permissible loss in\\npressure.\\nQ. What determines the allowable loss?\\nA. The variation in speed of the motor, between\\nno load and full load, which you are willing to\\nallow.\\nQ. Even with no loss of pressure in the line,\\nwhat variation of speed would you expect with\\nthe average small motor\\nA. About 3 per cent.\\nQ. How would you calculate the size of wire,\\nhaving given the power, pressure, distance, and\\npermissible loss\\nA. See Roper s Engineers Handy-Book,\\npages 67, 717, 718.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0053.jp2"}, "54": {"fulltext": "32 eoper s catechism for\\nLUBRICATION.\\nQ. What is the object of a lubricant?\\nA. To diminish friction by interposing a thin\\nfilm between the revolving or sliding surfaces.\\nQ. Does any lubricant have any tendency to\\nimprove a bearing\\nA. No; it simply keeps the surfaces apart,\\ndiminishes friction and prevents overheating.\\nQ. What are the requirements for a good lubri-\\ncant\\nA. It must have sufficient body to keep the\\nsurfaces apart, but must be as fluid as possible\\nconsistent with this requirement. It must have\\nthe smallest possible friction, must not gum or\\ncorrode; it must have a high flashing-point, and\\nmust remain fluid at the lowest temperature at\\nwhich it will be used.\\nQ. W^hat would you use for slow speeds and\\nheavy pressures on the bearings\\nA. Graphite, soapstone, tallow, or grease.\\nQ. What is an oib separator and on w^hat prin-\\nciple does it operate\\nA. A device for separating the oil from the\\nsteam coming from the exhaust of an engine.\\nThe principle on which it operates is to destroy\\nthe momentum of the oil which is carried along\\nwith the steam. This is accomplished by baffle", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0054.jp2"}, "55": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 33\\nplates which alter or reverse the direction of flow\\nof the steam. The heavy oil particles are thus\\nthrown against the plates and are given time to\\nfall under the action of gravity into a chamber\\nfrom which they may be afterward drawn off.\\nMEASUREMENT OF POWER.\\nQ. What are three common methods of measur-\\ning power\\nA. By means of the steam-engine indicator, by\\nelectrical methods, and by the Prony brake or\\nsome other form of dynamometer.\\nQ. Which is the most accurate\\nA. Whenever the electrical method can be ap-\\nplied it is the quickest and most accurate.\\nQ. How would you determine by the indicator\\nmethod the power used by a certain tool\\nA. By indicating the engine with the tool run-\\nning and without it. The difference in the power\\nshown by the two cards gives the power used by\\nthe tool.\\nQ. Is this method accurate\\nA. Not if the power used by the tool is small\\ncompared to the power of the engine. In this\\ncase it is like trying to weigh a fly on a platform\\nscale, by weighing a man on the scale with the fly,\\nand then weighing the man without the fly and\\nsubtracting one weight from the other.\\n3", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0055.jp2"}, "56": {"fulltext": "34 eoper s catechism for\\nQ. What instruments would you require for the\\nelectrical method, if direct currents were used\\nA. An amperemeter and voltmeter of proper\\nrange or a wattmeter, though the latter is much\\nless commonly at hand.\\nQ. How Avould you measure the power used in\\noperating a tool driven by a direct-current electric\\nmotor\\nA. I would measure the electrical pressure\\nbetw^een the two terminals of the motor by con-\\nnecting to the terminals a voltmeter of suitable\\nrange; I would at the same time find what current\\nwas supplied to the motor by connecting an am-\\nmeter in the circuit suppling the motor; I would\\ntake several readings of both instruments and\\nwould multiply the average reading of the volt-\\nmeter in volts by the average reading of the am-\\nmeter in amperes; this product I would divide\\nby 746, and the quotient would be the electrical\\nhorse-power supplied to the motor; then I would\\nthrow off the belt betw^een the motor and tool and\\nrepeat the measurement above so as to get the\\nhorse-power used by the motor when running\\nidle; subtracting this from the total power sup-\\nplied to the motor would give the power used by\\nthe tool.\\nQ. Will this method be correct if the motor is\\nof the alternating current type", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0056.jp2"}, "57": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 35\\nA. No; for the product of volts and amperes\\ndoes not give the power. In this case a watt-\\nmeter must be used.\\nQ. Describe the Prony brake.\\nA. The Prony brake consists of two or more\\nblocks of wood at-\\ntached to a lever arm, j* ^\u00e2\u0084\u00a2V\\nand so arranged that 3(^^31==\\nthey can be clamped v 9\\nmore or less tightly to\\na pulley or shaft, the\\npower transmitted by which it is desired to measure.\\nQ. How is the powder measured\\nA. When the blocks are clamped to the pulley\\nor shaft the tendency is for the Prony brake to\\nrevolve with the shaft, but weights are put in the\\npan hanging from the end of the brake-arm,\\nuntil this tendency is balanced and the arm stands\\nhorizontal. The number of revolutions, R, the\\nweight, W, and the length, L, from the center of\\nthe shaft to the point of the lever to which the\\nweight pan hangs, are noted. The horse-power is\\ncalculated from the formula\\nWXLXRXQ-28\\nHorse-power\\nor if the distance L is made 5 3 the formula\\nWX R\\nbecomes, Horse-power\\n1000", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0057.jp2"}, "58": {"fulltext": "36 roper s catechism for\\nQ. AVhat may be substituted for the pan and\\nweights\\nA. A spring balance, the average of its read-\\nings being used.\\nQ. What is a dynamometer\\nA. Any instrument used to measure power, as,\\nfor example, the Prony brake.\\nQ. For what purpose is a spring dynamometer\\nused\\nA. For measuring the power required to propel\\nvehicles, such as carriages, street-cars, or railway\\ncoaches.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0058.jp2"}, "59": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 37\\nHEAT, FUEL, AIR, W ATER, AND STEAM.\\nHEAT.\\nQ. What is heat?\\nA. Heat is a form of energy. In any body its\\nmolecules are in a state of incessant oscillating\\nmotion, and the energy of these moving molecules\\nor particles of the body is the heat of that body.*\\nQ. What is temperature, and how does it differ\\nfrom heat\\nA. Temperature is a measure, not of the heat\\nin a body, but of the tendency of that body to\\ngive up its heat to other bodies. Two bodies\\nmay be at the same temperature and yet possess\\nvery different quantities of heat. For example,\\na cubic inch of iron and a cubic foot of iron may\\nboth be put in the same oven, and after remaining\\nthere for a considerable time they would be at the\\nsame temperature as would be shown by a ther-\\nmometer. But the cubic foot of iron has 1728\\ntimes as many heat-units in it as the cubic inch, as\\ncould be proved by putting them in equal quanti-\\nties of water, and noting to what temperature the\\nwater is raised in each case. According to the\\nmolecular theory of the structure of matter a\\nhigher temperature means that the molecules of\\nFor the explanation of the molecular theory of matter,\\nsee Roper s Engineers Handy-Book, page 611.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0059.jp2"}, "60": {"fulltext": "38 roper s catechism for\\nthe body are moving more rapidly. They, there-\\nfore, will communicate motion to surrounding\\nbodies the more readil}^, and this is the reason\\nthat bodies at high temperatures give up heat to\\nthose at the lower temperatures. A lower tem-\\nperature means that the velocity of the molecules\\nis less, and as the temjoerature gets lower and\\nlower their velocity would become smaller and\\nsmaller until a temperature is reached at which\\ntheir velocity is zero, that is, they are at rest.\\nThis temperature is known as the absolute zero of\\ntemperatures.\\nQ. How is temperature measured\\nA. By means of a thermometer.\\nQ. How is a thermometer usually made\\nA. A thermometer consists usually of a small\\nhollow glass tube with a bulb at its lower end.\\nThe air having been exhausted from the tube it is\\npartially filled with mercury and sealed. The\\ntube is placed in melting ice and the position of\\nthe top of the mercury column marked on the\\nglass. The same thing is done with the tube\\nplaced in boiling water. The distance between\\nthese two marks is divided into a certain number\\nof equal parts, according to which scale is used.\\nQ. What are the three thermometer scales in\\ncommon use\\nA. The Fahrenheit, Centigrade, and Reaumur.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0060.jp2"}, "61": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n39\\nCOMPARISON OF FAHRENHEIT, CENTIGRADE, AND\\nREAUMUR SCALES.\\nCENT.\\nDrill {\u00e2\u0080\u00a2r./Y- t^,^i ti+ 4 AA _^.^\\nFAHR.\\n?1?\\nREAU.\\nxsoiiing-point XvO\\nqQ Jt oiiing-point\\nof water.\\n200\\nof water.\\n90\\n190\\n180\\n70\\n80\\n170-\\n60\\n70\\n160\\n150\\n140\\n60\\n50\\n150\\nso-\\n180\\n40\\nlo\\n110\\n-100\\nzo\\n50\\n90\\n80\\n20\\n20\\n70\\n60\\nf A\\n10\\nlu\\n40\\nFreezing-point.\\nOX,\\nQ Freezing-point.\\n-10\\nto\\n10\\n10\\n\u00e2\u0080\u009410\\n-20\\n20\\n-30\u00e2\u0080\u0094\\n20\\nTVTpjTPnTTT fTPPr^fia M\u00c2\u00a3^\\nATiOJL^Ul J iiCC/iC ^\u00e2\u0080\u00a2\u00e2\u0080\u00a2li", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0061.jp2"}, "62": {"fulltext": "40 roper s catechism for\\nQ. Where is the Fahrenheit scale used\\nA. The Fahrenheit scale is used in England,\\nCanada, and in the United States.\\nQ. What is the difference between Fahrenheit s,\\nCentigrade, and Reaumur s scales\\nA. Fahrenheit s zero is 32\u00c2\u00b0 below freezing, Ijoil-\\ning-point of water, 212\u00c2\u00b0; Centigrade zero is at\\nfreezing, boiling-point, 100\u00c2\u00b0; Reaumur s zero is at\\nfreezing, boiling-point, 80\u00c2\u00b0. Hence, 180 Fahren-\\nheit degrees are equal to 100 Centigrade degrees\\nor 80 Reaumur degrees, or 9 Fahrenheit degrees\\nare equal to 5 Centigrade or 4 Reaumur degrees.\\nQ. What are fixed temperatures\\nA. One the melting-point of ice, and the other\\nthe boiling-point of pure water.\\nQ. Why do you call these fixed temperatures\\nA. Because it is impossible to raise the tempera-\\nture of ice above 32\u00c2\u00b0 Fahr., and no amount of\\nheat will raise boiling water above a temperature\\nof 212\u00c2\u00b0 Fahr., if contained in an open vessel.\\nQ. Does the thermometer indicate the amount\\nof heat in any body\\nA. No; only the changes in temperature.\\nQ. To how high temperatures can the mercurial\\nthermometer be used\\nA. To about 600\u00c2\u00b0 Fahr. At about 675\u00c2\u00b0 mer-\\ncury vaporizes.\\nQ. What method is adopted to determine tern-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0062.jp2"}, "63": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 41\\nperatures so high that no thermometer can give a\\nrehable result, as, for example, the temperature\\nin a blast furnace\\nA. We take a body, such as platinum, and\\nplace a mass of this metal in the blast furnace,\\nand when the mass has acquired the temperature of\\nthe furnace we transfer it to a vessel containing a\\nknown weight of water. We can then observe\\nthe rise of temperature by means of an ordinary\\nthermometer, and from this and the weight of the\\nplatinum and its specific heat (.0324) we can\\ncalculate the temperature.\\nQ. What is specific heat\\nA. Specific heat of a substance is an expression\\nfor the quantity of heat in any given weight of it\\nat certain temperatures. It is the number of\\nheat-units necessary to raise the temperature of\\n1 pound of the substance 1 degree.\\nQ. What is sensible heat\\nA. That which is sensible to the touch.\\nQ. What is latent heat\\nA. It is that which a body absorbs in changing\\nfrom a solid to a fluid state, called the latent heat\\nof liquefaction, or that which it absorbs in chang-\\ning from the liquid to the gaseous state, called the\\nlatent heat of vaporization.\\nQ. What is a unit of heat\\nA. The unit of heat is the amount of heat", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0063.jp2"}, "64": {"fulltext": "42 roper s catechism for\\nrequired to raise the temperature of 1 pound of\\nwater 1\u00c2\u00b0, or from 32\u00c2\u00b0 to 33\u00c2\u00b0 Fahr.\\nQ. What is the mechanical equivalent of heat\\nA. The energy necessary to raise 1 pound 778\\nfeet high that is, 778 foot-pounds of mechanical\\nenergy, if used to produce heat, will be just equal\\nto 1 heat-unit, being just able to raise the tem-\\nperature of 1 pound of water 1\u00c2\u00b0 Fahr.\\nQ. How is heat transferred from one body to\\nanother\\nA. In three ways, by radiation, by conductioHj]\\nand by convection.*\\nQ. What substances radiate heat most readily 1\\nA. Those which absorb it most readily and\\nreflect it the least.\\nQ. What color should the covering of steam\\npipes be painted\\nA. White, because white radiates less than\\ndark colors.\\nQ. If the pipe is bare, as, for instance, a copper\\npipe, should it be kept burnished or dull\\nA. Burnished.\\nQ. What are some of the best conductors of\\nheat?\\nA. Generally speaking, the metals, of which\\nsilver, copper, and gold are the best.\\n*For full explanation, see Eoper s Engineers Handy-\\nBook, page 94.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0064.jp2"}, "65": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 43\\nQ. Is there any similarity between heat conduc-\\ntivity and electrical conductivity\\nA. Generally speaking, good conductors for\\nheat are also good conductors electrically, although\\nthe metals do not stand in the same relative order\\nfor both cases.\\nQ. What are some of the best non-conductors\\nA. Magnesia, mineral wool, hair felt, cork, air\\n(not in motion).\\nQ. To what practical use are non-conductors of\\nheat put\\nA. To the covering of steam pipes.\\nQ. Apart from the waste of fuel clue to loss of\\nheat by radiation from steam pipes, is there any\\nother effect\\nA. Yes; there is a lowering of pressure and a\\ncondensation of steam into water, which, if exces-\\nsive, would cause trouble in an engine.\\nQ. How much heat does a pound of water\\nreceive in passing from a liquid at 212\u00c2\u00b0 Fahr. to\\navapor at 212\u00c2\u00b0?\\nA. It receives as much heat as would raise it\\n966\u00c2\u00b0 if the heat was sensible instead of latent.\\nQ. What is convection of heat\\nA. It is the transfer or diffusion of heat in a\\nfluid mass by means of its particles.\\nQ. Will water boil in a vacuum with less heat\\nthan under the pressure of the atmosphere", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0065.jp2"}, "66": {"fulltext": "44 roper s catechism for\\nA. Yes; in a vacuum of 1 pound absolute pres-\\nsure water boils at 98\u00c2\u00b0 to 100\u00c2\u00b0.\\nQ. Does water give out heat in freezing\\nA. Yes; water in freezing gives 142 heat-\\nunits.\\nQ. AVhat is a thermal unit?\\nA. It is the quantity of heat required to raise 1\\npound of water 1\u00c2\u00b0, the water being at its maxi-\\nmum density (=39\u00c2\u00b0 Fahr. It is also called a\\nBritish thermal unit, and is abbreviated B. T. U.\\nCOMBUSTION AND FUELS.\\nQ. What is combustion\\nA. Combustion is a chemical process which\\ntakes place rapidly, in which the one or more of\\nthe elements which make up the combustible body\\ncombines with the oxygen of the air. Briefly,\\ncombustion is a rapid oxidation accompanied by\\nflame or fire.\\nQ. What is smoke\\nA. Smoke is the result of imperfect combustion,\\nand its appearance is due to minute unburned\\nparticles in the air.\\nQ. What is necessar}^ to produce complete com-\\nbustion\\nA. We must have sufficient air, must mix the\\ncombustible thoroughly with the air, and must\\nmaintain the combustible and air mixed with it", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0066.jp2"}, "67": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 45\\nat a temperature above the igniting-point of the\\ncombustible.\\nQ. What is the meaning of the term fuel\\nA. Fuel is used to denote substances that may\\nbe burned with air rapidly enough to produce\\nsufficient heat for commercial purposes.\\nQ. What sort of substances does fuel consist of\\nA. Of vegetable substances or the products of\\ntheir decomposition.\\nQ. What are some of the principal fuels used\\nin the production of steam\\nA. Coal, coke, wood, petroleum, natural gas,\\npeat, and vegetable refuse of various kinds.\\nQ. What are the elementary substances which\\nare found in most fuels\\nA. Carbon, hydrogen, oxygen, nitrogen, and\\nsmall quantities of other elements.\\nQ. What is the chief constituent of coal\\nA. Carbon.\\nQ. How much carbon does good coal contain\\nA. Anthracite contains about 90 per cent.\\nQ. Are there any other elements in coal except\\ncarbon\\nA. Yes hydrogen, nitrogen, and sulphur in\\nsmall quantities.\\nQ. How much heat does 1 pound of pure car-\\nbon yield in burning\\nA. 14,000 units, approximately.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0067.jp2"}, "68": {"fulltext": "46\\nroper s catechism for\\nTABLE\\nOF TEMPEEATUEES EEQUIEED FOE THE IGNITION OF\\nDIFFEEENT COMBUSTIBLE SUBSTANCES.\\nSubstances.\\nTemperature\\nof Ignition.\\nRemarks.\\nPhosphorus,\\n140\u00c2\u00b0\\nMelts at 110\u00c2\u00b0.\\nBisulphide of carbon vapor,\\n300\u00c2\u00b0\\nMelts at 130\u00c2\u00b0.\\nFuhuinatiijg powder,\\n374\u00c2\u00b0\\nUsed in percussion caps.\\nFuhuiiiate of mercury,\\n392\u00c2\u00b0\\nAccording to Legue and\\nChampion.\\nEqual parts of chlorate of\\npotash and sulphur,\\n395\u00c2\u00b0\\nSulphur,\\n400\u00c2\u00b0\\nMelts, 280\u00c2\u00b0 boils, 850\u00c2\u00b0.\\nGun-cotton,\\n428\u00c2\u00b0\\nAccording to Legue and\\nChampion.\\nNitro-glycerine,\\n494\u00c2\u00b0\\nEifle-powder,\\n550\u00c2\u00b0\\nGunpowder, coarse,\\n563\u00c2\u00b0\\nPicrate of mercury, lead, or\\niron,\\n565\u00c2\u00b0\\n11 ti i\\nPicrate powder for torpedoes,\\n570\u00c2\u00b0\\nPicrate powder for muskets,\\n576\u00c2\u00b0\\n11\\nCharcoal, the most inflam-\\nmable willow used for gun-\\npowder,\\n580\u00c2\u00b0\\nAccording to Pelouse\\nand Fremy.\\nCharcoal made by distilling\\nwood at 500\u00c2\u00b0,\\n660\u00c2\u00b0\\ni\\nCharcoal made at 600\u00c2\u00b0,\\n700\u00c2\u00b0\\n11 It (i\\nPicrate powder for cannon,\\n716\u00c2\u00b0\\nVery dry wood, pine,\\n800\u00c2\u00b0\\nVery dry wood, oak,\\n900\u00c2\u00b0\\nCharcoal made at 800\u00c2\u00b0,\\n900\u00c2\u00b0\\nIt will be seen by the above table that the most combust-\\nible substances, generally considered very dangerous, will\\nonly ignite by heat alone at a high temperature, so that for\\ntheir prompt ignition it requires the actual contact of a\\nspark.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0068.jp2"}, "69": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 47\\nQ. How many heat-miits does 1 pound of good\\ncoal, containing 90 per cent, of carbon, produce\\nA. It produces in burning about 13,000 units.\\nQ. What is the mechanical equivalent of 13,000\\nunits\\nA. 10,114,000 foot-pounds, that is to say,\\n10,114,000 pounds raised 1 foot high.\\nQ. How much air does it require to burn 1\\npound of coal?\\nA. About 155 cubic feet.\\nQ. How much air does it require to burn 100\\npounds of coal\\nA. About 15,500 cubic feet of air.\\nQ. What is the difference between anthracite\\nand bituminous coal\\nA. Anthracite coal is nearly all carbon, having\\nonly about 10 per cent, of other matter, while\\nbituminous coal has from 15 to 50 per cent, of\\nother materials besides pure carbon.\\nQ. What is the relative fuel value of anthracite\\ncoal and wood\\nA. A pound of coal is equal to about 2\\\\ pounds\\nof wood.\\nQ. What is coke?\\nA. Coke is what is left of coal after the volatile\\ningredients have been driven off by distillation,\\nas in gasworks; or by partial combustion, as in\\ncoke-ovens.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0069.jp2"}, "70": {"fulltext": "48\\nROPER S CATECHISM FOR\\nTABLE\\nSHOWING THE TOTAL HEAT OF COMBUSTION\\nOF VARIOUS FUELS.\\nSort of Fuel.\\nEquiva-\\nlent in\\npure\\ncarbon.\\nEvapora-\\ntive power\\nin lbs. water\\nfrom 212\u00c2\u00b0\\nFahr.\\nTotal heat of\\ncombustion\\nin lbs. water\\nheated 1\u00c2\u00b0\\nFahr.\\nCharcoal,\\nCharred peat,\\nCoke\u00e2\u0080\u0094 good,\\nCoke mean,\\nCoke bad,\\nCoal:\\nAnthracite,\\nHard bituminous hardest,\\nHard bituminous softest,\\nCoking coal,\\nCannel coal,\\nLong-flaming splint coal,\\nLignite,\\nPeat:\\nPerfectly air-dry,\\nContaining 25 per cent, water.\\nWood\\nPerfectly air-dry,\\nContaining 25 per cent, water,\\n0.93\\n0.80\\n0.94\\n0.88\\n0.82\\n1.05\\n1.06\\n0.95\\n1.07\\n1.04\\n0.91\\n0.81\\n0.66\\n0.50\\n14.00\\n12.00\\n14 00\\n13.20\\n12.30\\n15.75\\n15.90\\n15.25\\n16.00\\n15.60\\n13.65\\n12.15\\n10.00\\n7.75\\n7.50\\n5.80\\n13,500\\n11,600\\n13,620\\n12,760\\n11,890\\n15,225\\n15,370\\n13,775\\n15,837\\n15,080\\n13,195\\n11,745\\n9,660\\n7,000\\n7,245\\n5,600\\nI\\nRemark. In a boiler of fair construction, a pound of\\ncoal will convert 9 pounds of water into steam. Each\\npound of this steam will represent an amount of energy, or\\ncapacity for performing work, equivalent to 746,666 foot-\\npounds, or for the whole 9 pounds, 6,720,000 foot-pounds.\\nIn other words, 1 pound of coal has done as much work in\\nevaporating 9 pounds of water into 9 pounds of steam as\\nwould lift 300 tons 10 feet high.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0070.jp2"}, "71": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 49\\nQ. Next to carbon, which of the constituents of\\ncoal is the greatest heat producer\\nA. Hydrogen.\\nQ. What is the number of heat-units produced\\nby burning a pound of hydrogen\\nA. 62,000 British thermal units.\\nQ. Why do some coals have a greater heat-pro-\\nducing value per pound than does pure carbon\\nA. Because they are so rich in hydrogen.\\nQ. What is meant by the term free hydrogen\\nin connection with coal\\nA. In all fuel containing carbon, hydrogen, and\\noxygen, the proportion of hydrogen may be equal\\nto or greater, but never less, than that required to\\nform .water with the oxj^gen. It is only the\\nhydrogen in excess of this which is available as a\\nsource of heat, and this is called free hydrogen.\\nThe hydrogen existing in combination with oxygen\\nin the state of water, so far from contributing to\\nthe actual amount of heat produced, must be\\nevaporated at the expense of the heat developed\\nby the combustion of the carbon.\\nQ. How does the heat-producing value of petro-\\nleum compare with that of coal\\nA. It is about greater, pound for pound.\\nQ. What are some of the advantages of using\\npetroleum as a fuel\\nA. It gives a steadier fire, is more easily hand-\\n4", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0071.jp2"}, "72": {"fulltext": "50 roper s catechism for\\nled, makes no ashes and little smoke, and does\\nnot take up so much space.\\nQ. What determines the advisability of using\\npetroleum rather than coal at a certain place\\nA. The most important point is the relative\\ncost of the two.\\nQ. How many pounds of water can be evapo-\\nrated by a pound of coal\\nA. This depends upon the kind of boiler used\\nand its condition, and also on the kind of coal,\\nthe amount varying from 6 to 12 pounds. Under\\nmost favorable conditions an evaporation of over\\n13 pounds of water per pound of combustible\\nhas been secured.\\nQ. What is the meaning of the term com-\\nbustible used in connection with coal for\\nexample, in the expression, pounds of water\\nevaporated per pound of combustible\\nA. The amount of combustible in a quantity\\nof coal is found by subtracting from the original\\nweight of the coal the weight of the water in the\\ncoal plus the weight of the ash produced when\\nit is burned.\\nAIR AND OTHER GASES.\\nQ. What are the three most important element-\\nary gases that is, the three most important\\nelements existing naturally in the gaseous state", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0072.jp2"}, "73": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 51\\nA. Oxygen, nitrogen, and hydrogen.\\nQ. What are some of the most important char-\\nacteristics of oxygen?\\nA. It is colorless, tasteless, and odorless. It\\nsupports combustion, which process is the chemi-\\ncal combination of the oxygen of the air with the\\nburning substance. It is necessary for the respi-\\nration of animals and clearing the blood of im-\\npurities. It combines readily with nearly all other\\nchemical elements.\\nQ. What is iron rust\\nA. A combination of iron with oxygen, known\\nas oxide of iron.\\nQ. What relation does rusting bear to com-\\nbustion\\nA. Rusting is slow oxidation; combustion is\\nrapid oxidation.\\nQ. What are some of the characteristics of\\nnitrogen\\nA. It is also colorless, tasteless, and odorless.\\nUnlike oxygen, it does not combine readily with\\nother elements; it will not burn nor support com-\\nbustion; mixed with oxygen it forms atmospheric\\nair, its function being to dilute the oxygen.\\nQ. Give some of the qualities of hydrogen.\\nA. It is colorless and tasteless and odorless\\nwhen pure. It is the lightest of known substances,\\nbeing only one-sixteenth as heavy as air. It", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0073.jp2"}, "74": {"fulltext": "52 roper s catechism for\\nunites most readily with oxygen, combining with\\nit to form water in the proportion of 1 part by\\nweight of hydrogen to 8 parts of oxygen. It\\nburns in air with a bluish flame.\\nQ. Of what does the atmosphere consist\\nA. Of oxygen and nitrogen mixed together (not\\nchemically combined), in the ratio of about 1\\npart by volume of oxygen to 4 parts of nitrogen.\\nQ. How far from the earth s surface is the\\natmosphere supposed to extend\\nA. At least 45 miles.\\nQ. Is its density uniform that is, is it the\\nsame at different heights\\nA. No; it is less dense as we go farther from\\nthe earth s surface.\\nQ. Does air have any weight\\nA. Yes; a cubic foot at the level of the sea\\nweighs about yfo- of a pound.\\nQ. What is atmospheric pressure, so-called\\nA. It is the pressure exerted on all bodies by\\nthe air, owing to its weight. Since all gases trans-\\nmit a pressure equally in all directions, and since\\nair has weight, it follows that any square inch of\\nsurface has a pressure exerted on it equal to the\\nweight of a column of air 1 square inch in cross-\\nsection and of 45 miles or more in length.\\nQ. How much is this weight, or, in other words,\\nhow much is the atmospheric pressure?", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0074.jp2"}, "75": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n53\\nTABLE\\nSHOWING APPROXIMATE INCREASE IN BULK OF\\nDUE TO INCREASE OF TEMPERATURE, AT\\nATMOSPHERIC PRESSURE.\\nFahrenheit.\\nTemp. 32 (Freezing-point)\\n38\\n34\\n35\\nBulk Fah\\n1000 Tei\\n1002\\n1004\\n1007\\n1009\\n1012\\n1015\\n1018\\n1021\\n1023\\n1025\\n1027\\n1030\\n1032\\n1034\\n1036\\n1038\\n1040\\n1043\\n1045\\n1047\\n1050\\n1052\\n1055\\n1057\\n1059\\n1062\\n1064\\n1066\\n1069\\n1071\\n1073\\n1075\\n1077\\n1080\\n1082\\n1084\\n1087\\n1089\\n1091\\n1093\\n1095\\n1097\\nrenheit.\\nup 75\\nBulk\\n1099\\n76 (Summer heat)\\n77\\n78\\n1101\\n1104\\n1106\\n36\\n37\\n79\\n80\\n1108\\n1110\\n38\\n81\\n1112\\n39\\n82\\n1114\\n40\\n83\\n1116\\n41\\n84\\n1118\\n42\\n85\\n1121\\n43\\n86\\n1123\\n44\\n87\\nll ?5\\n45\\n88\\n1128\\n46\\n89\\n1130\\n47\\n90\\n1132\\n48\\n91\\n1134\\n49\\n92\\n93\\n1136\\n50\\n1138\\n51\\n94\\n1140\\n52\\n53\\n54\\n95\\n96 (Blood heat)\\n97\\n98\\n1142\\n1144\\n1146\\n55\\n1148\\n56 (Temperate)\\n99\\n1150\\n100\\n1152\\n58\\n110\\n1173\\n59\\n120\\n1194\\n60\\n130\\n1215\\n61\\n140\\n1235\\n62\\n63\\n64\\n65\\n66\\n150.\\n160.\\n170 (Spirits\\n180\\n190\\nboil 176)\\nr55\\n1275\\n1295\\n1315\\n1334\\n67\\n200\\n1364\\n68\\n210\\n1372\\n69\\n70\\n212 (Water\\n302\\nboils)\\n1375\\n1558\\n71\\n392\\n1739\\n72\\n73\\n74\\n482\\n572\\n680\\n1919\\n2098\\n2312", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0075.jp2"}, "76": {"fulltext": "54 roper s catechism for\\nA. At sea-level and at 32\u00c2\u00b0 Fahr. it is about 14.7\\npounds per square inch, or, in round numbers,\\n15 pounds.\\nQ. What would you understand b}^ a pressure\\nof three atmospheres\\nA. A pressure of 45 pounds per square inch.\\nQ. What instrument is used to measure atmos-\\npheric pressure\\nA. The barometer.\\nQ. How is it made\\nA. By filling a glass tube about 3 feet long with\\nmercury and then inverting the tube, letting its\\nopen end rest in a vessel containing mercury.\\nThe height of the top of the mercury column in\\nthe tube is read by a graduated scale.\\nQ. Why does the mercury not run entirely out\\nof the tube into the vessel?\\nA. The mercury column is acted upon by two\\nforces; its weight tends to make it run out, but the\\natmosphere pressing on the surface of the mercury\\nin the vessel resists this action. The mercury\\ncolumn in the tube, therefore, falls only to the\\npoint where the pressure per square inch due to\\nthe weight of the column is just equal to the\\npressure per square inch exerted by the atmos-\\nphere.\\nQ. Will the reading of the barometer on a\\nmountain be higher or lower than at sea-level\\nI", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0076.jp2"}, "77": {"fulltext": "STEAM ENGINEEES AND ELECTRICIANS. 55\\nA. Lower; for the atmospheric pressure being\\nless, it cannot balance so long a column of mer-\\ncury.\\nQ. Why does the mercury column of the\\nbarometer at a certain place stand at different\\nheights at different times\\nA. Owing to the presence of more or less water,\\nvapor in the atmosphere which changes the weight\\nper cubic foot of air, and consequently alters the\\natmospheric pressure.\\nQ. How can the height of a place above sea-\\nlevel be measured by the barometer\\nA. By reading the barometer at the given place\\nand comparing this reading with that taken at\\nsome known altitude. Roughly, each inch of\\nlength of the barometer column corresponds to a\\ndifference in level of 1000 feet.\\nQ. Can heights also be measured by the ther-\\nmometer\\nA. Yes; by observing at what temperature\\nwater boils. At sea-level it boils at 212\u00c2\u00b0 Fahr.\\nRoughly, for every 500 feet rise above sea-level\\nthe temperature of the boiling-point is 1 degree\\nless.*\\nQ. What is the effect of heat on air\\nA. To expand it.\\n*For more accurate calculations of heights, see Roper s\\nEngineers Handy-Book, pages 121-134.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0077.jp2"}, "78": {"fulltext": "66 roper s catechism for\\nQ. What is the method of calculatmg this ex-\\npansion\\nA. Under constant pressure, for each degree\\nFahr. rise in temperature the volume of air ii\\nincreased by ^2 i^^ volume at 32\u00c2\u00b0 Fahr.\\nWATER.\\nQ. Of what is water composed\\nA. Of the elementary gases, oxygen and hydro-\\ngen, in the proportion by weight of 89 parts of\\noxygen to 11 parts of hydrogen. By volume the\\nratio is 1 part of oxygen to 2 parts of hydrogen.\\nQ. Is pure water found in nature\\nA. No; water has, in solution, oxygen, nitrogen,\\nand ammonia, taken up from the air, and traces\\nof salts of many minerals. It may also contain\\norganic impurities resulting from the decomposi-\\ntion of animal or vegetable matter.\\nQ. Water is taken as the standard for specific\\ngravity of liquids, but is its specific gravity\\nalways uniform\\nA. No; the weight of a cubic foot of water\\ndepends upon its purity. The presence of any\\nsalts in solution makes it heavier as in the case of\\nsea water.\\nQ. Does the temperature of water have any\\neffect upon its specific gravity\\nA. Yes; at about 39.2\u00c2\u00b0 Fahr. pure water is at\\nI", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0078.jp2"}, "79": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 57\\nits greatest density, that is, weighs most per cubic\\nfoot. Above this temperature it is less dense;\\nbelow this point it also becomes less dense until\\nat 32\u00c2\u00b0 it solidifies into ice.\\nQ. Under what conditions, then, is water taken\\nas the standard for specific gravities\\nA. With the understanding that the water is\\npure and is at a temperature of 39.2\u00c2\u00b0 Fahr.\\nQ. In what three physical states or forms does\\nwater exist\\nA. As ice, water, and steam.\\nQ. How do the weights of a cubic foot of ice,\\nwater, and steam compare\\nA. A cubic foot of ice weighs about 57 pounds;\\nof water, about 62 J- pounds; and of steam, at 5\\npounds gauge pressure, yl-g- pounds, and at 100\\npounds gauge pressure, y^^-g- pounds.\\nQ. What is necessary to change from one of\\nthese forms to the other?\\nA. Merely the application or withdrawal of heat.\\nQ. Is water a good conductor of heat\\nA. No.\\nQ. Is it a good conductor of electricity\\nA. Not if reasonably pure. The addition of\\nsome soluble metallic salt, like sodium carbonate\\nor of sulphuric acid, makes it a good electrical\\nconductor.\\n!l Q. What are some of its other properties", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0079.jp2"}, "80": {"fulltext": "58 eoper s catechism for\\nA. It is tasteless, odorless, and colorless, and a\\nsolvent for most gases and a vast number of\\nliquids and solids.\\nQ. At what temperature does water boil\\nA. This depends upon its purity and upon the\\natmospheric pressure. Reasonably pure water at\\nthe sea-level boils at 212\u00c2\u00b0 Fahr.\\nQ. On a mountain 3000 feet above sea-level, at\\nabout what temperature would you expect water\\nto boil?\\nA. At about 206\u00c2\u00b0 Fahr., as for every 500 feet\\nabove sea-level the boiling-point drops approxi-\\nmately 1 degree.\\nQ. How does the boiling-point of salt water\\ncompare with that of fresh water\\nA. It is higher.\\nQ. Which will hold the greater quantity of a\\nsubstance in solution, hot water or cold water?\\nA. This depends on the nature of the substance.\\nSalts of lime are less soluble in hot water and,\\ntherefore, if they exist in a natural water will be\\ndeposited when the water is heated to a high\\ntemperature.\\nQ. How does the specific heat of water com--\\npare with that of other substances flj\\nA. It is greater than that of nearly all other^\\nand it is for this reason that it is chosen as tlie\\nstandard for specific heats.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0080.jp2"}, "81": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 59\\nQ. What is the specific heat of ice\\nA. About .5, or half that of water.\\nQ. How many units of heat are necessary for\\nmelting 1 pound of ice\\nA. About 142.\\nQ. How can water be decomposed into its con-\\nstituents oxygen and hydrogen\\nA. By passing an electric current through it.*\\nQ. Can we recombine these two gases to form\\nwater\\nA. Yes; by burning the hydrogen in a jet in a\\nvessel containing the oxygen.\\nQ. What is the specific gravity or density of a\\nbody?\\nA. Its weight per unit volume; and since the\\nunit volume used by physicists is the cubic centi-\\nmeter the specific gravity or densitj^ is the weight\\n(in grams) per cubic centimeter.\\nQ. What would be the specific gravity of pure\\nwater\\nA. 1, because the weight of a cubic centimeter\\nof pure water is 1 gram.\\nQ. What is taken as the standard of specific\\ngravities\\nA. Water, because its specific gravity is 1.\\nQ. How could you obtain the specific gravity\\nof any liquid\\n*See Roper s Engineers Handy-Book. page 134.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0081.jp2"}, "82": {"fulltext": "60 eoper s catechism for\\nA. By weighing equal bulks of the. liquid and\\nof water and dividing the weight of the liquid by\\ntlie weight of the water.\\nQ. How could you obtain the specific gravity\\nof a solid heavier than water\\nA. Weigh it in air; place it in a jar even full\\nof water and catch the overflow of water and\\nweigh it. Divide the weight of the body in air\\nby the weight of the water it displaces; the quo-\\ntient will be the specific gravity.\\nQ. When a body whose specific gravity is\\ngreater than 1, that is, greater than that of water,\\nis placed in water, what occurs\\nA. The body sinks.\\nQ. How much water does it displace\\nA. A volume in cubic feet or inches equal to\\nthe volume of the sinking body.\\nQ. What happens if the specific gravity of the\\nbod}^ is less than 1\\nA. The body floats, sinking only to a certain\\ndepth in the water.\\nQ. How much water does it disi3lace\\nA. Such an amount as will weigh the same as\\nthe floating body.\\nQ. What is meant by the term head ajoplied\\nto water?\\nA. It means a difference in level for example,\\nwith a filled tank at the top of a house, the upper", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0082.jp2"}, "83": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 61\\nlevel of the water in the tank being, say, 50 feet\\nabove the level of a spigot in the basement, there\\nwould be exerted at the spigot a pressure equal\\nin pounds to the weight of a column of water 50\\nfeet high we should say, then, that there was at\\nthe spigot a head of 50 feet.\\nQ. With a head of 100 feet, how would the\\n.pressure compare with the preceding case\\nA. It would be double, the pressure being\\nstrictly proportional to the head.\\nQ. What pressure corresponds to a head of 1\\nfoot?\\nA. Remembering that a cubic foot, or 1728 cubic\\ninches, of water w^eighs 62.5 pounds, it is easily\\ncalculated. A column of water 12 inches high by\\n1 inch square would contain 12 cubic inches and\\nwould weigh yyfg- or y^ of 62.5 pounds, or .43\\npound. Therefore, the pressure due to a head of\\n1 foot would be .43 pound per square inch.\\nQ. When water flows from an orifice in the\\nbottom of a tank under a head, how can its velocity\\nbe calculated\\nA. Were it not for friction of, and eddy currents\\nin, the water at the orifice, each particle of water\\nwould emerge at a velocity the same as it would\\nhave if it were allowed to drop through a height\\nequal to the head (the head in this case is the\\ndifference in level between the upper surface of", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0083.jp2"}, "84": {"fulltext": "62 roper s catechism for\\nthe water and the orifice). The formula is v\\nV 64. 4 h, or velocity in feet per second equals the\\nsquare root of 64.4 X the head in feet. Owing\\nto eddy currents set up at the orifice, the actual\\nvelocity will be slightly less than the value of v\\nobtained from the formula.\\nQ. Suppose that you desired to know the num-\\nber of cubic feet of water flowing from an orifice,\\nhow would you obtain it?\\nA. First obtain, as above, the velocity in feet per\\nsecond, multiply this by the area of the orifice in\\nsquare feet, and multiply the product by The\\nresult will be the quantity in cubic feet per second.\\nQ. Why do you multiply by\\nA. Because the jet of water issuing from the\\norifice has an area less than that of the orifice,\\nit being from six- to eight-tenths as large, accord-\\ning to the form of the orifice.\\nQ. When water is led from a tank through a\\nlong pipe and then allowed to flow from the mouth\\nof the pipe into the air, will the velocity be the\\nsame as calculated above\\nA. No; it will be less, owing to the friction of\\nthe water against the walls of the pipe, which\\ncauses a loss of pressure or loss of head.\\nQ. What does the loss of pressure depend on\\nA. The length*of pipe, its diameter, and the\\nsmoothness of the interior.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0084.jp2"}, "85": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 63\\nQ. Is the loss of pressure greater as the pipe is\\nlonger\\nA. Yes; the loss is strictly proportional to the\\nlength of pipe, the loss for a length of 200 feet\\nbeing double that for 100 feet.\\nQ. What effect does increasing the size of pipe\\nhave on the loss of pressure\\nA. The larger the pipe the less the lost pressure.\\nThe loss of pressure is proportional to the length\\nof the pipe and the square of the velocity, and\\ninversely proportional to the diameter of the\\npipe.^\\nQ. Having these tables, how would you calcu-\\nlate the velocity at which water escapes from a\\npipe 500 feet long, the height of the water in the\\ntank being 50 feet above the mouth of the\\npipe\\nA. Calculate first the flow, assuming no loss\\nowing to friction; then, with this flow, from the\\ntables calculate the loss of head subtracting\\nthis head from 50 feet gives the effective head.\\nFinally, using the effective head, calculate the\\nvelocity of flow.\\nFor tables of the loss of pressure, see Eoper s Engi-\\nneers Handy-Book, page 42.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0085.jp2"}, "86": {"fulltext": "64 roper s catechism for\\nSTEAM.\\nQ. What is steam\\nA. Steam is the gaseous form of water produced\\nby the application of heat sufficient to raise the\\ntemperature of the water to 212\u00c2\u00b0 Fahr.\\nQ. What are the most prominent properties*\\npossessed by steam\\nA. First, its high expansive force; second, its\\nproperty of condensation; third, its concealed or\\nlatent heat.\\nQ. Is steam in itself invisible\\nA. Yes; and it only becomes visible by loss of\\ntemperature, as when a jet is discharged into the\\nopen air, and is then seen in the form of vapor.\\nQ. If a jet of steam flowing into the air gave a\\ncloudy appearance close to the opening, what\\nwould you conclude?\\nA. That the steam was very moist, that is, that\\nit was carrying along with it a large quantity of\\nwater in finely divided particles.\\nQ. How is the condensation of steam effected\\nA. By the lowering of its temperature.\\nQ. What is the difference in volume between\\nwater and steam at a temperature of 212\u00c2\u00b0\\nFahr.\\nA. 1700; that is to say, any given quantity of\\nwater converted into steam at the pressure of the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0086.jp2"}, "87": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 65\\natmosphere or 212\u00c2\u00b0 Fahr. will present a volume\\n1700 times greater than its original bulk.\\nQ. What is dry- saturated steam\\nA. The vapor formed from water at a certain\\ntemperature and pressure and either remaining in\\ncontact with the water, or, if withdrawn from con-\\ntact with the water, not subjected to any further\\nheating.\\nQ. What is superheated steam\\nA. Dry-saturated steam not in contact with\\nwater and raised to a higher temperature than\\nthat at which it was formed.\\nQ. How does ordinary steam differ from dry-\\nsaturated steam\\nA. It has minute particles of water suspended\\nin it.\\nQ. Can steam be raised to a very high tempera-\\nture?\\nA, Yes; steam can be heated to nearly a red\\nheat, but not while it is held in contact with\\nwater.\\nQ. Is steam at ordinary pressure hot enough to\\nignite wood\\nA. Not without the intervention of some other\\nsubstance, such as linseed oil, greasy rags, or iron\\nturnings.\\nQ. What do you understand by the term steam\\npressure\\n5", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0087.jp2"}, "88": {"fulltext": "66 roper s catechism for\\nA. The elastic force which steam exerts in every\\ndirection.\\nQ. What is the sensible heat of steam?\\nA. The heat which goes to raise its temperature,\\nas, for example, if water at 32\u00c2\u00b0 Fahr. has heat\\napplied to it, its temperature will rise up to, but\\nnot above, 212\u00c2\u00b0 Fahr. The number of heat-units\\nrequired to raise 1 pound of water from 32\u00c2\u00b0 Fahr.\\nto any temperature is called the sensible heat cor-\\nresponding to that temperature.\\nQ. A\u00c2\u00a5hat other name is given to the sensible\\nheat\\nA. The heat of the liquid or the heat in water.\\nQ. What is latent heat?\\nA. Heat which is not sensible to the touch nor\\nindicated by the thermometer.\\nQ. Is there more than one latent heat\\nA. Yes; the latent heat of liquefaction, as, fo]\\nexample, the heat absorbed when ice melts into\\nwater; and the late^it heat of vaporization, or the\\nheat absorbed when water is changed to steam.\\nQ. How may the existence of latent heat be\\nshown\\ny1. If a thermometer be placed in a vessel con-\\ntaining water which is being heated, the reading\\nof the thermometer increases as heat is applied\\ntill it reaches 212\u00c2\u00b0, at which point the water\\nboils. After this, although heat is continually\\nI", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0088.jp2"}, "89": {"fulltext": "STEAM ENGINEERS AND ELECTEICIANS. 67\\napplied, the thermometer goes no higher. This\\namount of heat which goes to change the physical\\nstate of water without changing its temperature\\nis called latent heat.\\nQ. What is the latent heat of vaporization of\\nwater\\nA. The amount of heat needed to change a\\npound of water into steam.\\nQ. What is the sum of the latent heat of vapor-\\nization and the heat of the liquid, at any tem-\\nperature, called?\\nA. The total heat corresponding to that tem-\\nperature.\\nQ. Is the total heat the same for all pressures\\nA. At atmospheric pressure it is 1180, at 100\\npounds gauge pressure it is 1217, and at 135\\npounds it is 1223.\\nQ. Does the elasticity of steam increase with\\nan increase of temperature\\nA. Yes, but not in the same ratio; because if\\nsteam is generated from water at a temperature\\nwhich gives it the pressure of the atmosphere, an\\nadditional temperature of 38\u00c2\u00b0 will give it a pres-\\nsure of 2 atmospheres, and a still further addition\\nof 42\u00c2\u00b0 will give it a pressure of 4 atmospheres.\\nQ. Do you know any simple formula connecting\\nthe pressure and temperature of saturated steam\\nA. Experiments have been made from which", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0089.jp2"}, "90": {"fulltext": "b 5 roper s catechism for\\ntables have been constructed, known as tables of\\nthe properties of steam, which give the relation\\nbetween pressure and temperature.*\\nQ. What is indicated by the ordinary steam\\ngauge\\nA. The pressure of the steam above the atmos-\\nphere, that is, the number of pounds by which\\nit exceeds atmospheric pressure.\\nQ. How would you get the total pressure of the\\nsteam, that is, the number of pounds pressure-\\nabove zero\\nA. By reading the barometer, calculating the\\nnumber of pounds of atmospheric pressure corre-\\nsponding to the barometer reading, and adding\\nthis to the reading of the steam gauge.\\nQ. When a pound of steam is condensed to\\nwater, how much heat is given up to the surround-\\ning air?\\nA. An amount of heat equal to the latent heat\\nof steam at the temperature at which it is.\\nQ. If afterward the water cools to a still lower\\ntemperature, how much heat is given off?\\nA. The amount can be found by subtracting the\\nheat of the liquid at the lower temperature from\\nthat corresponding to the upper temperature; the\\ndifference will be the number of units of heat\\ngiven out per pound of cooling water.\\n*See Roper s Land and Marine Engines.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0090.jp2"}, "91": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 69\\nTHE STEAM BOILER*\\nDesigning steam boilers is not within the\\nprovince of the stationary engineer. It is his\\nduty not to build boilers, but to operate them to\\nthe best advantage. Frequently, however, he is\\ncalled upon to assist in the selection of the type of\\nboiler for a given purpose, and in this he should\\nremember that the three most important objects\\nto be attained are safety, durability, and economy.\\nTo secure safety it is necessary that the boiler\\nshould be made of good material, with good work-\\nmanship.\\nTo secure durability the boiler ought to be con-\\nstructed so as to give the greatest facilities and\\neasiest access for cleaning, repairing, and renewal\\nof any of its parts. The boiler should also be so\\ndesigned as to avoid unequal strains by expansion\\nand contraction, as far as possible.\\nIn attempting to secure economy in the genera-\\ntion of steam, it is necessary, first^ to secure perfect\\ncombustion of the fuel, so as to produce the great-\\nest amount of heat; secondly^ to apply the heat in\\nthe very best manner to the boiler, so as to heat\\nthe water in the most rapid manner possible\\nthirdly, to be very careful to prevent the heat from\\nescaping by radiation or with the products of\\ncombustion. If these three conditions be com-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0091.jp2"}, "92": {"fulltext": "70 roper s catechism for\\nplied with, our arrangements will be of the most\\neconomical character. The evaporative efficiency\\nof any boiler and furnace is to be measured by the\\namount of water evaporated by any given weight\\nof fuel in a given time. Mere waste of fuel, how-\\never, is not the only defect attendant upon an\\ninferior construction of boiler and furnace. Where\\nthese are not of the best kind, they must be of\\nlarger size in order to do the required amount of\\nwork; the grate surface must be larger, and more\\nair must be needlessly raised to a higher tempera-\\nture, thus carrying off a large amount of heat in\\nthe waste products of combustion; all of which\\ninvolves increased outlay of capital and larger\\nrunning expenses.\\nMany of the defects of modern boilers might\\nbe attributed to the fact that some of the in-\\nventors or designers seem to be partly, if not\\ntotally, ignorant of the first principles of mechan-\\nical science, and to competition between boiler\\nmakers themselves, in their efforts to undersell\\neach other; consequently they have to deceive\\npurchasers and steam users by magnifying small\\nl)oilers into large ones. Therefore, when the boiler\\ncomes to be tested, its evaporative powers are\\nfound to be lacking, the fuel has to be burned\\nunder a sharp draught, and instead of the best\\nresults the worst are obtained.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0092.jp2"}, "93": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 71\\nIn regard to the metal of the boiler itself, it is a\\nwell-known fact that the thicker the iron is, and\\nthe poorer its conducting qualities, the greater will\\nbe the amount of heat that will be lost or wasted;\\nwhen, by using a superior quality of iron, one\\nwhose tensile strength and conducting powers are\\nboth very great, we lessen the resistance to the\\npassage of the heat from the furnace to the water\\nand greatly increase the economy of the boiler.\\nIt is well known to engineers that there is a wide\\ndifference in the physical properties of different\\ngrades of iron and steel used in boiler construction.\\nSome kinds of boiler plate have nearly double the\\ntensile strength of others, and, consequently, to\\nsecure the same strength the latter would have to\\nbe made twice as thick as the former. This would\\ninvolve the interposition of a more difficult path\\nbetween the fire and the water, reducing the\\nefficiency and producing a weaker boiler, because\\nthe thicker plate has been subjected to greater\\nstrains in the bending. Consequent^ the thinner\\nplate, is by far the more advantageous. On the\\nother hand, as the tensile strength of boiler plates\\nincreases, its ductility decreases, and, therefore,\\ngreat care must be taken in selecting boiler mate-\\nrials, to be sure that they possess not only tensile\\nstrength, but also ductility, otherwise the plates\\nwill be subjected to initial strains, and, further-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0093.jp2"}, "94": {"fulltext": "72 roper s catechism for\\nmore, the boiler will not be sufficiently flexible to\\nwithstand the varying strains to which it is con-\\nstantly subjected. For these reasons it has been\\nfouiid that the best material for boilers is one which\\nhas a moderate tensile strength, 50,000 to 60,000\\npounds per square inch, and which will elongate\\n20 to 25 per cent, before breaking and contract 50\\nper cent, in cross-section at the point where rup-\\nture takes place.\\nEvery attempt to lessen the first cost of a\\nboiler by diminishing the heating- and grate-\\nsurface is, to a certain extent, carrying out the\\nprinciple of penny wise and pound foolish.