LIBRARY 
 
 UNIVERSITY OF CALIFORNIA. 
 
 \ Class J 
 
WORKS OF 
 PROFESSOR FORREST JONES 
 
 PUBLISHED BY 
 
 JOHN WILEY & SONS 
 
 The Gas Engine. 
 
 ix + 447 pages, 142 figures. 8 vo, cloth, $4.00. 
 
 Machine Design. Part I. Kinematics of 
 Machinery. 
 
 Fourth Edition, Revised. vi + 182 pages, 134 
 figures. 8vo, cloth, $1.50. 
 
 Machine Design. Part II. Form, Strength, 
 and Proportions of Parts. 
 
 Third Edition, Revised and Enlarged. ix + 
 4 U pages, 186 figures. 8vo, cloth, $3.00. 
 
THE GAS ENGINE 
 
 BY 
 
 FORREST R. JONES 
 
 FIRST EDITION 
 FIRST THOUSAND 
 
 NEW YORK 
 JOHN WILEY & SONS 
 
 LONDON : CHAPMAN & HALL, LIMITED 
 1909 
 
COPYRIGHT, 1909, 
 
 BY 
 FORREST R. JONES 
 
 Stanhope Ipress 
 
 F. H. CILSON COMPANY 
 BOSTON. U.S.A. 
 
PREFACE. 
 
 THE following discussion of gas and oil engines is presented in 
 the manner which it is believed is the most suitable for a text- 
 book for class instruction and for directing laboratory experi- 
 mentation, as well as for meeting the needs of those who wish to 
 learn to operate commercially and to test. The general con- 
 secutive order is: Descriptive, operative, testing for faults, 
 theoretical, results of trials. The latter portion deals some- 
 what briefly with thermodynamics and theoretical cycles. 
 
 Gas producers are considered briefly from both the practical 
 and theoretical viewpoints, the aim being only to give a clear 
 insight of the principles and methods of manufacturing gas for 
 power purposes. 
 
 The methods of locating and eliminating troubles have been 
 given in considerable detail. The writer's experience in training 
 something more than a hundred men in the commercial operation 
 of gas and oil engines has been fully convincing as to the need 
 of complete instruction in this particular. 
 
 The illustrations are, with one or two exceptions, representative 
 of American practice, but the text is based on information gained 
 by personal observation of motors in Germany, Belgium, France, 
 and England, as well as operating experience in America. 
 
 The proof was kindly read by Mr. Charles E. Ferris, Professor 
 of Mechanical Engineering, and the electrical portion also by 
 Mr. Charles E. Perkins, Professor of Electrical Engineering, both 
 in the University of Tennessee. The criticisms and suggestions 
 of these gentlemen led to important modifications and additions. 
 
 F. R. J. 
 
 DECEMBER 21, 1908. 
 
 iii 
 
 195087 
 
CONTENTS. 
 
 CHAPTER I. 
 
 PAGE 
 
 TYPES OF MOTORS, IMPULSE FREQUENCY, SCAVENGING, REVERSING. i 
 
 i. Introductory. 2. Beau de Rochas- or Otto-cycle motor. 3. Four- 
 cycle motors. 4. Auxiliary exhaust port. 5. Atkinson four-cycle 
 motor. 6. Complete expansion gas engine. 7. The Nuremberg and 
 Gobron-Brillie motors. 8. Two-cycle motors. 9. Koerting two-cycle 
 motor. 10. Brayton motor and cycle, n. Oil-burning motors. 
 12. Hornsby-Akroyd oil motor. 13. Oil-burning motor with bulb 
 ignition. 14. Diesel oil motor. 15. Pioneer types. 16. Scavenging. 
 17. Compound motors. 18. Impulse frequency for different arrange- 
 ment of cylinders. 19. Reversing the rotation of the motor. 
 
 CHAPTER II. 
 
 CARBURATION, CARBURETERS, PREHEATING THE CHARGE, FUEL SUPPLY 47 
 
 20. Carburation of air. 21. Primer for carbureter using volatile 
 fuel. 22. Float-feed carbureter. 23. Pump-feed spray carbureters. 
 24. Pump-feed carbureter with measuring cup. 25. Disk-feed spray 
 carbureter. 26. Diaphragm-feed spray carbureter. 27. Spray car- 
 bureters in general. 28. Other types of carbureters for naphtha 
 and gasoline. 29. Cooling effects of vaporization. 30. Heating the 
 carbureter or the air. 31. Carbureters for kerosene and other non- 
 volatile liquids. 32. Early and obsolete forms. 33. Effect of pre- 
 heating the charge on the power of the motor. 34. Fuel supply for 
 carbureters. 
 
 CHAPTER III. 
 
 IGNITION 63 
 
 35. General. 36. Double ignition. 37. Low-tension electric arc igni- 
 tion. 38. Sources of electric supply for ignition. 39. Low-tension 
 arc igniter with solenoid circuit breaker. 40. Oscillating electric gen- 
 erator for low-tension ignition. 41. Induction coil for low-tension 
 intermittent current. 42. High-tension jump-spark electric ignition 
 in general. 43. Spark plugs. 44. Timers for high-tension electric 
 ignition. 45. Induction coils for electric ignition. 46. Electric bat- 
 teries. 47. Dry batteries. 48. Series and multiple batteries. 49. Mul- 
 tiple series batteries. 50. Arrangement of batteries for ignition. 
 51. Recuperation of dry cells. 52. Storage batteries, accumulators, 
 secondary batteries. 53. Comparison of dry cells and storage bat- 
 teries for ignition purposes. 54. Testing electric batteries. 55. Wir- 
 ing scheme for single-acting, single-cylinder motor with jump-spark 
 ignition. 56. Wiring scheme for motor with more than one combus- 
 
 v 
 
vi CONTENTS 
 
 IGNITION Continued PACK 
 
 tion chamber. 57. Jump-spark ignition with .high-tension distrib- 
 uter. 58. Comparison of multi-induction coil and high-tension dis- 
 tributer systems. 59. Jump-spark ignition in two cylinders with one 
 induction coil and no distributer. 60. Magneto generator for jump- 
 spark ignition. 61. Low-tension magneto and separate transformer 
 system. 62. High-tension magneto. 63. Dynamo-battery ignition 
 system. "Floating the battery on the line." 64. Hot-tube ignition. 
 65. Hot-metal igniter heated by internal combustion. 66. Hot-wire 
 and platinum-sponge igniters. 
 
 CHAPTER IV. 
 
 CONTROL OF POWER AND SPEED 115 
 
 67. General methods. 68. Fuel control. General. 69. Fuel control 
 in four-cycle gas or vapor motor. 70. Governing and hand control. 
 71. Hit-or-miss governing. 72. Hit-or-miss governing by omitted open- 
 ings of the mixture inlet valve. Four-cycle motor. 73. Hit-or-miss 
 governing by keeping the exhaust valve open during the suction stroke. 
 
 74. Keeping the exhaust valve closed during the exhaust stroke. 
 
 75. Keeping the fuel valve closed and opening the mixture inlet valve 
 to admit air. 76. Modern modified method of cutting out charges. 
 77. Governing by varying the amount of fuel admitted for an explo- 
 sion. 78. Throttling. 79. Governing by the mixture inlet valve to 
 reduce the charge. 80. Governing by fuel valve to reduce the charge. 
 81. Governors. General. 82. Hydraulic governors. 83. Hand 
 control of speed and power. General. 84. Early and late ignition. 
 Definitions. 85. Early and late ignition effects on power and speed. 
 86. Time of ignition as affected by degree of compression. 87. Lag 
 in jump spark ignition apparatus. 88. Hand control by throttle and 
 spark. 89. Combined hand control and governing. 90. Compara- 
 tive accuracy of methods of governing. Speed variation in cut-out-of- 
 charge governing. 91. Speed variation with throttle governing. 
 92. Uniformity of speed in two-cycle, governed motor. 
 
 CHAPTER V. 
 COOLING THE MOTOR 162 
 
 93. General. 94. Air cooling. 95. Water cooling. Thermal circula- 
 tion. Circulating pump. 96. Water-cooled pistons and valves. 
 97. Oil cooling. 98. Gaskets and packing materials. 99. Pump 
 packing. 
 
 CHAPTER VI. 
 
 LUBRICATION OF MOTOR 171 
 
 100. Oils and methods of applying. 101. Lubricators. 
 
 CHAPTER VII. 
 
 DISPOSAL OF EXHAUST GASES 177 
 
 102. Precautions. 103. Silencing the exhaust. 104. Subterranean 
 mufflers and silencers. 105. Exposed muffler. 106. Submerged ex- 
 haust pipe. 107. Muffler cut-out. 108. Momentary back pressure. 
 
CONTENTS vii 
 
 CHAPTER VIII. 
 STARTING AND ADJUSTING THE MOTOR 181 
 
 109. Methods of starting, no. Relieving compression, in. Prepara- 
 tions. 112. Starting small gas motor by cranking. 113. Starting 
 small gasoline motor by cranking. 114. Starting a large gas 
 motor by external power. 115. Starting the motor by its own 
 impulse. 116. Starting on "compression." 117. Starting by firing 
 blank cartridge in cylinder. 118. Stresses due to starting motor 
 by its own impulse. 119. Compressed air for starting. 120. Starting 
 single-cylinder, single-acting motor by compressed air. 121. Start- 
 ing motor with more than one combustion chamber by compressed air. 
 122. Lubricator adjustment. 123. Cooling- water adjustment. 124. Ad- 
 justing spray carbureters and the ignition. 125. Rich and lean fuel 
 mixtures. 126. Rough adjustments for black smoke and backfiring. 
 127. Adjustment of a cut-out-governed motor. 128. Adjustment of a 
 throttle-governed motor. 129. Adjustment of a variable-speed motor 
 with hand control. 130. Adjustment of carbureter on an automobile. 
 
 131. Adjustment of carbureter and ignition on a launch motor. 
 
 132. Adjustment of fuel mixture in gas and oil motors. 
 
 CHAPTER IX. 
 
 SETTING OR TIMING THE VALVES AND IGNITER 200 
 
 133. Marks for valve setting. 134. Testing valve timing. 135. Locating 
 dead centers of motor. 136. Time at which a valve should open and 
 close. 137. Marking the fly wheel for valve setting. 138. Effect of 
 worn and loose parts. 139. Adjusting the ignition timer. 140. Com- 
 paring the time of ignition in different cylinders. 
 
 CHAPTER X. 
 TROUBLES, REMEDIES AND REPAIRS 210 
 
 141. General. 142. Conditions that cause troubles and loss of power. 
 143. Backfiring. 144. Misfiring. 145. Pounding, thumping, or ham- 
 mering. 146. Preignition and sharp snaps or heavy pounding. 
 147. Power decreases rapidly at a uniform rate. 148. Power 
 decreases slowly. 149. Erratic behavior. 150. Motor does not 
 develop full power. 151. Motor runs well, then loses power and 
 cooling water heats unduly. 
 
 CHAPTER XI. 
 TESTS OF IGNITION SYSTEMS 221 
 
 152. High-tension (jump-spark) system with induction coils. 153. High- 
 tension distributer system with duplicate batteries. 154. High-tension 
 magneto system. 155. Low-tension arc-ignition system. 156. Test 
 of magneto direct-current electric generator. 157. Direct-current 
 electro-magnetic generator. 158. Shuttle- wound electric generators. 
 159. Test of oscillatory generators. 160. High-tension electric gen- 
 erators. 
 
 CHAPTER XII. 
 TESTS FOR AIR AND GAS LEAKS IN MOTOR 230 
 
 161. Examination for leaks while the motor is running in service. 
 162. Running tests for various leaks. 163. Hand compression tests 
 for leaks. 164. Compressed-air test. 165. Hydrostatic test. 
 
viii CONTENTS 
 
 CHAPTER XIII. PAGK 
 
 CLEANING AND MISCELLANEOUS 235 
 
 1 66. Carbon deposit in cylinder. 167. Cleaning the spark plug. 168. Pit- 
 ting and warping of the exhaust valve. 169. Regrinding a valve. 
 170. Running the motor with a disabled valve. 171. Carbureter re- 
 pairs. Water-logged float. 172. Removing frost and ice from the 
 carbureter. 173. Pipe stoppages by gaskets and loose hose linings. 
 174. Cracked cylinder or cylinder head. 175. Leaky piston. Scored 
 cylinder. 176. Care and handling of combustibles. Removing water. 
 
 CHAPTER XIV. 
 INDICATOR CARDS FROM PRACTICE 245 
 
 177. General. 178. Indicator cards representing American practice. 
 179. Diagrams showing abnormal pressures. 180. Incorrect valve 
 setting as shown by the diagram. 181. Momentary back pressure. 
 182. Variation of time of ignition as shown on card. 183. Dilute mix- 
 ture effect on card. 184. Variation of compression effects. 185. Speed 
 variation effects on diagram. 
 
 CHAPTER XV. 
 
 ECONOMY AND EFFICIENCY 276 
 
 186. Units of heat energy and mechanical energy. 187. Motor economy 
 defined. 188. Motor efficiency defined. 189. Impulse-output effi- 
 ciency. 190. Mechanical efficiency. 191. Thermodynamic or ther- 
 mal efficiency. 192. Plant economy and efficiency. 193. Compari- 
 son of efficiencies. 
 
 CHAPTER XVI. 
 
 PHYSICAL PROPERTIES OF GASES. . . . ; 284 
 
 194. Introductory. 195. Density and weight of gases. 196. Laws of a 
 perfect gas. 197. Example. 198. Specific heat of gases. 199. Ex- 
 ample. 200. Volumetric specific heat. 201. Example. 
 
 CHAPTER XVII. 
 
 COMBUSTION AND HEAT VALUES 293 
 
 202. Combustion and change of specific volume due to combustion. 
 203. Complete and incomplete combustion. 204. Heat of combustion is 
 constant. 205. Heat value or calorific power. 206. Economy and 
 efficiency of motor as affected by calorimeter determinations of heat 
 values. 207. Higher, or effective, heat values. 208. Higher heat 
 values of hydrogen. 209. Lower heat values. 210. Illuminants. 
 211. Saturated and unsaturated hydrocarbons. 212. Physical form of 
 hydrocarbons. 213. Dissociation of chemical compounds. 214. Com- 
 bustion pressures and temperatures. 215. Rate of flame propagation 
 and combustion. 216. Unusual pressures of combustion. 217. Over- 
 rich mixture. 218. Moisture in air and gas. 219. Gas analyses rela- 
 tive to moisture. 
 
CONTENTS ix 
 
 CHAPTER XVIII. PAGE 
 
 FUELS AND GAS MAKING 326 
 
 220. General. 221. Retort gas. 222. Air gas. 223. Water gas. 224. Pro- 
 ducer gas. 225. Suction producer. 226. Theoretical case of gas 
 producer. 227. Computations for theoretical gas producer. 228. Com- 
 parative heat losses for burning carbon to CO or CO 2 . 229. Fuels 
 for continuous suction producers. 230. Pressure gas producers for 
 continuous operation. 231. Down-draught continuous producer. 
 232. Under-feed continuous producer. 233. Air-and-carbon dioxide 
 continuous process. 234. Combined pressure and suction producer. 
 235. Miscellaneous types of producers. 236. Intermittent gas-making 
 processes. 237. Twin producers. 238. Blast-furnace gas. 239. Coke- 
 oven gas. 240. Oil gas from petroleum. 241. Gasoline gas or car- 
 bureted air. 242. Tar destruction. 243. Variation in quality of 
 producer gas. 244. Observation of quality of gas from a producer. 
 245. Continuous calorimeter tests of gas. 246. Efficiency bases of gas 
 producers. 
 
 CHAPTER XIX. 
 
 PRESSURE-VOLUME DIAGRAMS 367 
 
 247. Equations for work. 248. Pressure-volume diagram for complete 
 cycle. 249. Indicator diagrams. 
 
 CHAPTER XX. 
 
 THEORETICAL HEAT CYCLES 374 
 
 250. Assumption for theoretical cycles. 251. Notation. 252. Addi- 
 tional laws of a perfect gas. 253. Relation between specific heat of 
 constant pressure and of constant volume. 254. Thermodynamic 
 changes. 255. Isometric change. 256. Isobaric change. 257. Iso- 
 thermal change. 258. Adiabatic change. 259. Comparison of ex- 
 pansion and compression lines. 260. Theoretically perfect Otto cycle. 
 261. Equations for Otto cycle. 262. Efficiency as affected by varia- 
 tion of compression. 263. Effect of variation of specific volume on 
 account of combustion. 264. Effect of different specific heats of 
 charge and products. 265. Effect of change of ratio of specific heats 
 by combustion. 266. Effect of imperfect gas. 267. Other causes 
 that modify theoretical cycle. 268. Modified theoretical Otto cycle. 
 269. Theoretical Brayton cycle. "270. General equations for thermo- 
 dynamic change. 271. Other thermodynamic cycles. 
 
 CHAPTER XXI. 
 RESULTS OF TRIALS 404 
 
 272. Introductory. 273. United States Government tests. 274. Test of 
 a 5oo-horsepower gas-engine plant. 
 
 CONVERSION TABLES 432 
 
OF THE 
 
 UNIVERSITY 
 
 OF 
 
 THE GAS ENGINE 
 
 CHAPTER I. 
 
 TYPES OF MOTORS, IMPULSE FREQUENCY, SCAVENGING, 
 REVERSING. 
 
 i. Introductory. In the operation of the internal-combustion 
 motor of the reciprocating piston type, fuel is rapidly burned, or 
 exploded, in an enclosed space, and the increase of pressure 
 thus produced is utilized to drive out a piston which is connected 
 more or less directly to a crank shaft, so that the energy of com- 
 bustion is transmitted to the latter in such a manner as to cause 
 it to rotate and have capacity to deliver power for the performance 
 of useful work. 
 
 In nearly all of the smaller internal-combustion motors, a 
 single piston reciprocates in the round bore of a cylindrical part, 
 the cylinder, which is closed at one end, completely and per- 
 manently in some types, and in other types is pierced with ports 
 for the admission of the charge and the expulsion of the gaseous 
 products of combustion. These ports are intermittently closed 
 by valves. The end of the cylinder next the crank shaft is left 
 open. In such a construction the piston is long, of the type 
 called a "trunk piston." 
 
 In modern designs the enclosed space at the end of the cylinder 
 and into which the piston does not enter is called the " com- 
 bustion chamber." The name " compression space " is also 
 applied to it for the reason that, in modern practice, a cylinderful 
 of combustible mixture is compressed into it before burning. 
 
 There are several modifications of and variations from this 
 simple form of motor, the more important of which will be con- 
 sidered later. 
 
2 THE GAS ENGINE 
 
 The parts of the motor with which the hot gases come in con- 
 tact receive considerable heat from the gases. Unless some 
 means is provided for cooling these parts, they become too hot 
 for satisfactory operation. This applies especially to the parts 
 
 FIG. 1. 
 
 Section of Single-Cylinder, Single-Acting, Four-Cycle Motor with Diagrammatic 
 Arrangement of Carbureter and Ignition System. 
 
 The float in the carbureter reservoir has a needle valve at the top which closes the 
 opening of the gasoline supply pipe when the float rises and maintains a constant 
 level of the gasoline lower than the spray nozzle in the air passage. 
 
 The gear on the cam shaft is twice the diameter of its mate on the crank shaft, so 
 that the cam shaft rotates at half the speed of the crank shaft. The cam lifts 
 the exhaust valve and holds it open during every second upstroke of the piston. 
 
 The rotor of the timer is on the cam shaft and closes the battery circuit every second 
 revolution of the crank shaft. 
 
TYPES OF MOTORS 
 
 enclosing the combustion chamber and the port through which 
 the spent gases pass out from the motor cylinder. 
 
 In small motors, some are cooled by water, some by oil, and 
 some, a minor number, by air. 
 Large motors are always water or 
 oil cooled. 
 
 When water or oil is used for 
 cooling, a jacket of the cooling 
 liquid surrounds the combustion 
 chamber more or less completely, 
 and also part of the bore of the 
 cylinder. The water or oil is circu- 
 lated through the jacket space in 
 most designs. In some it is not circulated. 
 
 FIG. 2. 
 Piston. Trunk Type. 
 
 FIG. 3. 
 Piston Rings. 
 
 The larger ring shows a cut to allow 
 the ring to expand against the cylin- 
 der wall to make a tight fit. The joint 
 at the cut is made so that the sur- 
 faces parallel to the ends of the ring 
 bear together to make the joint tight. 
 The ring must be sprung together 
 somewhat to fit the cylinder bore. 
 
 In very large 
 motors the piston and exhaust 
 valve are also water-cooled. 
 
 Air-cooled motors, always 
 small in size, have projecting 
 metallic lugs, fins, or other 
 forms with which the air comes 
 in contact. Some device, such 
 as a fan, is generally used to 
 circulate the air against the 
 cooling parts, but sometimes 
 only the motion of the motor 
 through the atmosphere, as on 
 an automobile, is depended on 
 to bring fresh air in contact 
 with the cooling parts. Some- 
 times the cylinder is encased, 
 or air-jacketed, and a current 
 of air forced through the jacket 
 
 space. 
 
 Gas turbines have been constructed and tested in various 
 forms, but none has yet proved successful. The efficiencies 
 obtained have been extremely low. In some cases the motor, 
 of the steam turbine type, would not develop enough power 
 
THE GAS ENGINE 
 
 to drive the compressor for precompressing the air for com- 
 bustion. Pulverized coal for fuel has been tested among 
 others. 
 
 Combustion, as used in connection with internal-combustion 
 motors, means the chemical union of hydrogen, carbon, and 
 hydrocarbons of the fuel with the oxygen of the atmosphere, 
 except in specific cases where pure oxygen, unmixed with 
 any other chemical element, is taken as the supporter of 
 combustion. 
 
 The fuel is the mechanical mixture, chemical compound, or 
 element that combines more or less completely with the oxygen 
 during combustion. 
 
 There is a certain, although quite wide, limit to the propor- 
 tions of fuel and air in a mixture that can be ignited and burned 
 
 in an internal-combustion motor; 
 and there is a very limited range of 
 the proportions of air and fuel that 
 will give the maximum or nearly the 
 maximum amount of power from the 
 fuel and produce clean and complete 
 combustion. 
 
 A saturated mixture of air and fuel 
 cannot be burned in the cylinder of 
 a motor. Air is saturated with the 
 vapor of liquid fuel when it has 
 assimilated all that it can, which is 
 a definite amount. It is in a way 
 analogous to the dissolving of salt 
 in water. When the water has dis- 
 solved a certain amount, it becomes 
 saturated and will not dissolve, or 
 take into solution, any more of the salt. 
 
 Numerous methods of mixing the fuel with air and burning it 
 have been tried commercially with more or less success. In 
 some the mixture is made by bringing the fuel and air together, 
 without burning, just before they enter the cylinder and while on 
 their way to it. By this method there is never any dangerous 
 
 FIG. 4. 
 Valve and Closing Spring. 
 
TYPES OF MOTORS 5 
 
 amount of the combustible mixture on hand. In qther methods 
 the fuel is injected into the combustion chamber after the latter 
 is filled with air. In still others the mixture is made in quantity 
 outside the combustion space and then forced into it. In some 
 of the early types of motors the air-and-gas or air-and-vapor 
 mixture is drawn into the cylinder by suction and ignited at about 
 atmospheric pressure. It was found later that greater economy 
 of fuel and more power could be obtained from a given size of 
 cylinder by compressing the charge before igniting it. All 
 modern internal-combustion motors operate either by com- 
 pressing the charge of combustible mixture before ignition or by 
 compressing the air and then injecting the fuel, in this case 
 liquid, into the compressed air. 
 
 The cycle on which the internal-combustion motor operates 
 is the principal means of distinguishing one type from others. 
 Cycle, in this use, means the series of changes through which 
 each charge of combustible mixture passes from the time any 
 process of change of volume, pressure, or chemical action begins 
 on it until it passes, or is free to pass, out of the motor. The 
 cycle of a single-acting, single-cylinder motor such as described 
 above is not changed by the addition of cylinders that are dupli- 
 cates of the first in their action on the charge. Neither is the 
 cycle changed by making the motor double acting so that the 
 piston receives an impulse to drive it first in one direction and 
 then in the other, provided all the charges are acted on in the 
 same manner. 
 
 2. Beau de Rochas- or Otto-Cycle Motors. In motors 
 approaching the theoretical Otto cycle most closely a charge of 
 combustible mixture in the gaseous state and at a pressure some- 
 what less than atmospheric is taken into the cylinder, then 
 compressed into the combustion chamber by the instroke of the 
 piston and ignited at about the time the compression stroke is 
 completed. (Ignition may occur slightly before, at, or slightly 
 after the completion of the compression stroke.) Combustion 
 takes place at nearly constant volume, accompanied by increase 
 of temperature and pressure. The increased pressure forces 
 the piston out, and the temperature and pressure drop on account 
 
THE GAS ENGINE 
 
 FIG. 6. 
 
 Section through Combustion Chamber and Ports of Single-Cylinder, Four-Cycle, 
 Water-Cooled Gasoline Motor. Horizontal Stationary Type. 
 
 1. Cylinder bore. 
 
 2. Inlet valve. 
 
 3. End of lifting arm for inlet valve. 
 
 4. Closing spring for inlet valve. 
 
 5. Exhaust valve. 
 
 6. End of lifting arm for exhaust valve. 
 
 7. Closing spring for exhaust valve. 
 
 8. Priming valve with measuring cup for introducing gasoline into combustion 
 
 space for starting motor when very cold. 
 
 9. Compression relief valve located part way down barrel of cylinder. For 
 
 partially relieving compression when starting by hand, 
 lo. Movable portion of contact (low tension) igniter surrounded by graphite 
 
 bearing (not insulated), 
 it. Mixture passage. 
 12. Cooling- water space. 
 
TYPES OF MOTORS 7 
 
 of the expansion. An, exhaust port is opened just. before the 
 end of the stroke, and enough of the products of combustion 
 escape in the gaseous state to allow the pressure in the cylinder 
 to fall to or near atmospheric. This completes the cycle, although 
 there are some of the hot gases still remaining in the cylinder. 
 The remaining gases are useless in performing work, for they 
 exert no appreciable pressure to drive the piston on account of 
 having direct connection with the atmosphere. 
 
 The method of removing partly or completely the inert gas still 
 remaining in the cylinder, and of introducing another charge 
 of combustible mixture is not a part of the real cycle, but, since 
 some work is done on the charge before its introduction into the 
 cylinder, the removal of the products of combustion and the 
 introduction of a fresh charge must be considered as auxiliary 
 to the real cycle. The two usual methods of clearing out part of 
 the inert gases of combustion (they are seldom completely cleared 
 out) after they have fallen to atmospheric pressure, and intro- 
 ducing a new charge, have given to motors operating on the Otto 
 cycle the names by which they are commercially known. The 
 two types are designated as " four-cycle" and "two-cycle." 
 
 The "four-cycle" motor makes an exhaust stroke of the piston 
 to expel part of the gases remaining after the real cycle is com- 
 pleted, and then a suction stroke to draw in a new charge, thus 
 making four strokes in all from the beginning of one cycle to the 
 beginning of the one that succeeds it. 
 
 In the "two-cycle" motor the elements that make up the com- 
 bustible charge are compressed slightly, either together or sepa- 
 rately, before entering the motor cylinder, then allowed to enter 
 the cylinder and drive out most of the residual gases while the 
 piston is at and near the out position. The inlet and exhaust 
 ports are necessarily open simultaneously during this operation. 
 There are two strokes for each cycle. 
 
 The terms "two-cycle" and "four-cycle" are indefinite in 
 themselves, and also for the reason that they can be applied 
 respectively to any motor making either two or four strokes per 
 cycle. But by common usage they have a definite meaning in 
 reference to the Otto-cycle motor. 
 
THE GAS ENGINE 
 
TYPES OF MOTORS 
 
 FIG. 6. (See also Figs. 7 and 8.) 
 
 Four-Cylinder, Four-Cycle, Air-Cooled Automobile Motor. 
 
 The H. H. Franklin Manufacturing Company, Syracuse, N.Y. 
 
 1. Cylinder. 
 
 2. Piston. 
 
 3. Piston pin (or wrist pin). 
 
 4. Connecting red. 
 
 5. Crank shaft. 
 
 6. Crank case. 
 
 7. Inlet valve, hollow. 
 
 8. Exhaust valve, concentric with inlet valve. 
 
 9. Auxiliary exhaust valve, poppet type. 
 
 10. Cam for lifting auxiliary exhaust valve. 
 
 11. Cam follower for auxiliary exhaust valve. 
 
 12. Lifting rod for inlet valve. 
 
 13. Lifting rod for exhaust valve. 
 
 14. Cam for opening inlet valve. 
 
 15. Cam for opening exhaust valve. 
 
 16. Closing spring for inlet valve. 
 
 17. Closing spring for exhaust valve. 
 
 18. Adjusting screw for inlet valve. 
 
 19. Adjusting screw for exhaust valve. 
 
 20. Inlet pipe. 
 
 21. Exhaust pipe. 
 
 22. Auxiliary exhaust pipe. 
 
 23. Cooling flanges. 
 
 24. Timer. Only upper part shown. 
 
 25. Fan for cooling the cylinder. 
 
 26. Fly wheel. 
 
 27. Starting crank. 
 
 28. Oil reservoir for lubricating oil. 
 
10 
 
 THE GAS ENGINE 
 
 Gas- and Vapor-Burning Motors. 
 
 3. Four-Cycle Motors. Motors operating approximately on 
 the Otto or Beau de Rochas cycle and making four single strokes 
 of the piston for each cycle are commonly known as "four-cycle'' 
 
 30 31 
 
 FIG. 7. 
 
 (See also Figs. 6 and 8.) 
 Four-Cylinder, Four-Cycle, Air-Cooled Automobile Motor. 
 
 20. Inlet pipe. 25. Fan for cooling the cylinder. 
 
 21. Exhaust pipe. 29. Magneto. 
 
 22. Auxiliary exhaust pipe. 30. Rocker arm for inlet valve. 
 24. Timer. 31. Rocker arm for exhaust valve. 
 
 motors, as already stated. The four strokes of the piston corre- 
 spond to two revolutions of the crank shaft and flywheel in 
 motors resembling in general appearance the ordinary recipro- 
 cating steam engine. 
 
TYPES OF MOTORS 
 
 II 
 
 The four-cycle motor of the usual type has tw*o ports leading 
 into the combustion chamber; one through which the combus- 
 tible charge of mixed air and gas, or air and vapor, enters, and 
 the other through which the inert gases remaining after com- 
 bustion escape after expanding against the out-moving piston. 
 Both ports have valves to close them. When permanent gas 
 under pressure, as in gas mains for lighting, is used for fuel, a 
 fuel valve is frequently used to prevent the flow of gas into the 
 air passage or mixing chamber during the time the motor is 
 not taking in a charge. 
 
 19 
 
 FIG. 8. 
 
 (See also Figs. 6 and 7.) 
 Concentric Inlet and Exhaust Valves for Air-Cooled Automobile Motor. 
 
 i. Cylinder. 
 
 7. Inlet valve, hollow. 
 
 8. Exhaust valve, poppet type, con- 
 
 centric with 7. 
 
 12. Lifting rod for inlet valve. 
 
 13. Lifting rod for exhaust valve. 
 
 16. Closing spring for inlet valve. 
 
 17. Closing spring for exhaust valve. 
 
 18. Adjusting screw for inlet valve. 
 
 19. Adjusting screw for exhaust valve. 
 30. Rocker arm for inlet valve. 
 
 71. Rocker arm for exhaust valve. 
 
12 
 
 THE GAS ENGINE 
 
 FIG. 9. 
 
 Cross-Section of Motor Cylinder and Valve Chest, showing Valve-Lifting 
 
 Mechanism. 
 
 Valve. 
 
 Collar fastened to valve stem. 
 
 Cam shaft, lay shaft or half-speed shaft. 
 
 Lobe of cam. 
 
 Roller follower pressing against cam. 
 
 7 and lifted by cam 4 so as to open the valve i. 
 
 i. 
 
 2. 
 
 3- 
 4- 
 
 5- 
 
 6. Rocker arm pivoted at 
 
 7. Pivotal support for 6. 
 
 8. Cover for valve chest. 
 
 The low-tension ignition points (contact points) show just above the valve. 
 
 The intensity of compression is regulated by means of the valve chest cover 8. For 
 
 natural gas, gasoline, etc., the almost flat-bottomed cover shown in place is used. 
 
 But for higher compression, as for producer gas, or blast-furnace gas, a cover 
 
 with a projection for filling the space between the cover and port is used. See 
 
 Fig. 10. 
 
TYPES OF MOTORS 13 
 
 The action of the moving parts of the motor 'in conjunction 
 with the different steps of the heat cycle can be followed by 
 starting with any of the events that occur. It is convenient to 
 begin with the suction or charging stroke, which is not part of 
 the heat cycle. 
 
 First Stroke. Four-Cycle Motor. Charging, intake or suc- 
 tion. The piston, starting from its position nearest the com- 
 bustion chamber, draws in a charge by suction during the out- 
 stroke. The inlet valve either opens by suction automatically 
 against the resistance of a comparatively weak spring, or is 
 opened mechanically against a fairly strong spring. The inlet 
 valve closes at, or about, the completion of the suction stroke. 
 
 Second Stroke. Four-Cycle Motor. Compression. The 
 piston, returning during the instroke, compresses the charge into 
 the combustion chamber. Both the inlet and exhaust valves 
 remain closed during the compression stroke. 
 
 FIG. 10. 
 
 Covers for Valve Chest of Fig. 9. Covers are of different depths to give different 
 degrees of compression according to the fuel used. 
 
 The compressed charge is ignited just before, at, or very 
 slightly after the completion of the compression stroke. Ignition 
 is accomplished by an electric spark, electric arc, a flame, or a 
 hot piece of metal or other substance. 
 
 Third Stroke. Impulse Stroke. Completion of combustion, 
 expansion. Combustion, producing rise of both temperature 
 and pressure, is generally well under way by the time the piston 
 has made an appreciable part of the stroke following compression. 
 Combustion is completed and the increased pressure drives the 
 piston out, allowing expansion of the gases as the piston moves. 
 When the piston is well toward the completion of the impulse 
 stroke, the exhaust valve is mechanically opened against the 
 
THE GAS ENGINE 
 
 OH 
 
 I 
 
 I 
 
 a 1 
 
 Bfi 
 
 a 
 
 W 
 
 O 
 
TYPES OF MOTORS 15 
 
 pressure of the gases in the cylinder and of a stoyt spring. The 
 hot, inert gases partly escape by expansion. 
 
 Fourth Stroke. Four-Cycle Motor. Expulsion of inert gases. 
 The exhaust valve is kept open, and the piston, moving toward 
 the combustion chamber, expels part of the remaining gases. 
 The exhaust valve then closes at, or more generally slightly 
 after, the completion of the exhaust stroke. 
 
 In a single-acting, single-cylinder, four-cycle motor operating 
 on the Otto cycle and having the piston joined directly to the 
 crank by means of a connecting rod, the crank receives an impulse 
 only once in two revolutions. This necessitates a very heavy or 
 large-diameter fly wheel to secure reasonably steady running. 
 
 4. Auxiliary Exhaust Port. In a small proportion of four- 
 cycle motors, an auxiliary exhaust port is provided in the wall of 
 the cylinder where it is uncovered by the motion of the piston 
 just before the completion of the outstroke. When the auxiliary 
 port is thus uncovered just before the completion of the impulse 
 stroke, a considerable portion of the burned gases escapes through 
 it on account of their expansion. By opening the valve of the 
 customary exhaust port leading out from the combustion cham- 
 ber at the usual time, two exhaust passages for the escape of the 
 products of combustion are provided, and the release of the gases 
 can be made so rapid that there is practically no back pressure 
 remaining to resist the motion of the piston at the moment of 
 beginning its exhaust stroke. The auxiliary port is again covered 
 by the piston soon after the beginning of the exhaust stroke, and 
 the remaining inert gases are partly expelled by the motion of 
 the piston, the gases passing out through the port in the com- 
 bustion chamber. 
 
 The auxiliary exhaust port has a valve in some designs, but 
 none is used in others. The valve is sometimes of the automatic 
 check-valve type and is either a ball resting on its seat by its own 
 weight only, or a spring-closed valve similar to that used for an 
 automatic inlet. In other designs a mechanically operated valve 
 is used in the auxiliary exhaust port. 
 
 5. Atkinson Four-Cycle Motor. Some years ago Mr. Atkin- 
 son, in England, constructed a single-cylinder, single-acting, 
 
i6 
 
 THE GAS ENGINE 
 
TYPES OF MOTORS I/ 
 
 FIG. 12. (See also Fig. 13.) 
 
 Two-Cylinder, Four-Cycle, Single-Acting, Oil-Cooled Motor for Traction Engine. 
 
 45 brake horsepower. 
 
 Adapted to burn gasoline or cheap grade kerosene. Electric ignition. 
 Hart-Parr Company, Charles City, Iowa. 
 
 Section through axis of one cylinder. 
 
 Oil-jacketed cylinder. Cooling oil circulated by rotary pump. 
 
 Exhaust jets create upward blast of air through cooler by ejector action. Hori- 
 zontal pipe from relief (auxiliary) exhaust is hidden by exhaust pipe from 
 compression end of cylinder. 
 
 One cam operates both the inlet and the exhaust valve of one cylinder. Cylinder 
 barrel and breech cast in one piece. 
 
 Removable valve cages (with valve seats) ground to fit in cylinder casting. 
 
 During a five-hour continuous test of this motor under a nearly constant average 
 load of 61.98 brake (delivered) horsepower the temperature of the cooling 
 oil did not exceed 163 F., with a maximum atmospheric temperature of 
 
1 8 THE GAS ENGINE 
 
 four-cycle motor operating on the Otto cycle, in which the crank 
 made only one revolution for every four strokes of the piston. 
 This was accomplished by means of a somewhat complicated 
 system of links and other parts. The crank thus received an 
 impulse every revolution. The piston moved farther in toward 
 the combustion chamber on the exhaust stroke than on the com- 
 pression stroke, in order to more completely free the cylinder 
 from the inert gases of combustion. 
 
 FIG. 13. 
 
 (See also Fig. 12.) 
 
 Two-Cylinder, Four-Cycle, Oil-Cooled Motor for Traction Engine, Unmounted. 
 45 horsepower. Adapted to burn gasoline or cheap grade kerosene. Hart-Parr 
 Company, Charles City, Iowa. 
 
 The motor operated economically with regard to fuel con- 
 sumption, and had good speed regulation, but the lack of mechan- 
 ical balance of the moving parts was so serious a feature as to 
 prevent its commercial adoption to any great extent. 
 
TYPES OF MOTORS 19 
 
 6. " The Complete-Expansion Gas Engine. " Figs. 64%, to 
 71. This is made as a four-cycle, double-acting tandem engine. 
 It is the design of Mr. C. E. Sargent, and has several unique 
 features. 
 
 When operating at any load less than its full capacity, air only 
 is admitted during the early part of the charging stroke. Then 
 gas also is admitted at a time determined by the governor, and 
 continues entering until both air and gas are cut off before the 
 completion of the charging stroke. At full load gas begins to 
 enter at the same time as the air (at the beginning of the charging 
 stroke) and both are cut off at the same instant. The instant of 
 cutting off the mixture is invariable so far as automatic (governor) 
 regulation is concerned, and is timed to suit the kind of gas used. 
 The range of setting for the cut-off is from five-eighths to three- 
 quarters of the stroke. After cutting off, the charge expands 
 during the remainder of the charging stroke. The fixed point 
 of cut-off determines the extent of compression, which is constant 
 for all loads. Since producer gas can be compressed more with- 
 out self-ignition than natural gas, the point of cut-off is set later 
 for the former than for the latter. The heat value of the producer 
 gas mixture is less than that of the natural gas, and this allows a 
 higher compression without causing a higher terminal pressure 
 at the end of the impulse (expansion) stroke. On account of 
 cutting off the charge before the completion of the charging 
 stroke, expansion is carried out further during the impulse stroke 
 than in motors which admit the charge (air and mixture) during 
 the entire intake stroke. The pressure at the time of opening 
 the exhaust valve is well down toward atmospheric, hence the 
 name "Complete-Expansion Gas Engine." 
 
 The cylinder volume is about twenty-five per cent greater than 
 in the usual types of four-cycle motors of the same power, but it 
 is claimed that the greater cost of construction on this account is 
 more than balanced by the gain in economy on account of the 
 more complete expansion. 
 
 Another feature of the engine is that there is only one port into 
 each combustion chamber, which is unusual for either four-cycle 
 or two-cycle motors. The charge enters and the burned gases 
 
20 THE GAS ENGINE 
 
 escape through the same cylinder port. There is a small port 
 with a by-pass valve for balancing the pressure on the poppet 
 valve that closes the cylinder port, but its function does not 
 include allowing the burned gases to escape. The by-pass valve 
 is opened by cam action just before the exhaust is to take 
 place. 
 
 On account of the extent to which the expansion is carried out, 
 the burned gases are so cool at the time the exhaust valve opens 
 that it is not necessary to water-cool the valve as in the usual 
 types of large gas engines. The builders of the engine make 
 the following statement regarding the temperatures of the burned 
 gases: 
 
 " Aside from the greater economy of an engine which expands 
 the charge to practically atmospheric pressure, the average tem- 
 perature during the cycle is less and the engine is not subjected 
 to the internal strains indigenous to the higher temperatures, 
 for example, the initial temperature in both types is about 3000 F., 
 the terminal temperature in the ordinary engine is 1800 F., and 
 in the complete-expansion engine 500 F., making the average 
 temperature of the working stroke of the former 2400 F. and in 
 the complete-expansion engine 1750 F." 
 
 The theoretical cycle which this motor approximates is shown 
 in Fig. 135. 
 
 7. The Nuremberg motor in large sizes, and the Gobron- 
 Brillie motor in small sizes for automobile and similar uses, both 
 four-cycle, use an open-end cylinder, dispensing with cylinder 
 heads. There are two pistons to one cylinder. The pistons are 
 both connected to the same crank shaft so as to approach and 
 recede from each other and the middle of the cylinder simul- 
 taneously. The one next the crank shaft has a connecting rod 
 of the usual length and form. The rear piston has a crosshead 
 at the end of the cylinder farthest from the crank shaft, and the 
 crosshead is connected to the crank shaft by two connecting rods, 
 one on each side of the cylinder (or cylinders). The cranks for 
 the two pistons of one cylinder are at 180 degrees with each other, 
 or, expressed otherwise, directly opposite each other. The ports 
 are several small openings arranged circumferentially around 
 
TYPES OF MOTORS 
 
 21 
 
 the middle of the cylinder. The inlet and exhaust through these 
 ports are controlled by valves in the usual manner. 
 
 This construction removes what is sometimes a source of 
 serious trouble in large gas engines, that is, the fracture of the 
 cylinder heads by heating and unequal expansion. There are 
 no glands or stuffing boxes required for piston rods. 
 
 FIG. 14. 
 
 Open-End Cylinder Motor. Longitudinal sections at right angles to each other. 
 
 Four-cycle. Two cylinders. Two pistons in each cylinder. Inlet and exhaust 
 
 ports at middle of cylinder. 
 The two pistons in each cylinder approach each other during compression, and 
 
 recede from each other during the impulse or expansion stroke. One impulse 
 
 every revolution in the two-cylinder motor. 
 
 8. Two-Cycle Motors. This name is generally applied to 
 motors operating on the Otto cycle, and in which each piston 
 makes only two strokes for each impulse it receives in a single- 
 acting motor. 
 
 The two-cycle motor, in its simplest and most usual form, has 
 its inlet and exhaust ports in the walls of the cylinder bore near 
 the end farthest from the combustion chamber. Its action can 
 
22 THE GAS ENGINE 
 
 be followed by starting with the piston in its position nearest the 
 combustion chamber, and a compressed charge in the latter. 
 
 First Stroke. Two-Cycle Motor. The compressed charge 
 is ignited and burned, and the consequent increased pressure 
 drives the piston outward as the charge expands. At the 
 beginning of the outstroke the enclosed crank case is full of 
 combustible mixture previously drawn in. The outstroke com- 
 presses this to some extent. When the piston is well toward the 
 completion of the outstroke, it uncovers a row of small exhaust 
 port-holes that pierce the cylinder walls and extend somewhat 
 less than half way around it circumferentially. This allows part 
 of the products of combustion to escape by expansion. The 
 piston, continuing its outstroke, next uncovers a similar row of 
 inlet port -holes that connect to the crank case. This allows a 
 charge of the slightly compressed combustible mixture in the 
 crank case to flow into the cylinder and drive out most of the 
 remaining inert gases. 
 
 Second Stroke. Two-Cycle Motor. The piston, now returning 
 toward the combustion chamber, covers first the inlet port-holes, 
 then the exhaust port-holes, and then compresses the charge till 
 the end of the instroke is reached. During the instroke the 
 piston also draws more mixture into the crank case by suction. 
 
 The mixture enters the crank case generally either through an 
 automatic poppet valve in or near its walls or through a port in 
 the bore of the cylinder that is uncovered when the piston has 
 nearly completed its compression stroke (instroke). The latter 
 port connects the crank case to the source of fuel and air supply. 
 A motor constructed in the latter manner has no valves, and need 
 have no moving parts but the piston, connecting rod, crank shaft, 
 and the parts rigidly connected to them. This does not include 
 the ignition system. This great simplicity makes this style of 
 motor at once attractive on account of small cost of construction 
 and absence of numerous parts to wear and get out of repair. 
 There are certain features of its operation, however, that have 
 prevented its adoption to as great an extent as the four-cycle 
 motor. While it seems at first thought that the power developed 
 per pound of weight of motor should be much more in the two- 
 
TYPES OF MOTORS 
 
 FIGS. 15 AND 16. 
 Two-Cycle, Valveless, Three-Port Motor. 
 
 Longitudinal sections. 
 
 6. Exhaust port. 
 
 7. Baffle plate. 
 
 Fine-mesh wire screen to prevent 
 
 back firing into the crank case. 
 Spark plug. 
 
 8. 
 
 Cylinder. 
 Piston. 
 Crank case. 
 Inlet to crank case. 
 5. Passage from crank case to inlet port 
 
 of combustion chamber. 
 
 In Fig. 1 6 the piston has just completed the compression stroke (upstroke in this 
 case) and uncovered the inlet port 4 to the crank case and mixture is flowing into 
 the latter on account of the partial vacuum created in it by the upward movement 
 of the piston. 
 
 Fig. 15 shows the piston after the charge has been burned and the piston moved 
 down to the lower end of its stroke. The burned gases are passing out through 
 the exhaust port 6 and the compressed mixture in the crank case is flowing into 
 the combustion space. The baffle plate 7 deflects the entering charge upward 
 so that it does not pass out of the exhaust port. 
 
24 THE GAS ENGINE 
 
 cycle than in the four-cycle motor, each, in fact, develops about 
 the same amount of power per pound of weight. 
 
 When a two-cycle motor of the simple single-acting form just 
 mentioned is changed to double-acting (with both ends of the 
 cylinder closed as in most steam engines, and a combustion 
 chamber at each end of the cylinder) it becomes impossible to 
 initially compress in the crank case all the combustible mixture 
 in order to force it into the combustion cylinder. The double- 
 acting two-cycle motor therefore requires an additional cylinder 
 for the initial compression of the charge. Numerous designs of 
 double-acting two-cycle motors have been operated. In some 
 the fuel and air are mixed on their way to the compression 
 cylinder, as in the case of the single-acting motor, while in others 
 the air is compressed in one auxiliary compression cylinder, and 
 the gas, or a mixture of fuel vapor and air, too rich in combustible 
 matter to burn, is compressed in another auxiliary cylinder, and 
 the contents of the two auxiliary cylinders are mixed as they pass 
 into the combustion cylinder. By this means there is no appre- 
 ciable amount of combustible mixture ever on hand outside of 
 the combustion cylinder. The liability to dangerous explosions 
 outside of the combustion cylinder, which must be carefully 
 considered for large motors, is thus eliminated. 
 
 9. The Koerting Two-Cycle Motor is of the double-acting type, 
 with separate auxiliary compression cylinders for air and gas. 
 Large motors of this type have been put into practical operation 
 extensively both in this country and Europe. Many of them 
 have been designed especially for using blast-furnace gas. 
 
 The Koerting motors, double-acting, are constructed with an 
 inlet port leading into each combustion chamber and an exhaust 
 port composed of a great number of small holes that pierce the 
 cylinder wall circumferentially at the middle. The piston has a 
 length but slightly less than that of the stroke. It covers the 
 exhaust port except when near the end of its stroke in either 
 direction. The same port is thus used for exhausting alternately 
 from both ends of the cylinder. After the exhaust port has been 
 uncovered and the inert gases have escaped till the pressure in 
 the combustion cylinder has fallen to about that of the atmos- 
 
TYPES OF MOTORS 
 
 FIG. 17. 
 