\\nAn engine extra large for the work to be done\\ncauses a loss of fuel, while a boiler moderately\\nlarger than necessary to do the work is productive\\nof economy in the use of fuel. A boiler taxed to\\nits utmost capacity will evaporate, say, from 5 to\\n6 pounds of water per pound of coal, while the\\nsame boiler might evaporate half the quantity of\\nwater at the rate of 8 to 10 pounds of water per\\npound of fuel. This is due partly to the fact that\\nwhen the boiler is forced the heating surface is not\\nsufficient to utilize all of the heat from the prod-\\nucts of combustion, and partly also to the excess\\nof air above that necessary for combustion which\\npasses through the grate and which is heated with-\\nout producing any useful effect.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0094.jp2"}, "95": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 73\\nFor instance, a locomotive boiler burning 10\\npounds of coal on each square foot of grate surface\\nin an hour, will evaporate, say, 8 pounds of water\\nfor each pound of coal. The same boiler, running\\nat a high speed, and burning 75 pounds of coal\\non each square foot of grate surface, will evaporate\\n7 pounds of water for each pound of coal burned.\\nHere is a vast difference in the total amount of\\nevaporation, each pound of coal produces less\\nsteam in the proportion of 9 to 7 pounds.\\nOn the other hand, increasing the size of boiler\\nfor a given evaporation must not be carried to\\nexcess, because beyond a certain limit there is no\\nadvantage to be derived and the increased first\\ncost then becomes a waste in the other direction.\\nThere is a certain fixed relation between grate\\nsurface, heating surface, and quantity of water\\nevaporated, in each type of boiler, which has been\\nfound in practice to be the most advantageous,\\nand any material departure from this in either\\ndirection will impair the cost of operation.*\\nA boiler may generate steam with great economy,\\nbut, owing to the steam being wasted by improper\\napplication to the engine, the result is unsatis-\\nfactory and the boiler unjustly blamed. On the\\nother hand, a boiler that carries out water with its\\nFor proportions of grate area, heating surface, etc. see\\npage 95 e^ seg-.; also, Eoper s Handy-Book, Chapter X.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0095.jp2"}, "96": {"fulltext": "74 roper s catechism for\\nsteam may show a large evaporation, but the\\nsteam being wet, is almost useless in the engine;\\nso that in judging the results of a steam-power\\nplant, great care must be taken to examine closely\\ninto all of the conditions, before condemning either\\nthe boiler or the engine.\\nIn selecting a type of boiler for a given pur-\\npose, there are many circumstances to be taken\\ninto account. Generally speaking, the most im-\\nportant considerations, as stated above, are safety,\\neconomy, and durability; of these, safety should\\nalwa^^s be first considered, because there are no\\nconditions under which human life and property\\nare not at stake. Consequently, if a boiler is\\nnot safe, it is not fit for use under any circum-\\nstances. The question of economy must be looked\\nat in a different way. Generally speaking, that\\nboiler is the most economical which evaporates the\\ngreatest amount of water with the least consump-\\ntion of coal, but there may be conditions under\\nwhich this is not the case; for example, in the coal-\\nregions, where fuel is very inexpensive, a highly\\nefficient boiler, which is of necessity more com-\\nplex than one which is less so, might cost more to\\noperate on account of the interest on the greater\\nfirst cost and the cost of attendance than a simple\\nfine or even a plain cylinder boiler; and it is a fact\\nthat the most efficient and therefore most expen-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0096.jp2"}, "97": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 75\\nsive boilers are not commonly nsecl where fuel is\\ncheap. Similar considerations might lead to the\\nselection of a less durable boiler. Suppose, for\\nexample, the case of a bridge to be built in some\\nout-of-the-way locality, the work requiring but a\\nshort time and the cost of transportation large\\ncompared to the value of the boiler. Under these\\ncircumstances it would probably not pay to use a\\nboiler of the highest grade, but preferably one\\nwhich was merely safe and cheap, did not require\\nmuch attention, cleaning, etc. and need not neces-\\nsarily be durable. Such conditions, however, are\\nvery uncommon and, generally speaking, the most\\nefficient and durable boiler is the safest and the\\nDIFFERENT TYPES\u00e2\u0080\u0094 ADVANTAGES AND\\nDISADVANTAGES.\\nQ. How would you classify steam boilers\\nA! Into cylindrical, flue, fire tubular, and water\\ntubular.\\nQ. What advantages does the plain cylinder\\nboiler possess over other types\\nA. It is simple, inexpensive, easy to clean and\\nrepair, and reasonably safe.\\nQ. What are its disadvantages\\nA. Its disadvantages are numerous and great.\\nFirst, on account of its relatively small heating", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0097.jp2"}, "98": {"fulltext": "ROPER S CATECHISM FOR", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0098.jp2"}, "99": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. il\\nsurface, it is very bulky, and, consequently, for a\\ngiven evaporative capacity, the space it occupies\\nlis much greater than in more modern types.\\nSecondly, on account of the high temperature at\\nIwhich the gases escape from the stack, it wastes\\nfuel, and for this reason it is the least economical\\ntype of boiler in existence. Thirdly^ it takes a\\nvery long time to raise steam. Fourthly, the\\nscale formed in the bottom, where the heat is\\nimost intense, makes a non-conducting stratum\\nwhich soon renders that portion of the heating\\nsurface useless and causes the iron to burn at that\\noint.\\nQ. Are plain cylinder boilers much used at the\\npresent time\\nA. No; they have disappeared almost entirely,\\nmainly on account of their inefficiency. They\\nire found occasionally in localities where the cost\\n3f fuel is very low.\\nQ. Name the principal varieties of flue boilers\\nmd briefly describe their characteristics.\\nA. The Cornish, Lancashire, and Galloway\\n3oilers are the principal varieties of flue boilers.\\n[n the Cornish type an internal cylindrical flue\\nextends the whole length of the boiler and the\\nurnace is usually contained in the flue. The\\nl^ancashire boiler has two internal flues with a\\nurnace in each, the two flues uniting into one", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0099.jp2"}, "100": {"fulltext": "78\\nroper s catechism for", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0100.jp2"}, "101": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. i\\\\)\\nbehind the bridge wall. The Galloway is similar\\nto the Lancashire, but has a number of conical\\ntubes, called Galloway tubes, inside and across the\\nflues, through which the water circulates. The\\nfurnaces are either within the flues or external.*\\nQ. What are the relative advantages and dis-\\nadvantages of the above-named boilers\\nA. The Cornish boiler has a greater heating\\nsurface than the plain cylindrical boiler, and it\\nhas the further advantage that that portion of the\\nshell on which the scale is deposited, is the coolest\\ninstead of the hottest point. It has the disad-\\nvantage that, for the same water capacity, it must\\nhave a greater diameter.\\nThe Lancashire boiler has the same advantages,\\nand additionally the combustion is more complete\\nthan in the Cornish type, because the furnaces\\nmay be fired alternately and the smoke which\\nwould issue from the stack, if there were but one\\nfurnace, is to a great extent consumed by coming\\nin contact with the products of .combustion from\\nthe other furnace. It also has the disadvantages,\\nin common with the Cornish boiler, that its diam\\neter is greater and, further, the liability of the\\ninternal flue to collapse, both of which disadvan-\\ntages it possesses to an even greater degree than\\nFor description of flue boilers, see Roper s Engineers\\nHandy-Book, pages 160-164.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0101.jp2"}, "102": {"fulltext": "80 roper s catechism for\\nthe Cornish boiler. The liability of the flue to\\ncollapse, however, is not very great when the\\nflues are properly stiffened or corrugated.\\nThe Galloway boiler, being virtually a modified\\nLancashire boiler, possesses all of its advantages;\\nand, additionally, by virtue of the conical tubes,\\nwhich are placed transversely in the flues, it has\\na greater heating surface and better circulation.\\nFurthermore, the flues are much less liable to\\ncollapse. All of this is accomplished by the\\nGalloway tubes. Of the three boilers mentioned\\nthe Galloway type is the safest and most econom-\\nical in the use of fuel.\\nQ. What methods are employed to stiffen the\\nflues of boilers and to provide for linear expan-\\nsion and contraction\\nA. This end was formerly accomplished by\\nmaking the flues in short lengths and connecting\\nthem by /\\\\-shaped rings, riveted on each section\\nof flue. The stiffening of the flue alone is also\\naccomplished by placing T-shaped rings within\\nthe flues, at intervals, and by the use of Galloway\\ntubes. This, however, does not take care of ex-\\npansion and contraction. The best way of ac-\\ncomplishing both ends is by corrugating the\\nflue, which has the further advantage of increas-\\ning the heating surface without taking up any\\nmore space in the boiler.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0102.jp2"}, "103": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 81\\nQ. What is meant by fire-tube or tubular boil-\\ners\\nA. Fire-tube or tubular boilers are those in\\nwhich the combustion gases pass, not only around\\nthe outside shell, but also through tubes which are\\nsurrounded by water.\\nQ. In what respect do they differ from flue\\nboilers\\nA. In no essential feature, except that instead\\nof one flue of large diameter there are a number\\nof small flues or tubes.\\nQ. What is the difference between internally\\nand externally fired tubular boilers\\nA. The internally fired type consists of an ex-\\nternal cylindrical shell containing a furnace ex-\\ntending from the front of the boiler to a point\\nabout midway in the length of the boiler. From\\nthis point, and extending to the rear end of the\\nboiler, there are a number of tubes which lead the\\ngases of combustion to the back, whence they pass\\nunder the outside shell to the front and into the\\nstack. In the externally fired type the tubes\\nextend the whole length of the boiler, and the\\nfurnace is outside and under the front end of the\\nboiler. The products of combustion pass along\\nthe bottom of the shell to the back of the boiler,\\nand then return through the tubes to the front\\nwhere they enter the stack connection. From the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0103.jp2"}, "104": {"fulltext": "82\\nROPER S CATECHISM FOR", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0104.jp2"}, "105": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 83\\ncourse which the gases take, this latter type is\\nfrequently designated as Return Tubular.\\nQ. What ad\\\\^antages does a tubular boiler pos-\\nsess over the cylinder and flue boilers\\nA. The tubular takes up less room, generates\\nsteam more rapidly, and requires less fuel; more-\\nover, tubes are less dangerous than flues, on ac-\\ncount of their small diameter and great strength.\\nQ. Why are tubular boilers more economical\\nthan plain cylinder and flue boilers\\nA. Because their heating surface is much greater,\\nand consequently the greater portion of the heat\\ncontained in the combustion gases is imparted to\\nthe water.\\nQ. What are their disadvantages as compared\\nto the above-mentioned types Are they impor-\\ntant?\\nA. The disadvantages are that the first cost is\\ngreater, and that they are more difficult to clean\\nand repair, because they are less accessible. These\\ndisadvantages are unimportant compared to the\\ngreat gain in economy, f\\nQ. What may be said about the tubular boiler\\nin regard to safety\\nA. The tubular boiler is just as safe as the\\ncylindrical boiler, and more so than the flue boiler,\\n*See Roper s Engineers Handy-Book, pages 165-168.\\nt For comparison with water-tube boilers, see next page.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0105.jp2"}, "106": {"fulltext": "84 roper s catechism for\\nbecause the parts subjected to internal pressure\\nhave the same strength, while those subjected to\\nexternal pressure, being smaller in diameter, are\\nmuch stronger.\\nQ. What is a water- tube boiler?\\nA. It is one in which the water circulates\\nthrough a series of tubes, which are surrounded\\nby the combustion gases.\\nQ. What is the position of the tubes in this\\nclass of boilers\\nA. Different makers place the tubes in different\\npositions. In the most common type, such as\\nthe Babcock and Wilcox, Heine, Gill and Root, the\\ntubes are inclined; in others, such as the Cahall,\\nthey are vertical, and occasionally the}^ may even\\nbe found curved spirally.*\\nQ. What are the principal advantages of the\\nwater-tube boiler as compared with other types\\nA. Its advantages are that it is safer, more eco-\\nnomical, steams more rapidly, is easily repaired,\\nmore durable; its form may be adapted to almost\\nany existing conditions, and it may be easily taken\\napart and transported. Its only disadvantages\\nare that it is heavy and expensive.\\nQ. Why is this type of boiler the most econom-\\nical in the use of fuel?\\nDescriptions of the different types in a comdeused form\\ncan be found in Babcock and Wilcox s Steam.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0106.jp2"}, "107": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 85\\nA. Because it has an enormous amount of heat-\\ning surface, and because the metal which con-\\nstitutes the heating surface is comparatively light;\\nbecause the combustion is very thorough, and com-\\nparatively little heat is contained in the escaping\\ngases.\\nQ. Why is it the safest?\\nA. Because for a given rating the parts sub-\\njected to strain are of smaller diameter than in\\nany other type, and, moreover, none are subjected\\nto external pressure. Further, because it is so\\nflexible that the whole structure accommodates\\nitself to changes in temperature without causing\\nundue strains.\\nQ. AVhat would probably be the difference in\\nan explosion of a water tube and a fire tube\\nboiler\\nA. Explosions occurring in fire -tube boilers\\nusually wreck the entire boiler, and in some cases\\nwhole batteries have been known to explode as\\nthe result of a single defect in one of the shells,\\nentailing great loss of life and property. In the\\nwater tube type, while more or less serious\\nexplosions have occurred, it is very rare for any-\\nthing more than a single tube or header to give\\nway; this may be easily repaired and does not\\ngenerally entail much loss.\\nQ. Why is it durable", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0107.jp2"}, "108": {"fulltext": "ROPER S CATECHISM FOR", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0108.jp2"}, "109": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 87\\nA. Because it is easily accessible, and because,\\nas already stated, it adapts itself to the varying\\nexpansion and contraction without producing\\nundue strains; further, the circulation is good and\\nconsequently the temperature of the different\\nparts is fairly uniform.\\nQ. To what class do locomotive and marine\\nboilers belong?\\nA. They may be said to belong to the tubular\\ntype, but they have certain characteristics not\\nembodied in the ordinary tubular boiler, Avhich\\nreally place them in separate classes by them-\\nselves.\\nQ. Give a brief description of a modern marine\\nboiler.\\nA. It usually consists of a short, circular shell\\nof large diameter with an internal corrugated fur-\\nnace. At the back of the furnace is a- chamber\\ninto which the gases pass from the furnace. This\\nis called the back up-take. A similar chamber in\\nthe front, called the front up-take, connects with\\nthe stack. The tubes are placed above and around\\nthe furnace, and extend from the front to the back\\nup-take.\\nQ. What, then, is the essential difference be-\\ntween a marine boiler and an internally fired\\ntubular boiler?\\nA. The principal difference is that while in the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0109.jp2"}, "110": {"fulltext": "05 ROPER S CATECHISM FOR\\nordinary internally fired tubular boiler the gases\\npass from the furnaces through tubes to the back\\nand then along the outside to the front; in the\\nmarine boiler the gases do not pass around the\\noutside at all, but go from the furnace directly\\ninto the back up-take, thence through the tubes\\nto the front up-take and into the stack.\\nQ. What conditions have brought about this\\ndesign of boiler for marine purposes\\nA. For marine purposes a boiler must be short,\\nas otherwise it could not be set and operated in\\nthe available space; and it must be self-contained,\\nbecause brick setting, on account of its great\\nweight and the motion of the ship, would be out\\nof the question. It must also make steam\\nrapidly.\\nQ. What pressure may be carried in modern\\nmarine boilers\\nA. Upward of 200 pounds per square inch.\\nQ. How many furnaces are generally used\\nA. Boilers less than 9 feet in diameter usually\\nhave only one; those from 9 to 13 feet, two; over\\n13 feet, three; and the largest, sometimes exceed-\\ning 15 feet in diameter, have four furnaces.\\nQ. What is meant by a double-ended boiler?\\nA. When the boilers are fired from the sides of\\nthe ship they are frequentl}^ placed back to back\\nor are made double-ended that is, they have fur-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0110.jp2"}, "111": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 89\\nnaces at both ends, with a common or separate\\nback up-takes. The latter arrangement is prefer-\\nable, because if anything should happen to a\\ntube in one end, this may be repaired without\\naffecting the other half of the boiler.\\nQ. What are the advantages and disadvantages\\nof marine-type boilers\\nA. They do not occupy much floor space,\\nrequire no brick setting, have a large steaming\\ncapacity for a given size and weight, but they are\\nnot as economical in the use of fuel or as safe as\\nthe best types of land boilers.\\nQ. Are marine-type boilers ever used for sta-\\ntionary purposes\\nA. The marine type of boiler is occasionally\\nfound on land. It is well adapted for use where\\nthe vibration is so great as to render brick setting\\nimpracticable, and where floor space is limited.\\nQ. Give a brief description of a locomotive\\nboiler.\\nA. The locomotive boiler consists of a rectang-\\nular furnace or fire-box, often made of copper,\\nwhich contains the grate bars. The fire-box is\\ninclosed in the boiler shell, which is also rec-\\ntangular where it contains the fire-box, but the\\nremainder of the shell consists of a long cylinder\\nof comparatively small diameter, which contains\\na large number of tubes. The products of com-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0111.jp2"}, "112": {"fulltext": "90 roper s catecpiism for\\nbustion first strike a fire-brick arch which deflects\\nthem into the tubes, through which they pass\\ninto the funnel or stack placed on the smoke-box\\nat the front end. Locomotives generally use\\nforced draught, which is obtained by allowing the\\nsteam from the engine cylinders to exhaust through\\nthe funnel.\\nQ. What conditions have led to the design now\\ngenerally used for locomotive boilers\\nA. A boiler suitable for use on locomotives\\nmust be light and of small diameter light,\\nbecause it is carried along at a high rate of speed,\\nand of small diameter on account of the limited\\nwidth of the road bed. For the same reasons,\\nand on account of the jarring motion, brick set-\\nting is out of the question, and hence it must be\\nself-contained. It must be capable of making\\nhigh-pressure steam quickly rather than econom-\\nically.\\nQ. Is the locomotive boiler economical in the\\nuse of fuel\\nA. Yes, but not as economical as the better\\ntypes of stationary boilers.\\nQ. How is the necessary strength of the flat\\nsurfaces of the fire-boxes obtained in locomotives?\\nA. By short stay-bolts connected to the outside\\nshell of the boiler. The top of the fire-box is\\nsometimes braced by girders called crown-bars,", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0112.jp2"}, "113": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 91\\na;nd sometimes to the semi-circular shell of the\\nboiler above by means of stay-bolts placed radially.\\nQ. What are the advantages and disadvantages\\nof the locomotive type of boiler\\nA. Its advantages are that it is compact, steams\\nquickly, and requires no brick setting. Its dis-\\nadvantages are that it is expensive, not as eco-\\nnomical as the best stationary boilers, and is inac-\\ncessible for cleaning and repairs.\\nQ. Are locomotive-type boilers used for station-\\nary purposes\\nA. Yes; they are well adapted for stationary\\nboilers where head room is limited, where it is\\ndesired to make steam quickl}^ rather than eco-\\nnomically, and where vibration or other condi-\\ntions would make brick setting undesirable.\\nQ. How is steam taken from locomotive boilers?\\nA. Usually from a steam dome placed on the top\\nof the shell. This is to insure dry-steam. Dry-\\npipes are also sometimes used instead of domes.\\nHOESE-POWER AND EFFICIENCY.\\nQ. What is meant by the term horse-poiver as\\napplied to steam boilers\\nA. A boiler of one horse-power capacity is one\\nwhich, under ordinary conditions, supplies as\\nmuch steam as is consumed in the average steam\\nengine in developing one horse-power.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0113.jp2"}, "114": {"fulltext": "92 eoper s catechism for\\nQ. Is there nothing more definite than this by\\nwhich the horse-power of boilers may be rated\\nA. Yes; the horse-power of steam boilers is now\\ngenerally based on an evaporative capacity of 30\\npounds of water per hour from feed-water at a\\ntemperature of 100\u00c2\u00b0 Fahr. to steam at a pressure\\nof 70 pounds. This was fixed by a committee of\\njudges at the Centennial Exposition in 1876, and\\nis equivalent to 33,305 heat-units per hour im-\\nparted to the water. It is known as the Centen-\\nnial Rating.\\nQ. How nearly does the horse-power of steam\\nboilers, rated according to this rule, come to the\\nactual consumption of steam in ordinary steam\\nengines\\nA. For an automatic cut-off, high-speed, non-\\ncondensing steam engine it is just about right.\\nFor plain slide-valve engines with throttling\\ngovernors the Centennial Rating is much too low,\\nwhile for multiple expansion and condensing\\nengines it is too high.\\nQ. How, then, would you fix the size of boilers\\nfor different engines, assuming that the horse-\\npower of the boilers were based on the Centennial\\nRating?\\nA. It is always well to have the boiler capacity\\na little in excess of that of the engine, because its\\nefficiency is not impaired by operating it below", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0114.jp2"}, "115": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 93\\nits rated capacity. If the engine were of the high-\\nspeed, automatic cut-off, single-expansion, non-\\ncondensing type, I should rate the boiler about\\n10 per cent, higher than the engine; if of the\\nsame type, but condensing, about equal; if plain\\nslide valve, non-condensing, with throttling gov-\\nernor, 40 to 50 per cent, higher; the same, con-\\ndensing, 10 to 20 per cent, higher; if automatic or\\nfour- valve non-condensing, about equal; the same,\\ncondensing, about 10 to 20 per cent, lower; if com-\\npound, high-speed, non-condensing, about 10 per\\ncent, lower; the same, condensing, 15 to 25 per\\ncent, lower if compound, four- valve, or Corliss,\\nnon-condensing, 10 to 15 per cent, lower; the same,\\ncondensing, 25 to 35 per cent, lower; if triple ex-\\npansion, non-condensing, 10 to 15 per cent, lower;\\nthe same, condensing, 35 to 45 per cent, lower.\\nQ. Why are the above rules only approximate\\nA. Because the evaporative capacity of a boiler\\ndepends on the temperature of the feed-water and\\nalso on the pressure of the steam. A boiler of\\n100 horse-power can evaporate 3000 pounds of\\nwater from 100\u00c2\u00b0 to steam at 70 pounds pressure;\\nbut if the temperature of the feed-water is less, or\\nif the pressure greater, it will not evaporate as\\nmuch, and vice versa.\\nQ. What, then, is the best method of determin-\\ning the size of a steam boiler", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0115.jp2"}, "116": {"fulltext": "94 roper s catechism for\\nA. The best method is to determme what amount\\nof steam is to be consumed and the pressure at\\nwhich it is to be dehvered to the engine, to specify\\nthese requirements and the desired evaporative\\nefficiency to the boiler-maker, and to leave the de-\\ntails of construction to him, binding him to guar-\\nantee the boiler to furnish the requisite amount of\\nsteam easily and under all conditions.\\nQ. Approximately, what horse-power of boiler\\n(Centennial Rating) would be required to supply\\nsteam to a 100 horse-power, four-valve, non-con-\\ndensing engine, consuming 26 pounds of steam\\nat 70 pounds pressure per horse-power per hour\\nA. Weight of steam required 100 X 26\\n2600 pounds per hour; H. P. (Centennial Rating)\\n87, but it would probably be better to use\\na boiler rated at 90 to 100 horse-power.\\nQ. What is meant by evaporative efficiency\\nA. The number of pounds of steam generated\\nper pound of fuel consumed.\\nQ. What, roughl}^, are the results that may be\\nobtained in this respect\\nA. In flue boilers of the best types, 6 to 9 pounds;\\nin tubular boilers, 8 to 10 pounds; in water- tube\\nboilers, 10 to 12 pounds of water per pound of coal;\\nthe average results, however, are from 10 to 25\\nper cent, below these figures.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0116.jp2"}, "117": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 95\\nGRATE AREA AND HEATING SURFACE.\\nQ. What determines the grate surface m boilers\\nA. Principally the quality of coal and the\\ndraught. In general, it is well to have the grate\\nsurface large, but not so large that the air passing\\nthrough it will be greatly in excess of the amount\\nrequired for combustion of the fuel.\\nQ. What amounts of coal can be consumed per\\nsquare foot of grate surface\\nA. Anywhere from 4 to 120 pounds, depending,\\nas already stated, upon the quality of the coal and\\nthe draught.\\nQ. What is meant by heating surface\\nA. The heating surface of a boiler means the\\naggregate area of all of the parts of the boiler which\\ncome in contact with the flame or products of\\ncombustion on the one side, and with the water\\nor steam on the other. In other words, it is all\\nthat part of the surface through which the heat of\\nthe fire is transmitted to the water or steam.\\nQ. How would you calculate the heating sur-\\nface of different types of boilers\\nA. Rule for Cylinder-Boilers. Multiply f\\nof the circumference of the shell in inches by its\\nlength in inches, add the area of one end in square\\ninches, and divide by 144. The quotient will be\\nthe number of square feet of heating surface.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0117.jp2"}, "118": {"fulltext": "96 roper s catechism for\\nRule for Flue-Boilers. Multiply f of the\\ncircumference of the shell in inches by its length\\nin inches;* multiply the combined circumference\\nof all the flues in inches by their length in inches.\\nTake the sum of these two products and add the\\narea of one end in square inches. Deduct the\\nsum of the areas of the cross-sections of all the\\nflues in square inches. The result divided by\\n144 is the heating surface in square feet.\\nRule for Vertical Tubular Boilers (such as\\nare generally used for fire-engines). Multiply the\\ncircumference of the fire-box in inches by its\\nheight above the grate in inches. Multiply the\\ncombined circumference of all the tubes in inches\\nby their length in inches, and to these two prod-\\nucts add the area of the lower tube- or crown-\\nsheet, and from this sum subtract the area of all\\nthe tubes, and divide by 144. The quotient will\\nbe the number of square feet of heating surface in\\nthe boiler.\\nRule for Horizontal Tubular Boilers.\\nMultiply f of the circumference of the shell in\\ninches by its length in inches; multiply the com-\\nbined circumference of all the tubes in inches by\\ntheir length in inches. To the sum of these two\\nproducts add f the area of both tube-sheets; from\\nthis sum subtract the combined area of all the\\ntubes divide the remainder by 144, and the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0118.jp2"}, "119": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 97\\nquotient will be the number of square feet of\\nheating surface.\\nRule for Locomotive Boilers. Multiply the\\nlength of the furnace-plates in inches by their\\nheight above the grate in inches; multiply the\\nwidth of the ends in inches by their height in\\ninches; multiply the length of the crown-sheet in\\ninches by its width in inches; also the combined\\ncircumference of all the tubes in inches by their\\nlength in inches; from the sum of these four\\nproducts substract the combined area of all the\\ntubes and the fire-door; divide the remainder by\\n144, and the quotient will be the number of\\nsquare feet of heating surface.\\nQ. How much heating surface per horse-power\\nshould be provided in fire- and water- tube boilers\\nA. About 12 to 15 square feet.\\nQ. How, then, can you approximate the horse-\\npower of a given boiler\\nA. By calculating the heating surface in square\\nfeet and dividing it by 14.\\nQ. What is the average ratio between grate and\\nheating surface in stationary boilers\\nA. The average is about 35 feet of heating sur-\\nface to 1 square foot of grate surface. This is for\\ngood anthracite coal, but for poorer grades the\\nproportionate surface of the grate should be\\nlarger.\\n7", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0119.jp2"}, "120": {"fulltext": "98 roper s catechism for\\nQ. How much coal, of good anthracite quality,\\ncan be consumed per square foot of grate under\\nordinary conditions?\\nA. About 11 pounds.\\nQ. According to these figures, how much coal,\\non an average, would be consumed per horse-^DOwer\\nper hour\\nA. Heating surface per H. P., 12 sq. ft.\\nGrate 1.\\nCoal consumption per sq. ft. of\\ngrate per hour, =11 lbs.\\nCoal consumption per H. P. per\\nhour, X 11 3f lbs.\\nQ. If all the heat in the fuel were utilized in\\nmaking steam, what would be the smallest theo-\\nretical amount of good anthracite coal consumed\\nper hour\\nA. Heat-units required per\\nH. P. (Cent l R g), 33,305\\nHeat-units in best an-\\nthracite coal, 14,000\\nMinimum consumption\\nper H. P. per hour, fll^l 2.4 lbs.\\nBOILER SHELLS.\\nQ. What materials are used for boiler shells\\nA. Wrought iron and steel. The latter is rap-\\nidly replacing the former as a boiler material.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0120.jp2"}, "121": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 99\\nQ. Why is steel preferred\\nA. Because for a given strength it is hghter\\nand, as a thinner plate may be used, the efficiency\\nof the heating surface is greater.\\nQ. What thickness of boiler plate do you con-\\nsider the safest, most durable, and economical for\\nboilers\\nA. First, to insure safety in shells and flues of\\nboilers; the thickness proper to use depends very\\nmuch on the quality of the iron, diameter of\\nboiler, and pressure to be carried. Secondly, as to\\ndurability, the thickest iron is not always the\\nbest, as the outside of the sheet becomes burned\\nand crystallized, and in most cases gives less wear\\nand satisfaction than a thinner gauge. Thirdly,\\nas to economy, thin boilers are more economical\\nwith fuel, and wear longer, provided in all cases\\nthat the diameter and the pressure are in propor-\\ntion.\\nQ. What would you consider the proper thick-\\nness for boilers\\nA. The thickness of boiler iron or steel should\\nrange between f and y\\\\- of an inch, for the rea-\\nson that plates of greater thickness than f of an\\ninch are liable to burn, especially if the circula-\\ntion is poor, and they are difficult to work and\\nrivet. If the plates are less than y\\\\ of an inch\\nthick, they cannot be properly caulked, and they", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0121.jp2"}, "122": {"fulltext": "100 roper s catechjsm for\\nare liable to waste away by corrosion so as to\\nimpair the safety of the boiler.\\nQ. What properties should be possessed by\\nmaterials used for boiler plates\\nA. Whether iron or steel, the test-piece should\\nhave a tensile strength of not less than 50,000\\npounds per square inch it should elongate 25\\nper cent, in 8 inches before breaking, and should\\ncontract 50 per cent, in cross-section at the point\\nwhere rupture takes place. It should stand bend-\\ning without injury around a radius equal to the\\nthickness of the 23late.\\nQ. Is the pressure the same on all riveted seams\\nin boiler shells\\nA. No; the pressure on the longitudinal rivets\\nis nearly double that on the curvilinear rivets.\\nQ. What do you mean by longitudinal and cur-\\nvilinear rivets\\nA. By longitudinal rivets I mean those that run\\nlengthwise on the boiler; the curvilinear are those\\nthat are around the circumference of the shell.\\nQ. If the pressure on the longitudinal seams is\\ndouble that on the curvilinear, how can all parts\\nof the boiler sustain the same pressure?\\nA. By making the longitudinal seams double\\nriveted and the curvilinear single.\\nQ. What is the difference in strength between\\nsingle- and double-riveted seams?", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0122.jp2"}, "123": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. lOl\\nA. Single-rivetecl seams are equal to about 56\\nper cent, of the material used, while double rivet-\\ning is equal to about 70 per cent.\\nQ. What do you mean by equal to about\\n56 per cent, of material used\\nA. I mean that the boiler plates lose 44 per\\ncent, of their strength in the process of riveting.\\nQ. What do you consider the proper diameter\\nfor rivets of boilers\\nA. That would depend very much on the diam-\\neter of the boiler, thickness of iron, and pressure\\nto be carried. For boilers from 36 to 42 inches\\ndiameter, and f iron, if single riveted, the rivets\\nought to be f of an inch for curvilinear, and f for\\nthe longitudinal; if double riveted, f will answer\\nfor both longitudinal and curvilinear seams.\\nFrom -f-Q iron down to y\\\\ smaller rivets will\\nanswer.\\nQ. Which do you consider the best method of\\nriveting boilers, by hand or by machine\\nA. For average or thin boiler plates, hand\\nriveting does very well, but for heavy iron, ^^g- or\\nJ inch thick, machine work is far superior; the\\npower of the machine brings the work together\\nbetter and with less injury to the iron than can be\\ndone by hand.\\nQ. How should the fiber of the iron be placed\\nto give the greatest strength", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0123.jp2"}, "124": {"fulltext": "102 roper s catechism for\\nA. The direction in which the iron is rolled\\nshould always be placed around the boiler, and\\nnot lengthwise, because in cylindrical boilers the\\nstrain in the line of the axis is much less than the\\ncircumferential bursting strain.\\nQ. Do you consider it an advantage to drill the\\nrivet-holes in boilers instead of punching\\nA. Yes; for all first-class work there can be no\\ndoubt but that all the rivet-holes ought to be\\ndrilled, on account of the liability of the plates\\nto become fractured by the process of punching,\\ncausing a great reduction in the strength of the\\nboilers.\\nQ. Do you consider the use of the drift-pin\\nought to be dispensed with as much as possible in\\nmaking boilers\\nA. Yes; a reckless use of the drift-pin has in\\nmany cases resulted in great injury to the boiler\\nplates; and there is good reason to believe that\\nsuch injuries as are caused by the drift-pin often\\nhasten the destruction of the boiler.\\nQ. What is a drift-pin\\nA. It is a tapering steel pin introduced into the\\nholes in the seams, to bring them into line.\\nQ. How do you propose to dispense with the\\nuse of the drift-pin?\\nA. If the holes are laid off carefully in the\\nsheet, and punched with judgment, there will be", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0124.jp2"}, "125": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 103\\nvery little need for the clrift-pin, as the holes can\\nbe straightened by a flat reamer. Such work will\\nbe greatly superior to that where the drift-pin is\\nused.\\nQ. Do you think i^ would be of any benefit to\\nslightly heat the boiler plates before rolling them\\nto form the shell of the boiler?\\nA. Yes; I think it would add very materially\\nto the strength and durability of boilers if the\\nsheets were rolled while warm, as the fiber of the\\niron would be drawn out; while, in the common\\npractice of cold rolling, the fiber is crushed and\\nbroken.\\nQ. Does hammering improve the quality of\\niron\\nA. No; it only hardens it, but at the same time\\nrenders it more brittle, while rolling imparts\\ntoughness.\\nQ. What fact is observable when boiler iron is\\nbroken suddenly, as in the case of steam-boiler\\nexplosions\\nA. It generally presents a crystalline fractured\\nappearance; when, if broken by some slow pro-\\ncess, it presents a fibrous or silky appearance,\\nin the first case the fiber is fractured, and in the\\nother it is drawn out.\\nQ. What does the crystalline fracture indicate\\nA. It indicates hardness, while a fibrous fracture", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0125.jp2"}, "126": {"fulltext": "104 roper s catechism for\\nis a mark of softness and ductility. The finer and\\nmore uniform the crystals, the higher the qualit}^\\nof the iron.\\nQ. Is the pressure equal on all sides of the shell\\nof a boiler when under steam\\nA. No; there is more pressure on the lower than\\non the upper side of a boiler; as the steam presses\\nequally on the surface of the water as on the upper\\nside of the boiler, the weight of the water must\\nbe added to the pressure on the lower side.\\nQ. Are the shells and flues of boilers sometimes\\ninjured by the application of the cold-water or\\nhydrostatic test\\nA. Yes; the shells and flues of boilers are some-\\ntimes injured by a reckless use of the test, and in\\nmany cases explosions take place soon after the\\ntest is applied.\\nQ. Would the shell and flues of a boiler be\\nstronger under a cold-water pressure of 70 or 80\\npounds to the square inch than under the same\\nsteam pressure\\nA. No; as iron increases in strength by the\\napplication of heat up to 550\u00c2\u00b0 Fahr., the boiler\\nwould be stronger under the steam pressure.\\nQ. How do you calculate the bursting pressure\\nper square inch of a C3dindrical boiler?\\nA. The rule is to multiply the thickness of the\\nshell in inches by the tensile strength of the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0126.jp2"}, "127": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 105\\nmaterial in pounds per square inch, and divide\\nthe product by one-half the diameter of the boiler\\nin inches.\\nQ. How do you calculate the safe working\\npressure\\nA. Multiply the thickness of the shell in inches\\nby the tensile strength in pounds per square inch.\\nMultiply one-half the diameter by the factor of\\nsafety. Divide the first product by the second,\\nand the quotient will be the safe working pressure.\\nQ. What is meant by the factor of safety\\nA. By factor of safety is meant the ratio of the\\nultimate breaking strength to the proper allowable\\nworking strength. For example, if a boiler shell\\nis made of steel having a tensile strength of\\n60,000 pounds and the thickness is calculated with\\na factor of safety of 4, the greatest strain which\\nwould come on any square inch of cross-section\\nis 15,000 pounds; or, in other words, the boiler\\ncould carry four times as much pressure before\\nbursting.\\nQ. What is the factor of safety usually em-\\nployed in designing boiler shells\\nA. It varies from 3 to 5. A safe average for\\nstationary boilers is 4.\\nQ. What value of tensile strength must be used\\nin the above rules for working and bursting pres-\\nsure", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0127.jp2"}, "128": {"fulltext": "106\\nROPER S CATECHISM FOR\\nA. That depends on how the joints are riveted.\\nThe value of tensile strength in the above rules is\\nthe ultimate breaking strength of the material\\nmultiplied by the efficiency of the joint.\\nQ. What do you mean by the efficiency of the\\njoint\\nA. I mean the number by which the original\\nstrength of the material must be multiplied to\\ngive its strength after riveting.\\nt(S O O (9 Q O ID\\nQ. What is the efficiency of single- and double-\\nriveted joints\\nA. As already stated above, it is about j^-^-q for\\nsingle-riveted and about -^q- for double-riveted\\njoints. The efficiencies of joints depend, how-\\never, not only on the thickness of j^late, but also\\non the spacing of the rivets and the material used.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0128.jp2"}, "129": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 107\\nQ. How would you express by formulae the\\nrelations existing between safe working pressure,\\nbursting pressure, thickness of shell, efficiency of\\njoint, and factor of safety\\nA. If p is the safe working pressure in pounds\\nper square inch,\\nP bursting pressure in pounds per\\nsquare inch,\\nW ultimate tensile strength in\\npounds per square inch,\\nt thickness of shell in inches,\\ne efficiency of the joint,\\nfactor of safety,\\nd diameter of boiler in inches.\\nTo find the bursting pressure:\\nj,_ t X WX e\\nid\\nTo find the safe working pressure\\n_tXWXe\\nidXf\\nTo find the thickness of shell for a given work-\\ning pressure and factor of safety:\\n_ i^ XpXf\\nWX e\\nTo find the factor of safet}^ of a given boiler:\\nf WX e X t", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0129.jp2"}, "130": {"fulltext": "108 eoper s catechism for\\nQ. As an example: If a boiler 48 inches in\\ndiameter is made of steel having an ultimate ten-\\nsile strength of 55,000 pounds per square inch,\\nthickness of shell f of an inch, joints double\\nriveted, what is the bursting pressure\\nr I X 55,000 X .70\\nA. P :r-^ -i^ 1000 pounds\\ni X 48\\nper square inch.\\nQ. With a factor of safety of 5, what would be\\nthe safe working pressure\\nf X 55,000 X .70\\nA. p= -r x-4^^^ 200 pounds\\nper square inch.\\nQ. If the boiler had to work under 150 pounds\\npressure with a factor of safety of 4, what would\\nbe the proper thickness of shell\\n1 X 48 X 150 X 4 3\\nA. t 55^000 X. 70\\nQ. If a boiler of the same diameter were made\\nof wrought, iron having an ultimate tensile\\nstrength of 50,000 pounds, shell inch thick,\\njoints single riveted, what would be the factor of\\nsafety for a working pressure of 100 pounds\\n^__ 50,000 X .56 X4 _^^^\\niX48x 100\\nwhich is somewhat higher than is usually allowed\\nby boiler makers.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0130.jp2"}, "131": {"fulltext": "STEAM E^-GINEERS AND ELECTRICIANS. 109\\nBOILER SETTING.\\nQ. What materials should be used for settmg\\nboilers\\nA. The walls should be of hard burned brick\\nlaid in Portland cement. They should be of\\nample thickness so as to prevent loss by radiation.\\nAll surfaces exposed to the action of the hot gases\\nshould be lined with best quality fire-brick laid in\\na thin mortar of fire-clay.\\nQ. What should be the course of the gases in\\na tubular boiler\\nA. It should be set in such a way that the gases\\ndo not pass over the top of the boiler, unless there\\nis ample space for a man to enter and clean off\\nsoot.\\nQ. What should be the distance between the\\ngrate bars and the bottom of the boiler shell\\nA. Not less than 24 inches. In large boilers it\\nmay be as much as 30 inches.\\nQ. What should be the distance between the\\nback tube sheet and rear wall\\nA. From 18 inches for a 48-inch shell to 24\\ninches for a 72-inch shell.\\nQ. What is the best method of holding boiler\\nwalls in place?\\nA. With the aid of buck-staves.\\nQ. What are buck-staves", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0131.jp2"}, "132": {"fulltext": "110 roper s catechism for\\nA. Vertical cast- or wrought-iron braces placed\\non the outside of the boiler walls, held together at\\nthe top and bottom by tie-rods. Buck-staves are\\noften made of rails, flattened at the end to take\\nthe tie-rods.\\nQ. How should the front of boilers be inclosed\\nA. The best method is by a full flush front,\\nwhich consists of cast-iron plates covering the\\nentire front of the setting, leaving no brickwork\\nin sight. The half-arch front which covers only\\nthe furnace is cheaper but less desirable.\\nQ. When a number of boilers are set together,\\nAvhat plan should be adopted\\nA. Each boiler should be set independently of\\nthe others, and each should have a separate con-\\nnection to the stack.\\nQ. Why is this arrangement better than the\\nold way of setting them in batteries, with a com-\\nmon flue connection\\nA. Because each boiler can be operated and shut\\ndown independently of the others; because the\\ndraught of one is not affected by the others; and,\\nfinally, because with the old method of setting, it\\noften happened that when one shell gave out the\\nwhole battery exploded.\\nQ. What kind of boiler should be used where\\nexcessive vibration exists or where brickwork\\nwould be too heavy", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0132.jp2"}, "133": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. Ill\\nA. A locomotive- or marine-type boiler is fre-\\nquently used under these circumstances, because\\nthey require no brickwork whatever.\\nf\\nCARE AND MANAGEMENT.\\nQ. What is the first duty of an engineer when\\nhe takes charge of an engine and boiler\\nA. It is his duty to examine his boiler and see\\nthat the water is at the proper level.\\nQ. How much water should the boiler contain\\nwhen in use\\nA. The water should be kept up to the second\\ngauge while working, and up to the third at night.\\nQ. Why should the level of the water be raised\\nat night\\nA. As a precaution against the water becoming\\ntoo low from leakage or evaporation.\\nQ. In case the water should become dangerously\\nlow, what would be the duty of the engineer\\nA. He should immediately draw the fire and\\nallow the boiler to cool, and not admit any cold\\nwater to the boiler or attempt to raise the safety\\nvalve, as it would be positively dangerous.\\nQ. Why would it be dangerous to raise the\\nsafety valve\\nA. Because it would lessen the pressure in\\nallowing the steam to escape from the boiler, thus\\npermitting the water to rise up and come in con-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0133.jp2"}, "134": {"fulltext": "112 roper s catechism for\\ntact with the overheated iron, and probably cause\\nan explosion.\\nQ. In case the water-supply should be cut off\\nfrom the boiler for a short time, what w^ould be\\nthe duty of the engineer\\nA. He should cover his fire with fresh fuel, stop\\nhis engine, and keep the regular quantity of w^ater\\nin the boiler until the accident is repaired and the\\nwater-supply renewed.\\nQ. How should an engineer proceed to get up\\nsteam\\nA. He should first see that the water is at the\\nproper level; he should then remove all ashes and\\ncinders from the furnace, and cover the grate with\\na thin layer of coal; and after placing wood and\\nshavings on the coal, he will be ready to start the\\nfire.\\nQ. What advantage is it to place a covering of\\ncoal on the grate before the wood or shavings\\nA. It is a saving of fuel, as the heat that would\\nbe transmitted to the bars is absorbed by the coal,\\nand the bars are also protected from the extreme\\nheat of the fresh fire.\\nQ, Should an engineer allow his fire to burn\\ngradually when he commences to get up steam\\nfrom cold water\\nA. Yes; as by allowing the fuel to burn very\\nrapidly, some parts of the boiler become expanded", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0134.jp2"}, "135": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 113\\nto their utmost limits, while other parts are nearl}^\\ncold. Of course, a great deal depends upon the\\ntime in which he has to raise steam.\\nQ. How should an engineer regulate his fire\\nA. He should always keep the fire at a uniform\\nthickness, and not allow any bare places or accu-\\nmulations of ashes or dead coals in the corners of\\nthe furnace, as these places admit great qviantities\\nof cold air into the furnace and render the com-\\nbustion very imperfect.\\nQ. Should an engineer avoid excessive firing as\\nmuch as possible?\\nA. Yes; as excessive firing is always attended\\nwith more or less danger, because the intense heat\\nrepels the water from the surface of the iron and\\nallows the boiler to be burned.\\nQ. How thick should an engineer keep his fires\\nA. About 3 inches for anthracite coal and about\\n5 inches for soft coal; but he should regulate the\\nthickness of the fire according to the capacity of\\nthe boiler; if the boiler is too small for the engine,\\nthe fire should be kept thin, the coal supplied in\\nsmall C[uantities and distributed evenly over the\\ngrate, and the grate kept as free as possible from\\nashes and cinders; but if the boiler is extra large\\nfor the engine, the thickness of the fire makes but\\nlittle difference.\\nQ. What should an engineer do in case, from", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0135.jp2"}, "136": {"fulltext": "114 roper s catechism for\\nneglect or any other cause, his fire should become\\nvery low\\nA. He should neither poke nor disturb it, as\\nthat would have a tendency to put it entirely out,\\nbut he should place shavings, sawdust, wood, or\\ngreasy waste on the bare places, with a thin cover-\\ning of coal; then by opening the draught to its\\nfull extent the fire will soon come up. If it\\nshould become necessary to burn wood on a coal\\nfire, it is always best to make an opening through\\nthe coal to the grate-bars, so that the air from the\\nbottom of the furnace can act directly on the wood\\nand increase the combustion.\\nQ. Should an engineer give great attention to\\nthe regulation of the draught in the furnace\\nA. Yes; the regulation of draught is one of the\\nmost important of an engineer s duties; in fact,\\nit is next in importance to the regulation of the\\nwater in the boiler.\\nQ. How do you explain that\\nA. Because it is well known that immense\\nquantities of fuel are recklessly wasted by igno-\\nrance and carelessness in the management of the\\ndraught.\\nQ. How should an engineer regulate his draught\\nto obtain the best results from the fuel\\nA. He should have no more draught at any time\\nthan would produce a sufficient combustion of the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0136.jp2"}, "137": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 115\\nfuel to keep the steam at the working pressure, as\\nby opening the clamper to its utmost limits great\\nquantities of heat are carried into the chimney\\nand lost.\\nQ. Can an engineer carry out this principle of\\nregulating the draught in all cases\\nA, No; only in furnaces and boilers that are\\nsufficiently large to furnish the necessary amount\\nof steam without forcing. Of course, where the\\nboiler is too small for the engine, or has not suf-\\nficient heating surface it is impossible to economize\\nfuel.\\nQ. Is it objectionable to throw steam or water\\nunder the grate-bars of locomotive boilers, when\\nsuch boilers are used for stationary engines\\nA. Yes; as steam or water in the ashpit forms\\na lye with the ashes and corrodes the iron and\\ndestroys the water-legs of the boiler.\\nQ. Should an engineer in all cases keep his ash-\\npit clean\\nA. Yes; by allowing the ashpit to become filled\\nwith ashes and cinders the air becomes heated to\\na high temperature before entering the fire; the\\ngrate-bars also become overheated, and in many\\ncases either badly warped or melted down.\\nQ. How should an engineer keep his safety\\nvalve\\nA. He should keep it at all times in good work-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0137.jp2"}, "138": {"fulltext": "116 roper s catechism for\\ning order, and move it at least once a day, partic-\\nularly in the morning,\\nQ. AVhy should he move the safety-valve every\\nmorning\\nA. To see that all its parts are in good working\\norder before getting up steam.\\nQ. Would you consider it reprehensible conduct\\non the part of an engineer who would weight his\\nsafety-valve in order to carry a pressure greater\\nthan that he knew to be safe\\nA. Yes; such conduct, if proved, ought to be\\nsufficient to disqualify any engineer from ever\\ntaking charge of an engine and boiler again.\\nQ. What is the duty of an engineer in regard to\\nblowing out his boilers\\nA. He should carefully remove all the fire from\\nthe furnace, and see that the steam is at the proper\\npressure, say from 45 to 50 pounds. He should\\nalso close his damper.\\nQ. Should any time intervene between the\\ndrawing of the fire and the blowing out of the\\nboiler?\\nA. Yes; at least one hour.\\nQ. Why should the blowing out of the boiler\\nbe deferred for an hour after the fire is drawn\\nA. To allow the furnace to cool, and prevent\\nthe boiler from being injured with the heat after\\nthe water is all blown out.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0138.jp2"}, "139": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 117\\nQ. Why not blow out the boiler under a high\\npressure of steam, say 70, 80, or even 90 pounds\\nto the square inch\\nA. Because the higher the steam pressure the\\nhigher the temperature of the iron, so that by\\nblowing out the boiler under a high steam pressure,\\nthe change is so sudden that it has a tendency to\\ncontract the iron and cause the boiler to leak.\\nQ. Should the engineer fill his boiler with cold\\nwater immediately after blowing out\\nA. No; as the introduction of cold water into\\nthe boiler before the temperature of the iron\\nbecomes lower would in all probability cause the\\nboiler to leak.\\n,Q. How often should an engineer blow out his\\nboiler\\nA. Whenever he discovers any appearance of\\nmud in the water.\\nQ. Is it not customary with some engineers and\\nowners of steam boilers to blow^ out their boilers\\nonce a week\\nA. Yes; but the wisdom of this practice is\\ndoubtful. When fresh water is boiled, it is sup-\\nposed to deposit its minerals, and after that it is\\nnot advisable to blow out the pure water and fill\\nthe boiler with water holding matter in solution\\nand suspension. How often a boiler should be\\nblown out depends on the nature of the water used.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0139.jp2"}, "140": {"fulltext": "118 roper s catechism for\\nQ. Should an engineer, when filUng his boilers,\\nopen some cock or valve in the steam room of the\\nboiler and allow the air to escape\\nA. Yes; otherwise the air would retard the\\ningress of the water, and also collect in the steam\\nroom of the boiler and prevent the regular expan-\\nsion of the iron when the fire is started.\\nQ. What do you mean by the steam room of a\\nboiler?\\nA. 1 mean that portion of the boiler occupied\\nby steam above the water.\\nQ. AVhat is meant by the water room in a steam\\nboiler\\nA. That portion of the boiler occupied by water.\\nQ. What do you call the fire-line of the boiler\\nA. The fire-line of the boiler is a longitudinal\\nline above which the fire cannot rise on account of\\nthe masonry by which the boiler is surrounded.\\nQ. How often should an engineer clean the tubes\\nor flues of his boiler\\nA. At least once a week; he should also remove\\nall ashes and soot that become attached to the out-\\nside of the boiler.\\nQ. What advantage is gained by cleaning the\\nflues and tubes regularly, and also removing the\\nsoot and ashes that become attached to the boiler\\nA. It makes a great saving in fuel, as it allows\\nthe fire to act directly upon the iron.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0140.jp2"}, "141": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 119\\nQ. How often should an engineer clean his\\nboilers\\nA. Every three months, if possible.\\nQ. Should an engineer, when cleaning his boil-\\ners, examine all stays, braces, seams, and angles\\nof the boiler or boilers\\nA. Yes; he should make a thorough examina-\\ntion of all parts of the boiler, seams, rivets,\\ncrown-sheet, crown-bars, crow-feet, cotters, and\\nbraces; he should also sound the shell of the\\nboiler with a very light steel hammer.\\nQ, Why should the engineer sound the boiler?\\nA. Because it is the only way in which he can\\ndetermine the condition of the iron.\\nQ. How often should an engineer test his steam-\\ner pressure-gauge\\nA. At least once a year.\\nQ. Can an engineer test a steam-gauge himself\\nA. No; unless he has a test-gauge, which is not\\nvery often the case. The gauge ought to be tested\\nby another gauge built or made expressly for that\\npurpose.\\nQ. How should an engineer keep his glass\\nwater-gauges\\nA. He should keep them perfectly clean inside\\nand out.\\nQ. How can an engineer clean his glass water-\\ngaus es inside", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0141.jp2"}, "142": {"fulltext": "120 roper s catechism for\\nA. By opening the drip-cock and closing the\\nwater- valve, and allowing the steam to rush down\\nthe glass and carry out the mud or sediment.\\nThey should also be swabbed out with a piece of\\ncloth or waste on a small stick, when the boiler is\\ncold; but care should be taken not to touch the\\ninside of the glass with wire or iron, as an abrasion\\nAvill immediately take place.\\nQ. In case an engineer has a glass water-gauge,\\nshould he neglect his gauge-cocks\\nA. No; he should examine them several times\\nin the day, see that they are in good working order,\\nand grind or repair them if necessary. He should\\nalways be sure to shut them tight, as by leaving\\nthem loose the steam and water destroy the seat\\nof the valve and render them useless.\\nQ. What evidence do dirty or broken glass\\ngauges, filthy boiler-heads, leaking and muddy\\ngauge-cocks give of a man s ability as an en-\\ngineer\\nA. They furnish strong evidence of his igno-\\nrance or neglect of duty.\\nQ. What should an engineer do in cold weather,\\nwhen his pumps, boiler connections, steam gauges,\\nor water-pipes are liable to be frozen\\nA. He should open all drip- or discharge-cocks\\nand allow the water to run out when he stops work\\nat night, and in the morning make a thorough", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0142.jp2"}, "143": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 121\\nexamination of all steam- and water-connections\\nbefore he starts his fires.\\nQ. In case it becomes necessary to stop the\\nengine, and the steam commences to blow off at\\nthe safety-valve, what is the duty of the engineer\\nA. He should immediately start his pump or\\ninjector, and also cover his fire with fresh coal, so\\nthat the circulation might be kept up by the feed-\\nwater, and the extreme heat of the fire absorbed\\nby the fresh coal, instead of being communicated\\nto the iron of the boiler; and he should not\\nattempt, under any circumstances, to interfere\\nwith the free escape of the steam through the\\nsafety-valve.\\nQ. Whenever the fire-door of the furnace is\\nopen, should the damper be closed, if possible\\nA. Yes; the door and the damper should never\\nbe open at the same time, unless it is absolutely\\nnecessary, as the cold air, that would otherwise\\nhave to pass through the fire and become heated,\\nrushes in through the open door above the fire and\\nimpinges on the tube and crown-sheets, and has a\\ntendency to contract the seams and cause leakage.\\nQ. In case it should become necessary to ex-\\namine the check-valve while steam is on the boiler,\\nhow should it be done\\nA. The stop-cock between the check-valve and\\nboiler should be first closed before any attempt is", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0143.jp2"}, "144": {"fulltext": "122 roper s catechism for\\nmade to unscrew or remove the check. Any\\nneglect to close the stop-cock might result in a\\nserious accident.\\nQ. How should an engineer proceed to make a\\njoint on the man-hole or hand-holes of his boiler\\nA. He should first carefully remove all gum or\\nother material from the seat or flange where the\\njoint is to be made, so that the gasket may have a\\nsmooth and solid bearing before he commences to\\ntighten the nut.\\nQ. Do you know any other important duty an\\nengineer should consider himself bound to per-\\nform\\nA. Yes; he should daily make a thorough ex-\\namination of all safety-valves, pumps, injectors,\\nand all steam- and water-connections.\\nQ. What should be said of an engineer who\\nwould allow his boiler and engine to run jon from\\nbad to worse, expecting some day to have a general\\noverhauling, instead of making repairs as they\\nwere needed\\nA. He should be considered totally unfit for\\nthe position of an engineer.\\nQ. When can it be said that an engineer has\\ndone his duty\\nA. When he shows by his work that he has\\ncared for everything connected with his engine and\\nboiler in the best possible manner.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0144.jp2"}, "145": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 123\\nSCALE-FORMATION, CORROSION, FOAMING,\\nAND PRIMING.\\nQ. What are the results of scale in boilers, and\\nwhy?\\nA. Increased coal consumption and burning of\\nthe plates. Because the scale being a poor con-\\nductor of heat, the heat of the fire is not imparted\\nto the water as completely as if the scale were not\\nthere. For the same reason the water does not\\nprotect the iron against crystallization and burning.\\nQ. What, roughly, is the conductivity of scale\\nas compared to iron\\nA. About 1 35.\\nQ. What are the principal ingredients contained\\nin water which cause the formation of scale\\nA. Sulphate of lime, phosphate of lime, car-\\nbonate of lime, magnesia, silica, and alumina.\\nIn sea-water the most important of these is sul-\\nphate of lime.\\nQ. How may the formation of scale be checked\\nA. By the use of boiler compounds.\\nQ. Is there any boiler compound which will be\\neffective in all cases\\nA. No; the composition of a boiler compound\\nshould be determined by the nature of the im-\\npurities. Thus, a proper amount of carbonate of\\nsoda introduced regularly with the feed- water", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0145.jp2"}, "146": {"fulltext": "124 roper s catechism for\\nwould prevent the formation of scale if the in-\\ngredient in the water which tends to produce it is\\nsulphate of lime; but this would be of no value\\nif the scale producing substance is silica or\\nalumina.\\nQ. What are the principal substances used to\\ncheck the formation of scale\\nA. Carbonate of soda if the scale-forming in-\\ngredient is sulphate of lime; phosphate of sodium\\nfor the sulphates of lime and magnesium; milk\\nof lime for the carbonates of lime and magnesium;\\ncaustic soda and soda ash for the carbonate and\\nsulphate of calcium; and sulphate of magnesium\\nand tannate of soda foT the sulphate and carbonate\\nof lime.\\nQ. How, then, should we proceed if it is found\\nthat an undue amount of scale forms in the\\nboiler\\nA. We should have a chemical analysis of the\\nfeed-water made and add sufficient quantities of\\nthe proper kinds of salts to transform the scale-\\nproducing ingredients into soluble salts.\\nQ. In what other ways may the formation of\\nscale be prevented\\nA. The use of feed-w^ater heaters and purifiers\\nof the open type is often sufficient, especially\\nwhere the amount of impurity is not very great.\\nQ. In what way does this remedy the difficulty?", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0146.jp2"}, "147": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 125\\nA. By causing the impurities to be deposited\\nin the heater or purifier, where they can do no\\nharm and whence they may easily be removed\\nwithout interfering with the operation of the plant.\\nQ. What is meant by corrosion\\nA. By corrosion is meant the wasting, pitting,\\nor grooving of the iron in the boiler.\\nQ. To what is it generally due\\nA. External corrosion is due to the chemical\\naction of sulphur or other products contained in\\nthe fuel and in the atmosphere. Internal corro-\\nsion is caused by the chemical action of acid and\\nmineral substances contained in the water.\\nQ. AVhat are the remedies\\nA. Numerous remedies are employed to prevent\\ninternal corrosion, such as painting the interior of\\nthe boiler with Portland cement, allowing a thin\\nlayer of scale to form, or suspending metallic zinc\\nin the water and steam spaces, all of which are\\neffective in some cases. There seems to be no\\neffectual remedy against external corrosion when\\nproduced by foreign substances contained in the\\nfuel.\\nQ. What is meant by foaming\\nA. By foaming is meant a violent agitation of\\nthe water in the boiler. It can be detected by the\\nrising and falling of the level of the water in the\\ngauge glass and by its disturbed condition.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0147.jp2"}, "148": {"fulltext": "126 roper s catechism for\\nQ. What is the cause of foaming in steam\\nboilers\\nA. Foaming in steam boilers might be attributed\\nto different causes. First^ to the boiler not having\\na sufficient amount of steam-room, so that when-\\never the valve opens to admit steam to the cylinder,\\nthe pressure on the surface of the water is less-\\nened, allowing the water to rise up from the bot-\\ntom of the boiler. Second^ foaming is sometimes\\ncaused by the foul condition of the boiler; but in\\nsuch cases it will be easy to discover the cause, as\\nthe water in the glass gauge will appear quite\\nmuddy. Third, foaming is caused by the presence\\nof any substance of a soapy or greasy nature in\\nthe water. But whatever may be the cause of\\nfoaming, it is always attended with great danger\\nto the boiler and a certain amount of injury to the\\nengine.\\nIn all cases where a boiler foams badly, the\\nwater is lifted from the fire-surface of the boiler,\\nand allows the iron to burn; also, the mud and\\nwater from the boiler are carried over with the\\nsteam to the cylinder, occupying the clearance\\nbetween the piston and the head of the cylinder,\\nnot only destroying the surface of the cylinder by\\nthe grit and dirt, but in many cases causing the\\nfracture of the cylinder-head.\\nQ. What is the best preventive against foaming", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0148.jp2"}, "149": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 127\\nA. The best preventives against foaming are\\nFirst, a clean boiler. Second, pure water. Third,\\na sufficient amount of steam-room. Fourth, a\\nsteam pipe well proportioned to the size of the\\nengine.\\nQ. What is meant by priming\\nA. The passage of water from the boiler to the\\ncylinder of the engine in the shape of spray.\\nQ. How may it be detected\\nA. By the appearance of the exhaust from the\\nengine, which, when moist, is white instead of\\ncolorless, as is the case when dry, and by a click-\\ning noise in the cylinder, which almost invariably\\naccompanies the presence of moisture.\\nQ. AVhat causes priming\\nA. Usually the want of sufficient steam space\\nin the boiler, or the water being carried at too\\nhigh a level.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0149.jp2"}, "150": {"fulltext": "128 roper s catechism for\\nADJUNCTS OF STEAM BOILERS.\\nTHE SAFETY-VALVE.\\nThe form and construction of this indispensable\\nadjunct to the steam boiler are of the highest\\nimportance, not only for the preservation of life\\nand property, which would in the absence of this\\nmeans of safety be constantly jeopardized, but also\\nto secure the durability of the steam boiler itself.\\nIncreasing the pressure to a dangerous degree\\nwould be impossible in any boiler if the safety-\\nvalve were what it is supposed to be, a perfect\\nmeans for liberating all the steam which a boiler\\nmay produce with the fires in full blast, and all\\nother means for the escape of steam closed. Until\\nsuch a safety-valve shall be devised and adopted\\nin general use, safety from gradually increasing\\npressure must depend on the attention and watch-\\nfulness of the engineer.\\nQ. AVhat is the object of the safety-valve?\\nA. It is a valve intended to relieve the boiler\\nfrom extra pressure, and prevent bursting, col-\\nlapse, or explosion.\\nQ. How is this accomplished\\nA. By balancing the steam pressure against that\\nof a spring or weight in such a way that when the\\npressure in the boiler exceeds the limit of safety,", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0150.jp2"}, "151": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 129\\nit overcomes the action of the spring or weight\\nand opens a valve, allowing the surplus pressure\\nto be relieved.\\nQ. How often should the safety-valve be moved\\nA. At least once a day, more particularly in the\\nmorning.\\nQ. Why should the safety-valve be moved in\\nthe morning?\\nA. So as to be sure that it is in good working\\norder before starting the fire.\\nQ. What are the most important principles to be\\nadhered to in the construction of the safety-valve\\nA. Simplicity of construction, directness, and\\nfreedom of action.\\nQ. Does the safety-valve become worn and\\nleaky by the continual action of the steam\\nA. Yes; all safety-valves become leaky and\\nought to be ground carefully on their seats.\\nQ. What is the best material to use for grinding\\nsafety-valves\\nA. Pulverized glass, grit of grinding-stones, or\\nfine emery.\\nQ. Should safety-valves be constructed with\\nloose or vibratory stems\\nA. Yes; as the rigid or solid stem is apt to be-\\ncome jammed by the canting of the lever and\\nweight, and in such cases the higher the pressure\\nthe more difficult it is for the valve to open.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0151.jp2"}, "152": {"fulltext": "130 roper s catechism for\\nQ. What are the principal kinds of safety-\\nvalves\\nA. There are three principal classes, namely:\\n(a) The dead-weight safety-valve, in which\\nthe pressure of the steam is balanced\\nby a weight placed directly on the\\nvalve-spindle.\\n(b) The spring safety-valve, which is similar\\nto the above except that the weight\\nis replaced by a spring.\\n(c) The lever safety-valve, in which a weight\\nor spring, instead of acting directly\\non the valve-spindle, is attached at\\nthe end of the lever, the adjustments\\nbeing made by altering its position\\non the lever.\\nQ. What are the relative advantages of springs,\\nas compared to weights in safety-valves\\nA. Weights have the advantage that they do\\nnot change, which springs are liable to do when\\nin tension. On the other hand, weights could not\\nbe used on vessels or locomotives on account of\\nthe motion; the momentum which the weight\\nwould acquire would constantly alter the blowing-\\noff pressure. For these reasons weight safety-\\nvalves are mostly used in connection with station-\\nary boilers, while spring safety-valves are used\\nexclusively for marine and locomotive boilers.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0152.jp2"}, "153": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 131\\nQ. How are safety-valves set for a given blowing-\\noif pressure in the dead- weight and spring type\\nA. By simply adjusting the weight or the ten-\\nsion of the spring until it is equal to the blowing-\\noff pressure in pounds per square inch, times the\\narea of the valve in square inches.\\nQ. How do you calculate what weight should\\nbe placed on the end of a given lever safety-valve\\nfor a certain blowing-off pressure?\\nA. Multiply the area of the valve in square\\ninches by the blowing-off pressure in pounds per\\nsquare inch and the distance of the valve from\\nthe fulcrum in inches; multiply the weight of the\\nlever in pounds by the distance of its center of\\ngravity from the fulcrum in inches; multiply the\\nweight of the valve and steam in pounds by their\\ndistance from the fulcrum in inches; add the last\\ntwo products together, subtract their sum from\\nthe first product and divide the remainder by the\\ntotal length of the lever. The quotient will be\\nthe required weight in pounds.\\nQ. How do you calculate the distance of the\\nweight from the fulcrum for a given blowing-off\\npressure\\nA. Multiply the pressure by the area and the\\ndistance from the fulcrum from the valve; multi-\\nply the weight of the lever by the distance of its\\ncenter of gravity from the fulcrum; multiply the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0153.jp2"}, "154": {"fulltext": "132\\nroper s catechism for\\nweight of the valve and stem by their distance\\nfrom the fulcrum; add the last two products,\\ndeduct them from the first product, and divide\\nthe remainder by the weight of the ball. The\\nquantities being again taken in pounds and inches,\\nthe result will be the distance of the weight from\\nthe fulcrum in inches.\\nQ. How do you calculate the bloAving-off pres-\\nsure for a given position of the ball\\nA. Multiply the weight of the valve and stem\\nin pounds by their distance from the fulcrum.\\nMultiply the weight of the lever by the distance\\nof its center of gravity from the fulcrum. Multi-\\nply the weight of the ball by its distance from the\\nfulcrum. Multiply the area of the valve by its\\ndistance from the fulcrum. Divide the sum of\\nthe first three products by the last product. The", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0154.jp2"}, "155": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 133\\nquantities being all taken in pounds and inches,\\nthe result will be the pressure at which the valve\\nwill blow off in pounds per square inch.\\nQ. How can these three rules be expressed by\\nsimple formulse\\nA. If in the diagram on opposite page\\nW weight of ball in pounds,\\nw weight of valve and stem in pounds,\\nii\\\\ weight of lever in pounds,\\nl^ distance from fulcrum to valve in\\ninches,\\nZj distance from valve to ball in inches,\\nI distance from fulcrum to center of\\ngravity of lever in inches,\\np z= steam pressure in pounds per square\\ninch,\\na area of valve in square inches,\\nthen\\npal, 10 l^ u\\\\ I W -f g\\n_ p a [w I, IV, q\\na I,\\npal, IV I, IV, I\\nQ. How would you find the distance of the\\ncenter of gravity of a lever from the fulcrum", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0155.jp2"}, "156": {"fulltext": "134 ropee s catechism for\\nA. If the lever is of aniform cross-section, as in\\nthe diagram shown on page 132, the center of\\ngravity would be at its middle point; but if the\\nlever is taper, proceed according to the following\\nRule for finding the distance of the center of\\ngravity of taper levers from the fulcrum. To the\\nwidth of the small end of the lever add one-third\\nof the difference, in width, between the large and\\nthe small end of the lever. Multiply the sum by\\nthe length of the lever, and divide the product by\\nthe sum of the large and the small end of the\\nlever, all in inches. The quotient will be the re-\\nquired distance in inches.\\nQ. How would you express this in a formula\\nA. If we let\\na width of the large end in inches,\\nb width of the small end in inches,\\nI distance of center of gravity from\\nfulcrum in inches,\\nL total length of lever in inches,\\nthe formula is:\\n_ g 4- 2 5 L\\na 6 3\\nQ. With the aid of this rule and the one given\\non page 133, find the weight to be placed at the\\nend of the lever of a safety-valve under the fol-\\nlowing conditions", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0156.jp2"}, "157": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 135\\nwidth of large end of lever 3 inches,\\nwidth of small end of lever 2 inches,\\ntotal length of lever 30 inches,\\narea of valve 7 sq. inches,\\nweight of lever 9 pounds,\\nweight of valve and stem 6 inches,\\ndistance of valve stem from\\nfulcrum 3 inches,\\nblowing-off pressure 60 pounds.\\nA. By the rule for finding the distance of center\\nof gravity, we have\\n3 2x2^ 30\\nI g I 2 X -Q- 14 mches.\\nBy the rule for finding the weight of the ball,\\nwe have\\n60 X 7 X 3 [6 X 3 9 X 14]\\n30\\n37.2 pounds\\nfor the required weight to be placed at the end of\\nthe lever.\\nQ. Suppose this weight were moved back so\\nthat its distance from the fulcrum became 26\\ninches, at what pressure would the valve blow off\\nA. By the second formula,\\n6X3 9X14 37.2 X 26\\np =rz 1 x Z pounds.\\nQ. Where should- the weight be placed, so that\\nthe valve would blow off at a pressure of 45 pounds", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0157.jp2"}, "158": {"fulltext": "136 roper s catechism for\\nA. By the third formula,\\n45X7X3 6X3 9X14\\n^i-f^2\u00e2\u0080\u0094 37 2\\n21^ inches from fulcrum.\\nQ. How large should the area of safety-valves\\nbe made for different sizes of boilers\\nA. There are a great many rules governing the\\nareas of safety-valves. Some rules base it on the\\nheating surface, some on the grate surface, some\\non the coal consumption, some on the water\\nevaporated, and some on the heating surface and\\ngauge pressure. The rule given by Professor\\nThurston gives average values. It is as follows:\\nRule. Multiply the heating surface in sq. feet\\nby 5 and divide the product by 10 plus the gauge\\npressure in pounds per sq, inch. The quotient\\ndivided by 2 gives the proper area in square inches.\\nQ. How much steam should a safety-valve be\\ncapable of discharging?\\nA. About twice as much as that corresponding\\nto the rated capacity of the boiler, because when\\nthe boiler is forced to the utmost it is capable of\\ngenerating a much greater quantity of steam than\\nits rating calls for.\\nQ. Should a boiler have only one safety-valve?\\nA. No; it should have at least two, for each\\nboiler fired separately or for each set of boilers\\nplaced over one fire.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0158.jp2"}, "159": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n137\\nA TABLE FOE SAFETY-VALVES.\\nContaining the Cikcumfeeences and Aeeas of\\nCircles from of an inch to 4 inches.\\nDiameter.\\nCircumfer-\\neuce.\\nArea.\\nDiameter.\\nCirciinifei-\\neuce.\\nArea.\\ntV\\n.1963\\n.0030\\n2 ins.\\n6.2832\\n3.1416\\ni\\n.3927\\n.0122\\ntV\\n6.4795\\n3.3411\\nA\\n.5890\\n.0276\\ni\\n6.6759\\n3.5465\\ni\\n.7854\\n.0490\\nA\\n6.8722\\n3.7582\\nA\\n.9817\\n.0767\\ni\\n7.0686\\n3.9760\\nf\\n1.1781\\n.1104\\nT%\\n7.2649\\n4.2001\\nt\\\\\\n1.3744\\n.1503\\n1\\n7.4613\\n4.4302\\n1.5708\\n.1963\\n/f\\n7.6576\\n4.6664\\nt\\\\\\n1.7671\\n.2485\\n1\\n7.8540\\n4.9087\\n1\\n1.9635\\n.3068\\nfe\\n8.0503\\n5.1573\\nH\\n2.1598\\n.3712\\n8.2467\\n5.4119\\nf\\n2.3562\\n.4417\\nH\\n8.4430\\n5.6727\\nf\\n2.5525\\n.5185\\n1\\n8.6394\\n5.9395\\n2.7489\\n.6013\\nif\\n8.8357\\n6.2126\\nif\\n2.9452\\n.6903\\ni\\n9.0321\\n6.4918\\n11\\n9.2284\\n6.7772\\nlin.\\n3.1416\\n.7854\\nt\\n3.3379\\n.8861\\n3 ms.\\n9.4248\\n7.0686\\n3.5343\\n.9940\\ntV\\n9.6211\\n7.3662\\ntV\\n3.7306\\n1.1075\\n9.8175\\n7.6699\\n\u00e2\u0080\u00a2i\\n3.9270\\n1.2271\\nA\\n10.0138\\n7.9798\\ntV\\n4.1233\\n1.3529\\nI\\n10.2102\\n8.2957\\n1\\n4.3197\\n1.4848\\nT%\\n10.4065\\n8.6179\\ntV\\n4.5160\\n1.6229\\nf\\n10.6029\\n8.9462\\n4.7124\\n1.7671\\ntV\\n10.7992\\n9.2806\\nA\\n4.9087\\n1.9175\\ni\\n10.9956\\n9.6211\\n1\\n5.1051\\n2.0739\\nA\\n11.1919\\n9.9678\\nH\\n5.3015\\n2.2365\\n1\\n11.3883\\n10.3206\\nf\\n5.4978\\n2.4052\\nil\\n11.5846-\\n10.6796\\nf\\n5.6941\\n2.5801\\ni\\n11.7810\\n11.0446\\n5.8905\\n2.7611\\nf\\n11.9773\\n11.4159\\nH\\n6.0868\\n2.9483\\n12.1737\\n11.7932\\nif\\n12.3700\\n12.1768\\n4 ins.\\n12^.5664\\n12.5654", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0159.jp2"}, "160": {"fulltext": "138 roper s catechism for\\nGAUGES.\\nQ. What is meant by a gauge\\nA, A gauge is any instrument or device used\\nfor measuring.\\nQ. What are the princijDal gauges used in con-\\nnection with steam boilers\\nA, The steam pressure gauge, vacuum gauge^\\nwater gauge, sahnometer, and econometer.\\nQ. Describe the steam gauge.\\nA. There are two kinds: those which merely\\nindicate the pressure and those which make a\\npermanent record of it. Both are usually con-\\nstructed on the principle invented by Bourdon,\\nand consist of a thin tube of elliptical cross-sec-\\ntion, bent into a curved shape. The steam whose\\npressure is to be measured is admitted into the\\ntube and tends to make the cross-section circular.\\nThis tendency causes the tube to straighten itself\\nout partially, and the instrument is so constructed\\nwith a pointer and gearing that the straightening\\nof the tube moves the pointer which indicates the\\npressure within on a suitable dial. The recording\\ngauge has, in addition, a clock which moves the\\ndial, giving it one revolution in 24 hours, so that\\nby the aid of a pen or stylus filled with ink a\\ncomplete record of the pressure carried during this\\ntime can be had.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0160.jp2"}, "161": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 139\\nQ. Do steam gauges register absolute pressure\\nA. No; they are usually constructed to indicate\\npressure above the atmosphere that is, at atmos-\\npheric pressure (14.7 pounds per square inch) the\\npointer stands at zero.\\nQ. What precautions should be taken in using\\npressure gauges\\nA. The pointer should always stand at zero\\nwhen there is no pressure in the boiler. If it\\ndoes not, it should be adjusted. Even after this\\nis done, the readings at other pressures may be\\nincorrect and its readings should be checked from\\ntime to time by comparing with a standard gauge\\nwhich is known to be correct.\\nQ. What is a vacuum gauge\\nA. It is made in the same way as a pressure\\ngauge, but it is arranged to read pressures below\\nthe atmosphere instead of above.\\nQ. How are vacuum gauges calibrated\\nA. They are usually calibrated in inches of\\nmercury instead of pounds, that is to say, the\\nreadings indicate to how many inches the vacuum\\nwould allow a column of mercury to rise under\\natmospheric pressure. Each inch of mercury\\ncorresponds roughly to a vacuum of about half a\\npound, so that a reading of 20 on a vacuum\\ngauge would mean that the pressure is about 10\\npounds below that of the atmosphere.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0161.jp2"}, "162": {"fulltext": "140 roper s catechism for\\nQ. Why are they calibrated in this way and not\\nin absolute pressures\\nA. Because the mechanism which operates the\\ngauge depends for its action upon the difference in\\npressure of the atmosphere and vacuum chamber;\\nhence, as the pressure of the atmosphere varies,\\nthe gauge would not be accurate if calibrated in\\npounds absolute pressure.\\nQ. What is a water gauge\\nA. It is a device for indicating the level of the\\nwater in the boiler. It usually consists of a plain\\nglass tube placed on the outside of the boiler, and\\nconnected at the top to the steam- and at the bot-\\ntom to the water-space.\\nQ. What is a safety water column\\nA. It is a modification of a glass water gauge,\\nwith floats so arranged that a signal is given both\\nwhen the water is too high and when it is too low.\\nQ. Do you consider the use of safety water\\ncolumns advisable?\\nA. The}^ are very useful where an engineer or\\nfireman has other duties to perform besides attend-,\\ning to the boiler; but it is a mistake for engineers\\nto neglect watching the water-level on account of\\nthis device becau-se it may get out of order.\\nThere can be nothing so dangerous in running\\nboilers as neglecting the water. In some instances\\nwhere these safety water columns were used, the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0162.jp2"}, "163": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 141\\nfiremen have been known to systematically fall\\nasleep and depend on the alarm in the safety water\\ncolumn to awaken them at the proper time.\\nQ. Is the glass gauge the only device used for\\nindicating the water-level\\nA. No every boiler should, in addition, be\\nfitted with gauge cocks placed at different levels.\\nThese are partly for the purpose of checking up\\nthe glass gauge and partly for use in case the\\ngauge glass should break, which is not an infre-\\nquent occurrence.\\nQ. What is the salinometer\\nA. It is an instrument or gauge used for indi-\\ncating the quantity of salt contained in the water\\nof marine boilers.\\nQ. What is the econometer\\nA. It is an instrument or gauge used for indi-\\ncating, continuously and automatically, the quan-\\ntity of carbonic acid contained in the products of\\ncombustion.\\nQ. How much carbonic acid should they con-\\ntain?\\nA. As much as possible.\\nQ. How can this be attained\\nA. By supplying enough air to the furnace for\\na complete combustion of the fuel, but not much\\nin excess of that amount.\\nQ. What is the result if too much air is supplied", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0163.jp2"}, "164": {"fulltext": "142\\nROPER S CATECHISM FOR\\nA. A portion of the heat of combustion is con-\\nsumed in raising the temperature of the excess of\\nair and consequently wasted. The following table\\nshows the amount of wasted fuel for different per-\\ncentages of carbonic acid in the flue gases:\\nTABLE\\nSHOWING WASTE OF FUEL DUE TO EXCESSIVE SUPPLY\\nOF AIR.\\n(coal of medium quality.)\\nPercentage carbonic acid\\nin flue gases,\\n2\\n4\\n6\\n8\\n10\\n12\\n14\\nNo. of times the quan-\\ntity of air required for\\ncomplete combustion,\\n9.5\\n4.7\\n3.2\\n2.4\\n1.9\\nL6\\n1.4\\nPercentage waste of fuel\\nat420OFahr.,\\n90\\n45\\n30\\n23\\n18\\n15\\n13\\nPUMPS AND INJECTORS.\\nQ. What is a pump\\nA. It is a device for lifting, forcing, or transfer-\\nring water or other liquids.\\nQ. How are pumps usually operated\\nA. (a) By belting or gearing from some power\\nshaft, called power pumps.\\n(6) By the direct connection to a steam\\ncylinder equipped with suitable valve", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0164.jp2"}, "165": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 143\\ngear for the distribution! of the steam,\\ncalled steam pumps,\\n(c) By direct connection or gearing to an\\nelectric motor these are called electric\\npumps.\\nQ. Which of the above types is usually adopted\\nfor feeding boilers\\nA. The steam pump.\\nQ. What different kinds of steam pumps are\\nthere\\nA. (a) Fly-wheel pumps those in which the re-\\nciprocating motion of the steam piston\\nis first converted into rotary motion\\nby means of a crank shaft, with a fly-\\nwheel to help it over the dead cen-\\nters, and then re-converted by another\\ncrank and rods into reciprocating mo-\\ntion for the water cylinder.\\n(6) Direct-acting pumps those in which the\\nwater piston or plunger is mounted-\\non the same rod as the steam piston\\nand the power transmitted from the\\nlatter to the former, direct and with-\\nout the intervention of a crank shaft\\nand fly-wheel. In this type an auxil-\\niary valve gear is required in addition\\nto the main valve gear, to help the\\nmachine over its dead points.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0165.jp2"}, "166": {"fulltext": "144 roper s catechism for\\n(c) Duplex pumps consisting of a combina-\\ntion of two pumps so coupled together\\nthat the steam-valve of the one is\\noperated by the piston of the other,\\nand vice versa.\\nQ. Which of these is most commonly used as a\\nboiler-feed pump Why\\nA. The duplex pump, because it is the simplest.\\nQ. W^hat is the difference between a force pump\\nand a suction pump\\nA. A force pump is one in which the energy is\\nexpended in forcing the water against some oppos-\\ning pressure, such as that in the boiler. A suction\\npump is one which takes the water from a lower\\nlevel than that of the pump, as, for example, a\\npump placed at the top of a well.\\nQ. Is there any limit beyond which water can-,\\nnot be lifted by a suction pump Give reasons.\\nA. Yes; water cannot be lifted by a suction\\npump over 33 feet vertically, and it will deliver\\nwater slowly only, at this height. The reason for\\nthis is that the pump does not actually lift the\\nwater, but merely creates a vacuum in the water\\ncylinder, and the water is lifted by the atmospheric\\npressure on its surface. The atmospheric pressure\\nwill support a column of water about 33 feet in\\nheight, hence this is the limit beyond which water\\ncannot be raised by a suction pump. If the pump", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0166.jp2"}, "167": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 145\\nand the piping is tight, however, it will draw\\nwater horizontally almost any distance.\\nQ. Is there any limit in the height to which a\\npiimp will force water\\nA. None; except the power of the pump.\\nQ. How do you calculate the power required to\\npump water\\nA. Multiply the number of pounds of water to\\nbe pumped per minute by the vertical distance, in\\nfeet, between the levels of the supply and dis-\\ncharge, and divide the product by 33,000; the\\nresult will be the theoretical horse-power. To\\nthis must be added the losses in friction corre-\\nsponding to the velocity of the water (see page 63).\\nIf instead of pumping the w^ater to a higher level\\nit is required to force it against a pressure, multi-\\nply by 2J times the pressure instead of the\\nheight, making the same correction for losses as\\nabove.\\nQ. How do 3^ou determine the capacity of boiler-\\nfeed pumps\\nA. Calculate the amount of water which the\\nboiler is capable of evaporating under normal\\nconditions by multiplying the horse-power of the\\nboiler by 30. This will give the number of pounds\\nof water it will evaporate per hour. Divide this\\nby 8.35, which will give the number of gallons.\\nThe pump should be capable of supplying about\\n10", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0167.jp2"}, "168": {"fulltext": "146 roper s catechism for\\ndouble this quantity, so that it will be adequate\\nwhen the boiler is forced.\\nQ. When the water is hot, what precautions\\nmust be taken with the pump\\nA. It should be brass-lined so that it will not\\ncorrode, and it must be placed below the level of\\nthe water-supply, as otherwise the hot water will\\nnot follow the plunger. It is also advisable to\\nplace a valve between the supply and the pump,\\nso that any accumulated vapor may be liberated.\\nQ. What is an injector?\\nA. It is an apparatus for forcing water against\\na pressure by the direct action of a jet of steam\\nupon a mass of water.\\nQ. Briefly describe the injector and its action.\\nA. It consists of a steam nozzle through which\\nenters the steam used a water-supply tube\\nthrough which enters the water to be forced a\\ncombining tube which begins at the end of the\\nsteam nozzle, being that part of the apparatus\\nwhere the steam and water first come in contact;\\nand, finally, a delivery tube from which the mix-\\nture of steam and water enters the discharge pipe.\\nAll of these parts have peculiar shapes, which\\nhave been determined by years of experimenting;\\nthe object being to give the steam and water the\\nproper velocities at different stages in the process.\\nThe action of the apparatus may be explained as\\n1", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0168.jp2"}, "169": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 147\\nINJECTOR.\\nS, Steam nozzle.\\nB, Spinale for adjusting supply of\\nC, Combining tube.\\nZ Delivery tube.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0169.jp2"}, "170": {"fulltext": "148 roper s catechism for\\nfollows The steam leaves the nozzle and enters\\nthe combining tube at a high velocity. The\\nfriction between the steam jet and the air in the\\nwater-supply pipe causes the latter to be exhausted\\nand consequently the water being relieved of the\\npressure upon its surface soon rises and enters the\\ncombining tube, where it comes in contact with\\nthe steam jet and condenses it. In being con-\\ndensed the cross-section of the steam jet is greatly\\nreduced, and the entire energy of its velocity is\\nconcentrated upon a very thin jet. This energy\\nbeing more than sufficient to force it into the\\nboiler, some of it is imparted to the water which\\nit meets in the combining tube, and the entire\\nmixture of steam and water is carried into the\\ndelivery tube and thence into the boiler by virtue\\nof the momentum which it has acquired. Of\\ncourse, the apparatus must be carefully propor-\\ntioned, since if there is too much water the\\nenergy of the condensed steam will not be suf-\\nficient to carry it into the boiler, while if there\\nis too little, the steam will not be condensed.\\nQ. What are the advantages of injectors over\\npumps\\nA. The principal advantages are that water\\nenters the boiler in a steady stream; practically\\nnone of the energy of the steam used to operate\\nit is wasted, as all the energy in excess of that", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0170.jp2"}, "171": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 149\\nnecessary to force the water into the boiler is\\nutilized in raising its temperature; the water does\\nnot enter the boiler cold it is more compact and\\nhas no moving parts.\\nQ. What is the commonest cause of the failure\\nof injectors to operate\\nA. The presence of air in the suction pipe.\\nThis must be avoided by properly packing the\\nvalve stem and by entirely submerging the end of\\nthe suction pipe. Sediment or dirt in the nozzles\\nwill also interfere with the proper working of the\\napparatus. They should be carefully cleaned out\\nif this occurs.\\nQ. If the injector does not get water, where\\nwould you look for the trouble\\nA. It would probably be due to one of the fol-\\nlowing causes: a leak in the supply pipe, clogging\\nup of the strainer, too hot water, too low a steam\\npressure for the required lift, or the water-supply\\nmay be cut off. I should examine the water pipe\\nfirst to see that it was intact.\\nQ. If the injector starts, but afterward the jet\\nbreaks, where would you expect to find the\\ndifficulty\\nA. Any of the causes given in the preceding\\nanswer might produce this result, or the trouble\\nmight be caused by a loose disc in the valve in the\\nsupply pipe, causing it to partly close. In the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0171.jp2"}, "172": {"fulltext": "150 roper s catechism for\\nlatter case, the trouble could be remedied by-\\nreversing the valve.\\nQ. What is the difference between lifting and\\nnon-lifting injectors?\\nA. In the former there is a partial vacuum\\nformed in the feed pipe on starting, in the latter\\na pressure is required in the water-supply.\\nQ. What are the principal points to be observed\\nin setting up injectors\\nA. All pipes, whether steam, water-supply, or\\ndelivery, must be of the same or greater internal\\ndiameter than the hole in the corresponding branch\\nof each injector, and as short and straight as\\npracticable. When floating particles of wood or\\nother matter are liable to be in the supply water,\\na strainer must be placed over the receiving end of\\nthe water-supply pipe. The holes in this strainer\\nmust be as small as the smallest opening in the\\ndelivery tube, and the total area of all the holes\\nmust be much greater than the area of the water-\\nsupply pipe, to compensate for the closing of some\\nof them by deposits. The steam should be taken\\nfrom the highest part of the boiler, to avoid the\\ncarrying over of water with the steam. Dry\\npipes should always be used on locomotives to\\ninsure dry steam; wet steam cuts and grooves the\\nsteam spindle and steam nozzle. The steam should\\nnot be taken from the steam pipe leading to an", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0172.jp2"}, "173": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 151\\nengine, unless such pipe is large. Sudden varia-\\ntions in pressure may break the jet. After all the\\npipes are properly connected to the injector and to\\nthe boiler, and before steam and water are admitted\\nthrough them to the injector, they should be dis-\\nconnected and well washed out by blowing steam\\nor running water through them, to wash out all\\nred lead, scale, or other solids that may be in the\\npipes. Finally, in setting injectors it is important\\nto place them as low as possible, since their\\ncapacity is reduced and the promptness and relia-\\nbility of their action diminished as the height of\\nlift is increased.\\nQ. What is an inspirator\\nA. It is a double-jet injector that is, one con-\\ntaining two sets of jets, of which one is used for\\nlifting the water from the source of supply and\\nthe other for forcing it into the boiler.\\nQ. What is an ejector?\\nA. It is an instrument similar to the injector,\\nbut designed for lifting water only, without forcing\\nit against a pressure.\\nQ, Is an injector more economical than a pump\\nas a boiler feeder\\nA. Not always; the injector is the more eco-\\nnomical of the two when the feed-water is cold,\\nbut the pump is the more economical when the\\nfeed-water has been heated.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0173.jp2"}, "174": {"fulltext": "152\\nROPER S CATECHISM FOR\\nTABLE*\\nSHOWING THE EELATIVE EFFICIENCIES OF PUMPS\\nAND INJECTORS.\\nMethod of Supplying Feed-\\nWater TO Boiler.\\nTemperature of feed-water as deliT-\\nered to the pump or to the injector,\\n60\u00c2\u00b0 Fahr. Rate of evaporation of\\nboiler, lOpounds of water per pound\\nof coal from and at 212\u00c2\u00b0 Fahr.\\nRelative amount\\n\u00e2\u0080\u00a2of coal required\\nper unit of time,\\nthe amount for a\\ndirect-acting\\npump, feeding\\nwater at 60\u00c2\u00b0, with-\\nout a heater, being\\ntaken as unity.\\nSaving of fuel\\nover the amount\\nrequired when\\nthe boiler is fed\\nby a direct-\\nacting pump\\nwithout heater.\\nDirect-acting pump, feeding\\nwater at 60\u00c2\u00b0, without a\\nheater,\\n1.000\\n.985\\n.0\\nInjector feeding water at 150\u00c2\u00b0,\\nwithout a heater,\\n1.5 per ct.\\nInjector feeding through a\\nheater in which the water\\nis heated from 150 to 200\u00c2\u00b0,\\n.938\\n6.2\\nDirect-acting pump feeding\\nwater through a heater, in\\nwhich it is heated from 60\\nto 200\u00c2\u00b0,\\n.879\\n12.1\\nGeared pump, ran from the\\nengine, feeding water\\nthrough a heater, in which\\nit is heated from 60 to 200\u00c2\u00b0,\\n.868\\n13.2\\nComputed by Professor D. S. Jacobus.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0174.jp2"}, "175": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 153\\nQ. Should a boiler plant have both a pump and\\nan injector?\\nA. Yes, whenever possible; because either the\\none or the other may at some time refuse to\\noperate. In some cases it would be better to have\\ntwo pumps, and in others two injectors. (See\\ntable on opposite page.\\nQ. With what kind of boilers are injectors used\\nthe most Why\\nA. AVith locomotives, because they use cold\\nwater, and therefore an injector is more efficient;\\nalso because the jarring motion of the engine does\\nnot affect an injector in the least, while its effect\\non the pump would be detrimental. An injector\\nis also much lighter than a pump.\\nHEATING FEED-WATER.\\nQ. Why should the feed-water be heated before\\nit enters the boiler?\\nA. Because cold water fed into a boiler under\\nsteam produces strains that will shorten the life of\\nthe boiler; because a large proportion of the solid\\nmatter frequently contained in water will separate\\nout at a high temperature, and, consequently, if\\nthe feed-water is heated sufficiently solids will\\nbe deposited in the heater that would otherwise\\nproduce scale in the boiler; and because by using\\nexhaust steam, or some other source of heat which", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0175.jp2"}, "176": {"fulltext": "154\\nroper s catechism for\\n0^\\nr\\nro\\no\\nOS\\n00\\nc^\\nt^\\nM\\ns\\n\u00c2\u00a75\\n?5\\ns\\nS\\ns\\n\u00c2\u00a75\\n\u00c2\u00a75\\na^\\n_^_\\no\\nn\\nni\\nc5\\nOi\\ns\\ns\\nS\\nto\\nJ2\\nUi\\nTf\\nCO\\nCO\\n2\\no\\ns\\nTt\\ns\\ng\\ns\\nS\\ns\\n\u00c2\u00a78\\n|0\\nT}\\ncc\\nCO\\nS2\\nS\\nlO\\nrh\\nin\\nfn\\nr-1\\n-f\\nin\\nj^\\nrf)\\nro\\nm\\nCO\\nOS\\nt-\\nt-\\nJ2\\n2\\ns\\ns\\nc^\\nS\\nO\\ns\\na\\nOS\\nm\\n\u00c2\u00abo\\ntn\\no\\nIC\\no\\nm\\nnn\\no\\ns\\nJ2\\no\\no\\n9i\\n05\\nOS\\nTl*\\n05\\niro\\nO\\nf^\\nm\\nrr,\\nrr\\\\\\nto\\n05\\nlO\\no\\no\\nC5\\nOS\\noi\\n00\\no\\nOO\\nr-1\\nin\\nf^\\nm\\nm\\nm\\no\\no\\nto\\no\\nto\\nS2\\no\\ns\\ns\\nCT.\\no\\n00\\nl\\n(M\\nto\\nCO\\n05\\no\\no\\no\\no\\n05\\nen\\nt^\\nlO\\nt^\\nori\\non\\n1^\\nJ\\nto\\nto\\no\\nto\\nlO\\nQ\\n-^1\\n-1*\\ni2\\n00\\no\\no\\nto\\nc^\\n05\\nlO\\n05\\nS5\\n05\\nt^\\nt-\\nt^\\no\\nin\\nm\\n(M\\no\\n40\\no\\nto\\nCO\\n00\\n00\\nt^\\nto\\nto\\nto\\nlO\\nIC\\nTfi\\nni\\nT(i\\nCO\\nQ\\nm\\nin\\ns\\no\\no\\nCO\\nt^\\nto\\nto\\nw\\nw\\nTti\\nCO\\nCO\\nN\\no\\ns\\nto\\nOS\\nt^\\nvi\\n\u00c2\u00abd\\nto\\nifl\\nIC\\nTti\\n\u00c2\u00abo\\nCO\\nCO\\nc i\\n(N\\nP\\nin\\nm\\ng\\nin\\nrr\\no\\nen\\nt^\\nlO\\nIC\\nic\\nT)\\nCO\\nCO\\nCO\\nIM\\no\\nQ\\n^l\\nm\\nlO\\n05\\nto\\no\\nm\\nlO\\nt-\\nTf\\nlO\\nIrt\\n00\\nCO\\nN\\nO\\no\\n1\\nS H\\nV.\\no\\ng\\ntu\\nto\\nOJ\\nUJ\\nh5", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0176.jp2"}, "177": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 155\\nwould otherwise be wasted, a very material\\neconomy is effected in the consumption of fuel.\\nA pound of feed water entering a steam\\nboiler at a temperature of 50\u00c2\u00b0 Fahr., and evapo-\\nrating into steam of 60 pounds pressure, requires\\nas much heat as would raise 1157 pounds of water\\n1 degree. A pound of feed- water raised from 50\u00c2\u00b0\\nFahr. to 220\u00c2\u00b0 Fahr. requires 170 units of heat;\\nwhich, if absorbed from exhaust- steam passing\\nthrough a heater, would be a saving of 15 per\\ncent, in fuel. Feed-water at a temperature of\\n200\u00c2\u00b0 Fahr., entering a boiler, as compared in\\npoint of econoni}^ with feed-water at 50\u00c2\u00b0 Fahr.,\\nwould effect a saving of over 13 per cent, in fuel;\\nand with a well-constructed heater there ought to\\nbe no trouble in raising the feed-water to a tem-\\nperature of 212\u00c2\u00b0 Fahr.\\nQ. What is the difference between open and\\nclosed feed-water heaters\\nA. In closed heaters the exhaust steam passes\\nthrough a series of brass tubes and the water is\\npumped through the space around the tubes into\\nthe boiler, or the water may be jjumped through\\nthe tubes and the steam pass around the tubes.\\nIn the open type, the steam comes in actual\\ncontact with the water, the latter passing over a\\nseries of cast-iron or steel pans placed in a chamber\\nthrough which the exhaust steam passes.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0177.jp2"}, "178": {"fulltext": "156\\nroper s catechism for\\ng M .S o\\nS 2", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0178.jp2"}, "179": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n157\\nOPEN HEATER,\u00e2\u0080\u0094 PITTSBURGH TYPE.\\n(Steam enters below the pans at the left and passes out at the top.\\nWater enters through the pipe at the top, the flow being regulated by a\\ncock which is controlled by the float and rod. The small cylinder at the\\nright separates the oil. [See also page 172.] The connection to the pump\\nis near the top of the small cylinder. Through an opening in the side\\nof the shell the pans, which rotate around a central shaft, may be\\ncleaned. Shell and pans of steel.)", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0179.jp2"}, "180": {"fulltext": "158 ropek s catechism for\\nQ. What is the difference in the method of\\ninstalling open and closed heaters\\nA. In open heaters the pump is placed between\\nthe heater and the boiler, hence the pump takes\\nhot water and must therefore be placed below the\\nlevel of the water in the heater, otherwise the\\nwater will not follow the plunger. With the closed\\ntype the water enters the pump cold and is forced\\nthrough the heater into the boiler.\\nQ. Why can open heaters not be used with\\ninjectors\\nA. Because if the water is heated to a high tem-\\nperature, as it should be, in the heater, the injec-\\ntor will not work, it requiring moderately cold\\nwater to condense the steam in the combining\\ntube. If the steam in an injector is not con-\\ndensed the apparatus will refuse to force the water\\ninto the boiler.