 Koerting Two-Cycle, Double-Acting Gas Engine. 
 Diagram showing the arrangement of parts. 
 
 1. Combustion cylinder. 
 
 2. Piston, drum type. 
 
 3. Gas pump. Piston at left end. 
 
 4. Air pump.' Piston at left end. 
 
 5. Air duct to inlet valve. 
 
 6. Gas duct to inlet valve. 
 
 7. Inlet valve. 
 
 8. Exhaust passage connecting to several small ports around the middle of the 
 
 cylinder. 
 
 9. Air valve at pump. 
 10. Gas valve at pump. 
 
 The opening and closing of the inlet valves 7 do not vary either in time or extent. 
 One of the inlet valves opens after the piston has moved away from it and 
 uncovered the exhaust ports. The time and stroke of the air-pump piston and 
 gas-pump piston do not vary. When the inlet valve of the combustion chamber 
 opens, air, which has been compressed by the air pump, flows into the combus- 
 tion cylinder. The piston of the air pump continues its compression stroke 
 during this time. The governor controls the time at which gas, compressed by 
 the gas pump, begins to flow into the combustion cylinder with the air. The 
 gas and air mixture then continues to flow in till the inlet valve closes. The motor 
 piston 2 is near the exhaust end of its stroke during the intake of charge. The 
 process is then repeated for the opposite end of the combustion cylinder. The 
 piston receives an impulse each stroke. 
 
26 THE GAS ENGINE 
 
 phere, the air inlet port is opened and air rushes in to scavenger 
 the cylinder by driving out the remaining inert gases. If any of 
 the air passes out of the exhaust port, there is no loss of fuel such 
 as occurs if too much combustible mixture is brought in as in 
 other types of two-cycle motors. After part of the compressed 
 
 PLAN 
 
 ELEVATION 
 FIG. 18. 
 
 Koerting Two-Cycle, Double-Acting Gas Engine. Single cylinder. Plan and 
 
 elevation. Made in units (single-cylinder) from 400 to 1500 horsepower. 
 
 i. Motor cylinder. 3. Gas-pump cylinder. 
 
 4. Air-pump cylinder. 
 
 The overhanging crank on the side opposite the flywheel is f<?r driving the air pump 
 and gas pump. The main connecting rod (for the motor piston) is not shown. 
 
 air has passed from the auxiliary cylinder into the combustion 
 cylinder, the fuel inlet valve is opened, and the gas and remaining 
 air mix as they pass into the combustion cylinder. Special forms 
 
TYPES OF MOTORS 27 
 
 of port openings are adopted to cause the mixture^to enter in such 
 a way as to remain in and near the compression space, while the 
 air that is not mixed with the fuel, but still remains in the com- 
 bustion cylinder, stays next to the piston head. This stratifica- 
 tion of the contents of the combustion cylinder is thought to give 
 better economic results than other methods, and allows the use 
 of very lean (low in capacity to produce heat) fuel, while, at the 
 same time, the speed can be controlled by regulating the amount 
 of fuel that enters for any stroke. 
 
 10. Brayton Motor and Cycle. This cycle was invented by 
 Mr. Brayton of Philadelphia, and a motor operating on it was 
 constructed in 1873. The air and fuel were compressed by 
 auxiliary compressors and delivered into separate tanks at a 
 pressure somewhat greater than that of the maximum in the 
 combustion cylinder. They were then allowed to flow toward 
 the combustion cylinder and mix together just before entering it. 
 The mixture then passed through a fine-mesh wire screen that 
 guarded the port, and burned immediately after passing through 
 the screen. The latter was to prevent the flame from backfiring 
 into the port. The mixture was admitted to the combus- 
 tion cylinder just as the piston was ready to start on the out- 
 stroke, and burned at a uniform pressure, practically the same 
 as that in the tanks. The piston was forced out by the pressure, 
 and the mixture was admitted during one-third of its stroke, more 
 or less, and then the inlet valve closed and the highly heated 
 contents of the cylinder expanded to drive the piston out to nearly 
 the end of the stroke, when the exhaust valve opened and allowed 
 them to escape till the pressure fell to about atmospheric. On 
 the return stroke the residual gases in the combustion cylinder 
 were compressed by the piston to nearly the same pressure as that 
 of the fuel and air tanks. A small by-pass at the inlet valve 
 allowed enough mixture to enter the combustion cylinder to keep 
 a small pilot flame going constantly at the wire screen. This 
 flame ignited the charge as soon as it began to enter the cylinder. 
 
 The cycle of the gases in the Brayton motor is accomplished 
 partly in the air and fuel compression cylinders, and the remainder 
 in the combustion cylinder. 
 
28 THE GAS ENGINE 
 
 Theoretically the Brayton cycle is of such a nature as to 
 deserve careful consideration with a view to its commercial 
 application. The chief difficulties that the inventor states he 
 met in the motors constructed to operate on it were with the wire 
 gauze screen and other devices used to prevent back firing, and 
 from the extinguishing of the pilot flame and consequent stoppage 
 of the motor. Many devices in addition to the wire gauze were 
 tried without entire success in any case. The addition of air and 
 gas compressors may seem a serious objection to this motor in 
 comparison with the simpler ones for operating on the Otto cycle. 
 Yet it is to be remembered that the larger Otto-cycle, two-cycle 
 motors (Koerting motors) have auxiliary compressors for the air 
 and the fuel. The absence of high pressures of explosion in the 
 Brayton motor is well worthy of consideration, especially for 
 very large motors. A central compressor plant for supplying 
 compressed air and fuel to several motors would simplify the 
 equipment of a power plant. 
 
 Oil-Burning Motors. 
 
 n. In the motors that have been discussed the combustible 
 charge enters the cylinder either in the form of a mixture of gas 
 and air or of vapor and air. There is another class of internal- 
 combustion motors, in less general, but extensive, use, whose 
 fuel is injected into the cylinder, combustion chamber, or an 
 extension of the latter, in liquid form. Kerosene and other of 
 the less volatile distillates of petroleum are used, and, in one 
 or two designs, even the crude petroleum itself is used for fuel. 
 The high cost of kerosene in comparison with the heavier or 
 less refined oils is the chief objection to its use in large motors. 
 
 12. The Hornsby-Akroyd Oil Motor has a somewhat jug- 
 shaped hollow metal vaporizer attached by the neck end to the 
 end of the combustion cylinder so as to form an extension of the 
 latter. The cylinder otherwise resembles that of an ordinary 
 four-cycle, single-acting, Otto-cycle motor. The vaporizer 
 space and cylinder space are joined only by the comparatively 
 small opening of the neck connection. Inlet and exhaust ports 
 
TYPES OF MOTORS 
 
 29 
 
 connect with the combustion chamber. The liquid fuel is 
 injected into the vaporizer through one or more minute nozzles 
 so that it enters as a spray. 
 
 The vaporizer, usually of cast iron, is kept at a dull-red heat. 
 Before starting the motor, the vaporizer is heated by an external 
 flame, but after the motor is running, the heat of combustion 
 inside the cylinder and vaporizer keeps the latter hot enough. 
 
 Cooling Water 
 Outlet 
 
 FIG. 19. (See also Figs. 20, 21, 22, 23, 24, 72.) 
 
 Hornsby-Akroyd Four-Cycle, Single-Acting Engine for Kerosene and Distillates. 
 De La Vergne Machine Company, New York, N.Y. Longitudinal section 
 through cylinder. 
 
 Oil is injected into the internally ribbed vaporizer during the suction stroke and 
 vaporized by the heat of the vaporizer. The compression stroke forces the air 
 into the vaporizer and the mixture is ignited at about the completion of the com- 
 pression stroke by the heat of the vaporizer. 
 
 The amount of fuel oil injected is controlled by a governor acting on a by-pass 
 valve connected to the outlet passage of a plunger pump. 
 
30 THE GAS ENGINE 
 
 The operation is almost exactly the same as that of a four- 
 cycle, Otto-cycle gas or vapor motor. Taken step by step, it is, 
 dealing with the strokes of the piston : 
 
 First Stroke. Charging, intake or suction. The piston, 
 starting from its position nearest the combustion chamber, draws 
 
 FIG. 20. 
 Transverse Section of Hornsby-Akroyd Oil Engine. 
 
 The fuel-oil pump is shown at the bottom of the figure, and the governor at the 
 right-hand upper part. 
 
 in air to an amount practically equal to the volume of displace- 
 ment of the piston during its outstroke. Oil is forced into the 
 vaporizer during all or part of the outstroke, and vaporized 
 
TYPES OF MOTORS 31 
 
 more or less completely. The air inlet valve opens at about the 
 time of beginning the stroke, and closes at or about the end of 
 the stroke. 
 
 FIG. 21. 
 
 Injector Nozzle Used on Hornsby-Akroyd Oil Engine. 
 
 The oil enters through the pipe at the left end, passes through the ball check valve 
 and around the helical grooves in the pin or plug at the right end, where it escapes 
 into the vaporizer. 
 
 Second Stroke. Compression and completion of vaporization. 
 The piston, returning on the instroke to its first position, com- 
 presses the air and oil vapor. If any of the oil remains unvapor- 
 ized at the beginning of this stroke, its vaporization is completed 
 during the early part of compression. The compression of the 
 
 Water Outlet 
 
 FIG. 22. 
 
 Air Inlet and Exhaust Valves of Hornsby-Akroyd Oil Motor. 
 Both valves are mechanically operated. 
 
 air forces part of it in through the narrow neck into the vaporizer 
 and mixes it with the vaporized fuel. The air is heated by the 
 compression and by heat received from the hot parts of the motor. 
 The heat of the vaporizer, together with that of compression, 
 causes the mixture to ignite at about the time of completion of 
 
FIG. 23. 
 
 Oil-injecting System of Hornsby-Akroyd Oil Engine. The pump discharge is con- 
 nected to both the injector nozzle in the vaporizer and the regulator. 
 
 (32) 
 
 FIG. 24. 
 Full Side View of Cylinder End of Hornsby-Akroyd Oil Engine. 
 
TYPES OF MOTORS 
 
 33 
 
 the compression stroke. The inlet and exhaust, ports are both 
 closed during most or all of the compression stroke. 
 
 Third Stroke. Impulse stroke. Completion of combustion. 
 Expansion. Opening of exhaust port. Combustion, accom- 
 panied by rise of both temperature and pressure, is generally 
 well established at the beginning of the impulse stroke. It is 
 completed during the early part of the impulse stroke, and the 
 increased pressure drives the piston outward, allowing the gases 
 to expand as the piston moves. When the piston has nearly 
 reached the end of the impulse stroke, the exhaust valve is opened 
 against the resistance of the gas pressure and a stout spring. The 
 contents of the cylinder partly escape by expansion. 
 
 Cock 
 
 Gas Reservoir. 
 
 Flexible 
 
 Rubber 
 
 Diaphragm 
 
 FIG. 25. 
 
 Gas Connections for Using Gas from Small Mains or through a Small Connecting 
 Pipe. The gas reservoir fills between the suction or charging strokes of the 
 piston, so that the flexible diaphragm is distended as shown. The suction stroke 
 takes gas from the reservoir, so that the diaphragm is drawn in. A rubber bag 
 is often used instead of the type of reservoir shown. 
 
 Fourth Stroke. Expulsion of inert gases. The exhaust valve 
 is kept open, and the piston, moving in toward the combustion 
 chamber and vaporizer, expels a portion of the residual gases. 
 
34 THE GAS ENGINE 
 
 The exhaust valve is closed at, or slightly after, the end of the 
 exhaust stroke. This completes the series of events. 
 
 In order that ignition shall occur at the proper instant in 
 carrying out the cycle in the Hornsby-Akroyd motor, it is necessary 
 to have the intensity of the compression made suitable to the 
 purpose. Too high compression causes ignition too long before 
 the completion of the compression stroke, and too low com- 
 pression will not cause ignition soon enough, or, if very low, not at 
 all. The usual method of adjusting the compression is by vary- 
 ing the effective length of the connecting rod so as to cause the 
 piston to pass further, or not so far, as the case may be, into the 
 combustion space end cf the cylinder. Ordinarily this is. done 
 in preliminary trials before putting the motor into permanent 
 service. The length of the connecting rod is fixed and a trial 
 made to determine when ignition occurs and also the efficiency 
 of the motor. If found unsatisfactory, the length of the con- 
 necting rod is changed and fixed at another length and another 
 trial made, and so on. 
 
 The necessity of adjusting the length of the connecting rod 
 for each motor arises from the fact that, since the vaporizer and 
 cylinder are usually of cast metal, there is a variation in the size 
 of those made from the same patterns; and similarly, in large 
 motors, in other cast parts, as the piston and frame. In addition 
 to this there may be other causes necessitating a slight difference 
 in the compression pressures of two practically similar and equal 
 size motors made from the same patterns. A slight difference 
 in the form or composition of the metal in the two vaporizers or 
 two motors made from the same patterns may make it necessary 
 for one to have higher compression pressure than the other in 
 order to produce ignition at the proper time. The compression 
 also has to be regulated to suit the fuel used. 
 
 The compression of the air is carried to about the same pressure 
 for this motor as is used in gasoline and naphtha motors with 
 electric spark or arc ignition. 
 
 13. Oil-Burning Motor with Bulb Ignition. In this moW a 
 comparatively small hollow bulb of metal is attached to the 
 closed end of the cylinder, and the space in the bulb is connected 
 
FIG. 26. 
 
 i 
 
 Mietz & Weiss Oil Engine. For kerosene oil and distillates, 
 acting. 2^ to 75 horsepower per cylinder. 
 
 Two-cycle, single- 
 
 1. Combustion space of cylinder. 
 
 2. Piston. 
 
 3. Air port into crank case. 
 
 4. Air passage from crank case into 
 
 combustion chamber. 
 
 5. Inlet port for air into combustion 
 
 chamber. 
 
 6. Fuel-oil tank. 
 
 7. Oil pipe to plunger pump for injecting 
 
 oil into the combustion chamber. 
 
 8. Pump for forcing oil into combustion 
 
 chamber. 
 
 9. Pump plunger. 
 
 10. Oil pipe to injecting nozzle. 
 
 11. Nozzle for injecting fuel oil into com- 
 
 12. Baffle plate opposite oil nozzle. 
 
 13. Hot bulb for ignition, cast iron. 
 
 14. Exhaust port. 
 
 15. Water in lower part of jacket for 
 
 cooling cylinder. 
 
 1 6. Steam in upper part of jacket space. 
 
 17. Steam dome. 
 
 1 8. Steam pipe from steam dome to air 
 
 inlet port 5. 
 
 19. Oscillating arm for forcing in the 
 
 pump plunger at each revolution 
 of the crank shaft. 
 
 20. Coil spring for forcing pump 
 
 plunger outward. 
 
 21. Torch for heating the bulb 13 when 
 
 starting cold. 
 
 bustion chamber. 
 
 The amount of fuel oil forced into the combustion chamber during each compres- 
 sion stroke of the piston is regulated by a governor (not shown). The governor 
 varies the movement of the arm 19 toward the pump plunger 9 so as to give the 
 plunger less motion when the speed of the motor increases. The amount of oil 
 injected is thus reduce^ as speed increases. It is not necessary to time the 
 injection of oil with any great accuracy. 
 
 The cooling water does not flow through and out of the jacket space, but is vapor- 
 ized in it and the steam carried into the combustion chamber along with the air. 
 
 See Fig. 27 for constant-level water tank that is attached to the side of the motor 
 cylinder and connected to the jacket space. 
 
 (35) 
 
THE GAS ENGINE 
 
 to the combustion chamber by a short, small duct. The cylinder 
 resembles that of an ordinary four-stroke, Otto-cycle motor, as do 
 the other principal parts. The heat cycle is nearly the same as 
 that of the usual types of gasoline and naphtha motors operating 
 on the Otto cycle and making four strokes of the piston per cycle. 
 The inlet and exhaust ports open into the combustion chamber. 
 
 -Water to Jacket Space of Motor 
 Cylinder 
 
 (Tater from City Mains or Overhead 
 Supply Tank 
 
 FIG. 27. 
 
 Constant-Level Water Tank for Mietz & Weiss Horizontal Oil Engine. This 
 tank is connected to the side of the motor cylinder and communicates with the 
 water-jacket space. The level of the water in the jacket space is the same as in 
 the tank. 
 
 1. Connection to lower part of jacket space of motor cylinder. 
 
 2. Connection to upper part of jacket space above water level. 
 
 3. Float. 
 
 4. Valve. 
 
 The bulbous extension attached to the cylinder head must be 
 heated by an external flame before starting the motor. When 
 operating, the bulb, generally of cast iron, is kept at a full red 
 heat. The liquid fuel is injected into the combustion chamber 
 of the cylinder at about the time that the compression stroke is 
 completed. The nozzle from which the oil is ejected is placed 
 in the side of the combustion chamber, and points so that the jet 
 of oil projected into the cylinder strikes a deflector plate extend- 
 ing out from the inner end of the piston, and part of it is deflected 
 into the hot bulb, there mixing with the air forced into the latter 
 during the compression stroke, vaporizing and igniting. 
 
TYPES OF MOTORS 37 
 
 The steps of the operation, starting with the suction stroke, are: 
 
 First Stroke. Suction. The outstroke of the piston draws 
 in a cylinderful of air through the open inlet valve. 
 
 Second Stroke. Compression. The inlet valve closes and the 
 air is compressed by the instroke of the piston. Oil is injected 
 just before, at, or very slightly after the completion of the com- 
 pression stroke. The oil is vaporized and ignited by the heat of 
 compression and of the hot parts of the motor, especially the hot 
 bulb. 
 
 Third Stroke. Impulse Stroke. Combustion and expansion 
 against the piston are completed and the exhaust port opened 
 to allow the inert gases to escape. 
 
 Fourth Stroke. Most of the remaining inert gas is expelled 
 by the instroke of the piston. 
 
 The compression of the air in this motor is about to the same 
 intensity as for gas and gasoline motors equipped with electric 
 spark or arc ignition apparatus. 
 
 14. Diesel Oil Motor. This motor, the invention of Herr 
 Rudolph Diesel, operates at a compression pressure of about 
 500 pounds per square inch, which is vastly higher than that 
 used in any other internal-combustion motor, and utilizes the 
 high temperature produced by compression to ignite the charge. 
 It differs radically from other motors in these two characteristics 
 of high pressure and of ignition. 
 
 In its operation a cylinderful of air is compressed by the in- 
 stroke of the piston into a very small space that corresponds to 
 the combustion chamber in an Otto-cycle motor. An oil inlet 
 valve is then opened and oil is blown in by compressed air taken 
 from tanks separate from the motor. The air pressure of the 
 tanks is, of course, higher than that in the combustion cylinder. 
 The first particles of oil are ignited and burned as soon as they 
 enter the hot compressed air in the combustion cylinder, and so 
 on with all the oil that follows. The burning is somewhat 
 gradual, as compared with the explosion in other motors, since 
 the oil is blown in slowly in comparison with the speed of the 
 piston. The pressure is therefore not increased much, if any, 
 above that of compression, but is kept up as the piston recedes, 
 
38 THE GAS ENGINE 
 
 by the constant influx of fuel, until the oil inlet valve closes. The 
 hot gases in the cylinder then continue to expand and drive out 
 the piston until the exhaust port is opened. The cylinder is 
 partly cleared of inert gases during the next stroke of the piston, 
 and fresh air is drawn in by suction during the following stroke. 
 Crude petroleum can be used for fuel. 
 
 The fuel is blown in through an atomizer of unusual construc- 
 tion which is made up of broad rings resembling washers, with 
 grooved faces and small perforations. The rings are placed side 
 by side on the oil-valve stem in sufficient number to form a column 
 several times as long as their diameter. The compressed air 
 from the auxiliary tanks passes through the nest of disks and 
 becomes thoroughly impregnated with the oil, thus securing the 
 best mechanical condition for rapid combustion. 
 
 On account of the extremely high compression pressure and 
 the comparatively large size of the Diesel motors that have been 
 put into operation, they cannot be conveniently started by hand 
 power. Compressed air from a storage tank is used for starting. 
 The motor is barred over by hand till the piston is just beginning 
 the outstroke with the valves closed as for the impulse stroke. 
 A hand valve from the compressed-air starting tank is then 
 opened and the high pressure enters the cylinder and drives the 
 piston outward. The motor starts quickly under the high 
 pressure and the hand valve must be promptly closed. 
 
 The auxiliary air tanks are filled by a separately driven air 
 compressor. These tanks are charged by means of power from 
 the motor while it is running. 
 
 The speed of the motor is controlled by the action of a centrif- 
 ugal governor that regulates the quantity of oil fuel forced into 
 the nest of atomizing washers or disks, from which it is carried 
 into the cylinder by the compressed air. The regulating devices 
 that are used operate in various ways, generally on a pump, each 
 stroke of which forces a charge of oil into the cylinder by varying 
 the length of stroke of the pump, the extent of the opening of an 
 oil by-pass valve, etc. The fuel valve closes early in the stroke, 
 and the pressure in the combustion cylinder drops -well toward 
 atmospheric by the time the exhaust valve opens. 
 
TYPES OF MOTORS 39 
 
 On account of the high compression and great expansion, the 
 combustion cylinder (combustion chamber and cylinder together) 
 and the stroke of the piston are longer, in comparison with their 
 diameters, than is customary in other internal-combustion motors 
 and in steam engines. This is on account of constructive prin- 
 ciples, and is not otherwise necessary to secure the high com- 
 pression and great expansion. 
 
 Pioneer Internal-Combustion Motors. 
 
 15. The earliest gas engine commercially used (still shown as 
 a historical exhibit) has a vertical cylinder open at the top and 
 with the inlet and exhaust ports at the bottom. The piston is 
 connected to a horizontal shaft placed above the cylinder and 
 carrying a flywheel. The connection between the piston and 
 shaft is by means of a spur gear wheel on the shaft and a toothed 
 rack on the piston, instead of the now customary smooth piston 
 rod. The gear is connected to the shaft by a pawl and ratchet, 
 so that it is free to turn around the shaft in one direction but 
 not in the other. The piston is therefore free to move upward 
 when a charge is exploded under it, but when descending it 
 drives the shaft by means of the gear wheel and ratchet. The 
 descent of the piston is due to its own weight only, unless the 
 speed is very slow. Then the cooling and contraction of the gas 
 after combustion may produce a partial vacuum. 
 
 In the operation of this free-piston motor the piston is lifted 
 through part of its stroke from its lowest position by means of a 
 connection, for this purpose, with the rotating flywheel shaft. 
 The combustible charge is drawn in by suction during this early 
 part of the piston's upward motion. When the piston has reached 
 a certain height the charge is ignited at about atmospheric 
 pressure, and the explosion projects the piston farther upward 
 at a higher velocity than it had been traveling. It moves upward 
 freely until stopped by gravity and friction, then descends by 
 gravity and drags the flywheel shaft around, at the same time 
 expelling the inert products of combustion through the exhaust 
 port, which opens when the piston begins to descend. This 
 
40 THE GAS ENGINE 
 
 is the cycle that is repeatedly performed while the motor is 
 running. 
 
 Motors operating on the same cycle (heat cycle of the gases) 
 as the free-piston motor just described, but having a cranked 
 flywheel shaft and a fixed-length connecting rod between the 
 piston and crank shaft, were constructed soon after the free- 
 piston motor. 
 
 In comparison with motors in which the combustible charge 
 is compressed before ignition, and which were brought out after 
 the ones just mentioned, the free-piston motor and all other 
 internal-combustion motors in which the charge is not com- 
 pressed before ignition, are inefficient in transforming the heat of 
 combustion into mechanical energy. They are uneconomical of 
 fuel and heavy in weight in proportion to their power capacity. 
 When motors operating on the Beau de Rochas or Otto cycle 
 appeared, the earlier non-compressing types were discarded from 
 commercial power generation use. 
 
 Scavenging. 
 
 1 6. In four-cycle motors following the Otto cycle approximately 
 there is a considerable volume of the gaseous products of combus- 
 tion left in the motor cylinder after the exhaust stroke of the 
 piston is completed, unless some special provision is made for 
 removing them. These inert residual gases mingle with the 
 next charge that enters and dilute it. While this dilution affects 
 the economy of the motor but little, if any, it reduces the power 
 capacity by preventing a complete cylinderful of the combustible 
 mixture from entering. 
 
 Some experiments were made in England on a small four- 
 cycle motor to find what increase of power could be secured by 
 removing the residual gaseous products of combustion before 
 taking in a fresh charge. The method of scavenging the cylinder 
 with pure air was very simple. A long, straight exhaust pipe was 
 connected to the motor. The length of the exhaust pipe was so 
 proportioned by experimentation that the inertia of the gases 
 passing out rapidly when the exhaust valve opened, induced a 
 
TYPES OF MOTORS 41 
 
 partial vacuum at the motor end of the pipe at fche instant of 
 opening the inlet valve. When the inlet opened, the suction due 
 to the inertia of the escaping portion of the exhaust gases drew 
 the remaining portion out of the cylinder and fresh air into it. 
 The fuel-gas valve was not opened till some air had passed into 
 the motor cylinder. Some gain in the power capacity of the 
 motor was thus secured. 
 
 The Atkinson four-cycle motor, already mentioned, can be 
 classed as a scavenging motor, since its piston goes so far into the 
 compression space on the exhaust stroke as to drive out nearly 
 all of the inert gases. 
 
 Two-cycle motors that have air and gas compressors are 
 scavenging motors when enough air is let in to drive out nearly 
 all the products of combustion before the combustible mixture 
 of air and gas is passed into the cylinder. The more simple form 
 of two-cycle motor that precompresses the combustible mixture 
 in the crank case can hardly be classed as a scavenging motor. 
 
 The advantages of scavenging in the four-cycle motor have not 
 yet appeared great enough to warrant the more complicated 
 construction necessary to secure it. 
 
 Compound Motors. 
 
 17. Motors in which the expansion of the gaseous products of 
 combustion is carried out to a greater degree by the aid of a 
 secondary low-pressure cylinder than in the usual types where 
 all the expansion is in the combustion cylinder, are constructed 
 to a small extent. 
 
 One of the most recent four-cycle compound motors, used for 
 driving an automobile, has two vertical combustion cylinders of 
 the same size, with a secondary low-pressure expansion cylinder 
 between them. The pistons and all the cylinders are single- 
 acting. The length of stroke of all three pistons is the same, but 
 the low-pressure cylinder is of greater diameter than the others. 
 The two high-pressure pistons (those in the combustion cylinders) 
 move up and down in unison, while the low-pressure piston 
 moves in the opposite direction. The crank angle between the 
 
42 THE GAS ENGINE 
 
 low-pressure crank and the high-pressure cranks is 180 degrees 
 or half a revolution. There is no angle between the two high- 
 pressure cranks. 
 
 The high-pressure cylinders are each provided with an inlet 
 and an outlet port, both opening into the combustion chamber in 
 the usual manner. 
 
 FIG. 28. 
 
 Compound Motor. Four-Cycle, Three-Cylinder Automobile Type. 12 to 15 horse- 
 power. Section on plane of cylinder axes, 
 i and 2 are the combustion or high-pressure cylinders. 
 3 is the intermediate low-pressure cylinder. 
 
 The upper end of the low-pressure cylinder is connected to each of the high-pressure 
 cylinders by short passages with valves. The exhaust from the high-pressure 
 cylinders passes into the low-pressure cylinder, so that its piston is given an 
 impulse every downstroke. 
 
 The method of operating is as follows, dealing with the forward 
 cylinder first for convenience: The exhaust gases from the 
 forward high-pressure cylinder follow a short passage into the 
 low-pressure cylinder and through one of the inlet valves of the 
 latter. The exhaust valve of the forward high-pressure cylinder 
 and the corresponding inlet valve of the low-pressure cylinder are 
 opened and closed in unison. They open about the time of 
 completion of the explosion stroke, and remain open about half 
 
TYPES OF MOTORS 43 
 
 a revolution of the crank, while the upstroke of tl\e high-pressure 
 piston in a vertical engine forces the chemically inert gases into 
 the low-pressure cylinder, whose cylinder is descending on its 
 impulse stroke. During this part of the operation the pressure 
 of the gases on the two pistons is about the same per square inch 
 for both, but is slightly lower in the low-pressure cylinder. Since 
 the piston area of the latter is greater than for the high-pressure 
 cylinder, the low-pressure piston delivers a turning moment to 
 the crank which is greater than the resisting moment of the high- 
 pressure piston. The net result is that the additional expansion 
 of the gases develops mechanical power. 
 
 At about the completion of the downstroke of the low-pressure 
 piston its inlet valve closes (together with the exhaust valve of 
 the forward high-pressure cylinder) and its exhaust valve, at the 
 upper end of the cylinder, is opened to allow the escape of the 
 thoroughly expanded gases into the atmosphere as the low- 
 pressure piston moves upward. A similar operation is then 
 carried out by the rear combustion cylinder and the low-pressure 
 cylinder. The latter has two inlet valves, one for each of the 
 high-pressure cylinders. 
 
 The crank shaft receives an impulse at every half revolution 
 to keep up its rotation. The impulses on the crank shaft come 
 in the following order: forward piston, low-pressure piston, rear 
 piston, low-pressure piston. 
 
 An earlier type of compound motor, an English production, 
 has one high-pressure and one low-pressure cylinder. They are 
 placed side by side close together, and the combustion chamber 
 of the high-pressure one is connected by a large open passage to 
 the closed end of the other. The low-pressure cylinder has, of 
 course, the greater volume. The pistons are connected to 
 separate crank shafts, which are parallel to each other and geared 
 together so that the one for the high-pressure cylinder makes 
 two revolutions to one of that for the low-pressure cylinder. 
 The crank shafts are geared together in such a manner that the 
 high-pressure piston makes nearly a complete stroke, imme- 
 diately following combustion, by the time the low-pressure piston 
 has moved a very small portion of its outstroke. Both pistons are 
 
44 THE GAS ENGINE 
 
 single acting. The low-pressure piston then moves out rapidly 
 while the high-pressure one is completing the small remaining 
 part of its outstroke and moving back a short distance on its 
 exhaust stroke, and so on. 
 
 A double-acting, four-cycle, compound motor of this type with 
 two high-pressure and two low-pressure cylinders was recently 
 constructed in this country with a view to using it for boat pro- 
 pulsion. There were some modifications, however, in the design 
 which, while not changing the appearance of the motor, had 
 a great effect on its operation. The most notable change was 
 the placing of a large automatic valve in the passage between the 
 high-pressure and low-pressure cylinders so that none of the 
 gases could pass from the latter to the former. There may have 
 been certain advantages to be gained by doing this. But, in 
 addition to this, an igniting device was placed in the low-pressure 
 cylinder as well as in the combustion cylinder. The result was 
 as might well be expected. When the motor was started some 
 of the combustible mixture entered the low-pressure cylinder on 
 account of a missed explosion or some other cause. The igniter 
 fired it in the low-pressure cylinder and the explosion closed the 
 intermediate valve with such force as to shatter it. The same 
 injury might have occurred without the ignition device in the 
 low-pressure cylinder, after a misfire in the high-pressure one. 
 
 Impulse Frequency for Different Arrangements of Cylinders. 
 
 1 8. The following are the more customary methods of arrang- 
 ing the cylinders of motors, and the corresponding number of 
 impulses delivered to the crank shaft: 
 
 Two revolutions of crank shaft for each impulse: 
 Four-cycle, single-acting, single-cylinder motor. 
 Four-cycle, single-cylinder motor with combustion chamber at 
 middle of cylinder and two opposed pistons that recede 
 from the middle of the cylinder at the same time toward the 
 open ends of the cylinder during the impulse stroke, and 
 then return at the same time during the compression stroke. 
 
TYPES OF MOTORS 45 
 
 One revolution for each impulse: 
 
 Two-cycle, single-acting, single-cylinder motor. 
 
 Four-cycle, single-acting, two-cylinder motor with opposed 
 cylinders on opposite sides of the crank shaft and cranks at 
 1 80 degrees. 
 
 Four-cycle, single-acting, two-cylinder motor with the cylinders 
 on the same side of the crank shaft and the cranks at 
 o degrees. (Twin cylinders in some designs.) 
 Two-thirds of a revolution for each impulse: 
 
 Four-cycle, single-acting, three-cylinder motor with all three 
 cylinders on the same side of the crank shaft and the cranks 
 at 120 degrees. 
 One-half revolution for each impulse: 
 
 Two-cycle, single-acting, two-cylinder motor with both cylin- 
 ders on the same side of the crank shaft and the cranks at 
 1 80 degrees. (Twin cylinders in some designs.) 
 
 Compound motor, four-cycle, single-acting, three cylinders. 
 Two high-pressure or combustion cylinders and one low- 
 pressure or expansion cylinder, all three on same side of 
 the crank shaft. Low-pressure crank at 180 degrees with 
 the pair of high-pressure cranks. High-pressure pistons 
 move in unison in one direction, while the low-pressure piston 
 moves in the opposite direction. 
 
 Four-cycle, single-acting, four-cylinder motor with all cylinders 
 on the same side of the crank shaft and one pair of crank 
 shafts at 180 degrees with the other pair. One pair of 
 pistons move in unison in one direction, while the other pair 
 move in the opposite direction. 
 
 Four-cycle, double-acting pair of tandem cylinders with one 
 
 crank. 
 One-third revolution for each impulse: 
 
 Two-cycle, single-acting, three-cylinder motor with all three 
 cylinders on the same side of the crank shaft and the three 
 cranks at 120 degrees. 
 
 Four-cycle, single-acting, six-cylinder motor with all six cylin- 
 ders on the same side of the crank shaft and the cranks at 
 120 degrees in pairs. 
 
46 THE GAS ENGINE 
 
 Reversing the Rotation of the Motor. 
 
 19. The direction of rotation that the first impulse gives the 
 motor shaft depends only on the position of the crank at the 
 instant of ignition. This assumes that the motor is rotating at 
 only a very slow speed, or not at all. The four-cycle motor, 
 unless provided with mechanism for changing the time of valve 
 action, will soon stop if the first impulse starts it in the wrong 
 direction. Such reversing mechanism has not come into use for 
 four-cycle motors. 
 
 The two-cycle motor will continue to rotate in the direction 
 that the first impulse gives it when of the simple type that com- 
 presses its charge in the crank case, if the timer is adjusted so as 
 to continue to give ignition at the proper time. The absence of 
 mechanically operated valves, or of all valves, makes this possible. 
 
 The method of reversing small two-cycle motors of this class, 
 such as launch motors, is to cut out the ignition and allow the 
 motor to slow down. The timer is then set to give ignition before 
 dead center is reached, as the motor is still rotating, provided the 
 timer is not already in this position. The igniter is put into 
 action again when the motor has nearly stopped, and the first 
 impulse reverses the motor. The timer is then adjusted to the 
 proper setting for the reversed rotation. The motor may be 
 throttled during the reversing to prevent too strong an impulse 
 at the instant of reversal. 
 
CHAPTER II. 
 
 CARBURATION, CARBURETERS, PREHEATING THE CHARGE, 
 FUEL SUPPLY. 
 
 C arbitration of Air. 
 
 20. A motor that receives into its combustion cylinder a 
 charge composed of a mixture of air and vapor of some volatile 
 hydrocarbon which is normally a liquid at atmospheric temper- 
 ature and pressure, must be provided with some kind of a car- 
 bureter for enriching the air with fuel on its way to the cylinder. 
 
 The spray carbureter has come into general use for naphtha 
 and gasoline in this country. The characteristic of this type is 
 that the liquid hydrocarbon is drawn out of a small nozzle, or 
 group of nozzles, by the suction of the air going to the com- 
 bustion cylinder, or, in the two-cycle motors, by the air going 
 into the crank case of the primary compression cylinder. The 
 suction that causes the flow of liquid fuel is aided by gravity in 
 some types of the spray carbureter. 
 
 One carbureter will supply either one or more combustion 
 chambers or cylinders. It is general practice to use only one 
 carbureter for a multi-cylinder motor. 
 
 21. Primer for Carbureter using Volatile Fuel. It fre- 
 quently happens that a carbureter will not sufficiently enrich 
 the air in the usual manner when starting the motor. In order 
 to prime the carbureter, many are therefore provided with a 
 means of causing more fuel than usual to flow from the spray 
 nozzle just before starting the motor. The device for doing this 
 is called a primer. It is a simple hand-operated arrangement 
 that depresses the float of a float-feed carbureter, or opens the 
 fuel valve otherwise in other types, so that some of the liquid 
 can flow out into the mixing chamber or air passage without 
 the aid of the suction of the motor. 
 
 47 
 
Gasoline level 
 when engine is|||||| 
 at rest 
 
 FIG. 29. 
 Spray Nozzle Carbureter. Sectional View. 
 
 The gasoline is supplied from some source that maintains a level somewhat lower 
 than the open upper end (nozzle) of the vertical gasoline pipe. The air current 
 passes up by the nozzle during the charging stroke of the motor. The partial 
 vacuum due to the suction of the motor draws gasoline from the nozzle. The 
 gasoline immediately vaporizes and mixes with the air. The amount of gasoline 
 drawn out is regulated by the small valve at the elbow of the supply pipe. It 
 can also be regulated by the butterfly valve in the horizontal part of the air pipe. 
 When this air valve is turned from the horizontal position shown, so as to par- 
 tially close the air inlet, a greater degree of vacuum is formed at the spray nozzle 
 and more gasoline drawn out, thus, making a richer mixture. The real use of the 
 air valve, however, is generally for causing enough gasoline to be drawn out when 
 starting the motor. The slow speed at starting, as by hand cranking, does not 
 produce suction enough to draw out sufficient gasoline when the air valve is open 
 as shown. But closing it will cause enough fuel to be drawn out to make a 
 mixture rich enough for igniting. In such cases the air valve is opened com- 
 pletely after starting. 
 
 (48) 
 
CARBURATION 
 
 49 
 
 14 
 
 12 
 
 Float-Feed Spray Carbureter. Wheeler & Schebler, Indianapolis, Ind. 
 
 The gasoline flows up past the valve i into the reservoir (float chamber) 2. As 
 the gasoline rises in the reservoir it lifts the cork float 3 (which is horseshoe 
 shaped and extends around the sides of the main air passage). The float is 
 fastened to an arm that is pivoted at 4 and engages with the upper end of the 
 stem of valve i. When the float rises to the proper height it closes the valve i 
 and stops the inflow of gasoline at a level slightly lower than that of the spray 
 nozzle 5. The needle valve 6 is for regulating the size of the passage to the spray 
 nozzle. 
 
 When starting the motor the air all enters through the bottom air passage 7 whose 
 orifice into the main air passage surrounds the spray nozzle. The passage 7 is 
 always left full open. The mixture passes out as indicated. When the motor 
 is running, air also enters at the upper inlet passage 8 by opening the valve 9 
 against the resistance of the coil spring 10. The gate valve n, shown partly 
 closed, acts as a throttle to the passage of the mixture from the carbureter. It is 
 operated by the lever (or bell crank) 12. The throttle can be prevented from 
 completely closing by the adjustable screw 13 against which a projection on the 
 lever 13 strikes. 
 
 The force exerted by the spring 10 for holding the compensating air valve 9 closed 
 is regulated by the wing nut 14. 
 
 For priming or flushing the carbureter, the vertical pin 15 is pressed down against 
 the cork float. This can be done by pulling a wire or string attached to the 
 bell crank 16. 
 
50 THE GAS ENGINE 
 
 Another method of priming the motor is to put the volatile 
 fuel directly into the combustion chamber. A pet-cock (often 
 with a cup-shaped end to be used as a measure) is generally 
 provided for this purpose. 
 
 22. Float-Feed Spray Carbureter for Volatile Liquids. The 
 float-feed spray carbureter has a small reservoir in which a 
 hollow metal or a cork float is buoyed up by the liquid fuel. 
 The float is connected to a cone-point valve (float valve) which, 
 when the float is lifted to a certain height, stops the opening 
 through which the liquid enters from the main tank in which 
 the bulk of the fuel is carried. The short duct that terminates 
 as the orifice of the nozzle is led from the carbureter reservoir 
 into the air passage through which air is drawn into the motor. 
 This duct starts some distance below the level of the liquid, and 
 the nozzle terminates a slight distance above the level of the 
 liquid maintained by the float. The latter is adjusted to main- 
 tain this level at about one-sixteenth to one-eighth of an inch 
 below the nozzle in most cases, but the nozzle is sometimes as 
 much as an inch higher than the level of the fuel. 
 
 As the air is drawn through the air passage, its suction draws 
 the liquid from the nozzle and it is vaporized almost instantly 
 when the conditions are favorable. Drawing the liquid from the 
 nozzle lowers its level in the small reservoir of the carbureter, 
 and the float falls so as to open the float valve for letting in more 
 liquid and maintaining the proper level. 
 
 The rate of flow of fuel from the nozzle in proportion to the 
 rate of flow of air past it is adjusted by a needle valve that 
 partially stops the nozzle orifice or the passage leading to it. 
 This is the only adjustment in several makes of float-feed car- 
 bureters. Others, however, that are increasing in proportion 
 of numbers used have an air valve that is used to regulate the 
 intensity of suction at the fuel nozzle. In many modern designs 
 a single air valve is placed so that the air passes through 
 it before reaching the nozzle; the air valve is held to its seat by 
 a weak spring except when lifted by suction. By adjusting 
 both the needle valve and the air valve the mixture "can be given 
 correct proportions, within practical limits, for very greatly 
 
CARBURATION 5 1 
 
 different rates of flow of the air. In other words,.the carbureter 
 can be adjusted to keep the mixture ratio of air and fuel prac- 
 tically constant for a motor that runs at greatly different speeds 
 and whose power and speed are controlled by throttling the 
 charge at a point between the carbureter and the motor. It is 
 not unusual to find the spring-closed air valve in other parts of 
 the carbureter. 
 
 In some types of carbureters in which no spring-seated air 
 valve is used, two valves of the wing type that is common in 
 stovepipes, etc., are used. One is placed between the fuel nozzle 
 and the motor, and the other between the nozzle and the air 
 intake of the carbureter. They are then both moved in con- 
 junction to control the speed and power of the motor. By this 
 means both the speed of flow of the air and the intensity of 
 suction at the fuel nozzle are simultaneously regulated. 
 
 An adjustable stop to limit the lift of the air valve is provided 
 in some designs, but this is unusual. 
 
 In carbureters for automobile motors the small liquid reservoir 
 generally surrounds the air passage and the nozzle more or less 
 completely. The chief reason for this form of construction is to 
 provide a means to keep the level of the fuel in the nozzle constant 
 when the carbureter is tipped by the car passing over hilly and 
 uneven roads. The earlier types, and some still on the market, 
 were made with the small reservoir at one side of the air passage 
 and nozzle; this results, in some cases, in a lack of uniform 
 carburation of the air when passing over uneven roads. 
 
 A throttle valve is often placed in the carbureter between the 
 fuel nozzle and the motor. Wing and shutter type throttle 
 valves are in common use, as are tubular forms. 
 
 While only one fuel nozzle is the rule in float-feed carbureters, 
 some are made with several nozzles of the same size that act 
 simultaneously. In more unusual designs, nozzles of different 
 sizes are provided, all placed at the same level. This type of 
 carbureter is intended for motor cars where the demand for 
 mixture varies between wide limits. A large nozzle delivers 
 the liquid fuel when the demand for power is great, as when 
 climbing a hill, but when the throttle control is readjusted for 
 
52 THE GAS ENGINE 
 
 light power on a good, level road, the large nozzle is cut out and 
 a small one brought into action. 
 
 23. Pump-Feed Spray Carbureters for Volatile Fuel. For 
 stationary and other motors where the supply of fuel is carried 
 below the level of the carbureter, and no air pressure is used to 
 raise the liquid to the level of the carbureter, the open spray 
 nozzle type, in which the constant level of the fluid fuel in the 
 small reservoir of the carbureter is maintained by a pump, finds 
 considerable use^ The fuel pump generally forms part of the 
 motor and is naturally very small. It pumps more fuel than 
 the motor requires at any time, and the level is maintained by an 
 overflow pipe or opening that takes the surplus fuel back to the 
 main supply tank or its connections. 
 
 24. Pump-Feed Carbureter with Measuring Cup. In this 
 type a small pump lifts the liquid fuel from the main tank and 
 discharges it into a small measuring cup or pipe end in the air 
 inlet pipe of the motor. The capacity of the measuring cup is 
 that for the amount of fuel required for one full charge of the 
 motor. The pump supplies more fuel than sufficient to fill the 
 cup, and the overflow returns to the main reservoir. The cup 
 is filled by the pump during the strokes of the motor piston that 
 come between impulse strokes. The suction of the air on its 
 way to the motor combustion cylinder empties the cap of its 
 complete charge of fuel. This type of carbureter is not suitable 
 for use in connection with a throttle in the air passage. 
 
 25. Disk-Feed Spray Carbureter for Volatile Liquids. In 
 this type of carbureter the vertical fuel nozzle opens upward 
 and is closed by a cone-point valve that points downward and 
 rests in the orifice by gravity and prevents the flow of liquid 
 when none is needed. The valve spindle is vertical and has a 
 thin metal disk attached to it. The disk is placed in and partly 
 closes the air passage leading to the motor combustion cylinder. 
 When a charge is drawn into the motor, the air, flowing upward 
 past the nozzle and disk, lifts the latter and the valve attached 
 to it, and thus opens the orifice so that the liquid fuel can flow 
 out into the passage for air, where it is vaporized and carried by 
 the air to the motor. 
 
CARBURATION 53 
 
 The supply tank is placed higher than the nozzle, and the 
 flow of the liquid is caused by both gravity and suction, except 
 when a compression supply tank is used, in which case the 
 compression pressure lifts the liquid to the nozzle. 
 
 In order to keep the valve and its seat free from dirt or deposit, 
 the disk has a few tongue-shaped pieces cut out of it except at 
 the part corresponding to the base of the tongue, and the point 
 of each tongue bent up slightly to make an opening through 
 which the air can. pass. This tongue somewhat resembles the 
 reed of a musical instrument. The length of each tongue is 
 parallel to the periphery of the disk, and all are pointed in the 
 same direction with regard to the rotation of the disk about the 
 valve stem. As the air passes through the openings and strikes 
 the tongues it causes the disk and valve stem to rotate some- 
 what in the manner of a wind motor, so that the valve spins 
 slightly on its seat when it settles down. 
 
 The adjustment for securing the proper proportions of air and 
 fuel in the mixture is made by regulating the height of the lift 
 of the valve. This is ordinarily done by means of an adjusting 
 screw that is placed above the valve and disk and is concentric 
 with the valve stem. 
 
 A spring-closed and adjustable air valve can be used in this 
 carbureter as well as in other types. The same is true of throttle 
 valves. They are, in fact, both used. 
 
 26. Diaphragm-Feed Spray Carbureters for Volatile Liquids. 
 In this type the vertical fuel nozzle is closed by a cone-point 
 valve whose stem is generally vertical. A circular diaphragm is 
 attached to the valve stem, and its periphery rigidly held by an 
 air-tight joint. Under the diaphragm is a small space that is 
 nearly air-tight and is of the same diameter as the free part of 
 the diaphragm. Above the diaphragm is another air space of the 
 same diameter, but connected with the passage through which 
 the air is drawn to the motor. When air is drawn into the motor 
 the reduction of pressure above the diaphragm by suction 
 allows the air confined in the space below the diaphragm to 
 expand and lift the latter, together with the attached valve, so 
 as to open the nozzle and allow the liquid fuel to run out by 
 
54 THE GAS ENGINE 
 
 both suction and gravity, or by suction and pressure when a 
 pressure fuel tank is used. The amount of fuel flowing out is 
 adjusted by a regulating screw against which the valve stem 
 strikes when it lifts. 
 
 Throttle control and a spring-seated air valve can be used in 
 this type of carbureter. 
 
 FIG. 31. 
 
 Carbureter Valve. The Lunkenheimer Company, Cincinnati, Ohio. 
 
 The gasoline is fed in by pressure to the passage around the needle valve 20 and 
 passes through a small orifice to the conical seat of the main valve 18. The 
 latter is pressed against its seat by the expansive action of the coil spring 19. 
 The gasoline orifice is closed by the valve 18 when the latter is seated. 
 
 The suction of the motor at the lower end B of the carbureter draws the valve 18 
 down from its seat so that air enters at the top C and flows down past the valve. 
 The suction and gravity (or pressure) both cause gasoline to flow from the open 
 nozzle when the valve 18 is drawn from its seat by suction and air is passing 
 through the carbureter. The flow of gasoline is regulated by the needle valve 20. 
 