\\nQ. Which type is, in general, preferable the\\nopen or the closed\\nA. Each has its advantages and disadvantages.\\nThe closed heater may be located in any conve-\\nnient position relative to the pump, while the open\\ntype must be placed at a higher level than the\\npump, which, as already stated, has to pump hot\\nwater; the open type is not under pressure (except\\nthat of the exhaust steam), hence it is lighter and\\ncheaper. It is more easily cleaned; it heats the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0180.jp2"}, "181": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 159\\nwater to a higher temperature; its purifying prop-\\nerties are better, and it produces no back pressure\\non the engine. On the other hand, the feed-water\\nmay contain grease which will injure the boiler,\\nalthough it is claimed that by a suitable oil\\nseparator this may be entirely eliminated.\\nQ. What is an economizer\\nA. It is a device used for heating the feed-water\\nby means of the products of combustion of the\\nboiler furnace as they pass into the stack.\\nQ. How is it constructed\\nA. The economizer usually consists of a series\\nof cast-iron or steel tubes connected at either end\\nby headers similar to those used in water-tube\\nboilers. The water circulates through the tubes,\\nwhich are placed in the flue connection just at the\\nentrance to the stack.\\nQ. What fittings should an economizer have\\nA. As it is virtually a water-tube boiler, it\\nshould have a blow-off pipe and a safety-valve,\\nbecause if the boiler is not supplying steam as\\nusual the water in the economizer tubes will be\\nevaporated, producing an excessive pressure.\\nQ. For what purpose are economizers generally\\nused\\nA. For the purpose of increasing the capacity\\nor efficiency of existing boiler plants.\\nQ. Why are they generally not necessary in new\\ninstallations", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0181.jp2"}, "182": {"fulltext": "160 roper s catechism for\\nA. Because if the boilers are properly con-\\nstructed they do not allow much heat to be wasted\\nthrough the chimney.\\nQ. What other method of heating the feed-\\nwater is sometimes used\\nA. It is heated by the use of condensers in\\nconnection with the engines. (See Condensers,\\npage 233.)\\nFURNACES AND FLUES.\\nQ. Can you calculate the strength of a flue by\\nthe same rules that apply to the shells of boilers\\nA. No; because the same rules for strength\\nof cylinders under pressure from within do not\\napply to those which are subjected to a pressure\\nfrom without.\\nQ. If pressure is exerted on the internal or\\nexternal surface of the cylinder, is the effect not\\nthe same in both cases\\nA. No; when pressure is exerted within a tube\\nor cylinder, the tendency of the strain is to cause\\nthe tube to assume the true cylindrical form; but\\nwhen pressure is exerted on the outside of the\\ntube, the tendency of that pressure is to crush the\\ntube or flatten it; as it is a well-known fact that\\niron of any strength when formed into a tube will\\nrequire a much greater strain to tear it asunder\\nthan it would take to crush it. A thin hoop of", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0182.jp2"}, "183": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 161\\niron will resist a very great amount of tearing\\nforce, but if that same hoop or circle be placed as\\na prop under half the weight that was exerted to\\ntear it apart, it would be crushed flat.\\nQ, What is the difference between external and\\ninternal strain?\\nA. Internal is a tearing strain, while external\\nis a crushing strain; and flues and tubes of boilers\\nare nothing but a series of props, and a constant\\ntendency of the pressure is to flatten the tube or\\nflue and cause it to collapse.\\nQ. What is a collapse\\nA. It is the crushing or flattening of a flue by\\noverpressure, and is often attended with terrible\\nresults.\\nQ. How do you calculate the strength of flues\\nor cylinders subjected to external pressure?\\nA. It has been shown by experiment that the\\nstrength of such cylinders is proportional to the\\nsquare of the thickness of the cylinder and in-,\\nversely proportional to the length and to the\\ndiameter. The formula for collapsing is:\\nP= 806,000^,\\nla\\nwhere P is the collapsing pressure in pounds per\\nsquare inch,\\nI is the length of the cylinder in feet,\\nd is the diameter of the cylinder in inches.\\n11", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0183.jp2"}, "184": {"fulltext": "162 roper s catechism for\\nRule for Finding the Collapsing Pressure\\nOF A Cylindrical Flue.- Multiply the square of\\nthe thickness in inches by the number 80,600.\\nMultiply the length of the flue in feet by its\\ndiameter in inches. Divide the first product by\\nthe second, and the quotient will be the collaps-\\ning pressure in pounds per square inch.\\nQ. If the length of a cylindrical flue is 10 feet,\\nits diameter 2 feet, and thickness J inch, what\\nwill be the collapsing pressure\\nP ^0^ 7^X|X^ 215 pounds.\\nQ. How may long flues be strengthened\\nA. This may be done in various ways. The\\nold method was to rivet rings of angle- or tee-iron\\naround the flue at fixed intervals, or to make the\\nflue in sections and to join them together b}^ rivet-\\ning on _f\\\\-shaped rings. The modern method is\\nto make the entire flue of corrugated iron, which\\nnot only adds strength, but facilitates expansion\\nand increases the heating surface.\\nQ. When the flue is stiffened by rings, as de-\\nscribed above, how do you calculate its strength\\nA. By the same rule as that for plain flues,\\nexcept that the length between rings is taken as\\nthe length of the flue.\\nQ. What method is employed in the Galloway\\nboiler for strengthening the flues", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0184.jp2"}, "185": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 163\\nA. The Galloway tubes, which are conical in\\nform and placed within and across the flues, being\\nriveted to the sides.\\nGRATES.\\nQ. What is the simplest form of grate\\nA. It consists of a series of cast-iron bars\\nshaped like beams, supported at either end, and\\nso placed as to allow spaces between them for the\\npassage of air.\\nQ. What points should, in general, be observed\\nin grates\\nA. They should be flat on top and supported,\\nbut not fixed at the ends, as otherwise the expan-\\nsion and contraction will cause them to get out of\\nshape. The spaces between the bars should be\\nnumerous and as large as possible. The width of\\nthe spaces, however, depends on the kind of coal\\nto be used, and in practice varies from f to f inch.\\nThe height of the grate above the bottom of the\\nashpit should be from 24 to 30 inches, and the\\nbars should, in general, be inclined downward to-\\nward the bridge wall, as the fuel may then be\\nmore easily distributed. The length is limited by\\nthe distance to which a fireman can throw the\\ncoal, which is about 6 feet.\\nQ. How much coal is generally consumed per\\nsquare foot of grate surface", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0185.jp2"}, "186": {"fulltext": "164 roper s catechism for\\nA. This depends on the nature of the draught\\nand the kind of coal. For land boilers fired with\\na good quality of anthracite coal, 9 pounds per\\nsquare foot is a fair average. In some boilers\\noperating under a light draught the coal con\\nsumption is as low as 4 pounds, while in locomo-\\ntives using a blast pipe to produce a stron^\\ndraught as high as 120 pounds of coal may be\\nburned per square foot of grate surface per hour\\nQ. How much grate surface should be alloweu\\nper horse-power\\nA. In land boilers about J square foot of grat^\\nsurface is given per horse-power. With good biti^\\nminous coal, better results are obtained by usin\\na smaller grate area and a strong draught. Wit.^\\ncoal containing a high percentage of ash it i-^\\nbetter to use a large grate surface with a compara-\\ntively slow rate of combustion.\\nQ. What is a shaking grate\\nA. It is a grate designed for cleaning the fire\\nbreaking up clinkers, and removing them withou\\nopening the fire door.\\nQ. What are the advantages to be derived from\\nsuch an arrangemxcnt?\\nA. Whenever the fire doors are opened cold air\\nrushes in, tending not only to impair the efficiency\\nof the boiler, but also its durability. Moreover,\\nit is impossible for a fireman to thoroughly stir", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0186.jp2"}, "187": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 165\\nout, with a slicing-bar, every part of the grate.\\nHence, if the coal has a tendency to form cUnkers\\nthe advantages of a shaking grate would be\\nmaterial.\\nQ. AVhat is meant by automatic stoking\\nA. A system by Which the coal is fed to, and\\nthe ashes removed from, the furnace automatically\\nwithout opening the furnace doors.\\nQ. How long have automatic or mechanical\\nstoking devices been in use\\nA. A device similar in many respects to the\\nmodern mechanical stokers was employed by\\nWatt in 1785.\\nQ. Under what conditions are mechanical\\nstokers especially desirable?\\nA. When the fuel used consists of mine refuse,\\nscreenings, or other materials not generally used\\nin manual firing.\\nQ. What advantages are claimed for mechanical\\nstokers\\nA. Fuel economy, prevention of smoke, saving\\n*fin labor, and cleanliness in the boiler room.\\nQ. Why is mechanical stoking productive of\\neconomy in the use of fuel?\\nA. Because the coal is spread upon the grate\\nuniformly and at the time when it is needed.\\nWith hand-firing the coal is fed to the furnace at\\nirregular intervals, and usually more coal is put", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0187.jp2"}, "188": {"fulltext": "166 koper s catechism for\\non than necessary. Besides, each time the boiler\\nis fired and cleaned, the furnace doors are opened\\nand cold air rushes in. All of these features\\nwhich attend hand-firing are injurious to the\\neconomy of operation. With a system of mechan-\\nical stoking they are not inciirred, and hence the\\nefficiency may be materially increased.\\nQ. Why do mechanical stokers lessen the pro-\\nduction of smoke?\\nA. Because the fuel is fed uniformly in small\\nquantities instead of intermittently and in bulk,\\nas in the case of hand-firing. A uniform tem-\\nperature is maintained in the furnace, and the\\nmotion of the grate keeps the spaces open for the\\ncontinual passage of the air. Hence the combus-\\ntion is at all times complete, which means absence\\nof smoke.\\nQ. Why are they productive of saving in labor\\nA. Because there is no cleaning of fires or\\nmanual labor of any kind, except, perhaps, the\\nbringing of the coal to the hoppers; and even this\\nis frequently accomplished by machinery.\\nQ. Why are they more cleanly\\nA. Because the usual dirty appearance of boiler\\nplants is produced by the dust raised in shoveling\\nthe coal, cleaning the fires, and removing the\\nashes, all of which operations are abolished in\\nmechanical stoking.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0188.jp2"}, "189": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 167\\nQ. Do mechanical stokers pay in small plants\\nA. No, they do not; because the cost of the\\nplant and the power consumed in operating would\\nnot be warranted by the saving which w^ould\\naccrue.\\nCHIMNEYS AND STACKS.\\nQ. What is the object of a chimney or stack?\\nA. It is for the purpose of producing a draught,\\nejecting the products of combustion, and supply-\\ning fresh air for the combustion of the fuel.\\nQ. How does a chimney produce a draught\\nA. The tendency of the rarefied gases is to rise,\\nproducing a partial vacuum which causes a rush\\nof air through the furnace.\\nQ. Which kinds of coal require the tallest\\nstacks\\nA. Anthracites, because they do not burn as\\nreadily as bituminous coals.\\nQ. On what does the draught produced by a\\nchimney depend?\\nA. It depends on two factors: on the height of\\nthe chimney and on the difference in weight of\\nthe gases contained in the chimney and the atmos-\\nphere.\\nQ. On what does this difference in weight\\nlargely depend?\\nA. Upon the temperature of the gases leaving\\nthe boiler.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0189.jp2"}, "190": {"fulltext": "168 roper s catechism for\\nQ. At what temperature do the gases usually\\nleave in well-designed boilers\\nA. 500 to 600 degrees Fahrenheit.\\nQ. At what temperature of the escaping gases\\nis the best draught obtained\\nA. At about 580 degrees Fahrenheit.\\nQ. On what does the area of the chimney for a\\ngiven boiler plant depend\\nA. It depends upon the quantity of coal con-\\nsumed.\\nQ. What relation is there between the quantity\\nof coal consumed and the area of the chimney\\nA. The area of the cross-section in square\\ninches should be from 1 J to 2 times the number\\nof pounds of coal consumed per hour.\\nQ. According to this rule, what would be the\\nproper diameter of chimney for 500 horse-power\\nboilers of the water-tube type\\nA. Assuming an evaporation of 10 pounds of\\nwater under normal conditions per pound of coal,\\nwe have:\\nPounds of water evaporated per pound of\\ncoal 10.\\nTotal pounds of water evaporated per hour\\n30 X 500 15,000.\\nPounds of coal consumed per hour\\n1500.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0190.jp2"}, "191": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 169\\nArea of chimney 1500 X IJ to 1500 X 2\\n2250 to 3000 square inches.\\nDiameter of chimney 53J to 61f inches\\nor, say, 60 inches.\\nQ. What is the relation between grate and\\nchimney area?\\nA. A fair average of coal consumed per square\\nfoot of grate surface for anthracite coal is 12\\npounds. Hence the chimney area being about If\\nsquare inches per pound of coal, we have:\\nChimney area per pound of coal If square\\ninches.\\nChimney area per square foot of grate surface\\nlfXl2 21 square inches\\nI square foot\\nor, in other words, the chimney area should be\\nabout Y of the grate area.\\nQ. Is there any relation between the cross-sec-\\ntion of chimney and horse-power\\nA. For fire-tube boilers the average heating\\nsurface is 12 square feet per horse-power, while the\\nratio of grate to heating surface is about 1 35.\\nHence the grate surface per horse-power may be\\ntaken roughly as -g-f or about J. If, now, we take\\nthe results above, we have for the chimney area\\nper horse-power, J X y ar fire-tube boilers,\\nand a trifle smaller, say ^V? ^^i water-tube boilers.\\nQ. What determines the height of chimneys", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0191.jp2"}, "192": {"fulltext": "170\\nroper s catechism for\\n\u00e2\u0080\u00a2saqDui\\n8:^BniixoaddY jo\\najBiibs JO apis\\n2Sg5SS5g??^^^^SgSg^\u00c2\u00a7g\\nBaay [Binoy\\n1.77\\n2.41\\n3.14\\n3.98\\n4.91\\n5.94\\n7.07\\n8.30\\n9.62\\n12 57\\n15.90\\n19.64\\n23.76\\n28.27\\n33.18\\n38.48\\n44.18\\n50.27\\n\u00e2\u0080\u00a2J98J SJBllbg\\nuajy 8Aip8jaa\\n0.97\\n1.47\\n2.08\\n2.78\\n3.58\\n4.47\\n5.47\\n6.57\\n7.76\\n10.44\\n13 51\\n16.98\\n20.83\\n25.08\\n29.73\\n34. 76\\n40.19\\n46.01\\ni\\no\\nH\\nw\\no\\n\u00c2\u00a73\\ni\\no\\nis\\na\\ns\\na\\n\u00c2\u00a7!igii\\n748\\n918\\n1105\\n1310\\n1531\\n1770\\n2027\\nd\\niisiiiii\\nd\\n389\\n503\\n632\\n776\\n934\\n1107\\n1294\\n1496\\n1720\\nd\\no\\n271\\n365\\n472\\n593\\n728\\n876\\n1038\\n1214\\n1415\\n1616\\nd\\n1\\n182\\n219\\n258\\n348\\n449\\n565\\n694\\n835\\n995\\n1163\\n1344\\n1537\\nd\\no\\nC3\\n^amimnm\\nd\\n8\\nSS8||||g^||\\nd\\n^^s*il^\u00c2\u00abS\\nd\\nS\\ns?\u00c2\u00a7sf2g;2^\\ng\\n?aS^^S\\nni\\nsaqduj\\nla\\ns?5 5;?5g?\u00c2\u00a7sg^^^gg^S3gg", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0192.jp2"}, "193": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n171\\nA. The height of chmmeys is determined by\\nthe required draught. It is influenced by the\\nkind of coal to be burned as well as by its loca-\\ntion, as it must, in general, be higher than hills\\nor buildings in the immediate vicinity.\\nSTEAM SEPARATOES AND TRAPS.\\nQ. For what purpose are steam separators used\\nA. For removing moisture from steam before\\nit enters the engine cylinder; or they may be used\\nfor extracting other liquids from\\nvapors, as, for example, the oil\\ncontained in exhaust steam.\\nThe first named is generally\\ncalled a live steam separator.\\nQ. Why should it be advis-\\nable to extract the entrained\\nwater from steam before using\\nit in the engine?\\nA. Because an accumulation\\nof water in the cjdinder is often\\nthe cause of blowing out the head\\nof the cylinder or steam-chest\\ncover; and also because the\\npresence of moisture in steam re-\\nduces the economy of the engine.\\nQ. How should a separator be\\nconstructed to be efficient", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0193.jp2"}, "194": {"fulltext": "172 roper s catechism for\\nA. The steam entering the apparatus at a high\\nvelocity should have its direction of flow altered\\nor reversed, so as to destroy the momentum of\\nthe liquid particles, permitting them to fall by\\ngravity into a vessel provided for that purpose.\\nThis being accomplished, the steam should not\\nagain come in contact with the water, as it is\\nliable to pick up particles of an}^ liquid with\\nwhich it comes in contact. Finally, the cross-\\nsection for the passage of the steam should be\\nample in all parts of the apparatus, so that the\\nlosses by friction will be reduced to a minimum.\\nQ. For what other purpose are separators fre-\\nquently used\\nA. To extract the oil from feed-water in open\\nheaters.\\nQ. How are these constructed\\nA. In various ways. In the Pittsburgh heater,\\nillustrated on page 157, the separation of oil is\\naccomplished by means of a small cylinder placed\\non the side of the apparatus near the bottom.\\nThis cylinder is connected by pipes to the steam-\\nand water-spaces of the heater, as shown in the\\ncut; the feed to the pump is at the top of the\\nsmall cylinder. As the oil floats on the surface\\nof the water it is evident that none will find its\\nway into the small cylinder, so long as the water\\nis maintained at its proper level, while if the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0194.jp2"}, "195": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 173\\nlevel of the water should become too low the\\npump will not be supplied with water.\\nQ. For what purpose are steam traps used\\nA. For the purpose of removing condensed\\nsteam from a system of steam piping, without\\nallowing any of the steam itself to escape.\\nQ. How is this accomplished\\nA. The trap is connected to the piping to be\\ndrained and contains an outlet controlled by a\\nvalve. The valve in some traps is operated by a\\nfloat, and in others by means of a bent tube of\\nelliptical cross-section. In the former the opening\\nand closing of the valve is determined directly by\\nthe amount of water in the trap. In the curved-\\ntube system the opening and closing of the valve\\ndepend upon the temperature.\\nQ. Suppose a separator, trap, heater, or other\\nappliance should require cleaning or repairing,\\nwill it not be necessary to shut down the plant\\nA. No; they should always be provided with\\nby-passes for both steard and water, that is, they\\nshould be connected with the piping in such a\\nway that the steam or water may be made to pass\\ntemporarily through auxiliary pipes around the\\nheater trap or other appliance.\\nQ. Give a brief description of the manner in\\nwhich a by-pass is usually constructed.\\nA. As generally constructed a by-pass consists", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0195.jp2"}, "196": {"fulltext": "174\\nROPER S CATECHISM FOR\\nof a pipe leading around the appliance and fitted\\nwith three valves V, V\u00e2\u0080\u009e and V,\u00e2\u0080\u009e as shown in\\nthe accompanying cut, the trap (in this case)\\nbeing connected to the piping by pipe unions U,\\nU. Under ordinary conditions, that is, when the\\ntrap is in operation, the valves V, and V\u00e2\u0080\u009e remain\\nopen while V,\u00e2\u0080\u009e is closed. If, however, the trap\\nis to be taken out for any reason, it is only neces-\\nsary to close the valves V, and V\u00e2\u0080\u009e and to open\\ny The steam, instead of passing through the\\ntrap, will then pass around it through the by-pass,\\nand the trap or other appliance may be discon-\\nnected by means of the two unions U, U, without\\nin any way interfering with the operation of the\\nplant. For feed- water heaters, etc., a similar\\nby-pass should be provided for the water.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0196.jp2"}, "197": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 175\\nTHE STEAM ENGINE.\\nThe steam engine, as it exists to-day, may be said\\nto be the invention of James Watt. While he\\nwas not the originator of the idea of utilizing the\\npressure and expansive force of steam for the\\npurpose of doing mechanical work, Watt s dis-\\ncoveries and inventions, in this connection, were\\nof such importance that he is generally considered\\nas the inventor of the steam engine.\\nIn looking over the models of engines and\\naccessories of James Watt, a great many of which\\nare exhibited in the South Kensington Museum,\\nLondon, it is surprising to note how little change\\nthe steam engine has undergone during the past\\ncentury. It is to-day, in fact, the same machine\\nthat it was then; and while the results which have\\nsince been accomplished in the way of economy,\\nregulation, speed, and power doubtless exceed the\\nmost sanguine expectations of the early workers\\nin this field, the modern engine is, nevertheless,\\npractically the same machine that it was a century\\nago.\\nThe efforts of steam engineers, since the days of\\nJames Watt, have produced not only vastly more\\npowerful machines, higher and more uniform\\nspeed and what now seems perfect running, but", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0197.jp2"}, "198": {"fulltext": "176 eoper s catechism for\\nthey have also very materially increased the effi-\\nciency of the engine. And yet the results which\\nhave been obtained in the way of economy still\\nleave much to be desired. The steam engine and\\nboiler, considered as an apparatus for converting\\nthe potential energy contained in coal or other\\nfuel into mechanical work, is a most extravagant\\nmachine. With the very best engines and boilers\\nwe are not able to develop a horse-power with a\\nconsumption of much less than 3 pounds of coal\\nper hour, while if all of the energy were utilized\\nwe should obtain from that amount of good coal\\nnot less than 14 horse-power. In other words,\\nthe best engines and boilers utilize only about 7\\nper cent, of the latent energy of the fuel. As far\\nas the engine itself is concerned, the mechanism\\nleaves but little to be desired. In such engines as\\nare generally used for electric lighting, that is, the\\nhigh-speed automatic cut-off type, the regulation\\nis such that the full load may be suddenly thrown\\non or off without producing a variation in the\\nspeed of the engine greater than 1 to 2 per cent.,\\nand at all loads such engines, when properly\\nadjusted, run smoothly, noiselessly, and without\\nproducing vibration.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0198.jp2"}, "199": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 177\\nHORSE-POWER.\\nQ. What is meant by the power of a steam\\nengine\\nA. The amount of work it will do in a given\\nspace of time.\\nQ. Define the unit of power.\\nA. The unit generally adopted for the power of\\nsteam engines is the horse-poiver. An engine of 1\\nhorse-power means one which will raise 550\\npounds 1 foot a second or its equivalent.\\nQ. What would be equivalent to this amount\\nof work?\\nA. As work is the product of force times space,\\na weight of 550 pounds raised 1 foot would be\\nequal to 550 foot-pounds of work. If 1 pound\\nwere raised 550 feet or 2 pounds 275 feet, the\\namount of work would be the same. Hence, a\\nhorse-power may be defined as 550 foot-pounds\\nper second, 33,000 foot-pounds per minute, 1,980,-\\n000 foot-pounds per hour, and so on.\\nQ. Name some form of work other than raising\\na weight, which would be equivalent to 1 horse-\\npower.\\nA. An electric current of 10 amperes at 74.6\\nvolts.\\nQ. What determines the horse-power of a steam\\nengine\\n12", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0199.jp2"}, "200": {"fulltext": "178 roper s catechism for\\nA. The diameter of the cylinder, length of\\nstroke, average or mean effective pressure on the\\npiston, and the speed.\\nQ. How do you calculate the horse-power of an\\nengme\\nA. By multiplying the area of the piston in\\nsquare inches by the mean effective pressure acting\\nupon it; multiplying the length of stroke in feet\\nby the number of strokes (twice the number of\\nrevolutions) per minute; multiplying the first\\nproduct by the second, and dividing by 33,000.\\nQ. What would be the horse-power of an 18 x\\n18 engine at 200 revolutions per minute, with a\\nmean effective pressure of 45 pounds per sq. inch\\nA. Area of piston 18 X 18 X .7854 254\\nsquare inches,\\nTotal mean pressure on piston 254 X 45\\n11,430 pounds.\\nNumber of strokes per minute 2 X 200\\n400,\\nLength of stroke 18 -f- 12 1.5 feet,\\nDistance traveled by piston per minute\\n400 X 1.5 600 feet,\\nWork done per minute 11,430 X 600\\n6,858,000 foot-pounds,\\nHorse-power 6,858,000 33,000 208.\\nQ. How would you write the above rule in the\\nshape of a formula", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0200.jp2"}, "201": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 179\\nA. Let HP horse-power,\\nP mean effective pressure in pounds\\nper square inch,\\nL length of stroke in feet,\\nA area of piston in square inches,\\nN number of strokes per minute,\\nB number of revolutions per min-\\nute,\\nS piston speed in feet per minute,\\nd 7= diameter of cylinder in inches;\\nthe formula corresponding to the above rule would\\nbe:\\n(A .7854cP)\\nPLAN APS\\n33,000 33,000\\nQ. Given the horse-power, mean effective pres-\\nsure, and piston speed, how would you find the\\nproper diameter of cylinder? Give rule and\\nformula.\\nA. The formula would be\\nI 42,017 HP ^\u00e2\u0080\u009e_ I\\nd ^J or 205\\nHP\\nPS PS\\nand the rule as follows Multiply the horse-power\\nby 42,017; multiply the piston speed by the\\nmean effective pressure; divide the first product\\nby the second and extract the square root of the\\nquotient.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0201.jp2"}, "202": {"fulltext": "180 eoper s catechism for\\nQ. Write formulse for length of stroke, piston\\nspeed, and number of revolutions when the other\\nquantities are given.\\nJ r ^3,000 HP\\nA. Length ot stroke L\\nFAN\\n16,500 HP _ 21,010 H P\\nPAR P RcV\\nPiston speed S=NL 2RL\\n33,000 HP\\nPA\\nNumber of revolutions R\\n16,500 HP _ 21,010 HP\\nPAL PLd\\nS\\n2L\\nQ. What do you understand by the mean effec-\\ntive pressure\\nA. The average forward pressure on the piston\\nless the back pressure.\\nQ. What is the average forward pressure\\nA. It is a pressure depending upon the initial\\npressure in the cylinder and the point of cut-off.\\nQ. How do you find the average (forward)\\npressure in a given case\\nA. In the following table look up the multiplier\\ncorresponding to the cut-off. To the initial gauge\\npressure in the cylinder add 14.7 pounds to ob-\\ntain the initial absolute pressure. Multiply this\\nby the number corresponding to the cut-off in the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0202.jp2"}, "203": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n181\\ntable, and the product will be the absolute average\\nforward pressure.\\nQ. What would be the average pressure corre-\\nsponding to 80 pounds initial by the gauge and J\\ncut-off?\\nA. 80 14.7 94.7 X .5965 56.45 absolute\\n14.7\\n41.75 gauge.\\nTABLE\\nOF MULTIPLIERS FOR MEAN ABSOLUTE PRESSURES.\\nCut-Off.\\nRate of\\nExpan-\\nsion.\\nMulti-\\nplier.\\nCut-Off.\\nRate of\\nExpan-\\nsion.\\nMulti-\\nplier.\\n1\\n4\\n3\\n2.66\\n2\\n.5965\\n.6995\\n.7428\\n.8465\\n1\\ni\\nf\\n1.6\\n1.5\\n1.33\\n1.14\\n.9188\\n.9370\\n.9657\\n9919\\nQ, How do you find the mean effective pressure?\\nA. Find the absolute mean forward pressure as\\ndescribed above and deduct the absolute back\\npressure.\\nQ. What is the back pressure?\\nA. It is the pressure opposing the piston. In\\nengines exhausting into the atmosphere it is", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0203.jp2"}, "204": {"fulltext": "182 roper s catechism for\\nusually about 15 pounds per square inch (atmos-\\npheric pressure). In condensing engines it varies\\nfrom two (2) pounds per square inch up to at-\\nmospheric pressure, depending on the vacuum.\\nWhere the exhaust is used in a heating system, it\\nvaries from 16 to 25 pounds, depending on the\\namount of friction in the piping.\\nQ. What horse-power would be developed by\\nan engine under the following conditions:\\nStroke, 12 inches;\\nDiameter of cylinder, 12 inches;\\nInitial gauge pressure, 80 pounds per square\\ninch;\\nSpeed, 300 revolutions per minute;\\nBack pressure (gauge), 5 pounds per square\\ninch;\\nCut-off, 1.\\nA. The absolute initial pressure is 80 14.7\\n94. 7 pounds, and the multiplier in the table cor-\\nresponding to cut-off being .5965, the average\\nforward pressure is 94.7 X .5965 56.45 pounds\\nabsolute. The back pressure being 5 -f- 14.7\\n19.7 pounds absolute, the mean effective pressure\\nis 56.45 19.7 36.75 pounds per square inch.\\nArea of piston 12 X 12 X .7854 113.1\\nsquare inches.\\nTotal mean pressure on piston 36.75 X\\n113.1 =4153 pounds.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0204.jp2"}, "205": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 183\\nLength of stroke :=12-v-12 l foot.\\nNumber of strokes 300 X 2 600 per\\nminute.\\nDistance traveled by piston 600 X 1\\n600 feet per minute.\\nWork done per minute 600 X 4153\\n2,491,800.\\nHorse-power 2,491,800 33,000 75\\nhorse-power.\\nQ. If in the above example, instead of exhaust-\\ning against a back pressure, a condenser had been\\nused, in which there was a vacuum of 22 inches,\\nwhat would have been the gain in power\\nA. Since each inch of vacuum corresponds to\\nabout pound, the back pressure would be 22 X\\n11 pounds less than atmospheric, or 14.7\\n11 3.7 pounds absolute. Hence the mean\\neffective pressure 56.45 3.7 52.75 pounds,\\nT 52.75X113.1 X600\\nand the horse-power 108.\\nThat is, the gain in power would be 108 75\\n33 horse-power, or over 40 per cent.\\nEXPLANATION OF TABLE.\\nThe table on the following pages is calculated\\nfor different cylinder diameters from 4 inches to 5\\nfeet and for piston speeds of 300 to 600 feet per\\nminute. To find the horse-power of any engine", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0205.jp2"}, "206": {"fulltext": "184\\nroper s catechism for\\nTABLE\\nOF HOESE POWEE FOR DIFFERENT CYLHSTDEE DIAMETERS\\nAND PISTON SPEEDS.\\nHorse-Power per Pound Mean Effective Pressure.\\n2\\nSpeed of Piston in Feet per Minute.\\ns 5\\n300\\n350\\n400\\n450\\n500\\n550\\n600\\nInches.\\n4\\n.114\\n.133\\n.152\\n.171\\n.19\\n.209\\n.228\\n4\\n.144\\n.168\\n.192\\n.216\\n.24\\n.264\\n.288\\n5\\n.18\\n.21\\n.24\\n.27\\n.30\\n.33\\n.36\\n5\\n.216\\n.252\\n.288\\n.324\\n.36\\n.396\\n.432\\n6\\n.256\\n.299\\n.342\\n.385\\n.428\\n.471\\n.513\\n6K\\n.807\\n.391\\n.409\\n.461\\n.512\\n.563\\n.614\\n7\\n.348\\n.408\\n.466\\n.524\\n.583\\n.641\\n.699\\nly,\\n.401\\n.468\\n.534\\n.602\\n.669\\n.735\\n.802\\n8\\n.456\\n.532\\n.608\\n.685\\n.761\\n.837\\n.912\\n8\\n.516\\n.602\\n.688\\n.774\\n.86\\n.946\\n1.032\\n9\\n.577\\n.674\\n.770\\n.866\\n.963\\n1.059\\n1.154\\n9J^\\n.644\\n.751\\n.859\\n.966\\n1.074\\n1.181\\n1.288\\n10\\n.714\\n.833\\n.952\\n1.071\\n1.390\\n1.309\\n1.428\\n10^\\n.787\\n.919\\n1.050\\n1.181\\n1.313\\n1.444\\n1.575\\n11\\n.864\\n1.008\\n1.152\\n1.296\\n1.44\\n1.584\\n1.728\\n113^\\n.943\\n1.1\\n1.257\\n1.414\\n1.572\\n1.729\\n1.886\\n12\\n1.025\\n1.195\\n1.366\\n1.540\\n1.708\\n1.880\\n2.050\\n13\\n1.206\\n1.407\\n1.608\\n1.809\\n2.01\\n2.211\\n2.412\\n14\\n1.398\\n1.631\\n1.864\\n2.097\\n2.331\\n2.564\\n2.797\\n15\\n1.606\\n1.873\\n2.131\\n2.409\\n2.677\\n2.945\\n3.212\\n16\\n1.827\\n2.131\\n2.436\\n2.741\\n3.045\\n3.349\\n3.654\\n17\\n2.054\\n2.396\\n2.739\\n3.081\\n3.424\\n3.766\\n4.108\\n18\\n2.312\\n2.697\\n3.083\\n3.468\\n3.854\\n4.239\\n4.624\\n19\\n2.577\\n3.006\\n3. 436\\n3.865\\n4.295\\n4.724\\n5.154\\n20\\n2.855\\n3.331\\n3.807\\n4.265\\n4.7r9\\n5.234\\n5.731\\n21\\n3.148\\n3.672\\n4.197\\n4.722\\n5.247\\n5.771\\n6.296\\n22\\n3.455\\n4.031\\n4.607\\n5.183\\n5.759\\n6.334\\n6.911\\n23\\n3.776\\n4.405\\n5.035\\n5.664\\n6.294\\n6.923\\n7.552\\n24\\n4.111\\n4.797\\n5.482\\n6.167\\n6.853\\n7.538\\n8.223\\n25\\n4.461\\n5.105\\n5.948\\n6.692\\n7.436\\n8.179\\n8.923\\n26\\n4.826\\n5.630\\n6.435\\n7.2.39\\n8.044\\n8.848\\n9.652\\n27\\n5.199\\n6.066\\n6.932\\n7.799\\n8.666\\n9.532\\n10.399\\n28\\n5.596\\n6.529\\n7.462\\n8.395\\n9.. 328\\n10.261\\n11.193\\n29\\n6.006\\n7.007\\n8.008\\n9.009\\n10.01\\n11.011\\n12.012", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0206.jp2"}, "207": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n185\\nHorse-Power per Pound Mean Effective Pressure.\\nI..I\\nSpeed of Piston in Feet per Minute.\\n2 o\\n5 5\\n300\\n350\\n400\\n450\\n500\\n550\\n600\\nInches.\\n30\\n6.426\\n7.497\\n8.568\\n9.639\\n10.71\\n11.781\\n12.852\\n31\\n6.865\\n8.001\\n9.144\\n10.287\\n11.43\\n12.573\\n13.716\\n32\\n7.308\\n8.526\\n9.744\\n10.962\\n12.18\\n13.398\\n14.616\\n33\\n7.770\\n9.065\\n10.360\\n11.655\\n12.959\\n14.245\\n15.54\\n34\\n8.238\\n9.611\\n10.984\\n12.357\\n13.73\\n15.103\\n16.476\\n35\\n8.742\\n10.199\\n11.656\\n13.113\\n14.57\\n16.027\\n17.484\\n36\\n9.252\\n10.794\\n12.336\\n13.878\\n15.42\\n16.962\\n18.504\\n37\\n9.774\\n11.403\\n13.032\\n14.861\\n16.29\\n17.919\\n19.548\\n38\\n10.308\\n12.026\\n13.744\\n15.462\\n17.18\\n18.898\\n20.616\\n39\\n10.86\\n12.67\\n14.48\\n16.29\\n18.1\\n19.91\\n21.62\\n40\\n11.424\\n13.328\\n15.232\\n17.136\\n19.04\\n20.944\\n22.848\\n41\\n12.006\\n14.007\\n16.008\\n18.009\\n20.00\\n22.011\\n24.012\\n42\\n12.594\\n14.693\\n16.792\\n18.901\\n20.99\\n23.089\\n25.188\\n48\\n13.20\\n15.4\\n17.6\\n19.8\\n22.0\\n24.2\\n26.4\\n44\\n13.818\\n16.121\\n18.424\\n20.727\\n23.03\\n25.333\\n27.636\\n45\\n14.454\\n16.863\\n19.272\\n21.681\\n24.09\\n26.339\\n28.908\\n46\\n15.128\\n\u00e2\u0080\u00a217.626\\n20.144\\n22.662\\n25.18\\n27.698\\n30.216\\n47\\n15.768\\n18.396\\n21.024\\n23.652\\n26.28\\n28.908\\n31.536\\n48\\n16.446\\n19.187\\n21.928\\n24.669\\n27.41\\n30.151\\n32.152\\n49\\n17.142\\n19.999\\n22.856\\n25.713\\n28.57\\n31.427\\n34.284\\n50\\n17.85\\n20.825\\n23.8\\n26.775\\n29.75\\n32.725\\n35.7\\n51\\n18.54\\n21.665\\n24.76\\n27.855\\n30.95\\n34.045\\n37.08\\n52\\n19.296\\n22.512\\n2.5.728\\n28.944\\n32.16\\n35.376\\n38.592\\n53\\n20.052\\n23.394\\n26.736\\n30.078\\n33.42\\n36.762\\n40.104\\n54\\n20.82\\n24.29\\n27.76\\n31.23\\n34.7\\n38.17\\n41.64\\n55\\n21.594\\n25.193\\n28.792\\n32.391\\n35.99\\n39.589\\n4.3.188\\n56\\n22.386\\n26.117\\n29.848\\n33.579\\n37 31\\n41.041\\n44.772\\n57\\n23.196\\n27.062\\n30.928\\n34.794\\n38.66\\n42.526\\n46.392\\n58\\n24.018\\n28.021\\n32.024\\n36.027\\n40.03\\n44.033\\n48.036\\n59\\n24.852\\n28.994\\n33.136\\n37.278\\n41.42\\n45.562\\n49.704\\n60\\n25.698\\n29.981\\n34.264\\n38.547\\n42.83\\n47.113\\n51.396\\nby means of this table, multipl}^ twice the number\\nof revolutions per minute by the length of stroke\\nin feet. This will give the piston speed in feet\\nper minute. Look up the horse-power from the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0207.jp2"}, "208": {"fulltext": "186 koper s catechism for\\ntable for this piston speed and the proper diameter\\nof cyHnder and multiply it by the mean effective\\npressure. Take the above example as an illustra-\\ntion; the piston speed was found to be 600 feet\\nper minute, and hence for a 12-inch cylinder the\\nhorse-power from the table is 2.05 for each pound\\nof mean effective pressure. Hence multiplying\\nthis by the mean effective pressure, 52.75, we have\\n52.75 X 2.05 108 horse-power.\\nQ. Is the pressure in the boiler and the pressure\\nin the cylinder nearly equal in all cases\\nA. No; the pressure in the C3dinder is in many\\ncases less than the pressure in the boiler.\\nQ. From what causes does the difference between\\nthe pressure in the boiler and the pressure in the\\ncylinder arise\\nA. Firsts from a malconstruction of the steam-\\npipe and steam-ports; secondly^ from loss by radi-\\nation and condensation; thirdly^ from the action of\\nthe governor; and, fourthly^ from the bad condition\\nof the piston.\\nQ. What is the most economical steam pressure\\nto use in the cylinder of a high-pressure engine\\nA. From 80 to 90 pounds to the square inch.\\nQ. Why should 80 or 90 pounds to the square\\ninch be more economical than lower pressure, say\\n40 or 45 pounds to the square inch\\nA. On account of the back pressure of the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0208.jp2"}, "209": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 187\\natmosphere; for instance, if we have a pressure\\nof 45 pounds to the square inch on the piston,\\nthe loss by atmospheric pressure is 15 pounds to\\nthe square inch, which is about J- of the pressure\\non the piston, leaving only 30 pounds for useful\\neffect and to overcome the friction of the engine;\\nif Ave have a pressure of 90 pounds to the square\\ninch, the loss is only 15 pounds to the square inch,\\nor about\\nQ. Is it economical to use an engine that is too\\nlarge for the work to be done\\nA. No; because an engine running below its\\nrated load wastes steam. If it is a throttling\\nengine^ the steam is throttled, or reduced without\\ndoing work, which means a loss. If it is an\\nautomatic cut-off engine the expansion is increased,\\nwhich also impairs the economy of the engine.\\nQ. Why does increasing the rate of expansion\\nreduce the economy\\nA. There is one point of cut-off which is more\\neconomical than any other, because at that point\\nthe steam expands to atmospheric pressure and is\\nnot capable of doing any more w^ork when ex-\\nhausted. This cut-off, for an initial pressure of\\n80 pounds, is J. If the rate of expansion is\\nreduced, the steam is exhausted before it has done\\nas much work as it is capable of doing, while if\\nthe rate of expansion is increased, the terminal", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0209.jp2"}, "210": {"fulltext": "188 roper s catechism for\\npressure is liable to fall below that of the atmos-\\nphere, in which case the opposing pressure of\\nthe atmosphere will retard the piston during the\\nlatter part of its stroke. This also means a waste\\nof power.\\nDIFFERENT KINDS OF ENGINES.\\nQ. What is the difference between condensing\\nand non-condensing engines\\nA. In non-condensing engines the steam, after\\nhaving done its work in the steam cylinder, escapes\\ninto the atmosphere, or sometimes into a heating\\nsystem where the heat still contained in the steam\\nis partially utilized. In the condensing engine\\nthe steam exhausts into a condenser, where it\\ncomes in contact with some cooling medium, in\\nconsequence of which it is condensed, producing\\na partial vacuum behind the piston.\\nQ. What is the object of condensing?\\nA. To increase the effective pressure on the\\npiston and consequently the power.\\nQ. By how much is the power of a non-con-\\ndensing engine increased when a condenser is\\nadded?\\nA. The power is increased in the ratio which\\nthe vacuum in the condenser bears to the mean\\neffective pressure.\\nQ. Suppose an engine working at 80 pounds", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0210.jp2"}, "211": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 189\\ninitial pressure and J cut-off exhausting against\\nthe atmosphere, had a condenser added. If there\\nwere an effective vacuum of 26 inches, what would\\nbe the percentage increase m power if the speed\\nremained the same\\nA. According to the rules given above, the mean\\neffective pressure was originally\\n(80 14.7) X .5965 14.7 41.75 pounds,\\nwhich was increased by adding a condenser whose\\nvacuum is 26 inches by\\n26 2 13 pounds.\\nHence the increase in power is\\n31 per cent.\\n41.75\\nQ. Does it not require power to operate a con-\\ndenser\\nA. Yes; but generally not so much as is gained\\nby its use.\\nQ. What percentage is gained in economy by\\ncondensing?\\nA. From 20 to 35 per cent., depending on the\\ntype and size of engine.\\nQ. Why, then, are not all engines built for\\ncondensing\\nA. Because in small engines the saving in fuel\\nwould not be enough to warrant the additional first\\ncost, and the increased labor and attention which\\nthe plant would require. Further, in many in-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0211.jp2"}, "212": {"fulltext": "190 eoper s catechism for\\nstallations the steam leaving at atmospheric pres-\\nsure can be used to good advantage for heating\\npurposes or for purifying the water before it enters\\nthe boiler. Finally, in cities the cost of the water\\nis frequently in excess of what would be saved in\\nfuel.\\nQ. How much water is required for condensing\\nA. About 25 times as much as passes through\\nthe engine.\\n(See also Condensers, page 233.\\nQ. AVhat do you mean by simple or single\\nexpansion and by multiple expansion engines\\nA. A simple or single expansion engine is one\\nin which the steam is used expansively in one\\ncylinder or set of cjdinders only, and after ex-\\nhausting is not used again for doing work in the\\nengine. In multiple expansion engines the steam\\nexpands successively, doing work, in two or more\\ncylinders or sets of cylinders.\\nQ. What are the names given respectively to\\nengines in which the steam expands two, three,\\nand four times\\nA. Compound, triple expansion, and quadruple\\nexpansion engines.\\nQ. What is meant by compounding\\nA. By the term compounding is meant\\nexpanding the steam successively in two or more\\ncylinders.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0212.jp2"}, "213": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 191\\nQ. Why are engines compounded\\nA. To secure greater economy in the use of\\nsteam.\\nQ. Is not the friction of an engine greater if it\\nuses the same amount of steam in two or three\\ncylinders than if the entire work is performed in\\na single cylinder\\nA. Yes; because each cylinder (except in tan-\\ndem compound engines) has its own crank and\\nattending mechanism.\\nQ. Why, then, is expanding successively in\\nseveral cylinders productive of economy in the\\nuse of fuel\\nA. The higher the initial steam pressure used\\nin a steam-power plant, and the lower the terminal\\npressure (provided it is not less than the back\\npressure), the greater the economy. Hence, in\\norder to secure the greatest fuel economy, there\\nmust of necessity be a wide range of temperature\\nfrom live to exhaust steam. If the expansion\\noccurred in a single cylinder, the walls of the latter\\nand a portion of the steam passages would be\\nsubjected to this variation in temperature at each\\nstroke. In other words, the cylinder walls and\\nsteam passages would be chilled at the end of the\\nstroke and, therefore, the live steam would be\\npartially condensed, as it enters the cylinder,\\nwithout doins: work. It is in reducing this loss", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0213.jp2"}, "214": {"fulltext": "192 roper s catechism for\\nof steam by condensation, called initial condensa-\\ntion, that compounding effects economy in fuel,\\nbecause if the expansion occurs successively in\\ntwo cylinders, instead of all in one, the range of\\n\u00e2\u0080\u00a2temperature is only one-half as great and con-\\nsequently the condensation is reduced proportion-\\nately.\\nQ. What should be the relative sizes of cylinders\\nin multiple expansion engines\\nA. They should be so proportioned that approx-\\nimately the same amount of work is done by each\\ncylinder. The first cylinder will be the smallest\\nin diameter and the last the largest.\\nQ. What names are given to the different\\ncylinders of multiple expansion engines\\nA. The one which takes the steam direct from\\nthe boiler is called the high-pressure cylinder, and\\nthe one in which it expands last before finally\\nbeing exhausted to the atmosphere or condenser\\nis called the low-pressure; the others are called\\nintermediate-pressure cylinders.\\nQ. What is a receiver\\nA. It is a chamber in which the steam is stored\\nfrom the time it leaves one cylinder until it is\\nadmitted to the next.\\nQ. Why is a receiver necessary?\\nA. Because the cranks of the different cylinders\\nare usually not placed in the same position. For", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0214.jp2"}, "215": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 193\\nexample, in a two- or four-cylinder engine they\\nwould generally be placed at 90\u00c2\u00b0 and in a three-\\ncylinder engine at 120\u00c2\u00b0. Hence the cylinders are\\nnot taking steam during the time it is exhausted\\nin the preceding cylinder and, therefore, a chamber\\nmust be provided for storing the steam until it can\\nbe used.\\nQ. Why are cranks set at different angles\\nA. To secure a more uniform turning force on\\nthe crank shaft.\\nQ. Does not the fly-wheel accomplish the same\\nresult\\nA. Yes; but if this can be done without the aid\\nof a fly-wheel it is much better, especially since\\nin many instances, such as in marine engines, a\\nfly-wheel cannot be conveniently used.\\nQ. Why are compound engines operated as con-\\ndensing engines wherever possible\\nA. Because the increase in the mean effective\\npressure in the low-pressure cylinder is a large\\nproportion of the total. Low-pressure cylinders\\nof multiple expansion engines frequently have a\\nmean forward pressure of only 3 or 4 pounds, and\\nhence by the use of a condenser this may be\\nincreased very materially.\\nQ. What do you understand by a high-speed\\nengine\\nA. Strictly speaking, a high-speed engine is one\\n13", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0215.jp2"}, "216": {"fulltext": "194 roper s catechism for\\nwhich has a high piston velocity; but the term is\\nnow generally used to mean engines of high rota-\\ntive speed.\\nQ. What advantages do high (piston) speed\\nengines possess as compared to low-speed engines\\nA. Other things being equal, they are lower in\\nfirst cost, more economical to operate, and run\\nmore smoothly.\\nQ. What additional advantage is possessed by\\nhigh (rotative) speed engines?\\nA. They are better adapted for driving electric\\nmachinery and other shafting which requires to be\\nrun at a high speed of rotation.\\nQ. Why are high-speed engines lower in first\\ncost?\\nA. The power of an engine depends on the\\npiston area, stroke, mean pressure, and speed,\\nvarying directly as each one of these factors. If\\nthe speed is increased, any one of the other three\\nfactors may be proportionately decreased, and,\\ntherefore, it follows, that a high-speed engine may\\nbe built smaller and hence more cheaply for a\\ngiven horse-power than a low-speed engine.\\nQ. Why are they more economical in the use of\\nfuel?\\nA. Because one of the principal losses in steam\\nengines is that due to initial condensation and\\nre-evaporation, and this is the less the more steam", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0216.jp2"}, "217": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 195\\npasses through a given cylinder in a given time.\\nHence it is less in high- than in low-speed engines.\\nQ. Why do they run more smoothly\\nA. Principally because the effect of the recipro-\\ncating parts is to equalize the turning force on the\\ncrank pin, so that it is nearly the same at every\\npart of the stroke.\\nQ. A\u00c2\u00a5hat do you understand by automatic cut-\\noff and throttling engines\\nA. Automatic cut-off engines are those in which\\nthe speed is kept constant under a variable load\\nby a governor acting upon the cut-off that is, one\\nin which the steam is admitted longer, for heavy\\nloads than for light loads, the exact point at\\nwhich it is cut off being regulated by the governor.\\nIn the throttling engine, the period of admission\\nremains the same under all loads, but the initial\\npressure is regulated by the action of the governor\\non a throttle valve.\\nQ. Which of the two is the more economical\\nmethod\\nA. The automatic cut-off; because when the\\npressure of steam is reduced by a throttle valve, it\\nexpands without doing work and hence an amount\\nof energy is lost equal to that which would be\\nnecessary to raise the steam from the pressure at\\nwhich it is admitted to the C3dinder to that at\\nwhich it is delivered by the boiler.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0217.jp2"}, "218": {"fulltext": "196 roper s catechism for\\nQ. Under what conditions could throttling\\nengines be used\\nA. When the load remains uniform or nearly\\nso, because throttling engines with plain slide\\nvalves are simpler and cheaper to build than auto-\\nmatic cut-off engines.\\nQ. What are single- and double-acting engines\\nA. Single-acting engines are those in which\\nsteam is admitted on one side of the piston only.\\nIn double-acting engines it is admitted alternately\\non either side of the piston.\\nQ. What are the relative advantages of these\\ntwo types\\nA. For the same diameter of cylinder, length\\nof stroke, steam pressure, and speed, the double-\\nacting engine develops twice as much power. The\\nsingle-acting engine, however, has no piston rod,\\ncross-head, or guides, the connecting rod being\\nattached direct to the piston. Engines of this\\nclass usually run faster, however, than double-\\nacting engines, and they are so arranged that the\\ncrank dips into a vessel filled with oil, every\\nrevolution, all of the moving parts being encased\\nin an iron boxing. They are, therefore, well\\nadapted for use where the atmosphere contains\\nmuch grit and dust.\\nQ. What is a rotary engine\\nA. It is one in which a motion of rotation is", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0218.jp2"}, "219": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 197\\ni produced directly by the pressure of the steam\\nand not a reciprocating motion first, which is\\nafterward converted into a rotary motion, as in\\nthe ordinary type.\\nVALVES AND VALVE GEAES.\\nQ. What do you understand by the valve gear\\nof an engine?\\nA. All that part of its mechanism which is\\nused in the distribution of steam.\\nQ. Of what does the simplest form of valve\\ngear consist\\nJ.. Of a plain slide valve, an eccentric, and the\\nrods or links necessary for transmitting the motion\\nof the latter to the former.\\nQ. Describe the plain slide valve.\\nA. The diagram on page 198 shows the simplest\\nform of slide valve in its central position, that is,\\nin the position where steam is neither admitted to\\nnor exhausted from the engine. V is the valve,\\nS S are the steam passages through which steam is\\nadmitted to the cylinder C from the steam-chest\\nX. The latter, being in communication with the\\nboiler, is always filled with live steam when the\\nthrottle valve is open. E is the exhaust passage\\nwhich, being in communication with the exhaust\\npipe, allows the steam to pass into the atmosphere\\nor condenser after it has done its work in the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0219.jp2"}, "220": {"fulltext": "198\\nKOPER S CATECHISM FOR", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0220.jp2"}, "221": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 199\\ncylinder. R is the valve rod which receives its\\nmotion from the eccentric and, passing through a\\nstuffing-box, imparts motion to the valve.\\nQ. Explain briefly the method of action of the\\nvalve.\\nA. As already stated, the valve in the above\\ndiagram is shown in a position where steam is\\nneither admitted to nor exhausted from the\\ncylinder. In this position of the valve, the piston\\nwhich has nearly completed its stroke, is moving\\ntoward the left, while the valve is moving toward\\nthe right, as indicated by the arrows. Presently\\nthe valve will have uncovered the left steam pas-\\nsage and steam will be admitted behind the piston.