 27. Spray Carbureters in General. Numerous types of the 
 spray carbureter other than those described above are in more 
 or less general use. The nozzle is vertical in nearly all. In 
 some cases it is slightly inclined from the vertical, as much as 
 forty-five degrees in one or two designs. The air current passes 
 in the direction that the nozzle points in the great majority of 
 designs; in a smaller number it passes across the nozzle at right 
 angles to the opening; and in a few isolated cases it comes down 
 against the orifice of the nozzle. 
 
 In some a coil of wire is used to act as the spring air valve 
 already mentioned and at the same time to break up the current 
 of air so as to make the mechanical mixture of the air and vapor 
 
CARBURATION 55 
 
 more complete than it is supposed to be without some mixing 
 device. One, a recent design, has a cylindrical wire cage at- 
 tached to one end of a propeller wheel and the whole mounted 
 on a central spindle. The fuel and air pass through the pro- 
 peller wheel and cage after coming together on their way to the 
 motor. The current of air and vapor causes the propeller wheel 
 and cage to rotate rapidly. The centrifugal action throws any 
 liquid, such as water or unvaporized fuel, out against the walls 
 surrounding the cage, and a dry mixture is thus secured. 
 
 FIG. 32. 
 
 Carbureter Valve. The Lunkenheimer Company. 
 
 This is a modified form of Fig. 31. Air enters at the lower opening C and the 
 mixture passes out at the upper opening B. Gasoline flows in at 5 and follows 
 a duct to the pocket back of the needle-valve point. The lift or movement of the 
 main valve F is regulated by the screw-threaded stem extending down from 
 the wheel 3 at the top. The top of the valve strikes against and is stopped by 
 the lower end of this stem. 
 
 One of the simplest carbureters, probably the simplest, con- 
 structed resembles an ordinary globe angle valve in general 
 appearance. The valve is pressed against its seat by a weak 
 spring that allows it to rise when the suction of the motor acts to 
 draw air through. A liquid-fuel supply pipe terminates in a 
 small orifice in the conical valve seat. When the valve rests on 
 
56 THE GAS ENGINE 
 
 its seat the orifice is closed and no liquid can flow into the air 
 passage, but when suction lifts the valve the orifice is uncovered 
 and the liquid fuel is drawn out by the suction, with some aid 
 from gravity or the pressure of a pressure system of fuel supply. 
 The liquid is vaporized as in other types of spray carbureters. 
 The lift of the valve is regulated by a screw above it that occu- 
 pies the place of the valve stem that is used in the ordinary angle 
 valve. The intensity of suction depends on the lift of the valve. 
 The latter can be completely closed by screwing down the regu- 
 lating screw. There is a needle valve in the fuel supply duct for 
 the regulation of the amount of fuel delivered. This carbureter 
 is intended for use only on motors that take a full charge for 
 each impulse stroke. It has proved very satisfactory for such 
 service. 
 
 28. Other Types of Carbureters for Naphtha and Gasoline. 
 One type of carbureter that was much used at one time but is 
 becoming less common on account of its displacement by the 
 spray class, has a considerable surface of metal on which the 
 gasoline or naphtha is allowed to run and is then vaporized by 
 air passing over it. The vaporizer is made in various forms. 
 One is a cone of wire gauze. In its operation the liquid is 
 dropped on the apex and runs down toward the base. The air 
 is drawn up through the gauze and rapid vaporization occurs. 
 Instead of the wire gauze a conically coiled wire or a piece 
 of perforated metal is often used. Different shapes find 
 application. 
 
 In the earlier forms the air was enriched with hydrocarbon 
 vapor to the saturation point, which gave a practically definite 
 amount of fuel per cubic foot of air, and then the saturated mix- 
 ture was diluted by mixing it with pure air until the ratio of 
 pure air and hydrocarbon vapor became suitable for complete 
 combustion. 
 
 In most of the later types the liquid fuel is directly mixed with 
 the air passing into the motor, and in such a proportion as gives 
 a combustible mixture. The proportion of the liquid fuel is 
 regulated by some device similar in its general action to those 
 of the float-feed and disk-feed carbureters. 
 
Air Escape 
 
 SECTION B-B 
 
 Fl 
 
 Spray Carbureter with Gasoline and Water Nozzles. C 
 This carbureter is provided with a reservoir for water as well as one for gasoline. 
 
 carbureting chamber or pipe. The carbureter is double, with a gasoline noz; 
 
 one of the carbureting chambers and its nozzles are shown in the figures. 
 The water is mixed with the charge to cool down an overheated combustion ct 
 An excess of gasoline is pumped continuously into the gasoline reservoir of the carbl 
 
 allows the excess gasoline to escape and maintains a nearly constant level in the 
 
 constant level in the water reservoir of the carbureter in a similar manner. 
 The needle valve for regulating the gasoline (for either combustion chamber) is set 1 
 
 out past the spring-closed valve (which is opened by the suction of the motor) ar 
 The gasoline nozzle has three orifices. 
 This carbureter was used on a four-cycle, single-acting motor with two cylinders 
 
Air Escapes 
 HORIZONTAL SECTION A-A 
 
 SECTION G-G 
 
 Water 
 
 I 
 
 /'"" ' ' 
 
 SECTION D-D 
 Through the Water Chamber 
 
 Needle Valve' 
 for control of water 
 [RTICAL SECTION C-C to the mature 
 
 3. 
 
 ant Level of Gasoline and Water by Overflow Method. 
 
 as separate spray nozzles for water and for gasoline, both opening into the same 
 
 , water nozzle, and a carbureting chamber for each combustion chamber. Only 
 
 er and prevent premature ignition. 
 
 :r by a pump driven by the motor. An overflow opening in the carbureter reservoir 
 
 rvoir. The overflow runs back to the supply tank. The water is maintained at a 
 
 e a richer mixture than is to be used in the motor. This over-rich mixture flows 
 m mixes with more air on its way to the motor. 
 
 6J inches diameter of bore, and with a piston stroke of 10 inches. 
 
CARBURATION 57 
 
 29. Cooling Effect of Vaporization. The vaporization of a 
 liquid requires heat. When the liquid fuel is vaporized in a 
 spray carbureter the necessary heat is abstracted^from the air 
 with which the vapor mixes, and from the metal of the carbureter. 
 Most of the vaporization takes place just beyond the fuel nozzle 
 in the spray carbureter. As a result the metal in that neighbor- 
 hood becomes very cold. It is not unusual to find it covered 
 with frost even in hot, dry weather, but this occurs to a more 
 marked extent in a cool, moist atmosphere. The heat con- 
 ductivity of the metal causes the entire carbureter to become 
 cold and chill the liquid fuel so that it will not vaporize so readily. 
 With the better qualities, or more correctly, the more volatile 
 fuels, this cooling by vaporization does not need much, if any, 
 consideration so far as the vaporization is concerned. 
 
 But frost and ice not infrequently collect, in very humid or 
 rainy weather, to such an extent that the inside of the air passage 
 or mixture chamber where the vaporization occurs becomes 
 coated with frost and ice. This is apt to interfere with the 
 operation of the throttle valve, or even to obstruct the air passage 
 to such an extent as to affect the working of the motor. When 
 the poorer or less volatile grades of oil are used, they will not 
 always vaporize at atmospheric temperature even before the 
 carbureter has become cooled. 
 
 30. Heating the Carbureter or the Air. In order to pre- 
 vent the formation of ice in the carbureter, and to make it 
 possible to use the lower and less volatile grades of naphtha and 
 gasoline, either the air is heated before reaching the carbureter 
 or the carbureter itself is heated by a hot-water or hot-oil 
 jacket. 
 
 The hot-water jacket generally extends around the part of the 
 air passage where the most vaporization occurs, and also around 
 the carbureter reservoir when a float is used, or around the 
 portion where the liquid fuel enters the carbureter when there 
 is no float reservoir. The hot water or oil for jacketing is taken 
 from that used to cool the motor cylinder when the latter is 
 liquid-jacketed. The liquid-warmed carbureter is used only in 
 connection with a water-cooled or oil-cooled motor. 
 
58 THE GAS ENGINE 
 
 Preheating the air before it passes into the carbureter is 
 generally accomplished by causing it to pass over some of the 
 heated surface of the motor cylinder or exhaust pipe. The 
 intake pipe frequently has one branch that takes in preheated 
 air, and another that receives air at atmospheric temperature. 
 By the use of adjustable valves the air is taken in through either 
 or both, as desired. 
 
 31. Carbureters for Kerosene and other Non-Volatile Liquids. 
 A temperature much higher than that of the atmosphere is 
 necessary for vaporizing kerosene and others of the heavier dis- 
 tillates of petroleum. In the very numerous designs that have 
 been used, the heat for raising the temperature to the vaporiza- 
 tion point has generally been taken from the exhaust gases by 
 passing them around or through the carbureter in passages 
 provided for the exhaust gas. The chief difficulty met has been 
 the keeping of the carbureter at a proper temperature at all 
 loads on the motor. The tendency in a simple form of car- 
 bureter through which all or always the same proportion of the 
 exhaust gases pass, is for the carbureter to become too cool on a 
 light load if it is so constructed that it does not become too hot 
 when the motor is working at about its full capacity. This 
 type of carbureter has been made to work satisfactorily on launch 
 and boat motors, where the rate of power generation is practically 
 constant. An auxiliary flame is required for keeping the car- 
 bureter hot when the motor stops, and for heating it before start- 
 ing after the parts have become cold. 
 
 When the temperature is kept high above the vaporization 
 point while the motor works at full load, there is apt to be trouble 
 from rapid deterioration of the metal of the carbureter, stoppage 
 of its passages, oxidation of the metal and deposit of carbon from 
 the fuel and exhaust and even from igniting the mixture while it 
 is still in or near the carbureter. 
 
 Some of the kerosene carbureters make a saturated mixture of 
 air and fuel vapor at a temperature well above the vaporization 
 point of the kerosene, and afterward dilute it with air, thus 
 securing a combustible mixture without an excessive temperature 
 of the entering charge. The heat of compression and that 
 
CARBURATION 59 
 
 received from the cylinder walls are relied upon to keep the 
 kerosene in the vapor state until combustion occurs. 
 
 The adjustment and handling of a kerosene carbureter when 
 in operation cannot be so readily and conveniently accomplished 
 as with one for gasoline, naphtha, and alcohol, on account of the 
 necessarily high temperature of the kerosene carbureter. Adjust- 
 ing screws and minute parts are injured by the heat, which also 
 opens joints and causes leakage. On the whole, the problem 
 of making a successful kerosene carbureter is far more difficult 
 than to make one for naphtha or alcohol. The result is 
 that the general tendency is to eliminate the use of the kero- 
 sene carbureter by injecting the liquid fuel directly into the 
 combustion space of the motor and to vaporize as well as burn 
 it there. 
 
 32. Early and Obsolete Forms of Carbureters. One of the 
 early methods of carbureting the air for internal-combustion 
 motors was to pass it more or less directly through the liquid fuel, 
 as from the submerged opening of an air pipe partly immersed in 
 the liquid. The bubbles of air, rising up through the liquid, 
 became more or less completely saturated with the vapor of the 
 liquid. Heat was added to the less volatile liquids to bring them 
 up to the vaporization temperature. 
 
 Another method was to blow air down against the surface of 
 the liquid so as to agitate it and absorb its vapor. 
 
 The above two methods are still applied to a small extent in 
 the carbureters for kerosene and others of the less volatile liquids. 
 It is difficult in them, almost impossible in fact, to secure the 
 proportions of an economical combustible mixture in this manner. 
 The usual method of using them, therefore, is to make a saturated 
 or over-rich mixture and then dilute it with air to the desired 
 proportions. 
 
 Still another early method was to drop or flow the liquid fuel 
 on an absorbent piece of cloth or other textile fabric, cotton or 
 woolen wicking, or the waste fiber from textile mills. The air 
 was passed through the fabric or waste and thus became car- 
 bureted. The cloth or fibers gradually became fouled by dust 
 carried in by the air, and in some cases by deposits from the 
 
60 THE GAS ENGINE 
 
 liquid. The rate of carburation therefore changed, and the 
 fabric had to be renewed. 
 
 The capillary action of wicks was also utilized by placing 
 them partly in the liquid with one end extending into the air 
 passage, so that the fluid that crept up the wick was vaporized 
 and carried off by the air. The use of animal and vegetable 
 fibers in any form for carburation seems to have been dis- 
 continued completely in connection with internal-combustion 
 motors. 
 
 33. Effect of Preheating the Charge on the Power of the Motor. 
 
 - The amount of power that is developed in the motor from a 
 combustible charge of a given composition is almost directly 
 proportional to the "weight of the charge when the cylinder is 
 always filled to the same pressure before compression begins. If 
 a charge enters at a high temperature it will have less weight (for 
 the same volume) than one that is cool when it enters. This 
 assumes that both charges pass in through the same passages 
 without any change in the area or form of the opening in any 
 place. Under this condition the pressure in the motor cylinder 
 at the completion of charging will be the same in both cases. The 
 reduced weight of the hot charge means a corresponding reduction 
 of the fuel to be transformed into heat, and consequently less 
 power developed. 
 
 From the above it can be seen that, while preheating the air 
 is in many cases advisable, or even necessary, to secure vaporiza- 
 tion and prevent freezing of the carbureter on .-account of the 
 vaporization, it should not be carried to a higher temperature 
 than necessary if maximum power from the motor is desired. 
 The reduction of power capacity of the motor is one of the objec- 
 tions to the kerosene carbureter with its highly preheated air. 
 
 The mixture from a gasoline or naphtha carbureter that is not 
 jacketed by hot water, hot gases, etc., and takes its air at atmos- 
 pheric temperature, is much cooler than the atmosphere when it 
 enters the motor. This is one of the reasons why a motor running 
 on naphtha fuel will develop more power than when on gas fuel, 
 even though the heat value of a pound of the mixture is the same 
 in both cases. 
 
CARBURATION 6 1 
 
 
 Fuel Supply for Carbureters. 
 
 34. Gravity, Compression, and Pump Supply of Fuel. The 
 
 liquid fuel for a carbureter is either placed in a tank at a level 
 higher than that of the carbureter and flows down to the car- 
 bureter by gravity, or the supply tank is placed lower than the 
 carbureter and the liquid forced up by compressed air, gas or 
 vapor, or by a pump. 
 
 In the gravity system the tank should have a minute opening 
 or vent at the top so that air can enter it as the fuel flows out. 
 If this opening is not provided, the partial vacuum produced by 
 the flowing out of the liquid will first retard and finally stop the 
 flow. A very minute hole is sufficient for the vent, but it should 
 be large enough not to be easily clogged. About one-thirty- 
 second of an inch in diameter is the size generally used. 
 
 The pipe from the gravity supply tank to the carbureter 
 should not, under any condition, have large vertical bends or 
 any part much lower than the carbureter. Vertical bends or a 
 low pipe is apt to cause an air lock that will prevent the liquid 
 from flowing into the carbureter after it has been drained or 
 otherwise emptied, or when the supply tank is filled after being 
 completely empty. 
 
 In the compression system of fuel supply, air is forced into the 
 supply tank after it has been nearly filled with fuel. After the 
 motor is started the pressure is maintained in the tank by 
 the exhaust, frpm the motor. A common method of doing this 
 in automobile practice is to make a pipe connection between the 
 supply tank and the exhaust pipe of the motor. The connection 
 to the exhaust pipe is made very close to the motor. A check 
 valve is placed in the connecting pipe, generally near the motor, 
 which is the proper location. The back pressure of the 
 exhaust at the instant of its discharge is sufficient to force some 
 of the exhaust gases past the check valve and into the fuel tank. 
 The connecting pressure pipe must be of small diameter in order 
 to prevent the passage of a flame through it from the motor to 
 the tank in case the pipe should ever become filled with com- 
 bustible mixture. It may at first seem that there is a probability 
 
62 THE GAS ENGINE 
 
 of combustible mixture passing into the pipe when the motor 
 misses an explosion in the cylinder to which the compression pipe 
 is connected. But there is really little danger of this, since there 
 is no pressure in the combustion cylinder at the time of opening 
 the exhaust valve after a misfire. 
 
 The use of a pump to lift the fuel is confined chiefly to station- 
 ary motors, but a pump is used to some extent on portable 
 and semi-portable motors. In stationary motors the fuel is very 
 conveniently stored in the base of the motor. The plunger 
 type of pump is generally used for this purpose, and is driven 
 by the motor itself, of which it usually forms a part. 
 
CHAPTER III. 
 IGNITION. 
 
 35. General. The manner in which a charge is ignited in 
 an oil motor whose charge of fuel is injected in the liquid form, 
 has already been discussed in connection with the different 
 types of oil-burning motors. 
 
 The electric spark or electric arc has come into almost uni- 
 versal use for igniting the combustible charge when it is neces- 
 sary to have some source of heat for this purpose other than that 
 necessary to vaporize an injected liquid fuel, as in the oil-burning 
 motors. High-tension ignition, also called jump-spark igni- 
 tion, systems use a spark passing across the gap between two 
 permanently separated metallic points. In low-tension arc- 
 ignition systems, an electric arc is drawn at the instant a break 
 is made in the electric circuit by separating a pair of metallic 
 contact points. 
 
 A hot piece of metal, porcelain, or other substance with which 
 the combustible mixture is brought into contact, is still used to 
 some extent, however. One of the early methods was to bring a 
 flame into contact with the mixture at the moment it was to be 
 ignited. This is practically obsolete. The constantly burning 
 flame of the Bray ton motor has already been discussed. 
 
 36. Double Ignition. Two entirely separate ingition systems 
 are used in many of the better small motors, and quite commonly 
 in large ones. In automobile and launch motors both the high- 
 tension (jump-spark) and the low-tension (arc) systems are 
 installed. In large stationary motors the two systems are gen- 
 erally duplicates. 
 
 It is quite common practice to operate both ignition 'systems 
 at once in large motors, but this is not usual in the smaller ones. 
 In the latter case one system is generally held as a reserve. 
 
 63 
 
64 THE GAS ENGINE 
 
 37. Low-Tension Electric- Arc Ignition. This is often called 
 either the " make-and-break " or the " break-and-make " system, 
 since the electric circuit is completed and broken each time an 
 arc is formed. 
 
 A low-voltage electric current of a few amperes flows through 
 an insulated metal rod that pierces the wall of the combustion 
 chamber, in the arc system of ignition. A movable metal con- 
 tact, electrically connected with the metal of the motor, presses 
 
 FIG. 34. 
 Ignition Points. Low-Tension Make-and-Break. 
 
 The stationary contact point (ring) D and the rod that supports it are insulated 
 from the remainder of the complete igniter. 
 
 The contact ring C oscillates about the upper spindle and is brought into contact 
 with D just before the time for ignition, and immediately separated from it to 
 draw an arc. C and the parts attached to it are not insulated from the main 
 part of the apparatus or from the metal of the motor when the igniter is in place. 
 
 periodically against the inner end of the insulated rod. The 
 electric connection between the movable contact part and the 
 metal of the motor is generally made by the very simple means of 
 not insulating it from the cylinder where it pierces the latter's 
 wall. The stationary and moving igniter rods both generally 
 enter the cylinder through a removable plate or plug that forms 
 part of the cylinder wall when in place. The insulated rod and 
 
IGNITION 65 
 
 the metal of the motor cylinder are respectively connected to the 
 terminals of the source of electric supply. The separation of the 
 contact points inside the combustion cylinder draws an electric 
 
 / K 
 
 FIG. 35. 
 
 Make-and-Break Igniter in Place. 
 
 The igniter, Fig. 34, is here shown in place on the motor. The contact points are 
 inside a chamber which forms part of the combustion space of the motor. F is 
 the lay shaft (half-speed shaft) of the motor. The lay shaft rotates so that the 
 top moves out from the paper on which the illustration is printed. The projec- 
 tion on E engages with the spring I as F rotates and thus brings the contact 
 point C up against the stationary point D. Further rotary movement of E allows 
 7 to become disengaged from the projection on E and to snap back so as to 
 quickly separate the contact points and draw an arc. 
 
 arc that ignites the combustible gaseous mixture surrounding 
 them. 
 
 In the "make-and-break" system the contact points are brought 
 together and immediately separated to draw the arc. 
 
 The " break-and-make " method is to keep the contact points 
 together constantly except during the short interval that lies 
 between their separation and almost immediate bringing into 
 contact again. 
 
 A minimum amount of electric energy is consumed in the 
 make-and-break system, and injurious heating of the contact 
 points is hardly possible. There is a maximum opportunity for 
 carbon and oil to collect on the contact points, however, and foul 
 them so that they cannot come into electric contact when brought 
 together mechanically. 
 
66 
 
 THE GAS ENGINE 
 
 There is less liability to failure of the formation of the arc in 
 the break-and-make system on account of fouling of the contacts, 
 but it requires more electric energy if the source of electric supply 
 continuously delivers current at a uniform rate while the contacts 
 are together, but not a larger current than is required by the 
 make-and-break system. There is a greater tendency in the 
 break-and-make system than in the other to heat the contacts 
 when current flows during the entire time the circuit is closed 
 
 FIG. 36. 
 Double Make-and-Break Igniter. 
 
 at the contacts. Injurious heating by the current seldom occurs, 
 however, in an electric arc ignition system that is properly 
 designed and operated. 
 
 To secure the advantage of the greater certainty of closing 
 the circuit at the contact points than belongs to the break-and- 
 make system, and at the same time keep the liability of heating 
 as low as it is in the make-and-break system, special forms of 
 electric generators are used. These generators produce current 
 intermittently and during only a short period covering the instant 
 that the contacts separate to draw the arc. 
 
 Metals and alloys having a high fusing point were thought 
 necessary and were used exclusively in the early application of 
 electric-arc ignition. Platinum, iridium, and platinum-iridium 
 alloy were generally used. Platinum and iridium are so costly 
 

 IGNITION 67 
 
 as to make it desirable to substitute less expensive materials for 
 them. They have been almost completely displaced by steel 
 alloy contacts, which give better service, under the modern 
 methods of using them, than the more expensive metals pre- 
 viously used. It has been found that there is no necessity to 
 form the contacts into a point or anything approaching a point 
 in form. Blunt ends and flat or nearly flat surfaces are in 
 common and entirely successful operation. One form that has 
 given entire satisfaction has a broad steel ring, resembling a 
 washer, attached securely to the end of the insulated rod, and 
 another similar ring fastened to the moving part inside the 
 cylinder. The axes of the rings are more or less perpendicular 
 to each other, and their edges are brought together to close the 
 circuit. If a ring-shaped contact piece becomes worn or pitted 
 by fusing, it can be turned around slightly on its support so as 
 to bring a new portion of its edge into action. Nickel steel 
 alloy has been found good for contacts, along with other kinds 
 of steel. 
 
 The insulating material for the stationary ignition rod that 
 pierces the wall of the cylinder is subjected to a high temperature 
 and must, therefore, be of a nature that will withstand the heat 
 and retain its insulating properties. Mica, lava, porcelain, and 
 asbestos are the materials generally used. The asbestos is more 
 especially used as a packing for the other materials. The mica 
 is used in thin pieces, stamped or cut to suitable form and laid 
 against each other. The joints must be made with care, since the 
 expansion and contraction due to heating and cooling of the 
 cylinder tend to open them and allow the escape of gas, especially 
 at the time when the pressure is high during and just after com- 
 bustion. 
 
 The spindle carrying the movable contact point generally has 
 an oscillatory motion in the cylinder wall, so as to give a rocker- 
 arm motion to the arm that carries the contact piece. In some 
 designs, however, the spindle has a rotary motion. There is 
 ordinarily no difficulty met in keeping a tight joint at the place 
 where the rocker arm pierces the cylinder wall. The pressure 
 of the confined gases forces the shoulder or collar of the spindle 
 
68 
 
 THE GAS ENGINE 
 
 against the inner surface of the cylinder wall, and thus keeps the 
 joint tight if the bearing surfaces are true. 
 
 In one type the contact points are pressed together by the 
 action of a spring connected to the external part of the rocker 
 shaft, either directly or by means of an outside rocker arm. The 
 
 FIG. 37. 
 
 Make-and-Break Igniter with Rotary Contact Piece. 
 
 The stationary contact piece B is insulated from the frame of the motor and from 
 the outer metallic bushing that surrounds the middle portion of B. The contact 
 point A is rotated by the motor at half the speed of the crank shaft for a four- 
 cycle motor, and makes contact with B at every revolution. 
 
 contacts are separated at the proper instant by the action of a 
 single-lobe cam on a shaft that rotates at the same speed as the 
 crank shaft in a two-cycle motor and at half the speed of the 
 crank shaft in a four-cycle motor. This refers to one cylinder of 
 a single-acting motor. The cam acts through a system of rods and 
 levers that transmit the motion of its follower to the movable arm 
 of the igniter. 
 
IGNITION 
 
 69 
 
 In order to secure a very rapid separation of the 'contact parts, 
 a " hammer-blow " device is sometimes used. The rocker arm 
 of the igniter supports a comparatively heavy part, the hammer, 
 that is free to rotate on it. The parts that move the igniter press 
 the hammer back against the resistance of a spring while the con- 
 tact points remain together. The hammer is then released, and 
 the spring throws it back quickly. It strikes an arm that is 
 rigidly connected to the rocker shaft of the igniter point with a 
 blow that forces the contacts apart almost instantly. The rapid 
 
 4 
 
 FIG. 38. 
 
 Rotor of Make-and-Break Igniter. 
 
 The rotary contact part of the igniter shown in the preceding figure has a graphite 
 bearing, shown in black, for the rotating spindle 2. This eliminates the necessity 
 of lubrication with oil, since the graphite is a solid lubricant. The graphite is 
 not an insulator. 
 
 separation reduces the fusing action of the arc, as compared with 
 that of slow opening, by breaking the arc almost as soon as it is 
 formed. Modern practice does not seem to show any necessity 
 of breaking the circuit and the arc any more rapidly than can be 
 done with the simpler, direct-acting arrangement more generally 
 used. 
 
 38. Sources of Electric Supply for Ignition. An electric 
 generator is the best source of supply for the low-tension arc 
 system of ignition. The current provided must be flowing as 
 a direct current at the instant of separating the contact points 
 and drawing the arc at the igniter. The nature of the current 
 at other times when the circuit is closed is immaterial (except 
 that it must not be large enough to injure the apparatus). 
 
THE GAS ENGINE 
 
 It may be either direct continuous or pulsating, intermittent or 
 alternating. Generators that are used solely for this purpose, 
 and are practically a part of the motor accessories, are in com- 
 mon use. Both magneto-generators and those with electrically 
 excited magnetic fields are suitable. The former has the 
 advantage of being less complicated, but is more bulky and 
 generally heavier than the electrically magnetized type. When 
 the electric generator is suited to its work, one of its terminals 
 is connected directly (electrically) to the insulated rod that 
 carries the stationary contact point, and the other terminal of 
 
 FIGS. 39 AND 40. 
 Magneto with Shuttle- Wound Armature. Alternating-current Type. 
 
 1. Permanent magnets. 3. Armature core. 
 
 2. Armature. 4. Armature shaft. 
 
 5, 6. Insulated slip rings to which the two terminals of the armature winding are 
 connected and on which the brushes bear for carrying the current away 
 from the magneto. 
 
 The armature wire is wound around the neck that connects the two convexed ends 
 (or sides) of the core. 
 
 the generator is "grounded" by connecting it (electrically) to 
 the metal of the motor at any convenient place. It will not 
 give more current when thus short-circuited than it and the 
 contacts in the cylinder can safely carry. In some cases the 
 moving part of the generator rotates at a speed either constant 
 or proportional to that of the motor; in others it is either 
 
IGNITION 71 
 
 oscillated or moved intermittently and always in the same direc- 
 tion of rotation. 
 
 Direct continuous current generators and direct intermittent 
 current generators are the types generally used for low-tension 
 ignition. The direct continuous current generator is distin- 
 guished from others by its commutator of numerous (copper) 
 segments. 
 
 The type of generator commonly known as alternating can 
 be operated so as to give current which does not change its 
 direction during the period for drawing the arc. This method 
 of operating is described in sections 40 and 41. 
 
 In variable-speed motors, direct-current rotary electric gen- 
 erators for low-tension (arc) ignition are in a few cases driven 
 at a speed proportional to that of the crank shaft. They are 
 specially wound so as to give enough current for ignition at the 
 lowest speed of the motor, and not to give excessive current, or 
 to burn out on account of high voltage, at the highest speed of 
 the motor. It is more usual, however, for the generator to be 
 driven through a friction clutch which, is thrown partly out of 
 engagement at a certain speed that is the maximum predeter- 
 mined for the generator. Friction-pulley drives are also used 
 to limit the speed in a similar manner. The armature of the 
 generator thus driven never exceeds a certain speed, but main- 
 tains it when the motor runs at its slowest speed. Generators 
 of this class will give an arc hot enough to ignite the charge in 
 the combustion chamber at the speed that a small motor can be 
 cranked by hand. The generator is therefore all that is neces- 
 sary to supply electric energy for ignition purposes. 
 
 An electric battery of dry cells, or a storage battery, can be 
 used for low-tension arc ignition. The battery runs down 
 rapidly, however, even when the make-and-break system is used, 
 as distinguished from the break-and-make. A "kick coil," 
 also called a "choke coil," should be used in the battery circuit 
 to draw a longer and stronger arc by its inductive action than 
 can be produced by the battery without it. The choke coil is 
 made by winding a considerable number of turns of insulated 
 copper wire around a soft-iron core. The core is usually made 
 
72 THE GAS ENGINE 
 
 up of a number of small rods or short, straight pieces of soft 
 iron wire gathered into a sheaf or bundle. The axis of the 
 bundle coincides with that of the copper coil. 
 
 The chief use of the battery, in connection with low-tension 
 ignition, is for starting the motor. The generator can be 
 switched on for continued use. 
 
 When both a storage battery and a generator are thus used 
 for igniting purposes they can be so connected together that the 
 generator always keeps the battery charged and ready for use. 
 The latter is thus always a reserve factor to be brought into use 
 in case the generator fails. This method is known as " floating 
 the battery on the line." 
 
 39. Low-Tension Arc Igniter with Solenoid Circuit Breaker. - 
 This igniter differs from the ones of the type just described in 
 that it does not require the motor to have as a part of its mechan- 
 ism proper any device for separating the contact points. Their 
 separation is accomplished by the magnetic action of a current 
 passed through a solenoid coil that forms part of each spark 
 plug. The igniter is compact in form and size. It screws into 
 a hole in the cylinder wall. T^he hole is generally of the standard 
 size for a half-inch gas pipe. A wire from the electric generator 
 connects to its one binding post. The " grounding" of the 
 outer casing of the plug is accomplished by screwing it into the 
 metal of the cylinder. This completes the electric circuit, since 
 the second terminal of the generator is also "grounded" to the 
 metal of the motor. In general appearance the plug resembles 
 the common form of high-tension spark plug to be described 
 later. 
 
 When no current is passing through the solenoid the soft- 
 iron movable core is forced out by a spring, so that its end presses 
 against a metal bridge that spans the open end of the core space 
 of the coil. The metal bridge is a part of the outer shell that is 
 threaded to screw into the cylinder. When a current is passed 
 through the solenoid its core is drawn in against the resistance 
 of the spring and away from contact with the bridge. The 
 path of the current is through the contact points before they are 
 separated, so that their separation draws an arc between the end 
 
IGNITION 73 
 
 of the solenoid core and the bridge. The arc ignites the com- 
 bustible gases in the cylinder. 
 
 An electric generator especially designed to supply current to 
 the arcing plug is used with it. A timer on the generator closes 
 the circuit to each plug in a multi-cylinder motor at the proper 
 moment, and delivers current to it long enough to separate the 
 contact points and draw the arc. A drop of heavy oil on the 
 contact points does- not prevent the formation of the arc when 
 the contacts are separated, although the oil still connects the 
 points. This system can be readily installed on a motor that 
 has no mechanism for separating the contact points. 
 
 40. Oscillating Electric Generator for Low-Tension Ignition. 
 - There are three features that are desirable in a low-tension 
 arc-ignition system. They are: 
 
 T. Contact points kept pressed together except during the 
 instant the arc is drawn; 
 
 2. Current supplied only when needed at the time that the 
 
 contacts are separated to draw the arc; 
 
 3. An electric generator, operated entirely by the motor, 
 
 that will supply the right amount of current what- 
 ever the speed of the motor, and also when the motor 
 is moving very slowly, as when "cranking" a small 
 motor by hand, or "barring" a heavy motor to start it. 
 
 By the use of an electric generator which produces an inter- 
 mittent current a system embodying these desirable features has 
 been evolved and is in general use. 
 
 In the oscillating generator the armature never makes a 
 complete rotation, and the oscillations of the armature are 
 intermittent. The armature is forced to one extremity of its 
 oscillation by a spring. 
 
 When the motor is- running, the armature, oscillator, or rotor is 
 slightly rotated, through a fraction of a revolution, against the 
 resistance of the spring, at a comparatively slow rate, by a cam, 
 pin, or other device moving in unison with the motor shaft. Just 
 before the time for separating the contact points the armature 
 
74 
 
 THE GAS ENGINE 
 
 is released and snaps back by the action of the spring. This 
 motion is rapid enough, and through a sufficient part of a revolu- 
 tion to generate enough current to make an electric arc hot enough 
 to ignite the charge when the contacts inside the combustion 
 chamber are separated. The separation of the contacts is gen- 
 erally done by mechanism connected to the armature or oscillator 
 so as to move in unison with it. The separation is made when 
 the current is at or near its maximum. The contacts come 
 
 FIG. 41. 
 
 Position of the armature of the magneto at which no electromotive force and current 
 are generated during its rotation or oscillation. The arrows indicate the direction 
 of flow of magnetism, or magnetic flux. 
 
 together again almost instantly, but no appreciable current passes 
 through them till the armature is again snapped over. The 
 motion of forcing the armature over against the resistance of the 
 spring is so slow that no appreciable current is produced. 
 
 The amount of current generated and the intensity of the arc 
 do not in any manner depend on the speed of the motor. Even 
 if the motor is not rotating, a charge can be ignited by this device 
 by drawing over the armature and allowing it to snap back. The 
 motor can be started from rest in this manner if the piston is in 
 
IGNITION 
 
 75 
 
 position for the impulse stroke and the cylinder charged with 
 combustible mixture. 
 
 Generators of this type generally have permanent field magnets. 
 Electromagnets can be used, but the necessity of maintaining a 
 source of electric current supply is generally a sufficient reason 
 for not using them. The armature may be made stationary out- 
 side the field magnet, which is then made small and mounted so 
 as to oscillate in the manner already described. 
 
 FIG. 42. 
 
 Position of magneto armature at about which the voltage and current generated by 
 a uniform speed of rotation are a maximum. When the armature rotates at a 
 
 . uniform speed from the position of Fig. 41 to that of Fig. 42, the pressure (and 
 current if the external circuit is kept closed) keep increasing till a maximum of 
 each is reached at about the position of Fig. 42. The maximum value of the 
 current lags somewhat behind that of maximum pressure when the external cir- 
 cuit is kept closed. 
 
 In a variable-speed motor, as one on an automobile, the 
 separation of the contact points will not always occur when the 
 piston is in the same position. This is because the time interval 
 between the release of the armature and the separation of the 
 contacts in the cylinder is always the same whatever the speed 
 
76 THE GAS ENGINE 
 
 of rotation of the motor. If the release is made when the crank 
 is on the dead center and the piston just ready to begin its impulse 
 stroke, the contacts will not separate until the piston has moved 
 out some on its stroke. The distance that the piston moves out 
 will be greater the higher the speed. 
 
 Some means of readily adjusting the time of release of the 
 armature while operating the motor is therefore desirable on a 
 variable-speed motor, and is generally provided. Such a quick 
 means of adjustment is not needed on a constant-speed motor, 
 but some means of setting the release to the best position, where 
 it is to remain permanently as long as the same fuel is used and 
 the demands for power do not change greatly, is desirable. 
 
 41. Generator with Interrupted Magnetic Circuit, for Low- 
 Tension Intermittent Current. A very simple device for gener- 
 ating electric' current intermittently as required for ignition in 
 an internal-combustion motor finds application to some extent. 
 It is a simple form of generator whose stationary armature con- 
 sists of a permanent magnet, more or less horseshoe- or U-shaped, 
 upon which is wound a single coil of insulated wire. 
 
 The gap between the ends of the magnet is alternately bridged 
 by a keeper and opened by its removal. The nature of its con- 
 struction and operation is illustrated by winding an insulated 
 copper wire around the bar of an ordinary horseshoe- or U- 
 shaped magnet and electrically connecting the ends of the wire 
 so as to form a closed coil. When the keeper is removed from 
 the magnet an electric current is induced in the coil. The same 
 is true when the keeper is replaced. The quicker the removal 
 and replacement of the keeper the greater the current generated. 
 
 If the magnet is of sufficient size and strength, and the move- 
 ment of the keeper is rapid, an arc can be drawn by separating 
 the ends of the wire at the same instant that the keeper is removed 
 or replaced. It is not necessary that the keeper shall come into 
 metallic contact with the magnet poles. The same effect can be 
 produced by passing a bar of iron or soft steel between the poles 
 of the magnet. 
 
 One form of apparatus used for ignition by a current generated 
 in this manner has an air gap in the magnet core nearly closed 
 
IGNITION 77 
 
 most of the time by the edge of a rotating iron 'disk or the rim 
 of a wheel that passes between the poles. The disk or wheel is 
 attached to the crank shaft of the motor. A notch is cut in the 
 disk edge or wheel rim. As the notch passes between the magnet 
 poles the magnetic circuit is interrupted, as by removing the 
 keeper from the poles, and a current is induced in the coils. The 
 contact points are separated at the same instant in the combustion 
 chamber and an arc is drawn. The contact points and the induc- 
 tion coil are, of course, electrically connected. 
 
 The notch in the disk or wheel rim is generally filled with some 
 non-magnetic material, such as copper, brass, lead, wood, wood 
 fiber, etc., so as to form continuous smooth surfaces. 
 
 42. High-Tension Jump-Spark Electric Ignition in General. 
 A single electric spark, or a series of sparks, jumping across a 
 permanent gap or break in the metallic circuit, and passing 
 through the combustible mixture in the cylinder of a motor, is 
 the means adopted to a very considerable extent for igniting the 
 charge in an internal-combustion motor. A high electromotive 
 force or pressure is necessary to force the -park across the gap. 
 This is secured by the use of an induction coil that transforms 
 a current of an ampere or less and of only a few volts pressure 
 into electric energy of enormously higher tension and correspond- 
 ingly less volume. The low-tension current is supplied by a 
 battery or a low-tension generator. A "timer" is used in con- 
 nection with the battery. The function of the timer is to close 
 the battery circuit so that a current can flow from the battery 
 through the induction coil at the proper instant to produce 
 a spark in the combustion chamber. A generator, instead 
 of the battery, is very often used to supply the low-tension 
 current. 
 
 The generator, the timer, the induction coil, and a distributer 
 for directing the high-tension current to the different combustion 
 chambers of a multi-cylinder motor, are all sometimes brought 
 together and embodied in a single piece of apparatus. This 
 combination is commonly known as a high-tension magneto, 
 because a magneto generator has been used for this purpose up 
 to the present time. 
 
THE GAS ENGINE 
 
 43. Jump-Spark Igniters for Electric Ignition. Spark Plugs. 
 
 The jump-spark igniter for high-tension ignition is, with few 
 exceptions, made up of a central metal wire surrounded by a 
 thick tube of insulating material which, in turn, fits into a hol- 
 
 FIG. 43. 
 Spark Plug for High-Tension Jump-Spark Ignition. Porcelain Insulation. 
 
 The central rod or wire S is insulated from the outer metal parts by the porce- 
 lain P. Asbestos packing is used around the swell just below the middle of 
 the porcelain. Copper or asbestos packing is used on the central wire at the 
 shoulder U. The spark jumps across the gap between the lower end of the 
 central wire and the curved wire set into the lower end of the outer metallic 
 bushing. 
 
 low metal plug threaded on the outside so as to screw into a 
 threaded hole in the wall of the cylinder of the motor or into 
 some part that fits into the cylinder wall. The insulating material 
 
IGNITION 
 
 79 
 
 is generally either porcelain or mica. The former is used in one 
 tubular piece, and the latter is made up of numerous disks 
 perforated for the central wire and placed side by side over it. 
 Lava is also used for insulation to a limited extent. When 
 porcelain is used, tight joints are made between the central wire 
 and the porcelain, and between the porcelain and outer bush- 
 ing, by the use of asbestos fiber packing or 
 of soft copper washers. A fine copper wire 
 wrapped with the asbestos fiber is especially 
 convenient for this purpose. In general 
 practice either the central wire of the 
 spark plug terminates in an end of small 
 diameter near some part of the outer shell, 
 or a small wire is fastened to the outer shell 
 and brought near the enlarged end of the 
 central wire. The gap left between the end 
 of the wire and the larger body of metal 
 near which the wire terminates, is jumped 
 by the spark when the igniter- is in oper- 
 ation. This gap is called the " spark 
 Its width is about one-thirty-second 
 
 gap. 
 
 FIG. 44. 
 
 Spark Plug for Jump 
 Spark, 
 lation. 
 
 Mica Insu- 
 
 ers of sheet mica. 
 The black portion 
 indicates the mica. 
 
 of an inch. The insulation between the 
 central wire and the outer shell is all the 
 insulation that is between the two sides of 
 the high-tension circuit at the spark plug. The insulation is made 
 The standard size of the plug is that of up of disks or wash- 
 a half-inch gas-pipe plug as made in this 
 country. The French plug is smaller at the 
 threaded part of the outer shell, but of nearly 
 the same size elsewhere. Plugs intended for special motors 
 are generally larger than the American standard. One special 
 type has two insulated wires passing through a plate of con- 
 siderable diameter. This secures double insulation between 
 the two sides of the high-tension circuit. The ends of the 
 wires are brought to within about one-thirty-second of an inch 
 of each other. This type of plug is held in place by a yoke 
 that spans it. 
 
80 THE GAS ENGINE 
 
 44. Timers for High-Tension Electric Ignition. When a 
 battery is used to supply current for high-tension jump-spark 
 ignition, a timer is placed in the battery circuit to close it at the 
 moment a spark is required. The timer controls the time of 
 flow of the low-tension current. Of the principal parts of the 
 timer, one is stationary and the other rotates. They are elec- 
 trically insulated from each other. As the rotor revolves, a metal 
 contact piece on it comes against the metal of the stationary part 
 at intervals and closes the electric circuit. There are as many 
 metallic contact pieces on the stationary part as there are induc- 
 tion coils in use for operating the motor, in the more common 
 and simpler device. (Other forms will be described later.) 
 The contact pieces are placed around the circular path of the 
 rotating contact piece so as to close the circuit at the time re- 
 quired for each cylinder of the motor. The stationary part is 
 adjustable to a slight extent by rotary motion around the rotor 
 shaft, so that the time of closing the circuit can be varied to meet 
 the requirements of the motor. 
 
 In the better modern designs the stationary part generally 
 consists of a ring of wood fiber supported on a metal part 
 that is bored to receive the shaft of the rotor. The contact 
 points in the stationary part are attached to the insulating ring 
 so as to be insulated from each other and from the shaft of 
 the rotor. The rotor has only one contact piece, and in some 
 designs it has rigid metallic connection with the rotor shaft; 
 in others it is insulated from the shaft, but permanently con- 
 nected by a rubbing or rolling contact with the metal ring that 
 is part of the stationary member of the timer and is electrically 
 connected to the metal of the motor. The contacts are pressed 
 together by the action of a spring. The moving parts are either 
 packed with soft grease or copiously lubricated with oil. 
 
 In automobile practice the frequent movement of the adjust- 
 able (stationary) part of the timer breaks the wires that lead 
 from its contact pieces to the other parts of the apparatus. In 
 order to prevent this trouble the adjustable part is surrounded 
 by a case that is truly stationary with regard to the -motor frame, 
 and the leading-out wires are connected to binding posts on the 
 
IGNITION 8 1 
 
 casing. The electrical connections between tfye case and the 
 adjustable part are made by sliding contact. 
 
 The speed of rotation of the timer is half that of the crank 
 shaft in the ordinary type of four-cycle motor. In the two- 
 cycle motor the timer rotates at the same speed as the crank 
 shaft. 
 
 45. Induction Coils for Electric Ignition. The induction 
 coil used for high-tension ignition in motor practice has a central 
 core of very soft, small iron wires arranged in a circular bundle. 
 Insulating material in the form of a tube covers the core. Com- 
 paratively coarse copper wire is wound around the insulating 
 tube in the form of a solenoid coil of a few layers and several 
 turns. This is the low-tension coil, primary coil, or battery coil. 
 The turns of wire are insulated from each other either by using 
 a wire with an insulating covering or by carefully winding bare 
 wire over a thickness of sheet insulation for each layer, so that 
 the turns of wire do not touch each other, and then filling the 
 spaces between the wires with paraffine. One end of the pri- 
 mary-coil wire is attached to a binding post for receiving a battery 
 wire, and the other end connects to a device for interrupting the 
 current. 
 
 The interrupter has a thin, flat spring (vibrator, trembler) 
 that is rigidly held at one end so that a metal contact point near 
 the free end is pressed against a mating point. The metal 
 parts to which the two contact points are attached are electri- 
 cally insulated from each other when the points are separated. 
 The second wire from the battery is connected to the part of the 
 interrupter that is insulated from the side to which the primary- 
 coil wire is connected. The free end of the spring has attached 
 to it a disk of soft iron that is held just opposite one end of the 
 soft-iron core of the coil and at a short distance from it. When 
 a current of electricity is passed through the coil it magnetizes 
 the iron core, which then attracts the metal disk and draws both 
 it and the free end of the spring toward it. The contact points 
 are thus separated and the current interrupted. The core then 
 quickly loses its magnetism, and the elasticity of the spring 
 brings the contact points together, so that current again passes 
 
82 THE GAS ENGINE 
 
 through the coil. This operation is repeated and continued as 
 long 'as the battery supplies sufficient current. 
 
 A second coil (secondary coil, high-tension coil, spark-plug 
 coil) is wound over the first. It is of exceedingly thin wire and 
 has an extremely great number of turns. The turns and layers 
 of wire are insulated from each other in the same manner as in 
 the inner coil. The outer coil is carefully insulated from the 
 inner one that carries the low-tension battery current. One 
 end of the outer coil is connected to the same binding post as 
 the end of the inner coil of coarse wire (primary coil). The 
 other end of the outer coil is terminated at a binding post of its 
 own. The apparatus thus has three binding posts or terminals 
 for receiving wires from outside. 
 
 One terminal is at the battery side of the interrupter; an- 
 other, which may be called the intermediate terminal, is between 
 the ends of the inner and outer coils; and the third terminal is 
 at the remaining end of the outer coil. 
 
 The inner coil of coarse wire and few turns is designated, as 
 has already been indicated, either as the primary winding or 
 coil, the low-tension winding or coil, or the battery winding or 
 coil. 
 
 The outer coil of thin wire and many turns is known as the 
 secondary winding or coil or as the high-tension winding or coil. 
 
 When the battery current stops flowing through the primary 
 winding it induces a current of extremely high pressure and 
 very small volume, or amperage, in the secondary winding. 
 For ignition purposes the tension of this secondary current 
 should be at least great enough to give a spark across a one- 
 quarter-inch air gap. 
 
 An electric condenser is used in connection with the parts of 
 the induction coil that have just been described, and is a com- 
 ponent part of the apparatus. Its function is to strengthen the 
 action of the coil and protect the contact points at the interrupter 
 from fusing. The condenser is made up of sheets of tin foil 
 and paraffined paper laid together alternately, so that the paper 
 insulates the sheets of foil from each other. Alternate sheets of 
 the foil are connected together electrically to form one pole of 
 
IGNITION 83 
 
 the condenser, and the remaining sheets are likewise connected 
 together to form the other pole of the condenser. One pole of 
 the condenser is connected to the battery side of the interrupter, 
 and the other pole to the primary-coil side. 
 
 When the contact points of the interrupter are separated there 
 is a tendency for the battery current to keep flowing in an arc 
 across the gap thus formed. The magnetic core, acting induc- 
 tively on the primary coil, also has a tendency to maintain the 
 arc. 
 
 The condenser counteracts this combined effort to maintain 
 an arc at the interrupter contacts, by receiving and storing the 
 electric energy and thus breaking down the arc quickly. The 
 energy stored in the condenser is probably discharged back 
 through the primary circuit immediately after the primary 
 current is stopped, thus further increasing the inductive action 
 and the strength of the spark. 
 
 The induction coil, when not constructed especially for ignition 
 purposes, usually has four terminals instead of three. Each 
 end of the two coils is provided with its own binding post. Such 
 coils are still used, to a limited extent, for ignition purposes. 
 