\\nThis will continue until the steam passage is again\\ncovered by the valve on its return stroke. In the\\nmeantime the other steam passage will have been\\nuncovered and placed in communication with the\\nexhaust chamber E, and exhaust will take place\\nuntil this passage is again covered by the valve.\\nAfter that the process is reversed, steam being\\nadmitted to the right hand end of the cylinder\\nand exhausted from the left; and so on, continu-\\nously.\\nQ. What are the four important events in the\\nsteam distribution, which take place in every\\ndouble stroke of the engine\\nA. Admission, cut-off, release, and compression.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0221.jp2"}, "222": {"fulltext": "200 roper s catechism for\\nQ. Explain what you mean by these terms.\\nA. When the passage is first uncovered admis^\\nsion takes place and continues until the point of\\ncut-off is reached, which is when the passage is\\nagain covered. Release occurs when the passage\\nis opened to the exhaust, and compression when\\nthe latter is closed. From the time steam is cut\\noff until it is released expansion takes place.\\nQ. What do you mean by the terms lap, lead,\\neccentricity, travel, overtravel, angular advance\\nA. Outside or steam lap is the distance the outer\\nedge of the valve laps over the outer edge of the\\nsteam passage, in the central position of the valve,\\nthe distance a h in the cut.\\nInside or exhaust lap is the distance the inner\\nedge of the valve laps over the inner edge of the\\nsteam passage, in the central position of the valve,\\nthe distance c d in the cut.\\nLead is the amount the steam port is open when\\nthe piston is beginning its stroke. If the piston\\nbegins its stroke before the steam passage is\\nuncovered the lead is negative.\\nEccentricity, or throw of the eccentric, is the\\ndistance from the center of the shaft to the center\\nof the eccentric.\\nTravel of the valve is the total distance it moves\\non its seat between extreme positions. This travel\\nis equal to twice the throw of the eccentric.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0222.jp2"}, "223": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 201\\nOvertravel is the distance the valve travels above\\nwhat is necessary to fully uncover the steam pas-\\nsage.\\nAngle of advance is the angle by which the\\neccentric is in advance of the position which\\nwould bring the valve in its central position when\\nthe crank is on a dead center.\\nQ. Having given the various dimensions of a\\nvalve gear of this kind, how do you determine\\nwhen the events described above will take place\\nA. Graphically that is, with the aid of some\\ndiagram such as Zeuner s, Sweet s, or Reuleaux s.\\nOf these, Zeuner s is the one generally used in\\npractice.\\nQ. Briefly explain the Zeuner diagram and its\\nuse.\\nA. *Draw a line X to represent the crank at\\nthe beginning of the stroke, and with this as a\\nradius draw the crank circle ZX^, Xj, Xg, X^.\\nSuppose the crank to turn in the direction of the\\narrow. Through the point draw the line R R^\\nmaking the angle R Y equal to the angle of\\nadvance, and lay off the distances OR and OR\\nequal to the eccentricity or throw of the eccentric.\\nOn the lines R and R as diameters draw the\\ntwo circles C i? Z) and E R F. With as a\\ncenter and a radius A equal to the outside or\\n*From Eoper s Engineers Handy-Book, pp. 391-393.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0223.jp2"}, "224": {"fulltext": "202\\nroper s catechism for\\nsteam lap draw a circle A C D, and similarly with\\na radius B equal to the inside or exhaust lap,\\ndraw a circle B E F. Through the point and\\nJ\\nZEUNER DIAGRAM.\\nthe intersections (7, D, E, and F draw the lines\\nX,, Zj, Xg, and X,. We are now able\\nto take from the diagram all of the data necessary", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0224.jp2"}, "225": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 203\\nfor a complete understanding of the distribution\\nof steam in the cylinder:\\nX^ is the position of the crank when admission\\nof the steam begins.\\nX^ is the position of the crank when cut-off\\ntakes place, hence\\nX^ X^ is the angle traversed by the crank during\\nthe period of admission.\\n-Xg is the position of the crank when the exhaust\\nopens.\\nX^ is the position of the crank when the exhaust\\ncloses, hence\\nXg X^ is the angle traversed by the crank during\\nthe period of exhaust, and\\nX^ Xj is the angle traversed by the crank during\\nthe period of compression.\\nThe distances from the intersection of the circles\\nR and R^ with the lines X, X^, etc. represent\\nthe travel of the valve corresponding to the posi-\\ntions OX, Xj of the crank. The circle R repre-\\nsents the forward and the circle R the return\\nstroke, hence\\nX is the distance the valve has traveled from its\\ncentral position at the beginning of the stroke.\\nX the same for the return stroke.\\nis the outside or steam lap, hence\u00e2\u0080\u0094\\nA K is the distance the steam port is open at the\\nbeginning of the stroke or the steam lead.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0225.jp2"}, "226": {"fulltext": "204 roper s catechism for\\nR is the full travel of the valve.\\n5 is the inside or exhaust lap, hence\\nB Kis the distance the exhaust port is open at the\\nbeginning of the stroke or the exhaust lead.\\nAt the points C and D the travel of the valve is\\njust equal to the outside lap; hence in these posi-\\ntions of the crank the steam port opens and closes\\nrespectively; similarly at the points E and F the\\ntravel is just equal to the exhaust lap; hence, in\\nthese positions of the crank the exhaust port opens\\nand closes respectively. If we lay down from the\\npoint A a distance A H, equal to the width of the\\nport, and with as a center and a radius H\\ndraw an arc, cutting the line i? at J,\\nJ R is the distance the valve travels more than\\nenough to fully open the port, or the over-\\ntravel.\\nSimilarly, if we lay off from B the distance B L,\\nequal to the width of the port, and from the center\\nand a radius equal to L draw an arc, cutting\\nthe line R at M,\\n31 R is the distance the valve travels more than\\nenough to fully open the port to the exhaust.\\nIt will thus be seen that by a careful study of\\nthe diagram all information necessary for the\\nproper design and setting of the valve gear may\\nreadily be had. For example, in the above dia-\\ngram the cut-off takes place a little later than f", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0226.jp2"}, "227": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 205\\nstroke. It is evident that if it is desired to have\\nthe cut-off take place earUer, say at J stroke, it\\nwill be necessary for the outside lap circle, A C D^\\nto intersect the valve circle R in the line Y Y.\\nThis may be accomplished by increasing the out-\\nside lap, by reducing the eccentricity, or by chang-\\ning the angle of advance. However, any one of\\nthese changes would also affect the entire distribu-\\ntion, and it would probably be necessary to lay\\ndown several diagrams before the most advantage-\\nous dimensions could be obtained.\\nQ. How would you proceed to set the slide-\\nvalve of an engine\\nA. Place the crank on the dead center and give\\nthe valve the necessary amount of lead then turn\\nthe engine on the other center, and if the valve\\nhas the same amount of lead it is properly set.\\nBut if the lead on one end is more or less than on\\nthe other, the difference must be divided. When\\nthe valve is attached to the rod by means of jam-\\nnuts great care must be taken not to jam the nuts\\nagainst the valve, as that would prevent the valve\\nfrom seating.\\nQ. What is a link motion\\nA. It is a mechanism consisting of two eccen-\\ntrics and rods and a slotted link, designed for the\\npurpose of reversing an engine and varying its\\npoint of cut-off.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0227.jp2"}, "228": {"fulltext": "206 roper s catechism for\\nQ. How is this accomplished in the Stephenson\\nImk?\\nA. The two eccentrics, called respectively the\\nforward and back eccentric, are placed on the shaft\\nin different relative positions in such a way that, if\\nthe valve were operated by the one, the engine\\nwould move forward; and if by the other, it would\\nbe reversed. The link is attached to the ends of\\nthe two eccentric rods and hence receives a rocking\\nmotion. It is slotted and carries a movable block\\nin the slot to which the valve rod is attached. If\\nthe block is at the end of the link nearest the for-\\nward eccentric, the engine will move forward,\\nwhile if it is at the other end, it will be reversed.\\nQ. What happens when the block is in some\\nintermediate position?\\nA. The travel of the valve becomes less as the\\nblock approaches the center, and hence the cut-off\\nbecomes earlier. In the central position of the\\nblock, the travel of the valve is not sufficient to\\nuncover the ports, and hence the engine remains at\\nrest.\\nQ. In the ordinary form of D slide valve, is\\nthere not a good deal of friction between the valve\\nand its seat\\nA. Yes; the friction in the old forms of slide\\nvalve is very great, because the steam pressure on\\nthe back of the valve forces it tightly against its seat.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0228.jp2"}, "229": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 207\\nQ. How can this be avoided to a great extent\\nA. By the use of pressure plates, which relieve\\nthe back of the valve of its pressure, or by the use\\nof the piston valve, which, being of circular cross-\\nsection instead of flat, is balanced and conse-\\nquently the only pressure tending to force it\\nagainst the seat is that due to its own weight.*\\nQ. What objection is there to piston valves?\\nA. It is claimed that the seat wears unevenly\\nand hence they cannot be kept tight. With a\\nsuitable construction, however, the bushings form-\\ning the seat can be taken out and replaced with\\nvery little trouble and expense.\\nQ. Next to the slide-valve gear, as described\\nabove, what is the most common valve gear used\\nin stationary engines\\nA. The Corliss gear.\\nQ. What are the essential differences between\\nthe Corliss and the plain slide-valve gear\\nA. Instead of a single valve which admits and\\nexhausts the steam, the Corliss gear has four\\nindependent valves which rotate partially about\\nan axis. The four valves, of which two are for\\nthe admission and cut-off and the other two for\\nthe release and compression of the steam in the\\ncylinder, are operated by a single eccentric and\\nwrist plate, but the two steam valves are connected\\n*See Roper s Engineers Handy-Book, pp. 398-402.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0229.jp2"}, "230": {"fulltext": "208 roper s catechism for\\nto the wrist plate in such a way that they can be\\ndetached at any moment. This is accompHshed\\nby a tripping or releasing mechanism controlled\\nby a ball governor, and as soon as the steam valves\\nare released, they are closed by the action of a\\ndash pot, and hence the cut-off is under the direct\\ncontrol of the governor. The exhaust valves are\\nnot released from the wrist plate, and hence the\\nrelease and compression are constant.\\nQ. What do you understand by a four-valve\\nengine\\nA. It is one having a valve gear midway between\\nthe plain slide valve and the Corliss gears. It has\\nfour independent valves like the Corliss, but, like\\nthe plain slide valve, their motion is positive and\\nthey have no releasing mechanism. The cut-off\\nis varied by the travel of the valve.\\nQ. What are the relative advantages and dis-\\nadvantages of the Corliss and four- valve types of\\nvalve gear\\nA. The Corliss has the advantage that the cut-\\noff is quick and sharp and that there is very little\\npower lost in friction. The valves being, however,\\nunder the control of a spring or dash pot, they\\ncannot be run at a high rotative speed. This\\nconstitutes the main advantage of the four-valve\\ngear, that it can be run at as high a speed as a\\nsingle-valve engine, and it is almost, but not quite,", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0230.jp2"}, "231": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 209\\nas economical as the Corliss. Both have the ad-\\nvantage over single-valve engines that the steam\\nenters and leaves the cylinder by separate passages,\\nand hence there is less loss by condensation.\\nThey are, therefore, much more economical in the\\nuse of steam than single- valve gears.\\nGOVERNORS.\\nQ. What are the principal methods in use for\\ngoverning the speed of stationary engines\\nA. By the centrifugal governor acting on the\\nthrottle valve that is, by varying the initial pres-\\nsure in the cylinder to suit the load and by a\\ncentrifugal or inertia governor acting on the valve\\ngear in such a way as to vary the point of cut-off\\nto suit the load.\\nQ. Which is the better method, and why\\nA. The one in which the cut-off is varied to\\nsuit the load, because it is much more economical\\nin the use of steam, and the regulation is far\\nbetter. Moreover, engines in which the steam,\\npressure is throttled to suit the load often knock\\nviolently under light loads.\\nQ. Why should the steam never be throttled on\\nengines running at a high piston velocity?\\nA. Because the force necessary to accelerate the\\nreciprocating parts at the beginning of the stroke\\nis so great in high-speed engines that if the steam\\n14", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0231.jp2"}, "232": {"fulltext": "210 ROPER^S CATECHISM FOR\\nCENTRIFUGAL BALL GOVERNOR.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0232.jp2"}, "233": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 211\\nwere throttled the fly-wheel would have to supply\\nit, and hence there would be a reversal of pressure\\non the crank pin each stroke. This would not\\nonly cause very noisy running, but it would soon\\nwear out the engine.\\nQ. How is the governor usually made to vary\\nthe cut-off?\\nA. By a releasing mechanism, as already ex-\\nplained above (Corliss valve gear); by the action\\nof a ball governor on the block of a link, as in the\\nPorter- Allen engine; or by a shaft governor.\\nQ. What is a shaft governor\\nA. It is one in which the centrifugal action of\\na weight or weights, placed in a fly-wheel, is\\nbalanced against a spring or springs. The weights\\nare attached to pivoted arms, and these in turn to\\nthe eccentric of the valve gear. As the speed\\nincreases, the tendency is for the weights to move\\naway from the shaft and in so doing to alter the\\nposition of th-e eccentric, varying its angular\\nadvance or its throw, or both, and in this way\\naltering the point of cut-off.\\nQ. What is the difference in the effect on the\\nsteam distribution when the cut-off is varied by\\nthe angular advance and by the throw of the\\neccentric\\nA. If the angle of advance only is altered, the\\nlead will increase as the cut-off is decreased. If", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0233.jp2"}, "234": {"fulltext": "212\\nROPER S CATECHISM FOR\\nthe throw of the eccentric only is altered, the\\nreverse takes place. Hence, in order to keep the\\nlead constant with a single valve, both the throw\\nSHAFT GOVERNOR,\u00e2\u0080\u0094 BUCKEYE TYPE.\\n(A A are the weights attached to the ends of arms a a. The arms are\\npivoted to the fly-wheel at one end and attached to the loose eccentric C\\nat the other. FF are the springs which resist the tendency of the weights\\nto move away from the shaft. In this type of governor the angular\\nadvance only is varied.)\\nof the eccentric and the angular advance should\\nbe varied. In the governor illustrated above,\\nthis is not necessar}^, because a separate valve is\\nused to cut off the steam.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0234.jp2"}, "235": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 213\\nQ. How do you calculate the proper diameter\\nfor ball-governor pulleys\\nA. To find the diameter of governor shaft-pul-\\nleys Multiply number of revolutions of engine\\nby diameter of engine shaft-pulley, and divide\\nproduct by number of revolutions of governor.\\nTo find diameter of engine shaft-pulley Mul-\\ntipl}^ number of revolutions of governor by diam-\\neter of governor shaft-pulley, and divide product\\nby number of revolutions of engine.\\nINSTALLATION, CARE AND MANAGEMENT.\\nQ. What is the best material for engine founda-\\ntions\\nA. They should be of hard-burned brick laid\\nin Portland cement or of concrete.\\nQ. How deep should they be carried\\nA. The proper depth depends on the size of the\\nengine. The builders usually furnish a founda-\\ntion plan showing minimum depth, but they\\nshould always rest on solid ground.\\nQ. How should the foundation bolts and anchor\\nplates be placed in the foundation\\nA. A template should first be constructed to\\nhold the bolts in their proper positions and the\\nbolts suspended from the template. The bolts\\nshould be threaded at both ends and the lower nut\\nheld in a suitable pocket in the anchor plate. In", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0235.jp2"}, "236": {"fulltext": "214\\nROPER S CATECHISM FOR\\nbuilding the foundation a space should be left\\naround each bolt, sufficient to allow the bolt to be\\nmoved a half inch in any direction.\\nQ. How should the foundation be finished\\nA. A cap-stone of granite makes the best finish,\\nbut, as a rule, the expense is too great. After the\\nengine is set on the foundation and leveled by\\nmeans of iron wedges, the space between the\\nbottom of the engine and the top of the founda-\\ntion should be filled with grout or, preferably,\\nmolten sulphur, to give an even bearing.\\nQ. Should foundations be built the same width\\nfrom bottom and top\\nA. No; they should be wider at the bottom and\\nhave a slope or batter of about two inches to every\\nfoot of height up to the floor-level. The top\\nshould be about an inch wider than the bed plate\\nof the engine.\\nQ. How would you proceed to set up an engine\\nA. First. Determine the position or location\\nthe engine is to occupy in the shop or factory.\\nSecond. Lay out the line of the main shafting\\nin the building, if there be any; if not, the line\\nof the building itself, at, at least, three different\\npoints in the direction in which the main shafting\\nis to run; now line down from the center of the\\nmain shaft, or from the line of the building, at\\ntwo different points, to the floor on which the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0236.jp2"}, "237": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 215\\nengine is to stand, and from these points line to\\nthe engine-shaft.-\\nThird. Determine the height the bed-plate is\\nto stand above the floor; also the depth of the\\nfoundation.\\nFourth. Make a template the exact counterpart\\nof the bed-plate, in which to hang the foundation\\nbolts, and set this upon four props at right angles\\nto the main shaft in the building.\\nFifth. Lay up the brick foundation to the level\\nat which the engine is intended to stand; then\\nremove the template, and lower the bed-plate on\\nto the foundation.\\nSixth. Level the bed-plate by means of iron\\nwedges and pour in sulphur to give it an even\\nbearing. After that the nuts may be screwed\\ndown on the foundation bolts.\\nSeventh. A line should now be drawn exactly\\nthrough the center of the cylinder, and another\\nline through the center of the main bearing.\\nThis line will give the location of the pillow-block\\nor outboard bearing.\\nEighth. Place a straight edge across the bottom\\nof the bearings and adjust them with the aid of a\\nspirit level until they are perfectly level.\\nNinth.. Swing the fly-wheel into its proper\\nposition, slip the shaft through it and key it in\\nplace. Screw down the caps of the pillow-blocks.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0237.jp2"}, "238": {"fulltext": "216 roper s catechism for\\nTenth. Place the cross-head, connecting rod,\\netc., in position, bolt on the front cylinder head,\\nand adjust the valve gear.\\nQ. AVhat are the principal points which should\\nbe kept in mind in running the steam and exhaust\\npipes for an engine\\nA. They should be run in such a way that the\\nfree flow of steam will never be impeded. The\\nsteam- and exhaust-pipes should never be smaller\\nthan the outlets provided on the engine. The\\npipes should be run as straight as possible.\\nHorizontal runs should be slightly inclined to\\nallow the condensation to drain of! in the same\\ndirection as the flow of the steam. The piping,\\nif long, should have a suitable provision for\\nexpansion, and all steam- and exhaust-piping\\nshould be covered with some non-conducting\\npipe-covering.\\nQ. What is the first duty of an engineer in\\nregard to the steam engine\\nA. He should always keep it clean and free from\\nrust, oil, and grit. This does not involve a great\\ndeal of labor, and adds very materially to the life\\nof the engine.\\nQ. How should an engine be started\\nA. First see that the drips are all open. The\\ncylinder should then be warmed by slightly open-\\ning the throttle.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0238.jp2"}, "239": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 217\\nQ. How should the clrij^s be left when the\\nengine is not running\\nA. They should be left open so as to allow the\\ncondensed steam to escape.\\nQ. How do you pack stuffing-boxes\\nA. Before packing the piston- and valve-rods\\nall the old packing should be carefully removed.\\nThe new packing should be cut in suitable lengths,\\nand the joints placed at opposite sides of the box.\\nThe stuffing-box should then be screwed up until\\nthe leakage around the rod is stopped, and no\\nfurther, as any unnecessary tightening of the\\nstuffing-box will greatly diminish the power of\\nthe engine and soon destroy the packing by the\\nincreased friction. Piston-rod packing should\\nalways be kept in a clean place, as any dust or\\ngrit that may become attached to it has a tendency\\nto cut or flute the rod.\\nQ. What precautions should be taken with the\\npiston\\nA. The spring packing in the cylinder should\\nalways be kept up to its proper place, because if\\nallowed to become loose, the leakage materially\\nreduces the power of the engine. Setting out\\npacking- rings requires the exercise of great care,\\nbecause, if set too tightly, the friction produced\\nwill not only have a tendency to cut the cylin-\\nder, but will also perceptibly lessen the power", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0239.jp2"}, "240": {"fulltext": "218 roper s catechism for\\nof the engine. The piston should be removed\\nfrom the cylinder at least twice a year, and the\\njoints formed by the rings on the flange of the\\nhead and the follower-plate carefully ground with\\nemery and oil. If badly corroded, they should\\nbe faced up in a lathe and made perfectly steam-\\ntight.\\nQ. How should the spindle of a ball governor\\nbe packed\\nA. Great care should be taken, when packing\\nthe spindle of a governor, not to screw the pack-\\ning down too tightly, as that would interfere with\\nthe free movement of the governor. All the parts\\nof the governor should be kept perfectly clean and\\nfree from the gum formed by the use of inferior\\nqualities of lubricating oils.\\nQ. How should the engine be lubricated\\nA. All the surfaces subjected to friction should\\nbe provided with sight-feed oil-cups. These\\nshould be turned on as soon as the engine is\\nstarted and examined at frequent intervals, to see\\nthat the supply is not exhausted and to make sure\\nthat every cup is feeding correctly.\\nQ. Is it advisable to use as much oil as possible\\non an engine?\\nA. No more oil should be used on an engine\\nthan is absolutely necessary, as it is not only a\\nloss, but often detracts from the appearance of the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0240.jp2"}, "241": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 219\\nengine, and greatly interferes with its free and eas}\\nmovement, from the accumulation of gum and\\ndirt on its working parts.\\nQ. Suppose any part of the engine should heat,\\nwhat would be the proper thing to do\\nA. First examine the lubricator, and if it is\\nfound that the heated part has not been receiving\\nthe proper amount of oil, the trouble can usually\\nbe remedied by giving it a liberal supply. Some-\\ntimes it is necessary in a new engine to keep the\\nbearings cool, temporarily, with ice, although if\\nthey run very hot it is generally better to stop\\nthe engine if possible and determine the cause.\\nIn case the crank-pin should heat which is a\\ncommon occurrence with engines having a narrow\\nbearing on the pin, but more particularly with\\nengines that are slightly out of line remove the\\nkey and slacken the strap and box; then pour in\\nsome flour of sulphur with a liberal supply of\\noil; then adjust the key, and the trouble will\\ngenerally disappear. If the pillow-blocks of an\\nengine should heat badly, remove the cap and\\npour in a good supply of pulverized bath-brick\\nand water while the engine is in motion; after\\ndoing this for some time, wash out with oil, and\\nwipe the bearing clean with waste. In case any\\nof the bearings of an engine should heat through\\nthe accumulation of matter deposited from the oil", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0241.jp2"}, "242": {"fulltext": "220 roper s catechism for\\nused, or sand, grit, or whitewash being dropped\\ninto the bearings, use a strong solution of concen-\\ntrated lye with oil when the engine is in motion.\\nQ. Where should the tools and materials used\\nabout an engine be kept\\nA, They should be kept in a clean place.\\nNever set steam-packing, cotton-waste, tops of\\noil-cups, or anything that is to be used around the\\ncylinder, valves, piston-rod, or bearings of steam\\nengines, on the floor, as they will invariably pick\\nup sand or grit, which injure the rubbing and\\nrevolving surfaces with which they come in con-\\ntact.\\nQ. How should gum- joints be made?\\nA. If they frequently need to be taken apart,\\nthe gum should be well coated with pulverized\\nchalk or soapstone before being placed between\\nthe flanges. This prevents it from adhering to\\nthe metal and being destroyed when the joint is\\nbroken.\\nQ. What does a clicking noise in the cylinder\\nindicate\\nA, It frequently indicates the pressure of moist-\\nure, and it can generally be stopped b}^ opening\\nthe drip-cocks.\\nQ. What are some of the principal causes of\\nknocking in steam engines and the appropriate\\nremedies", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0242.jp2"}, "243": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 221\\nA. Knocking in engines generally arises from\\nthe following causes:\\nFirst. Lost motion in the boxes on the cross-\\nhead, crank-pin, and the pillow-blocks, and in\\nthe key of the piston-rod in the cross-head. To\\nstop it, take up lost motion by means of the key,\\nor file off the edges of the boxes, if brass-bound.\\nSecond. It is sometimes caused by the crank\\nbeing ahead of the steam, which in most cases can\\nbe relieved by moving the eccentric forward in\\norder to give more lead an the valve.\\nThird. Knocking is caused in many cases by\\ntoo much lead on the valve. The simplest remedy\\nfor this is to move the eccentric back so as to give\\nless lead.\\nFourth. Frequently it is caused by the exhaust\\nclosing too soon. The best remedy for this would\\nbe to enlarge the exhaust-chamber in the valve.\\nFifth. Insufficient clearance between the piston\\nand the cylinder-head at the end of the stroke.\\nThe remedy for this kind of knocking would be\\nto turn off the heads of the cylinder on the inside,\\nso as to give more clearance.\\nSixth. Knocking sometimes arises from the\\nwrist of the cross-head and the crank-pin becom-\\ning worn out of round. The most effective remedy\\nfor this cause is to turn up the crank- and wrist-\\npin.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0243.jp2"}, "244": {"fulltext": "222 roper s catechism for\\nSeventh. Insufficient counter-bore in cylinder.\\nIn such cases the piston-rings wear a shoulder at\\neach end of the cylinder, and whenever the keys\\nare driven or the packing-rings set out, the edges\\nstrike these shoulders and cause the engine to\\nknock. The most practical remedy for knocking\\narising from this cause is to recoimter-hore the\\ncylinder.\\nEighth. Knocking is sometimes caused by the\\nengine being out of line. The surest remedy for\\nthis kind of knocking would be to put the engine\\nexactly in line.\\nNinth. Sometimes it arises from shoulders be-\\ncoming worn on the ends of the guides in cases\\nwhere the gibs on the cross-head do not run over.\\nThe most reliable remedy for such knocking would\\nbe to replane the guides.\\nTenth. Knocking is sometimes caused by the\\nfollower-plate being loose. The best preventive\\nfor such knocking is to bring the bolts up tight.\\nTo do so, it is sometimes necessary to remove the\\ndeposit of rust or grease in the bottom of the holes.\\nEleventh. Very often it is caused by the pack-\\ning around the piston-rod being too hard and\\ntight. The most effectual remedy for that is to\\nremove all the old packing from the box and\\nreplace it with new, and only screw the box up\\nsufficiently to prevent the escape of steam. Too", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0244.jp2"}, "245": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 223\\nmuch friction on the rod is a great loss of power,\\nand has a tendency to destroy the packing.\\nTwelfth. The knocking heard in the steam-chest\\nis sometimes caused by lost motion in the jam-\\nnuts or yoke that forms the attachment between\\nthe valve and rod. The remedy for this would\\nbe to remove the cover of the steam-chest and re-\\nadjust the jam-nuts on the valve-rod.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0245.jp2"}, "246": {"fulltext": "224 roper s catechism for\\nADJUNCTS OF THE STEAM ENGINE.\\nTHE INDICATOR.\\nQ. What do you understand by the steam engine\\nindicator\\nA. An instrument which records the pressure\\nin the steam cylinder at every point of the stroke.\\nQ. Give a brief description of the instrument\\nand explain how this record is made.\\nA. The indicator consists essentially of a small\\nhollow cylinder which communicates with the\\nengine cylinder. A rod attached to the piston is\\nenclosed in a spiral spring which presses against\\nthe piston and opposes its motion. The end of\\nthe rod extends through the cover at the top of\\nthe cylinder, and is attached to a series of levers,\\ncalled a parallel motion^ in such a way that a\\npencil attached to the end of the long lever will\\nmove in a vertical straight line when the piston\\nascends. A second hollow cylinder, carried on\\nthe same frame as the first, and called the paper\\ndrum, is mounted on a vertical spindle, about\\nwhich it is free to rotate, but by the action of a\\nspring contained in it the drum tends to remain\\nin a fixed position. A groove, shown at the bot-\\ntom of the drum, carries a cord which is attached", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0246.jp2"}, "247": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS..\\n225\\nby means of a reducing motion to some of the\\nreciprocating parts of the engine, so that the\\npencil, when the engine is moving, would trace a\\nhorizontal line on the surface of the drum, which\\nwould represent the stroke of the engine. As the\\nSECTION OF TABOR S INDICATOR.\\npencil, however, is moved up and down by the\\npressure of the steam in the cylinder, it follows\\nthat, if a paper is placed around the drum, a\\ndiagram will be traced, representing the pressure\\n15", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0247.jp2"}, "248": {"fulltext": "226 roper s catechism for\\nin the cylinder at every point in the stroke. The\\nvertical height of any point in the diagram, from\\nthe bottom or atmospheric line, will represent the\\npressure, and the horizontal distances will repre-\\nsent the position of the piston.\\nQ. How would you proceed to take an indicator\\ndiagram\\nA. It is impossible to give directions which\\nwould apply to all makes of indicators. I should\\ncarefully read the directions given by the makers\\nof the particular type of instrument in my pos-\\nsession, and proceed accordingly.\\nQ. Sketch an indicator diagram and explain\\nwhat it means.\\nA. In the accompanying diagram the line A A\\nis the atmospheric line that is, it is the line\\ntraced by the pencil on the paper when the engine\\nis in motion before the indicator cylinder is placed\\nin communication with the engine cylinder.\\nHence its position represents the pressure of the\\natmosphere. The point B represents the position\\nof the pencil at the beginning of the stroke, and\\nhence the vertical height B A of this point above\\nthe atmospheric line A A represents the initial\\nsteam pressure in the cjdinder. The line B C\\nrepresents the distance traveled by the piston\\nduring the period of admission, and the point C,\\nwhere the first change in direction occurs, is the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0248.jp2"}, "249": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n227\\npoint of cut-off. Expansion now takes place in\\nthe cylinder and continues until the next change\\nin direction occurs at D, which is the point at\\nwhich the exhaust port begins to open. The\\nsteam is released from the cylinder, and the pres-\\nsure falls more rapidly until the end of the stroke\\nE, when it is about equal to that of the atmos-\\nHHhI\\nEXPLANATORY DIAGRAM.\\nphere. The piston then begins its return stroke\\nagainst the back pressure represented by the ver-\\ntical height of the line E F above the atmospheric\\nline A A. If the engine exhausts into the atmos-\\nphere, this height is generally very small, while\\nif it is a condensing engine, the back pressure\\nline E F will be below the atmospheric line A A,", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0249.jp2"}, "250": {"fulltext": "228 roper s catechism for\\nindicating a negative back pressure. At F the\\nexhaust closes and compression begins, which\\ncontinues until the end of the stroke G. The\\nsame cycle is then repeated, and so long as the\\nload, the initial pressure and the back pressure\\nremain the same, the diagram traced by each\\nsuccessive stroke will be practically the same.\\nFor the other end of the cylinder the diagram\\nwill be similar but reversed.\\nQ. What are the principal things that may be\\nascertained about an engine with the aid of the\\nindicator diagram\\nA. The information furnished by the indicator\\ndiagram is of the most important kind. It en-\\nables us to determine:\\nFirst. The power of the steam engine under all\\nconditions, or the power consumed by any one\\nmachine driven by the engine or by the engine\\nitself in overcoming the friction of its parts.\\nSecondly. The forward and back pressure on\\nthe piston at any point in the stroke.\\nThirdly. The average forward and back pres-\\nsure and the mean effective pressure on the piston.\\nFourthly. The positions of the piston when\\nsteam is admitted and cut off; the period of ex-\\npansion, exhaust, and compression; the action of\\nthe valves; and, in fact, all questions relating to\\nthe steam distribution.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0250.jp2"}, "251": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 229\\nQ. How is the power developed by the engine,\\nor the indicated horse-power calculated from the\\ndiagram\\nA. The indicated horse-power of the engine is\\nfomid by determining the mean effective pressure\\nfrom the diagram and using it in the rules and\\nformulae for horse-power given on pages 177-180.\\nQ. Explain how to find the mean effective\\npressure.\\nA. There are two methods in common use,\\none by the use of ordinates and the other by the\\nplanimeter. The latter method is more exact and\\nless laborious than the former, but as a plan-\\nimeter is not always available, the former method\\nis much used, especially for rough calculations.\\nTO DETERMINE THE MEAN EFFECTIVE\\nPRESSURE.\\nFirst Method. Draw vertical lines A B and A I\\ntouching the ends of the diagram (see page 227),\\nand apply a rule across them obliquely as shown\\nby the dotted line in the diagram in such a way\\nthat some division on the rule, as y^g-, or\\nwill divide the distance between the verticals just\\ndrawn an even number of times, preferably 20\\ntimes. Mark off points on this line, dividing it\\ninto equal parts excepting the first and last, which\\nare only one-half as large as the intermediate", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0251.jp2"}, "252": {"fulltext": "230 roper s catechism for\\nspaces, and draw vertical lines or ordinates\\nthrough these points, dividing the area enclosed\\nby the diagram as shown. Next take a long strip\\nof paper and apply its edge successively to each of\\nthe ordinates and mark their combined length on\\nit. This length multiplied by the scale of the\\nspring used and divided by the total number of\\nordinates will give the mean effective pressure.\\nThe length of the ordinates is measured between\\nthe forward- and back-pressure lines.\\nSecond Method. If a planimeter is used, it is\\nonly necessary to multiply the area enclosed by\\nthe diagram in square inches by the scale of the\\nspring, and divide the product by the length of\\nthe diagram in inches. The quotient will be the\\nmean effective pressure.\\nQ. What precautions must be taken if the indi-\\ncated horse-power is to be calculated very accu-\\nrately\\nA. The mean effective pressure must be calcu-\\nlated separately from the diagrams of the head-\\nand crank-ends of the cylinder. In doing this it\\nmust be remembered that the back-pressure line\\nof one diagram belongs to the forward-pressure\\nline of the other, and vice versa. While in most\\nengines in which the valves are properly adjusted\\nthe two back-pressure lines are identical, yet if\\nthe greatest accuracy is desired the mean effective", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0252.jp2"}, "253": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 231\\npressure should be calculated by deducting from\\nthe mean forward pressure as obtained from the\\nhead-end diagram, the mean back pressure as\\nobtained from the crank-end diagram, and vice\\nversa. It must further be borne in mind that the\\neffective area of the piston at the crank end is less\\nthan that at the head end by the area of the piston\\nrod. Hence the horse-power is different for the\\ntwo ends and should be calculated independently;\\nthe total horse-power of the engine being equal to\\nthe sum of the two.\\nQ. Suppose it is desired to find the horse-power\\nof an engine where the following dimensions and\\ndata are known:\\nStroke 36 inches.\\nDiameter of cylinder 24 inches,\\nSpeed 150 revolutions per minute,\\nDiameter of piston rod 4 inches.\\nThe engine having been indicated with a spring\\nwhose scale was 60 pounds per square inch, it was\\nfound with the aid of a planimeter that the areas\\nof the diagrams w^ere as follow^s:\\nHead end 3. 54 square inches,\\nCrank end 3.42 square inches,\\nLength of diagrams 3.27 inches.\\nCalculate the mean effective pressures and the\\nhorse-power of the engine.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0253.jp2"}, "254": {"fulltext": "232 roper s catechism for\\nA. The mean effective pressure, according to the\\nabove (second) method, is\\nHead end, 64.95 pomids,\\nCrank end, 62. 32 pomids.\\nThe area of the piston is\\n.7854 X 24 X 24 452.39 square inches,\\nand the area of the piston rod is\\n.7854 X 4 X 4 12.57 square inches.\\nHence the effective areas of the piston are\\nHead end, 452.39 square inches.\\n12.57\\nCrank end, 439.82\\nThe total mean pressures on the piston are\\nHead end, 452.39 X 64.95 29385 pounds,\\nCrank end, 439.82 X 62.32 27409 pounds.\\nThe piston speed is\\n36\\n12\\nand therefore the horse-power\\njr A A 29385 X 900\\nHeadend.\u00e2\u0080\u0094 33^^^\u00e2\u0080\u0094 ^801.4\\nT 27409 X 900\\nCrank end, 33000\\nTotal, 1548.9", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0254.jp2"}, "255": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 233\\nCONDENSERS.\\nQ. What do you understand by a condenser\\nA. An apparatus for condensing the exhaust\\n-steam of an engine, thereby reducing the back\\npressure and therefore increasing the power.\\nQ. How is this done\\nA. By bringing the steam under the influence\\nof cold water, either by bringing the two in direct\\ncontact or by allowing the steam to pass around a\\nseries of tubes through which the w^ater flows.\\nCondensers constructed on the first-named plan\\nare called jet condensers^ while the latter are termed\\nsurface condensers.\\nQ. What are the principal advantages and dis-\\nadvantages of the two types\\nA. Surface condensers have the advantage that\\nthe condensed steam is not mixed with the con-\\ndensing water. Hence they are generally used on\\nshipboard so that the condensed steam may again\\nbe used in the boilers. The vacuum is also\\ngenerally higher in surface than in jet condensers,\\nbut they have the disadvantage of being heavier\\nand much more expensive to construct than jet\\ncondensers. The tubes are also liable to become\\nleaky and impair the vacuum.\\nQ. At what temperature should jet condensers\\nbe kept?", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0255.jp2"}, "256": {"fulltext": "234 roper s catechism for\\nA. About 100\u00c2\u00b0 Fahr., at which temperature\\nthey have been found to operate most efficiently.\\nQ. What degree of vacuum should exist in a\\ngood condenser\\nA. From 20 to 26 inches.\\nQ. What do you mean by 26 inches of vacuum\\nA. As the atmospheric pressure will support a\\ncolumn of mercury about 30 inches in height,\\neach inch of the mercury column would be equiv-\\nalent to a pressure of about pound. A complete\\nvacuum (which can never exist) would be a\\nvacuum of 30 inches, corresponding to a pressure\\nof pound per square inch; 20 inches of vacuum\\nwould be one-third less vacuum or one-third of\\nthe atmospheric pressure that is, 5 pounds per\\nsquare inch absolute pressure. Hence to find the\\nabsolute pressure in pounds per square inch,\\ndeduct one-half of the vacuum in inches from the\\npressure of the atmosphere. Thus 15 inches of\\nvacuum would be, 15 15 X i 7J- pounds\\nper square inch absolutely.\\nQ. How much power is gained by the use of\\nthe condenser?\\nA. From 20 to 30 per cent., depending on the\\ntype and size of the engine.\\nQ. How much water is required for condensers\\nA. About 25 times the quantity evaporated in\\nthe boiler.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0256.jp2"}, "257": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n235\\nTABLE\\nSHOWING VACUUM IN INCHES OF MERCURY AND POUNDS\\nPRESSURE PER SQUARE INCH.\\nMercury.\\nFounds,\\nMercury.\\nPounds.\\n2.037\\n1\\n16.300\\n8\\n4.074\\n2\\n18.337\\n9\\n6.111\\n3\\n20.374\\n10\\n8.148\\n4\\n22.411\\n11\\n10.189\\n5\\n24.448\\n12\\n12 226\\n6\\n26.485\\n13\\n14.263\\n7\\n28.552\\n14", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0257.jp2"}, "258": {"fulltext": "236 eoper s catechism for\\nMATERIALS AND THEIR PROPERTIES.\\nQ. Of what is all matter made up\\nA. Of chemical elements.\\nQ. What are chemical elements\\nA. Substances having certain definite and pecu-\\nliar properties which, so far, chemists have not\\nbeen able to split up into simpler substances, and\\nwhich it is presumed cannot be further split up.\\nQ. What are some of the elements\\nA. Among the metals Iron, Copper, Lead, Tin,\\nZinc, Silver, Gold, and Platinum. Among the\\nnon-metals are: Antimony, Bismuth, Silicon, Sul-\\nphur, and Carbon. Among those which exist nor-\\nmally in the gaseous condition are: Hydrogen,\\nOxygen, Nitrogen, and Chlorine.\\nQ. What are the substances called which are\\nmade up by the chemical combination of two or\\nmore elements?\\nA. Compounds, as, for example, Water, which\\nis a compound of Oxygen and Hydrogen; Ammo-\\nnia, which is a compound of Nitrogen and Hydro-\\ngen; Carbonic Acid, which is a compound of Car-\\nbon and Oxygen; Zinc Oxide, which is a compound\\nof Zinc and Oxygen; and common Salt, which is\\na compound of Sodium and Chlorine.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0258.jp2"}, "259": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 237\\nQ. What are the molecules of a substance\\nA. The smallest particles mto which a substance\\ncan be divided without these particles losing any\\nof the distinctive properties of the substance.\\nQ. Have you any idea as to whether molecules\\nare visible under the microscope\\nA. They are not. Were the magnifying power\\nin any way much increased, they would still be\\ntoo small to be seen. Our ideas as to their exist-\\nence are derived not from sight, but from a variety\\nof chemical phenomena.\\nQ. Is it conceived that there are particles even\\nsmaller than molecules\\nA. Yes, the so-called atoms. It is believed that\\neach molecule of a compound substance is made\\nup of the atoms of the elements contained in the\\ncompound. For example, the molecule of salt is\\nsupposed to be made up of an atom of sodium\\njoined to an atom of chlorine, and the water mol-\\necule is supposed to be made up of two hydrogen\\natoms joined to one oxygen atom. The molecules\\nof the elements are supposed to be made up of\\ntwo or more atoms of that element.\\nQ. What is meant by the term atomic weight\\nof a substance\\nA. It is found experimentally that the elements\\ncombine with each other in certain fixed propor-\\ntions or in multiples of them. The figures which", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0259.jp2"}, "260": {"fulltext": "238 roper s catechism for\\nrepresent these proportions (hydrogen bemg used\\nas the standard and its combining weight called\\none are called the atomic weights. For ex-\\nample: Experiment shows that hydrochloric acid\\nis made up of 35.4 parts b}^ weight of chlorine to\\n1 part by weight of hydrogen; and that in other\\nchlorine compounds the proportion of chlorine is\\nrepresented either by 35.4 or by some multiple of\\nit, as 35.4 X 2, 35.4 X 3, etc. Thus, salt is made\\nup of 35.4 parts by weight of chlorine to 23 parts\\nby weight of sodium.\\nQ. What is supposed as to the construction of\\nsubstances according to the molecular theory\\nA. Every substance is supposed to be made up\\nof an immense number of molecules, which, even\\nin the solid state, are never entirely at rest, and\\nin the gaseous state are in perpetual violent com-\\nmotion, rushing about in straight lines in all di-\\nrections with enormous rapidity.\\nQ. What are the principal properties of metals\\nA. Their malleability, or capability to stand ham-\\nmering; their ductility, or power of being drawn\\nout into wire; their tenacity, or strength; their\\nhardness their fusibility, or ease of melting; and\\ntheir relative weight, or specific gravity.\\nQ. Name some of the most malleable of the\\ncommon metals.\\nA. Gold, Silver, Aluminum, Copper, Tin, Lead.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0260.jp2"}, "261": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 239\\nQ. Name the most ductile.\\nA. Platinum, Silver, Iron, Copper, Gold.\\nQ. What are some of the strongest\\nA. Iron, Copper, Aluminum, Platinum, Silver.\\nQ. What are some of the least fusible\\nA. Platinum, Iron, Copper.\\nQ. AVhat are some of the heaviest, or which\\nhave the greatest specific gravity\\nA. Platinum, Gold, Lead, Copper, Iron.\\nQ. How would you define the specific gravity\\nof a substance\\nA, The ratio of its weight to the weight of an\\nequal bulk of water.\\nQ. How would you find the specific gravity of\\na solid body\\nA. If it is heavier than water, weigh it in air\\nand then weigh it suspended in water. The dif-\\nference in weight is the weight of an equal bulk\\nof water. Divide the weight in air by the weight\\nof the equal bulk of water and the quotient is the\\nspecific gravity.\\nIf the body floats put just the weight oil it that\\nis necessary to make it sink even with the surface\\nof the water. Then from the sum of this weight\\nand the weight in air subtract the weight in water.\\nThe difference is the weight of an equal bulk of\\nwater. Divide the weight in air by this and the\\nquotient will be the specific gravity.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0261.jp2"}, "262": {"fulltext": "240 eoper s catechism for\\nQ. How would you measure the specific gravity\\nof a liquid\\nA. Take a vessel filled with it and weigh it.\\nThen weigh the same vessel filled with water.\\nDivide the weight of the substance by the weight\\nof the water and the quotient will be the specific\\ngravity.\\nQ. Is there any simple instrument for testing\\nthe specific gravity of liquids\\nA. Yes; the hydrometer, which consists of a\\ngraduated tube of small diameter attached to a\\nbulb containing air enough to make it float. Just\\nbelow this air chamber is a small bulb containing\\nenough mercury to keep the apparatus upright.\\nThe graduations on the tube give the specific grav-\\nity of the liquid in which the hydrometer is placed.\\nQ. Is water used as the standard of specific\\ngravity for gases\\nA. No; air at a standard temperature of 32\u00c2\u00b0\\nFahr. and at a pressure corresponding to the at-\\nmosphere at sea level.\\nCOMMON METALS.\\nQ. What are the varieties of iron\\nA. Wrought iron, cast iron, and malleable iron.\\nQ. What is steel?\\nA. A modification of iron, it being a combina-\\ntion of iron with varying percentages of carbon.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0262.jp2"}, "263": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 241\\nQ. What are some of the properties of wrought\\niron?\\nA. It is tough, malleable, ductile, fibrous, and\\ncan be welded.\\nQ. How does cast iron differ from wrought\\niron\\nA. It contains carbon, sulphur, silicon, phos-\\nphorous and other impurities. It is crystalline\\nin structure, is neither malleable, ductile, nor\\ntenacious, but has the very important property of\\nallowing itself to be cast.\\nQ. What is malleable iron\\nA. Cast iron annealed amid iron oxides.\\nQ. What are its properties\\nA. It is much more ductile than cast iron and\\nhas a higher tensile strength, though far inferior\\nin both respects to wrought iron and steel.\\nQ. What are the properties of steel\\nA. Steel partakes of the properties of both\\nwrought and cast iron, as some steels can be cast\\nand others welded. By varying the percentage of\\ncarbon in its composition its characteristics can be\\nwidely changed. It can be made soft and ductile\\nor hard and brittle. Steel also has the important\\nproperty of teinpermg, or being artificially hard-\\nened by sudden changes of temperature.\\nQ. What effect on the strength of steel does an\\nincrease of the percentage of carbon have\\n16", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0263.jp2"}, "264": {"fulltext": "242 roper s catechism for\\nA. It increases the strength of steel.\\nQ. What effect does it have on the ductihty of\\nsteel?\\nA. The ductility is diminished.\\nQ. At about what temperature is iron red hot\\nA. At about 1000\u00c2\u00b0 Fahr.\\nQ. At about what temperature does iron melt\\nA. At about 3000\u00c2\u00b0 Fahr.\\nQ. How much is iron expanded when its tem-\\nperature is raised from freezing point to boiling\\npoint\\nA. About -glo of its length.\\nQ. AVhat is the effect of a rise of temperature\\non the strength of iron\\nA. It increases nearly to about 600\u00c2\u00b0 Fahr.,\\nafter which it falls. At 1000\u00c2\u00b0 Fahr. its strength\\nis about half the maximum.\\nQ. How does copper compare with iron in its\\nprincipal qualities?\\nA. It is more malleable and more ductile. Its\\ntensile strength is a little less than one-half. Its\\nspecific gravity is a little greater. It is a much\\nbetter conductor for heat and electricity, its elec-\\ntrical conductivity being about six times that of\\niron.\\nQ. How is the tensile strength affected by heat\\nA. It is diminished, disappearing entirely at\\nabout 1300\u00c2\u00b0 Fahr.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0264.jp2"}, "265": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 243\\nQ. What is the temperature at which copper\\nmelts?\\nA. At about 2000\u00c2\u00b0 Fahr.\\nQ. In what form is copper mostly used\\nA. In the form of sheets and wires.\\nQ. In what other ways is it largely used\\nA. In combination with other metals forming\\nalloys.\\nQ. What are some of the principal alloys\\nA. Brass, Bronze, and German Silver.\\nQ. What is the composition of brass\\nA. It varies with the purpose for which it is to\\nbe used. Ordinary brass in foundries consists of\\n2 parts copper to 1 part zinc. A little tin or lead\\nis sometimes added, but essentially brass is an\\nalloy of copper and zinc.\\nQ. What is bronze\\nA. Bronze is essentially an alloy of copper and\\ntin, consisting of about 8 parts copper to 1 part\\ntin.\\nQ. What is German Silver\\nA. An alloy of copper and zinc, having a com-\\nposition of about 3 parts copper to 1 part zinc.\\nQ. What are some of the striking properties of\\nlead?\\nA. Its softness and malleability and its lack of\\nelasticity. A very valuable property is that it is\\nnot readily oxidized nor attacked by acids.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0265.jp2"}, "266": {"fulltext": "244 roper s catechism for\\nQ. For what purposes is it largely used\\nA. In sheets, pans, and pipes and as a constit-\\nuent of paints.\\nQ. How does it compare, in tensile strength,\\nwith iron\\nA. Its tensile strength is very small indeed in\\ncomparison with that of iron.\\nQ. What is its melting point?\\nA. About 600\u00c2\u00b0 Fahr.\\nQ. What is its specific gravity\\nA. About 11, nearly double that of iron.\\nSTRENGTH OF MATERIALS.\\nQ. What do you understand by the breaking\\nstrength of a substance\\nA. The force, in pounds per square inch, that\\nmust be exerted to break a specimen of that sub-\\nstance when it is placed in a suitable testing\\nmachine. The breaking strength may be either\\ntensile or compressive.\\nQ. What is the tensile strength\\nA. The number of pounds necessary to pull\\nasunder the test piece of 1 square inch cross-sec-\\ntion, the force being applied in a line perpendicu-\\nlar to the plane of the section.\\nQ. What is the compressive strength\\nA. The number of pounds that must be applied\\nto crush the test piece.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0266.jp2"}, "267": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 245\\nQ. What is the tensile strength of cast iron\\nA. About 16,000 pounds per square inch.\\nQ. What is the compressive or crushing\\nstrength\\nA. About 100,000 pounds.\\nQ. What are the tensile and compressive\\nstrengths of wrought iron\\nA. They are about the same, viz. 50, 000 pounds.\\nQ. What can you say of the strength of steel\\nA. It may be made to have almost any value, by\\nvarying the composition, from 50,000 to 200,000\\npounds per square inch. The great increase in\\nstrength is accompanied by brittleness.\\nQ. What are the strengths of oak and pine\\nA. Tensile about 7000 pounds and compressive\\nabout 3500 pounds per square inch.\\nQ. In calculating the sizes of pieces, either\\nmetal or wood, are the above figures used without\\nany allowance for uncertainties?\\nA. No; we make use of what is termed a Factor\\nof Safety. We assume that the load coming on\\nthe piece is a certain number of times greater\\nthan it really is and calculate the size of the piece\\naccordingly. The ratio between the assumed load\\nand the real load is the Factor of Safety.\\nQ. What values are used for the factor of\\nsafety\\nA. This depends entirely upon the nature of", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0267.jp2"}, "268": {"fulltext": "246 roper s catechism for\\nthe load. If it is steady, with no vibration as in\\nthe roofs of houses, the factor is taken as three.\\nWhen the load is fairly nniform, but with vibration,\\nas in the case of shafting hung from the roof trusses,\\nthe factor should he four. If the direction of the\\nload is reversed, putting the piece in alternate ten-\\nsion and compression, the factor should be six.\\nQ. Suppose it were desired to hang a weight of\\n50,000 pounds on the lower end of a wrought-iron\\nrod. What should be the area of the cross-section\\nof the rod\\nA. This is a case of a steady load where the\\nfactor of safety to be used is three. Multiplying\\nthe actual load by 3 we obtain 150,000 pounds as\\nthe load to be assumed. The tensile strength of\\nwrought iron being about 50,000 pounds per\\nsquare inch, it is evident that we must have a\\nsection of 150,000 50,000, or 3 square inches.\\nQ. On what does the weight that a beam will\\nsupport, depend?\\nA. On the length of the beam between the\\npoints of support, on its width and depth, and\\non the manner of application of the load.\\nQ. What difference does it make as to the\\nmanner of loading the beam\\nA. It will support a much greater load if it is\\nuniformly loaded than if the load is applied at\\none point.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0268.jp2"}, "269": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 247\\nQ. What do you mean by a uniformly loaded\\nbeam\\nA. A beam is uniformly loaded when the weight\\nper square inch resting on it is the same at all\\nparts of its length.\\nQ. When a beam is supported at both ends, at\\nwhat point will a given load break the beam most\\nreadily\\nA. At the middle of the beam.\\nQ. What is the difference between the load\\nwhich if applied in the middle will break a beam,\\nand the load needed to break it if it is uniformly\\ndistributed\\nA. A given beam will support a uniformly\\ndistributed load twice as great as that which will\\nbreak it if it is applied at the middle.\\nQ. Can the values for crushing strength be safely\\nused in all cases\\nA. Not when the length of the piece in com-\\npression has a length greater than four times a\\ndiameter. When this is the case the piece\\nbecomes a column, and a bending action comes\\ninto play, causing the piece to break long before\\nthe load corresponding to the compressive strength\\nhas been reached.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0269.jp2"}, "270": {"fulltext": "248 roper s catechism for\\nELECTRICITY*\\nSeven simple experiments contain the funda-\\nmental principles on which nearly all electrical\\napparatus depends.\\nExperiment 1. Place in a jar containing a solu-\\ntion of chromic acid a plate of zinc and a plate\\nof carbon. The plates should be near each other\\nwithout actually touching, and each should have\\nfastened securely to it a short piece of small\\ncopper wire. Place in another glass jar a solution\\nof copper sulphate and let the ends of the copper\\nwires dip into the copper sulphate solution with-\\nout touching each other.\\nQ. AVhat will happen to that part of the copper\\nwires dipping into the solution\\nA. The wire attached to the carbon plate will\\nbe gradually eaten away, while the wire attached\\nto the zinc plate will increase in size by an equal\\namount.\\nQ. AVhat is deposited on this wire to increase\\nits size\\nA. Pure copper.\\nQ. Suppose this wire were made of some other\\nmaterial than copper, would copper be deposited\\non it?\\nA. Yes; if made of iron, zinc, lead, or carbon.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0270.jp2"}, "271": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 249\\nQ. What does this experiment seem to show\\nA. That there has been set up a current of\\nsomething which apparently carries copper along\\nwith it.\\nQ. What name has been given to this current\\nA. The electric current.\\nQ. Could other plates than zinc and carbon be\\nused to jjroduce it\\nA. Yes; though zinc is generally used for one\\nof the plates.\\nQ. Could another solution than chromic acid\\nbe used\\nA. Yes; the solution must be one which readily\\nattacks one of the plates, and it is usually some\\nstrong acid.\\nQ. What is the apparatus called in which an\\nelectric current is produced by chemical action\\nA. A battery cell, or, simply, a cell.\\nQ. What is a battery\\nA. Properly speaking, a battery means several\\ncells, but it is often used to mean simply one\\ncell.\\nQ. What is the wire called to which copper is\\ncarried\\nA. The kathode.\\nQ. What is the wire called from which copper\\nis taken\\nA. The anode.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0271.jp2"}, "272": {"fulltext": "250 eoper s catechism for\\nQ. In which direction does the current flow in\\nthe copper sulphate solution\\nA. From the anode to the kathode.\\nQ. Is there a current flow through the cell con-\\ntaining chromic acid\\nA. Yes; resulting in taking zinc from the zinc\\nplate and carrying it into solution.\\nQ. Suppose one of the copper wires were cut,\\nwhat effect would this have on the flow of current\\nA. It would stop completely the action described\\nabove.\\nQ. What does this show\\nA. That what is called the electric current was\\nflowing around through a path or circuit, starting,\\nsay, at the carbon plate, thence through the copper\\nAvire attached to that plate to and through the\\nsolution of copper sulphate, then through the\\nother wire to the zinc plate, and finally through\\nthe chromic acid solution back to the carbon\\nplate. Any interruption of this circuit stops the\\nflow of current.\\nQ. Would pulling one of the wires out of the\\ncopper sulphate solution have the same effect as\\ncutting the wire\\nA. Yes.\\nQ. Of what electrical industry is this experi-\\nment the basis\\nA. Electro-plating.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0272.jp2"}, "273": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 251\\nExperiment 2. Pull the copper wires out of the\\ncopper sulphate solution and touch them together.\\nQ. What will be observed\\nA. The wires become heated.\\nQ. Equally all along their length\\nA. Apparently so.\\nQ. Is the zinc plate being dissolved as in Ex-\\nperiment 1\\nA. Yes.\\nQ. What does this experiment show\\nA. That the electric current heats bodies through\\nwhich it passes.\\nQ. Suppose the wire connecting the zinc and\\ncarbon plates is made longer, what will occur\\nA. The heating will be less.\\nQ. And if the wire is made shorter\\nA. The heating effect is much greater.\\nQ. What would you infer from this\\nA. Since a decrease in the heating means a\\ndecrease in the current, and since this was caused\\nby lengthening the wire, it would seem that the\\nwire opposes a resistance to the flow of the elec-\\ntric current, and that the longer the wire the\\ngreater the resistance which it offers.\\nQ. Can you think of any electrical apparatus\\nworking on the principle shown in this experiment\\nA. Electric heaters and certain electric measur-\\ning-instruments.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0273.jp2"}, "274": {"fulltext": "252 roper s catechism for\\nExperiment 3. Bring a compass needle or a\\nfreely suspended bar magnet near the wire in Ex-\\nperiment 2.\\nQ. What will be observed\\nA. The magnet is evidently acted upon by some\\nforce due to the current flowing through the wire.\\nAfter oscillating it comes to rest, pointing cross-\\nways to the wire and nearly perpendicular to it.\\nQ. Is this the case all along the wire\\nA. Yes.\\nQ. Why does the needle not stand exactly per-\\npendicular to the wire\\nA. Because normally it tends to point north.\\nThe current through the wire tends to make it\\nstand perpendicular to the wire. It actually takes\\na direction between these two.\\nQ. Notice which way the north-seeking pole of\\nthe magnet points. Now, if the magnet is held\\nfirst above the wire and then below, what occurs\\nA. Although the needle tends to stand in a\\ndirection cross- ways to the length of the wire, yet\\nwhen above the wire the north-seeking pole points\\nin one direction, and when below the wire in the\\nopposite direction.\\nQ. Is there any rule for telling in what direction\\nit will point?\\nA. Yes, one known as Ampere s rule, which is:\\nImagine yourself swimming with the current and", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0274.jp2"}, "275": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. Zo6\\nturned either on your side, face, or hack, so as to look\\nat the magnet. Then the north-seeking pole of the\\nmagnet luill point toivard your left.\\nQ. In the above experiment, suppose that the\\nwire carrying the current is free to move while\\nthe magnet is fixed, what will occur\\nA. The Avire will move either toward or away\\nfrom the magnet, according as one pole or the\\nother of the magnet is presented to it.\\nQ. What does this show?\\nA. That there is a force existing between a\\nmagnet and a wire carrying a current, similar to\\nthe force existing between two magnets. Further\\nexperiment shows that the strength of this force\\ndepends on the nearness of the magnet to the wire\\ncarrying current, and that the direction of the force\\ndepends on the position of the wire with respect\\nto the two poles of the magnet.\\nQ. Can this magnetic force be represented con-\\nveniently by lines as in the case of other forces\\nA. Yes. We conceive that around every mag-\\nnet or wire carrying current lines could be drawn\\neither straight or curved, which at any point of\\ntheir length should represent the direction of the\\nresultant magnetic force at that point.\\nQ. How could you actually lay out the lines of\\nforce due to any magnet, say a bar magnet\\nA. If we could obtain a north-seeking pole of a", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0275.jp2"}, "276": {"fulltext": "254 roper s catechism for\\nmagnet without its accompanying south-seeking\\npole, we could place it near the north-seeking pole\\nof the bar magnet and observe the path which it\\npursued from the north pole to the south pole and\\nplot this path on paper. We would then place\\nthe test pole at another point of the north pole of\\nthe bar magnet, and again observe the path and\\nplot it, and so on. In this way the space around\\nthe magnet could be mapped out.\\nQ. What is the space around a magnet, in\\nwhich magnetic force exists, called?\\nA. The field of that magnet.\\nQ. Does every magnet have a field\\nA. Yes; and since lines of force could be drawn\\nin this field which would represent the direction\\nof magnetic force, we say that every magnet pro-\\nduces lines of force.\\nQ. What, then, is a line of force\\nA. It is a line which represents the direction of\\nmagnetic force in the region where the line is\\ndrawn or may be supposed to be drawn.\\nQ. What is the positive direction of the line of\\nforce\\nA. That direction in which a free north-seeking\\nmagnetic pole would move. A free south pole\\nwould move in the opposite direction.\\nQ. Since we cannot obtain a free north pole for\\ntesting the direction of magnetic force, how can", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0276.jp2"}, "277": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 255\\nwe explore and map out the magnetic field due to\\nany magnet or wire carrying current\\nA. By taking advantage of the fact that a short\\nmagnet will, if free to move, place itself length-\\nwise along the lines of force.\\nQ. Explain how the experiment is performed.\\nA. Place under a piece of window-glass a bar\\nmagnet, and dust on the\\nupper side of the glass\\nsome iron filings. These\\nfilings become magnets\\nwhich are exceedingly\\nshort, and when they are\\njarred by tapping the glass\\nthey are free to move\\nand set themselves into\\nlines corresponding to the\\nlines of magnetic force as shown in the cut.\\nQ. Why are the lines of filings more dense at\\nsome points of the field than at others\\nA. Because the strength of the magnetic force\\nis greater at those portions of the field.\\nQ. How would you describe the lines of force\\ndue to a bar magnet\\nA. As curved lines running from the north pole\\nto the south pole.\\nQ. What are the lines of force due to a horse-\\nshoe magnet", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0277.jp2"}, "278": {"fulltext": "256\\nroper s catechism for\\nA. Principally straight lines from the north to\\nthe south pole.\\nQ. How can you obtain the field due to a cur-\\nrent in a straight wire\\nA. By drilling a hole in the piece of glass and\\npassing the wire vertically through this hole and\\nthen dusting on iron filings.\\nQ. AVhat are the lines of force due to a current\\nin a wire\\nA. Circles concentric with the axis of the wire,\\nthe positive direction be-\\ning in the direction in\\nwhich the hands of a\\nwatch move.\\nQ. Where is the mag-\\nnetic force greatest\\nA. Next to the wire, as\\nshown by the greater den-\\nsity of the lines of force.\\nQ. Suppose the current\\nthrough the wire were greatly increased, how\\nwould the density of the lines be affected\\nA. It would be increased in the same proportion\\nas the magnetic effect of the current is strictly\\nproportional to the strength of the current.\\nQ. When a coil of wire carrying a current is\\nbrought near a magnet, can the direction of\\nmotion of the coil or magnet be told in advance", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0278.jp2"}, "279": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 257\\nA. Yes; they will move in such a way that the\\ngreatest possible number of lines of force due to\\nthe magnet will pass through the coil.\\nQ. For what practical purpose can this principle\\nof the effect of an electric current on a magnet be\\nused\\nA. AYe can detect currents in wires by bringing\\na magnet near. the wires, and can also, by applying\\nAmpere s rule, determine in which direction the\\ncurrent flows.\\nQ. Is there any other method of determining\\nthe direction of flow of a current.\\nA. Yes; by making use of the principle illus-\\ntrated in Experiment 1. The current can be led\\ninto a solution of copper sulphate (or nearly any\\nsolution of a metallic salt), and by noting which\\nof the wires increases in size we can tell in which\\ndirection the current flows, as it flows toivard the\\nwire which has copper deposited on it.\\nQ. Can we increase the effect of the current on\\nthe magnet\\nA. Yes, in three ways By increasing the\\nstrength of current, by bringing the wire and the\\nmagnet nearer together, and by winding the wire\\nwhich carries the current in a coil and placing the\\nmagnet in the axis of the coil.\\nQ. When this is done, what direction will the cur-\\nrent in the coil tend to make the magnet assume\\n17", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0279.jp2"}, "280": {"fulltext": "258 roper s catechism for\\nA, A direction parallel to the axis of the coil.\\nSince the magnet is also acted on by the earth s\\nmagnetism tending to make it point north, it will\\nactually assume a position between these two\\ndirections. The angle which it makes with north\\ndepends on the relative strength of the earth s\\nmagnetic force and the magnetic force due to the\\ncoil. AVith no current passing through the coil\\nthe magnet points due north. When a small cur-\\nrent passes through the coil the magnet is slightly\\ndeflected. A larger current deflects it more, and\\nso on.\\nQ. What is the apparatus called which consists\\nof the coil of wire and pivoted magnet described\\nabove?\\nA. A galvanometer.\\nQ. For what purposes should you say that the\\ngalvanometer would be useful\\nA. For detecting the presence of electric cur-\\nrents, determining in which direction they flow\\nand also to nxeasure their strength.\\nExperiment 4- Connect to a galvanometer, as\\ndescribed above, the terminals of an auxiliary\\ncoil of wire placed a few feet distant, the connec-\\ntion being made by leading a wire from one end\\nof the auxiliary coil to one end of the galvanom-\\neter coil, and another wire from the other end of\\nthe auxiliary coil to the other end of the galvanom-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0280.jp2"}, "281": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 259\\neter coil. Bring a strong magnet near the auxil-\\niary coil, watching at the same time the magnet\\nneedle of the galvanometer.\\nQ. What occurs?\\nA. The magnet needle gives a sudden jump\\nand continues to oscillate to and fro, coming to\\nrest a little while after the motion of the strong\\nmagnet has stopped.\\nQ. What does this show\\nA. The jump of the galvanometer needle shows\\nthat an electric current has been produced by\\nmoving the magnet near the auxiliary coil. The\\nfact that after the magnet stops the needle comes\\nto rest in its original position, shows that the cur-\\nrent is produced only while the magnet is moving.\\nQ. Suppose that instead of moving the magnet\\ntoward the auxiliary coil, the coil is moved\\ntoward the magnet\\nA. The galvanometer needle jumps in the same\\ndirection as before, showing that current is pro-\\nduced in the same way and in the same direction.\\nQ. Suppose that the magnet and coil are moved\\naway from each other?\\nA. The needle jumps as before, but in the\\nopposite direction.\\nQ. What do you conclude from all this\\nA. That moving a wire and a magnet relatively\\nto each other produces an electric current, and", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0281.jp2"}, "282": {"fulltext": "260\\nROPER S CATECHISM FOR\\nthat the direction of the current depends on the\\ndirection of the motion.\\nQ. Has the current so produced the same\\nproperties as the current produced by a battery\\nA. Absolutely the same; the two are identical.\\nQ. What piece of electric apparatus is based on\\nthe principles illustrated by this experiment\\nA. The dynamo.\\nQ. Making use of the idea of lines of force in\\nthe above experiment, what result do you arrive at\\nA. Moving the magnet nearer the coil causes\\nthe coil to cut across lines of force due to the\\nmagnet, and since a current is produced by the\\nmotion we may conclude that ivhenever an electric\\nconductor cuts across lines of force an electric current\\nis produced.\\nQ. When the magnet was moved away there\\nwas a current produced in the opposite direction\\nby the cutting of lines of force. Is there any\\nconvenient rule for de-\\ntermining the direction\\nof the induced current\\nA. Yes; a rule known\\nion of as Fleming s.\\nPoint the forefinger along\\nthe positive direction of the\\nmagnetic lines and point\\nthe thumb stretched at right", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0282.jp2"}, "283": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 261\\nangles in the direction in ichich the conductor moves.\\nIf now the second finger he stretched at right angles\\nto both thumb and forefinger, it will point in the direc-\\ntion of the induced current.\\nQ, When the magnet is moved nearer the coil,\\nthe number of Hnes of force due to the magnet,\\nwhich is enclosed by, or which passes through, the\\ncoil, is increased, might we not say that a cur-\\nrent is produced w^henever the number of lines\\nenclosed by a coil is changed\\nA. Yes; and when the conductor is in the form\\nof a coil this idea is of great value. Looking along\\nthe positive direction of the lines of force, when the\\nnumber enclosed by the coil is increased, the cur-\\nrent around the coil is left-handed as we look at it.\\nIf the number enclosed by the coil is diminished,\\nthe current will be right-handed as we look at it.\\nQ. What do you mean by right-handed\\nA. In the direction in which the hands of a\\nwatch move.\\nExperiment 5. If the current from a battery or\\nother current generator be led through a wire\\nAvhich is coiled around a rod of iron, the iron\\nbecomes strongly magnetized, as we say that is, it\\nexhibits all the properties of a magnet. It at-\\ntracts other pieces of iron, and it has polarity,\\none end attracting the north-seeking pole of a bar\\nmagnet and the other end repelling it.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0283.jp2"}, "284": {"fulltext": "262 roper s catechism for\\nQ. What is the combination of a piece of iron\\nwith a coil of wire around it called\\nA. An electro-magnet.\\nQ. After current is cut off from the coil, does\\nthe iron still exhibit magnetic qualities\\nA. Only feebly. The magnetism still remain-\\ning is called permanent or residual magnetism.\\nQ. What is the advantage of an electro-magnet\\nover a permanent magnet\\nA. For the same size the electro-magnet is\\nmuch more powerful.\\nExperiment 6. Suspend a coil of wire so that\\nit can turn freely and lead a current through the\\nwire. Then bring a magnet near it.\\nQ. Will the coil be affected by the magnet\\nA. Yes, the coil will turn so as to enclose as\\nmany as possible of the lines of force due to the\\nmagnet and will finally come to rest in that position.\\nQ. Suppose the other pole of the magnet be\\npresented toward the coil\\nA. The coil will turn in the opposite direction\\nand come to rest in such a position that it encloses\\nthe greatest possible number of lines of force due\\nto the magnet.\\nQ. Suppose just at the moment the coil gets\\ninto the position of enclosing the maximum num-\\nber of lines the current is reversed in direction,\\nwhat will be the effect", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0284.jp2"}, "285": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 263\\nA. The coil will continue to turn in the same\\ndirection and will make a half turn, after Avhich\\nit will stop.\\nQ. Can you determine in which direction the\\ncoil will turn\\nA. Yes, by applying Fleming s rule previously\\nmentioned, using the left hand. Point the fore-\\nfinger along the positive\\ndirection of the lines of force\\ndue to the magnet at any\\npart of the coil. Point the\\nsecond finger, held at right\\nangles to the forefinger, in\\nthe direction of the current\\nin that part of the coil.\\nFinally, extend the thumb\\nat right angles to both of the fingers. The direc-\\ntion in which the thumb points will be the direc-\\ntion in which that part of the coil will move.\\nQ. And if at this point the direction of current\\nis again reversed\\nA. The coil will rotate in the same direction one\\nhalf-turn further.\\nQ. What piece of well-known electrical appa-\\nratus operates in this manner\\nA. The electric motor.\\nQ. Does it make any difference whether the\\nmagnet is a permanent or electro-magnet", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0285.jp2"}, "286": {"fulltext": "264 roper s catechism for\\nA. None at ail, except that greater strength can\\nbe secured by usmg an electro-magnet.\\nExperiment 7. Suppose we have the same coil\\nof wire as in Experiment 6, which we will call\\n^coil No. 1, connected to a galvanometer, and near\\nit a second coil attached to a battery. A current\\nis flowing through coil No. 2, but not through coil\\nNo. 1, of course.\\nQ. What occurs if we suddenly disconnect the\\nbattery from coil No. 2, and what does it show\\nA. The needle of the galvanometer will give a\\nsudden jump, showing that by stopping the cur-\\nrent through coil No. 2 a current has been pro-\\nduced, or induced, as we say, in coil No. 1,\\nalthough coil No. 1 is not connected to coil No. 2\\nin any way. In a moment or two the needle of\\nthe galvanometer will come to rest at its original\\nposition, showing that the current has ceased.\\nQ. What will occur if the battery be again con-\\nnected to coil No. 2\\nA. The needle will again jump, but this time\\nin the opposite direction, showing that the induced\\ncurrent is in the opposite direction.\\nQ. Suppose that the current instead of being\\nentirely stopped were diminished and then in-\\ncreased, what would happen\\nA. We should see the needle go first one way\\nand then the other, as before, showing that any", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0286.jp2"}, "287": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 265\\nchange in the strength of current hi coil No. 2\\ntends to induce a current in No. 1.\\nQ. Looked at from the standpoint of Hnes of\\nforce, what has occurred in this experiment\\nA. From the standpoint of Hnes of force, when\\nthe current in coil No. 2 is increased more lines\\nof magnetic force are enclosed by No. 1, and a\\ncurrent is produced. When the current is dimin-\\nished less lines pass through No. 1, and a current\\nis induced in the opposite direction. The nearer\\nthe two coils are to each other the greater the\\neffect, and if a soft iron core be introduced into\\nthe axis of the coils, the induced current becomes\\nenormously greater than before.\\nQ. What electrical apparatus is illustrated by\\ntiiis experiment?\\nA. The transformer.\\nExperiment 8. Connect a battery to a galvanom-\\neter and notice the reading of the needle which\\nshows what current is flowing through the circuit.\\nConnect in tandem another cell of battery.\\nQ. What will occur\\nA. The reading of the galvanometer needle will\\nbe increased, being about double what it was\\nbefore.\\nQ. What does this show\\nA. That the current through the circuit is\\ndouble.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0287.jp2"}, "288": {"fulltext": "266 roper s catechism for\\nQ. Has the resistance of the circuit been appre-\\nciably changed?\\nA. No.\\nQ. What could have caused double flow through\\nthe same resistance\\nA. Reasoning from analogy to the flow of water,\\nthe pressure tending to cause flow must have been\\ndoubled.\\nQ. Would you then conclude that there is such\\na thing as electrical pressure\\nA. Yes, and that each generator, as, for instance,\\na battery, furnishes a definite pressure, and that\\nwhen two are connected in tandem the two\\ntogether furnish a pressure which is the sum of\\nthe pressures furnished by each.\\nQ. What other names are there for electric pres-\\nsure?\\nA. Difference of potential (P. D.), electro-\\nmotive force (e. m. f. and voltage.\\nQ. The battery produces electric pressure by\\nmeans of chemical action; is there any other\\nmethod\\nA. Yes; an electric pressure is produced wher-\\never a conductor cuts across lines of force; or if the\\nconductor is in a coil a pressure is produced when-\\never the number of lines of magnetic force\\nenclosed by the coil is in any way changed.\\nThe pressure continues only so long as the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0288.jp2"}, "289": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 267\\ncutting or change of number of lines of force\\ncontinues.\\nQ. Upon what does the amount of electric pres-\\nsure depend\\nA. On the rate of cutting the lines of force\\nthat is, the number cut per second or the change\\nper second in the number enclosed by a coil.\\nQ. Suppose a coil has 10,000 lines of force\\npassing through it, its plane being perpendicular\\nto the lines of force, which lines are in this case\\nsupposed to be parallel and straight. Now let\\nthe coil be rotated one quarter- turn, how many\\nlines will it enclose\\nA. Zero.\\nQ. Suppose it took one-quarter of a second to\\nmake the quarter-turn, what would be the rate of\\nchange of lines of force enclosed by the coil\\nA. 10,000 ^i 40,000 per second.\\nELECTRICAL UNITS.\\nQ. What is the unit of electrical pressure or\\nelectro-motive force\\nA. The volt, which is the pressure furnished by\\na certain standard cell.\\nQ. What is the unit of resistance\\nA. The resistance of a column of mercury 41.85\\ninches long and w^eighing 223 grains at 32\u00c2\u00b0 Fahr.\\nIt is called the ohm.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0289.jp2"}, "290": {"fulltext": "268 roper s catechism for\\nQ. Are the standard ohms and multiples of the\\nohm used in practice made of mercury\\nA. No; they are made of German-silver wire, or\\nan alloy of copper, nickel, and one or more metals.\\nQ. What is the unit of current\\nA. It is the current which will deposit, in one\\nsecond, on the kathode plate, from a standard\\nsolution of silver nitrate, .001118 gram (.017\\ngrain) of silver. It is called the ampere^ and is\\nin its nature a unit of rate of flow and analogous\\nto a flow of a certain quantity per second.\\nQ. What other common unit is employed\\nA. The watt, which is the unit of power. It is\\nequal to a volt-ampere that is, the power in watts\\nis equal to the product of the number of amperes\\nflowing multiplied by the number of volts pressure\\ncausing the flow.\\nQ. What relation does the watt bear to a horse-\\npower\\nA. One horse-power equals 746 watts exactly,\\nor, in round numbers, 750.\\nQ. AVhat multiple of the watt is found con-\\nvenient\\nA. The kilowatt, written K.W., which is 1000\\nwatts and nearly equal to horse-power.\\nQ. In measuring electrical properties, such as\\ncurrent, pressure, resistance, or power, what is the\\ngeneral method of going about the work", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0290.jp2"}, "291": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 269\\nA. Take current as an example. We find some\\neffect of current easy to observe, and we agree to\\ncall a current which produces this effect to a certain\\nextent unit current, as, for example, the current\\nwhich in one second will deposit from a nitrate of\\nsilver solution .017 grain of silver is called unit\\ncurrent. Having an unknown current which it is\\ndesired to measure, we observe how many grains\\nof silver it will deposit in one second, and if it\\ndeposits 17 grain we call it a current of 10 units\\nor 10 amperes. Of course, no one in actually\\nmeasuring a current now goes through the long\\nprocess of measurement by means of depositing a\\nmetal any more than in order to measure a length\\nhe makes a journey to the British Museum to get\\nthe standard yard-stick. Convenient instruments\\nworking on the principle of a galvanometer are\\nmade so that when a current of 1 ampere flows\\nthrough their coils their needle points to 1; with\\na current of 2 amperes, points to 2, and so on.\\nQ. What multiples of the units given above are\\nin common use?\\nA. The megohm 1 million ohms.\\nThe microhm 1 millionth part of 1 ohm.\\nThe kilowatt 1 thousand watts.\\nQ. Can these prefixes, meg, micro, and kilo, be\\nused with the other electrical units\\nA. Yes; although such use is not very common.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0291.jp2"}, "292": {"fulltext": "270 roper s catecpiism for\\nRESISTANCE.\\nQ. How is the resistance of a conductor affected\\nby increasing its length\\nA. The resistance is increased proportionately\\nto the increase in length.\\nQ. What is the effect of increasing the area of\\ncross-section\\nA. The resistance is lessened proportionately; in\\nother words, the resistance is inversely pro23ortional\\nto the area of the cross-section.\\nQ. A certain size wire, 100 feet long, has a\\nresistance of 2 ohms, what will be the resistance\\nof 200 feet of the same wire\\nA. 2 X 2, or 4 ohms.\\nQ. Suppose that 100 feet of wire inch diam-\\neter has a resistance of 1 ohm, what would be its\\nresistance if the diameter were ^V inch\\nA. Since the new diameter is one-half the old,\\nthe area of cross-section of the new wire is J X J,\\nor one-quarter that of the old wire. The resistance\\ntherefore would be four times greater, or 4 ohms.\\nQ. What is meant by the conductivity of a wire\\nor other conductor\\nA. The opposite of resistance. It is numeri-\\ncally e(^ual to 1 divided by the resistance.\\nQ. A wire has a resistance of 100 ohms, what\\nis its conductivity", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0292.jp2"}, "293": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 271\\nA. 1-^0 5 01 -Ol-\\nQ. When two re-\\nsistances, as Fand R,\\nare joined as shown\\nin the figure, how are\\nthe}^ said to be connected\\nA. In parallel or multiple.\\nQ. When so connected, what is their joint\\nresistance, that is, the resistance from A to B?\\nA. It is found by the formula, joint resistance\\nE-i- Y\\nQ. Two resistances of 10 and 20 ohms respect-\\nively are joined in multiple, what is their joint\\nresistance\\n10 X 20 200 .2 I.\\nI0-+20^W==^^^^^^-\\nQ. When the resistances are equal, what is the\\njoint resistance\\nA. One-half the resistance of one.\\nQ. When several equal resistances are connected\\nin multiple, what is their joint resistance equal to\\nA. To the resistance of one divided by the\\nnumber of them.\\nQ. When are two conductors said to be con-\\nnected in series f\\n*For complete explanation, see Eoper s Engineers\\nHandy-Book, page 665.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0293.jp2"}, "294": {"fulltext": "272 koper s catechism for\\nA. When they are jomed tandem, or end on.\\nQ. When two resistances are connected hi series,\\nwhat is their Joint resistance equal to\\nA. To the sum of the separate resistances.\\nQ. What is specific resistance\\nA. It has the same relation to resistance that\\nspecific gravit}^ has to weight. It is the resistance\\nof a cubic inch, or it may be expressed in cubic\\ncentimeters.\\nQ. What are some of the substances having\\nlarge specific resistance\\nA. Of the metals lead, mercury, and alloys.\\nThe non-metals have a much higher specific resist-\\nance.\\nQ. What are some substances having a low\\nspecific resistance\\nA. Copper, silver, and gold.\\nQ. What are non-conductors\\nA. Substances having a high specific resistance.\\nQ. What are conductors\\nA. Substances having a low specific resistance.\\nThe metals are classed as conductors and the non-\\nmetals as non-conductors.\\nQ. What are insulators\\nA. Insulators is another name for non-con-\\nductors or poor conductors.\\nQ. What effect does a change of temperature\\nhave on the resistance of substances", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0294.jp2"}, "295": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n273\\nTABLE OF RELATIVE RESISTANCES.\\n(Substances Arranged in Order of Increasing .Resistance for\\nSAME Length and Sectional Area.)\\nName of Metal.\\nSilver, annealed,\\nCopper, annealed,\\nSilver, hard dravrn.\\nCopper, hard drawn,\\nGold, annealed,\\nGold, hard drav^ n,\\nAluminum, annealed,\\nZinc, pressed,\\nPlatinum, annealed,\\nIron, annealed,\\nGold-silver alloy (2 ozs. gold,\\n1 oz. silver), hard or an-\\nnealed,\\nNickel, annealed,\\nTin, pressed,\\nLead, pressed,\\nGerman silver, hard or an-\\nnealed,\\nPlatinum-silver alloy (1 oz.\\nplatinum, 2 ozs. silver),\\nhard or annealed,\\nAntimony, pressed,\\nMercury,\\nBismuth, pressed,\\nCarbon,\\nResistance in Microhm\\nat 0\u00c2\u00b0 Centigrade.\\n32\u00c2\u00b0 Fabr.\\nCubic\\nCenti-\\nmeter.\\n1.504\\n1.598\\n1.634\\n1.634\\n2.058\\n2.094\\n2.912\\n5.626\\n9.057\\n9.716\\n10.87\\n12.47\\n13.21\\n19.63\\n20.93\\n24.39\\n35.50\\n94.32\\n131.2\\nCubic\\ninch.\\n0.5921\\n0.6292\\n0.6433\\n0.6433\\n0.8102\\n0.8247\\n1.147\\n2.215\\n3.565\\n3.825\\n4.281\\n4.907\\n5.202\\n7.728\\n8.240\\n9 603\\n13.98\\n37.15\\n51.65\\nRelative\\nResist-\\nance.\\n1.\\n1.063\\n1.086\\n1.086\\n1.369\\n1.393\\n1.935\\n3.741\\n6.022\\n7.228\\n8.285\\n8.784\\n13.05\\n13 92\\n16.21\\n23.60\\n62.73\\n87.23\\n14.\\n18", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0295.jp2"}, "296": {"fulltext": "274 EOPER s CATECHISM FOR\\nA. It increases the resistance of metals and\\ndiminishes the resistance of non-conductors.\\nQ. Can you remember about how much a\\nchange of temperature of one degree Fahrenheit\\naffects the resistance of metals\\nA. It increases the resistance of the common\\nmetals roughly about 2 parts in 1000.\\nPractical Use of Conductors and Insulators.\\nFor carrying electrical energy from the point\\nwhere it is generated to the point where it is to be\\nused we want to use such material and of such\\nsize that the resistance of the circuit does not\\nexceed reasonable limits, although we must be\\nguided by consideration of the first cost. Copper\\nhas the lowest specific resistance of the common\\nmetals and is generally employed, although if\\naluminum gets much lower in price than now\\n(30 cts. per pound), it will be a serious competi-\\ntor to copper. Iron is used only on short tele-\\ngraph and telephone lines. It is evident that the\\ncircuit should be as direct as possible, as the\\ngreater its length the greater its resistance, and\\ntherefore the greater is the amount of energy lost\\non the line.\\nInsulators are used to prevent current from\\nbeing led off the conductors. For all work ex-\\ncept outdoor work, and, indeed, for a large part\\nof that, the conducting wire is covered with one", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0296.jp2"}, "297": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 275\\nor more layers of some compomid of rubber\\nwhich is a good insulator. The thicker this\\nrubber covering the better its insulating proper-\\nties, for we have made the path of leakage of\\ncurrent longer by thickening the rubber coating.\\nA further protection is given by suspending the\\nwires at intervals on porcelain or glass or other\\ninsulators, so that the wire only comes in contact\\nwith its coating, porcelain, or the air, which is\\nalso an exceedingly good insulator. To sum up\\nbriefly, make the path through which you want\\nthe current to flow as short and easy as possible.\\nMake all possible leakage paths as long and nar-\\nrow as possible.\\nCUEEENT.\\nQ. What are some of the most notable effects\\nof electric current\\nA. It heats the conductors which carry it; it\\nproduces around the wire a magnetic field which\\nexerts a force on all magnetic substances placed\\nwithin the field; it has the power to decompose\\nor electrolyze solutions of many chemical com-\\npounds. To these three effects are given the\\nnames heating effect, magnetic effect, and electro-\\nlytic effect.\\nQ, Is the heating effect proportional to the\\nstrength of current or number of amperes", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0297.jp2"}, "298": {"fulltext": "276 roper s catechism for\\nA. No; if the amperes are doubled the heating\\neffect is four times as great instead of twice as\\ngreat. With three times as many amperes the\\nheating effect is nine times as great.\\nQ. What is the law, then, which connects the\\nheating effect with the strength of current\\nA. The heating effect is proportional to the\\nsquare of the current strength.\\nQ. How is the heating effect of a certain cur-\\nrent affected if the resistance through which it\\nflows is doubled\\nA. The heating effect is doubled, it being\\nstrictly proportional to the resistance.\\nQ. Is there any formula which gives the num-\\nber of heat units produced by a certain current\\nthrough a certain resistance\\nA. Yes; in Roper s Engineers Handy-Book,\\npage 670.\\nQ. Is the heating effect of a current a source of\\ndanger\\nA. It may be; if wires which carry currents\\nare too small they may be so heated as to set fire\\nto neighboring woodwork. On this account the\\ninsurance underwriters have found it necessary to\\nprescribe the minimum sizes which shall be used\\nfor various currents. These are published in\\ntables called Tables of Safe Carrying Capacity\\nof Wires.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0298.jp2"}, "299": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 277\\nQ. Is any practical use made of the heating\\neffect of the electric current\\nA. Yes; in electric heaters and cooking devices,\\nand also in the incandescent lamp, where the fila-\\nment is heated white hot.\\nQ. Is the magnetic effect of a current propor-\\ntional to the current strength\\nA. Strictly.\\nQ. Is the electrolytic effect also proportional to\\nthe current strength\\nA. Yes; doubling the number of amperes will\\nalways double the electrolytic effect, tripling the\\namperes will triple it, and so on.\\nQ. When, as in Experiment No. 1, a metallic\\nsalt is electrolyzed, does the amount of copper\\ndeposited bear any definite relation to the current\\nstrength\\nA. Yes; one ampere will always deposit a\\ndefinite amount of copper per second.\\nQ. Does it make any difference what salt of\\ncopper is used\\nA. Generally speaking, no; but with one or\\ntwo salts the number of grains of copper deposited\\nper second by one ampere is double what it is\\nwith the ordinary salts.\\nQ. Will one ampere deposit from a silver salt\\nsolution the same number of grains per second as\\nwith copper?", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0299.jp2"}, "300": {"fulltext": "278 roper s catechism for\\nA. No; one ampere deposits different weights\\nof the various metals per second, the amounts\\nbeing proportional to the atomic weights of the\\nelements or to multiples of them.\\nELECTRO-MOTIVE FORCE OR ELECTRIC\\nPRESSURE.\\nQ. In what ways may electric pressure be pro-\\nduced\\nA. There are many ways of which these four\\nare the most common:\\n1. By rubbing together two dissimilar sub-\\nstances, as silk and glass.\\n2. By heating the point at which two dissimilar\\nmetals are joined together.\\n3. By chemical action, as in Experiment No. 1\\nwith the chemical battery.\\n4. By moving a magnet relatively to a coil of\\nwire, as in the dynamo, the principle being illus-\\ntrated in Experiment No. 4.\\nQ. Which method is the most important?\\nA. The last; the first two are scarcely used at\\nall in practice. The third is used only where\\nsmall amounts of power are required.\\nQ. If there is a difference of electrical pressure\\nexisting between two points and these two points\\nbe joined by a conductor, what will occur\\n*See Roper s Engineers Handy-Book, p. 612.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0300.jp2"}, "301": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 279\\nA. An electric current will flow from the point\\nof higher pressure to the other point.\\nQ. How long will this current continue?\\nA. As long as there is any difference of pressure\\nbetween the two points. If the two points are, for\\nexample, the terminals of a battery, which by\\nchemical action keeps up a difference of pressure\\nbetween its terminals, the current would continue\\nuntil one of the chemicals of the battery, the zinc\\nor solution, is exhausted.\\nQ. How could you determine if two points\\nwere at the same pressure\\nA. By connecting a galvanometer between the\\npoints. If the needle of the galvanometer was\\nnot deflected this would show that no current\\nflowed through it and, therefore, that no difference\\nin electrical pressure existed between the two\\npoints to which it was connected.\\nQ. When an electric pressure exists between two\\npoints, is there also any mechanical pressure.\\nA. Yes; the medium or substance separating\\nthe two points is under a mechanical strain which\\nis proportional to the number of volts electrical\\npressure existing between the two points. If this\\nvoltage is very great the substance, be it air, glass,\\nporcelain, or otherwise, is actually cracked and an\\nelectric spark passes which tends to relieve the\\ndifference of pressure.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0301.jp2"}, "302": {"fulltext": "280 roper s catechism for\\nOHM S LAW.\\nThis law, which is the relation existing\\nbetween current, pressure, and resistance of a\\ncircuit, is the most important law in electrical\\nscience, and an intelligent application of it will\\nsolve most problems which the ordinary engineer\\nwill meet. This law is as follows: In an electric\\ncircuit the total current (amperes) is equal to the\\ntotal electric pressure (in volts) divided by the\\ntotal resistance (in ohms). In shorter form it is\\nE\\nexpressed by the formula O 75-, where C cur-\\nrent in amperes, E pressure in volts, and E\\nresistance in ohms. Several examples will illus-\\ntrate its use.\\nQ. In a certain electrical circuit there is an\\nelectro-motive force or electrical pressure of 4 volts.\\nThe total resistance of the circuit is 2 ohms.\\nHow much will be the current\\nE\\nA. (7 f 2 amperes.\\nQ. What electro-motive force or electrical pres-\\nsure must be used to force a current of 10 amperes\\nthrough a circuit whose resistance is 10 ohms\\nA. C=~otE=CR 10x10 100 volts.\\nK\\nQ. If under a pressure or electro-motive force", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0302.jp2"}, "303": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 281\\nof 100 volts we get a current flow of 20 amperes,\\nwhat is the resistance of the circuit\\nA. C=^OYR 5ohms.\\nWhen there is more than one electro-motive\\nforce acting in a circuit, we must use for the value\\nof E in the above formula the resultant of all the\\nseparate electro-motive forces acting. When there\\nare several resistances in a circuit their joint\\nresistance must be used.\\nQ. Suppose we have two batteries, one giving\\n2 volts and the other 1 volt, their plates being zinc\\nand carbon, but different solutions being used in\\neach. Connect the zinc of one to the carbon of\\nthe other, and then connect from A to B a piece\\nof wire having a resistance\\nof, say, 10 ohms, as shown\\nin the sketch. When con-\\nnected in this way the elec-\\ntro-motive forces are added, c^JuuumMJiuum}\\nand the total electro-motive 1^^ /oohms ji\\nforce is 2 -f- 1, or 3 volts. The batteries themselves\\nhave some resistance, and also the lead wires A C\\nand B D. Suppose that the resistance of one bat-\\ntery is 4 ohms and the other 2 ohms, the resist-\\nance of A and B D each 1 ohm. Then the\\ntotal resistance of the circuit is 10 1 2 4\\n1 18 ohms. What will be the current?\\n^b", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0303.jp2"}, "304": {"fulltext": "282\\nA. The current will be\\nroper s catechism for\\nresultant E\\nTotalis 18 6\\ntt\\n[XWUULUSJLSiWiSJUUU\\nampere.\\nQ. Suppose that one of the batteries was re-\\nversed so that the two zincs are\\nconnected together as in the\\nsketch\\nA. The batteries now oppose\\neach other and the resultant or\\neffective electro-motive force is\\n2 1, or 1 volt. The resistance of the circuit is,\\nas before, 18 ohms, and the current will be\\nampere.\\nCalculation of Current in Divided Circuits.\\nSuppose that the battery has an electro-motive\\nforce of 2 volts, that its\\nresistance is J- ohm, that\\nthe resistance of the lead\\nwire A B is S ohms, and\\nthat between C and B we\\nhave two paths of resistance 10 and 20 ohms each.\\nQ. What will be the total current flowing\\nthrough the batter}^ and through A Bf\\nA. First find the total resistance of the circuit.\\nThe joint resistance between the points B and E\\nis, as previously shown under Resistance,\\n10 X 20\\nequal to\\n10 20\\n^0 g| ol^j^g^ rpj^g ^(j^al", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0304.jp2"}, "305": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 283\\nresistance of the circuit is therefore 6f J 3,\\nE\\nor 10 ohms. The current is equal to p .2\\nampere.\\nQ. What part of the current flows through\\neach branch\\nA. Obviously the greater part of the current\\nwill flow through the branch having the smaller\\nresistance. or J- ampere will flow through the\\n20 ohms branch, and f-J or f ampere will flow\\nthrough the other branch.\\nPractical Approximation. If the resistance\\nof batteries or generator and the leads is small\\ncompared to that of the main resistance in circuit,\\nwe may neglect them, using for R in the formula\\nthe resistance of the external circuit. This is\\ngenerally the case in electric lighting circuits,\\nwhere the resistance of the generator will rarely\\nexceed one-hundredth of an ohm, and where the\\nresistance of the line wires will usually be less than\\none-twentieth of the joint resistance of the lamps.\\nExample. Q. On a 110- volt circuit, what is the\\ncurrent (total) when one sixteen-candle-power\\nlamp of 220 ohms resistance is turned on\\nA. E= 110, R is practically 220 ohms. The\\ncurrent ampere.\\nQ. What is the current (total) when two lamps\\nare turned on", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0305.jp2"}, "306": {"fulltext": "284 roper s catechism for\\nA. The joint resistance of two similar lamps is\\n220 X 220 220 X 220 .,r. w\\n2-20T220 TT220-\\nthat of one lamp. The total current 1\\nampere. The current through each lamp is the\\nsame, and is ampere as before.\\nWith three lamps turned on the joint resistance\\nis one-third of 220, or 73J, and the total current\\n^______\\nr~ r~~ 1.^^ peres, and the cur-\\nr^ r^ r through each\\nlamp is still am-\\npere. Turning on one lamp then adds J ampere\\nto the total current. The lamps are connected in\\nmultiple as shown in the figure.\\nThe Use of Alternating Currents complicates\\nthe calculation of current, pressure, and resist-\\nance by Ohm s laAv, and the method of making\\nsuch calculations is outside of the scope of this\\nbook, inasmuch as the ordinary engineer would\\nrarely be called upon to do so.