 All parts of the induction-coil apparatus, except the inter- 
 rupter and binding posts, are enclosed in a box or case and 
 surrounded with paraffine poured in while melted. 
 
 American induction coils for ignition purposes are generally 
 wound to operate on from six to seven volts. Most of the foreign 
 coils require only about four volts. 
 
 A voltage much higher than that for which the induction coil 
 is constructed should not be applied to the primary coil. It will 
 injure the contact points by fusing and oxidizing them, and if 
 very much in excess of the right amount, may destroy the coil by 
 breaking down the insulation in the winding. 
 
 46. Batteries for Electric Ignition. Storage batteries and 
 those made up of dry primary cells are the only kinds used for 
 ignition to any extent on automobiles and launches. They are 
 the most suitable for the same use in connection with stationary 
 motors, even though the spilling of the liquid of a wet cell does 
 not have to be considered. The high internal resistance and the 
 
84 THE GAS ENGINE 
 
 polarization of wet primary cells when in use are the main 
 obstacles to their adoption for stationary motors. 
 
 47. Dry Batteries. The primary dry cell that finds most 
 use for ignition, has zinc and carbon for its elements; the electro- 
 lyte is a solution of sal ammoniac in water. 
 
 The sheet zinc used is made up into a round, cylindrical, open- 
 top cell. A solid stick of carbon (coke) is placed in the middle 
 of the cell and packed in with rather finely granulated coke. 
 Absorbent paper, such as blotting paper, is placed at the bottom 
 and top of the cell. The granulated coke is saturated with the 
 sal-ammoniac solution. The top of the cell is sealed with a thick 
 layer of pitch, poured in hot, and the end of the carbon stick 
 protrudes through the pitch cap. A binding post is attached to 
 the carbon and another to the edge of the sheet zinc. 
 
 The electromotive force of a carbon-zinc-sal ammoniac dry 
 cell is about ij volts when the cell is not giving out current. 
 The voltage drops while it is delivering current. From i to ij 
 volts is as much as a dry cell will ordinarily maintain when 
 furnishing electricity to an induction coil used for ignition, even 
 while the cell is still in good condition. Dry cells run down 
 rapidly in both voltage and capacity when in use for ignition, and 
 some even deteriorate rapidly while still new and not in use. 
 
 The carbon is called the positive element of the dry cell just 
 described, and the zinc is called the negative element. They are 
 indicated by the signs 
 
 (+ ) for the positive element; 
 ( ) for the negative element. 
 
 48. Series and Multiple Batteries. When dry cells are used 
 for ignition they must be connected together in groups so as to 
 give the required pressure and current. 
 
 For convenience the words carbon and zinc will often be used 
 instead of positive and negative, in referring to the various battery 
 connections. 
 
 In series battery connection the carbon of one cell is elec- 
 trically connected to the zinc of another, from cdl to cell. A 
 positive element is left free at one end of the series of cells, and 
 
IGNITION 85 
 
 likewise a negative element at the other end. These two free 
 elements are the terminals of the battery. 
 
 The connection of cells in series has the effect of adding their 
 voltages together to produce a voltage equal to their sum. If all 
 the cells have the same voltage, then the voltage obtained by 
 connecting them in series is found by multiplying the voltage of 
 
 Carbon Terminal 
 of Battery s 
 
 i Zinc Terminal 
 of Battery 
 
 FIG. 45. 
 
 Battery of Four Series-Connected Cells, 
 ij volts per cell. 5 volts between (+) and ( ). 
 
 one cell by the number that are connected in series. If five cells 
 whose working pressure (when delivering current) is ij volts 
 each, are connected in series, the voltage between the terminals 
 of the battery will be $ X i% = 61 volts. This is about the 
 voltage for American induction coils for high-tension ignition 
 purposes. 
 
 The voltage, or electromotive force, of a battery is the measure 
 of the pressure that forces electric current through the circuit to 
 be traversed. All parts of the circuit, including the battery 
 itself, offer resistance to the flow of current. The current must 
 pass through the battery, therefore the internal resistance of the 
 battery must be added to the resistance of the external circuit 
 (external resistance) in order to obtain the value of the total 
 resistance. The amount of current that a given voltage will 
 send through a given circuit is inversely proportional to the total 
 resistance of the circuit. 
 
 The elementary equation representing this is 
 
 Electromotive force 
 
 Current = 
 
 Total resistance of circuit 
 
 Electromotive force 
 
 Internal resistance + external resistance 
 
86 THE GAS ENGINE 
 
 If the external resistance of the circuit is so great in comparison 
 with the internal resistance of the battery as to make the latter 
 insignificant in comparison, then the current that a battery will 
 give is almost exactly proportional to the number of series- 
 connected cells of equal voltage in the battery. But, on the 
 other hand, if the external resistance of the circuit is very small 
 in comparison with the internal resistance of the battery, as when 
 the terminals of the battery are connected by a thick, short 
 copper wire, the addition of cells of equal voltage and internal 
 resistance, connected in series, will not appreciably affect the 
 amount of current that will flow, for the total resistance of the 
 circuit is increased in nearly the same proportion as the electro- 
 motive force. 
 
 Increasing the number of cells in a series-connected battery 
 does not increase the current in the same proportion. But when 
 the circuit includes an operating induction coil the proportionate 
 increase of current is greater, and more nearly in proportion to 
 the number of cells, than is indicated by an equation dealing only 
 with current, electromotive force, and resistance when the latter 
 is measured by a continuous, uniform flow of current. The 
 reason for this is that the inductive resistance of the circuit on 
 account of the rapid change in the rate of flow of current as the 
 .interrupter works greatly increases the external resistance above 
 that which the external resistance offers to a steady flow of 
 current. 
 
 Under the usual conditions of high-tension battery ignition, 
 increasing the number of cells in a series-connected battery very 
 materially increases the current that flows through the primary 
 winding of the induction coil. The volume or hotness of the 
 spark is also very materially increased as long as the magnetic 
 core of the induction coil is not nearly or completely saturated. 
 (Saturated = magnetized to its full capacity.) 
 
 In multiple battery connection all the carbons are connected 
 together, as by a single wire, and all the zincs are similarly con- 
 nected together. The two wires are the terminals of the battery. 
 The voltage of the battery is the same as that of a single cell, 
 when all the cells are of equal electromotive force. The current 
 
IGNITION 
 
 that the battery will give is but slightly more than that of a single 
 cell when the external resistance is very high in proportion to the 
 internal resistance of a cell. But when the resistance of the exter- 
 nal circuit is very small in comparison with that of a cell, the 
 current will be nearly proportional to the number of cells. 
 
 ) Terminal 
 
 minal 
 
 FIG. 46. 
 
 Battery of Multiple or Parallel-Connected Cells. 
 i volts per cell; also ij volts between (-}-) and ( ). 
 
 The facts just pointed out goto show that if one cell is sending an 
 electric current through a circuit, and it is desired to increase the 
 current to the greatest value possible by the addition of another 
 cell, they should be connected in series (carbon to zinc) if the 
 external resistance of the circuit is large; but if it is small, they 
 should be connected in multiple (zinc to zinc and carbon to car- 
 bon). The inductive resistance is to be included in the external 
 resistance of the circuit. It is assumed that the cells are exactly 
 alike. 
 
 FIG. 47. 
 
 Two Sets of Four Series-Connected Cells in Multiple or Parallel, 
 ij volts per cell. 5 volts between (+) and ( ). 
 
 49. Multiple-Series Batteries. A group of series-connected 
 cells can be considered as one of the units of which a battery is 
 made up. In determining the pressure and current capacity of a 
 
88 
 
 THE GAS ENGINE 
 
 battery of such units, the work may be facilitated by imagining 
 each series-connected group to be a single cell whose carbon and 
 zinc correspond to the terminals of the group. The electro- 
 motive force of this imaginary cell is the same as that of the series. 
 The effects on pressure and current obtained by connecting these 
 groups either in series or multiple are similar to those already 
 pointed out for series and multiple arrangement of single cells. 
 
 Thus, if five cells connected in series is the unit, whose electro- 
 motive force is 6^ volts, then putting two of these units in series 
 with each other will give 2 X 6J = 12 J volts; or putting the two 
 units in multiple will leave the pressure 6J volts as before. And 
 as for single cells, any number of the series-connected units 
 when connected in multiple do not increase the pressure. 
 
 50. Arrangement of Batteries for Ignition. It is advisable 
 to have the batteries in duplicate for ignition purposes. Only 
 one battery is used at a time. This leaves a reserve to be called 
 on in case the one in use at the moment fails. If both batteries 
 
 Switch Open 
 
 FIG. 48. 
 
 Incorrect Wiring for Two Batteries in Parallel. 
 
 Current flows as indicated by the arrows when the switch is open and exhausts the 
 upper row of six cells. Current also flows in the same manner when the circuit 
 is not closed by the timer of the ignition system. 
 
 become too weak to supply enough current when either is used 
 alone, they can both be used together. Simple and inexpensive 
 switches for throwing either one or both batteries on are found 
 in numerous designs. Such switches connect the two batteries 
 
IGNITION 
 
 89 
 
 in multiple when both are used at the same instant. The two 
 batteries when thus connected really form a single multiple-series 
 battery. 
 
 In jump-spark electric ignition for motors the resistance of 
 the circuit that is external to the battery is generally of such an 
 amount that the following method of arranging the cells can be 
 used to advantage when there are originally two batteries. 
 
 After both batteries have become too weak to give sufficient 
 current when used individually, they can first be connected in 
 multiple, as already described, and used until still further weak- 
 ened to such an extent as to fail to supply the necessary energy. 
 
 Induction Coil 
 
 Switch Open 
 
 FIG. 49. 
 Correct Wiring for Two Batteries in Parallel. 
 
 No current flows when the switch is open. The switch when in mid-position puts 
 the two batteries in parallel. 
 
 The two original batteries can then be connected in series and 
 they will then generally give enough current for a while. Some- 
 times it is advisable not to change directly from multiple to series 
 connection of all the cells, but instead to put only part of the 
 cells of one battery in series with all those of the other and 
 then add the remaining cells in series as they are needed. 
 
 When dry cells are used for low-tension arc ignition a gain of 
 current can be obtained by putting two batteries in multiple 
 after they have each run down so that neither alone will give 
 enough current. There is no further gain by putting them in 
 
90 THE GAS ENGINE 
 
 series, however, when the external resistance of the circuit is as 
 low as in the usual practice for arc ignition. 
 
 51. Recuperation of Dry Cells. Most carbon-zinc dry cells 
 can be temporarily recuperated by making a hole in each and 
 putting in a solution of sal ammoniac in water, or by putting in 
 water alone. The rejuvenation thus secured is generally of short 
 duration, however. 
 
 52. Storage Batteries, also called Accumulators and Second- 
 ary Batteries. The storage battery for ignition purposes is 
 ordinarily made up of two or three storage cells, all placed 
 together in a single case, or in a large cell, so that the battery is 
 a compact and inseparable unit in itself, which in many designs 
 has but two external binding posts or terminals. In others 
 the terminals of each cell are brought outside of the case and 
 connected together to form the battery. Two of the cell termi- 
 nals are left free, of course, to form the battery terminals. 
 
 The storage cells are made up of positive and negative plates. 
 In one type the plates are of lead with numerous perforations 
 or pockets which are filled with oxide of lead in the form of 
 paste. Several of these plates, or grids, are connected to form 
 the positive side of the cell, and another set for the negative 
 side. The positive and negative grids are interposed between 
 each other, and the intervening spaces are filled with a liquid 
 electrolyte of dilute sulphuric acid. 
 
 When first made up the cell has no electric life, but must be 
 charged by passing a current of electricity through it. When 
 charged, the terminal of one set of plates becomes electro- 
 positive and that of the other set electro-negative. When the 
 cells are recharged, it must always be done so that each set of 
 plates retains its initial polarity. The terminals of the battery 
 are therefore marked in some manner to indicate which is posi- 
 tive and which negative. In ignition storage batteries the 
 terminals are usually marked (+) and ( ) to indicate positive 
 and negative respectively. 
 
 The charging of the storage battery can be done from any 
 source that will furnish direct current (not alternating) of suffi- 
 cient pressure. The pressure of the charging current must be 
 
IGNITION 91 
 
 higher than that of the battery when it is fully charged. The 
 current must not be allowed to exceed a certain maximum am- 
 perage that depends on the area of the surface of the grids. 
 There are generally instructions with the battery which give 
 the maximum allowable current for charging. The charging 
 process is one of chemical change in the lead oxide. If done 
 too rapidly, gases are formed too rapidly and the paste loosened 
 in the pockets. 
 
 Before connecting the charging wires to the terminals of the 
 battery, it is necessary to know which of the wires is positive 
 and which negative, so that they can be connected accordingly. 
 A very simple and convenient method of determining the polarity 
 of the charging wires is to immerse their ends in water. Bubbles 
 of gas will form on the immersed surface of the negative ( ) 
 wire more rapidly than on the positive (+ ). The wire on which 
 the greater formation of bubbles occurs should be connected to 
 the negative terminal of the storage battery, and the other wire 
 to the positive terminal of the battery. 
 
 In testing for the positive and negative wires it is advisable 
 to keep their ends well apart when they are first immersed in the 
 water, and then bring them toward each other gradually till the 
 bubbles show distinctly. An excessive flow of current will thus 
 be prevented in cases where it would occur with the wire ends 
 close together. Impure or slightly acidulated water will give 
 bubbles more readily than pure water, on account of the lower 
 electrical resistance of the former. In case the memory fails 
 as to the pole at which the bubbles form most rapidly, wires can 
 also be connected to the terminals of the storage battery to be 
 charged and their free ends immersed in water. The formation 
 of bubbles should be noted as for the charging wires. The 
 two wire ends that give most bubbles in the two cases should be 
 connected together for charging. Acidulated water is generally 
 required to bring out the bubbles with the voltage of the ignition 
 storage battery. 
 
 The case enclosing the ignition storage battery is tightly closed 
 when the battery is in use. But when charging, each cell is 
 opened to the atmosphere by the removal of a stopper to a hole 
 
92 THE GAS ENGINE 
 
 in the cell, or by other means. This is necessary to allow the gas 
 slowly formed during charging to escape. When the battery is 
 completely charged, the formation of the gases by the continu- 
 ance of the charging current is much more rapid than before. 
 Charging should be discontinued as soon as gases begin to form 
 rapidly. 
 
 Rectifiers for transforming alternating current into direct 
 current are used for charging storage batteries when the source 
 of electrical supply has an alternating current. 
 
 The electromotive force of the lead-grid storage cell is brought 
 up to about 2.5 volts while charging. It quickly drops a tenth 
 of a volt or so when it begins to discharge. When it has fallen 
 to 2.1 volts per cell the battery should not be used till charged 
 again. Three cells in series, giving an average of about 6.5 
 volts, are put together for the battery to be used in connection 
 with American induction coils, according to the usual practice. 
 
 Storage cells with other elements than lead and its compounds 
 are also in use for ignition purposes. In one, nickel and iron are 
 the metals used for the elements. Another, a foreign production, 
 is really a combination of a storage cell and a primary cell. It is 
 charged by passing a current through it in the usual manner for 
 a storage cell. But in order to obtain current from it a piece of 
 metal, or alloy, is dropped into it. Current is then given out 
 as in the ordinary case of a storage cell. This continues as long 
 as any of the piece of metal dropped in remains. But as soon as 
 the metal is consumed the cell becomes dead till more metal is 
 dropped in. This makes it active again as long as the metal 
 lasts. The number of pieces of metal that have been used in a 
 battery after it has been fully charged is an index of its degree 
 of discharge. The pieces of metal to be dropped in are made of 
 uniform size. When a certain number have been used the cell 
 must be recharged. 
 
 The electrical resistance of storage cells for ignition is much 
 lower than that of dry cells, but not so low as that of the larger 
 storage cells intended for power and lighting purposes where a 
 vastly larger current is required. The ignition storage battery 
 is, therefore, not so seriously injured by short-circuiting as are 
 
IGNITION 93 
 
 the larger ones, but is exhausted with great rapfidity when the 
 terminals are connected through a circuit of very low resistance. 
 
 53. Comparison of Dry Cells and Storage Batteries for Ignition 
 Purposes. The storage battery has a greater capacity than a 
 battery of dry cells of equal bulk. It also provides a more 
 uniform voltage. On account of these properties it is far more 
 desirable than dry cells. The two features not so desirable are 
 the necessity of recharging and the comparatively high cost of the 
 storage battery. When used in connection with a generator that 
 supplies it with current while both are connected in the working 
 position with the motor, the objection to the necessity of recharg- 
 ing disappears. 
 
 Many makes of dry cells are notably unreliable in action. 
 They sometimes have practically no energy in them when first 
 put in place. This deficiency may be due either to an originally 
 poor cell or to one that has been kept too long before putting it 
 into use. It is believed that nothing more than care in selecting 
 materials and in construction is necessary to produce a good, 
 durable dry cell. When carelessly packed, the terminals of two 
 cells may come together so as to make a short circuit and exhaust 
 them both. 
 
 54. Testing Electric Batteries. The test for the condition 
 of a storage battery with regard to its capacity to deliver current 
 is made by measuring the voltage. It will be remembered that 
 the voltage drops as the battery is discharged. Since the drop is 
 slight from the highest to the lowest working limits, a voltmeter 
 reading to small fractions of a volt (milli-voltmeter) between 
 these limits is necessary. A storage battery may be very much 
 out of repair and still show a satisfactory pressure. In some 
 cases of this kind a test of the current will disclose that it is 
 faulty. The test for current can be made with an ammeter 
 in a circuit that has from terminal to terminal of the battery 
 about the same resistance as that on which the latter is intended 
 to work. This is readily done by cutting the ammeter into the 
 regular circuit. The current will decrease rapidly if the bat- 
 tery is seriously faulty. 
 
 The ammeter is sometimes applied directly to the terminals of 
 
94 THE GAS ENGINE 
 
 the battery. This, if done at all, should be for only a small 
 fraction of a second. The ammeter has a very low resistance, 
 and applying it to the terminals without any other resistance in 
 the circuit practically amounts to short-circuiting the battery. 
 The only method of doing this that is at all safe for the battery 
 is to connect one terminal of the ammeter to a terminal of the 
 battery and then strike the other battery terminal a glancing 
 blow with the free ammeter terminal. The kick of the ammeter 
 needle is to be observed. The circuit should not be closed long 
 enough for even a dead-beat needle to come to rest. This does 
 not refer to storage batteries other than those constructed for 
 ignition purposes. 
 
 Dry cells and dry batteries can be tested in the same man- 
 ner as that just given for storage cells. The dry cell will not 
 generally be so much injured by short-circuiting through the 
 ammeter as the storage cell, but still it is never advisable to 
 hold the instrument in contact with the terminals more than a 
 second or two when there is a strong current. If the current 
 is weak, the cell is poor and past injury in this manner. 
 Tests of dry cells cannot be greatly relied on, however, for one 
 that shows full voltage and a strong current after standing idle 
 will not infrequently fail in a short time. 
 
 55. Wiring Scheme for Single-Acting, Single-Cylinder Motor 
 with Jump-Spark Ignition. A wire from one terminal of the 
 battery connects to the induction coil at the binding post that 
 forms part of, or is directly connected to, one side of the inter- 
 rupter. A wire from the insulated stationary contact piece of 
 the timer is connected to the induction coil at the intermediate 
 binding post where one end of the primary and one end of the 
 secondary coil terminate. The remaining terminal of the 
 battery is "grounded" by connecting it to the metal of the motor 
 or any part of the metal frame on which the motor rests. If 
 the rotor of the timer is electrically insulated from the shaft to 
 which it is mechanically attached, and thus from the frame of 
 the motor, then a wire connects the insulated ground ring of 
 the rotor to the metal of the motor or its supporting frame, or 
 a slip ring and brush are used for the same or a similar purpose. 
 
IGNITION 
 
 95 
 
 When the timer rotor is not insulated from the shaft, no special 
 electric connection is used. This completes the wiring of the 
 battery circuit. 
 
 When the timer closes the circuit, current passes from the 
 battery to the interrupter, then through the primary winding 
 and on through the timer to the metal of the motor or of the 
 frame that supports the motor, and thence to the ground wire 
 
 Battery 
 
 Spark Plug >q fj 
 
 Cylinder 
 
 Timer Frame 
 
 FIG. 50. 
 
 Ignition System for Single-Cylinder Motor. One Battery. 
 Heavy black indicates frame or "ground" connection. 
 
 of the battery and through the ground wire back to the battery 
 itself. A switch for opening and closing the primary circuit 
 at will is placed somewhere in the circuit, generally between the 
 battery and the induction coil. 
 
 Only one additional wire is required for the high-tension or 
 spark-plug circuit. It connects the remaining terminal of the 
 induction coil to the insulated part of the spark plug. The 
 high-tension current passes along this wire from the induction 
 coil to the spark plug, jumps across the spark gap to the metal 
 of the motor, and then passes back to the induction coil by way 
 of the timer and the wire connecting the timer to the terminal 
 to which an end of each of the windings of the induction coil is 
 attached. 
 
 It will be seen from the above that both the primary and 
 secondary currents pass through the wire connecting the timer 
 to the induction coil. This wire does not need heavy insulation, 
 however, for the high-tension current passes through it only 
 when the circuit is closed by the timer, thus making the potential 
 
96 THE GAS ENGINE 
 
 of the wire practically the same as that of the motor. The insula- 
 tion on the wire between the timer and induction coil needs to 
 be only sufficient to prevent, when the timer is not closed, the 
 primary current from passing between the wire and the motor 
 or parts electrically connected to the motor. 
 
 While the method of wiring just given is the best, no serious 
 injury is done if the timer wire is connected to the interrupter 
 end of the primary coil. With this connection, however, the 
 secondary current must either jump the open gap at the inter- 
 rupter contacts immediately after the circuit is broken there, 
 or pass from the motor frame back through the battery to the 
 induction coil. There is "apt to be more sparking at the inter- 
 rupter with such connections than when they are made as first 
 given. 
 
 A properly constructed induction coil is not injured by con- 
 necting the battery wires to the wrong terminals. When there 
 is no way of determining, by an examination of the induction 
 coil, how the connections should be made to it, it can be tested 
 with perfect safety by connecting the battery wires to it till the 
 interrupter vibrates, provided the interrupter is so adjusted that 
 it will not allow a large current to flow through the coil without 
 interrupting it. The current from a battery of the right capacity 
 will do no harm unless it is allowed to flow for considerable 
 time without interruption. 
 
 In testing for induction-coil connections, the vibrator spring 
 should be set so that it presses the contact points together very 
 lightly. 
 
 The substitution of a low-tension direct-current electric gen- 
 erator of constant voltage for the battery does not alter the wiring 
 scheme. It is not usual, however, to find an electric generator 
 used in connection with a current interrupter on the induction 
 coil. 
 
 56. Wiring Scheme for Motor with More than One Combustion 
 Chamber, Jump-Spark Ignition, and One Induction Coil for Each 
 Combustion Chamber. This differs from the wiring for a 
 single combustion chamber, as just given, in the multiplication 
 of the spark plugs, induction coils, number of contact points on 
 
IGNITION 
 
 97 
 
 the timer, and the number of wires connecting the induction coils 
 to the timer and spark plugs. 
 
 A wire is led from one of the battery terminals to one of the 
 terminals of a switch at the induction coils, which are grouped 
 together, all of them generally being placed in one box. Each 
 induction coil is complete in itself, including the interrupter. 
 
 Battery A 
 
 Switch open. 
 
 When the Switch is in Mid 
 Position the Batteries are 
 in Multiple. 
 
 mm 
 
 FIG. 61. 
 
 Ignition System for Four-Cylinder Motor. Two Batteries. 
 Heavy black indicates frame or "ground" connection. 
 
 When the switch is closed, one of the battery wires is electrically 
 connected to the interrupter ends of all the induction coils. The 
 timer has as many stationary contact points as there are spark 
 plugs to be operated. There are as many wires between the 
 timer and the group of induction coils as there are induction coils. 
 Each induction coil has its own contact point at the timer, and is 
 
98 THE GAS ENGINE 
 
 connected to the latter by a wire leading from the inter- 
 mediate binding post of the coil. Each spark plug is connected 
 to the remaining binding post of its own induction coil. The 
 rotor of the timer and the remaining terminal of the battery 
 are grounded to the metal of the motor as for a single-cylinder 
 motor. 
 
 The timer, by its rotation, closes the primary circuit through 
 each induction coil consecutively in the proper order and at about 
 the instant the spark is to pass in the corresponding combustion 
 chamber. 
 
 If the explosions are to occur with equal intervals of time 
 between them, then the stationary contacts of the timer are 
 placed at equal distances apart around the path traveled by the 
 rotor's contact point. But if, as is the case of a double-acting, 
 single-cylinder, four-cycle motor, the explosions occur first at 
 one-half a revolution of the crank shaft apart, and then not until 
 one and a half revolutions more have been made, then after 
 another half revolution, and so on, the two stationary contacts of 
 the timer must be placed at one-quarter of the circumference 
 apart. 
 
 The low-tension direct-current generator can be used instead 
 of the battery, but its application for this purpose is not 
 common. 
 
 57. Jump-Spark Ignition with High-Tension Distributer and 
 Battery Current. In this system of ignition the timer and 
 induction coils are replaced by a single piece of apparatus com- 
 posed of one induction coil, a timer, and a distributer for directing 
 the high-tension current to the proper spark plug. 
 
 The timer closes the battery circuit through the interrupter 
 and the primary winding of the coil whenever a spark is wanted 
 at any of the spark plugs. Since there is only one induction coil, 
 a means of directing the high-tension current to where it is needed 
 becomes necessary. 
 
 The distributer generally consists of an arm of some sort that 
 is attached to and rotates with the same shaft that carries the 
 timer rotor. As the distributer arm swings around it comes 
 consecutively opposite the terminals to which the wires that lead 
 
IGNITION 99 
 
 out to the insulated parts of the different spark plugs are con- 
 nected. The distributer has always come opposite one of these 
 terminals when the timer closes the primary circuit. 
 
 In addition to the spark gap in the combustion chamber, the 
 high-tension current must jump another small gap between the 
 distributer arm and the terminal next to it. 
 
 By this condensing of the apparatus the wiring system is 
 simplified to some extent. The wires necessary are: one wire 
 from the battery to the induction coil; one from each of the spark 
 plugs to the induction coil ; and one from the battery to the metal 
 of the motor, or to " ground. " If the rotor of the timer is insulated 
 from the metal of the motor, then another wire for grounding the 
 rotor, or its ground-ring, is necessary. 
 
 58. Comparison of Multi-Induction-Coil and High-Tension- 
 Distributer Ignition Systems. The high-tension distribution 
 system has the advantage of the absence of external wires between 
 the timer and the induction coil and of more compact apparatus. 
 It has the disadvantage of depending entirely on one induction 
 coil for the current to all the spark plugs. In a four-cylinder 
 motor the service is so arduous that the contact points of the 
 interrupter become very warm, and fusing and oxidation are of 
 frequent occurrence. It is not unusual for makers to construct 
 the case for enclosing the apparatus with space for carrying an 
 extra induction coil, and to supply the extra coil as a part of the 
 apparatus. 
 
 When an individual induction coil is used for each spark plug, 
 the failure of one coil to work does not necessarily stop the 
 motor, for it can be run on the remaining coils and their corre- 
 sponding motor cylinders and combustion chambers. A test can 
 also be easily made to locate a faulty spark plug or a cylinder that 
 is not acting properly, by holding down one or more of the 
 vibrators and thus cutting out some of the spark plugs, at the 
 same time noting the action of those left in operation. This 
 cannot be done with the single induction coil combined with a 
 high-tension distributer. The high-tension wires can be dis- 
 connected or short-circuited in either system, however, for 
 locating a faulty plug or cylinder. This is far less convenient, 
 
100 THE GAS ENGINE 
 
 and sometimes decidedly uncomfortable on account of the elec- 
 tric shock that may be received. 
 
 59. Jump-Spark Ignition in Two Cylinders with One Induction 
 Coil and No Distributer. In a two-cylinder, four-cycle, single- 
 acting motor whose time interval between explosions is of uniform 
 length (one revolution of the crank shaft apart) one induction 
 coil can be used for ignition in both combustion chambers. 
 The coil most suitable for this purpose has four terminal binding 
 posts instead of three. This is the usual construction of the 
 induction coil for general uses. Each wire end of the two wind- 
 ings is terminated in a binding post of its own, which gives the 
 four binding posts or terminals. 
 
 The battery circuit is run as for a single spark plug, but the 
 timer must either turn at the same speed as the crank shaft 
 or have two stationary contacts at diametrically opposite points, 
 and also have these two contacts electrically connected together 
 so that the battery circuit is closed once every revolution of the 
 crank shaft. The high-tension circuit has a wire from each of 
 the two spark plugs to the corresponding terminal of the second- 
 ary winding of the induction coil. The path of the secondary 
 current is from one terminal of the coil to the insulated part of 
 the spark plug, when plugs having only one side of the spark 
 gap insulated are used, then across the spark gap of the plug to 
 the metal of the motor and thence to the threaded bushing of the 
 other plug, then across its spark gap to its insulated part and 
 back to the other binding post of the secondary winding of the in- 
 duction coil. Spark plugs having both sides of the spark gap insu- 
 lated from the motor metal require an additional wire between the 
 plugs, or each must have one side grounded to the motor metal. 
 
 The spark is made in both cylinders simultaneously and twice 
 as often as it is needed. It comes at about the beginning of the 
 impulse stroke and at the corresponding time in the exhaust 
 stroke or suction stroke, or between the last two. When the 
 motor is operating properly there is nothing but inert gases in 
 the cylinder whose piston is about beginning the suction stroke 
 at the instant the spark passes in it, hence the spark in that 
 cylinder produces no result. 
 
IGNITION .101 
 
 But if a charge fails to ignite at the proper .time there will 
 be some of the combustible mixture still remaining in the cylin- 
 der when the spark passes at about the beginning of the suction 
 stroke, and it may be ignited. The result generally is that it is 
 still burning when the new charge begins to enter, and the latter 
 is fired back into the inlet pipe and carbureter. This does no 
 damage generally, but the motor does not get another charge 
 of combustible mixture until after a stroke or two of the piston 
 has been made to clear out the inert gases from the inlet pipes, 
 and there is consequently loss of power. 
 
 This back firing into the carbureter occurs frequently when 
 starting a motor by cranking, either on account of the failure to 
 fire a charge at the proper time or by the incoming charge 
 striking the spark plug at the instant the spark jumps. 
 
 This system of ignition can be extended to any even number of 
 spark plugs by using one induction coil for each pair of plugs 
 whose charges are to be fired one revolution apart. 
 
 The use of this system is decreasing. It has the objectionable 
 features of depending on only one coil for two cylinders and the 
 absence of a ready method of locating a defective spark plug or 
 a cylinder that is not giving its full power. 
 
 60. Magneto Generators for Jump-Spark Ignition. The 
 primary current for jump-spark (high-tension) ignition is very 
 often furnished by a magneto generator. Both the rotary- 
 armature and the oscillating-armature types are used. The 
 rotary type generates an alternating current. There are two 
 forms of the apparatus found in general practice. 
 
 The armature of the magneto is usually of the simple shuttle- 
 wound type with the customary I-shaped cross-section of armature 
 core. In the better machines the armature core is built up of nu- 
 merous thin stampings from sheets of soft iron or mild steel. The 
 I-shaped stampings are placed side by side to build up the core. 
 
 The magneto is a separate piece of apparatus in one system 
 of ignition. The low-tension current from the magneto is taken 
 to a transformer for changing it into high-tension current for the 
 spark-plug circuit. The transformer is an induction coil without 
 an interrupter (trembler, vibrator). 
 
102 
 
 THE GAS ENGINE 
 
 In another system both the magneto and the induction coil, or 
 transformer, are embodied in a single piece of apparatus, which 
 is commonly called a "high-tension magneto." 
 
 61. Low-Tension Magneto and Separate Transformer System 
 of Jump-Spark Ignition. A magneto with either a rotary 
 armature or an oscillating armature can be used in this system. 
 
 Circuit Breaker 
 
 | Contact Point 
 
 Condenser 
 
 FIG. 52. 
 
 Magneto and Transformer for Jump-Spark Ignition. Interrupted Armature Current. 
 
 The cam is either placed on the armature shaft or driven at the same speed as the 
 armature. The cam lifts the circuit breaker and breaks the armature circuit at 
 the contact points when the current has reached about its maximum value. The 
 sudden drop of current thus caused in the primary winding of the transformer 
 induces a pressure in the secondary winding of sufficient intensity to make a spark 
 at the ignition points of the spark plug. 
 
 The condenser has the same function as in an induction coil with a vibrator for 
 interrupting the primary current. 
 
 The figure is an entirely diagrammatic representation of the system. A cylindrical 
 timer with non-conducting segments for interrupting the current is generally 
 used instead of a circuit breaker of the nature shown. 
 
IGNITION 
 
 103 
 
 When a rotary armature is used, the more uual practice is 
 to drive it at a high speed, and use a timer for closing the primary 
 circuit through the transformer at the instant an ignition is 
 wanted. The rapidly alternating current from the magneto 
 passes through the primary (low-tension) coil of the transformer 
 and induces a high-tension current in the secondary winding 
 which connects to the spark plug. A series of sparks pass 
 at the plug each time the primary circuit is closed by the 
 timer. 
 
 FIG. -53. 
 
 Magneto with Separate Transformer for Jump-Spark Ignition. Shunted or 
 Short-Circuited Primary Current. 
 
 The armature current is short-circuited through the contact points till it has reached 
 about its maximum. The circuit breaker is then opened and the consequent 
 sudden increase of current in the primary of the transformer causes a spark at 
 the spark plug. Immediate closing of the circuit breaker will induce another 
 spark at the plug on account of sudden decrease of current in the primary of the 
 transformer. 
 
104 THE GAS ENGINE 
 
 With this arrangement the armature can be driven by a belt, 
 friction gears, or friction clutch, for it is not necessary that the 
 speed of the armature shall bear a constant ratio to that of the 
 crank shaft of the motor. 
 
 If a speed-limiting device is used in connection with the 
 friction gears or clutch, then the armature can be given a high 
 speed ratio in relation to the crank shaft, so that rotating the 
 motor shaft slowly, as when cranking a small motor by hand, 
 will generate current of sufficient volume and frequency to 
 induce a spark in the combustion chamber. The speed-limit- 
 ing device prevents the speed of the armature from becoming 
 excessive when the motor rotates rapidly. 
 
 Some rotary magnetos for this system are so constructed that 
 they can be connected by a positive drive to the motor crank 
 shaft so as to have a constant speed ratio to the latter. The 
 armature is wound so that it will give enough current to produce 
 the ignition spark when the motor is cranked rapidly by hand, 
 and will not be injured or deliver too much current or voltage to 
 the transformer when the motor runs fast. 
 
 The oscillating-armature magneto always gives the same 
 current and voltage, whatever the speed of the motor. A timer 
 is not necessary in connection with it, but is often used. When 
 the timer is used the transformer generally has a condenser. 
 The oscillating magneto gives only one spark for each ignition. 
 Its armature is moved partly around at a comparatively low rate 
 against the resistance of a spring, and then allowed to snap back 
 to generate the current for the spark at the plug. Or, in other 
 designs, the armature is held stationary while the part to which 
 the spring is attached rocks over, and then the armature is 
 released and follows with a snap, first in one direction and then 
 in the other. The oscillating magneto is used successfully on very 
 high speed motors, such as those on motor cycles. In a four- 
 cylinder, four-cycle, single-acting motor having only one mag- 
 neto, the armature must snap over twice for every revolution of 
 the crank shaft. This has been accomplished on the motor cycle. 
 
 62. " High-Tension Magneto." This is the commercial 
 name for a piece of apparatus which delivers high-tension current 
 
IGNITION 
 
 105 
 
 to the spark plug in jump-spark ignition when its armature is 
 rotated at the requisite speed, or oscillated. It is really the 
 embodiment, in one apparatus, of a magneto electric generator, 
 a condenser, a transformer, a timer, and a high-tension current 
 distributer. The latter is needed only when the motor has more 
 than one combustion chamber. 
 
 In one type, designed for a four-cylinder, single-acting four- 
 cycle motor, or for a two-cylinder, double-acting motor, the 
 
 
 FIG. 54. 
 
 Magneto without Separate Transformer for Jump-Spark Ignition. 
 Magneto Armature used on Transformer. Interrupted Primary Current. 
 The secondary coil is wound on the armature core of the magneto outside of the 
 primary coil. The primary current is interrupted by the circuit breaker when 
 at about its maximum value. The sudden drop of current in the primary coil of 
 the armature, together with the action of the magnetic field, induces pressure 
 in the secondary coil great enough to produce a spark at the spark plug. The 
 condenser may be embodied in the magneto, thus forming a " high-tension 
 magneto." 
 
106 THE GAS ENGINE 
 
 shuttle-wound armature is driven at the same speed of rotation 
 as the crank shaft of the motor. The armature delivers low- 
 tension current to a condenser of the usual tin-foil construction; 
 a timer closes the circuit between the condenser and the primary 
 winding of the transformer at the time the condenser is fully 
 charged, which corresponds to the instant the spark is required 
 for ignition. One end of the secondary winding of the trans- 
 former is connected to a rotating high-tension current distributer 
 arm that comes, at the proper instant, opposite the terminal of 
 a wire leading to the spark plug where the spark is wanted. 
 The other terminal of the secondary .winding is grounded to the 
 metal of the motor. The high-tension current jumps both the 
 slight gap at the distributer arm and that at the spark plug at 
 the same instant. The rotation of the distributer arm brings it 
 in turn opposite the end of each wire that leads to a spark plug, 
 so that a spark is produced in each combustion chamber as 
 desired. 
 
 The apparatus resembles an ordinary magneto in general 
 appearance. It can be constructed for any number of cylinders, 
 and the speed or rotation of its armature and distributer arm 
 varied accordingly in relation to the crank shaft. 
 
 When an oscillating armature is used the timer can be 
 dispensed with, especially if the speed of the motor is not 
 high. When there is no timer the condenser can also be 
 eliminated. 
 
 An induction coil with an interrupted magnetic circuit and 
 a single winding of many turns of wire can be used for pro- 
 ducing high-tension current for the spark plug. The coil can 
 be used with or without a timer and condenser. Without the 
 condenser it differs from the similar induction coil already 
 described for low-tension ignition only in having a greater 
 number of turns in the winding. 
 
 63. Dynamo -Battery Ignition and Lighting System. Storage 
 battery "floated on the line." Direct-current shunt-wound 
 dynamo. Fig. 55 illustrates a method of using a dynamo and 
 storage battery simultaneously for supplying current for ignition 
 purposes, and for small lights also when desired. The scheme 
 
IGNITION 
 
 107 
 
 is a simplification, to some extent, of the same method as applied 
 to power and lighting purposes on a large scale. 
 
 The voltage of the system is determined by the battery within 
 slight variations. 
 
 When the voltage of the dynamo is higher than that of the 
 battery, the direction of flow of current is as indicated by the full 
 arrows. The current from the lower ( + ) brush of the dynamo 
 divides, most of it flowing out through the lower line. The other 
 (very small) portion of the current flows first through the field 
 
 & 
 
 32 C 
 
 I 
 
 Two-way Switch 
 
 : 
 
 t Hinge, 
 
 ^Series Coil 
 
 
 J-ShuntCoU 
 11 1 
 
 
 Induction Spring^ 
 
 Coil * WvVWv- 
 
 o 
 
 
 
 . / 
 
 1 | == g Cutout- 
 
 II /yyy MWW) 
 Cutout for 
 
 ^ ic3 c 
 II* 
 
 ^=> ( 
 
 V 
 
 f a Contact Poir 
 
 
 
 FIG. 55. 
 Dynamo-Battery Ignition and Lighting System. Battery " floated on the line." 
 
 coil of the generator and then through the thin-wire coil of the 
 armature cut-out and back to the dynamo. The main part of 
 the current, in the lower line, divides and the different portions 
 flow through the storage battery and lamps, each portion in its 
 own course. The induction-coil circuit is shown open, and will 
 not be considered at present. 
 
 The current returning along the upper line passes down through 
 the armature of the dynamo cut-out, through the contact points 
 and around the series coil of the cut-out, then back to the dynamo. 
 The currents in both coils on the cut-out act in unison to draw 
 the armature of the cut-out toward the core of the magnet 
 and thus to keep the contact points together. The current 
 flowing through the battery as indicated by the full arrows 
 charges it. 
 
 If the dynamo furnishes between the junction points, E and 
 F, of the battery wires with the main lines a voltage that is just 
 equal to the voltage of the battery, then no current will flow 
 through the battery, but all the current delivered by the dynamo 
 
io8 
 
 THE GAS ENGINE 
 
IGNITION 
 
 109 
 
no THE GAS ENGINE 
 
 to the lower main line will pass through the lights (induction- 
 coil circuit open). 
 
 When the pressure between E and F falls slightly below that 
 of the battery terminals, but with the pressure at the dynamo 
 still higher than that of the battery, which condition may 
 occur on account of the resistance of the circuit from E 
 through the dynamo to F, then current will flow from the 
 battery, as indicated by the broken arrow, and through the 
 lamps, as well as from the dynamo through the lamps. 
 The battery thus aids the dynamo. 
 
 If the pressure of the dynamo falls below that of the battery, 
 or more correctly, below that between E and F, then current will 
 flow from the battery to E, divide there and pass in parallel 
 through the dynamo and the lamps back to the battery. The 
 current flowing back through the dynamo circuit in this manner 
 acts in opposition to the shunt coil of the automatic cut-out. 
 Before this back-flowing current becomes great enough to injure 
 the dynamo, it weakens the cut-out magnet to such an extent that 
 the spring draws the cut-out armature away from the magnet and 
 separates the contact points, thus breaking the circuit that leads 
 through the dynamo and battery. The battery continues to 
 supply current to the lamps. 
 
 By now increasing the voltage of the dynamo, as by speeding 
 it up, the current through the field coil of the generator and the 
 shunt coil of the cut-out can be increased to magnetize the core 
 of the cut-out enough to draw its armature in and again bring 
 the contacts together to close the dynamo circuit. This is the 
 same process as when starting the dynamo from rest. 
 
 The induction coil is connected to the middle of the battery, 
 so that only half of the total voltage acts on it when its two-way 
 switch is closed on either contact. If the dynamo circuit is open 
 and the two-way switch is closed on the lower contact, then the 
 lower half of the battery furnishes current to the induction coil; 
 if the switch is closed on the upper contact, the upper half of the 
 battery furnishes the current to the induction coil. If with the 
 latter position of the switch the dynamo is put on-with enough 
 pressure to send current through the battery, the current 
 
IGNITION 
 
 III 
 
 from E will pass up to the middle of the batfery and divide 
 there, so that part will pass to the upper line through the 
 induction coil and part to the same line through the upper 
 part of the battery. 
 
 Small dynamos for this method of ignition are made with the 
 automatic cut-out as a part of the dynamo. When intended to 
 
 N9 5-S-SWITCHBOARD 
 
 WE PROVIDE FOR 
 EITHER BELT, FRICTION 
 OR GEAR DRIVE. 
 
 READ HERE 
 VOLTAGE OF BATTERY, 
 AMPERE DISCHARGE, 
 AMPERE CHARGE. 
 
 -ONE SWITCH 
 ^CONTROLS IGNITION AND 
 VOLT AMPEREMETER 
 
 CONNECT THESE WIRES FROM 
 
 =^ 
 ATTERY) 
 
 TO COIL & ENGINE THE SAME AS IF FROM ABATTERY. 
 
 BATTERY FLOATING 
 ON LINE AND ACTING 
 AS RESERVOIR. 
 
 AUTOMATIC 
 IGNITION DYNAMO 
 WITH AUTOMATIC CUT-OUT V 
 
 FIG. 58. Dynamo-Battery Ignition System. Apple Electric Company, 
 Dayton, Ohio. 
 
 operate in connection with a variable-speed motor, a governor is 
 used on the dynamo shaft to limit its speed to that which gives 
 sufficient voltage to charge the battery. 
 
 With suitably constructed batteries and a kick-coil in the 
 ignition circuit, the above method of supplying current can be 
 used for low-tension arc (make-and-break) ignition.* 
 
 : There are several other conditions and refinements which might be 
 considered in connection with this method of supplying current, but is 
 
112 THE GAS ENGINE 
 
 64. Hot-Tube Ignition. This method of ignition was exten- 
 sively used until recent years, and is still in some use on con- 
 stant-speed motors. 
 
 A tube of metal or some such material as porcelain or lava 
 is attached to the cylinder of the motor so that one end opens 
 into the combustion chamber; the outer end of the tube is perma- 
 nently closed. An external flame keeps the tube at a red heat. 
 When a charge is compressed into the combustion chamber 
 some of it is forced into the open end of the tube on account of 
 the diminution of volume of the inert gases contained in the tube 
 at the beginning of compression. The combustible mixture 
 thus forced into the tube is ignited by coming into contact with 
 the red-hot inner surface, and the sudden expansion of the gases 
 in the tube, due chiefly to combustion, projects a flame into the 
 body of the charge. The length of the tube is so proportioned, 
 and it is so heated, that ignition occurs at about the completion 
 of the compression stroke. The principal application of hot- 
 tube ignition is to motors running at constant or approximately 
 constant speed. 
 
 A timing valve was used in connection with the hot-tube 
 igniter in English practice. The valve closed the opening from 
 the combustion chamber into the tube until time for ignition. 
 The valve, of the poppet type, was then lifted from its seat and 
 some of the compressed charge in the combustion chamber 
 allowed to pass into the tube and become ignited. The timing 
 valve was lifted by the action of a cam or some corresponding 
 mechanism. With the timing valve, the hot tube can be used on 
 a variable-speed motor. 
 
 The tubes were made of various metals in their earlier appli- 
 
 believed that the cases considered will make the method clear enough for 
 the purpose at hand. 
 
 It may be noted, however, that there is no provision shown for auto- 
 matically cutting out the battery when it becomes fully charged, in order 
 to prevent its injury by overcharging. Such a device, common to all 
 larger work, is not generally considered necessary for gas-engine ignition 
 outfits. Fuses to prevent excessive current can of course ,be installed in 
 the usual manner. Automatic circuit breakers for opening by the action 
 of excessive current are hardly necessary above that shown. 
 
IGNITION 1 1 3 
 
 cation. Platinum and other precious metals .were tried, but 
 their cost was objectionable. The friable tubes of porcelain and 
 lava cracked, often without warning, and were therefore unsatis- 
 factory on account of stopping the motor when power was 
 needed. Nickel-steel hot tubes have finally proved the most 
 satisfactory for this method of ignition. They are not particu- 
 larly expensive, last well, and give ample warning when approach- 
 ing the age limit. 
 
 The objections to the hot tube are the open flame, the deteri- 
 oration of the tube, and, when the timing valve is used, the 
 difficulty of keeping it tight. When the timing valve is omitted 
 the ignition cannot always be brought about at just the instant 
 desired, especially if the motor is exposed to wind and cold. 
 Throttling the charge so as to reduce it in quantity also affects 
 the time of ignition, especially if there is no timing valve. 
 
 65. Hot-Metal Igniter Heated by Internal Combustion. - 
 This igniter for motors receiving a gaseous charge is, in one form, 
 a piece of steel resembling a short section of tube with a deeply 
 corrugated or ribbed interior. The corrugations are very deep, 
 and the open space between them is narrower near the center of 
 the tube than at a slight distance further out toward the circum- 
 ference. The igniter is heated by a flame before starting the 
 motor. The compression of the charge in the cylinder forces 
 some of the combustible mixture back into the tube and against 
 the hot metal, which ignites it. The heat of the combustion of 
 the gases thus ignited is sufficient to keep the igniter red hot. An 
 adjustment makes it possible to bring the mixture against the 
 igniter at the proper instant if the amount of the charge is 
 always the same so that the compression pressure is practically 
 constant. 
 
 In connection with this method of igniting may be men- 
 tioned the very simple expedient of having a piece of metal pro- 
 ject into the combustion chamber so as to become hot. After 
 becoming heated it serves as an igniter, but the time of ignition 
 cannot be well regulated with it. A bolt screwed into the piston 
 has been used in this manner. The overheating of a water- 
 cooled motor when its water circulation fails is another example. 
 
114 THE GAS ENGINE 
 
 66. Hot- Wire and Platinum-Sponge Igniters. Ignition by 
 means of a hot wire or a platinum sponge has been accomplished, 
 but neither method was found serviceable enough to warrant its 
 continuance. 
 
 In the hot-wire igniter, a short piece of very thin wire, generally 
 of platinum, was placed in the combustion chamber and heated 
 to incandescence momentarily by passing an electric current 
 through it at the time a charge was to be ignited. 
 
 The platinum-sponge method depends on the property, peculiar 
 to platinum, of becoming incandescent when placed in a current 
 of combustible gas. This property is called " catalysis." The 
 sponge, or a number of very thin platinum wires, was placed 
 inside the cylinder where the current of incoming gas would 
 strike it and quickly heat it to a temperature that would ignite 
 the charge. The fouling of the sponge was a serious objection 
 to its use. This method is analogous to igniting the gas escaping 
 from an ordinary illuminating jet by holding a platinum sponge 
 or a number of pieces of very thin platinum wire in the current 
 of the escaping gas. 
 
CHAPTER IV. 
 CONTROL OF POWER AND SPEED. 
 
 67. General Methods of Control. There are two fundamental 
 methods of controlling the power and speed of an internal-com- 
 bustion motor whose fuel enters the combustion chamber in the 
 form of gas or vapor, that find general application in general 
 engineering practice. They are : 
 
 Variation of the amount of fuel supplied; 
 Variation in the instant of ignition. 
 
 There are several other methods of regulating the speed and 
 power, but they are wasteful of fuel and otherwise undesirable in 
 comparison with the two methods just cited. 
 
 It may be said that control by variation of the instant of ignition 
 is also wasteful of fuel, and otherwise usually undesirable, yet, 
 under certain conditions in connection with the operation of 
 variable-speed motors, as those of automobiles, hoisting machin- 
 ery, and, to some extent, of boats, the control of speed by this 
 method is most convenient and desirable when used in connection 
 with variation in the rate of fuel supply. 
 
 68. Fuel Control. General. Variation in the amount of fuel 
 is accomplished by two distinct methods in motors using gas or 
 vapor fuel. 
 
 In one method the motor takes in either a complete charge, 
 or no charge at all, of the combustible mixture during the 
 normal charging period. This method is probably entirely 
 limited in practice to four-cycle stationary motors operating at 
 as nearly a constant speed as can be maintained, although it can 
 also be applied to two-cycle motors. 
 
 On account of the form and the method of operation of the 
 mechanism generally used to accomplish the cutting out of a 
 charge, it is commonly known as the " hit-or-miss " method. 
 
Il6 THE GAS ENGINE 
 
 The other method is to vary the amount of the charge while 
 always allowing enough mixture to enter the combustion cylinder 
 to ignite and produce an impulse. 
 
 69. Fuel Control in Four-Cycle Gas or Vapor Motor. Both 
 the intermittent cutting out of a charge, method and the reduction 
 in the amount of the charge method, cited in the preceding section, 
 find general application according to the conditions to be fulfilled. 
 
 The four customary ways of completely cutting out a charge, 
 all of them hit-or-miss methods, are : 
 
 1. Keeping the mixture inlet valve closed during the suction 
 
 stroke and also keeping the exhaust valve closed as usual; 
 
 2. Keeping the exhaust open and holding the inlet valve closed 
 
 during the suction stroke; 
 
 3. Leaving the exhaust closed during the regular exhaust period 
 
 so as to retain the inert products of combustion; 
 
 4. Keeping the gas valve closed while the mixture valve is kept 
 
 open to admit air during the suction stroke. 
 
 The three usual ways of diminishing the quantity of fuel in 
 a charge are: 
 
 A. Throttling the mixture; 
 
 B. Varying the length of time that the mixture inlet valve is kept 
 
 open; 
 
 C. Varying the length of time that the gas valve is kept open, but 
 
 opening and closing the mixture valve at fixed times. 
 
 By combinations of the above methods control for exceedingly 
 variable demands for power is accomplished by first diminishing 
 the quantity of fuel admitted for each charge till a certain con- 
 dition is reached, and then cutting out charges as by the hit-or- 
 miss method. 
 
 70. Governing and Hand Control. The power and speed 
 may be controlled either by a governor or by the hand of the 
 operator, according to the requirements. 
 
 The governor is used when the speed is to be kept as nearly 
 constant as possible with the degree of sensitiveness that the 
 apparatus can attain. 
 
CONTROL OF POWER AND SPEED 117 
 
 Hand control is used on variable-speed motors, as those for 
 automobiles, hoisting machines, launches, etc. It is generally 
 accomplished by throttling the mixture and, to some extent, by 
 varying the time of ignition. 
 
 Both governing and hand control are used in conjunction on 
 variable-speed motors. In this application the mechanical 
 governor limits the speed to a predetermined maximum and 
 maintains that speed as long as the demand on the motor for 
 power does not exceed its capacity at the speed limit of rotation 
 to which the governor is then set. When the hand control (or 
 foot control) is brought into use the governor is put out of action, 
 either partly or completely, as desired. Usually the movement 
 of the hand control changes the speed limit maintained by the 
 governor. Such a governor is generally constructed so as to 
 hold the speed fairly constant at the speed to which it is tempo- 
 rarily adjusted, within the speed limits of the motor. Throttling 
 the mixture is the method generally adopted. 
 
 Methods of Governing by Cutting out Full Charges of Fuel or 
 of Combustible Mixture. 
 
 71. Hit-or-Miss Governing in General. This method was 
 applied to the early motors operating on the Otto cycle, and 
 still finds extensive application especially in small and medium 
 sized motors. The speed cannot be as closely regulated as by 
 reducing the amount of the charge to keep down the speed when 
 the demand for power is low, but is sufficiently accurate for a 
 large range of service. 
 
 This method of governing gives the highest theoretical effi- 
 ciency of any, since each charge admitted is a full one, and the 
 compression is therefore always to practically the same pressure, 
 which is the maximum pressure suitable for the fuel. It may be 
 remembered that the efficiency is higher the higher the com- 
 pression pressure. 
 
 The usual means of securing the hit-or-miss effect is by the 
 use of a part (called a "trigger" or "pick-piece" in certain 
 forms) whose position is controlled by the governor in such a 
 
Il8 THE GAS ENGINE 
 
 manner that, when the speed is not in excess of the normal, it 
 engages with other parts (or does not engage) in such a manner 
 as to cause the valves to perform their functions regularly. 
 But when the speed exceeds the normal this part takes a position 
 such as either to cause the omission of the movement of a valve 
 or to modify its movement so that no charge is drawn in during 
 the suction stroke of the piston. 
 
 The device generally has a pair of sharp, beveled edges (knife- 
 edges) where the hit-or-miss occurs, so that when brought 
 together by a very slight movement of the governor the beveled 
 edges catch together and slip over each other so as to bring more 
 substantial parts into full engagement for operating the valve. 
 There are numerous modifications of the hit-or-miss apparatus. 
 
 A pendulum governor was used on the early thrust-rod valve 
 lifters, and still finds application on account of its great simplicity 
 and consequent small cost. It is used in its simplest form in 
 connection with a .valve whose stem is horizontal. The lift rod, 
 or the trigger attached to its end, is hinged and supports a weight 
 that hangs below the hinge. The reciprocating push rod has 
 a tendency to carry the suspended weight with it, but the inertia 
 of the weight causes it to lag behind the rod and thus deflect the 
 trigger from its horizontal position. The lag and deflection are 
 increased as the speed increases until, at the maximum speed of 
 the motor, the deflection is sufficient to cause the rod or trigger 
 to miss the valve stem so that the valve is not lifted, and thus a 
 charge of fuel is cut out. 
 
 In later mechanisms for hit-or-miss governing the centrif- 
 ugal governor with weights rotating about a shaft is also used 
 for moving the trigger, the cam, the cam roller, etc. 
 
 One mechanism has a rotary cam with a roller follower. 
 Both the cam and the follower have knife-edge projections which 
 engage and bring their lifting parts together when the speed is 
 below normal, but clear each other when it reaches the maxi- 
 mum, or vice versa. 
 
 72. Hit-or-Miss Governing by Omitted Openings of the 
 Mixture Inlet Valve. Four-Cycle Motor. This method finds 
 its application generally in motors with mechanically operated 
 
CONTROL OF POWER AND SPEED 119 
 
 inlet valves. The action of the governor prevents the opening of 
 the mixture inlet valve when the motor speed exceeds the normal. 
 The exhaust valve opens as usual both before and after the omis- 
 sion of the charge. 
 
 Either the springs of the inlet and exhaust valves must be strong 
 enough to hold the valves to their seats during the suction stroke 
 when the inlet is left closed, or additional means of holding the 
 valves to their seats must be provided. The degree of the partial 
 vacuum in the cylinder is greater at this time than at any other, 
 and the tendency of the suction to open the valves is, of course, 
 correspondingly great. 
 
 Since there is no admission at the time of a cut-out during the 
 suction stroke, there is a partial vacuum induced in the cylinder 
 at the end of the impulse stroke (without the impulse) when the 
 exhaust valve opens in its regular operation. This causes a rush 
 of inert gases from the exhaust port into the cylinder by which 
 foreign matter is apt to be carried from the exhaust passages 
 into the cylinder. 
 
 The speed at or about the time of the beginning of the suction 
 stroke determines how the governor shall act regarding the open- 
 ing or closing of the inlet valve. There are about two inertia 
 strokes between the action of the governor and the beginning of 
 the following impulse. 
 
 73. Hit-or-Miss Governing by Keeping the Exhaust Valve 
 Open during the Suction Stroke. Four-Cycle Motor. This 
 method is used in connection with an automatic inlet valve. Very 
 little suction can be produced by the action of the piston when the 
 exhaust is open, therefore there is little tendency to lift the inlet 
 valve. 
 
 It should be remembered, however, that if there is a long, 
 straight pipe for carrying off the exhaust the inertia of the 
 rapidly expelled gases may reduce the pressure in the cylinder 
 enough to open an inlet valve with a weak spring and draw in 
 a small amount of the mixture, but not enough to be ignited. 
 In such a case the fuel drawn in is simply passed through the 
 motor and wasted. The springs of automatic inlet valves are 
 apt to become weak in service. 
 
120 THE GAS ENGINE 
 
 As a precaution against the untimely opening of the inlet a 
 device for holding the inlet valve to its seat when the exhaust 
 is open is generally used. The simplicity of the valve mechan- 
 ism for this method of governing is the chief feature that recom- 
 mends it. The closeness of regulation is practically the same 
 as with the hit-or-miss mechanically operated inlet valve. 
 There is a possibility of drawing foreign matter into the cylinder 
 during the suction stroke when the exhaust valve is open. 
 
 74. Hit-or-Miss Governing by Keeping the Exhaust Valve 
 Closed during the Exhaust Stroke. Four-Cycle Motor. This 
 is simpler than either of the two methods just discussed, since 
 there is no need of any locking device for the inlet valve. It 
 has the objection, however, that the retained hot gases of com- 
 bustion heat the motor and destroy the lubricant in the cylinder 
 more rapidly than when they are allowed to escape at the end 
 of the impulse stroke. 
 
 75. Hit-or-Miss Governing by Keeping the Fuel Valve 
 Closed, but Opening the Mixture Inlet Valve to Admit Air during 
 the Suction Stroke. Four-Cycle Motor. The use of this method 
 is confined almost entirely to motors using permanent gas for 
 fuel. It can, however, be used by those in which air car- 
 bureted far beyond the ignition point is mixed with pure air to 
 form a combustible mixture as has been stated. But very few 
 motors that first carburate the air nearly to saturation and then 
 dilute it are found in use. 
 
 An additional valve for the fuel is required. It generally opens 
 into the air passage, or mixing chamber, near the mixture inlet 
 valve, and in such a manner as to cause the gas and air to mix 
 quite thoroughly before entering the cylinder. The mixture 
 valve is opened for every suction stroke. 
 
 This method of governing has an undesirable property that 
 is peculiar to it and is most marked when the mixture is some- 
 what too rich in fuel and the load changes suddenly from heavy 
 to light. Under these conditions the passage of cool air through 
 the cylinder during the several consecutive cut-outs that follow 
 the consecutive explosions of the heavy load, cools "the cylinder 
 to some extent and clears out the inert gases that remain after 
 
CONTROL OF POWER AND SPEED 121 
 
 the exhaust stroke immediately following the* last explosion. 
 This allows a greater weight of the mixture to enter when the 
 fuel valve is opened after several cut-outs, and the air in the 
 cylinder at the beginning of the suction stroke mixes with 
 the incoming overrich mixture so that a more perfect mixture 
 is formed in the cylinder. The greater weight of fuel, the more 
 perfectly proportioned mixture, and the absence of dilution by 
 inert gases all act to produce a greater impulse on the piston 
 than is obtained when there has been no cut-out. A greater 
 increase of speed during the first impulse after several cut-outs is 
 the natural result. Even with a single cut-out the energy of the 
 following explosion is greater than that of one following an 
 immediately preceding explosion. 
 
 76. Modern Modified Method of Cutting out Charges. Four- 
 Cycle Motor. At least one modern gas-engine builder has 
 introduced a cut-out device that reduces the objectionable speed 
 variation of this method to a considerable extent and completely 
 eliminates the drawing in of exhaust gases. In this method the 
 mechanical inlet valve is opened by a rotating cam with one lobe, 
 and the exhaust valve by an exhaust cam in the same manner. 
 They are both attached to a shaft that rotates at half the speed 
 of the crank shaft as long as explosions are needed regularly. 
 An increase of speed throws the cam shaft out of engagement 
 with its driver, and it remains at rest till the speed falls below 
 normal. It is then brought into engagement with its driver again 
 and opens the valves as usual. The device for driving the cam 
 shaft is of such a nature that the parts can be disengaged and 
 brought into engagement again during one revolution of the 
 crank shaft of the motor, corresponding to half a revolution of 
 the cam shaft. Therefore, when the motor is working at almost 
 its full capacity and a charge is cut out, the cam shaft will be 
 picked up again after one revolution of the crank shaft, the 
 mixture valve opened and a charge admitted so as to be exploded 
 after only six strokes of the piston instead of eight as with other 
 cut-out valve mechanisms. 
 
 The cam shaft is disengaged so as to come to rest just after 
 the exhaust valve closes. The latter remains closed until the 
 
122 THE GAS ENGINE 
 
 time to open for discharging exhaust gases again, so there is no 
 possibility of drawing foreign matter into the cylinder from the 
 exhaust port and pipe, as with some of the other devices for 
 governing. 
 
 Governing by Varying the Amount of Fuel Admitted for an 
 
 Explosion. 
 
 77. General. The power that is developed by an explosion 
 in the cylinder of a motor is proportional, at least in a measure, to 
 the amount of fuel that is admitted and burned during the impulse 
 stroke of the piston. Since the impulses occur regularly and are 
 graduated to the amount required to keep the speed constant in 
 this method of governing, it is therefore the method that gives the 
 closest speed regulation. 
 
 There are three methods by which the amount of fuel admitted 
 per charge can be varied so as to still give a combustible mixture 
 in the cylinder when the charge has been reduced within certain 
 limits. The three methods are: 
 
 a. Throttling by partly closing the passage through which the 
 
 mixture enters the cylinder, or by partly closing both the 
 air and the gas passages; 
 
 b. Varying the length of time during which the mixture inlet 
 
 valve is kept open; 
 
 c. Varying the length of time during which the fuel valve is 
 
 kept open, and opening and closing the air valve at 
 regular times. 
 
 78. Governing by Throttling. This method finds more 
 general application than any other. It is adapted to both two- 
 cycle and four-cycle motors using either permanent gas or car- 
 bureted air for fuel. The largest as well as the smallest motors 
 can be successfully governed by throttling. The valves for 
 throttling vary in form from the simple wing type or butterfly 
 type to somewhat complicated ones that have separate and 
 adjustable passages for air and gas. The simpler ones natu- 
 rally find most application to the smaller sizes of motors, which, 
 
CONTROL OF POWER AND SPEED 
 
 123 
 
 FIG. 59. f 
 
 Balanced Throttling Governor and Valve Mechanism of Nash Gas Engine. 
 National Meter Company, New York. 
 
 The air enters through a hand proportioning 
 valve i. The gas enters through a sim- 
 ilar proportioning valve in the same hori- 
 zontal plane as the air valve. The gas inlet 
 and valve are not shown in the illustration. 
 The gas and air mix in the chamber 2 and 
 pass through the two 
 openings at the disk 
 valves 3 and 4 into 
 the duct 5 leading 
 to the inlet valve 6. 
 The disk valves 3 and 
 4 are attached to the 
 governor spindle 7. 
 
 Air 
 
 The amount of the mixture 
 admitted to the combus- 
 tion chamber for a charge 
 is regulated by the gov- 
 ernor. When the speed 
 increases, the governor 
 lowers the disk valves 3 
 and 4, thus partly closing 
 theiropenings and cutting 
 down the amount of mix- 
 ture admitted. 
 
 The governor and 
 valve mechanism 
 are shown in the 
 lower part of the 
 illustration. 
 
 The exhaust pipe 8 
 is water jacketed. 
 
124 
 
 THE GAS ENGINE 
 
 however, are not necessarily those of the cheapest form of con- 
 struction. The double valve arrangement with one valve for 
 fuel and one for air is found only on motors using permanent gas 
 and the very limited number using air carbureted to nearly the 
 saturation point. A centrifugal governor is generally used to 
 move the throttle valve so as to give the required amount of 
 charge. 
 
 FIG. 60. 
 
 Proportioning, Mixing, and Throttle Governing Device for Gas Engine. The 
 Bruce-Merriam- Abbott Company, Cleveland, Ohio. 
 
 The principal parts of the device are: 
 
 An outer casing with provisions for gas and air connections; 
 
 A ported bushing fitting in the casing; 
 
 A cylindrical hollow valve with ports for gas and mixture. 
 
 The gas passes from the gas space at the bottom of the casing through the port in 
 
 the bushing and up between the bushing and valve to the top of the air space. 
 
 The gas then passes out through the bushing and mixes with the air flowing up 
 
 to the annular chamber marked "Mixture of Gas and Air" in the illustration. 
 
 From there the mixture goes through the numerous ports in the upper halves of 
 
 the bushing and valve to the inside of the valve and then out at the top. 
 The governor is connected to the valve spindle which extends downward from the 
 
 bottom of the device. Increase of speed causes the governor to lift the valve and 
 
 thus reduce the area of the port openings. 
 The gas and air are proportioned by moving the bent handle shown at the 
 
 bottom of the illustration. This rotates the valve and changes the area of 
 
 the gas ports. 
 
CONTROL OF POWER AND SPEED 125 
 
 The reduction of the charge causes a corresponding reduction 
 in the compression pressure. Since the efficiency of the trans- 
 formation of the heat energy of the gas into mechanical energy 
 increases with increased compression pressure, there is a de- 
 crease of this efficiency caused by throttling on account of the 
 reduced compression pressure that accompanies it. This de- 
 crease of efficiency is not so great, however, as to counterbalance 
 the advantage of the close regulation of speed that can be secured 
 by reducing the amount of the charge, as compared with other 
 methods, when close regulation is desired. 
 
 There is always some suction resistance to the motion of the 
 piston during the charging stroke in a four-cycle motor. This 
 resistance is increased throughout the stroke by throttling. The 
 suctional resistance abstracts mechanical energy from the motor. 
 The amount of energy thus abstracted is not entirely lost, how- 
 ever, for some of it is returned during the early part of the com- 
 pression stroke while the pressure in the cylinder is still below 
 atmospheric. 
 
 79. Governing by the Mixture Inlet Valve to Reduce the 
 Charge. Four-Cycle Motor. By the use of suitable valve 
 mechanism the inlet valve can be opened at the same time for 
 each charging stroke of the piston, and its closure timed later or 
 earlier so as to let in more or less mixture as the speed of the 
 motor decreases or increases. As compared with throttling, 
 practically the same delicacy of speed regulation can be secured 
 by this automatic cutting off of the admission of mixture. The 
 loss of efficiency in the heat transformation into mechanical 
 energy, due to the reduction of the compression pressure, is 
 practically the same as- for throttling, but there is not quite so 
 great a waste of mechanical energy during the suction stroke, 
 for with the cut-off governor the mean value of the resistance 
 to the motion of the piston during the suction stroke is not so 
 great as by throttling. This is because in cut-off governing 
 the inflow of the mixture is not restricted during the early part of 
 the suction stroke. There is free flow until the inlet valve closes. 
 Up to this point the suction resistance is only that due to the 
 passage of the gases through the unobstructed port. This 
 
126 
 
 THE GAS ENGINE 
 
 16 
 
 FIG. 61. 
 
CONTROL OF POWER AND SPEED 127 
 
 FIG. 61. (See also Figs. 62 and 60.) 
 
 Four-Cylinder, Four-Cycle, Single- Acting Gas Engine. 115 to 200 Horsepower. 
 The Bruce-Merriam-Abbott Company, Cleveland, Ohio. 
 
 1. Cylinder. 
 
 2. Piston. 
 
 3. Inlet valve. 
 
 4. Exhaust valve, water cooled. 
 
 5. Mixture port. 
 
 6. Air intake. 
 
 7. Gas intake. 
 
 8. Mixer and throttle. 
 
 9. Throttle valve stem. 
 
 10. Lever arm between throttle valve stem and governor. 
 
 11. Governor sleeve or quill. 
 
 12. Governor fly-balls. 
 
 13. Hand handle for proportioning mixture. 
 
 14. Exhaust gas main. 
 
 15. Vertical shaft for transmitting power to valve mechanism. 
 
 16. Gear on shaft driven by 15. 
 
 17. Gear on cam shaft. 
 
 18. Cam shaft. 
 
 19. Cam. 
 
 20. Cam. 
 
 21. Rocker arm for opening inlet valve. 
 
 22. Rocker arm for opening exhaust valve. 
 
 As the speed increases the governor lifts the throttle valve by means of the stem 9 
 and cuts down the flow of mixture into the motor cylinder, while keeping the 
 proportions of the mixture constant (constant quality mixture). 
 
 The cooling water for the exhaust valve flows down through the small pipe in the 
 hollow valve stem and enters the valve at the bottom of the hollow space, then 
 flows through the openings into the hollow valve stem near the top of the water 
 space in the valve and passes up and out through the annular space between the 
 inflow pipe and the walls of the hollow stern. 
 
128 
 
 THE GAS ENGINE 
 
CONTROL OF POWER AND SPEED 129 
 
 suction resistance, up to the corresponding position of the piston, 
 is much less than when the inlet passage is throttled. After the 
 inlet valve is closed, the suction resistance increases to the end 
 of the stroke, where it has the same pressure as at the end of the 
 throttled stroke, if the weight of the charge is the same in both 
 cases. Here again the resistance during the completion of the 
 suction stroke after cut-off is less than by throttling during the 
 corresponding latter part of the stroke. The mechanical energy 
 returned to the motor by suction during the early part of the 
 compression stroke is the same by both methods. 
 
 There is a possibility that the temperature of the mixture at 
 the end of the charging stroke is higher by cut-off than by throttle 
 governing, since in the former the complete charge is in the 
 cylinder some time before the completion of the stroke, and is 
 therefore heated more than when drawn in gradually as by 
 throttling. The principal effect of heating the mixture during 
 the charging stroke is to reduce the weight of the charge and the 
 power of the motor. The difference of this effect in the two 
 cases is hardly great enough to need attention. 
 
 80. Governing by the Fuel Valve to Reduce the Charge. 
 This method is applicable to both two-cycle and four-cycle 
 motors using gas or vapor fuel. 
 
 Its especial field is the two-cycle motor of the type in which 
 the air and fuel are separately precompressed in auxiliary com- 
 pressors to a slight extent, sufficient to force them into the motor 
 cylinder when the exhaust port is opened, but it is equally appli- 
 cable to four-cycle motors. It has already been said of this 
 type of motor that when the piston is at and near the out 
 position the exhaust port is open and the charge enters while 
 the piston is at and in the neighborhood of the extreme out 
 position and while the exhaust port is open. Air is admitted 
 first to scavenger the cylinder, and then gas is also admitted to 
 mix with the entering air' in proportion to form a combustible 
 mixture just before they enter the combustion cylinder. The time 
 at which the fuel valve opens is regulated in accordance with the 
 need of fuel to maintain the speed of the motor. The air and 
 fuel valves, or the air and mixture valves, close at the same time, 
 
130 
 
 THE GAS ENGINE 
 
 13 
 
 15 
 
 10 
 
 18 
 
 FIG. 63. 
 
 FIGS. 63 AND 64. 
 
 Valve Mechanism of Gas Engine. Governing by fuel valve. 2000 kilowatts 
 capacity in double-acting twin tandem engine. (Four cylinders, eight combus- 
 tion chambers.) The Allis-Chalmers Company, West Allis, Wisconsin. 
 
 1. Cylinder, 
 
 2. Piston. 
 
 3. Inlet poppet valve for mixture. Closed by spring. 
 
 4. Head on upper end of inlet poppet valve stem. 
 
 5. Rocker arm pivoted at 6 and resting (through a small sliding block) on 5. 
 
 Operated by cam rocker 7. 
 
CONTROL OF POWER AND SPEED 
 
 FIG. 64. 
 
 6. Pin connection between 5 and stationary part of engine. 
 
 7. Cam-shaped rocker pivoted at 8 and bearing on its follower 5. 
 
 8. Pin connection between 7 and stationary frame of engine. 
 
 9. Double-seated hollow gas valve. Concentric with 3. Spring closed. 
 
 10. Head on gas valve stems. 
 
 11. Cam-shaped rocker resting on 13 and pivotally connected to 10. 
 
 12. Pin connection between 10 and n. 
 
 13. Movable rest for cam rocker n. Partly supported by the stationary frame of 
 
 the engine. 
 
 OF THE 
 
 UNIVERSITY 
 
 OF 
 
132 THE GAS ENGINE 
 
 14. Eccentric rod between rocker 7 and eccentric on 18. 
 
 15. Rod connection between 7 and n. 
 
 16. Eccentric strap on 14 and on eccentric 17. 
 
 17. Eccentric on 18. 
 
 18. Lay shaft or half-speed shaft. 
 
 19. Rod connection between rest 13 and an eccentric on the governor-actuated 
 
 shaft 20. 
 
 20. Regulating shaft or governor shaft. 
 
 21. Governor rod. 
 
 22. Hand grip for dropping 13 so that the gas valve will not lift (open). 
 
 23. Valves for proportioning gas and air by hand. 
 
 24. Hand wheel for setting proportioning valves. 
 
 25. 26. Electric igniters. 
 
 27. Exhaust poppet valve. Water cooled. 
 
 28. Head on lower end of exhaust valve stem. 
 
 29. Rocker arm cam follower for lifting exhaust valve 27. Pivoted to stationary 
 
 frame of engine at 30. 
 
 30. Pin connection between stationary frame of engine and 29. 
 
 31. Rocker cam for lifting 29 and the exhaust valve 27. Pivoted to the stationary 
 
 engine frame at 32. 
 
 32. Pin connection between 31 and the engine frame. 
 
 33. Eccentric rod between the rocker cam 31 and an eccentric on lay shaft 18. 
 
 34. Water space in exhaust valve. 
 
 35. Water pipe for exhaust valve 27. 
 
 36. Water inlet to exhaust valve. 
 
 37. 38. Cooling-water spaces. 
 
 39. Check valve for starting with compressed air. 
 
 The governor regulates the amount of gas admitted for each charge by raising and 
 lowering the rest 13 on which the cam-shaped lifting arm u : rocks, and thus 
 varying the extent of opening of the gas valve. 
 
 When the exhaust valve begins to open against the pressure in the cylinder, the line 
 of contact between the eccentric-driven rocker 31 and its follower 29 is near the 
 pivot (fulcrum) 32 where the rocking cam is supported by the stationary frame 
 of the engine. This gives a long lever arm for the eccentric rod 33 to act on when 
 first lifting the valve from its seat, and a slow initial motion to the valve. As 31 
 rises, the line of contact between it and 29 moves out toward the pivot 30 of the 
 rocker 29, thus giving an increasing speed of lift to the valve relative to the motion 
 of 31 and a decreasing leverage for 33. The reverse occurs during the closing of 
 the valve, so that it seats gently. Since the force required to move the valve 
 after it leaves its seat is much less than at the instant of lifting it from its seat, 
 the decreasing leverage as the valve rises is of no disadvantage in the application 
 of the lifting force, and is advantageous in giving the valve a rapid movement 
 after it leaves its seat. 
 
 The action of the mixture inlet valve is the same as that of the exhaust valve, and 
 that of the gas valve mechanism is similar in a general way. 
 
 The gas enters around the outside and through the inside of the shell gas valve. 
 
CONTROL OF POWER AND SPEED 133 
 
 which is invariable in relation to the movement of the piston. 
 If the air and combustible mixture stratify in the combustion 
 cylinder as desired, the part next the piston is filled with air and 
 possibly some of the inert gases of combustion, and the com- 
 bustion chamber is filled with perfect mixture, all at about 
 atmospheric pressure before compression begins. 
 
 The igniter is located so as to be surrounded by combustible 
 mixture at the instant for ignition. 
 
 Since the mixture arranges itself in a stratum in the cylinder 
 at less than full loads, the fuel can be cut down to a much smaller 
 amount than when the combustible charge is distributed through- 
 out the cylinder. Therefore close speed regulation can be accom- 
 plished satisfactorily for all loads including very light loads and 
 the friction load of the motor alone. 
 
 By this method of regulation the pressure of compression is 
 always kept the same, hence there is no reduction in the effi- 
 ciency of heat transformation into mechanical energy on account 
 of a reduced compression pressure corresponding to a light load, 
 as there is when mixture alone is admitted to the cylinder in 
 amounts varying according to the demands for power. This 
 is true theoretically, because the efficiency of the cycle remains 
 always the same in a motor when the initial and final pressures 
 of the compression stroke do not change. 
 
 There is no power loss on account of suction resistance in 
 this case, but its counterpart appears in the energy expended 
 to compress the air and gas for forcing them into the motor 
 cylinder. 
 
 As applied to the four-cycle motor, this method of governing 
 can be used without any auxiliary compression cylinders or 
 pumps. The suction of the charging stroke is effective here as 
 in other methods of governing. The mixture valve opens and 
 closes at invariable times, and the fuel valve is opened early 
 or late, as the speed is slow or fast within the limits of the 
 sensitiveness of governing, and closes at an invariable time. 
 The same advantage of close governing on very light loads, 
 and on motor friction load, obtains here as in the two-cycle 
 motor. 
 
134 
 
 THE GAS ENGINE 
 
CONTROL OF POWER AND SPEED 
 
 a ? 
 
136 
 
 THE GAS ENGINE 
 
CONTROL OF POWER AND SPEED 
 
 137 
 
 FIG. 66. 
 Section through Cylinder and Valve. 
 
138 
 
 THE GAS ENGINE 
 
 FIG. 67. 
 Section on A-B, Fig. 65. 
 
CONTROL OF POWER AND SPEED 
 
 139 
 
 000000 
 
 Q Q Q O |Q Q 
 h= - 
 
140 
 
 THE GAS ENGINE 
 
 12 
 
 FIG. 69. 
 Valve closed for Compression and Impulse Stroke. 
 
CONTROL OF POWER AND SPEED 
 
 141 
 
 FIG. 70. 
 Valve in Exhaust Position. 
 
142 
 
 THE GAS ENGINE 
 
 12 
 
 FIG. 71. 
 Valve in Charging Position. 
 
CONTROL OF POWER AND SPEED 143 
 
 1 FIGS. 64 a , 64b, AND 65 TO 71. 
 
 " Complete Expansion " Gas Engine. Four-Cycle, Double- Acting Tandem 600 
 Horsepower. The Wisconsin Engine Company, Corliss, Wis. 
 
 1. Cylinder. 
 
 2. Piston. 
 
 3. Water-jacket space. 
 
 4. Poppet valve for inlet and exhaust. Stem extends down through the bottom 
 
 of the valve cage. 
 
 5. Cylindrical valve with air, power gas, and exhaust ports. Hollow stem 
 
 down nearly to bottom of valve cage. Concentric with 4. 
 
 6. Piston on bottom of poppet valve stem. 
 
 7. Automatic fuel cut-off valve. Cylindrical. Concentric with 4 and 5. Motion 
 
 regulated by governor. 
 
 8. Ported tubular valve for proportioning air and gas by hand. 
 
 9. Stationary bushing and poppet valve seat. 
 
 10. Bearings for arm that lifts 5 and 4. 
 
 11. Rods for moving cut-off valve 7. Operated by cam on shaft 18. 
 
 12. Connection for pipe leading to 13 and the combustion chamber. 
 
 13. By-pass valve. Operated from shaft 18. 
 
 14. Pipe connection between by-pass valve 13 and cylinder space under poppet 
 
 valve piston 6. 
 
 15. Rocker arm for lifting valves 4 and 5. Cam driven. 
 
 1 6. Cam shaft, lay shaft, or half-speed shaft. 
 
 17. Cam for operating valves 4 and 5. 
 
 1 8. Small cam shaft. Controlled by governor. 
 
 19. Igniter. 
 
 20. Igniter. (Shown only in longitudinal section.) 
 
 21. Relief valve or snifter valve. 
 
 22. Gas supply pipe. 
 
 23. Air supply pipe. 
 
 24. Exhaust pipe. 
 
 25. Compressed air valve for starting engine. 
 
 26. Compressed air supply pipe. 
 
 27. Starting handle. 
 
 28. Screw gear on main shaft (crank shaft) for driving cam shaft or lay shaft at half 
 
 speed of main shaft. 
 
 29. Screw gear on cam shaft or lay shaft. Driven by 28. 29 also acts as an oil 
 
 pump for supplying lubricating oil to the main bearing of the crank shaft, 
 the main crosshead, and the crank pin. 
 
 30. Governor. 
 
 31. Main crosshead. Not shown in line illustrations. 
 
 32. Intermediate crosshead. 
 
 33. Rear crosshead. 
 
 34. Cooling water supply pipes to valve case, cylinder, and cylinder heads. 
 
 35> 36, 37- Water connections to intermediate crosshead. Swinging telescopic 
 
 connections. For water-cooling the pistons and piston rod. 
 In the longitudinal section, Fig. 65, the valves of two combustion chambers are 
 shown in the positions for movement of the pistons toward the crank shaft (toward 
 the left). Combustion chamber B (not shown) is on the impulse (expansion) 
 stroke; A (not shown) is exhausting; C is compressing; and D is charging. 
 
144 THE GAS ENGINE 
 
 Enlarged sectional views of the valves are shown in Figs. 69, 70, and 71 for the 
 three positions during the different steps of the cycle. The coil compression springs 
 are omitted. 
 
 Fig. 69 shows the position of the valves for one combustion chamber during the 
 charging and impulse strokes. The poppet valve 4 is closed and the others have no 
 action or function during this time. 
 
 Just before the completion of the impulse stroke the by-pass valve, 13, Figs. 65 
 and 66, is opened by cam action and the pressure in the combustion chamber is 
 transmitted through the pipe 14 to 9 and to the under side of the balancing piston 6 
 on the lower end of the stem of the poppet valve 4. The pressure under the piston 6 
 almost balances that on the top of the poppet valve. The cylindrical, double- 
 ported valve 5 is then mechanically lifted by cam action at an invariable position of 
 the motor piston, by a rocker arm bearing against the trunnions 10. As the cylin- 
 drical valve 5 rises it carries the poppet valve 4 with it, thus opening the port for 
 exhausting. 
 
 Fig. 70 shows the position of the valves of one cylinder for exhausting. The air 
 and gas ports are of course closed during the exhaust stroke. 
 
 At about the end of the exhaust stroke the cylindrical valve 5 descends under 
 the combined action of the expansion coil spring (see longitudinal section) and the 
 cam, so that its ports register with those of the air and gas ducts around the valves 
 just after the beginning of the charging stroke. This position of 5 is shown in Fig. 
 71. If the engine is on only part load, the gas cut-off valve 7 still retains the posi- 
 tion shown in Fig. 70, so that the gas port is closed and air only is allowed to enter 
 the cylinder. Later in the charging stroke, at a time determined by the governor, 
 cam action allows the cut-off valve 7 to be lifted by the expansive force of the coil 
 compression spring (see longitudinal section) bearing against it, so that the port 
 in the cut-off valve registers with the gas port in the cylindrical valve 5 and in the 
 bushing 9. 
 
 Fig. 71 shows the position of the valves for admitting both gas and air to the 
 cylinder. At the fixed time for cutting off the admission of mixture to the cylinder, 
 the double-ported valve 5 is lifted by cam action to the position shown in Fig. 69, 
 thus closing both the air and gas ports. 
 
 Up to this time since opening for exhausting, the poppet valve is held up by the 
 exhaust gases under the balancing piston 6 on account of throttling which prevents 
 rapid escape of the gases from under 6. After the mixture is cut off, the poppet valve 
 4 settles to its seat so as to be closed at the beginning of the compression stroke. 
 
 The gas cut-off valve 7 is drawn down by cam action at about the same time that 
 the cylindrical valve 5 is lifted to cut off air and gas. 
 
 At full load the gas cut-off valve 7 rises early, so that the admission of gas begins 
 at the same time as that of the air. 
 
 Summary of the Valve Motions. The cylindrical, double-ported valve 5 moves 
 at invariable times relative to the motion of the motor piston. The poppet valve 
 4 is lifted (opened) at a fixed instant and closes between the cut-off of the mixture 
 and the completion of the charging stroke. The gas cut-off valve moves to admit 
 the fuel gas at variable times controlled by the governor. For full loads it opens 
 so that gas is admitted as early as the air, but it opens later for light loads. It does 
 not act to stop the flow of gas, which is done by 5. 
 
 Cutting Out Combustion Chambers. When the load falls below one-fifth full 
 load, the governor automatically cuts out two of the combustion chambers by 
 leaving their gas valves closed. The engine then runs on only two combustion 
 chambers. 
 
CONTROL OF POWER AND SPEED 145 
 
 When the engine is run for some time on light loads, one <y more of the com- 
 bustion chambers can be permanently cut out by hand. This is done by locking 
 the exhaust valve open. 
 
 Proportioning Gas and Air. The tubular shell 8, outside of the stationary 
 bushing 9 that surrounds the valves, is rotatable to a limited extent by hand mechan- 
 ism. The rotary adjustment of 8 changes the relative areas of the air and gas 
 ports leading from the outer ducts to the cylindrical valve 5 and regulates the pro- 
 portions of gas and air in the mixture. 
 
 Relief or Snifter Valves. In order to prevent abnormally high pressures in the 
 cylinder, each combustion chamber is provided with a spring-closed relief valve of 
 the same nature as those used on steam engines for allowing the escape of water 
 from the cylinder, or of the nature of a safety valve on a steam boiler. 
 
 The relief valves come into action in case of premature ignition during the com- 
 pression stroke. 
 
 Igniters. Each combustion chamber has two igniters of the low-tension make- 
 and-break type. One is placed in the port at 20 and the other well up toward the 
 top of the combustion chamber at 19. This disposition insures dry contact points 
 on the upper igniter when starting with cold cylinders, and also the ignition of the 
 charge by the lower igniter when the engine is running on a light load with a corre- 
 spondingly small amount of gas admitted at the latter part of the charging period. 
 
 The igniters can be removed and replaced in any combustion chamber while the 
 engine is running, by locking the open exhaust valve of that chamber. 
 
 Cooling Water. The cooling water for the cylinders and the exhaust valves 
 enter below the exhaust valves and passes up to the top of the cylinder to the open 
 top of an overflow pipe. This pipe pierces the jacket casing of the cylinder near 
 the bottom and close to the end near the intermediate crosshead. The portion of 
 the pipe between the open overflow end at the top of the jacket space and the point 
 where it pierces the jacket wall is inside the water space. 
 
 The pistons and piston rods are cooled by water that flows to the intermediate 
 crosshead through oscillating telescopic pipe connections. A pipe in the center of the 
 hollow piston rod leads the water from the intermediate crosshead to the rear cross- 
 head 33. The water flows back through the space between the central pipe and 
 the wall of the hollow piston rod to the piston, then through the piston and back to 
 the outflow connection at the intermediate crosshead. The other piston and its 
 portion of the rod are cooled similarly. 
 
 Lubrication. The screw gear 29 on the cam shaft (lay shaft) 16 and under the 
 main shaft (crank shaft) acts as an oil pump for forcing streams of lubricating oil 
 to the main bearing of the crank shaft, the crank pin, and the main crosshead. The 
 gear is enclosed in a case that fits a portion of the periphery closely, so that, when 
 there is sufficient oil in the casing, the gears act much as an ordinary gear pump 
 whose spaces between the teeth are the pockets that carry the oil around in pump 
 action. The other bearings have self-oiling devices or run in an oil bath. 
 
 The pistons and metallically packed stuffing boxes are lubricated with gas engine 
 cylinder oil by mechanically driven sight-feed pressure lubricators. 
 
 Starting the Engine. The engine is started by compressed air at about 125 
 pounds pressure. A cam on the governor shaft acts to admit the air during the 
 impulse stroke until the pressure from combustion during this stroke is sufficiently 
 great to hold the air-admission check valve closed when the compressed air is cut 
 off by shutting the main air valve. 
 
146 
 
 THE GAS ENGINE 
 
 Governors. 
 
 81. The work to be performed by the governor of a gas or oil 
 motor is generally very light. The governor can therefore be 
 small. Its sensitiveness -naturally depends on the desired 
 closeness of speed regulation. The centrifugal type is generally 
 used in forms analogous to those used on throttling steam engines 
 and on those with Corliss or analogous valve gears for cutting 
 off steam at part stroke. An exception to this practice is the 
 hydraulic governor. 
 
 FIG. 72. 
 Governor and By-Pass Oil Valves for Hornsby-Akroyd Oil Engine. 
 
 The vertical pipe at the right of the bevel gears is connected to the discharge of the 
 fuel oil pump. The curved pipe with the glass sight (at the extreme right) leads 
 to the fuel oil tank. 
 
 When the speed of the motor increases, the governor acts through the horizontal 
 lever arm so that the end of the latter forces down a small valve above the end of 
 the vertical pipe. The opening of this by-pass valve allows a portion of the oil 
 delivered by the pump to return to the tank and thus reduces the quantity of 
 oil that is forced into the vaporizer. The pump discharge is also connected to 
 the vaporizer. If the speed of the motor exceeds a certain limit, the governor 
 acts in the same manner as before to open a larger by-pass valve that is concen- 
 tric with the smaller one already mentioned. The opening of the larger valve 
 completely (or nearly completely) cuts off the injection of oil into the vaporizer. 
 
 The speed to which the motor is governed can be changed by moving the small 
 cylindrical weight along the left-hand extension of the horizontal arm. 
 
CONTROL OF POWER AND SPEED 147 
 
 82. Hydraulic governors are used to some extenton automobile 
 motors that have a pump for circulating the cooling water. 
 When the speed of the pump is proportional to that of the motor, 
 the pressure of the water at points near the pump varies in 
 nearly the same proportion as the speed of the motor. This 
 variation of pressure with variation of speed is utilized to open 
 or close the throttle as the speed of the motor falls or rises. 
 
 In the more general forms of hydraulic governor, the water 
 acts against one side of a corrugated diaphragm to the center of 
 which is attached the mechanism that connects to the throttle. 
 The variation of the water pressure moves the central part of the 
 diaphragm, and the motion of the latter is transferred to the 
 throttle. 
 
 The accuracy of governing in this manner is not great, but 
 this is not important for variable-speed motors operating under 
 the usual conditions. 
 
 The simplicity of the governor and the absence of wearing 
 parts are strong points in its favor in automobile use, where 
 the dust and grit that invariably reach bearings that are not 
 thoroughly protected cause rapid wear. 
 
 Hand Control of Speed and Power. 
 
 83. General. The nature of the requirements for variable 
 speed and power that the motor must fulfil needs to be under- 
 stood before the control can be studied comprehensively. These 
 requirements cover a wider range in the automobile than in 
 any other service. 
 
 In the automobile the motor is called upon to run at any speed 
 from the highest permissible on account of danger of its flying to 
 pieces, to the lowest at which the inertia of the moving parts will 
 keep it going between impulses. It is also expected to deliver 
 power of varying amount up to its full capacity for the speed at 
 which it is rotating. When the clutch is thrown into engagement 
 to start the car, the motor should, when desired, change quickly 
 from its friction load to its full capacity corresponding to the 
 speed at which it is rotating. When running idly with the driving 
 gear disconnected, it works against its own friction resistance 
 
148 THE GAS ENGINE 
 
 only. It must drop from full load to friction load quickly, almost 
 instantly, when the friction clutch for transmitting the power is 
 suddenly disengaged, as in an emergency at the time the car is 
 climbing a steep hill or rapidly gaining speed on a level road. 
 The motor is often used as a brake for retarding the speed of the 
 car, either when stopping the car or descending a hill. 
 
 As has already been pointed out, the speed and power of a 
 motor can be regulated either by varying the amount of fuel 
 supplied during each charging stroke or by varying the time, 
 relative to the position of the piston, at which the charge is 
 ignited and burned. Except in one or two isolated cases, variable- 
 speed motors are so constructed that both methods can be applied 
 simultaneously. 
 
 Hand control of the fuel can be effected by any of the methods 
 that have been given for governing. The only change necessary 
 is the replacement of the governor by a hand or foot device for 
 regulating the supply of fuel. 
 
 Governor and hand control can both be applied by connecting 
 to the governor, or the parts closely related to it, a hand mechanism 
 by which the speed at which the governor acts can be varied at will. 
 
 Throttling the fuel supply is, with few exceptions, the method 
 adopted for its control in variable-speed motors. 
 
 84. Early and Late Ignition. Definitions. The instant at 
 which the charge in the cylinder of a motor is ignited can be 
 determined accurately in relation to the position of the piston 
 and crank when the igniter is of the make-and-break or break-and- 
 make type and has the contact points separated by the action of 
 rigid mechanism between it and the crank shaft or piston. In 
 an igniter of this type the contact points separate, for a given 
 setting, at the same position of the piston and crank shaft whether 
 the speed is high or low. 
 
 When a variable-speed motor is running at moderate speed, 
 the ignition apparatus is so timed that the igniting arc will be 
 formed at about the time the piston has completed the compres- 
 sion stroke and is ready to start on the impulse stroke, in other 
 words, at about the dead-center position of the crank: The dead- 
 center position in the usual types of motors is that at which the 
 
CONTROL OF POWER AND SPEED 149 
 
 axes of the crank shaft, crank pin, and of the piston pin or wrist 
 pin all lie in the same plane and the piston is at one end of its 
 path of travel. 
 
 Under certain conditions of speed and power the arc is timed 
 to come earlier in the rotation of the crank, and under other 
 conditions later. 
 
 The terms " early spark " and " late spark," or " early igni- 
 tion " and " late ignition," are used to designate the different 
 times of ignition. They are only relative terms used in a general 
 way. There is no fixed boundary between early and late igni- 
 tion. The act of adjusting the ignition apparatus to make 
 earlier ignition is called " advancing the spark," and adjusting; 
 for later ignition " retarding the spark." 
 
 The exact time of separation of the contact points of an igniter 
 varies in relation to the position of the piston in its travel when the 
 force that separates the contacts is transmitted through a spring 
 and the speed of the motor varies. This is due to the inertia of 
 the parts that are actuated by the spring to cause the separation 
 of the contacts. The lag due to inertia may be of appreciable 
 magnitude in comparison with the movement of the piston at 
 high speeds. 
 
 In a similar manner, when an induction coil or transformer is 
 used as a part of the ignition apparatus its use makes it impossible 
 to determine at just what position of the piston and crank the 
 spark passes. This refers to the usual outfit of a motor in 
 service. 
 
 When glowing hot surfaces are used to ignite the charge .there 
 is no means of telling the exact instant of ignition. 
 
 85. Early and Late Ignition Effects on Power and Speed. If 
 a variable-speed internal-combustion motor is running at moderate 
 speed under any constant load with ignition at dead center, and 
 the ignition is changed to come later in relation to the movement 
 of the parts of the motor, the speed and power will immediately 
 drop if there is no governor to regulate the fuel supply. Under 
 certain conditions the motor will take the new speed and hold it 
 approximately, while the torque resistance to the rotation of the 
 motor remains constant at the same value as before the ignition 
 
150 THE GAS ENGINE 
 
 was retarded. The power developed is decreased in about the 
 same proportion as the speed of rotation. The energy given to 
 the piston at each impulse is the same as it was at the higher 
 speed. It is assumed that the strength, or hotness, of the 
 igniting arc or spark remains constant. 
 
 The reason that the retarded spark or arc causes a decrease 
 of speed is that, with the later ignition, the charge does not burn 
 early enough in the stroke of the piston at the higher speed to 
 give it as great an impulse as before retarding the ignition, and 
 the contents of the cylinder escape at a higher pressure and 
 temperature than with the earlier ignition. But when the speed 
 falls, inflammation and combustion are both completed earlier 
 in the stroke, so that the resulting mean pressure is higher and 
 the gases expand through a greater portion of the stroke after the 
 charge has completely burned. 
 