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0306.jp2"}, "307": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 285\\nELECTRICAL MEASUREMENT.\\nQ. What are the electrical quantities which the\\nengineer is called upon to measure\\nA. Current, electro-motive force, resistance, and\\npower.\\nQ. What instruments are necessary\\nA. For direct-current circuits, an ammeter and\\nvoltmeter of proper range.\\nQ. How are the Weston ammeters constructed\\nA. They consist of a fixed permanent magnet\\nof horse-shoe form, between the poles of which is\\npivoted a coil of fine wire which carries the needle.\\nWhen the coil is connected so that a current flows\\nthrough the coil, it tends to turn so as to include\\nthe maximum number of lines of force due to the\\nmagnet. This motion is resisted by a pair of\\nsprings resembling the hair spring of a watch.\\nIn the instruments for measuring currents of\\nmdre than an ampere, only a known fraction of\\nthe current passes through the coil, the balance\\npassing through a conductor placed in parallel\\nwith the coil.\\nQ. Suppose we have a circuit similar to that in\\nthe sketch and we desire to measure the current\\ntaken by four lamps. How would you proceed\\nA. If these are 16 candle-power (16 c. p.)", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0307.jp2"}, "308": {"fulltext": "286\\nROPER S CATECHISM FOR\\nlamps on a 110-volt circuit, we know that they\\nwill take, roughly, J ampere each. Therefore to\\nmeasure accurately their current we need an\\nammeter intended to measure small currents.\\nConnect its terminals to two points on the circuit\\nas C and D by wires, as shown by dotted lines.\\nThen cut the circuit between C and D. The total\\ncurrent will now flow around through the am-\\nmeter and the reading of the needles will, if the\\ninstrument is correct, give\\nthe current in amperes.\\nNotice that one termi-\\n(^5*25 marked and the\\nother If the instru-\\nment is not connected\\nproperly, the needle will\\nmove, or try to move, to\\nthe left of the scale. In\\nthis event reverse the wire connections from the\\npoints C and D to the instrument. Such an\\ninstrument tells the polarity of the circuit that\\nis, which is the higher pressure and which the\\nlower pressure side. When the binding-post\\nis connected to the higher pressure side of the\\ncircuit the needle deflects in the proper direc-\\ntion.\\nQ. Suppose we have no ammeter of proper\\nrange available, but we have a resistance whose", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0308.jp2"}, "309": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 287\\nvalue we know and which will carry the current\\nto be measured without much heating\\nA. In this case with the aid of the voltmeter\\nwe can measure current. Suppose we have a\\nresistance which we know is 1 ohm and a portable\\nvoltmeter with an additional scale reading from\\nto 15 volts, and we want to make the current-\\nmeasurement just described. Put the resistance\\nin between C and D and connect the voltmeter\\nterminals to the ends of the resistance. Suppose\\nthe reading of the voltmeter was 2.3 volts. The\\ncurrent through the resistance is by Ohm s law\\nequal to the electrical pressure or electro-motive\\nforce between its terminals divided by the resist-\\nance, or 2. 3 1, which is 2. 3 amperes. This is the\\nmethod used in the Weston switchboard instru-\\nments, a resistance of known value being placed\\nin the main circuit of the dynamo and two leads\\ntaken off from its terminals and run to a volt-\\nmeter.\\nQ. How would you measure the electrical pres-\\nsure between two points\\nA. I would connect the terminals of a voltmeter,\\none to each of the points.\\nQ. Suppose the voltage between the points is\\ngreater than the range of the voltmeter. For\\nexample, suppose you wish to measure a voltage\\nwhich you know is about 220, but have an instru-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0309.jp2"}, "310": {"fulltext": "T-/\\nV*\\n288 roper s catechism for\\nment which reads only to 150 volts, what is the\\ninethod\\nA. Connect between the two points A and B,\\nwhose voltage is wanted,\\ntwo 110- volt lamps in se-\\nries. Then make the con-\\nnections shown by the solid\\nlines and read. Change\\nthe connections to the dot-\\nted positions and read again. The sum of the two\\nreadings will be the voltage between A and B.\\nQ. Is there any other method\\nA. Yes; in the other method it is necessary to\\nhave a known resistance, to place it in series with\\nthe voltmeter, and also to know the resistance of\\nthe voltmeter. This last is usually given on the\\nbox containing the instrument. A resistance just\\nequal to that of the instrument doubles its range.\\nIn general, to get the value of the reading of a\\nvoltmeter when a resistance has been put in series\\nwith it, multiply its reading by the sum of the\\nresistance of the instrument and the auxiliary\\nresistance, and divide the product by the resistance\\nof the instrument.\\nQ. How would you measure a resistance for\\ninstance, the resistance of a coil of wire\\nA. li I had an ammeter and voltmeter of\\nproper range I would put the ammeter in series", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0310.jp2"}, "311": {"fulltext": "STEAM ENGINEERS AND ELECTEICIANS. 289\\nwith the coil and would connect the voltmeter to\\nits terminals. Then I would send a current from\\na battery or dynamo through the coil and take the\\nreadings of the ammeter and voltmeter. By\\nOhm s law current or resistance\\nresistance\\nvoltage\\ncurrent\\nQ. What do you mean by instruments of proper\\nrange in this case\\nA. The ammeter must be suitable for measur-\\ning the largest current which the coil can carry\\nwithout overheating, and the voltmeter must be\\nsuch that the voltage at the terminals of the coil\\nwill give a deflection of the need large enough to\\nbe readable with accuracy.\\nQ. Is there any other method of measuring\\nresistance\\nA. Several. One of the most valuable, since it\\nneeds only a voltmeter of known resistance and\\nsome form of current\\nX\\n,.^y^^\\ngenerator, is known as\\nthe Voltmeter Method.\\nThis method requires\\ntwo readings of the\\ninstrument. For the\\nfirst reading the in-\\nstrument is connected to the terminals of the\\n19", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0311.jp2"}, "312": {"fulltext": "290 roper s catechism for\\ncurrent-generator. For the second reading the\\nunknown resistance is put in series with the volt-\\nmeter and then the two connected to the generator.\\nIn the figure X is the unknown resistance, and for\\nthe first reading the connection shown by the\\ndotted hne is made. For the second reading the\\nconnection is as shown by the solid lines. To cal-\\nculate the resistance from the readings divide the\\nfirst reading by the second, then multiply the\\nquotient by the resistance of the voltmeter, and\\nfrom the product subtract the resistance of the\\nvoltmeter.\\nQ. Which of these methods would you use for\\nlow resistances of, say, less than 100 ohms\\nA. The first method.\\nQ. Which for high resistances, such as insula-\\ntion tests\\nA. The voltmeter method.\\nQ. How would you connect for a test of the\\ninsulation of the armature\\ncoils of a dynamo, from\\nthe frame\\nA. As in the figure, the\\nheavy black line represent-\\ning a commutator seg-\\nment, and the cross-hatched\\nportion representing the frame. The white space be-\\ntween, of course, represents the insulating material.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0312.jp2"}, "313": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 291\\nQ. How would you measure the power used in\\nany part of a circuit, as, for example, in a lamp\\nA. Power being the product of volts by amperes\\n(in direct-current circuits), I would connect an\\nammeter in series with the lamp and a voltmeter to\\nits terminals, and would multiply their readings\\ntogether, thus obtaining the number of watts.\\nQ. Suppose you wished to get the horse-power\\nA. I would divide the number of watts by\\n746.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0313.jp2"}, "314": {"fulltext": "292 roper s catechism for\\nELECTRIC BATTERIES.\\nQ. What two kinds of electric generators are\\nin most common use\\nA. The chemical generators, or batteries, and\\nthe magneto- electric generators, or dynamos.\\nQ. In what cases are batteries used?\\nA. When the amount of power to be supplied\\nis small, as for bells, time clocks, telegraphs, tele-\\nphones, surgical lamps, dental engines, etc., and\\nin some cases in which the introduction of the\\nengine which would be needed to drive a dynamo\\nwould be objectionable.\\nQ. Why are batteries not used when large\\namounts of power are required\\nA. On account of the expense of the chemicals\\nused. Zinc is in nearly all batteries the fuel, and\\nsince the energy produced by burning one pound\\nof it is only one-sixth that produced by one pound\\nof coal, and, moreover, since the cost of zinc is\\nabout sixty times that of coal, it is much cheaper\\nto generate electric power by means of coal rather\\nthan by means of zinc.\\nQ. What are secondary or storage batteries\\nA. Those whose chemical actions may be re-\\nversed by sending an electric current (from some\\noutside source) through them in the opposite", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0314.jp2"}, "315": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 293\\ndirection to the current which they have produced.\\nThereby they are restored to the original condition\\nwhich existed before they were used to produce\\nelectric current.\\nQ. Do they store electricity\\nA. Not at all. They store up energy in the\\nform of chemical energy, which at any time may\\nbe changed into electrical energy by connecting the\\nterminals of the battery together by some con-\\nductor.\\nQ. What are primary batteries\\nA. Those whose chemical actions cannot be\\nreversed by passing an electric current through\\nthem in the reverse direction.\\nQ. Give an example of a reversible cell.\\nA. The Daniell cell.\\nQ. Is it used as a storage or as a primary battery\\nA. As a primary; others being better adapted\\nfor use as secondaries.\\nQ. Into what two classes may primary cells be\\ndivided\\nA. OiDcn-circuit cells and closed-circuit cells.\\nQ. What is an open-circuit cell\\nA. A cell suitable for use on circuits that are\\nnormally open, being closed only at the moment\\nwhen work is to be done; as, for example, bell\\ncircuits, gas-lighting circuits, time systems, watch-\\nclock systems, etc.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0315.jp2"}, "316": {"fulltext": "294 roper s catechism for\\nQ. What kind of a cell is generally employed\\nfor such work\\nA. A cell known as the Leclanche, having a\\nzinc plate for one pole, a carbon plate for the\\nother pole, and the two immersed in a solution of\\nsal-ammoniac.\\nQ. What is the voltage furnished by such a cell\\nand what is the resistance of the ordinary size\\ncell?\\nA. About IJ- volts and from to -f^ ohm\\nresistance.\\nQ. Why is not this cell suitable for closed cir-\\ncuit work\\nA. Because when a circuit is closed hydrogen\\nparticles begin to collect on the carbon plate, and\\nthese cut down the voltage and at the same time\\nincrease the resistance of the cell.\\nQ. If the circuit of the cell is opened do these\\ndisappear\\nA. Yes; in a few minutes.\\nQ. Is there any way of lessening the trouble\\ncaused by the collection of hydrogen particles\\nA. Yes; by using a porous carbon and by put-\\nting next to the carbon a slab of some strong\\noxidizing agent like manganese binoxide. In the\\nbest forms of cell the carbon is made in the form\\nof a thin, hollow cylinder, and the manganese in\\npowdered form is placed inside.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0316.jp2"}, "317": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 295\\nQ. What is the effect of the manganese bin-\\noxide\\nA. It gives up a part of its oxygen, which\\nattacks the hydrogen particles and forms, with\\nthem, water.\\nQ. Why are some zincs made in the form of a\\nhollow cylinder extending around the carbon\\nA. To diminish the resistance of the cell. The\\ngreater the surface of the plates and the nearer\\nthey are together, the less is the resistance of the\\ncell.\\nQ. What cell is largely used for closed circuit\\nwork?\\nA. Some form of the Daniell cell. In its orig-\\ninal form it consisted of a zinc plate in sulphuric\\nacid on one side of a porous wall and a copper\\nplate in a solution of copper sulphate on the\\nother side.\\nQ. What is the gravity cell\\nA. A form of Daniell in which the different\\nspecific gravities of the liquids are used to keep\\nthe liquids from mixing without the use of a\\nporous cup.\\nQ. What is the voltage and resistance of a\\nDaniell cell\\nA. The voltage is about 1 volt. The resistance\\nof the ordinary size gravity is in the vicinity of 4\\nohms.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0317.jp2"}, "318": {"fulltext": "296 roper s catechism for\\nQ. What other cell is largely used and for what\\nclass of work?\\nA. The bichromate cell; for small motors and\\ncautery work, where a strong current is needed for\\na few minutes. It consists of zinc and carbon\\nplates immersed in chromic acid.\\nQ. What is the voltage of these cells and their\\nresistance\\nA. About 2 volts. Their resistance varies, of\\ncourse, with their size, that of the smaller sizes\\nbeing only a fraction of an ohm.\\nQ. What are the two chief objections to this cell\\nA. The fumes produced and the eating, of zinc\\neven when the circuit is open.\\nQ. What is done to lessen the latter objection\\nA. The cell is arranged so that the zinc plate\\ncan be easily raised out of the solution when the\\ncircuit is open.\\nQ. What are dry cells\\nA. Cells in which the solution has been reduced\\nto a pasty condition.\\nQ. What are their advantages\\nA. Their greater portability; on the other hand,\\ntheir resistance is higher, and they polarize more\\nreadily.\\nQ. What do you mean by polarization?\\nA. The collecting of hydrogen particles previ-\\nouslv mentioned.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0318.jp2"}, "319": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 297\\nDYNAMOS*\\nQ. For what is a dynamo used\\nA. To change mechanical energy into electrical\\nenergy.\\nQ. The dynamo as well as the battery are\\nsometimes likened to an electrical pump. In\\nwhat respect do they resemble a pump\\nA. They may be considered as raising electricity\\nfrom a low level to a high level, just as a pump\\nraises water.\\nQ. Of what does a dynamo consist\\nOf a magnet and a coil of wire moving\\nrelatively to each other. Generally, the magnet\\nis fixed and the coil rotates between its poles. A\\ndifference of electric pressure is set up between the\\ntwo ends of the coil, and if these ends are connected\\ntogether a current will flow.\\nQ. Upon what does the amount of electrical\\npressure depend?\\nA. It is proportional to the rate of change in\\nthe number of lines of force enclosed by the coil.\\nIt is, therefore, increased by increasing the strength\\nof the magnet, the speed of revolution, or the\\nnumber of turns of wire in the coil.\\nQ. With such a simple dynamo, is the direction\\nand strength of current uniform", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0319.jp2"}, "320": {"fulltext": "298 eoper s catechism for\\nA. No; the current can best be represented by\\nplotting its values at different moments, as in the\\nfigure. Here distances to the right along the\\nhorizontal line represent time. Distances above\\nor below the line represent the strength of current\\nat different times. The curve shows the variation\\nof current during three complete revolutions of\\nthe coil. It is evident from this curve that the\\nstrength of current is alwaj^s changing and that it\\nchanges direction twice in each revolution.\\nQ. What is such a current called\\nA. An alternating current.\\nQ. Can it be used for practical purposes\\nA. Yes; for lighting and for small motors.\\nQ. How is the current rectified or made contin-\\nuous in direction in the circuit where it is to be\\nused?\\nA. By the commutator, a purely mechanical\\ndevice which changes the connection between the\\nends of the coil and the external circuit just at the\\nmoment that the direction of the current in the\\ncoil is reversed.\\nSee also Roper s Engineers Handy-Book, page 689.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0320.jp2"}, "321": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 299\\nQ. What is a rectified current called\\nA. A direct current.\\nQ. For what purposes is it employed\\nA. For nearly all isolated lighting plants, for\\noperating most arc lights, for driving motors, and\\nfor charging storage batteries.\\nQ. What is the moving coil called\\nA. The armature.\\nQ. How does it differ in practice from the ideal\\nsimple dynamo\\nA. The armature is made up of a large number\\nof coils wound on an iron core. The larger num-\\nber of coils give greater uniformity to the strength\\nof current and diminishes the sparking at the\\ncommutator. The iron core is used to keep as\\nmany as possible of the lines of force produced\\nby the magnet in the space in which the armature\\nis moving, thus making the electrical pressure\\nhigher than would be the case without the iron core.\\nQ. How is the iron core made\\nA. Of thin circular disks held together by bolts\\nand attached to the armature shaft by a sort of\\nspider.\\nQ. What two classes of armatures are there\\nA. The Gramme ring and the drum-wound.^\\nQ. What is the reason of making the core out\\nof disks instead of solid metal\\n*See Roper s Engineers Handy-Book, page 691.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0321.jp2"}, "322": {"fulltext": "\u00e2\u0080\u00a2300\\nROPER S CATECHISM FOR\\nA. To diminish the heating of the core by use-\\nless currents set up in the core.\\nQ. Are the disks separated from each other in\\nany way\\nA. They are insulated from each other by\\nenamel or by thin sheets of varnished paper.\\nQ. Is the field magnet of the dynamo a perma-\\nnent or electro-magnet\\nA. An electro-magnet excited by coils carrying\\neither a part or all of the current supplied by the\\ndynamo.\\nQ. What is a series machine\\nSERIES MACHINE.\\n1\\nI\\nSI\\n;o)^\\neui\\nSHUNT MACHINE.\\nA. A dynamo in which the field-magnet coils\\ncarry all the current produced by the machine\\nthat is, the current flows around the field-magnet\\ncoils before going to the external circuit.\\nQ. What is a shunt dynamo", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0322.jp2"}, "323": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n301\\nCOMPOUND MACHINE.\\nA. One in which only a fraction of the current\\nis had around the field-magnet coils.\\nQ. What is a compound\\ndynamo\\nA. A combination of shunt\\nand series.\\nQ. What are the purposes\\nfor which a series dynamo is\\nused?\\nA. A series dynamo tends\\nto produce a current of con-\\nstant strength whatever load\\nmay be thrown on it. It is therefore used for\\nconstant-current circuits such as street arc lighting.\\nQ. When is the shunt machine used\\nA. When a machine is desired which will supply\\nconstant pressure at all loads.\\nQ. Does a shunt machine do this\\nA. Quite well, but if the closest regulation for\\nconstant pressure is desired a compound machine\\nis used.\\nQ. What is an over-compounded machine\\nA. One which, instead of maintaining the pres-\\nsure constant as the load increases, will raise the\\npressure a few volts proportionally to the amount\\nof load.\\nQ. What is the advantage of this\\nA. There are two advantages. One is to make", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0323.jp2"}, "324": {"fulltext": "302 roper s catechism for\\nup for a slight lowering of speed in the engine,\\nwhich takes place as the load increases. The other\\nis to make up for the loss in pressure owing to the\\nresistance of the external circuit wires, which loss\\nis proportional to the load which they carry.\\nQ. How can the pressure furnished by a shunt\\nor compound dynamo be varied\\nA. An adjustable resistance called a rheostat is\\nconnected in series with the shunt-field coils; by\\nturning the arm of the rheostat in one direction\\nmore resistance is thrown into this circuit and the\\ncurrent flowing around the coils is diminished.\\nThis cuts down the number of lines of force pro-\\nduced by the field magnet, and therefore the pres-\\nsure furnished by the machine is lowered. Mov-\\ning the rheostat arm in the other direction raises\\nthe pressure by cutting out resistance.\\nQ. AVhat are the brushes\\nA. The brushes are pieces of copper or carbon\\nresting on the commutator and serving to take\\ncurrent from the commutator to the external\\ncircuit.\\nQ. In order to secure freedom from sparking\\nwhat care must be exercised in setting the brushes\\nA. The brushes must be opposite each other,\\nand must fit the surface of the commutator prop-\\nerly. The rocker arm carrying them must be\\nturned into the position of least sparking.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0324.jp2"}, "325": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 303\\nDISTRIBUTION OF ELECTRICAL\\nENERGY.\\nThe production and distribution of electrical\\nenergy are very much like a small water-system,\\nwhere water is pumped from a tank to a high\\nreservoir, taken from the reservoir through pipes\\nto the place where it is to be used, and after use\\nled back to the tank to be again pumped up and\\nagain used. The generator, or dynamo, driven by\\na steam engine, gas engine, or water-wheel, corre-\\nsponds to the pump. The distributing-pipes in\\nthe water-system are replaced by copper wires for\\nthe electrical system. The high-pressure reservoir\\nand low-pressure tank are replaced by the switch-\\nboard bus bars, one of which is a high-pressure\\nand the other a low-pressure bar. The high-pres-\\nsure^ bar is also called the positive or plus\\nbar, and the other the negative or minus bar.\\nThey are each copper bars mounted on the marble\\nor slate of which the switchboard is made, and\\nare called bus bars, or omnibus bars, from the fact\\nthat all the current is carried by them. The\\nvalves of the water-system are replaced by switches,\\nthe water-meters by ammeters, and pressure-\\ngauges by voltmeters. Some devices which are\\nused in electrical distribution have nothing similar", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0325.jp2"}, "326": {"fulltext": "304 roper s catechism for\\nto them in Avater- systems, but the general shni-\\nlarity is of great assistance in understanding\\nelectrical distribution.\\nQ. What is a switchboard\\nA. One or more slate or marble slabs mounted\\non an iron or wooden framework and containing\\nthe various devices for controlling the electric dis-\\ntribution system.\\nQ. What are the principal devices to be found\\non the switchboard\\nA. 1. A voltmeter to measure electric pressure.\\nThis is generally furnished with a switch by which\\nit may be connected to the terminals of any gene-\\nrator or to the bus bars.\\n2. An ammeter for each generator to measure\\nthe current which it furnishes.\\n3. A rheostat for each generator placed in series\\nwith its shunt-field coils and controlling the pres-\\nsure furnished by it.\\n4. A device for each machine, such that if\\nowing to any trouble a current greater than the\\nmaximum for which the machine is designed\\nflows through the machine, it is automatically\\ndisconnected from the circuit. This device may\\nbe a fuse or a circuit breaker.\\n5. A device called a ground detector^ for showing\\nwhen the conductors in the system are by accident\\nbrought into electrical connection with the earth;", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0326.jp2"}, "327": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 305\\nthat is to say, with gas- or steam- or water-pipes\\nwhich are imbedded in the earth.\\n6. Switches for disconnecting the generators\\nfrom the bus bars.\\n7. Switches for disconnecting from the bus bars\\nthe distribution circuits.\\n8. A device (either fuse or circuit breaker) for\\nprotecting each distribution circuit from having\\ntoo much current flow over it.\\nQ. What are fuses\\nA. Strips of an alloy, generally of tin and lead,\\nof such size that they will melt and interrupt the\\ncircuit when a current in excess of a certain amount\\nflows through them.\\nQ. What are circuit breakers\\nA. Switches so arranged that they open auto-\\nmatically when the current flowing through them\\nexceeds a certain value.*\\nQ. Why are circuit breakers used in preference\\nto the much cheaper fuses\\nA. Because in large sizes fuses are very uncertain\\nin their action a fuse designed to melt at 500\\namperes, for example, being liable to melt with a\\ncurrent of 400 or 600 amperes.\\nQ. How is a simple form of ground detector\\nmade, and how does it operate on a circuit, say,\\nwhose pressure is about 110 volts?\\n*See Roper s Engineers Handy-Book, page 705.\\n20", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0327.jp2"}, "328": {"fulltext": "306\\nROPER S CATECHISM FOR\\nUu^\\nA. The ground detector consists of two 110-volt\\nlamps connected in series with each other and across\\nor between the bus bars. The junction between the\\ntwo lamps is connected to a convenient water-pipe.\\nSo long as the insulation of the circuit is all right\\nthe two lights burn alike equally dim, since they\\nare designed for 110 volts at their terminals and\\nthey have only 55 volts under the circumstances.\\nBut suppose any point on the circuit, as P, is\\npurposely or accidentall}^ connected\\nto earth, then the left-hand light\\nwill burn bright while the right-\\nhand one will burn exceedingly\\ndim, or perhaps not at all. The\\nreason is that the grounding of the\\npoint P has put it in electrical\\nconnection with the point A\\nthrough a very low resistance.\\nThe current through the right-hand\\nlamp is, therefore, diminished, its terminals being\\nshort-circuited. The left-hand lamp will have\\npractically 110 volts between its terminals, since\\nthe joint-resistance of the right-hand lamp and the\\nother path from A to P is exceedingly small, and\\nhence the pressure used up being also exceedingly\\nsmall. If the point P were on the other side of the\\ncircuit, the right-hand lamp would burn brightly\\nand the left-hand one ver}^ dimly.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0328.jp2"}, "329": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n307\\nQ. How would you find the location of the\\nground\\nA. By opemng the switches one by one till one is\\nfound which on being opened relieves the ground.\\nThis tells on which feeder the ground exists. Then\\nthe circuit is examined in detail by means of a\\nmagneto- bell, it being split up into sections by\\nthrowing open local switches, taking fuses out of\\nlocal distribution boards, and disconnecting at fix-\\ntures.\\nQ. May any number of dynamos be connected\\nin multiple so as to feed on the same pair of\\nbus bars\\nA. Any number of shunt machines of the same\\nvoltage may be so used.\\nQ. Cannot compound machines be so connected?\\nA. Not without a connection called the equalizer\\nshown by the dotted line in the cut.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0329.jp2"}, "330": {"fulltext": "308 eoper s catechism for\\nQ. Suppose you have one machine feeding the\\nbus bars and desire to connect up with it machine\\nNo. 2, how would you proceed\\nA. First start up the engine Of No. 2 and turn\\nits rheostat till its pressure is the same as that of\\nthe bus bars or perhaps one-half volt higher.\\nThen close the single-pole switch in the equalizer\\ncircuit, shown dotted, and finally close the ma-\\nchine s double-pole switch which connects it to\\nthe bus bars. Its ammeter reading will then in-\\ncrease, and the rheostat handles of the two ma-\\nchines are moved till the ammeters read alike (if\\nthe machines are the same size) and the voltage\\nof the bus bars is correct.\\nQ. Is any different arrangement of switches ever\\nemployed\\nA. Yes; instead of a two-pole switch in the\\ndynamo leads and a single-pole switch in the\\nequalizer lead, a three-pole switch is frequently\\nemployed. In this case the middle blade is used\\nfor the equalizer wire, and is so adjusted that it\\ncloses the equalizer circuit just before the other\\ntwo blades close their circuits.\\nSYSTEMS OF DISTRIBUTION.\\nQ. What are the two principal systems of elec- j\\ntrical distribution I\\nA. The series system and the parallel system.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0330.jp2"}, "331": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 309\\nQ. What is the difference between the two sys-\\ntems\\nA. In the series system the entire current flows\\nsuccessively through each lamp. In the parallel\\nsystem the current from the dynamo is divided, a\\npart flowing through each lamp. Afterward these\\nseparate currents unite and flow back to the dy-\\nnamo.\\nQ. What is necessary, on a series system, to\\nmake the lighting successful\\nA. It must be a constant-current system that\\nis, cutting out lamps or throwing more on must\\nnot change the value of the current.\\nQ. How is this accomplished\\nA. By an automatic regulator on the machine\\nwhich increases its voltage if lamps are thrown on,\\nand diminishes it if lamps are cut out.\\nQ. How are lamps cut out on this system", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0331.jp2"}, "332": {"fulltext": "310 roper s catechism for\\nA. By short-circuiting them that is, by provid-\\ning another path for the current to flow other than\\nthe path through the lamp mechanism and\\ncarbons.\\nQ. What is necessary in a parallel system\\nA. It must be a constant-potential or constant-\\npressure system.\\nQ. How are lamps cut out on this system\\nA. By interrupting the branch circuit in which\\nthe lamp is connected.\\nQ. In the parallel system, why does cutting out\\none lamp not affect others\\nA. Because it does not change the current flowing\\nthrough each of the others. The current through\\nany lamp depends on two things only, the pres-\\nsure and the resistance of the lamp. Turning out\\na lamp in nowise affects the resistance of other\\nlamps and only affects the pressure at the terminals\\nto a very slight de-\\nj g 1^ y gree therefore the cur-\\nCj i i 4 a i a rent flowing through\\n.*^1 o 1-8 J^ the lamp is practi-\\nj j cally the same as it\\nT Y Y Y H* before the other\\nCD I ll I lamp was turned off.\\nQ. In the cut, what\\nare the wires C A and D B called\\nA. The feeders.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0332.jp2"}, "333": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 311\\nQ. And the wires E F smd G H f\\nA. The mains.\\nQ. And from F to the lamp and H to the lamp\\nA. Branches.\\nQ. What is the Edison three- wire system\\nA. Two 110-volt machines are connected in\\nseries and the middle or neutral wire is connected\\nto their junction. When the same number of\\nlamps are burning on each side of the neutral wire\\nthere is no current flowing through the neutral\\nand the same current flows through each machine.\\nWhen No. 4 is turned out, for example, the lower\\nmachine supplies only the current necessary for\\nlamps 5 and 6, while the upper continues to\\nsupply the same as before, the current for one\\nlamp returning to the upper machine over the\\nneutral. If all lamps on one side were turned out,\\nthe machine on that side would furnish no current,\\nand the other machine would continue to work as\\nbefore.\\nQ. What is the advantage of this system\\nA. It is a 220-volt system and therefore requires", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0333.jp2"}, "334": {"fulltext": "312\\nroper s catechism for\\nmuch smaller wires to transmit a given amount\\nof energy with a given loss, wdthout increasing the\\nvoltage of the lamps.\\nQ. How much is the gain in size of wire used\\nA. The two outside wires are just one-quarter\\nas large as they would be with a 110- volt two-wire\\nsystem. If the neutral is made of the same size,\\nthe three-wire system requires as much copper\\nas the two-wire system, using the same voltage\\nlamps in both cases.\\nTABLE\\nSHOWING GAIN BY USING HIGH PEESSURES, THE SAME\\nSIZE WIRES BEING USED FOR EACH CASE.\\nPower\\ntrans-\\nmitted\\nin watts.\\nVolts at\\nwhich\\ntrans-\\nmitted.\\nCorre-\\nsponding\\nnumber of\\namperes.\\nPower\\nlost\\nin\\nwatts.\\nVolts\\ndrop\\nin line.\\nPer cent,\\npower\\nlost.\\nPer cent,\\nvolts\\nlost.\\nCXE\\nE\\nC\\nC^ R\\nC R\\nc^R^um\\nCR-^E\\n1100\\n110\\n10\\n100\\n10\\n11.\\n9.9\\n1100\\n220\\n5\\n25\\n5\\n2.75\\n2.27\\n1100\\n550\\n2\\n4\\n2\\n.0227\\n.363\\n1100\\n1100\\n1\\n1\\n1\\n.0009\\n.091\\nQ. If in one case, to transmit a certain power,\\nwe use 110 volts pressure and in another case\\n1100 volts, what will be the relative amount of\\ncopper used on the line\\nA. With 1100 volts pressure we shall need only\\nYj-g-th as much copper as with 110 volts.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0334.jp2"}, "335": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n313\\nQ. What disadvantages have high jDressiires\\nA. Greater difficulty in insulating the lines and\\ndanger to human life.\\nQ. In proportioning the size of electrical con-\\nductors, what two requirements must be met?\\nA. The wire must be large enough to transmit\\nthe energy without losing more than a prescribed\\nper cent., and the wire must further be large\\nenough so that the current will not heat it more\\nthan is allowed by the insurance regulations.\\nINSURAI^CE EULES FOR CARRYING-CAPACITY OF WIRES.\\nNational\\nNational Board of\\nAssoc.\\nEnglish\\nBoard of\\nTrade.\\nB. S.\\nElectric\\nFire Underwriters.\\nFactory\\ngauge.\\nLight\\nMutual\\nAssociation.\\nConcealed.\\nOpen work.\\nIns. Co.\\n0000\\n175\\n218\\n312\\n175\\n000\\n145\\n181\\n262\\n145\\n00\\n120\\n150\\n220\\n120\\n105\\n100\\n125\\n185\\n100\\n83\\n1\\n95\\n105\\n156\\n85\\n66\\n2\\n70\\n88\\n131\\n70\\n52\\n3\\n60\\n75\\nno\\n60\\n41\\n4\\n50\\n63\\n92\\n50\\n33\\n5\\n45\\n53\\n77\\n45\\n26\\n6\\n35\\n45\\n65\\n35\\n21\\n7\\n30\\n30\\n16\\n8\\n25\\n33\\n46\\n25\\n13\\n10\\n20\\n25\\n32\\n20\\n8\\n12\\n15\\n17\\n23\\n15\\n5\\n14\\n10\\n12\\n16\\n10\\n3\\n16\\n5\\n6\\n8\\n5\\n2\\n18\\n3\\n5\\n3\\n1", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0335.jp2"}, "336": {"fulltext": "314 roper s catechism for\\nQ. What is the loss of pressure allowable on\\nconductors\\nA. See Roper s Engineers Handy-Book, pp.\\n714-717.\\nQ. The distance between the switchboard and\\na group of ten 16 c. p. lamps is 100 feet. What\\nsize wire must be used so that the loss of pressure\\non the wire between switchboard and lamp is\\nonly one-half of one per cent., the voltage of the\\ndynamo being 110?\\nA. 1. One-half of one per cent, of 110 is .55\\nvolt, the allowable loss of pressure.\\n2. The current for ten lamps is 5 amperes.\\n3. By Ohm s law C f or i? R\\n.11 ohm that is, the wire must be of such\\nsize that the total length of it, 200 feet, has a\\nresistance not exceeding .11 ohm; 1000 feet of\\nthis size wire would have a resistance ^r^\\n.55.\\n4. Looking in the wire tables we see that No. 7\\nwire, having a resistance of .491 ohm at 60\u00c2\u00b0\\nFahr. fulfils the requirement.\\n5. Looking in the table of safe carrying capaci-\\nties on the preceding page, we find that according\\nto the National Board of Fire Underwriters rules\\na No. 7 wire will carry a much greater current", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0336.jp2"}, "337": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n315\\nPROPERTIES OF COPPER WIRE.\\nENGLISH SYSTEM BROWN SHAEPE GAUGE.\\n2\\ni a\\nWeights.\\nResistances per 1000 feet\\nin International ohms.\\n3\\ns-\\n|2\\n1000\\nfeet.\\nMile.\\nAt 60\u00c2\u00b0 F.\\nAt 75\u00c2\u00b0 F.\\n0000\\n460.\\n211600.\\n641.\\n3382.\\n.04811\\n.04966\\n000\\n410.\\n168100.\\n509.\\n2687.\\n.06056\\n.06251\\n00\\n365.\\n133225.\\n403.\\n2129.\\n.07642\\n.07887\\n325.\\n105625.\\n320.\\n1688.\\n.09639\\n.09948\\n1\\n289.\\n83521.\\n253.\\n1335.\\n.1219\\n.1258\\n2\\n258.\\n66564.\\n202.\\n1064.\\n.1529\\n.1579\\n3\\n229.\\n52441.\\n159.\\n838.\\n.1941\\n.2004\\n4\\n204.\\n41616.\\n126.\\n665.\\n.2446\\n.2525\\n5\\n182.\\n33124.\\n100.\\n529.\\n.3074\\n.3172\\n6\\n162.\\n26244.\\n79.\\n419.\\n.3879\\n.4004\\n7\\n144.\\n20736.\\n63.\\n331.\\n.491\\n.5067\\n8\\n128.\\n16384.\\n50.\\n262.\\n.6214\\n.6413\\n9\\n114.\\n12996.\\n39.\\n208.\\n.7834\\n.8085\\n10\\n102.\\n10404.\\n32.\\n166.\\n.9785\\n1.01\\n11\\n91.\\n8281.\\n25.\\n20.\\n132.\\n105.\\n1.229\\n1.269\\n12\\n81.\\n6561.\\n1.552\\n1.601\\n13\\n72.\\n5184.\\n15.7\\n83.\\n1.964\\n2.027\\n14\\n64.\\n4096.\\n12.4\\n65.\\n2.485\\n2.565\\n15\\n57.\\n3249.\\n9.8\\n52.\\n3.133\\n3.234\\n16\\n51.\\n45.\\n2601.\\n2025.\\n7.9\\n42.\\n3.914\\n4.04\\n17\\n6.1\\n32.\\n5.028\\n5.189\\n18\\n40.\\n1600.\\n4.8\\n25.6\\n6.363\\n6.567\\n19\\n36.\\n1296.\\n3.9\\n20.7\\n7.855\\n8.108\\n20\\n32.\\n1024.\\n3.1\\n16.4\\n9.942\\n10.26\\n21\\n28.5\\n25.3\\n812.3\\n2.5\\n13.\\n12.53\\n12.94\\n22\\n640.1\\n1.9\\n10.2\\n15.9\\n16.41\\n23\\n22.6\\n510.8\\n1.5\\n8.2\\n19.93\\n20.57\\n24\\n20.1\\n404.\\n1.2\\n6.5\\n25.2\\n26.01\\n25\\n17.9\\n320.4\\n.97\\n5.1\\n31.77\\n32.79\\n26\\n1.5.9\\n252.8\\n.77\\n4.\\n40.27\\n41.56\\n27\\n14.2\\n201.6\\n.61\\n3.2\\n50.49\\n52.11\\n28\\n12.6\\n158.8\\n.48\\n2.5\\n64.13\\n66.18\\n29\\n11.3\\n127.7\\n.39\\n2.\\n79.73\\n82.29\\n30\\n10.\\n100.\\n.31\\n1.6\\n101.8\\n105.1\\n31\\n8.9\\n79.2\\n.24\\n1.27\\n128.5\\n132.7\\nThere are two points in this table which will be found easy to remem-\\nber and very convenient in practice\u00e2\u0080\u0094 namely, that the resistance of 1000\\nfeet of No. 10 is almost exactly 1 ohm at 75\u00c2\u00b0 F., and that a change of\\nt three sizes either halves or doubles the resistance, according as we go up\\nor down the table.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0337.jp2"}, "338": {"fulltext": "316 roper s catechism for\\nthan 5 amperes, so that a No. 7 wire is suitable\\nfor the requirements.\\nQ. What is a mil?\\nA. One-thousandth of an inch.\\nQ. What are the circular mils in a wire\\nA. The square of the diameter in mils.\\nQ. What relation do the circular mileages of\\ntwo wires bear to their resistances\\nA. Their resistances are inversely proportional\\nto their circular mileages.\\nQ. A No. 2 wire, No. 4 wire, and No. 6 wire\\nare connected in multiple to what size wire will\\ntheir joint resistance be equal?\\nA. The sum of their circular mileages is,\\n66,564 41,616 -f 26,244 134,424, and this\\nis nearly the circular mileage of a No. 2/0 wire to\\nwhich the three wires will be practically equivalent.\\nWIRING AND APPLIANCES.\\nQ. What two classes of wiring are there\\nA. Open or exposed work and concealed work.\\nQ. In open work, what varieties are there\\nA. Porcelain work, where the wires are carried\\non porcelain knobs, and molding work, where the\\nwires are carried in a grooved molding provided\\nwith a cap to hide them from view.\\nQ. What are the varieties of concealed work\\nA. Porcelain work and conduit work.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0338.jp2"}, "339": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 317\\nQ. What is the nature of conduit work?\\nA. A system of tubes or pipes is first installed\\ninto which the wires are afterward drawn in.\\nQ. What are the fundamental requisites for a\\nconduit\\nA. It should be strong enough to protect the\\nwires from all accidents such as hammering, jar-\\nring, nails, etc. and it should not be attacked by\\ncement, plaster, or moisture. Moreover, it should\\nhave a smooth inside surface, so that the insulation\\nof the wires may not be injured by the process of\\ndrawing them in.\\nQ. What kind of conduits meet these require-\\nments\\nA. An iron or steel tube like a gas-pipe has suf-\\nficient strength. If properly painted or enameled\\nit is not affected by cement, plaster, or moisture.\\nTo secure smoothness a special pipe must be made,\\nwith this end in view or, as in some conduits, a\\nlining of wood or some compound of a bituminous\\nnature may be employed.\\nQ. How many wires are placed in one tube?\\nA. Two in the two-wire system or three in the\\nthree-wire system, except sometimes in the case\\nof large-sized feeders where it is not possible to\\ndraw two in. Where alternating currents are to\\nbe used both the wires of a circuit must be in the\\nsame tube to avoid an excessive loss of pressure.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0339.jp2"}, "340": {"fulltext": "318\\nroper s catechism for\\nQ. What is a cut-put, and when is it used\\nA. A cut-out is the name given to a combination\\nof fuse blocks, studs, and screws and convenient\\nterminals for fastening wires. These parts are\\nmounted on some insulator, as slate, marble, or\\nporcelain. A cut-out with fuse is used at every\\npoint in a circuit where the size of wire is changed.\\nQ. Why is this\\nA. So that the fuse may protect the smaller\\nwire from an excess of current.\\nQ. What is a switch\\nA. A convenient device for opening or closing\\nan electric current. It performs a similar service\\nto that of a valve in a water system, except that it\\nhas no positions corresponding to partly open. It\\nmust be completely open or completely shut.\\nQ. What is a single-pole switch\\nA. One which opens one wire of a circuit.\\nQ. What kre double-\\npole\\n-O\\nand triple\\nswitches\\nA. Those which open\\ntwo or three wires of\\nthe circuit.\\nQ. When are three-\\nway switches used\\nA. When it is de-\\nsired to control lamps from either of two points.\\n3-w^y\\n3 -way\\nCIRCUIT WITH 3-WAY SWITCHES.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0340.jp2"}, "341": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 319\\nQ. In calculating the carrying capacity of\\nswitches, what general rules are employed\\nA. Where current goes through solid metal\\nallow one square inch per 1000 amperes, and w^here\\nit goes through the joint between two pieces allow\\none square inch of contact surfaces to each 75\\namperes.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0341.jp2"}, "342": {"fulltext": "320 roper s catechism for\\nELECTRIC LIGHTING.\\nQ. In what ways may arc lamps be classified?\\nA. (1) According to the kind of distribution-\\nsystem for which they are intended, as constant\\npotential arc lamps and series arc lamps; the latter\\nare in general used now only by central stations.\\n(2) According as they are to be supplied by direct\\nor alternating current, into direct-current arcs and\\nalternating arcs. (3) According to the degree of\\nenclosure of the arc, into open arcs and closed arcs.\\nQ. What are the requirements of all arc lamps\\nA. All lamps to be commercially satisfactory\\nmust do two things: They must strike the arc\\nthat is, after current has commenced to flow they\\nmust automatically draw the carbons apart so as\\nto start the arc. They must also regulate that is,\\nas the carbons burn away they must be automat-\\nically fed together, and the feeding of one must\\nnot appreciably affect the brilliancy of others.\\nQ. How are these accomplished in an arc lamp\\nburning on a parallel or constant potential system\\nof distribution?\\nA. The current coming from the line to the\\npositive lamp-terminal passes through a coarse\\nwire coil and then through a chain or brush con-\\ntact to the upper carbon, through the upper and", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0342.jp2"}, "343": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 321\\nlower carbons, and back through a wire resistance,\\nwhich can be varied, to the other terminal of the\\nlamp and thence to line. The passage of current\\nthrough the coil lifts an iron armature or core, as\\nthe case may be, to a certain distance depending\\non the strength of the current. This armature\\nlifts a clutch-device which raises the upper carbon.\\nThe arc is thus struck and the lamp continues to\\nburn, the two carbons being gradually consumed\\nand the arc becoming longer. As the arc lengthens\\nits resistance becomes greater and the current less.\\nThis allows the armature to drop down a little,\\nand the clutch tripping against a stop lets the\\nupper carbon slide through a little, thus shorten-\\ning the arc. The moment the arc has been\\nshortened sufficiently to increase the current enough\\nto lift the clutch off the tripping-stop the feeding\\nof the carbon cCases and the lamp continues to\\nburn till the arc again becomes too long.\\nQ. Can two or more of these lamps be placed\\nin series\\nA. No; when several lamps are to be operated\\nin series they will not all feed at the same time, so\\nthat the action of one would interfere with the\\nothers unless some different arrangements were\\nintroduced.\\nQ. What modification of the mechanism is\\nmade when lamps are to be run in series\\n21", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0343.jp2"}, "344": {"fulltext": "322 roper s catechism for\\nA. An additional magnet with fine wire coil is\\nconnected as a shunt around the arc, and its arma-\\nture arranged so that when lifted to a certain point\\nit makes the clutch feed. As the arc lengthens its\\nresistance increases, and also the pressure between\\nits terminals. Hence more current is sent around\\nthe fine wire coils, raising their armature and\\nstarting the feeding mechanism.\\nQ. What is the difference between open and\\nclosed arc lamps\\nA. An open arc lamp is one in which the air\\nhas free access to the arc. A closed arc lamp is\\none in which a small inner globe placed around the\\narc prevents, to a great extent, the access of air..\\nQ. What is the object of enclosing the arc?\\nA. The consumption of carbon is diminished\\nand the light is steadier.\\nQ. How long do carbons last in the two types\\nof lamp?\\nA. About 7 hours in the open arc and about\\n100 hours in the closed arc.\\nQ. How are lamps rated commercially\\nA. Lamps are rated in candle-power according\\nto their brilliancy in the angle of greatest bril-\\nliancy. Thus the ordinary street lamp rated at\\n2000 candle-power gives that brilliancy only at an\\nangle from the horizontal of about 45 degrees.\\nAt any other angle its brilliancy is less, and the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0344.jp2"}, "345": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 323\\naverage candle-power below the horizontal will not\\nbe much over 800 candle-power. Such a lamp\\nrequires a current of 9. 6 amperes and about 45 or\\n50 volts, and a lamp using such current and pres-\\nsure that their product is 450 watts may be con-\\nsidered commercially a 2000 candle-power lamp.\\nQ. What current does a nominal 2000 candle-\\npower closed arc take\\nA. About 5 amperes on steady burning, though\\nnearly double this on first starting.\\nQ. What is the voltage between the carbons\\nA. About 80 to 90 volts.\\nQ. What effect does the use of two globes have\\non the distribution of light\\nA. It is more even with the closed arc on\\naccount of the two globes, but for the same reason\\na larger percentage of light is absorbed.\\nQ. What are the essential features of the incan-\\ndescent lamp\\nA. Incandescent lamps consist of a carbon\\nfilament attached to platinum wires, which is\\nmounted in a glass globe from which the air has\\nbeen exhausted and which is sealed up so as to ex-\\nclude air. The platinum wires serve to connect\\nthe filament to the terminals of the lamp base.\\nThe vacuum is made as perfect as possible, so that\\nthere may remain no air inside the globe in which\\nthe highly heated filament would burn aw^ay.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0345.jp2"}, "346": {"fulltext": "324 roper s catechism for\\nQ. How is the filament made\\nA. By taking a slender piece of some material\\nconsisting largely of carbon, such as bamboo, silk,\\npaper, or cellulose, and heating it intensely in a\\nfurnace so as to drive out all the other material,\\nleaving a very nearly pure carbon thread. In\\norder to smooth out the roughness and make its\\nsection uniform at all points, a current is passed\\nthrough it large enough to heat it to nearly a white\\nheat in an atmosphere of some hydrocarbon, like\\ncoal gas. This causes carbon to be deposited most\\nlargely at the hottest points, which are those of\\nthe smallest cross-section. The filament is then\\nattached to the platinum leading-in wires and\\nplaced in the globe.\\nQ. What is the remainder of the process of\\nmaking the lamp\\nA. A mechanical air-pump exhausts the air\\nfrom the globe, and, finally, by passing a strong\\ncurrent through the filament, the latter, heated to\\nincandescence, burns away the remnant of oxygen\\nremaining. The bulb is then sealed up and the\\nplatinum wires connected to the lamp-base ter-\\nminals. Finally, the lamps are tested to see at\\nwhat voltage they will give the candle-power for\\nwhich they are intended.\\nQ. What is the effect of use on the lamp\\nA. Its candle-power graduall}^ diminishes owing", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0346.jp2"}, "347": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 325\\nto the deposition of carbon from the filament on the\\nwalls of the globe, the layer of carbon absorbing\\nthe light-rays, so that after a few hmidred hours\\nburning the lamp must be replaced by a new one.\\nQ. What candle-powers are ordinarily made\\nA. 8, 10, 12, 16, 20, 24, 32, 50, 100, 150,\\nthough the last two sizes are rarely used, arc lamps\\nbeing employed instead.\\nQ. What are the voltages commonly made\\nA. From 50 to 60, 70 to 80, 100 to 120, and\\n200 to 250 lamps of 110 and thereabouts being\\nthe most common.\\nQ. Why are 220-volt lamps employed\\nA. To secure economy in the size of the dis-\\ntributing wires.\\nQ. Why are they not more extensively used\\nA. Because they are inferior in quality to the\\nlower voltage lamps.\\nQ. What are the two important qualities of an\\nincandescent lamp\\nA. Its length of life and its efficiency.\\nQ. What is meant by efficiency\\nA. The number of watts power which must be\\nsupplied to the filament to produce 1 candle-power.\\nThe most efficient lamp is that one which produces\\n1 candle-power with the least number of watts.\\nQ. Is there any relation between life and effi-\\nciency", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0347.jp2"}, "348": {"fulltext": "326\\nroper s catechism for\\nA. Yes; a somewhat unfortunate one, since we\\ncannot improve one without injuring the other.\\nThe efficiency increases with the temperature of\\nthe filament, while the life is correspondingly\\ndiminished.\\nTABLE\\nOF EFFICIENCIES AND LIFE OF INCANDESCENT LAMPS.\\nEfficiency.\\nWatts per can-\\ndle.\\nLife-hours.\\nWatts per 16\\nc. p. lamp.\\nAmperes for 16\\nc. p. 110-volt\\nlamp.\\n2.6\\n3.1\\n3.6\\n4.0\\n400\\n600\\n800\\n1000\\n41.8\\n49 6\\n57.6\\n64.0\\n.38\\n.45\\n.52\\n.60\\nQ. When is it desirable to use a low and when\\na high efficiency lamp\\nA. It depends upon the cost of power. If coal\\nis cheap, it pays to use a low efficiency and long\\nlife. If coal is dear, the high efficiency lamp\\nshould be used, provided the speed regulation of\\nthe engine is good enough to prevent fluctuations\\nin the voltage of the dynamo, it being understood\\nthat any rise in voltage above that for which the\\nlamp is intended shortens its life very seriously.\\nOf course, where all the exhaust steam of the\\ngenerator engine is used in steam heating it is de-\\nsirable to use the low efficiency and long-life lamps.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0348.jp2"}, "349": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 327\\nELECTRIC MOTORS*\\nQ. How does a motor differ from a dynamo, as\\nregards the purpose for which it is used\\nA. A dynamo transforms mechanical energy\\ninto electrical energy. A motor transforms elec-\\ntrical energy into mechanical energy.\\nQ. How do direct-current motors differ from\\ndynamos, as regards construction\\nA. Practically any direct-current dynamo, if\\ncurrent be supplied to it, will operate as a motor,\\nand a well-designed dynamo will make a good\\nmotor. Certain alterations in winding and in\\nother details are made in motors to improve cer-\\ntain qualities that may be specially desired.