 By retarding the ignition still more, the speed and torque 
 will both be decreased. With late ignition and a greatly re- 
 duced speed, the charge will still be burning when the exhaust 
 port is opened. When the ignition is extremely late, even 
 though the speed is rather high, the exhaust will come out as a 
 flame. In extreme cases the flame will be carried through and 
 out of the opening of an exhaust pipe several feet long. 
 
 If the ignition is now advanced, the speed and power will be 
 increased until they return to the initial values when the ignition 
 reaches the dead center again. By advancing the ignition still 
 further, the speed and power will generally be still further in- 
 creased for a slight advance; they will always be increased in a 
 high-speed motor. But still further advance will cause a de- 
 crease of power, and if the torque is still kept constant, as has been 
 assumed, the speed will drop. If the ignition is advanced to 
 come very much before dead center, the motor will slow down 
 suddenly and stop quickly, sometimes with a sudden reversal 
 of rotation due to the explosion of a charge before the com- 
 pletion of the compression stroke and the consequent driving 
 back of the piston from the combustion chamber before dead 
 center is reached. 
 
 The increase of power and speed caused by advancing the 
 
CONTROL OF POWER AND SPEED 151 
 
 ignition from the dead-center position to a slight degree earlier, 
 in motors other than slow-speed ones, is due to the fact that the 
 early ignition gives the charge time to become well inflamed by 
 the time compression is complete, so that combustion is fin- 
 ished early in the impulse stroke and the mean pressure on the 
 piston is increased. But when the advance becomes so great 
 that the pressure attained before the completion of the compres- 
 sion stroke comes so early and is of such intensity as to seriously 
 check the motion of the piston and to detract from the energy 
 that should be transmitted to the piston during the impulse 
 stroke, the motor of course loses power. And not only does it 
 lose power, but heavy stresses are thrown on the parts, and if 
 there is the slightest looseness, or lost motion, in any of the con- 
 nections between moving parts, it will be indicated by knock- 
 ing, hammering, or pounding. 
 
 86. Time of Ignition as Affected by Degree of Compression. 
 - If a throttle-regulated motor is running on a light load with 
 the ignition so timed as to give the maximum power per pound 
 of fuel, and the throttle is then opened either for speeding up or 
 to meet the demands of a rapidly increasing load, there will be 
 immediate knocking in a motor that has some lost motion, as 
 evidence that the ignition is too early for the higher compression 
 that accompanies the opening of the throttle and consequent 
 taking in of larger charges. The ignition must be retarded to 
 give satisfactory running. And, on the other hand, when the 
 motor is again throttled for a light load, the power can be in- 
 creased by advancing the spark when the speed of rotation is 
 the same as before. 
 
 The rates of inflammation and combustion are more rapid the 
 higher the compression pressure. They both act to suddenly 
 check the motion of the piston when ignition takes place before 
 the completion of the compression stroke, and thus cause ham- 
 mering or pounding. When the compression is high, knocking 
 will sometimes occur before the ignition is advanced to the time 
 that gives the maximum power for the speed and setting of the 
 throttle. This is seldom true, however, when the load is light 
 and the throttle well closed. 
 
152 THE GAS ENGINE 
 
 87. Lag in Jump-Spark Ignition Apparatus. In all the 
 various systems of jump-spark ignition there is a time interval 
 of greater or less length between the instant the timer closes the 
 primary circuit and the passing of the spark across the spark gap 
 inside the cylinder in the secondary circuit. This time interval 
 of delay in the passing of the spark will be called the " lag " of 
 the electrical apparatus. 
 
 When the battery circuit is closed by the timer in the battery 
 system of ignition, the current is retarded, in gaining its maxi- 
 mum value, by the inductive resistance of the induction coil. 
 This induction resistance is due chiefly to the magnetic lag of the 
 soft-iron core and the reactionary effect of the current in the 
 secondary winding. This causes a lag in the formation of the first 
 spark at the spark plug, even if a spark jumps before the primary 
 current is broken by the interrupter. In most induction coils 
 no high-tension spark is formed until the interrupter breaks the 
 primary circuit. When the spark does not come till the battery 
 circuit is broken, there is an additional lag caused by the inertia 
 of the vibrator or interrupter. The tofcal lag has a time value 
 that is equal to that of a very considerable part of a piston stroke 
 in a small, high-speed motor. Therefore, if the timer is set to 
 give a spark at the dead center when the motor is cranked by 
 hand, the spark will not jump till long after the dead center has 
 been passed when the motor speeds up. In order to keep the 
 spark at dead center at the higher speed, the timer must be 
 advanced accordingly. Advancing the timer to keep the spark 
 at the same place in the motion of the piston is generally, and 
 incorrectly, called advancing the spark. 
 
 The difference in the amount of advance of the timer neces- 
 sary in the make-and-break low-tension system, as compared 
 with the jump-spark system with battery and induction coil, is 
 due to the lag of the latter apparatus. It is not because the 
 ignition must take place earlier in the cycle by one method of 
 ignition than by the other. The necessary advance of the spark 
 itself (not the timer) or of the arc is practically the same in both 
 cases when their hotness does not vary with the speed. 
 
 Jump-spark systems with a transformer for raising the electric 
 
CONTROL OF POWER AND SPEED 153 
 
 tension all have some lag, which is generally less than for those 
 having an interrupter induction coil. 
 
 88. Hand Control by Throttle and Spark. In order to bring 
 out as clearly as possible the nature of the work that must be 
 done by the motor and the methods of manipulating the con- 
 trols, the operation of the automobile will be taken up in some 
 of its phases. It will first be assumed that the control is 
 entirely by hand, there being no governor or safety device for 
 regulating the speed of the motor. Jump-spark ignition with 
 a battery will be considered first. 
 
 When the motor is to be started by hand cranking, the spark 
 is set at or later than the dead center, otherwise the motor will 
 kick backward, with danger to the operator. The throttle is 
 opened partly. After starting, if the motor is to rotate while 
 the car remains still for a while, the throttle is then nearly 
 closed and the spark is set late to give a slow speed. 
 The throttle should be closed as far as possible with still enough 
 opening to keep the motor turning over slowly. Just before 
 throwing the friction clutch into engagement to start the car, 
 the throttle is opened to produce a more powerful torque and 
 power to give the car momentum. As the speed of rotation 
 increases, the timer is advanced to keep the spark at least as 
 early as at the time of throwing in the clutch. The timer is 
 generally moved up to give a spark at least as early as the 
 dead-center position of the crank. When the motor gets well 
 up toward its maximum speed and the transmission gears are 
 to be shifted so as to give the car more travel per revolution 
 of the motor, the timer is retarded and the change of gears 
 quickly made. The throttle need not be closed any when the 
 gear shift is made so quickly that the motor has not time to 
 race. 
 
 When the car is running along a good, level road, the throttle 
 and spark are adjusted in conjunction till the throttle is open 
 the least amount possible, and the timer is advanced to the point 
 that gives the best result. When approaching an up grade or a 
 piece of heavy road that is to be passed over without decrease of 
 speed the timer is gradually retarded and the throttle opened to 
 
154 THE GAS ENGINE 
 
 give the requisite power. The more the throttle is opened, the more 
 the timer must be retarded; but the timer is always kept as far 
 advanced as possible in order to get the maximum power for the 
 setting of the throttle without pounding in the motor. When 
 the motor is new and all the parts snugly fitted, the timer is set 
 up to the position that gives maximum driving effort. If it is 
 desired to pull the car slowly for a short time without changing 
 from the high-speed gear, it can be done best by retarding the 
 timer till the spark comes late, and opening the throttle well to 
 secure a large torque. This method is very satisfactory so far 
 as handling the car is concerned, but it is wasteful of fuel and 
 heats the motor rapidly. The exhaust pipe will become glowing 
 hot after driving in this manner for some time, and the cooling 
 water will soon boil except in very cold weather. If the slow 
 speed of travel is to be continued for some time, the transmission 
 gears should be shifted so as to let the motor turn over more 
 rapidly with the throttle well closed and the timer far advanced. 
 A late spark makes the motor work smoothly and the car easy 
 to handle on slightly varying grades, but the effects of heating 
 the motor and destroying the exhaust valves are too seriously 
 objectionable to admit of operating the motor in this manner for 
 a very long time, even if the large consumption of fuel is not a 
 consideration. 
 
 When the ignition is by a low-tension current from a con- 
 stant-speed generator, so that the intensity of the arc is always 
 the same, and there are no springs that will allow lag in the 
 separation of the contact points, the advancing and retarding of 
 the arc are exactly the same as for the jump spark (not the 
 timer). It will be remembered that the larger part of the ad- 
 vance and retard with the jump-spark system is in the position 
 of the timer, and not in the instant of the spark itself. 
 
 In one automobile motor no provision is made for changing 
 the time of ignition, but the arc is made stronger as the speed of 
 the motor increases. This is accomplished by increasing the 
 speed of the generator as the speed of the motor increases. The 
 ratio of the two speeds is kept constant, or nearly so. With 
 this arrangement, the advantage of slow speed and strong 
 
CONTROL OF POWER AND SPEED 155 
 
 pull cannot be secured by retarding the spark and opening the 
 throttle. A slow speed of rotation and a strong pull are often 
 extremely desirable for a short time. 
 
 89. Combined Hand Control and Governing. When a motor 
 is entirely controlled by hand (and foot) there are times when 
 it is impossible for the operator to perform all the operations 
 quick enough to prevent the motor from racing, as in the case 
 of suddenly disengaging the clutch and applying both hand and 
 foot brakes to avoid an accident, or when it is necessary to re- 
 lease the brakes, throw on the power and steer the car quick 
 enough to get away from a dangerous position. For this reason, 
 especially to avoid racing of the motor, and in order to provide 
 means by which a uniform speed can be easily maintained on a 
 clear road, a governor is connected to the throttle or other fuel- 
 regulating device. The governor is found on many automobile 
 motors, to a less degree on launch motors, and sometimes on 
 stationary motors for hoisting, etc. Some motors are provided 
 with a connection between the clutch and throttle such that the 
 act of disengaging the clutch also partly closes the throttle. 
 This, however, does not keep down the speed of the motor when 
 the transmission gears are in neutral position and the clutch in 
 engagement. 
 
 A governor has, to a small extent, been applied to the timer 
 to adjust it in relation to the speed, but without very satisfactory 
 results. The governor for a timer should advance and retard it 
 in relation to both the speed and the amount of fuel supplied 
 for a charge or the degree of compression, instead of for the 
 speed alone. 
 
 The fuel governor is set, in the usual practice, to keep the 
 speed at the lowest at which the motor will run well, and to main- 
 tain that speed from friction load up to the maximum torque 
 capacity of the motor at that speed. When a higher speed is 
 wanted, the hand control is set for that speed, and the governor 
 maintains it as before. In other designs the governor ceases to 
 act as soon as the hand control is brought into action. This 
 latter method is hardly desirable for an automobile. An accel- 
 erator foot lever for opening the throttle wide and throwing the 
 
156 THE GAS ENGINE 
 
 governor out of action quickly is generally provided for sudden 
 speeding up of the motor, or for working it at its full torque 
 capacity and the highest speed it will take under the load. 
 
 Comparative Accuracy of Methods of Governing. 
 
 90. Speed Variation in Cut-Out-of-Charge Governing. By 
 
 the use of the cut-out mechanisms of the forms generally adopted, 
 and which have been described, the piston of a four-cycle, one- 
 cylinder, single-acting motor of the simpler type must make 
 eight strokes, corresponding to four revolutions of the crank 
 shaft, between the beginning of impulses when one charge only 
 is cut out of a series. 
 
 If the motor is working at nearly its full capacity, and con- 
 sequently cutting out an impulse only after several have occurred 
 in regular consecutive order, there will be a considerable drop 
 of speed following the missed explosion. And, on the other 
 hand, if the motor is running with little or nothing more than its 
 own frictional resistance to overcome, there will be several con- 
 secutive cut-outs, with a slowly decreasing rotative speed and then 
 a considerable rapid increase of speed when an explosion occurs. 
 
 The total variation of speed is not as great when working 
 against only the friction load as when delivering power up to 
 nearly the full capacity of the motor. The maximum speed of 
 the motor is reached shortly before the completion of the last 
 impulse stroke preceding a cut-out, and the minimum speed just 
 after the beginning of the first impulse stroke following the 
 cut-out. 
 
 The relative extent of the speed variation under light and 
 heavy loads can be shown mathematically with a close degree of 
 accuracy. In doing this it will be assumed, for convenience, 
 that the maximum speed is reached at the completion of the last 
 impulse stroke preceding a cut-out, and that the minimum speed 
 occurs just at the beginning of the next impulse stroke. These 
 assumptions do not vary from the true conditions enough or in 
 such a manner as to affect the result appreciably. The same 
 motor will be considered under both light and heavy loads. 
 
CONTROL OF POWER AND SPEED 157 
 
 It should be remembered that, in this method of governing, 
 every impulse acting on the piston is produced by the combustion 
 of a full charge. It will be assumed that all charges contain the 
 same amount of fuel; also that the resistance opposing the crank 
 shaft is constant. The assumption is also made that the speed 
 decreases uniformly during the time there are no impulses. This 
 is not strictly true, since the inertia effects of the reciprocating 
 parts and the variation of pressure against the piston cause a 
 variable rate of drop. The truth of the results is not affected by 
 this assumption. 
 
 The discussion refers to a single-cylinder, single-acting, four- 
 cycle motor governed in such a manner that the time interval 
 between explosions when there is a cut-out is never less than the 
 time corresponding to four revolutions of the crank, and is always 
 a multiple of four. 
 
 The following notation will be used : 
 
 N = any number of strokes of the piston not less than 12 
 and a multiple of 4; 
 
 H = the heat transformed into mechanical energy and 
 delivered to the piston each time a charge is burned 
 in the motor cylinder. A constant ; 
 
 W = the sum of the external work done plus the friction loss 
 
 in the motor, both during one stroke of the piston; 
 
 K.E = the kinetic energy given up by the flywheel and 
 
 other moving parts during the longest series of 
 
 consecutive inertia strokes of the piston. 
 
 When the motor is running on light load and there is only one 
 impulse stroke during AT" strokes of the piston, then 
 
 and since there are N 1 inertia strokes during the AT strokes 
 of the piston, 
 
 K.E = (N - 1) W = (N - 1) ~ (Light load.) 
 
158 THE GAS ENGINE 
 
 Again, when the motor is carrying a heavy load and there is 
 ly one cut-out during N strokes of the pis 
 impulses during the N strokes. Therefore 
 
 only one cut-out during N strokes of the piston, there are 1 
 
 4 
 
 and since the maximum number of inertia strokes is 7 when there 
 is only one cut-out during N strokes, 
 
 K.E h = 7 W h = 7 (- - l) ^ - (Heavy load.) 
 
 \4 J N 
 
 The decrease of speed is nearly proportional to the amount of 
 kinetic energy given up for the amount of speed variation that 
 occurs in a governed motor. The ratio of the kinetic energy 
 given up in the first case (light load) to that given up in the 
 second case (heavy load) is 
 
 K.E N 
 
 K.E h 
 
 When N is given its minimum value of 12, corresponding to 
 one impulse and two cut-outs for K.E. and to two impulses and 
 one cut-out for K.E h , this ratio becomes yj = .786. 
 
 And since the speed variation in each case is practically pro- 
 portional to the kinetic energy given up, the speed variation at 
 the light load is only about 79 per cent of that at heavy load, 
 or the variation at heavy load is about 1.27 times that at 
 light load. 
 
 If N= 40, corresponding to one impulse and nine cut-outs 
 for K.E and to nine impulses and one cut-out for K.E h , then 
 the ratio of the kinetic energy given up during the 39 inertia 
 strokes with the light load to that given up during the 7 inertia 
 strokes with the heavy load is f f = .619. 
 
 In this case the speed variation at light load is only about 
 62 per cent as great as at heavy load, or the heavy load variation 
 of speed is about 1.62 times that at light load. 
 
CONTROL OF POWER AND SPEED 
 
 159 
 
 The nature of th& speed variations for consecutive strokes of 
 the piston is shown in the diagrams, Figs. 73 and 74, for N = 40. 
 The diagrams are drawn to the same scale. The diagrams do 
 not show the minor effects of compression, expansion, reciprocat- 
 ing parts, etc. 
 
 Beginning at the left-hand side of Fig. 73, which is for the 
 light load, the straight line inclined downward toward the right 
 indicates a uniform decrease of speed. The time for the governor 
 to act is at the completion of the 2d, 6th, loth, . . . 34th, 38th, 
 
 1 impulse and 9 cutouts during 40 Strokes of Piston 
 
 
 
 \ 
 
 1 
 
 f 
 
 
 
 * 
 
 jt 
 
 , 
 e 
 
 *-~ 
 
 a 
 
 *-*, 
 
 at< 
 
 - 
 ) '( 
 
 -^ 
 \ 
 
 - 
 li 
 
 --. 
 rli 
 
 . 
 
 t.l 
 
 --. 
 le 
 
 
 
 JOV 
 
 -^. 
 > -ti ( 
 
 -., 
 
 > n 
 
 -^ 
 
 1 S 
 
 "*- . 
 
 <> 1 
 
 -^ 
 t 
 
 "-- 
 
 -^- 
 
 - -^ 
 
 *-* 
 
 
 
 
 
 
 
 /""" " 
 
 -^.. 
 
 
 
 *"* 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 -- 
 
 . 
 
 
 
 36 38 2 4 
 
 6 8 10 12 14 16 18 20 32 
 Strokes 
 
 24 26 28 30 32 
 
 34 36 
 
 38 40 42 
 
 FIG. 73. 
 
 etc., strokes (suction or charging strokes). The speed has fallen 
 below that at which the governor cuts out when the inclined line 
 crosses the vertical line that represents the beginning of the 38th 
 stroke to the left of the zero. A charge is therefore taken in and 
 compressed during the two strokes preceding the impulse stroke 
 that begins at the zero division. The speed is increased from 
 A to B during the impulse stroke, and then falls uniformly during 
 the following 39 inertia strokes and reaches a minimum at the 
 end of the 4oth stroke. The speed has fallen below the cut-out 
 line at the end of the 38th stroke, so that the inlet valve is opened 
 for this charging stroke. The impulse given during the 4ist 
 stroke brings the speed up to the maximum again. 
 
 Now taking up Fig. 74 for a heavy load, the last impulse of a 
 consecutive series of impulses increases the speed from N to P 
 during stroke i according to the numbering on the diagram. 
 The speed then falls off uniformly, as indicated by the inclined 
 straight line, but at the beginning of the third stroke, as repre- 
 
i6o 
 
 THE GAS ENGINE 
 
 sented by vertical line 2, it is still above that at which the governor 
 cuts out. The charge is therefore cut out, and the piston must 
 make, in all, seven inertia strokes during which the speed falls 
 to R before another impulse begins. Impulses are then given 
 during every fourth stroke, beginning with the gih and ending 
 with the 4 1 st. The speed has now again reached the same value 
 
 9 impulses and 1 cutout during 40 Strokes of Piston 
 
 peed 
 
 I ove which 
 
 governo 
 
 out 
 
 f 
 
 10 12 14 16 18 20 22 24 26 28 30 32 34 30 38 40 42 44 46 48 
 Strokes 
 
 FIG. 74. 
 
 as at P, and the cut-out is repeated. The speed change from A 
 to B, Fig. 74, and that from P to R } have a ratio of f f as has 
 been calculated. 
 
 While the greatest total speed variation comes with the heavy 
 load, the highest rate of variation occurs with the light load. The 
 highest rate of variation takes place during the impulse stroke 
 with both the light and heavy load. The energy stored in the 
 moving parts during each impulse stroke is the difference between 
 that given to the piston by each explosion and that abstracted for 
 external work and friction in the motor. It is represented by the 
 expression 
 
 Heat energy stored in moving parts! 
 of motor by each explosion J 
 
 The values of W for the two cases already considered are 
 
 w = 
 
 N 
 
CONTROL OF POWER AND SPEED 161 
 
 Since N is never less than 12, the value of W^ is always less 
 than that of W h . Therefore H W Q is always greater than 
 H W h , which indicates that there is more energy stored in the 
 moving parts during the impulse with the light load than with 
 the heavy load. 
 
 Applying this to the concrete case in which N = 40 gives: 
 
 Energy stored in moving parts during one "1 . 
 impulse when there is but one impulse [ = H 
 
 40 40 
 
 AQ 4O 
 
 during the 40 strokes 
 
 Energy stored in moving parts 
 during one explosion when 
 there is but one cut-out dur- 
 ing 40 strokes 
 
 These results show that the increase of speed during one 
 impulse stroke with the light load is f f , or about 1.25 times that 
 of the corresponding increase with the heavy load. 
 
 91. Speed Variation with Throttling Governor. In this case 
 the speed variation is very much less than by cutting out whole 
 charges. The piston receives its impulses at regular intervals, 
 so there is no long period of inertia strokes. The speed curves 
 for both light and heavy loads are of the same nature. The 
 accuracy of speed depends on the inertia of the rotating parts. 
 
 92. Uniformity of Speed in Two-Cycle Governed Motor. - 
 Since the impulses come twice as often in a two-cycle motor as 
 in a four-cycle one when both have the same speed of rotation, 
 the governing is naturally more accurate. This is most marked 
 in motors with only one combustion chamber and one piston. 
 
CHAPTER V. 
 
 COOLING THE MOTOR. 
 
 93. General. It has already been stated that some means of 
 cooling the parts of the motor with which the hot gases come in 
 contact is necessary to prevent their overheating. 
 
 The three methods adopted are water cooling, oil cooling, 
 and air cooling. 
 
 When a charge is burned in a motor, part of the heat is 
 abstracted by the enclosing walls, part is transformed into 
 mechanical energy by driving out the piston, and the remainder 
 passes out with exhaust gases. The only useful part as far as the 
 motor is concerned, is that transformed into mechanical energy. 
 
 The cooler the confining walls, the greater the amount of heat 
 abstracted from the gases by them. The transformation of the 
 heat of the fuel into mechanical energy is therefore the more 
 efficient the hotter the walls. From this viewpoint it is therefore 
 desirable to have hot walls. 
 
 On the other hand, the cooler the walls the higher the pressure 
 to which the compression of the charge can be carried before 
 ignition occurs by the heat due to compression when the air and 
 fuel are mixed before compressing, as is the practice in all 
 modern motors using gas or vapor fuel and in most oil motors. 
 The Diesel oil motor is a decided exception to the general prac- 
 tice. The efficiency of heat transformation is higher the higher 
 the compression. On this basis cool walls are desirable. 
 
 There have been many tests on water-cooled motors reported 
 in which it is pointed out that when the cooling water is kept at 
 or near the boiling point, the efficiency is higher than when a 
 bountiful supply of cold water is circulated through the water 
 jacket. But these tests all seem to have been .made without 
 changing the compression pressure in any of the motors during 
 the test when the change was made from hot to cold water. If 
 
 162 
 
COOLING THE MOTOR 163 
 
 the compression pressure had been carried higjier for the cold 
 water than for the hot, as can be done by lengthening the con- 
 necting rod so as to decrease the ratio of the volume of the com- 
 pression space to that of the displacement by the piston per 
 stroke, the results would have been different. How far different 
 would depend on how much higher the compression pressure 
 could be carried with the cold-water jacket without producing 
 ignition before the completion of the compression stroke. 
 
 The capacity of the motor is lower the hotter the cylinder and 
 combustion chamber. The hot metal of the walls heats the 
 charge and expands it before the compression stroke begins and 
 while the inlet port is still open. This is especially true when 
 the inlet port is located so that the cool incoming charge will 
 strike the hot exhaust valve and cool it. The expansion of the 
 mixture by heat reduces the weight of the charge and therefore 
 also reduces the power that is developed from it. The result is 
 that motors working with hot cylinders develop less power per 
 cubic foot of piston displacement per minute than those with 
 cooler cylinders. In other words, of two motors having the same 
 diameter of piston and length of stroke, and running at the same 
 speed of rotation, but one having a hot cylinder and the other a 
 cool one, the latter will develop more power. 
 
 The distortion and deterioration of the parts in the neighbor- 
 hood of the combustion chamber' by heat, and the difficulty of 
 sufficiently lubricating the hot parts, both limit the degree of 
 hotness at which the motor will operate satisfactorily. 
 
 94. Air Cooling. Air cooling has been found entirely satis- 
 factory for small motors such as are used on motor cycles and air 
 ships. The movement of the vehicle generally brings enough 
 air in contact with the external portions of the heated parts to 
 keep them cool enough to operate. But when a motor cycle is 
 moving in the same direction as a strong wind on a hot day up 
 a long grade, the motor is apt to become rather hot. 
 
 Air-cooled automobile motors up to ten -horsepower capacity 
 per cylinder in four- and six-cylinder designs have been oper- 
 ated successfully for several years. In the multi-cylinder motor 
 a fan is provided to create a draft against the radiating pro- 
 
1 64 THE GAS ENGINE 
 
 tuberances of the heated part. In some designs the fan merely 
 causes a circulation of air through the space enclosed by the hood 
 that covers the motor. In others the heated parts and their pro- 
 tuberances are surrounded by a casing which encloses a compar- 
 atively small space so as to form an air jacket between the casing 
 and cylinder, etc. A current of air is forced through the jacket 
 by a blower or fan. 
 
 When the circulation of air is poor around the cylinder of an 
 air-cooled motor, the metal becomes hot enough to glow dis- 
 tinctly in moderate darkness. The motor runs successfully 
 at this temperature, but the continuation of such heating injures 
 the valves, etc., and very copious lubrication of the cylinder is 
 necessary with an oil that will stand high temperatures before 
 burning or evaporating. . 
 
 95. Water Cooling. By far the greater proportion of auto- 
 mobile motors, practically all .small stationary motors and all 
 large ones, launch motors, etc., are cooled by water or some 
 other liquid. 
 
 In the more usual practice of cooling the cylinder, water is 
 passed through the water jacket and then out through a waste 
 pipe or to a cooler from which it returns to the motor again. In 
 at least one motor, however, the method is different. In it the 
 water is kept at a constant level in the jacket space of the hori- 
 zontal cylinder, so as to surround about three-quarters of the 
 cylinder, and there is no water outlet from the water jacket. 
 As the water is gradually vaporized, the vapor passes out of the 
 jacket through a pipe that leads it to the inlet of the motor. 
 The water vapor mingles with the air that is entering the cylin- 
 der and is carried in with it. 
 
 In the true circulating system of cooling, the water passes 
 repeatedly from the motor to the cooler and back to the motor, 
 and so on. 
 
 Whether the circulating system or the waste system of the 
 cooling water shall be adopted for a motor naturally depends 
 on conditions separate from the motor itself. On a launch the 
 water is allowed to flow overboard, while on an automobile it 
 is carefully retained and cooled. 
 
COOLING THE MOTOR 165 
 
 It is quite common practice to pass the waste water into the 
 exhaust pipe on stationary and launch motors. This serves 
 the triple purpose of cooling the pipe, silencing the exhaust 
 to some extent, and of preventing serious explosions in the 
 exhaust pipe and its connections, in case some of the com- 
 bustible mixture is passed unburned through the motor into 
 them. 
 
 Thermal circulation, in which the heat from the cylinder walls 
 is utilized to move the water in the circulating system, is the 
 simplest and most economical method. In the thermal system, 
 the top level of the water in the cooling apparatus is higher than 
 the top of the jacket space of the motor, and the lower level of 
 the water in the cooler is above the bottom of the jacket space. 
 A pipe, or passage, carries the water from the top of the jacket 
 space to the upper part of the water in the cooler. The open- 
 ing of this pipe into the cooler must be below the surface of the 
 water, at least the lower part of the opening must be lower than 
 the water level, and the pipe, should have an upward incline, 
 or be vertical, from the motor to the cooler, so that the water 
 always rises as it passes through it from the former to the latter. 
 There should be no downward bends in the pipe. The pipe 
 from the lower part of the cooler to the lower part of the jacket 
 space should either be inclined downward from the cooler or 
 descend vertically, so that the water will always descend on its 
 way from the cooler to the motor. 
 
 The operation of the thermal system depends on the fact that 
 hot water has less density, or weighs less per cubic foot, than 
 cold water, and therefore always tends to rise to the surface. 
 The hot water rises to the top of the jacket space and flows up 
 through the pipe to the cooler, while the cold water from the bot- 
 tom part of the cooler flows through the pipe to the bottom of 
 the jacket space, thus maintaining circulation. 
 
 If the water in the cooler falls below the opening of the pipe 
 from the motor jacket space to an appreciable extent, the cir- 
 culation will stop. 
 
 In stationary-motor practice the cooler can be a tank, a barrel, 
 a reservoir, or any simple form of vessel that will retain the water. 
 
1 66 THE GAS ENGINE 
 
 since it can be made large enough to have ample exposed water 
 surface and enough of its own outer part exposed to the air to 
 cool it. This is also generally true of portable and, to a con- 
 siderable Extent, of semi-portable motors. 
 
 A radiator is used for cooling the circulating jacket water in 
 automobiles. It is placed at the extreme front of the car in 
 usual practice. Numerous designs of radiators are used. The 
 object sought in all the correctly designed ones is to present as 
 large an exterior cooling surface to the air and as large an in- 
 terior contact surface to the water as possible for the amount of 
 water carried, and at the same time to have rapid passage of air 
 over the radiating or exterior surface of the cooler. It is also 
 extremely desirable to keep the weight of the radiator as low as 
 possible. 
 
 Copper, brass, and bronze are the materials almost univer- 
 sally used for automobile radiators. Copper, or its alloys, is 
 most suitable on account of its combined high capacity for 
 conducting heat, ease of working to form and of soldering, and 
 toughness. 
 
 A fan is generally used for drawing air over and between the 
 external surfaces of the radiator. When the fan is a separate 
 piece of the apparatus, it is generally placed just back of the 
 radiator. The tendency of modern practice is to utilize the arms 
 of the flywheel of the motor for a fan by making them vane- 
 shaped. In such cases the motor is completely enclosed by a 
 tight hood and a bottom pan, so that the suction of the flywheel 
 at the rear of the motor draws air in through the radiator at the 
 front, allows it to circulate around the motor, and then discharges 
 it under the body of the car. 
 
 The aid of a fan is not generally required in freezing weather, 
 but it becomes an absolute necessity in hot weather. Without 
 it an automobile traveling up a long grade together with a breeze 
 in the same direction and at the same speed, and in a hot sun, 
 will have the cooling water boiling in a short time. 
 
 A circulating pump for forcing the water to circulate rapidly 
 through the cooling system is generally used - in automobile 
 practice, especially in the larger, high-powered cars. The small 
 
COOLING THE MOTOR 167 
 
 quantity of cooling water carried (often not more than three or 
 four gallons for a forty-horsepower motor) makes it necessary to 
 circulate the water rapidly. This is largely due to the fact that 
 the water space in the radiator is so limited that but a very small 
 part of the water is contained in its very narrow passages, hence 
 the circulation must be more rapid than thermal action will 
 produce. 
 
 The pump for circulating the water is interposed in some 
 part of the circuit, generally in the pipe between the bottom of 
 the radiator and the bottom of the jacket space. The pump 
 is generally of the rotary type, since this form will deliver a large 
 quantity of water when of small size and light weight. Two 
 types are used, centrifugal and positive action. The centrif- 
 ugal pump creates a pressure in a measure proportional to its 
 speed of rotation, and the amount of water that flows depends 
 on the freedom of its passage through the circuit. The positive- 
 action pump is of the nature of a force pump. At every revo- 
 lution it delivers a fixed and constant volume of water, and the 
 pressure is proportional to the resistance of the flow through 
 the circuit. This is true provided the pump has no leakage 
 between the parts that work together and give the impulse to 
 the water. There generally is considerable leakage in this 
 class of pumps as used on automobiles. The centrifugal type 
 has come to be used more generally in automobile practice. It 
 is the simpler form, and does not depend on the absence of leak- 
 age for its satisfactory operation. 
 
 In launches, the reciprocating plunger type of circulating pump 
 for the cooling water is more commonly used than the rotary. 
 The reason for this selection does not seem plain when the pump 
 is placed below the level of the water in which the boat floats. 
 It is, of course, a simple and inexpensive form of pump, and 
 can be driven by a crank or an eccentric instead of gear 
 wheels. 
 
 96. Water-Cooled Pistons and Valves. In the smaller sizes 
 of motors the heat is conducted away from the piston and valves 
 by the parts of the cylinder with which they come in contact. In 
 single-acting motors, the piston is also cooled by the external air 
 
1 68 THE GAS ENGINE 
 
 when the piston is exposed to the air, as in the usual forms of 
 single-acting stationary motors. 
 
 In large, or even in medium-sized motors, the heat is not 
 carried away with sufficient rapidity in this manner to keep the 
 parts cool enough for operation. The head of a 20 inch diameter 
 piston will glow with heat after the motor has been on a heavy 
 load for some time, and the exhaust valve becomes hot and 
 distorted so as to leak. The hot gases passing by it also destroy 
 the smoothness of the bearing surface that comes against the seat 
 when the valve is closed. 
 
 Water-cooling the piston becomes especially necessary in 
 double-acting motors, since the piston receives heat on both faces 
 and none of it is exposed to the external air. 
 
 The usual method of cooling the piston of a double-acting 
 motor is to pass water in through a pipe in the hole of a hollow 
 piston rod. The piston is also made hollow, and the space so 
 divided that the water upon entering it flows around so as to cool 
 its entire surface and then flows out through the hollow piston 
 rod in the space not occupied by the pipe that carries the water 
 in. A pump or a head of water is necessary to force the water 
 through the piston and piston rod. 
 
 The cooling of the exhaust valve with water is done in a manner 
 similar to that for the piston. 
 
 97. Oil-Cooling the Motor. Oil can be used in the same man- 
 ner as water for cooling the motor by circulating it through the 
 jacket space. This has been demonstrated in regular service on 
 a considerable number of motors for several years. 
 
 For motors that are exposed to the cold when not in operation 
 the use of oil for cooling has great advantages over water. 
 Freezing of the water will burst the jacket shell and other parts. 
 Any failure to drain it off completely may be the indirect cause 
 of broken pipes and radiator. If there are any pockets that do 
 not drain easily, this failure is apt to occur. 
 
 When oil is used for cooling, the value of the oil makes a circu- 
 lating system necessary, A radiator and circulating pump can 
 be used as for water. 
 
 "Oil-cooled" is often erroneously applied to air-cooled motors 
 
COOLING THE MOTOR 169 
 
 under the supposition that so much cylinder ail is required to 
 lubricate the cylinder and piston that it has an appreciable cooling 
 effect. 
 
 98. Gaskets and Packing Materials. A gasket is a piece of 
 comparatively soft material, generally thin and flat, placed between 
 two harder surfaces, generally metallic, for making a tight joint. 
 
 Where the temperature is high, as where the parts are heated 
 by exhaust gases, the gasket must be of a material that will not 
 burn, and should also be soft and thick enough to allow for warp- 
 ing of the connected parts. Asbestos woven into a sheet, together 
 with a net of small copper wires for strengthening, is much used. 
 The material can be easily cut to the form needed. Asbestos 
 covered with sheet copper and made up into forms to be used 
 (rings, ovals) is convenient and good. 
 
 When gasoline or naphtha comes in contact with the gasket, as 
 in an inlet pipe, some material that is not affected by the naphtha 
 or gasoline should be used. Rubber will not do on account of 
 the softening action of the gasoline or naphtha, but leather, wood 
 fiber, paper, lead, and soft copper are suitable. 
 
 For joints in the cooling-water connections, any of the last 
 mentioned materials, or any good steam gasket material, will 
 answer if there is no oil or other substance in the water that will 
 attack them. Rubber and rubber composition should not be 
 used when oil is present, as in a non-freezing mixture, or when 
 oil alone is used as in oil-cooled motors. 
 
 The pipe for the liquid fuel is generally very small. Lead or 
 soft-copper rings serve well in it for packing, but the lead ring 
 should be quite thin so that there is not enough material to be 
 squeezed out so as to close the passage. Vulcanized wood fiber 
 does well here. The small joints are generally ground to a fit. 
 If a ground fit in the fuel-pipe connection cannot be made tight 
 without packing or some other filling material, a thin coating of 
 cake soap or some rubber cement put between the ground sur- 
 faces will generally stop a leak. 
 
 When the joint remains dry, and especially if it is highly 
 heated in service, it can be prepared for easy separation by coating 
 one side of a non-metallic gasket with powdered or flake graphite 
 
170 THE GAS ENGINE 
 
 (plumbago, black lead) and the other side with varnish. The 
 varnished side will adhere so as to hold the gasket in place, but 
 the graphite-coated side will separate readily from the surface 
 that was pressed against it. 
 
 99. Pump Packing. Some fibrous material is generally 
 used for packing the circulating pump. Flax (tow) is probably 
 best for a water pump, but cotton wicking covered with graphite 
 grease is good. The latter, or prepared steam packing (without 
 any rubber), does well for the circulating pump of an oil-cooled 
 motor. 
 
CHAPTER VI. 
 
 LUBRICATION OF MOTOR. 
 
 loo. Oils and Methods of Applying. Copious lubrication of 
 the piston of an internal-combustion motor is an absolute neces- 
 sity. In the absence of lubrication, the rubbing surfaces of the 
 piston and the bore of the cylinder become dry and abrade 
 each other, and may even seize together. As a result the motor 
 loses power and finally stops. Oil is used for lubricating. 
 
 The oil to be most suitable must withstand a high temper- 
 ature without decomposition or rapid vaporization, and when 
 finally evaporated and burned must leave a minimum deposit 
 on the walls of the cylinder and piston, valve stems, and ignition 
 apparatus. It must also be free from acids that act on the 
 metal of the motor. Most of the oils used are thin (not vis- 
 cous) and flow readily, especially those for small motors. In the 
 latter it is often desirable to use the same oil for the bearings 
 on the crank shaft as for the piston. 
 
 One of the simplest methods of lubricating the piston and 
 crank-shaft bearings of a vertical motor is the splash system. 
 In it the enclosed crank case is kept partly filled with oil to such 
 a level that the rotating parts strike it and splash it up into the 
 bore of the cylinder and against the piston. The latter is amply 
 lubricated by this method. 
 
 In order to prevent too copious lubrication of the piston by 
 splashing in this manner, a splash plate is sometimes placed 
 across the lower end of the cylinder between it and the crank 
 case. The splash plate has a slot in it only large enough to 
 allow the movement of the connecting rod. No oil is fed in 
 through the cylinder walls in the best practice when the splash 
 system is used. The lowest piston ring is sometimes beveled on 
 the lower part of the periphery so that the oil will pass up by it on 
 the downstroke of the piston. The upper side is left with a 
 
 171 
 
1/2 
 
 THE GAS ENGINE 
 
 FIG. 75. 
 
 Axial Section of Cylinder of Vertical Gas Engine. Four-cycle, Single-Acting, 
 Water- Cooled. Oil Well at Bottom of Cylinder. Auxiliary Exhaust Port. 
 
 A. Mixture inlet. 
 
 B. Exhaust passage. 
 
 C. Exhaust pipe connection. 
 
 D. Auxiliary automatic exhaust port. 
 
 E. Jacket-water inlet. Outlet at top of 
 
 jacket space not shown. 
 
 F. Annular oil well into which piston 
 
 dips. 
 
 G. Piston. 
 
 H. Combustion part of cylinder. 
 
 J. 
 K. 
 M. 
 N. 
 O. 
 P. 
 
 Q- 
 
 Opening for relieving compression 
 during first part of compression 
 stroke when starting. Ordinarily 
 closed by valve. 
 
 Connecting rod. 
 
 Water-jacket space. 
 
 Flywheel. 
 
 Inlet valve. 
 
 Exhaust valve. 
 
 Closing spring for inlet valve. 
 
 Closing spring for exhaust valve. 
 
LUBRICATION OF MOTOR 
 
 sharp corner so that the oil will be carried up on the upstroke. 
 This practice does not seem necessary, however. It is not 
 found in very many motors. 
 
 Forced lubrication is a still more certain way of securing posi- 
 tive lubrication of the parts. In this system a small pump is 
 used to take the oil from the bottom of the crank case and force 
 it through pipes or passages in the case leading to the bearings 
 and thence through the hollow crank shaft and passages in the 
 cranks to the crank pins and then through the hollow connect- 
 ing rod up to the piston pin or wrist pin. The oil escapes through 
 the various bearings and runs back to the crank case to be 
 pumped through the system again. Both reciprocating plunger 
 and rotary pumps are used for circulating the oil. Positive-acting 
 rotary pumps are more suitable here than for water circulation, 
 since the copious lubrication prevents rapid wear and conse- 
 quent leakage. 
 
 Ring oiling of the crank-case bearings that support the crank 
 shaft is frequently adopted. The usual method is to make the 
 bearing with an oil reservoir beneath it, and to cut away part of 
 the top of the bearing in order to hang a ring over the shaft so 
 that its lower part dips into the oil in the reservoir. The weight 
 of the ring resting on the top of the shaft causes the ring to turn 
 when the shaft is rotating, but at a slower rate. The rotation 
 of the ring carries oil up to the shaft, so that the bearing is lubri- 
 cated as long as there is enough oil in the reservoir for the ring 
 to touch it. 
 
 In horizontal motors oil is fed in at the top of the cylinder. 
 This is the only way the oil is supplied in open-frame motors. 
 But when the crank case is enclosed there is some lubrication 
 of the piston by the oil that flies from the crank and connecting 
 rod. 
 
 When there is no pump, as for forced lubrication, the oil must 
 be supplied by some sort of a lubricator which gradually delivers 
 oil to the motor. 
 
 The amount of oil required per stroke of the piston of a motor 
 is in a measure proportional to the rate at which the motor is 
 working. More oil is required for a heavy load than for a light 
 
1/4 THE GAS ENGINE 
 
 one when the speed of the motor is constant. The oil required 
 for variable-speed motors is approximately proportional to both 
 the speed and the load. The refinement of lubricating in propor- 
 tion to the work per stroke does not seem to have been attempted. 
 It is doubtful as to its being worth while. But practically all 
 the lubricators for variable-speed motors, except the simplest 
 gravity types, supply the oil more or less nearly in proportion to 
 the speed of rotation. When the splash system is used, it is 
 not so important that the rate of feed of the oil shall be pro- 
 portional to the speed. But when the motor works steadily on a 
 heavy load for a long time, the rate of gravity feed that is suit- 
 able for a light load is not rapid enough for a heavy one. 
 
 101. Lubricators. There are four distinct types of lubri- 
 cators used on internal-combustion motors, as classified accord- 
 ing to the method of delivering the oil. They are: 
 
 Gravity feed; 
 
 Mechanical oil supply and gravity delivery; 
 
 Compression feed; 
 
 Positive mechanical feed. 
 
 The gravity-feed lubricators that are used on gas and oil 
 motors are principally of the adjustable sight-feed type. The 
 rate of flow of the oil is adjusted by a needle or cone-point regu- 
 lator, and is observed through the glass sight below the point 
 from which the oil drops. The gravity lubricator can be used 
 where there is no compression resistance to feed against. It 
 can be used for the crank shaft of an enclosed crank case, four- 
 cylinder vertical motor of the usual type in which two of the 
 pistons move upward in unison while the other two move down- 
 ward, since neither compression nor partial vacuum is produced 
 in this form of motor. 
 
 The mechanical-supply and gravity-delivery lubricator was 
 used on the early horizontal motors of the Otto type for lubricating 
 the piston. It still finds considerable application to this style of 
 motor. In it a mechanically driven part, generally rotary, dips 
 into a reservoir of oil and carries some of it up over the open 
 end of a tube which extends down through the cylinder wall to 
 
LUBRICATION OF MOTOR 175 
 
 the bore of the cylinder. Some of the oil either drops or is scraped 
 off the rotating part as it passes over the top of the tube, and flows 
 down through it to the piston. If the pressure due to a leaky 
 piston blows the oil up out of the tube, it is caught in the cup or 
 reservoir and again carried up by the rotating part. 
 
 In several forms of motor with an enclosed crank case the air 
 or mixture in the case is alternately compressed and expanded. 
 The gravity-feed lubricator will not deliver oil into the com- 
 pressed air. 
 
 The compression-feed lubricator is applicable to such motors. 
 In some of its forms a pipe connects the crank case with the air 
 space above the oil in the lubricator reservoir. The pipe ter- 
 minates in a check valve in the lubricator. When the air is 
 compressed in the crank case, some of it is forced into the air 
 space of the lubricator and retained there under pressure by the 
 check valve. When the pressure in the crank case falls as the 
 pistons recede, the compressed air in the lubricator forces the oil 
 out through the openings for that purpose. The oil is fed out and 
 regulated as in a sight-feed gravity lubricator, except that the 
 orifice can be at or above the level of the oil provided it is con- 
 nected with the body of the oil by a passage that opens below its 
 surface. If the compressed air is not released from the lubricator 
 when the motor stops, it will continue to feed oil out till the 
 pressure falls. A release valve is generally provided. It is 
 opened by a pressure of the finger when the motor is stopped. 
 
 Some of the types of single-acting motors in which the air is 
 alternately compressed and expanded in the enclosed crank case 
 are: single-cylinder motor; two-cylinder opposed motor, with the 
 cylinders on opposite sides of the crank shaft and the cranks 
 1 80 degrees apart, so that the pistons alternately approach and 
 recede from each other; two-cylinder, twin-cylinder motors, in 
 which the cylinders are side by side and the pistons move in 
 unison toward and away from the crank shaft. 
 
 The positive-feed lubricator in one of its forms has a number 
 of small plungers and corresponding cylinders or pipe ends, one 
 for each outlet of the lubricator. The lower ends of the plungers 
 and the cylinders are submerged in the reservoir of oil. The 
 
1/6 THE GAS ENGINE 
 
 plungers are consecutively lifted by a rotating part, and oil flows 
 into the cylinder beneath the plunger through a small hole in the 
 side of the oil cylinder. The plunger is then released and a 
 spring snaps it down suddenly. The side orifice of the cylinder 
 is closed as the plunger passes it. The descent of the plunger 
 forces the oil into a tube which carries it to the part to be lubri- 
 cated. There are no valves in the device for forcing the oil out. 
 The plunger-lifting part of the lubricator is driven by the motor 
 at a speed proportional to that of the motor. The amount of oil 
 fed to the motor is therefore approximately proportional to the 
 speed of rotation of the motor. 
 
 Practically all mechanically driven lubricators deliver oil at a 
 rate approximately proportional to the speed of the motor. 
 
 Slow-moving mechanically driven plunger pumps with valves 
 are used in some of the other positive-feed lubricators. 
 
CHAPTER VII. 
 DISPOSAL OF EXHAUST GASES. 
 
 102. Precautions. Since the exhaust gases from an internal- 
 combustion motor are hot, and since combustible mixture may 
 be mingled with them at times, the pipes or passages through 
 which the exhaust is carried to the atmosphere must be so located 
 and protected as not to injure anything by their heat, and must 
 be strong enough to resist the pressure of explosions in them. It 
 is often desirable to carry the exhaust from a small stationary 
 motor out through a chimney or flue of a building in which the 
 motor is located. In such a case the exhaust pipe must be 
 extended the full length of the flue so that the gases will be 
 discharged directly into the atmosphere. If the exhaust is dis- 
 charged into the masonry flue and an explosion occurs in it, the 
 flue is apt to be wrecked. 
 
 The discharge of a spray of water, as cooling-jacket water, 
 into the exhaust pipe reduces its temperature and lessens the 
 liability of explosions. This is not generally practiced for 
 stationary motors of small size, however. If there is much 
 sulphur dioxide (SO 2 ) in the exhaust gases, cooling with water 
 causes destruction of metal pipes by chemical action. 
 
 The exhaust should never be discharged into a room even for a 
 short time. A small quantity of the gases will cause headache, 
 and a large quantity asphyxiation. There is no warning odor, 
 and fainting is apt to occur before the danger is realized. 
 
 When too rich a mixture is used in a gasoline motor, the exhaust 
 gases will also cause the eyes to suffer by smarting and pain. 
 
 The danger is greatest in heavy, damp weather. 
 
 103. Silencing the Exhaust. The pressure of the gases in 
 the cylinder of an internal-combustion motor is still high enough 
 when the exhaust valve opens to cause them to escape with a 
 loud explosive sound, except in compound motors or others of 
 
 177 
 
1/8 THE GAS ENGINE 
 
 unusual design in which the expansion is carried out to almost 
 atmospheric pressure. Some provision is generally made for 
 deadening or silencing the sound of the exhaust. The apparatus 
 for this purpose is generally known as a silencer or muffler. 
 
 An efficient muffler not only deadens the noise of the exhaust, 
 but also offers a minimum resistance to the escape of the gases. 
 Any resistance to the escape of these gases causes a back pressure 
 against the piston of the motor during the exhaust stroke, or 
 against the piston of the pump that forces in the new charge in 
 two-cycle motors, and thus reduces the efficiency of the motor and 
 decreases the amount of power that it will develop. 
 
 104. Subterranean Mufflers or Silencers. For stationary 
 motors, the exhaust is generally discharged into a buried tank 
 or a pit when ground space is available. The gas expands to a 
 low pressure in the receptacle and then escapes to the atmos- 
 phere through a comparatively small pipe or opening. 
 
 For very large motors a pit or well is generally excavated and 
 used in the manner just described. 
 
 The noise is more completely deadened by filling the well with 
 loose broken stone, coarse cinders, slag, etc. 
 
 Since some of the combustible mixture is apt to pass through 
 the motor at times and on into the mufHer, and may be exploded 
 there by the hot gases of a subsequent discharge, the muffler 
 should be provided with means of relieving the pressure of the 
 explosion instantly, so that it may not be blown to pieces. A 
 hinged trap door of planks answers this purpose well for large 
 pits, and a large short pipe extending from the barrel or tank 
 to the atmosphere and closed by a relief valve at the top is 
 suitable for smaller sizes. The pipe from the motor to the 
 muffler should be strong enough to resist the pressure of these 
 explosions. 
 
 105. Exposed Muffler. When the muffler is not buried, it 
 is made of metal strong enough to resist the pressure of explo- 
 sions in it. If the exhaust pipe from the motor to the muffler is 
 long, there should be a relief valve either on the muffler or very 
 near it. 
 
 The exposed metal muffler has either a comparatively large 
 
DISPOSAL OF EXHAUST GASES 179 
 
 chamber, or a number of chambers, into which t the exhaust gas 
 is discharged and expanded and then passes out to the atmos- 
 phere. When the volume of the muffler is large in proportion 
 to the size of the exhaust pipe, the escape from the muffler is 
 often made through a single large pipe into the atmosphere. 
 But if the muffler is small, the discharge is made through a great 
 number of small orifices direct into the atmosphere. 
 
 One simple form of muffler consists of two comparatively 
 small enlargements of the exhaust pipe in series and a short 
 distance apart in the pipe. The gas expands in the first one 
 and then passes through the pipe between them into the second 
 for further expansion and then escapes through a length of pipe 
 to the atmosphere. 
 
 Another form of muffler has two or more pipes of different 
 diameter concentrically arranged in a nest, and the ends of all 
 the pipes are closed by one pair of heads. The exhaust is 
 received inside the smallest pipe and passes from it through a 
 number of small holes into the next larger pipe, and so on to 
 the outer tube or casing, and thence to the atmosphere direct or 
 through a pipe extension. 
 
 Still another form is made up of a number of thin metal disks 
 slightly concaved and placed on a pipe so that the convex side of 
 the first disk forms one end of the muffler and the concave side 
 of the second disk is placed toward that of the first one so that 
 the outer edges of the two press together. The convex side of 
 the third disk is placed next to that of the second one and 
 presses against it at the edge of the central hole, and so on for all 
 the disks. The pipe through the disk is stopped at one end 
 and has holes communicating with the spaces between the 
 concave sides of the disks. The exhaust gases pass from 
 the pipe through the holes into the enclosed spaces between the 
 disks and escape through the cracks between their outer edges. 
 
 1 06. Submerged Exhaust Pipe. On launches it is quite 
 common practice to submerge the end of the exhaust pipe in the 
 sea water. When this is done, the precaution should be taken 
 to give the pipe sufficient fall to prevent drawing the water up 
 into the motor by the contraction of the hot gases in the pipe 
 
180 THE GAS ENGINE 
 
 when the motor is stopped, or after an explosion in the exhaust 
 pipe. A check valve is often used to meet this and other con- 
 tingencies tending toward the same result. 
 
 107. Muffler Cut-Out. A cut-out or relief valve is commonly 
 used on automobiles. It is controlled by the driver, and is 
 opened when the maximum power that the motor will develop 
 is desired, as when climbing a grade or speeding up quickly. 
 
 1 08. Momentary Back Pressure. In a four-cylinder, four- 
 cycle motor whose impulses occur at equal time intervals and 
 whose valves have the usual setting, the exhaust valve of one 
 combustion chamber opens before the completion of the exhaust 
 stroke of the piston of one of the other cylinders. If the exhaust 
 pipes from the two combustion chambers (or from all of them) 
 are brought together into a single main passage near the motor, 
 this action of the exhaust will produce a momentary increase of 
 pressure in the latter combustion chamber unless the connections 
 between the single exhaust pipes and the main pipe are cor- 
 rectly made. This increase of pressure usually occurs during 
 the early part of the suction stroke of the piston and before the 
 inlet valve of the combustion chamber affected is opened. While 
 the action of the momentary back pressure on the piston is not 
 directly harmful in affecting the power of the motor, it does act 
 to reduce the amount of charge that is drawn into the cylinder. 
 This is because the exhaust valve closes while there is momen- 
 tary back pressure in the cylinder and thus retains more inert 
 gases of combustion than would be retained at atmospheric 
 pressure in the cylinder. 
 
 The proper method of connecting the individual exhaust 
 pipes to the main is to bring them nearly parallel with the latter 
 where they are connected, so that the Y formed will have a very 
 sharp angle between the branches. The discharge from one 
 combustion chamber will then have a tendency to draw the ex- 
 haust gases from the others by ejector action instead of pro- 
 ducing a back pressure as when the passages are at right angles 
 to each other at their connection. 
 
CHAPTER VIII. 
 STARTING AND ADJUSTING THE MOTOR. 
 
 109. Methods of Starting the Motor. There are three 
 methods in general use for starting an internal-combustion 
 motor. They are: 
 
 1. Rotating the motor by external power till a charge is 
 exploded in the usual manner and the motor then runs itself. 
 Small motors are "cranked" or otherwise turned by hand, and 
 large ones are driven from some source of mechanical power. 
 
 2. Starting the motor from rest by its own impulse. This is 
 generally done by exploding a charge of the combustible mixture 
 in the cylinder. An impulse is thus given the piston in much 
 the same manner as when the motor is running, so that it starts. 
 A less common method, although probably older, is to fire a 
 charge of gunpowder in the cylinder. 
 
 3. Driving by compressed air passed into the cylinder to act 
 on the piston in a manner similar to that of steam in steam 
 engines. 
 
 no. Relieving the Compression while Starting. The larger 
 sizes of motors intended to be started by hand are often con- 
 structed so that the compression can be cut down to a much 
 lower pressure for starting than is used during the regular oper- 
 ation of the motor. A very common method of doing this is to 
 have the Tegular cams move aside so as to bring the starting cams 
 into position for actuating the motor valves-. The starting cams 
 hold either the inlet valve or the exhaust valve of each cylinder 
 open during a portion of the compression stroke, so that part of 
 the charge that was drawn in during the preceding suction 
 stroke, in a four-cycle motor, is either forced back through the 
 inlet port or out through the exhaust port. When the inlet 
 valve is mechanically operated, the starting cam is applied to it, 
 but with an automatic inlet valve the starting cam can act only 
 
 181 
 
1 82 THE GAS ENGINE 
 
 on the exhaust valve. The latter has the seriously objectionable 
 feature of passing combustible mixture through the motor into 
 the exhaust pipe, and of the resulting danger of explosions in 
 the exhaust pipe and muffler. 
 
 In automobile motors the cam shaft is shifted to the starting 
 position by putting on the starting crank. The throwing of the 
 hand crank out of engagement when the motor starts on its own 
 impulses allows the cam shaft to come back to the running 
 position. Some of the large motors that are started by external 
 mechanical power are provided with means for relieving the 
 compression in the same general way as the small ones. 
 
 in. The preparations for starting a motor are practically the 
 same to a certain extent, whatever the method of starting. The 
 general preparations which are given immediately below do 
 not all apply to any one motor, but such of them as do apply to 
 any particular case should be made. It should be seen that : 
 Fuel is in the tank for motors that use liquid fuel; 
 The vent of the gravity fuel tank is not clogged; 
 The compression fuel tank is tightly closed; 
 Gas is in the supply pipe for motors using permanent gas. 
 This can be done by lighting a jet or burner connected 
 to the pipe at a point near the motor; 
 Lubricating oil is in all the lubricators; 
 The reservoir of a compression lubricator is tightly closed; 
 Grease cups are filled; 
 
 Cooling water is provided. If a stationary motor is located 
 in a. warm room and the cooling water is very cold, as 
 when it flows from mains or an exposed tank in winter, 
 it may be advisable to start the motor before turning on 
 the cooling water. This applies especially to gasoline, 
 naphtha, and alcohol motors. 
 Then: 
 
 Give the grease cups a turn to force grease into the bearings ; 
 Turn on the lubricating oil; 
 
 Disengage the clutch when one is used between the motor 
 and a load having considerable inertia or a load that 
 must be started slowly. 
 
STARTING AND ADJUSTING THE MOTOR 183 
 
 The operations following these depend so much on the kind 
 of motor and the method of starting that they must be differen- 
 tiated. 
 
 Starting by External Power. 
 
 112. Starting a Small Electrically Ignited Gas Motor by Crank- 
 ing. After such of the above preparations as apply to the 
 motor have been made: 
 
 Set the igniter in the late or retard position ; 
 
 Set the relief cam mechanism so that the compression will 
 be cut down when starting; 
 
 Turn on the gas, but only part way if there is no fuel valve 
 to prevent its flow from pressure pipes into the air passage 
 or mixing chamber; 
 
 Crank the motor. Always pull up on the crank. The 
 cranking should be done immediately after the gas is 
 turned on if there is no provision to prevent flow of the 
 gas into the air passage or mixture chamber; 
 
 As soon as the motor begins to run itself: 
 
 Turn on the cooling water if it has not been done before 
 (see preparations). This is not necessary in a circu- 
 lating system; 
 
 Close the throttle enough to prevent racing if the motor is 
 hand controlled; 
 
 Open the gas valve to its proper setting (see below); 
 
 Advance the ignition (see below). 
 
 There is no provision for retarding the time of ignition in many 
 small stationary motors. Under such conditions it is safer to 
 open a switch in the primary circuit of the ignition system before 
 cranking the motor. Then crank up to a fair speed and close 
 the switch. If this precaution is not taken, the motor may start 
 backward (kick) if the ignition comes as early as it should for 
 economical operation at fairly high speed. When provision is 
 made for retarding the ignition in a small stationary motor, there 
 
1 84 THE GAS ENGINE 
 
 are often only two positions in which the timer or igniter can be 
 set a starting and a running position. 
 
 If an electric generator that does not give enough pressure or 
 current to cause ignition until the motor has been cranked up to 
 high speed, is used, there is no necessity for the precaution of 
 breaking the ignition circuit when starting. 
 
 The amount of opening to be given the hand-opened gas valve 
 depends on the pressure of the gas and its richness or heat value. 
 The opening that gives maximum power can be determined by 
 noting the load that the motor will pull. The setting for maxi- 
 mum power does riot generally correspond to that for maximum 
 economy of fuel, however. The economy of fuel is generally 
 better with slightly less gas than is required for maximum power. 
 
 The hand crank for starting the motor should be made so as to 
 free itself and cease to rotate with the motor as soon as the latter 
 starts on its own power. 
 
 For the greatest safety to the operator, the hand crank should 
 be made, when possible, so that it can be pulled only upward at 
 the time of ignition. Then, if the motor kicks, the crank may 
 be snapped or jerked out of one's hand with less danger than 
 when pressing down on it. 
 
 113. Starting an Electrically Ignited Stationary Gasoline 
 Motor by Cranking. (See preparations. ) 
 
 Turn on the gasoline and lubricating oil; 
 
 Set the timer or igniter for late ignition; 
 
 Close the throttle well toward shut so that the motor will 
 
 not race if hand controlled; 
 
 Prime the carbureter (this is not generally necessary); 
 Crank the motor; pull up on the crank; 
 Turn on the cooling water if it has not been done before 
 
 (see preparations); 
 Advance the timer and close the throttle still further if the 
 
 motor is to run light for a while. 
 
 See preceding section regarding timer and crank. 
 It sometimes happens that the slow speed of cranking does 
 not cause enough gasoline to mix with the air while cranking 
 
STARTING AND ADJUSTING THE MOTOR 185 
 
 to form a combustible mixture. The priming o^ the carbureter 
 is intended to remove this difficulty. If there is no way of 
 priming the carbureter, its air intake may be partly closed 
 with one's hand or anything else that is convenient, while 
 cranking. This causes enough suction to draw out sufficient 
 gasoline. 
 
 When the motor is very cold, as one that has been exposed to 
 freezing weather, it is sometimes very difficult to get the fuel, 
 especially if it is of a poor grade for the purpose, to vaporize. 
 Most motors are provided with a small valve or pet -cock at the 
 top of the cylinder, through which gasoline can be poured into 
 the cylinder. If a small quantity of gasoline is poured in and 
 left for a minute or^two, it will generally vaporize and diffuse 
 enough to produce a mixture that will ignite. 
 
 A still further expedient with a cold motor is to pour hot water 
 into the jacket space, or into the circulating system at a con- 
 venient place. In the latter case, a motor with a circulating 
 pump should be rotated by hand to force the water into the 
 jacket. 
 
 Still another expedient, which should be that of last resort, is 
 to heat the cylinder and inlet pipe with a torch, or by putting a 
 little gasoline on them and burning it off. Very little gasoline 
 should be put on at first, and then more can be squirted on from 
 an oil can with a small opening in the nozzle. The gasoline will 
 not ignite in the can, for the flame cannot pass in through the 
 small opening. 
 
 114. Starting a Large, Electrically Ignited Gas Motor by 
 External Mechanical Power. The method is practically the 
 same as for the small gas motor, except the substitution of mechan- 
 ical power for muscular effort. 
 
 The gas motor to be started may be driven by friction gears 
 pressing against the flywheel. In such a device the driving gear 
 should be movable so as to be withdrawn from engagement with 
 the flywheel when the motor starts on its own power. 
 
1 86 THE GAS ENGINE 
 
 Starting the Motor by Its Own Impulse. 
 
 115. A single-cylinder, single-acting gas motor with electric 
 ignition can be started by its own impulse in the following manner 
 after it has been stopped by cutting off the fuel supply: Set the 
 crank past its dead-center position with the piston a short distance 
 out on its impulse stroke. The crank may be set as much as 
 30 degrees or even more past dead center. 
 
 Open the hand valve and allow gas to flow into the combustion 
 space through a small auxiliary pipe or opening for this purpose. 
 The gas mixes with the air in the cylinder that was drawn in after 
 the fuel was cut off. After enough gas has passed in to make a 
 combustible mixture, as determined by judgment or a small gas 
 meter, its flow is to be cut off. Then after the suitable prepara- 
 tions (see preparations) have been made, the charge is to be 
 ignited. This will give the piston an impulse sufficient to drive 
 the motor till a charge is drawn in and ignited. 
 
 When a battery is used in connection with an induction coil 
 for ignition, the first ignitioij can be made by leaving the battery 
 circuit open till the time to ignite and then closing it. The jump 
 spark thus produced will ignite the charge. 
 
 If an oscillating-armature magneto is used, the electric spark 
 or arc can be produced by snapping the armature over by hand. 
 In the absence of an ignition system suitable to cause ignition 
 when the motor is at rest, one manufacturer has adopted the 
 expedient of striking a match inside the combustion chamber 
 to ignite the charge. The end of a match is fastened in the 
 plunger point of a holder and the latter screwed into a threaded 
 hole in the combustion chamber wall. The plunger is then 
 forced in and the match ignited by rubbing against a surface 
 provided for the purpose. The flame of the match ignites the 
 charge. 
 
 116. Starting the Motor on " Compression." If the ignition 
 is cut out to stop a four-cycle, single-acting, four-cylinder motor, 
 and the throttle is opened during the last revolutions before 
 stopping, at least two of the cylinders will contain a combustible 
 charge when the motor stops. The piston of one of the charged 
 
STARTING AND ADJUSTING THE MOTOR 
 
 187 
 
 cylinders will stop 'on the impulse-stroke position. The motor 
 can be started again by exploding the charge in this cylinder. 
 In a hand-controlled motor the ignition can be effected by mov- 
 ing the timer to the position that will give a spark in the cylinder 
 whose impulse will start the crank in the right direction, that is, 
 in the cylinder whose piston is part way out on the impulse 
 stroke. 
 
 Two-cylinder, single-acting, four-cycle motors will some- 
 times stop in position to be started on compression, but this is 
 unusual and in the nature of an accident. Motors with more 
 than two cylinders generally stop so as to start on compression, 
 provided the fuel has free access and is not exploded while stop- 
 ping. 
 
 FIG. 76. 
 Starting Valve for Starting Motor with Compressed Air. 
 
 1. Motor cylinder. 3. Coil spring to hold valve closed. 
 
 2. Valve. 4. Lever for opening valve. 
 
 5. Connection to compressed air supply. 
 
 The motor is put into position with the piston a short distance out on the impulse 
 stroke and then the compressed air is admitted by opening the valve 2 by means 
 of the hand lever 4. 
 
 The length of time that a motor will retain a charge in the 
 cylinder so as to start on compression depends on the tightness 
 of the cylinder, piston, valves, etc. The writer has frequently 
 
1 88 THE GAS ENGINE 
 
 seen motors that have been in considerable service started in this 
 manner after standing for a week. 
 
 117. Starting by Firing a Blank Cartridge in the Cylinder. 
 Motors are not infrequently, and with entire success, started in 
 this manner. The powder should be comparatively slow burn- 
 ing, as black gunpowder. A blank cartridge, such as is used in 
 a gun, is suitable. The amount of powder necessary depends 
 on the size of the motor, of course. About four drams, or 120 
 grains, should start a motor with a cylinder bore six inches in 
 diameter. 
 
 It is advisable to begin with small charges of powder and grad- 
 ually increase the amount until it is great enough. 
 
 Suitable means of holding the cartridge, as a breech block, 
 must of course be provided. The piston of the cylinder in which 
 the cartridge is fired should be placed a short distance out on its 
 impulse stroke, with the crank for that cylinder some distance 
 past the dead-center position. 
 
 1 1 8. Stresses Due to Starting a Motor by Its Own Impulse. - 
 The explosion of a charge of combustible gas or a cartridge in 
 the cylinder when the motor is at rest produces a higher pressure 
 in the cylinder than if the piston were moving out on its impulse 
 stroke. The force transmitted to the crank shaft is greater in 
 proportion to the pressure against the face of the piston than 
 when the speed of the piston is accelerating rapidly at the time 
 of explosion, as is the case when the motor is running and the 
 charge is fired at the usual time at about the beginning of the 
 impulse stroke. It .is therefore not advisable to explode a full 
 charge in the cylinder when the motor is at rest, on account of 
 the great stresses that such an explosion would produce, unless 
 the motor is constructed with a view to starting it with full 
 charges. The practice of starting in this manner is mostly 
 confined to motors below medium size. 
 
 Starting on compression does not produce higher pressure in 
 the cylinder than the explosions during regular running, for the 
 piston stops in such a position that the charge is but slightly 
 compressed when ignited. The pressure of explosion is higher, 
 the higher the compression pressure at the time of igniting. 
 
STARTING AND ADJUSTING THE MOTOR 189 
 
 Starting the Motor with Compressed Air* 
 
 119. The use of compressed air in the cylinder for starting 
 the motor is a certain and gentle way. It is much used on large- 
 size motors. The cost of the equipment for compressing the air 
 is an objection to this method for small and medium size motors, 
 but when the compressed air is to be used for other purposes also, 
 this objection disappears. 
 
 120. In starting a single-cylinder, single-acting motor by 
 compressed air, the usual practice is to use a hand valve to 
 admit the compressed air to the cylinder after the crank shaft 
 has been rotated (barred over) to bring the piston to a position 
 a little way out on the impulse stroke. The compressed air is 
 turned on and quickly shut off again before the completion of 
 the impulse stroke. The momentum given the moving parts in 
 this manner is sufficient to keep them moving until a charge 
 is drawn in and exploded immediately after the first suction 
 stroke. 
 
 The air is generally compressed by a compressor driven by 
 the motor long enough to store up a sufficient amount of the 
 compressed air in storage tanks. Some attempts were made in 
 the earlier single-acting, single-cylinder motors to have them 
 act as air compressors while stopping after the fuel was cut off. 
 This practice has not come into much use. 
 
 121. Starting a Motor with More than One Combustion Cham- 
 ber by Compressed Air. When the motor has more than one 
 combustion chamber, compressed air can be used in one of them 
 for driving the motor till the explosion impulses in the other 
 combustion chamber (or chambers) come into effect to drive 
 the motor. The compressed air is then shut off and the motor 
 operates in the usual manner. 
 
 A starting valve-mechanism must be brought into operation 
 on the valves of the combustion chamber to which the compressed 
 air is admitted, so as to cause the admission valve to open during 
 the early part of each outstroke of the piston and the exhaust 
 valve to open during each return or instroke of the same piston. 
 * See also Diesel motor. 
 
190 THE GAS ENGINE 
 
 The starting cams or other starting mechanisms are usually made 
 so as to be readily moved into position for starting and promptly 
 withdrawn when the motor has gained speed. 
 
 An automatic device for cutting off the compressed air is 
 used in general practice. 
 
 Adjusting the Lubricator and Cooling Water. 
 
 122. Lubricator Adjustment. The lubrication of the piston 
 requires more care than that of the other parts of the motor, 
 although it is very important that all of the bearings shall have 
 plenty of oil or grease. It is practically impossible to give the 
 bearings of the crank shaft, connecting rod, cam shaft, and other 
 similar parts too much oil, but an excess of oil for the piston is 
 accompanied with undesirable results, which are not so serious, 
 however, as those of too little oil. 
 
 The piston (or cylinder) lubricator can be well opened at first, 
 so that blue smoke is discharged with the exhaust gases, and then 
 gradually closed just enough to prevent the appearance of the 
 blue smoke. The oil should be cut down slightly and the motor 
 allowed to run at least several minutes before making further 
 adjustment of the piston lubricator. The black smoke of too 
 rich a mixture should not be mistaken for the blue smoke of too 
 much oil. The actual amount of piston-lubricating oil cannot be 
 well specified for motors in general, but it is safe to start with 
 twenty small drops a minute for a piston 5 inches in diameter and 
 running at high speed. The condition of the exhaust gases can 
 be observed by opening a small hole in the pipe near the motor, 
 or by partly disconnecting a pipe joint, when the motor dis- 
 charges into the atmosphere at a considerable, or unobservable, 
 distance from the motor, as is frequently the case with stationary 
 motors. 
 
 For the bearings of small motors from which the oil is allowed 
 to run to waste, three or four drops a minute on crank-shaft 
 bearings 2 inches in diameter and running at 400 to 500 revolutions 
 per minute are generally sufficient. The smaller* and slower 
 speed cam shaft requires but very little oil. 
 
STARTING AND ADJUSTING THE MOTOR 191 
 
 123. Cooling- Water Adjustment. When the, cooling water is 
 taken from water mains and allowed to flow to waste the water 
 valve should be set so as to give the escaping water a temperature 
 as near the boiling point as possible. The amount of water 
 depends on the rate at which the motor is developing power. It 
 requires more water at full load than at light load. Care should 
 be taken to give it enough water for the heaviest load that comes 
 on it. 
 
 In circulating systems of cooling there is seldom any means of 
 adjusting the rate of flow. In thermal systems the water in the 
 cooler must be kept above the opening of the upper pipe from 
 the motor, as has been previously stated. 
 
 Adjusting Spray Carbureters and the Ignition. 
 
 124. The air-valve stop, not generally used, is not referred to 
 in the following direction for adjusting carbureters. This stop 
 is used in some carbureters for constant-speed motors, where its 
 function is to positively limit the lift of the automatic air valve of 
 the carbureter. 
 
 It should be remembered that the more the lift of the carbu- 
 reter air valve is restricted by the stop, the richer will be the 
 mixture when the motor is working at full load. The intro- 
 duction of the action of this device into the general discussion 
 would make it complicated to an extent hardly warrantable on 
 account of the small use that is made of the stop. 
 
 125. Rich and Lean Fuel Mixtures. The amount of power 
 developed by a motor falls off from the maximum with either 
 an increase or a decrease in the proportion of the fuel in the 
 mixture, and the charge fails to ignite when it becomes either 
 too rich or very lean. If the mixture is very rich, but still ignites, 
 black smoke will be discharged with the exhaust. The exhaust 
 from an over-rich gasoline mixture has a strong characteristic 
 odor and is painful to the eyes, even if it is not so rich as to pro- 
 duce black smoke. The black smoke should not be confused 
 with the blue smoke that comes from too much lubricating oil 
 in the cylinder or from oil of the wrong quality. 
 
1 92 THE GAS ENGINE 
 
 A very rich combustible mixture burns so slowly that the flame 
 continues long enough to pass out into the exhaust pipe when 
 the exhaust valve (or port) is opened. This heats both the 
 cylinder and the exhaust valve and pipe unduly, as well as wasting 
 the fuel. The ignition of an over-rich mixture is uncertain. An 
 unfired charge is therefore apt to pass out into the exhaust pipe, 
 where it is subject to ignition by the flame of a succeeding burn- 
 ing charge or by hot particles of soot in the exhaust pipe or 
 muffler. The after explosion, or muffler explosion, thus pro- 
 duced is extremely undesirable. 
 
 Premature ignition is apt to occur with the continued use of 
 too rich a mixture, on account of the carbon or soot that is de- 
 posited on the walls of the combustion chamber while the charge 
 is burning. This deposit becomes ignited and burns like the 
 soot in a fireplace in a house. The glowing soot ignites the 
 charge prematurely, generally during the compression stroke of 
 the piston. It may, however, ignite the entering mixture during 
 the suction stroke, thus causing back firing into the intake pipe. 
 
 A very lean mixture is also slow burning and uncertain of 
 ignition. This is especially true when the charge is also rare- 
 fied by a nearly closed throttle. The characteristic result of a 
 lean mixture is back firing into the inlet pipe and carbureter, or 
 into the crank case of a two-cycle motor of the type in which the 
 mixture is compressed in the crank case. The back firing is 
 caused by the slow burning of the charge till the fuel port is 
 opened and the mixture in the inlet passage is ignited by the 
 flame in the combustion cuamber. The explosion thus pro- 
 duced in the intake passage and carbureter is sharp and light 
 in sound. It compares with an exhaust explosion as the snap- 
 ping of a percussion cap does with the report of a gun using 
 black powder. 
 
 Misfires of a lean mixture are also conducive to explosions in 
 the exhaust. 
 
 When the fuel mixture is too rich there will generally be com- 
 bustible gas carried out with the exhaust in the form of carbon 
 monoxide, CO. Carbon monoxide is not only suffocating but 
 also poisonous. 
 
STARTING AND ADJUSTING THE MOTOR 193 
 
 The following method of detecting CO in the, exhaust gases 
 from an internal-combustion motor is given by Mr.R. E.Mathot.* 
 "A small glass flask, about two inches in diameter and four 
 inches high, closed with a cork, through which pass two vertical 
 tubes, is used for collecting some of the exhaust gas. One of 
 the tubes is connected to the exhaust pipe of the engine, while 
 the other end is plunged in mercury about one inch deep in the 
 flask. As soon as the connection between the exhaust pipe and 
 flask is established, some of the exhaust gas will be blown into 
 the flask at each stroke, and the mercury, operating as a check 
 valve, will prevent it from being withdrawn. The air contained 
 in the flask, and afterward the exhaust gas, will be expelled 
 through the second pipe open to the atmosphere and ending 
 inside, at the top of the flask. 
 
 "To detect CO, which is contained in the exhaust gas con- 
 tinuously rushing through the flask, a small piece of white 
 blotting paper is hung in the flask, the paper being previously 
 prepared by dipping five or six times in a solution of double 
 chlorid of palladium and sodium of such concentration as to 
 give a dark brown color, and drying after each immersion. 
 
 "If there is more than 1 per cent of CO in the' exhaust gases, 
 the paper will, in two or three minutes, lose its bright brown 
 color and become gray. This shows insufficient air in the mix- 
 ture for combustion, which can be corrected at the mixing 
 valve." 
 
 126. Rough Adjustments for Black Smoke and Back-firing. - 
 If black smoke (not blue, see adjustment of lubricator) is dis- 
 charged from the exhaust after the motor has been running a 
 minute or so after starting, the fuel mixture is too rich. The fuel 
 valve of the carbureter should be closed some, or the air valve (of 
 the carbureter) opened more. 
 
 If the motor back-fires with a sharp explosion in the intake pipe 
 and carbureter, it may be due to having the throttle nearly closed 
 and the ignition set late in a hand-controlled motor, or the fuel 
 mixture may be too lean. Open the throttle slightly and advance 
 the ignition a little. If this does not stop the back firing, then, 
 
 * Trans. Amer. Soc. Mechanical Engineers, April, 1908, Vol. 30, p. 401. 
 
IQ4 THE GAS ENGINE 
 
 if the carbureter has been previously adjusted, close and open the 
 needle fuel valve quickly, so as not to stop the motor, bringing the 
 valve back to the same setting that it had. This will generally 
 remove or crush foreign matter that may have lodged under the 
 valve. If the back firing still continues, open the fuel valve still 
 more, or close the air valve some. Continue this till black smoke 
 appears at the exhaust if the back firing does not stop before. If 
 this does not stop the back firing, it is probably due to some other 
 cause than those just mentioned. (See back firing). 
 
 Closing the air valve enriches the mixture in greater proportion 
 with a closed setting of the throttle and slow speed of the motor 
 than with an open throttle and high motor speed, in the usual 
 forms of carbureters. The same effects generally obtain when 
 the spring is adjusted to press the air valve harder on its seat in a 
 carbureter with a spring-closed air valve. Adjusting the spring 
 to press the air valve harder on its seat is commonly referred to 
 as closing the air valve. 
 
 The above adjustments are only rough ones, and should be 
 followed by the more accurate ones described later. 
 
 127. Adjusting the Carbureter and Ignition on a Cut-Out- 
 Governed Motor. (See preceding section for rough initial 
 adjustments.) 
 
 Run the motor on a constant load and adjust the fuel valve and 
 the air valve to obtain the maximum number of cut-outs. 
 
 Set the timer to give earlier and later ignition till the position 
 of the timer that gives the greatest number of cut-outs is deter- 
 mined. Leave the timer in this position, and 
 
 Adjust the carbureter again as at first. 
 
 Continue the adjustments of the carbureter and timer in this 
 manner till the final settings for the greatest number of cut-outs 
 are found. 
 
 128. Adjusting the Carbureter and Ignition of a Throttle- 
 Governed Motor. (See rough adjustments. ) To make the best 
 adjustment for regular service, the motor should be run part of 
 the time on a nearly full load of constant value and the remainder 
 of the time on a small constant load of about the same amount as 
 the average small load on which the motor is to operate. These 
 
STARTING AND ADJUSTING THE MOTOR 195 
 
 loads can be obtained by the use of an absorption dynamometer if 
 not otherwise. 
 
 The object in each case is to secure the least opening of the 
 throttle for the load applied. 
 Put on the full load : 
 
 Set the air valve of the carbureter at about mid-position; 
 Adjust the fuel valve and the ignition to find the settings 
 
 that let the throttle close farthest. 
 Put on the small load: 
 
 Adjust the air valve to give the least opening of the throttle; 
 Set the air valve about midway between its first and second 
 
 settings. 
 
 Put on the full load again and adjust the fuel valve and the 
 air valve in the same manner as before with both the 
 full and the small load. Repeat until very slight adjust- 
 ments are required when changing from one load to the 
 other. 
 
 Put on the small load and adjust the ignition for the least 
 opening of the throttle. 
 
 If the throttle continues to close as the air valve is adjusted 
 up to its limit either way at any time during the test, then the 
 air valve should be set nearly to its other limit and the process 
 of adjustment begun again. 
 
 When the limit of the decrease of the throttle opening is not 
 reached by adjusting the spring-closed air valve from one ex- 
 treme setting to the other, then the spring is either too weak or 
 too strong, provided the carbureter is otherwise correctly con- 
 structed. 
 
 If the initial setting of the spring gave the lightest pressure of 
 the air valve on its seat, and the adjustments increased the seat- 
 ing pressure up to the heaviest, then the spring is too weak. 
 The remedy is to remove the spring and stretch it, if it is a com- 
 pression spring, so as to close the valve harder. The stretching 
 must give the spring a permanent elongation when it is free. 
 A tension spring (seldom used) must be shortened under similar 
 conditions. 
 
196 THE GAS ENGINE 
 
 The reverse of the above applies to the spring when its initial 
 setting gives the heaviest pressure of the valve on its seat. 
 
 The fuel valve may be slightly closed from the adjustment 
 determined as above in order to secure the best economy of 
 fuel. 
 
 The ignition should finally be set to correspond with the pre- 
 vailing load, using at least two of the settings just determined 
 as a guide, but it should not be set so early as to cause thump- 
 ing of the motor on full load. 
 
 129. Adjustment of a Variable-Speed Motor with Hand Con- 
 trol by Throttle. (See rough adjustments. ) In a hand-con- 
 trolled variable-speed motor the throttle and the ignition are 
 both operated by hand when controlling the motor, except in 
 infrequent designs where the time of ignition is not changed. 
 
 The following method of adjusting the carbureter applies to 
 motors in which both the throttle and the ignition are manipu- 
 lated for controlling. 
 
 The adjustment requires the load to be rapidly varied at will, 
 as by an absorption dynamometer. 
 
 After each adjustment or set of adjustments is made, the 
 throttle may be quickly operated between the open and the 
 nearly closed positions (not completely closed). If this causes 
 either back firing or smoky exhaust, further adjustment of the 
 carbureter should be made before testing any more. If there 
 is black smoke, the air valve generally should be opened more; 
 if there is back firing, the air valve should generally be closed 
 some. Adjustments the reverse of these are sometimes re- 
 quired, however, this depending on the form of the carbureter. 
 If misfiring occurs with neither black smoke nor back firing while 
 the throttle is quickly operated, the fuel valve can be adjusted, 
 but whether more or less fuel is needed cannot be determined 
 before making an adjustment. 
 
 i. Adjust the air valve to about mid-position; set the ignition 
 late and the throttle to give nearly maximum speed with no load 
 or a very small load. Put on a small load and open the throttle 
 till the speed is well up to the maximum. Increase the load 
 and open the throttle still more till the speed is nearly up to the 
 
STARTING AND ADJUSTING THE MOTOR 197 
 
 maximum again. Continue the increase of thjs load and the 
 opening of the throttle till the latter is full open. Then advance 
 the timer and increase the load till the setting of the ignition that 
 pulls the greatest load at somewhat less than maximum speed 
 is determined. Now adjust the fuel valve and timer to increase 
 the speed till the maximum is reached. Retard the timer slightly, 
 put on more load, and adjust the fuel valve and timer again till 
 the maximum speed is reached. Continue till the settings that 
 give the greatest load at full speed are found. 
 
 2. Retard the timer and increase the load till the motor is 
 brought down to a slow speed. Adjust the air valve and ignition, 
 and increase the load till the greatest load that the motor will 
 pull at slow speed is determined. 
 
 3. Set the air valve about midway between its last two positions 
 and repeat the operations and adjustments of (i). 
 
 4. Repeat the operations of (2). 
 
 5. Continue the adjustments as above till there is not much 
 change of setting for the maximum and slow speeds with heavy 
 loads. Make the last adjustment of the air valve as in (2). 
 
 6. Set the throttle about one-quarter open and adjust the air 
 valve to the setting that gives the most satisfactory operation at 
 all speeds with light load. The ignition must also be adjusted 
 during this test, of course. Just what is the most satisfactory 
 operation of the motor depends on the nature of the service 
 required. 
 
 7. Set the air valve about two-thirds of the way back toward 
 the last setting. Give the throttle full opening and adjust the 
 fuel valve to give the best results at maximum speed. If these 
 fall much below what was obtained in (i), the test should be 
 started over again with a different setting of the air valve from 
 that in (i). 
 
 If the power continues to increase as the air valve is adjusted 
 up to its limit either way at any time during the test, then the 
 air valve should be set to its other limit and the series of tests 
 begun again. (See latter half of preceding section.) 
 
198 THE GAS ENGINE 
 
 130. Adjustment of the Carbureter on an Automobile. The 
 
 following is such an adjustment as can be made on the road 
 without any apparatus other than the automobile itself. 
 
 1. Set the air valve at about mid-position. 
 
 2. Open the throttle half way or less. 
 
 3. Set the timer for late ignition. 
 
 4. Disengage the clutch. 
 
 5. Start the motor. 
 
 6. Advance the timer part way. 
 
 7. Open and close the throttle quickly several times to deter- 
 mine how rapidly the motor speeds up, and whether there is 
 either black smoke in the exhaust or back firing. Set the timer 
 in different positions while doing this. 
 
 8. If back firing occurred, open the fuel valve more, or close 
 the air valve some; 
 
 If black smoke (not blue) was discharged, close the fuel valve 
 some, or open the air valve more; 
 
 Test after each adjustment by opening and closing the throttle 
 at different settings of the timer until the motor operates satis- 
 factorily. 
 
 9. Test the motor by climbing a hill or by noting the rate of 
 speed acceleration on a level road. 
 
 10. Adjust the fuel valve (without changing the air-valve 
 setting) till the best running of the car is obtained. 
 
 11. Change the air-valve setting and repeat (10). 
 
 12. Change the air-valve settings again and repeat (10). 
 Continue in this manner till the settings of the air valve and the 
 fuel valve that give the most satisfactory operation are deter- 
 mined. 
 
 131. Adjusting the Carbureter and Ignition on a Launch 
 Motor. The requirements for power in this case are much like 
 those for an automobile motor, but simpler. There is no demand 
 for maximum torque, or turning effort, at slow speed of the motor 
 in a launch. 
 
 Apply such of the steps for the automobile as are necessary. 
 The object is to secure maximum speed of rotation. 
 
STARTING AND ADJUSTING THE MOTOR 199 
 
 Adjusting the Fuel Mixture in Gas and Oil Motors. 
 
 132. The securing of a suitable proportion of gas and air for 
 a combustible mixture is a much simpler operation for the gas 
 motor than when the air is carbureted by the vaporization of a 
 volatile liquid. 
 
 In the simpler designs only the gas valve is set by trial to the 
 position that gives the greatest power, speed, etc., as is desired. 
 
 The more complicated designs of gas-and-air mixers have 
 adjustments for both the gas and the air in some cases. Since 
 the process of adjusting is so simple, it seems hardly necessary 
 to give the steps in detail. 
 
 It is generally more economical of fuel to close the gas valve 
 slightly after the adjustment for maximum power has been found. 
 
 In some designs of gas motors, the securing of the proper 
 mixture proportions is largely a matter of selecting the proper 
 proportions in designing. Designing is not under consideration 
 in this part of the discussion. 
 
 The above statements also apply in a general way to oil motors 
 in which the oil is injected into the combustion space. The 
 regulation of the fuel is generally by varying the stroke of the 
 piston of the oil pump, by opening a by-pass valve, etc. 
 
CHAPTER IX. 
 SETTING OR TIMING THE VALVES AND IGNITER. 
 
 133. Marks for Valve Setting. A large number of motors, 
 especially those on automobiles, have marks on the flywheel to 
 indicate its positions when the valves should begin to open and 
 complete their closing. One of the marks on the flywheel 
 registers with a reference mark, that is stationary with regard to 
 the frame of the motor, at the instant that the corresponding 
 valve should just begin to open, and another mark on the flywheel 
 registers with the same reference point at the time the valve 
 should just come in contact with its seat. 
 
 Since the mark on the flywheel is often a line drawn across its 
 face in a direction parallel to the shaft, or radially across the side 
 of the rim, and since the stationary part is often a pointed piece 
 of metal, they will be referred to as the flywheel mark and the 
 reference point, or, more briefly, as the mark and the point, for 
 convenience. 
 
 134. Testing the Valve Timing when the Flywheel is Marked. 
 The simplest case is a single-cylinder, single-acting motor with 
 an automatic inlet valve and one exhaust valve (which must be 
 mechanically opened). (There are sometimes two mechani- 
 cally opened exhaust valves when an auxiliary exhaust port is 
 used.) 
 
 To test the valve setting: Insert a piece of very thin tissue 
 paper (thick paper will not do) between the end of the valve stem 
 and the part that lifts it. Rotate the motor by hand or any other 
 suitable means till the piston and other parts are in the position 
 of about three-quarters of the impulse stroke. Then turn the 
 shaft very slowly in the direction that it runs and keep the paper 
 moving at the same time till it is pinched tight by the movement 
 of the valve-lifting mechanism toward the valve stem. Stop in 
 
 200 
 
SETTING OR TIMING THE VALVES AND IGNITER 2OI 
 
 this position. If the valve setting is correct, tfre mark on the 
 flywheel will register with the reference point. 
 
 If the mark has not yet reached the point when the paper is 
 first pinched, then the valve opens too early according to the 
 marking. But if the mark has passed the point, then the valve 
 does not open soon enough. 
 
 For the closing of the valve, rotate the crank shaft quickly 
 through about half a revolution in the direction that the motor 
 runs without paying any attention to the paper under the valve 
 stem. Then turn the crank shaft very slowly while pulling on 
 the paper till it begins to loosen on account of the seating of the 
 valve and the reduction of pressure against the valve stem. If 
 the second flywheel mark and the reference point register at the 
 instant the paper begins to loosen, then the time of valve closing 
 is correct according to the marking. If the mark has not yet 
 reached the point, the valve closes too early, but if the mark has 
 passed the point the valve closes too late. 
 
 When the inlet valve is mechanically operated, its setting 
 can be tested in the same manner as that for the exhaust valve. 
 The exhaust valve should always be closed before the inlet 
 valve begins to open, in motors of the usual construction with- 
 out provision for scavenging. This can be determined without 
 any markings on the flywheel. 
 
 In a two-cylinder motor with either opposed or twin cylinders, 
 whose explosions occur every revolution, the same marking of 
 the flywheel serves for both cylinders. 
 
 In a four-cylinder motor, either with all the cylinders on one 
 side of the crank shaft or with two on each side, whose explo- 
 sions come every half revolution, there must be two sets of mark- 
 ings. One set is the same as the other, but half way round the 
 flywheel from it. 
 
 In a six-cylinder motor with the cranks in pairs at 120 
 degrees apart and the cylinders all on the same side of the 
 crank shaft, there are three sets of markings, one third of a 
 revolution apart. 
 
 The gears that connect the cam shaft to the crank shaft should 
 be marked so that they can be placed together again with the 
 
202 THE GAS ENGINE 
 
 same teeth mating as before, in case of their being taken apart. 
 Some manufacturers mark the gears for this purpose. 
 
 135. Locating Dead Centers when there are no Marks for 
 Valve Setting. If there is no marking for the valve setting or 
 for the dead-center positions of the crank, then the latter should 
 be determined. 
 
 To determine the dead centers, some means of locating the 
 position of the piston is necessary. When there is a 'pet-cock 
 with a straight passage in the cylinder head, and the length of 
 the passage is parallel to the bore of the cylinder, this can be 
 done by inserting a straight wire through the pet -cock till the end 
 touches the piston. The wire should be of about the same size 
 as the hole. If the head of the piston is flat, the wire will always 
 enter the same distance for the same position of the piston. 
 But if the piston head is not flat, care must be taken to insert 
 the wire so that it will always enter the same distance for a given 
 position of the piston. Any opening through the cylinder head, 
 as that for the ignition plug of the pet-cock, can be used for 
 inserting the wire after the part is removed. If there is no open- 
 ing in the cylinder head, then the position of the piston can be 
 determined from the crank end of the cylinder. The crank case 
 may have to be opened for this purpose. The general method of 
 procedure is the same in all cases when the cylinder is not offset 
 (set to one side so that the center line of the bore does not 
 intersect the axis of the crank shaft). 
 
 Offset cylinders are unusual. The method of determining the 
 dead centers will therefore be given only for those whose crank 
 shaft crosses in front of the center of the cylinder bore. It will 
 be assumed that there is a suitable pet-cock for inserting 
 the wire. 
 
 Put the wire into the cylinder through the pet-cock till its end 
 rests against the piston and rotate the crank shaft through about 
 one revolution. Note roughly the positions of the wire while 
 resting against the piston at each end of its stroke. Make a 
 notch in the wire at a position that will coincide with the end 
 of the pet-cock when the piston is about one-third of the way out 
 from its position nearest the head of the cylinder. This notch 
 
SETTING OR TIMING THE VALVES AND IGNITER 203 
 
 can be located by judgment without measuring. Place the wire 
 against the piston as before and turn the crank shaft till the 
 notch on the wire registers with the end of the pet-cock. Make 
 a temporary mark on the face of the flywheel to coincide with 
 a stationary reference point. Rotate the crank again through 
 part of a revolution till the notch on the wire again registers 
 with the end of the pet-cock. Mark the flywheel again as be- 
 fore to coincide with the reference point. Divide the shortest 
 length of the periphery of the flywheel between the two marks 
 just made on it into halves and make a third mark midway 
 between the other two. When the last mark registers with the 
 stationary reference point, the crank will be in its dead-center 
 position with the piston at the head end of its stroke. 
 
 The dead-center position with the piston at the crank end of 
 its stroke can be determined in a similar manner by placing 
 another notch on the wire where it will coincide with the end of 
 the pet-cock when the piston is about one-third of the way from 
 the crank end of the cylinder. The two dead-center marks will 
 be 1 80 degrees, or half the circumference of the flywheel, apart, 
 if correctly located. 
 
 When there is no flywheel, or it is difficult of access, some 
 other rotary part can be used in the same manner. In small 
 motors, the starting crank can be used as the hand (as of a clock) 
 and a board or piece of cardboard provided for a dial. 
 
 136. Time at which a Valve should Open and Close. In a 
 four-cycle motor, the exhaust valve should open long enough 
 before the piston reaches the end of its impulse stroke to allow 
 the pressure in the cylinder to drop nearly to atmospheric by 
 the time the piston has moved an appreciable distance on the 
 exhaust stroke, and should not close before the end of the exhaust 
 stroke. The smaller the port and the less the lift of the valve, 
 the earlier must it open and the later it must close. 
 
 A mechanically operated inlet valve should not open before 
 the exhaust valve has closed, and should remain open at least 
 until the suction stroke is completed. 
 
 The time at which a valve must open and close in relation to 
 the position of the piston in its movement in order to develop 
 
204 THE GAS ENGINE 
 
 the most power depends principally on the following three 
 items : 
 
 Speed of rotation of the motor; 
 
 Area of the ports in relation to the volume of the cylinder, 
 
 or of the piston displacement per stroke; 
 Lift of the valve. 
 
 Among other features (which should all be minor ones) 
 affecting the valve timing are the back-pressure resistance to 
 the exhaust and the suction resistance to the intake due to causes 
 outside of the motor proper. 
 
 In high-speed, single-acting, four-cycle automobile motors the 
 exhaust valve is sometimes set to open as much as 40 degrees 
 (one-ninth of a revolution) of rotation of the crank before the 
 piston has reached the end of its impulse stroke, and does not 
 close until as late as 10 degrees (one-thirty-sixth of a revolution) 
 after the completion of the exhaust stroke. In such a case the 
 inlet valve does not generally open earlier than 15 degrees (one- 
 twenty-fourth of a revolution) of rotation on the suction stroke. 
 It sometimes closes the same amount later on the compression 
 stroke. 
 
 The proportion of the stroke of the piston represented by 
 these angles of rotation is not as great as it might at first seem, 
 especially at the crank or exhaust end of the stroke, where the 
 angularity of the connecting rod brings the piston nearer the 
 end of its stroke than it is from the completion of its stroke at 
 the head end when the crank is the same part of a revolution 
 from the head dead center. 
 
 When the length of the connecting rod is twice that of the 
 stroke of the piston (connecting-rod length = four times the 
 crank radius), which does not differ much from automobile 
 motor practice, and the crank is 40 degrees from the dead-center 
 position between the impulse and exhaust strokes (crank dead 
 center), the piston has only .091 (less than one-tenth) of its 
 stroke remaining to complete the impulse ' stroke. When the 
 exhaust valve closes 10 degrees after the completion of the 
 exhaust stroke, the piston has moved out only .0095 (less than 
 
SETTING OR TIMING THE VALVES AND IGNITER 205 
 
 one-hundredth) of the suction stroke from the hea/1 end When 
 the inlet valve opens at 15 degrees of the crank past dead 
 center, the piston has moved out .021 (a little more than one- 
 fiftieth) of its stroke from the head end. And if it closes at the 
 same angle of the crank past the crank dead center, then the 
 piston has moved out .013 (a little more than one-eightieth) of 
 its stroke from the crank end. 
 