\\nQ. Will a dynamo used as a motor run in the\\nsame direction that it had as dynamo\\nA. A series dynamo, when used as a motor, will\\nrun in the opposite direction, and a shunt motor\\nwill run in the same direction.\\nQ, What must be done to reverse the direction\\nin which a motor will run\\nA. Change the connections so as to reverse the\\ndirection of current through either (but not both)\\nfield or armature. It may further be necessary\\nto shift the brushes to prevent sparking.\\nQ. When are series motors employed?", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0349.jp2"}, "350": {"fulltext": "328 ROPER S CATECHISM FOR\\nA. The series motor is used where it is necessary\\nto start with full load and where automatic regu-\\nlation for constant speed is not necessary, a hand\\nregulation being used, as, for example, in hoists,\\ncranes, street railways, etc.\\nQ. When are shunt motors used\\nA. A shunt motor is used where automatic\\nregulation for constant speed is desired. A good\\nshunt motor will not change its speed more than\\n5 per cent, when the load is varied from zero to a\\nmaximum.\\nQ. Under what circumstances would compound\\nmotors be desirable\\nA. Compound motors are used where closer\\nspeed regulation than that given by shunt motors\\nis desired, and in special cases, such as on planers\\nwhere it is desired to check the sudden large flow\\nof current during reversal.\\nQ. With a series motor, whose use is almost\\nentirely on constant pressure circuits, how is\\nregulation of speed accomplished\\nA. There are two common methods:\\n1. To change the pressure supplied to it, by\\nputting in series with the motor a rheostat in\\nwhich more or less pressure is used up according\\nto the position of the rheostat-handle. Lowering\\nthe pressure will, of course, lower the speed.\\n2. To change the strength of the field of the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0350.jp2"}, "351": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 329\\nmotor. This is done by winding the field coils in\\nsections and bringing out the ends to a sort of\\ncommutating device called a controller. In one\\nposition of the controller handle the sections will\\nall be in series, cutting down the current and\\nmaking the ampere turns of the field, and hence\\nits strength, low. In the next position, for ex-\\nample, three sections will be in series and three\\nothers in series, and the two sets of three in\\nmultiple, which will diminish the resistance, let\\nmore current through, and increase the ampere\\nturns. Another position will put more in multiple\\nand less in series, and so on till the final step puts\\nall the sections in multiple, giving the lowest\\npossible resistance, highest number of amperes,\\ngreatest number of ampere turns, and strongest\\nfield. With the series motor on constant potential\\ncircuits the speed is increased in proportion as we\\nincrease the field strength. A combination of the\\ntwo methods is frequently used, the resistance\\nbeing used during the first positions in order to\\ncut down the excessive flow of current on starting.\\nQ. How are shunt motors, on constant pressure\\ncircuits, regulated for changes in speed\\nA. By putting resistance coils in series wdth the\\narmature and throwing more or less of them in\\naccording as we want lower or higher speed.\\nAnother method is to put a rheostat in the field", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0351.jp2"}, "352": {"fulltext": "330 roper s catechism for\\ncircuit and vary the current flowing around the\\nfield coils by means of it.\\nQ. What effect does weakening the field have\\non the speed of the series motor on constant pres-\\nsure circuits\\nA. It lowers the speed.\\nQ. What is the effect with a shunt machine\\nA. Weakening the field increases the speed.\\nQ. How are compound motors regulated\\nA. Generally like shunt motors; but in some\\nspecial cases the series coils are wound in sections\\nand thrown in series, and finally in multiple, as\\nis the case with series motors.\\nQ. In starting shunt or compound motors what\\nprecaution is necessary\\nA. It is necessary to put a considerable resist-\\nance in series with the armature, on account of its\\nvery low resistance, which will vary from y^Q- to\\nYQ^o-g- of an ohm or less, according to its size.\\nSuch a low resistance thrown across 110 volts\\nwould cause an enormous current, which would\\ninjure the commutator and brushes by sparking\\nand the armature coils by heating. As the\\nmachine speeds up the resistance may be cut down,\\nbecause the armature, which is turning in a mag-\\nnetic field, produces an electro-motive force oppo-\\nsite to that of the circuit, which tends to cut the\\ncurrent down.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0352.jp2"}, "353": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 331\\nQ. What further protective devices are needed\\nwith motors\\nA. All motors need to be protected from the\\ndanger of being overloaded. An overload, by\\nslowing down the motor, diminishes the back\\nelectro-motive force and therefore allows an excess-\\nive current to flow, which, if long continued,\\nwould burn out the armature. The protection\\nformerly used was a pair of fuses, one in each of the\\ncircuit wires, which were of such a size that they\\nwere expected to blow at any current exceeding\\nthat corresponding to the maximum load for which\\nthe motor was designed. Owing to the uncertain\\naction of fuses, a circ ait-breaker is now almost\\nuniversally used, mounted on the starting-box.\\nAnother thing which must be guarded against is\\nthis: Suppose that the circuit to which the motor\\nis connected is overloaded, perhaps by some\\naccident, and the circuit-breaker of that circuit\\non the switchboard should open. This would\\ncut off current from the motor and it would\\nstop. Now if nothing were done except at the\\nswitchboard to throw in the circuit-breaker\\nagain, we should throw the full voltage on the\\nmotor armature, none of the rheostat being in\\nseries with it, as it had been previously cut out of\\nthe circuit when the motor was first brought up to\\nThe result, of course, Avould be a tre-", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0353.jp2"}, "354": {"fulltext": "332 roper s catechism for\\nmendous flow of current and injury to commu-\\ntator, brushes, and perhaps the armature, depend-\\ning upon how quickly some one opened the switch\\nwhich connected the motor to the circuit. To\\nobviate this difficulty, the rheostat arm has\\nattached to it a spring which tends to pull it back\\nto the position in which all of its coils are in\\nseries with the armature. At the other limit of\\nits motion, where it would stand when all the\\ncoils had been cut out of the circuit, is a magnet\\nwound with fine wire and supplied from the\\ncircuit wires. When the rheostat arm gets to this\\nposition the magnet holds it there by its attraction\\nfor a piece of iron mounted on the arm, as long\\nas the current flows through the coil; but if the\\ncircuit-breaker goes off or the voltage disappears\\nfor any reason, the magnet lets go and the spring\\npulls the rheostat arm back to the position of safety.\\nQ. What are the commercial sizes in which\\nmotors are built?\\nA, i, h 1, 2, 3, 5, 71 10, 15, 20, 25, 50,\\n75, 100, and upward.\\nQ. What are the standard voltages\\nA. 110 to 125, 220 to 250, and 500 to 550.\\nQ. What is a motor- generator\\nA. A combination of motor and generator on\\nthe same shaft. The most easily understood form\\nwould be a motor which might be designed for any", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0354.jp2"}, "355": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 333\\nvoltage, speed, and power, coupled directly to the\\nshaft of a dynamo designed for the same speed,\\nbut for any voltage and the same output as the\\nmotor. Such a machine has two distinct com-\\nmutators, brushes, armatures, and fields.\\nQ. How is this arrangement modified in prac-\\ntice?\\nA. By using a common armature core and field,\\nand putting the two sets of armature windings on\\nthe same core, insulated, of course, carefully from\\neach other.\\nQ. What are some of its principal uses\\nA. 1. To change from a high pressure and small\\ncurrent to a lower pressure and correspondingly\\ngreater current.\\n2. With its generator armature in series with\\nsome circuit to raise the pressure of that particular\\ncircuit higher than that of the other circuits sup-\\nplied from the principal generator. In such uses\\nit is called a booster.\\n3. In connection with storage batteries, it being\\nused in series with the charging mains to increase\\nthe pressure in proportion as the batteries become\\nmore fully charged.\\nIt is also used to a considerable extent in tele-\\nphone exchanges for operating the calling circuits,\\nthe generator end being arranged to give an alter-\\nnating current.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0355.jp2"}, "356": {"fulltext": "334 roper s catechism for\\nSTORAGE OR SECONDARY BATTERIES.\\nQ. Of what does the storage battery, as com-\\nmercially sold, consist?\\nA. Of two lead plates, or sets of plates, im-\\nmersed in a jar containing dilute sulphuric acid,\\nthe plates having the form of grids, the holes in\\nwhich are filled with active material.\\nQ. Of what does this active material consist\\nA. On the positive plate, of peroxide of lead.\\nOn the negative plate, of metallic lead in finely\\ndivided, spongy condition.\\nQ. What do you mean by the positive plate\\nA. Just as with any battery, the plate from\\nwhich current will flow through a conductor con-\\nnecting it to the other plate.\\nQ. How can you tell by the eye which is the\\npositive plate of a storage cell\\nA. By its reddish color.\\nQ. Is there any other way\\nA. Yes; there is always one more negative plate\\nin a cell than there are positive plates.\\nQ. Are the positive and negative plates in con-\\ntact?\\nA. The positives are all joined to each other,\\nlikewise the negatives; but the positives are\\nseparated from the negatives by about of an", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0356.jp2"}, "357": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 335\\ninch, the space between bemg filled with sulphuric\\nacid.\\nQ. What do you mean by the discharge of a\\ncell?\\nA. Allowing it to furnish current, as it will do\\nif the positive and negative terminals are con-\\nnected by a conductor.\\nQ. What are, roughly, the chemical changes that\\ntake place during discharge\\nA. The peroxide on the positive is changed to\\nlead sulphate. The spongy lead on the negative\\nis likewise changed to lead sulphate.\\nQ. What do you mean by charging a cell\\nA: Running a current from some generator\\nthrough the cell in the opposite direction to that\\nof the current which it furnished during dis-\\ncharge.\\nQ. What chemical action takes place\\nA. The reverse of what occurred during dis-\\ncharge. On the positive plates lead sulphate is\\nchanged to lead peroxide and on the negatives to\\nmetallic lead.\\nQ. What pressure is furnished by such a storage\\ncell?\\nA. When fulty charged, about 2.2 volts. This\\ngradually diminishes during discharge to 1. S volts\\nbeyond which point further discharge would injure\\nthe cell.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0357.jp2"}, "358": {"fulltext": "336 roper s catechism for\\nQ. What are the principal sources of trouble,\\nand how are they remedied?\\nA. The principal troubles of storage cells are\\nshort-circuiting, buckling, and sulphating. The first\\nis caused by buckling of plates or by the dropping\\nout of portions of the pencils of active material,\\nwhich in time form between the positive and\\nnegative plates a connection which causes loss of\\ncharge and destruction of the plates if not noticed\\nand remedied by taking out the material. Buck-\\nling is due to an excessive rate of discharge or an\\nunequal discharge at different parts of the plate.\\nTo assist in preventing it the plates are separated\\nby glass or rubber distance-pieces. Sulphating,\\nor the production of a complex, hard, white lead\\nsulphate, is caused by carrying the discharge of\\nthe battery too far or by letting it stand too long\\nwithout recharging. It is remedied by persistent\\ncharging.\\nQ. What are the principal advantages of using\\nstorage cells\\nA. To take care of light loads, thus permitting\\ndynamos, engines, and perhaps a boiler to be shut\\ndown; to maintain a steady pressure; and to take\\ncare of the peak of the load, thus enabling\\nthe machinery to work at a more even load and\\nsecuring greater economy.\\n*See Roper s Engineers Handy-Book, page 755.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0358.jp2"}, "359": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 66 i\\nQ. How are storage cells rated\\nA. By their capacity in ampere-hours. Thus, a\\ncell of 50 ampere-hours is one which when dis-\\ncharged at its normal rate gives out such a number\\nof amperes for such a number of hours that the\\nproduct of the number of amperes by the number\\nof hours equals 50. The capacity of a cell, or the\\nnumber of ampere-hours which can be taken from\\nit without carrying the voltage lower than 1.8 volts,\\nis very much affected by the rate of discharge,\\nbeing much less at a rapid than at a slow rate of\\ndischarge.\\nQ. What is the efficiency of a storage cell, and\\nhow is it measured\\nA. The efficiency of a cell is the ratio between\\nthe amount of power which can be taken out of\\nit and that which is put into it. It, like capacity,\\nvaries with the rate of discharge, and may be\\nanywhere from 50 to 95 per cent., according to\\nthe charge and discharge rates used. Eighty per\\ncent, for the normal discharge-rate of a cell is a\\ngood value except for the very largest cells. To\\nmeasure the efficiency the watt-hours put in dur-\\ning charge are measured by an ammeter and volt-\\nmeter, and, similarly, the watt-hours taken out in\\ndischarge. The quotient of the latter by the\\nformer is the efficiency.\\n22", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0359.jp2"}, "360": {"fulltext": "338 roper s catechism for\\nMETHOD OF CONNECTING STORAGE BATTERIES.\\nOwing to the fact that the electro-motive force\\nof a cell increases with charge and diminishes with\\ndischarge, it is necessary to have special arrange-\\nments by which a dynamo while supplying hghts\\nmay charge a battery of cells, and by which the\\nelectro-motive force of a set of cells may be kept\\nconstant while they are supplying lamps. The\\narrangement for discharge will be first described.\\nSupposing a 110-volt system, we must have a\\nnumber of cells in series equal to volts, or\\nabout 60 cells. When fully charged, as each cell\\nhas an electro-motive force of 2.2 volts, the total\\nelectro-motive force of the 60 cells would be 132\\nvolts, a pressure which would seriously injure the\\nlamps. When the cells are fully charged, there-\\nfore, a sufficient number are switched out of cir-\\ncuit to bring the pressure down to 110 volts. As\\nthe cells discharge and their electro-motive force\\nfalls, these cells are switched back into the circuit\\none at a time, till at the end of the discharge they\\nare all in circuit.\\nIn charging, the electro-motive force rises. As\\nit is desired to run 110-volt lamps and charge the\\ncells at the same time, we cannot raise the pres-\\nsure of the lighting dynamo; so an auxiliary\\ndynamo or booster is employed, its armature being", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0360.jp2"}, "361": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n339\\nput in series with the cells and its field varied by\\nits rheostat so as to give enough additional volts\\nfor charging at the proper rate. The accompany-\\ning diagram of connections shows the arrange-\\nment. B is the booster and R its rheostat. V is\\na voltmeter and A an ammeter, so arranged that", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0361.jp2"}, "362": {"fulltext": "340 roper s catechism for i\\n\u00e2\u0096\u00a0i\\nits needle stands in the center of the scale when no\\ncurrent is flowing through it, moving to one side\\nfor a charging current and to the opposite side for a\\ndischarge current. K represents the main battery\\nand H the switch which throws the reserve cells\\nin and out. S is a double-throw switch, which in\\none position connects the batteries to the lamp to\\nbe supplied with current, and in the other position\\nconnects it to the dynamo for charging. E is sl\\nswitch for connecting the voltmeter, so as to give\\nthe voltage of the battery, the line, and the charg-\\ning dynamo and booster respectively. is an\\nautomatic circuit-breaker, which will operate if\\ntoo great current is taken out of the batteries, and\\nC is a circuit-breaker which will open the circuit\\nif the charging current becomes less than a certain\\nvalue. This last is necessary if a compound-\\nwound dynamo is used in order to protect the\\ndynamo from having a reverse current sent through\\nit from the battery if by accident it was slowed\\ndown or stopped before the charging switch had\\nbeen opened.\\nSeveral other arrangements are employed but\\na proper understanding of the one described above\\nwill be sufficient to enable the engineer to com-\\nprehend the others without difficulty.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0362.jp2"}, "363": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 341\\nELECTRIC SIGNALS.\\nQ. Of what four elements are most signal\\nsystems made up\\nA. Of the battery, line, the operating station,\\nand the receiving mechanism.\\nQ. What is the function of each element\\nA. The battery furnishes the electrical energy\\nfor operating the signals, and the line serves to\\ntransmit this energy. The operating station, which\\ngenerally consists of a key, a switch, or a push-\\nbutton, closes the electrical circuit and permits\\nthe operating current to flow. The receiving sta-\\ntions are somewhat varied in design. They may\\nconsist of a bell or telegraph sounder, giving the\\nsignals by sound, or of a galvanometer or a shutter-\\ndrop, which conveys the signals by means of\\nsight. Frequently the two methods of sound and\\nsight are combined.\\nQ. Of what does an electric bell consist\\nA. Of an electro-magnet, to the armature of\\nwhich is connected a hammer arranged to strike a\\ngong when the armature is pulled up to the core\\nof the magnet by the passage of an electric cur-\\nrent. When current ceases the magnet loses its\\nstrength and a spring pulls the armature away\\nfrom the core and also the hammer from the gong.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0363.jp2"}, "364": {"fulltext": "342\\nroper s catechism for\\nQ. Into what classes are bells divided\\nA. Into single-stroke bells, which make but one\\nstroke each time that circuit is closed, and vibrat-\\ning bells, whose hammer continues to vibrate as\\nlong as circuit is closed.\\nQ. How is a single-stroke bell\\nconnected\\nA. As shown by the solid\\nlines in the cut.\\nQ. How is a vibrating bell\\nconnected\\nA. As shown in the cut, the\\nconnection F-D being considered\\nas removed.\\nQ. Explain the complete ac-\\ntion of the vibrating bell.\\nA. When the button is pressed down, the cir-\\ncuit being closed, current will flow from F to B,\\nB to the contact point C, through the armature\\nE to D, from D through the magnet coil to A,\\nand from A back through the closed push and\\nbattery to F. Owing to the current, the electro-\\nmagnet pulls the armature E toward itself and\\nthe hammer strikes the gong G; but as soon as\\nthe armature moves toward the magnet the circuit\\nis opened, because C no longer touches E. The\\ncurrent therefore stops, and as the electro- magnet\\nno longer has any strength the armature is pulled", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0364.jp2"}, "365": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 343\\naway from it by the spring S. This movement,\\nhowever, brings E and C into contact again, caus-\\ning the whole action to be repeated, and this con-\\ntinues as long as the push-button is held down,\\nprovided the battery keeps up its strength.\\nQ. What three styles of bells are there\\nA. Wooden box, the working parts of which are\\ncovered with wood iron box, when they are cov-\\nered with iron, and skeleton frame, w^hen they are\\nnot covered at all.\\nQ. Show how you would connect three bells to\\nring by one push-button.\\nt A.\\n[T o[::jio[:{iO[]\\nQ. Show how to connect two bells to be rung\\nby either of two pushes.\\nA.\\n41\\nd od\\nQ. Show how you would connect a return call\\nbetween two points.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0365.jp2"}, "366": {"fulltext": "844 roper s catechism for\\nA.\\n\u00e2\u0096\u00a1O\\nill-\\nd\\nQ. What is an annunciator\\nA. The annunciator in principle consists of a\\nnumber of bells mounted together in a case, each\\noperated by its own push located in some distant\\nplace. In practice, however, it would be difficult\\nto tell from the sound of the bells which station\\nwas calling, so the hammers and gongs are\\nomitted, and instead we have a simple mechanism\\noperated by the armature, called the drop.\\nQ. Explain the details of one form of drop.\\nA. It consists of a coil whose armature is an\\niron rod which is sucked up into the coil when\\ncurrent passes through it. This releases a pivoted\\nneedle, which is hung eccentrically so that it turns\\nfrom the horizontal to the vertical position. Each\\nneedle being numbered or otherwise marked the\\npoint from which the signal was sent is, of course,\\nknown.\\nQ. How are the needles restored\\nA. By a rod carrying little stops, which when\\npushed up force the needles back to their original\\nposition.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0366.jp2"}, "367": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS.\\n345\\nQ. What is an automatic set-back annunciator\\nA. One in which this rod is lifted by an electro-\\nmagnet so connected that current flows through it\\nwhen any push-button is pressed. All the needles\\nare pushed back to their horizontal position, after\\nwhich the needle corresponding to the push-button\\nlast pressed turns to the vertical position.\\nQ. Show by a diagram the connections for an\\nautomatic set-back annunciator system.\\nA.\\nSignal Bell.\\nQ. How does the return-call annunciator system\\ndiffer from this\\nA. By the addition of another wire between\\neach push-button and the annunciator.\\nQ. What is a fire-alarm attachment\\nA. A device, frequently added to annunciators\\nfor use in hotels, which closes the circuit of the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0367.jp2"}, "368": {"fulltext": "346 roper s catechism for\\nbells in the rooms, the effect being the same as if\\nall the return- call pushes on the instrument were\\npressed simultaneously.\\nQ. How does a burglar-alarm system differ\\nfrom the ordinary annunciator system\\nA. Burglar- alarm systems are similar to simple\\nannunciator systems, with the addition of a bell\\nin an auxiliary circuit which is closed when any\\nof the drops operate. This auxiliary bell will\\ntherefore continue to ring till some one comes\\nalong and restores the drops to their usual posi-\\ntion with the needles horizontal. The push-\\nbuttons are of a somewhat modified pattern and\\nare placed in doors and window-casings, so that\\nif either a door or window is opened the contacts\\nof the button touch each other and close the\\ncircuit, causing the corresponding drop on the\\ninstrument to operate. Frequently the pushes of\\nall the windows and outside doors of any one\\nroom are connected in multiple on one circuit, so\\nthat any one of them when closed operates the\\ndrop corresponding, it not being necessary to\\nhave a drop for each window and door, but only\\nfor each room.\\nQ. Why are watchmen s clock systems used?\\nA. To insure that watchmen make their rounds\\nat the time and in the order that they are expected\\nto do so.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0368.jp2"}, "369": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 347\\nQ. Into what classes may they be divided\\nA. Into the battery and magneto systems, ac-\\ncording as the energy for actuating the recording\\ndevice is obtained from a battery or from a small\\ndynamo.\\nQ. Explain the arrangement and operation of a\\nbattery system.\\nA. This system is wired like a simple annun-\\nciator system. Its push-buttons are of such\\npattern that circuit will be closed in them only\\nby pushing into them a special key carried by\\nthe watchman. The annunciator of the ordinary\\nsystem, with slight modification, becomes the\\nwatchman s clock, the signal bell and self-restoring\\nmagnet of the annunciator being omitted. The\\narmature of each drop is made to actuate a little\\nneedle which punctures a hole in a paper recording\\ndial. This dial being divided in spaces corre-\\nsponding to the hours from 12 o clock to 12 o clock,\\nand being further subdivided into spaces corre-\\nsponding to five minutes, and rotating so as to make\\none complete turn in the 12 hours, the position of\\nthe punctured holes on the paper tells at what time\\nthey were made by the watchman. The dial has\\nalso a number of circles marked on it correspond-\\ning to the number of stations, and each needle\\npricks its holes in one of the circular spaces\\nformed by these rings, so that a hole in a certain", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0369.jp2"}, "370": {"fulltext": "848 roper s catechism for\\nring means that the ke}^ has been put in the cor-\\nresponding station push-button.\\nQ. What is the weak point of this system\\nA. That if the watchman can get at the two\\nwires leading to any station and can connect them\\ntogether, he can make the clock register as if he\\nhad actually gone to that station.\\nQ. How does the magneto system differ from it\\nA. The wiring, and clock are the same; but\\ninstead of the special push-button to be operated\\nby a key, a little dynamo, called a magneto, is\\nplaced at each station. The watchman carries a\\nhandle which he puts on a stud connected with\\nthe shaft of the dynamo armature. Turning the\\nhandle sends a current through the coil corres-\\nponding at the clock and causes the needle to\\nmake a record.\\nQ. What are the advantages of the magneto\\nsystem\\nA. There are no batteries to be taken care of\\nand the watchman practically cannot make a\\nproper record without going to the station.\\nQ. What kind of batteries are used for operating\\nthe above systems\\nA. Some form of the zinc-carbon sal-ammoniac\\ncell.\\nQ. How many are required for the different\\nsystems", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0370.jp2"}, "371": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 349\\nA. For single bells or annunciators with short\\ncircuits, as in a dwelling-house, three cells are\\nusually sufficient. For larger buildings five or\\nsix will be needed. For automatic fire-alarms a\\nmuch larger number is needed, the exact number\\nbeing stated by the manufacturer, as a rule. For\\nburglar- alarm and watch -clock systems six are, as\\na rule, sufficient, and sometimes a less number\\nmay be used.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0371.jp2"}, "372": {"fulltext": "350\\nROPER S CATECHISM FOR\\nTHE TELEPHONE.\\nThe phenomenon of sound is caused by vibra-\\ntions of the particles of air; its pitch is dependent\\nupon the number of vibrations per second, its\\nloudness on the wideness of those vibrations, and\\nits quality, that property by which we distinguish\\ntones of the same pitch and loudness, upon the\\nform of the vibrations. This last point is some-\\nwhat difficult to understand. Suppose that a\\nmass of air is set in vibration by a tuning-fork,\\nand that we study the motion of a single particle\\nof air by plotting on a flat surface. Let distances\\nto the right of the vertical represent time, and\\nvertical distances represent the distance which the\\nparticle has moved through at any time. The\\nmotion of the particle would be represented by the\\nwavy line in the figure. Distances above the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0372.jp2"}, "373": {"fulltext": "STEAM ENGJNEERS AND ELECTRICIANS. 351\\nhorizontal correspond to motion in one direction\\nfrom its position of rest, and distances below the*\\nhorizontal represent, similarly, motion in the oppo-\\nsite direction. If we set the air into vibration by\\nmeans of a bowed violin- string, the shape of the\\nwavy line would be very much altered, as in the\\nsecond figure. To perfectl}^ reproduce sounds it is\\nnecessary to reproduce the pitch or number of\\nwaves per second and the quahty or form of these\\nwaves, and sufficient wideness of vibration to\\naffect the Hstening ear.\\nThe telephonic transmission of speech between\\ntwo points may be best considered in two parts:\\n(1) The transmitter, which produces in the wires\\nconnecting the two points a varying current\\nwhose curve of variation, if plotted, has the same\\nnumber of vibrations per second, and whose form\\nis the same as that of the sound-waves which\\nstrike upon the diaphragm of the transmitter\\nmouthpiece. (2) The receiver, into which comes\\nthis varying current, which is made to set a dia-\\nphragm into vibrations exactly similar to those of\\nthe transmitter diaphragm. The receiver dia-\\nphragm, of course, sets the air surrounding it into\\nvibrations similar to those caused by the voice\\nspeaking, and the ear of the listener is affected in\\nthe same way, though not so strongly as if the\\nspeaker were talking directly to him.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0373.jp2"}, "374": {"fulltext": "352 roper s catechism for\\nQ. Describe the magneto receiver.\\nA. The magneto receiver consists of a bar mag-\\nnet with a short cylindrical pole-piece of soft iron\\non one end. Mounted on this pole-piece as an\\naxis is a little wooden spool wound with fine wire.\\nIn front of the spool is a thin circular disk of soft\\niron.\\nQ. What improvements have been made in the\\nreceiver\\nA. It is now made with a magnet of horse-shoe\\npattern, each pole having a spool of wire on it.\\nQ. What was the original form of the trans-\\nmitter\\nA. Originally the same instrument was used\\nalternately as transmitter and receiver.\\nQ. Explain the operation when two of these\\nreceivers are connected together by two wires, one\\nbeing spoken into and the other serving as a\\nreceiver.\\nA. The voice of the speaker sets the diaphragm\\nof the transmitter into vibration. The motion of\\nthe iron near the magnet-pole alters the position\\nand density of the magnetic lines of force enclosed\\nby the coil and sets up a varying electro-motive\\nforce in the coil. This produces a current in the\\nline with a variation or wave-form similar to the\\noriginal sound-wave. This varying current flow-\\ning around the coil of the receiver causes the", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0374.jp2"}, "375": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 353\\nstrength of its pull on the receiver diaphragm to\\nvary in a similar way, and therefore to set up in\\nthe receiver diaphragm vibrations similar to those\\nof the transmitter diaphragm. This sets the\\nsurrounding air into similar vibration. This\\ncauses the listener s ear to be affected just as if\\nthe speaker were talking directly in his ear,\\nalthough not so loudly.\\nQ. What form of transmitter is now used\\nA. That which is known as the battery or car-\\nbon transmitter.\\nQ. Explain how it differs from the magneto\\ntransmitter.\\nA. In the magneto transmitter just described\\nthe varying current is produced by setting up an\\nelectro-motive force whose wave-form of variation\\nis similar to that of the sound-wave producing\\nH\\ny^\\nCARBON TRANSMITTER AND CIRCUIT.\\nit. Another way to produce the varying current\\nis to use a constant electro-motive force^- but\\nemploying a resistance varied by the sound-wave\\nand having the same wave-form of variation. A\\ncurrent is sent through the circuit consisting of\\n23", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0375.jp2"}, "376": {"fulltext": "354 roper s catechism for\\nthe receiver, line, and carbon contact, as shown\\nin the diagram. One of the carbon pieces is fixed\\nand the other moves with the diaphragm. When\\nthe latter is spoken against, its vibrations cause\\nthe varying pressures on the contact between the\\ntwo carbon pieces. This causes the varying resist-\\nance, which produces the varying current neces-\\nsary to transmit speech.\\nQ. Do the present forms of transmitter consist\\nof a single carbon contact\\nA. No; in order to make the variation of resist-\\nance as great as possible the number of contacts\\nis increased by having the circuit pass through a\\nnumber of small carbon particles against which\\nthe diaphragm presses.\\nQ. What is the induction coil, and why is it\\nused\\nA. On long lines the resistance of the lines,\\nwhich is fixed in value, is so much greater than\\nthat of the variable carbon contacts that the effect\\nof the latter in varying the total resistance in cir-\\ncuit is practically zero. To overcome this diffi-\\nculty the induction-coil is used. Jt consists of a\\nbundle of fine iron wires about three inches long,\\nand wound around these as an axis is a coarse\\nwire coil of about No. 16 wire and a fine wire\\ncoil of No. 24 or smaller, according to the length\\nof line.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0376.jp2"}, "377": {"fulltext": "STEAM ENGINEEES AND ELECTRICIANS. 355\\nQ, How is the coil connected\\nI A. As shown in the diagram.\\n11=3=^ pC=B\\nIaaaaAa4 /^AA/^AAJ\\nCONNECTIONS USING INDUCTION COILS.\\nQ. What are the methods used in calUng up\\nA. By a battery and ordinary vibrating bell,\\ncalled the battery call, and by a magneto and special\\nbell, called the magneto call.\\nQ. When is the former used\\nA. Generally for distances not exceeding a few\\nhundred feet.\\nQ. On what two systems are telephones oper-\\nated?\\nA. On the intercommunicating system and on\\nthe exchange system.\\nQ. What is the intercommunicating system\\nA. The intercommunicating system consists of\\ninstruments as above described, combined with a\\nsuitable number of wires running to all instru-\\nments, and at each instrument such a form of\\nmechanical-contact changing switch as to enable\\neach telephone station to call up any particular", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0377.jp2"}, "378": {"fulltext": "356 eoper s catechism for\\nstation without interfering with any others who\\nmay be talking.\\nQ. What is the general scheme of wiring for\\nthis system?\\nA. To each instrument as many wires are run\\nas there are telephones in the system, plus two\\n(three in some systems). These wires are prefer-\\nably of different colors, to facilitate making proper\\nconnection.\\nQ. What kind of a call is used\\nA. Either may be employed, but the battery\\ncall is more common.\\nQ. What requirement must a successful inter-\\ncommunicating system fulfil\\nA. That no other act is necessary after finishing\\nconversation than to hang up the receiver on the\\nhook. Some systems require that a lever shall be\\nreturned to a certain point or that a plug shall be\\nput in a certain hole in addition to hanging up\\nthe receiver. Such systems are faulty.\\nQ. How many instruments are used on such\\nsystems\\nA. Any number may be used, but it is rarely\\nadvisable to go above twelve or fifteen, the\\nexchange system being preferable when a greater\\nnumber is required.\\nQ. What is the general nature of exchange\\nsystems", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0378.jp2"}, "379": {"fulltext": "STEAM ENGINEERS AND ELECTRICIANS. 357\\nA. In such systems two (or sometimes three)\\nwires run from each telephone to a central point,\\nat which an operator sits, whose duty it is to con-\\nnect the lines of any two telephones by means of\\na convenient switchboard and to disconnect them\\nwhen they have finished talking. The connections\\nare made through a pair of flexible cords, called\\ntalking-cords, which are attached to plug-shaped\\npieces.\\nQ. How are the subscribers called up\\nA. By either battery or magneto call.\\nQ. What is the general method of operation in\\nan exchange system when one party wishes to talk\\nto another\\nA. See Roper s Engineers Handy-Book,\\npages 771-773.\\nQ. May any number of instruments be con-\\nnected on an exchange system\\nA. Yes; the switchboard is increased as fast as\\nthe addition of instruments renders it necessary.", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0379.jp2"}, "380": {"fulltext": "J", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0380.jp2"}, "381": {"fulltext": "INDEX.\\nAbsolute zero of temperature, 38\\nAcceleration, definition of, 4\\nrelation between mass, force,\\nand, 7\\nAccumulators, electric {see Storage\\nBatteries)\\nAir, 50\\ncompressors, 26\\nflow of, 27\\nmotors, 28\\nvolume of, at various tempera-\\ntures, 53\\nAlloys, 243\\nAlternating currents, 298\\nAltitude measured by barometer, 55\\nby thermometer, 55\\nAmpere, 268\\nAngle of advance or angular ad-\\nvance, 201\\nAnnunciator, electric, 344\\nAnode. 249\\nArc lamps, 320\\nArmatures of dynamos, 299\\nAtmosphere, 52\\nAtmospheric pressure, 52\\nAtomic weights, 237\\nAtoms and molecules, 237\\nAutomatic cut-otf and throttling\\nengines, comparison of, 195\\nengines {see Engines).\\nstoking of boilers, 165\\nAxle, the wheel and, 16\\nBabcock Wilcox boilers, 84\\nBarometer, 54\\nBeams, 246\\nuniformly loaded, 247\\nBearings {see Journals).\\nBells, electric, 341\\nBelting, 20\\nBelts, calculation of width, 20\\nBoiler chimneys and stacks, 167\\ncompounds, 123\\nflues, 160\\nBoiler furnaces, 160\\ngrates, 163\\nmaterials, 98\\nthickness of, 99\\nsetting, 109\\nBoilers, 69\\nautomatic stoking of, 165\\nBabcock Wilcox, 84\\ncare and management of. 111\\nCornish, 77\\ncylindrical, 75\\ntire-tube, 80\\nfiring of. 111\\nGalloway, 80\\ngrate surface per horse-power\\nof, 95\\nimportance of correct supply\\nof air to, 141\\nLancashire, 79\\nlocomotive, 89\\nmarine, 87\\npriming of, 125\\nrating of, 91\\nreturn tubular, 83\\nriveted joints of, 100\\nscale and corrosion in, 123\\ntubular, 81\\nwater-tube, 84\\nBoiling-point of water, 58\\nBourdon steam gauge, 138\\nBrass, 243\\nBronze, 243\\nBurglar alarm, 346\\nBus-bars on electric switchboards,\\nCalorific value of coals, 48\\nCarbon effect on strength of steel,\\n241\\nCards, indicator {see Indicators).\\nCast-iron (see Iron).\\nCathode, 249\\nCentennial rating of boilers, 92\\nCentigrade thermometer scale, 38\\nChemical elements, 236\\n359", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0381.jp2"}, "382": {"fulltext": "360\\nChimneys. 167\\nCircuit breakers, 305\\nClutches, friction, 24\\nCoal, 45, 47\\nCoke, 47\\nCollapsing pressure of boiler flues,\\nrule for, 161\\nColumns, 247\\nCombustibles, relative value of,\\n48\\nCombustion, 44\\nheat of, 48\\nCommutators of dynamos, 298\\nComposition of forces, 11\\nCompound dynamos, 30\\nengines, 191, 192\\nCompressed air, flow of, through\\npipes, 28\\nCompression in engines, 225\\nCompressors, air, 26\\nCondensers, 233\\ninjection water required, 234\\nvacuum of, 234\\nCondensing engines, economy of,\\n188\\nConducting power of substances for\\nheat, 42\\nConduction of heat, 42\\nConductivity, electrical, 270\\nConductors, electrical, 272, 274\\nConservation of energy, 10\\nConvection of heat, 42\\nCopper, 242\\nalloys, 243\\nwire, electrical table, 313, 315\\nCorliss engines, 207\\nCorrosion of boilers, 123\\nCorrugated furnaces and flues, 162\\nCoverings for steam-pipe, 42\\nCurrent, electric, 250, 251, 260, 275\\nunit of, 268\\nCurvilinear seams of boilers, 100\\nCut-off 227\\nautomatic, 195, 207\\nvalves, 207\\nCycloid gears, 24\\nDaniell battery, 295\\nDead center of engines, 143\\nDead-weight safety valve, 130\\nDiagrams, indicator {see Indicator)\\nDraught of chimneys, 167, 171\\nDuctility of metals, 238\\nDynamometers, 33, 36\\nDynamo regulation, 302\\nDynamos, 297\\ncompound, 302\\noperated in parallel, 307\\nseries, 300\\nshunt, 301\\nEccentric, steam engine, 199\\nEccentricity, 200\\nEconouieter, 141\\nEconomizers, 159\\nEdison 3-wire system of electrical\\ndistribution, 311\\nEfficiency of injectors and pumps,\\nrelative, 152\\nof pneumatic power transmis-\\nsion, 28\\nEjector, 151\\nElectric accumulator {see Storage\\nBatteries)\\narc lamps, 320\\nbatteries, 292\\nbells, 341\\ncircuit breakers, 305\\nconductivity, 270\\nconductors, calculation of sizes,\\n313\\ninsulation of, 274\\nmaterials used {see also\\nConductors), 274\\ncurrent, heating effects, 251\\ndistribution of energy, 308\\nparallel system, 309\\nseries system, 309\\n3-wire system, 311\\nsizes of conductors, 313\\ndynamos, 297\\nfuses, 305\\ngenerators, 292, 297\\nground detectors, 305\\nheating, 251\\nincandescent lamps, 323\\nElectric induction coil, 354\\nlighting, 320\\nmotor generators, 332\\nmotors, 327\\nprotective devices for, 331\\npressures used in practice, 332\\nresistance (see Eesistance).\\nsignals, 341\\nstorage batteries, 292, 334\\nswitches, 303, 305, 319\\ntelephones, 350\\ntransformer, 265\\nunits, 267", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0382.jp2"}, "383": {"fulltext": "361\\nElectric wires, tables of weights and\\ndiameters, 315\\nwiring, 316\\nElectrical experiments, fundamen-\\ntal, 248\\nmeasurement, 285\\nmethod of power measurement,\\n34\\ntransmission of power, 29\\nElectrolysis, 248\\nElectro-magnet, 262\\nElectro-motive force, 266, 267, 278\\nElectro-plating, 250\\nElements, the six mechanical, 1\\nEnergy, conservation of, 10\\ndefinition of, 8\\nforms of, 8\\nsources of, 10\\nEngine, steam (see Steam engine), 175\\nExhaust, steam engine, 227\\nExpansion curve, 227\\nFactors of safety, 105, 245\\nFahrenheit thermometer scale, 38\\nFalling bodies, motion of, 7, 8\\nFeed-pumps (see Pumps).\\nFeed-water, advantages of heating,\\n153\\nheaters, 154\\nadvantages of each type, 158\\nclosed type, 155, 156\\nopen type, 155, 157\\nBerryman, 156\\nPittsburgh, 157\\nrelative advantages of pumps\\nand injectors for supplying,\\n152\\nField, magnetic, 254\\nFiring of boilers, 163\\nautomatic, 165\\nFittings, boiler, 128\\nFleming s rule for direction of in-\\nduced electrical currents, 260\\nFlow of air, 28\\nof Avater, 61\\nFlues of boilers, 160\\nFoaming of boilers, 123\\nForce, definition of, 1\\nmagnetic lines of, 254\\nrelation between mass, accelera-\\ntion, and, 10\\nForced draught, 210\\nrepresentation by lines, or\\ngraphically, 11\\nresultant of two or more, 11\\nForces, parallelogram of, 11\\nFoundations of engines, 213\\nFuels, 4\\nFulcrum, 14\\nFurnaces of boilers, 160\\nFuses, 305\\nFusibility of metals, 238\\nGalvanometer, 258\\nGauge cocks, 141\\nGauges, 138\\nvacuum, 139\\nsteam pressure, 138\\nwater, 140\\nGearing, 23\\nGerman silver, 243\\nGovernors for steam engines, 209\\nGrates for boilers, 163\\nGrate surface of boilers, 95, 164\\nGravity, specific, 239\\nGround detectors, 305\\nHancock inspirator, 151\\nHeat, conduction of, 42\\ndefinition of, 37\\nlatent, 41\\nmechanical equivalent of, 42\\nof combustion, 48\\nradiation of, 42\\nspecific, 4\\ntransference of methods, 42\\nunit of, 41\\nHeaters, feed-water (see Feed-water\\nHeaters).\\nHeating due to electric currents,\\n251\\nsurface of boilers, 95\\nHorse-power, indicated, 229\\nof boilers {.lee Centennial Rat-\\ning).\\nof steam engines, calculation\\nof, by indicators, 229\\nrules for calculating, 177\\ntables for different speeds\\nand pressures, 184\\nHydrogen, 51\\nin fuel, 45\\nHydrometer, 240\\nIce, weight of cubic foot, 57\\nIncandescent lamps, 323\\nlife and efficiency of, 325\\nIncrustation and scale {see Cor-\\nrosion of Boilers).", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0383.jp2"}, "384": {"fulltext": "362\\nIndicated horse-power (see Horse-\\npower).\\nIndicator cards or diagrams, 226\\nfunction of, 225\\nmethod of power measurement,\\nof using, 226\\nsteam engine, 224\\nTabor, 225\\nInduction coil, electric, 354\\ncurrents of electricity, 264\\nInertia, 2\\nInjectors, 146\\naction of, 146\\nfailure of, 149\\nstarting, 149, 150\\nsetting up of, 150\\nvs. pumps, 152\\nInsulation of electric wires, 274\\nInsulators, 274\\nIntercooler, 26\\nInvolute gears, 24\\nIron, 240\\nexpansion of, due to heat, 242\\nstrength of, 245\\nvariation of strength due to\\nheating, 242\\nwire {see Wire).\\nelectrical tables, 315\\nJet condensers, 233\\nJoints, riveted, 106\\nKinetic energy, 8\\nLamps, arc, 320\\nincandescent, 323\\nLap of a slide valve, 200\\nLatent heat, 41\\nLaws of motion, Newton s, 3\\nLead, 243\\nof slide valve, 200\\nLeather belts, 20\\nLeclanche battery, 294\\nLever, safety valve, 130\\nLevers, 14\\nrules for calculation, 15\\nLifters or ejectors, 151\\nLifting ejectors {see Injectors).\\nLines of force, 254\\nused to represent forces 11\\nLink motion, 206\\nLiquid fuels, 49\\nLocomotive boilers, 87\\nLongitudinal seams, 100\\nLoss of head of water in pipes, 62\\nLow-pressure cylinders {see Com-\\npound Engine).\\nLubrication, 32\\nMachines, elenients of, 1\\npurpose of, 1\\nMagnets, electro-, 262\\nMagnetic field, 254\\nlines of force, 254\\nMalleability of nieials, 232\\nMarine boilers, 87\\nMass, definition of, 6\\nrelation between force, accelera-\\ntion, and, 7\\nrelation of weight to, 6\\nMaterials and their properties, 236\\nstrength of, 244\\nMean eflTective pressure obtained\\nfrom the indicator,\\ncard, 229\\nof steam engines, 181,\\n229\\nMeasurement of heights by barom-\\neter, 55\\nby thermometer, 55\\nMechanical elements, 1\\nequivalent of heat, 42\\nfiring of boilers, 165\\nMechanics, 1\\nMetals, 240\\nprincipal properties of, 238\\nMethods of transmitting power, 18\\nMil, circular, 316\\nMoisture in steam, 64, 65\\nMolecules and molecular construc-\\ntion of matter, 23\\nMoment, 13\\nMomentum, definition of, 7\\nMotion, 3\\nNewton s laws of, 3\\nof falling bodies, 5\\nperpetual, 4\\nMotors, electric {see Electric\\nMotors).\\nNewton s laws of motion, 3\\nNitrogen, 45, 51, 236\\nNon-condensing engine, 188\\nNon-conducting covering for steam-\\npipes, 43\\nNon-conductors, 274\\nOhm s law and its applications, 280", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0384.jp2"}, "385": {"fulltext": "363\\nOil separators, 32\\nused as a fuel, 49\\nOils aud lubrication, 32\\nOrdiuates, 230\\nOver-compounded dynamos, 301\\nOver-travel of a valve, 200\\nOxygen, 45, 51, 236\\nPacking for steam engines, 217\\nParallel system of electrical dis-\\ntributiou, 308\\nParallelogram of forces, 11\\nPerpetual motion, 4\\nPetroleum as a fuel, 49\\nPipe coverings, materials for, 43\\nPipes, flow of air in, 28\\nof water in 62\\nPiping of engines, 216\\nPiston valves, 207\\nPitch of gears, 23\\nPlanimeter and its use, 229\\nPneumatic transmission of power,\\n25\\nPorts or passages, steam, 197\\nPotential energy, 8\\nPower, definition of, 10\\nhorse-power {see also Horse-\\npower), 10\\nmeasurement, 33\\nof steam engines, calculation\\nof, 177\\ntables of, 184\\ntransmission by gearing, 23\\nby ropes, 22\\nby shafting, 18\\nelectrical, 29\\nmethods of, 18\\npneumatic, 25\\nPressure, electric, 266, 267, 278\\nmean effective, 181, 229\\nPriming of boilers, 123\\nProny brake, 35\\nPuUev, as a mechanical element,\\n16\\nrule for calculating gain in\\nforce, 17\\nPumps, 142\\nboiler- feed, 143\\ncapacity of, 145\\nclassification of, 142\\ndirect-acting, 143\\nduplex, 144\\nelectric, 143\\nfly-wheel, 143\\nfor hot water, 146\\nPumps, lift of, 144\\npower, 142\\npower required by, 145\\nvs. injectoi s, 152\\nPurifying feed-water, 153\\nKadiation of heat, 42\\nReaumur thermometer scale, 38\\nKeceivers, compressed air, 27\\nelectric telephone, 352\\nReciprocating parts of steam en-\\ngines, 195\\nRelease, 200\\nReleasing valve gear, 207\\nReservoirs for compressed air, 27\\nResistance, change with change of\\ntemperature, 270\\nelectric, 251, 270\\nspecific, 272\\nResistances in multiple, 271\\nReversing valve-gears, 206\\nRiveted joints of boilers, 106\\nRope-driving, 22\\nRubber belting, 20\\nRust, 51\\nSafe current-carrying capacity of\\ncopper wires, 318\\nSafety, factors of, 105, 245\\nvalves, 128\\nSalinometer, 141\\nScale in boilers, 123\\nScrew as a mechanical element, 1\\nSeams, curvilinear, 100\\nlongitudinal, 100\\nSeparators, 171\\nSeries dynamos, 300\\nsystem of electrical distribu-\\ntion, 308\\nSetting boilers, 109\\nShaft-governors, 211\\nShafting calculation of sizes, 19\\nShunt dynamos, 300\\nSlide valves, 197\\nSmoke-stack {see Stacks and Chim-\\nneys).\\nSpecific gravity, 60, 239\\nheat, 4\\nresistance, 272\\nStacks for boilers, 167\\nproportioning of, 168\\ntable of sizes for various sizes\\nof boiler, 170\\nSteam, 64", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0385.jp2"}, "386": {"fulltext": "364\\nsteam boilers {see Boilers),\\ndry {see also Separators), 65\\nengine, 175\\nadvantages of high speed,\\n194\\nbrake, horse-power of, 177\\ncare and management of,\\n217\\nclassification of, 188\\ncompound, 191\\ncondensing and non-con-\\ndensing, 188\\nCorliss, 207\\ncut-offs, 207\\nfoundations, 213\\ngovernors, 209\\nhigh- and low-speed, 194\\nindicated horse-power of,\\n177, 229\\ntables of, at different\\npiston speeds, 184\\nindicator {see also Indi-\\ncator), 224\\ninvention of, 175\\nknocking in, 221\\nlining up, 214\\nlocation of, 214\\nmean effective pressure of,\\n181, 229\\npiping for, 216\\nreciprocating parts of, 195\\nrotary, 196\\nsetting valves of, 205\\nsingle-acting, 196\\nand double-acting, 196\\nand multiple expan-\\nsion, 192\\nthrottling and automatic\\ncut-off, 195\\nvalves and valve-gears, 197\\nlatent heat of, 66\\nmoisture in, 64\\npipe-covering, 43\\npiping for engines, 216\\nsaturated, 45\\nseparators, 171\\nsuperheated, 45\\ntotal heat of, 67\\ntraps, 171\\nSteel, 241\\nStoking, automatic, 166\\nStorage batteries, 292, 334\\nStrength of materials, 244\\nString of indicator diagram, 230\\nSurface condensers, 233\\nSwitchboards, electric, 304\\nSwitches, electric, 303\\nTabor indicator, 225\\nTeeth, gear teeth forms, 23\\nTelephone, 350\\nTemperature, definition of, 38\\nTenacity of metals, 238\\nTensile strength, 244\\nTheoretical indicator diagram, 227\\nThermal unit, 44\\nThermometers, 38\\nThree-wire system of electric dis-\\ntribution, 311\\nThrottling and automatic cut-off\\nengines, 195\\nThrow of eccentrics, 200\\nTimber, strength of, 245\\nTime systems, watchmen s, 346\\nTotal heat, 67\\nTransference of heat, 42\\nTransformers, 265\\nTransmitter, electric telephone, 353\\nTransmission of power {see Power).\\nTravel, 200\\nTraps, steam, 171\\nTubular boilers {see Boilers).\\nUnit of heat, 41\\nof work, 8\\nUnits, electric, 267\\nVacuum of condensers, 234\\ngauges, 139\\nValve circle, 202\\ngears {see also Cut-off), 197\\nreleasing, 207\\nreversing, 205\\nthe link motion, 205\\nvariable cut-off and revers-\\ning, 205\\nZeuner s diagram for, 202\\nValves and valve-gears, 197\\nbalanced, 207\\ndifferent varieties of, 207\\nfriction of, 206\\nhow to set, 205\\nlap and lead of, 200\\npiston, 207\\nplain slide, 197\\nsafety, 128\\nsemi-rotary, 207\\nseparate, for admission and ex-\\nhaust, 207\\nsetting of, 205", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0386.jp2"}, "387": {"fulltext": "365\\nVelocity, 4\\nVolt, the, 267\\nWatchmen s time systems, 34\\nWater, boiling point of, 58\\ncolumns, 140\\ncomposition and properties,\\n56\\ndecomposition of, 59\\nflow of, 61\\nspecific gravity of, 59\\nheat of, 58\\nweight of, at diflferent tempera-\\ntures, 56\\nWedge, the, 16\\nWeights, atomic, 237\\nWheel and axle, the, 16\\nWire calculation of sizes for electric\\ndistribution, 313\\nelectric, tables of weights and\\ndiameters, 315\\nproperties of copper, 315\\nsafe-current carrying capacity\\nof, 313\\nWiring, electric, 316\\nWork, definition of, 8\\nunit of, 8\\nWrought-iron {see Iron).\\nZero, absolute, 38\\nZeuner s diagram for valves, 202", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0387.jp2"}, "388": {"fulltext": "Ll.Ai St?", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0388.jp2"}, "389": {"fulltext": "", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0389.jp2"}, "390": {"fulltext": "", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0390.jp2"}, "391": {"fulltext": "", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0391.jp2"}, "392": {"fulltext": "", "height": "2840", "width": "1804", "jp2-path": "roperscatechismf00rope_0392.jp2"}}