 The writer's experience in increasing the power development 
 of motors by changing the timing of the valves on a number of 
 automobile motors of different makes in which the exhaust and 
 inlet valves, as originally timed, closed at or near the dead-center 
 positions of the crank, or the exhaust valve opened only slightly 
 before the dead-center position, or in which all three of these 
 conditions existed, has been thoroughly convincing in favor of 
 early openings and late closings to conform more or less nearly 
 with those just mentioned, according to speed, area of ports, 
 lift of valves, etc. In some cases the only change was to set the 
 cam shaft a little earlier in relation to the crank shaft, while in 
 others new cams were made. 
 
 In moderate- and slow-speed motors on which an indicator 
 can be used without the inertia effects of its moving parts causing 
 serious modification of the true indicator card, the card can be 
 used to determine the correctness of the valve action. This will 
 be discussed later (see Indicator diagrams). In very high-speed 
 motors the power test is all that can be applied for this purpose. 
 The power test is the crucial one in all cases. 
 
 137. Marking the Flywheel for Valve Setting. After the 
 times of opening and closing of the valves have been decided 
 upon, the flywheel can be marked accordingly. 
 
 If the exhaust valve is to begin opening at one-ninth of a 
 revolution before the completion of the exhaust stroke, measure 
 from the crank dead-center mark on the flywheel (see locating 
 dead centers) one-ninth of the circumference around in the 
 direction of its rotation and mark the flywheel accordingly 
 (see below for lettering). If the exhaust valve is to close one- 
 thirty-sixth of a revolution after the completion of the exhaust 
 stroke, measure one-thirty-sixth of the circumference of the fly- 
 
206 THE GAS ENGINE 
 
 wheel from the head dead-center mark in the direction opposite 
 that of the rotation. For the inlet valve to open one-twenty- 
 fourth of a revolution after dead center, measure from the same 
 (head) dead -center mark one-twenty-fourth of the circumference 
 in the same direction (opposite the rotation). And for the inlet 
 valve to close 15 degrees after the dead center, measure one- 
 twenty-fourth of the circumference from the crank dead-center 
 mark in the direction opposite the rotation. 
 
 The marks on the flywheel should be lettered to avoid con- 
 fusion, especially in multi-cylinder motors. The following 
 lettering is suggested. A numeral can be placed after the 
 letters of each marking to indicate to which cylinder or com- 
 bustion chamber it refers. If the same mark is for more than 
 one valve, the corresponding numerals can be placed after the 
 letters. 
 
 HC = head center. 
 CC = crank center. 
 EO = exhaust opens. 
 EC = exhaust closes. 
 IO = inlet opens. 
 1C = inlet closes. 
 EO 1-3 = exhaust opens for cylinders i and 3. 
 
 138. Effect of Worn and Loose Parts on the Valve Action. 
 A cam shaft whose driving mechanism has become worn so 
 that the shaft lags behind its correct position, retards both the 
 opening and the closing of a valve. A cam whose fastening is 
 loose so that the cam lags produces the same effect. 
 
 A loose cam that lags when opening a valve and then snaps 
 forward under the pressure of the valve spring, retards the time 
 of opening and allows the valve to close too early, thus decreas- 
 ing the duration of the open period. 
 
 Wear of any part of the valve-operating mechanism of the usual 
 construction, other than wear that allows a cam to lag as stated, 
 causes late opening and early closing, shortening the duration of 
 the opening. 
 
SETTING OR TIMING THE VALVES AND IGNITER 207 
 
 The regrinding of a valve down on its seat has the effect of 
 lengthening the valve stem. This causes early opening and late 
 closing, which is compensative with the wear of the parts. 
 
 The methods of applying the remedies for the above troubles 
 depend on the construction of the motor. When a lifting rod 
 or a push rod is used for raising a valve, it is often made with 
 some provision for adjusting its length. This affords a means 
 of compensating, more or less completely, wear of all the usual 
 kinds except that which allows a cam to lag or turn slightly on 
 its shaft. When no provision for adjustment is made, the push 
 rod or the valve stem can be cut off when necessary, or if it 
 needs lengthening, a thimble-shaped cap can be placed over its 
 end, or a pin inserted in the end to lengthen it. The pin may 
 have an enlarged end to resist wear. In some designs the push 
 rod is a short round bar inserted between the valve stem and 
 the lifting mechanism. A new push rod of this form can be 
 substituted readily at small expense, or in an emergency it can 
 be elongated by hammering. 
 
 A worn cam can be built up by brazing or riveting a piece on 
 it, first cutting away a portion if better results can be thus ob- 
 tained. In case of doubt as to the exact form of the cam, it can 
 be left a little full for the first trial of the valve action and then 
 cut down accordingly. 
 
 139. Adjusting the Ignition Timer. When a battery and an 
 induction coil are used, the following method can be applied: 
 Open the pet -cocks of the combustion chambers, or remove the 
 spark plugs or disconnect the wires leading to them. Set the 
 crank shaft on dead center with one piston at the end of its 
 stroke between compression and impulse. Set the hand control 
 a little in advance of the retard, or late ignition, position. Turn 
 the rotor of the timer in the direction that it is to rotate until 
 the circuit is just closed and a spark produced for the cylinder 
 whose piston is set as given above, and fasten the rotor in this 
 position. 
 
 If the speed of the motor is too high when running with a 
 small load, the throttle well closed and the timer retarded as 
 far as possible, then move the rotor back a little in the direction 
 
208 THE GAS ENGINE 
 
 opposite its rotation, or adjust the connecting mechanism so 
 that the stationary part of the timer is moved further in the 
 direction of rotation of the rotor. 
 
 For an oscillating magneto the method of adjusting is the 
 same in a general way. The part that engages with the lever or 
 arm of the armature must be set so that the parts will disengage 
 at the proper instant. 
 
 In low-tension ignition with cams to operate the contact 
 points of other mechanism, the method of setting the ignition 
 cams is similar to that for timing the valves. 
 
 A high-tension magneto with a rotary armature should have 
 some part of the rotor or its attachments marked to indicate the 
 position when the timer closes the circuit. In the absence of 
 such marking, the current from a battery or a lighting circuit 
 can be used to determine the instant that the timer closes the 
 circuit. After this is done, the process of setting is of the nature 
 of those just described. If current from a lighting system is 
 used, there should be an incandescent lamp, water resistance, 
 etc., in series with the generator in order to keep down the 
 current. 
 
 140. Comparing the Time of Ignition in Different Cylinders. 
 - It is important that there shall be very little variation in the 
 time of ignition, relative to the positions of the respective pistons, 
 in the various cylinders of a multi-cylinder motor. The follow- 
 ing method can be used for testing the time at which the primary 
 circuit is closed in a jump-spark system. 
 
 Set the crank shaft in one of its dead-center positions. (See 
 marking the flywheel for valve setting.) If there are no dead- 
 center marks on the flywheel or elsewhere, any mark or marks 
 arranged to come opposite a stationary reference mark at such 
 parts of a revolution as correspond to the intervals, as they 
 should be, between ignitions, will answer equally well. (See 
 impulse frequency for different arrangements of cylinders.) 
 
 Advance the timer of a jump-spark system from the retard 
 position (late ignition) till the primary circuit is just closed and 
 leave the tinier in that position. Rotate the crank' shaft in the 
 direction of running and note whether the timer always closes all 
 
SETTING OR TIMING THE VALVES AND IGNITER 209 
 
 the circuits at the instant the timing marks register with the 
 reference point. Only a very slight variation from this condition 
 is allowable. 
 
 If the primary current is supplied by a rotary generator driven 
 by the motor during regular service, a battery or other source of 
 electricity must be substituted while making the test. 
 
 In the case of an oscillating generator (magneto) for either 
 high-tension or low-tension ignition, it is generally sufficient to 
 determine whether the armature is released and snaps back at 
 the same relative position of the piston for each cylinder if the 
 speed of rotation of the motor is not high. The method is 
 practically the same as that just given. If the speed of the motor 
 is very high, a test should also be made to determine whether the 
 primary circuit is always closed at the same position of the arma- 
 ture in its snapping-back motion, or whether the different pairs 
 of contact points of a low-tension system separate at the same 
 position of the armature. 
 
 When a rotary generator is used for the low-tension (arc, 
 make-and-break, break-and-make) system, a battery current of 
 a few volts can be passed through the contact points and the time 
 of their separation, as indicated by the interruption of the current, 
 determined by rotating the crank shaft slowly and noting the 
 position of the timing marks as above. The generator circuit 
 should be broken before connecting the battery to the ignition 
 system. One terminal of the testing circuit can be connected to 
 the metal of the motor, and the other terminal to the insulated 
 member of the ignition plug. 
 
CHAPTER X. 
 
 TROUBLES, REMEDIES AND REPAIRS. 
 
 141. When operated and cared for with as much care, skill, 
 and knowledge as are usual for steam engines and boilers, the 
 internal-combustion motor is as reliable as the steam power plant. 
 On account of the adoption of gas and oil motors to any con- 
 siderable extent being comparatively recent, as compared with 
 steam engines, they are not nearly so well understood by many 
 of those who operate them. 
 
 The aim of this chapter is to set forth some of the many troubles 
 met by the inexperienced, together with the means of preventing 
 most of them and of remedying the others. In many cases a 
 difficulty that seems insurmountable in the presence of ignorance 
 is really insignificant when understood. 
 
 The following detailed list of causes of trouble may seem long. 
 An equally long one can be made for steam engines and their 
 accessories. The writer has experienced more trouble with steam 
 engines than with internal-combustion motors, in proportion to 
 the number of each dealt with. 
 
 Conditions that Cause Trouble and Loss of Power. 
 
 142. Very few of these troubles ever occur in connection 
 with intelligent operation, ordinary care and good construction. 
 
 IN THE MOTOR. 
 Leaks between the combustion chamber and jacket space: 
 
 Cracked cylinder; 
 
 Leaky joint between cylinder head and barrel; 
 
 Loose plug in the cylinder wall; 
 
 Blowhole in the cylinder wall; 
 
 Porous casting. 
 
 210 
 
TROUBLES, REMEDIES AND REPAIRS 211 
 
 Leaks in the cylinder wall between the combustion space and 
 
 the atmosphere: 
 Ignition plug not in tight; 
 
 Loose insulation or leaky packing in the ignition plug; 
 Pet-cock partly open or not in tight. 
 
 Valve leaks : 
 Pitted valve; 
 Cracked valve; 
 Warped valve; 
 
 Flake of carbon under the valve; 
 Valve stem too long so that valve cannot rest on its seat. 
 
 Valve binding or sticking: 
 
 Carbon deposit on the valve stem; 
 
 Bent valve stem. 
 
 Valve spring weak or broken. 
 
 Piston leaks: 
 
 Scored (grooved) cut) cylinder wall and piston rings; 
 
 Piston rings broken, worn, or improperly fitted; 
 
 Carbon and gummy oil under the piston rings; 
 
 Cracked piston; 
 
 Blowhole in piston; 
 
 Carbon deposit on the cylinder and on the piston. 
 
 IN THE COOLING SYSTEM. 
 Insufficient water or oil for cooling. 
 Inadequate cooling (radiating) surface. 
 Leaky pump packing and joints. 
 Pump not operating properly. 
 
 Steam from hot cylinders forced back into the pump. 
 Air lock in the circulating system : 
 
 Large vertical reverse bends in the connecting pipes. 
 
 Clogged or stopped passages : 
 
 Packing or gasket squeezed out into the passage; 
 Loose lining in a rubber hose acting like a check valve; 
 Cotton waste, rags, etc., in the passages; 
 Short kinks in a hose or pipe so as to close the passage. 
 
212 THE GAS ENGINE 
 
 IN THE CARBURETER. 
 
 Passages clogged by particles of foreign matter (dirt, lint). 
 
 Water in the fuel reservoir of the carbureter. 
 
 Flooding on account of the float binding or sticking so as not 
 
 to rise and cut off the inflow of fuel. 
 Leaky or "water-logged" float. Causes flooding. 
 Valve of float leaky so as to allow flooding. 
 Binding or sticking of the air valve. 
 Broken spring on the air valve. 
 Frost and ice in the mixture passage. 
 Air lock prevents fuel from flowing into the carbureter after 
 
 it has been empty. 
 
 * 
 
 IN THE FUEL AND FUEL SUPPLY. 
 
 No vent in the fuel tank. 
 
 Air lock in the connections between the fuel tank and the 
 carbureter. 
 
 Pipes stopped by gaskets, short bends or kinks, lint, etc. 
 
 Water in the fuel. 
 
 Dirt in liquid fuel. 
 
 Dust and grit in the gas, as in imperfectly cleaned blast- 
 furnace gas. 
 
 Variation in the quality of the fuel (liquid or gaseous). 
 
 IN THE CONNECTIONS BETWEEN THE CARBURETER AND MOTOR. 
 
 Loose joints and holes through which air can leak into the 
 mixture. 
 
 IN THE IGNITION SYSTEM. 
 Spark plug defective or dirty: 
 
 Carbon and oil deposit in the spark gap or on the insulation; 
 Spark gap too wide or too small; 
 Carbon on the contacts of the low tension system; 
 Contact-points fuse so as not to make electric" contact; 
 Loose contact points; 
 
TROUBLES, REMEDIES AND REPAIRS 213 
 
 Water on the points. Generally due to a cracked cylinder 
 
 or blowholes in the cylinder casting; 
 Porcelain insulation cracked; 
 
 Mica insulation loose, open between the disks or crumbled; 
 Air leaks around the insulated parts. 
 
 Induction coil: 
 
 Contact points oxidized or fused so as not to make electric 
 
 connection ; 
 
 Dirt or other foreign matter between the contact points; 
 Contact points fused together; 
 Bent spring (vibrator, trembler, interrupter); 
 Loose contact points; 
 
 Loose connections or broken wires inside the coil box; 
 Defective or burned -out insulation in the coil box; 
 Difference of lag in producing sparks when two or more 
 
 coils are used on one motor. 
 
 Timer: 
 
 Dirt or grit between contact points; 
 
 Springs weak or broken; 
 
 Loose screws, rivets, etc.; 
 
 Rotor (rotating part) loose on its shaft; 
 
 Failure to make contact on account of worn parts; 
 
 Circuit closed at wrong time on account of worn or loose 
 
 parts. 
 Shaft not in continuous electric connection with the metal 
 
 of the motor on account of separation by oil or grease 
 
 (unusual); 
 Circuit not closed at the same relative position of each 
 
 piston in its stroke. 
 
 Battery: 
 
 Connections between two batteries made so that a current 
 
 flows when they are not in use; 
 Exhausted cells; 
 
 No insulation (paper, cardboard, glass, rubber, etc.) 
 between the metal of adjacent cells; 
 
214 THE GAS ENGINE 
 
 Binding posts of different cells touch each other; 
 Too many cells for the induction coil (too much voltage); 
 Cells not tightly secured to prevent shaking about and 
 breaking the connections between them. 
 
 Generator (magneto or electromagnetic): 
 
 Grease and dirt on the commutator; 
 
 Brushes worn or bent; 
 
 Commutator worn out of round, loose, or with poor insula- 
 tion; 
 
 Brushes binding in brush holder so as not to press on the 
 commutator; 
 
 Broken wires at the connections or inside the insulation; 
 
 Defective or burned-out insulation; 
 
 Loose parts; 
 
 Magnetism lost (infrequent). 
 
 Connections (electric): 
 
 Loose binding screws and joints; 
 
 Poor quality of insulation, especially on the high-tension 
 circuit ; 
 
 Broken wires at the binding posts; 
 
 Broken wires inside the insulation (sometimes very diffi- 
 cult to find); 
 
 Insulation chafed or worn off so as to allow electric contact 
 with metallic parts. This may be only intermittent on 
 account of a swinging or vibrating wire, or the movement 
 of a part such as a brake rod, clutch lever, etc. 
 
 Symptoms and Diagnoses. 
 
 143. Back-firing into the intake pipe and carbureter is generally 
 due to some of the following causes: 
 
 Lean mixture. A lean mixture may be due to leaks at the 
 joints of the intake pipe between the carbureter and motor, or 
 to improper adjustment of the carbureter. Water in gasoline 
 will cause a lean mixture temporarily; 
 
TROUBLES, REMEDIES AND REPAIRS 215 
 
 Carbon deposit on the piston head and the walls of the com- 
 bustion chamber; 
 
 Overheating of the cylinder, piston, ignition points or exhaust 
 valve, or of a projecting piece of metal in the cylinder; 
 
 Excessive rarefication of the charge by throttling or cutting 
 off the charge in the very early part of the intake stroke, and the 
 consequent slow burning; 
 
 Binding or sticking of the inlet-valve stem; 
 
 Weak spring on the inlet valve, especially if it is an automatic 
 valve; 
 
 A particle of carbon scale or other foreign matter under the 
 inlet valve; 
 
 It is impossible to prevent back firing when the amount of 
 mixture admitted for a charge is about as small as will ignite. 
 The remedy is either to cut off the charge completely or 
 to admit more. Misfiring is apt to accompany back firing 
 under this condition, and, less frequently, exhaust explosions 
 also occur. 
 
 If preignition occurs in connection with back firing, the cause 
 is either an overheated cylinder or other part in the combustion 
 space, or incandescent carbon in the cylinder. 
 
 If the gas valve or carbureter has not been adjusted and 
 operating satisfactorily, and back firing occurs when the charges 
 are not cut down excessively in amount, the carbureter or gas 
 valve may need adjustment. 
 
 If the carbureter has been operating satisfactorily, or the gas 
 valve (of a gas motor) has been adjusted, then : 
 
 Note whether the cooling water or cooling oil is excessively hot 
 or not circulating properly, and 
 
 Cut off the ignition completely from all the cylinders to see 
 whether the explosions continue after the ignition is cut off. 
 
 If the explosions continue after the ignition has been cut off 
 from all the cylinders, then there is either incandescent carbon 
 deposit in one or more of the cylinders, a hot point or projecting 
 piece of metal, or there is overheating. In case of continued 
 
2l6 THE GAS ENGINE 
 
 explosions, and if they do not continue in all the cylinders, 
 then: 
 
 Put on the ignition again and then cut it off from one cylinder 
 at a time, or in pairs, to determine where the ignitions occur 
 without the aid of the ignition apparatus. (See cutting out the 
 ignition.) 
 
 If the explosions do not continue after the ignition is completely 
 cut off, then: 
 
 Note the setting of the adjusting (needle) valve of the carbu- 
 reter, and then close and open it again quickly so as not to stop 
 the motor. This will generally remove dirt or other foreign 
 matter from the passage at the needle valve. 
 
 Drain the carbureter to remove water; 
 
 Strike the carbureter a sharp, light blow to shake the float loose 
 in case it is sticking in such a position as to keep the inlet valve 
 of the carbureter partly closed; 
 
 Open the gas valve (of a motor using permanent gas) to com- 
 pensate for the fuel becoming more lean; 
 
 Stop the motor and examine for a binding or sticking valve 
 stem or a weak spring on the inlet valve. 
 
 Test the compression. If it is very poor, then: 
 
 Turn the mechanical inlet valve around on its seat while 
 applying enough lifting force to it to allow it to press lightly on 
 its seat. The lifting force can be applied by the valve-lifting 
 cam by bringing the crank shaft to a position where the valve 
 just begins to leave or to settle on its seat; 
 
 Look for a cracked or broken inlet valve. 
 
 144. Misfiring not accompanied by other serious troubles, 
 but sometimes by exhaust explosions, is generally due to one or 
 more of the following causes : 
 
 Ignition adjustment or trouble; 
 
 Carbureter adjustment or trouble giving too rich a mixture 
 and causing carbon deposit in the cylinder; 
 
 Lubrication excessive or oil poor in quality for the purpose; 
 
 Valve troubles (infrequently). 
 
 If black smoke is discharged from the exhaust, adjust the 
 carbureter or the gas valve to cut down the fuel. 
 
TROUBLES, REMEDIES AND REPAIRS 217 
 
 If blue smoke is discharged, either cut down* the amount of 
 lubricating- oil fed to the cylinder or get suitable lubricating oil 
 for it. 
 
 Test the ignition system (see ignition system tests.) 
 
 Look for a weak exhaust-valve spring and for binding or 
 sticky exhaust-valve stems. 
 
 Test the compression. If it is poor, then: 
 
 Twist the exhaust valve around while it presses lightly on 
 its seat to remove flake carbon or other foreign matter from 
 under it; 
 
 Look for a cracked or broken exhaust valve; 
 
 Test for a cracked cylinder or a leaky plug in the cylinder wall 
 between the combustion chamber and water jacket. (See test 
 for cracked cylinder and loose plug.) 
 
 145. Continuous Pounding, Thumping, or Hammering on 
 Heavy Load. When not accompanied by other evidences of 
 trouble, this is generally due to one of the following faults : 
 
 Loose fit between the connecting rod and the crank pin or 
 
 the wrist pin (piston pin); 
 Loose bearings on the crank shaft; 
 Fly wheel loose on its shaft (loose key). 
 
 The piston, if rather loose in the cylinder, may also thump at 
 each explosion. This is not generally serious, although the noise 
 may be disturbing. 
 
 The first three of these troubles should be remedied as soon as 
 possible, for they are apt to be the sources of injury to the parts 
 on account of the heavy pressures produced when they strike 
 together at the time the sound is produced. The bearings are 
 generally constructed so that the lost motion can readily be 
 taken up. 
 
 146. Preignition and Sharp Snaps or Heavy Pounding in the 
 Motor. If the igniter is not set to give too early ignition, pre- 
 ignition is generally due to either an overheated cylinder, carbon 
 deposit, or hot ignition points or projections in the combustion 
 
21 8 THE GAS ENGINE 
 
 chamber. It also occurs when the motor compresses the charge 
 more than is allowable for the kind of fuel used. 
 
 If the cylinder is overheated, it may be on account of too late 
 ignition, too rich a mixture, or insufficient lubrication. The 
 exhaust pipe will generally be very hot (sometimes red hot) if the 
 ignition is too late or the mixture too rich. 
 
 Carbon deposit in the cylinder will cause preignition even if the 
 cylinder is not overheated or the cooling water or oil not hotter 
 than it should be. 
 
 In any case of preignition by means other than the early setting 
 of the ignition apparatus, the motor may continue running after 
 the ignition is cut off, and may kick if cranked soon after 
 stopping. (See carbon deposit and cooling-water troubles. ) 
 
 147. Power Decreases Rapidly at a Uniform Rate and the 
 Motor Stops. There may also be back firing and misfiring 
 just before the motor stops. This behavior may be due to some 
 of the following troubles: 
 
 No fuel; 
 
 Water in the carbureter. (Drain it out); 
 
 Valve suddenly jarred shut in the fuel pipe or the carbureter; 
 
 Broken connection in the fuel-supply pipe. 
 
 In an automobile this sudden loss of power will occur when the 
 fuel tank is rather empty and the car is run along the inclined 
 side of the road so that the end of the tank from which the fuel is 
 drawn is on the high side of the car. 
 
 It also occurs when the fuel (liquid) is low and the car turns a 
 curve at high speed so as to throw the gasoline away from the out- 
 let of the tank. The power may drop off and then come on again 
 quickly when this occurs. The action is especially noticeable 
 when climbing a grade. 
 
 The remedies to the above troubles are obvious. 
 
 To drain the water out of a carbureter, open the valve at the 
 bottom of the gasoline reservoir of the carbureter, or remove 
 the bottom plug. If there is no means of opening the bottom of 
 the carbureter for drainage, then remove the top and siphon the 
 water out with a bent tube or a piece of small rubber hose. Or 
 
TROUBLES, REMEDIES AND REPAIRS 219 
 
 it can generally be drawn out by closing the air. inlet with one's 
 hand while rotating the motor. The carbureter can be removed 
 and emptied without much trouble in some cases. 
 
 148. Power Decreases Slowly at a Uniform Rate and the 
 Motor Finally Stops. This may be accompanied by back 
 firing and misfires after the impulses have become quite weak. 
 
 These are the characteristic symptoms of no vent in the fuel 
 tank of a vapor motor with gravity feed, or of the fuel gas 
 growing poor when taken from a gas producer about as fast as it 
 is made. 
 
 The gradual jarring shut of a valve in the fuel-supply passages 
 has the same effect. 
 
 The opening up of a joint or a valve in a gas-supply pipe or 
 in the mixture passage, so that air is admitted, is another cause. 
 
 149. The Motor Behaves Erratically and the Timer Con- 
 trol Must be Set Differently from Usual Position to get the Best 
 Results. When the timer rotor (rotating part) is very loose 
 on its shaft these results often occur. They are apt to be accom- 
 panied by preignition, back firing, and misfiring. If the tinier 
 rotor takes a permanent position for a while and the control 
 agrees with it the motor will pull well. But when the rotor keeps 
 moving on its shaft the power may be good for a while, and 
 then erratic action will begin. 
 
 150. The Motor does not Develop Full Power at any Time. 
 When not accompanied by other symptoms, such as back firing, 
 misfiring, overheating, etc., this is generally due to one of the 
 following causes: 
 
 Insufficient lubrication, especially of the cylinder; 
 Piston leaks; 
 Valve leaks; 
 
 Particle of carbon under a valve; 
 
 Leaks from the cylinder into the atmosphere through or 
 around the spark plug, pet -cock, etc. 
 
 The motor can be tested for some of the leaks while running 
 (see running test), or some one of the compression tests can be 
 applied (see compression tests). 
 
220 THE GAS ENGINE 
 
 In the case of a leaky valve it should be turned around while 
 pressing lightly on its seat in order to remove a particle of carbon 
 that may have lodged under it. 
 
 151. The Motor Runs Well for a While, then Loses Power 
 and the Cooling Water Heats Unduly. These are the symptoms 
 of an opening between the combustion chamber and the water 
 jacket. The opening may be on account of a loose plug in the 
 cylinder wall or of a cracked cylinder. In such cases the 
 opening closes up sometimes when the motor is cool, but opens 
 out when it becomes hot. 
 
 The opening allows the hot gases of combustion to pass out 
 into the cooling water and heat it, and also, during the suction 
 stroke, some of the water or steam to be drawn into the com- 
 bustion chamber from the water jacket. The water thus drawn 
 into the cylinder is almost certain to cause misfiring. 
 
 After the motor has been stopped for a while and allowed to 
 cool down, it will sometimes run well again for a short time and 
 then behave as before. 
 
 If the crack or opening is rather large, there will be consider- 
 able loss of compression and power even when the motor is cool. 
 
 Any of the hand or the stationary tests for compression and 
 leaks can be applied, but in case they do not show leaks between 
 the combustion chamber and the water jacket, then 
 
 Apply the running test for a cracked cylinder and loose plug. 
 
CHAPTER XI. 
 TESTS OF IGNITION SYSTEMS. 
 
 152. Test of High -Tension (Jump-Spark) Ignition System 
 with Individual Induction Coils and Duplicate Batteries. [The 
 test when the primary current is furnished by an electric generator 
 (magneto) is practically the same as the one given below, but the 
 motor must be kept running if the generator is of the rotary 
 type.] 
 
 It is assumed that one of the batteries is held as a reserve and 
 the other used till exhausted, then a new battery put in and 
 the old reserve one used for the regular service. 
 
 Switch on the reserve battery while the motor is running. An 
 exhausted dry-cell battery often works well for a short time after 
 a considerable period of rest and then fails gradually. 
 
 Press down the tremblers (vibrators, interrupters) one at a 
 time, or in pairs, to find the cylinder in which the misfiring occurs. 
 This can be done with the fingers. 
 
 Note whether all the tremblers vibrate strongly. If this cannot 
 be done while the motor is running, stop it and either rotate it 
 slowly by hand or close the battery circuit for each coil in turn by 
 placing a piece of metal (wire, screw-driver, etc. ) so as to connect 
 the timer terminal of each coil, one at a time, to the metal of the 
 motor or to the battery terminal of the timer. 
 
 If all the tremblers have weak action, then look for loose 
 connections at the battery and between the timer and the induc- 
 tion coil. Examine the battery (low-tension, primary) circuit 
 for bare places and wires broken inside of the insulation. See 
 that there is good metallic (electric) connection between the rotor 
 of the timer and the metal of the motor, or, in the case of a rotor 
 that is insulated from its shaft, that the contact is good between 
 the metal of the rotor and the part to which the wire from the 
 battery is electrically connected. 
 
 221 
 
222 THE GAS ENGINE 
 
 If only one trembler has weak action (or, more strictly, if not 
 all), then look for bare and broken wires and loose connections 
 between it and the timer. Clean the contact points of the 
 trembler and notice whether they are loose. (See induction-coil 
 troubles.) Close the circuit at the timer as before and look for 
 troubles in the circuit for the coil under inspection. (See induc- 
 tion-coil troubles.) 
 
 Test each spark plug and its wire in turn as follows: 
 Disconnect the high-tension (secondary) wire from the spark 
 plug, hold the end of the wire about one-quarter of an inch from 
 the metal of the motor or of the spark plug, and close the primary 
 (battery) circuit for that plug. A spark should jump the 
 quarter-inch air gap between the end of the wire and the motor 
 or spark plug. If no spark jumps, look for poor insulation on 
 the secondary (high-tension) wire under test; 
 
 Remove the spark plug from the motor, connect the high- 
 tension wire to it again, place the outer metal of the plug against 
 the metal of the motor, and close the primary circuit for the plug 
 under test. If both sides of the spark plug are insulated and a 
 wire leads to each side, it is not necessary to make contact with 
 the metal of the motor for this part of the test. There should be 
 a strong spark across the air gap of the plug. The spark may not 
 jump the gap when the plug is in the motor, however, even though 
 it is strong outside, for the reason that the resistance to its 
 jumping is much higher in the compressed charge in the motor 
 than in the open air; 
 
 Separate the spark points, if possible, so as to have a spark gap 
 of one-eighth inch or slightly more, and test again as before. 
 There should be a strong spark. Put the points back so as to 
 have a spark gap of about one-thirty-second (Jg-) of an inch. 
 
 If the spark is weak, clean the plug (see cleaning spark plug) 
 and test it again as above. If the result is not satisfactory, then : 
 Put in a new plug, or new insulation in the old one; 
 Test the timer for uniformity of the time of ignition. (See 
 comparing the time of ignition in different cylinders. ) 
 
 153- Test of High-Tension Distributer Ignition System with 
 Duplicate Batteries. (When the primary current is furnished 
 
TESTS OF IGNITION SYSTEMS 223 
 
 by a generator, the test is the same except that the motor must be 
 kept running if the generator is of the rotary type.) 
 
 Switch on the reserve battery. 
 
 Cut off the ignition from the cylinders, one at a time or in pairs, 
 while the motor is running, by short-circuiting the spark plug to 
 determine which cylinder is misfiring. The short-circuiting of 
 the spark plug can be done with a wooden-handled screw-driver 
 placed against both the insulated central part of the plug and 
 the metal of the motor, or across the insulated parts of the plug 
 if both terminals are insulated. Care should be taken to hold 
 the tool by the insulated part to avoid a shock, which, while not 
 at all dangerous, is startling. 
 
 If there is misfiring in all of the cylinders, then : 
 
 Look for loose connections in the battery and the battery 
 
 circuit ; 
 Rotate the timer and distributer arm and notice whether 
 
 the arm comes near or opposite the high-tension terminals 
 
 at the instant the timer closes the primary circuit; 
 Clean the vibrator (trembler, interrupter) contacts and note 
 
 whether the spring is bent; 
 Test each spark plug and its connections as in the latter 
 
 part of the preceding section. 
 
 (See also "comparing the time of ignition in different cylin- 
 ders.") 
 
 If the misfiring does not occur in all the cylinders, then : 
 
 Examine the timer contacts for the cylinder that misfires; 
 Apply the spark-plug test as in the preceding section. 
 
 154. Test of High-Tension Magneto Ignition System. Short- 
 circuit the spark plugs, one at a time or in pairs, as in the pre- 
 ceding section, to locate the misfiring. 
 
 If the misfiring is general, examine the magneto, especially 
 the moving contacts, screw fastenings, and the connections. (See 
 magneto test.) 
 
224 THE GAS ENGINE 
 
 If the misfiring is confined to only a portion of the cylinders, 
 apply the spark-plug test. (See individual induction-coil system. ) 
 
 (Also see " comparing the time of ignition in different cylin- 
 ders.") 
 
 155. Test of Low-Tension Arc-Ignition System. This test 
 applies more especially when the electric generator is of the 
 rotary type, but will also answer for the oscillating magneto 
 generator. 
 
 Cut out the ignition from the cylinders successively to find 
 which is misfiring. This can be done by opening the switches 
 near the ignition plugs, or by disconnecting the wires at the 
 plugs. 
 
 If the misfiring is general, then : 
 
 Examine the generator for worn or loose brushes, com- 
 mutator worn out of round, dirt on the commutator, 
 loose connections, etc. (See electric-generator test); 
 
 Clean the spark plugs; adjust the contacts to bring fresh 
 parts together; 
 
 Examine the spark plugs for weak springs and worn parts. 
 
 (Also see "comparing the time of ignition in different cylin- 
 ders.") 
 
 If the misfiring is in only one cylinder, then make the tests 
 just given, but reserve the examination of the generator till the 
 last. 
 
 156. Test of Magneto Direct-Current Electric Generator. - 
 The following tests can be applied without the aid of much appa- 
 ratus in case the generator fails to operate satisfactorily. They 
 apply especially to a magneto which has a commutator with 
 several segments. 
 
 See that the brushes press against the commutator so as to 
 make good contact. They may be worn out or bind in the brush 
 holder. 
 
 Note whether the commutator is round and runs true. 
 
 See that the brushes have good contact with their holders. 
 
 Examine the commutator for a segment with a blackened or 
 fused edge. This may be caused by a broken or loose connec- 
 
TESTS OF IGNITION SYSTEMS 225 
 
 tion between the segment and the armature winding, or by a 
 partly burned out armature coil. The edge of the segment 
 which passes under the brush immediately before one that is 
 dead (connection broken) is the one that is affected. 
 
 Look for loose and broken connections in both the generator 
 and the outside circuit. 
 
 A completely burned out coil can generally be readily seen by 
 an examination of the outside of the armature. 
 
 See that the commutator is clean and free from grease and 
 dirt. It can be cleaned by holding a piece of fine sandpaper 
 (not emery paper or emery cloth) against it while running. It 
 is advisable to lift the brushes while cleaning the commutator 
 in this manner. Do not use gasoline to cut the gum. It will 
 be ignited by the spark at the brushes. 
 
 Test the strength of the magnet by placing a piece of soft 
 steel or iron (as a steel nail, door key, screw-driver) against one 
 of the poles (ends) of the magnet. The magnet should be 
 strong enough to hold the nail tight, even to hold it out horizon- 
 tally from a flat surface, especially if the armature of the gener- 
 ator has been removed. No other metal or non-ferrous alloy 
 will do for this test. 
 
 A weak magnet can be permanently magnetized, if it is steel 
 that is hardened very hard, by the application of a powerful 
 magnet. An electromagnet is best for this purpose. To remag- 
 netize, place one pole of the electromagnet (say the north pole) 
 near the middle of the permanent magnet and draw the electro- 
 magnet along the metal in the direction toward the end of the 
 hard steel, keeping the two magnets in contact during the mo- 
 tion. Then place the other (south) pole of the electromagnet 
 near the middle of the permanent magnet and draw the electro- 
 magnet along to the other end of the hard steel. By repeating 
 these operations several times the hard steel will be fully mag- 
 netized and will remain a strong permanent magnet if the steel 
 is hard enough, unless some demagnetizing influence other than 
 that of the armature currents in regular service acts on it. Soft 
 steel will not retain sufficient magnetism for a magneto generator. 
 
 The following test can be made with a portable magneto such 
 
226 THE GAS ENGINE 
 
 as is used with telephones in which the magneto crank is turned 
 to ring the bell when calling central : 
 
 Disconnect all wires, etc., leading out from the magneto to 
 the exterior circuit. 
 
 Lift the brushes from the commutator. Connect the terminals 
 of the portable magneto to the brushes, one terminal to each 
 brush (of the two). The bell of the testing magneto should not 
 ring when the crank of the testing magneto is turned rapidly (or 
 otherwise). If the bell rings, the insulation of the brushes is 
 poor. Test the insulation between the armature shaft and the 
 brushes in the same manner. If the bell rings in either case, 
 remove the brushes or brush holders and clean the insulation 
 carefully. 
 
 Connect one terminal of the testing magneto to the armature 
 shaft of the generator and the other terminal to several of the 
 commutator segments in succession while turning the crank of the 
 testing magneto. Turn the testing magneto rapidly. If the bell 
 rings there is poor insulation between the armature winding and 
 the armature core. The remedy for this is to partly or wholly 
 rewind the armature. Some armatures are made so that a section 
 or coil of the winding can be removed and another section put in 
 its place without disturbing the other sections. 
 
 A broken or loose connection may make intermittent contact 
 and cause erratic behavior of the generator. 
 
 Put one of the brushes down against the commutator so that 
 it has good contact (the brush can be held as usual in its holder), 
 connect one terminal of the testing magneto to the brush, and 
 place the other terminal against the commutator segments, one 
 at a time. The brush and the terminal should not touch the 
 same segment. The armature must be rotated part of a revolu- 
 tion in order to test all the segments individually. The testing 
 magneto should be turned only fast enough to make the bell ring. 
 If there is a dead segment, the bell will not ring when the testing 
 terminal is in contact with it. It should ring for all the live 
 segments. The dead segment indicates a broken or loose con- 
 nection between it and the armature. More rapid turning of 
 the testing magneto may produce a pressure sufficient to send 
 
TESTS OF IGNITION SYSTEMS 22/ 
 
 enough current across a break whose parts are onjy an extremely 
 minute distance apart, to ring the bell. 
 
 A further test for a broken commutator connection can be 
 made with a galvanic cell (not a storage cell) or some other source 
 of electric energy of very low voltage and small current capacity. 
 An ammeter suitable for measuring very small currents (milli- 
 ammeter) should be placed in the circuit. The test can then be 
 made as before by connecting one terminal of the cell to the brush 
 that is in contact with the commutator and the other terminal to 
 the commutator segments in turn. The amount of current should 
 be noted in each case. If the broken parts are pressed but very 
 lightly together, the current for the corresponding segment will 
 be smaller than for the others. Due allowance must be made 
 for the dropping off of the current capacity of the cell on account 
 of polarization, etc. 
 
 Defective insulation between the different turns of the wire of 
 an armature coil or section cannot readily be determined by an 
 electric test with the more common electric instruments unless 
 the armature sections or coils are disconnected from the com- 
 mutator and from each other. Even then the measurement is 
 one of electric resistance and generally requires delicate apparatus 
 such as is used only in laboratories and electric works. 
 
 157. Test of Direct-Current Electro-Magnetic Generator. 
 Except the test of the field winding for magnetizing the soft 
 steel or iron magnet cores and poles, this test is practically 
 the same as for a magneto generator as given in the preceding 
 section. 
 
 The test of the insulation and for broken wires in the field coil 
 can be made first with a portable magneto. The terminals of 
 the field winding should first be disconnected from the other 
 parts, and then the tests made between the terminals of the 
 winding, and also between the winding and the metal of the 
 generator. 
 
 To determine whether there is a short circuit in the field winding 
 the electric resistance of the coils can be measured and compared 
 with what it was when the coils were new. The old and new 
 values should be the same, after corrections have been made for 
 
228 THE GAS ENGINE 
 
 differences of temperature. Laboratory or factory instruments 
 are needed for the latter test. 
 
 If the magnets have not retained enough magnetism to cause the 
 generator to "pick up" and produce pressure and current, they 
 can be remagnetized by sending a current from a battery or other 
 source through the field winding. This will remagnetize the field 
 magnets. Care should be observed to have sufficient resistance 
 in the magnetizing circuit while doing this, in order to prevent 
 burning out the field winding by too great a current. An incan- 
 descent lamp, or two or more lamps in parallel, will answer if 
 the current is taken from a commercial lighting circuit. Only 
 circuits having direct current can be directly utilized (without a 
 rectifier). Water resistance will answer in any case. Put a 
 little acid in the water if enough current will not flow through 
 pure water. The electromagnets are generally not very strong 
 when the generator is not running. 
 
 158. Tests of Shuttle- Wound Electric Generators. Most of 
 the oscillating electric generators and those used in connection 
 with transformer (induction) coils without vibrators (tremblers, 
 interrupters) belong to this class. The tests in case of trouble 
 are of the same nature as those already given, but simpler. By 
 following such parts of these tests as apply to the case in hand 
 the desired results can be obtained. 
 
 When one terminal of the single-coil armature winding is con- 
 nected to the armature shaft, the test for the insulation of the 
 winding from the core cannot be made unless this connection is 
 opened up for the purpose. 
 
 159. Test of Shuttle- Wound Oscillatory Armature Generators. 
 A permanent magnet (or magnets) is used on this type of 
 
 generator, and the armature is generally shuttle wound with only 
 one coil. Ordinarily the current is taken off either by a pair of 
 insulated collector brushes in contact with a corresponding pair 
 of insulated slip rings, or one end of the armature winding is 
 connected to the armature shaft, which has metallic connection 
 to the frame of the machine, and the other end of the armature 
 wire is connected to a slip ring on which a collector brush rests. 
 When the armature coil is connected to the shaft electrically, the 
 
TESTS OF IGNITION SYSTEMS 229 
 
 test of the insulation between the winding and the armature core 
 cannot be made until the connection to the shaft is broken 
 (electrically). Otherwise the test is the same in general as 
 already given (see 156), except that there is only one ring 
 or a pair of rings, instead of several segments of a commutator. 
 
 1 60. Tests of High-Tension Electric Generators. The gen- 
 erators of this class are so varied in form that it is hardly possible 
 to give directions that will apply generally. 
 
 The tests really amount to a combination of those for a gen- 
 erator, a timer, and an induction coil or transformer coil. By 
 combining such parts of these tests as apply to a particular 
 machine, a complete test can be made. 
 
 In a magneto generator whose armature is stationary, and 
 whose rotor or oscillator is a permanent magnet without any wire 
 winding, the sources of trouble are reduced to a minimum. The 
 armature test for it is similar, but simpler than when the arma- 
 ture rotates. The test for magnetism can be applied after 
 removing the magnet, sometimes without removing it. 
 
CHAPTER XII. 
 TESTS FOR AIR AND GAS LEAKS IN MOTOR. 
 
 161. Examination for Leaks while the Motor is Running in 
 Regular Service. To detect a leak at the spark plug or other 
 form of ignition apparatus, at a plug or other stop to an opening 
 in the cylinder, or at any part of the cylinder that is accessible, 
 put a plentiful supply of the cylinder lubricating oil where the 
 examination for the leak is to be made, while the motor is running. 
 Bubbles will appear where there is a leak if it is not so great as 
 to blow off the oil. The oil may be drawn into the cylinder to 
 some extent if the leak is large. 
 
 A piston leak of any considerable extent allows smoke to blow 
 out around the piston during the impulse stroke. The smoke 
 is especially noticeable when the combustion mixture is over 
 rich or there is too abundant lubrication. It may be necessary 
 to remove part of an enclosed crank case to see the end of the 
 piston. 
 
 A cracked or porous cylinder, or a leaky plug in the cylinder 
 wall between the combustion chamber and the water jacket, 
 allows gas to pass from the combustion chamber into the jacket 
 water during the compression and the impulse strokes. If a 
 cooling tank is used, bubbles will appear where the hot water 
 flows into the tank at the end of the pipe that carries the water 
 from the motor to the cooling tank, provided that the opening 
 of the pipe is entirely submerged. Bubbles may appear here 
 on account of air carried into the jacket space with the cooling 
 water. A chemical analysis will determine the nature of the 
 gas in the bubbles. Air is not apt to be carried into a thermal 
 circulating system. A piece of glass tube interposed in the 
 pipe that leads from the water jacket affords a means of detect- 
 ing bubbles in the water. The glass should not be placed so near 
 the motor as to show steam bubbles that have not had time to 
 
 230 
 
TESTS FOR AIR AND GAS LEAKS IN MOTOR 231 
 
 condense. A glass jar filled with water and held inverted over 
 the outlet of the submerged pipe with most of the jar above the 
 water level can be used to determine whether the bubbles are 
 steam. 
 
 162. Running Test for a Cracked Cylinder, Porous Metal, 
 Leaky Plugs, and Leaks into the Jacket Space. The motor 
 should be cool at the beginning of the test, and the following 
 preparations should be made before starting the motor: Dis- 
 connect the driving mechanism of the circulating pump and 
 remove the pipe connected to the water outlet at the top of the 
 jacket. Fill the jacket space full of water till it stands level 
 with the top of the opening. If the motor is small, rotate or 
 crank it by hand and note whether bubbles rise through the water. 
 If the combustion chamber is plugged at the top, it can generally 
 be observed whether the bubbles, if any, come from around the 
 plug. 
 
 Start the motor and observe as before. If the water vibrates 
 too much for the observation, a piece of glass can be placed over 
 the opening with the water high enough to keep it in contact 
 with the glass. Water may be flowed in slowly at the bottom 
 of the jacket and allowed to escape under the glass. The load 
 on the motor should be increased to the full capacity of the motor 
 without much delay. Small bubbles of air will soon begin to 
 form on the cylinder wall on account of the heat, as they do in 
 a glass of water standing for some time on a warm day, and 
 finally steam bubbles will form unless the water is allowed to 
 flow rapidly enough to keep it below the boiling temperature. 
 The air and steam bubbles must not be taken for gas from cylinder 
 leaks. 
 
 In an oil-cooled motor the test is the same, except the use of 
 oil instead of water. 
 
 163. Hand-Compression Tests for Cylinder and Piston Leaks 
 in Small Motors. Cut out the ignition, open the pet-cocks to 
 the combustion chamber, and rotate the motor to see that it moves 
 freely. Close the pet-cock of the cylinder to be tested. Rotate 
 again till the compression stroke is nearly completed, hold the 
 crank shaft in this position and note whether the effort necessary 
 
232 THE GAS ENGINE 
 
 to hold it grows less on account of leakage. The crank shaft 
 may also be worked back and forth to move the piston in and 
 out. Note whether the compression resistance decreases during 
 this action. If the compression resistance decreases more 
 rapidly when the piston is moved than when it is held still at 
 nearly the completion of the compression stroke, then the piston 
 leaks more at nearly the middle of its stroke than at and near 
 the end of the compression stroke. 
 
 In case the compression falls rapidly, the valves can be roughly 
 tested for leaks by holding a piece of thin cloth or tissue paper 
 over the end of the exhaust port while the piston is held stationary 
 near the end of the compression stroke. This will hardly give 
 definite results if the exhaust pipe has leaks. In such a case the 
 exhaust pipe can be removed and the paper or cloth held near 
 the opening, or the caps over the valves can be removed and the 
 valves tested by putting oil, kerosene, or water around or over 
 them, or talc powder or pulverized soapstone around the edges. 
 A piece of sheet rubber held tightly over the exhaust opening, as 
 by pressing a ring against it, will be bulged out by the gas that 
 escapes through a leak. It may be necessary to prevent escape 
 of gas around the stem of a mechanically operated valve by 
 closing the crack with thick grease. 
 
 Leaks from the cylinder into the water jacket can be detected 
 by noting whether bubbles escape into the cooling tank or rise 
 through the water in the jacket when the pipe is disconnected 
 from the top of the jacket. The circulating pump should not 
 rotate during this part of the test. (See preceding section.) 
 
 Leaks in the spark plug, pet -cock, or other stopped openings 
 into the cylinder can be detected by putting oil around the 
 parts. 
 
 This test does not show whether the piston is tight when well 
 out on the impulse stroke or during the early part of the compres- 
 sion stroke. 
 
 164. Compressed- Air Test for Leaks. The air pressure for 
 this test should be about the same as the explosion pressure of 
 the motor. A pressure of 350 pounds per square inch is sufficient 
 for all motors except those in which air alone (and residual gases) 
 
TESTS FOR AIR AND GAS LEAKS IN MOTOR 233 
 
 is compressed in the combustion space before the fuel is admitted 
 to it, as in the case of one type of oil motor. 
 
 The connections for supplying the compressed air to the motor 
 cylinder can be made by removing the cylinder pet -cock, the spark 
 plug or other ignition apparatus from the cylinder and then 
 connecting the compressed-air pipe to 'the opening. 
 
 Set the motor with the piston in position to begin the impulse 
 stroke and lock the fly wheel so that it cannot rotate. Put on the 
 full pressure of the air and examine for leaks by 'the methods 
 already described (see preceding section and others). 
 
 Release the pressure from the motor cylinder and rotate the 
 crank a little in the direction that it runs. Lock the fly wheel 
 again and apply air pressure as before, but the full pressure need 
 not be applied if the piston is about one-eighth of the way out on 
 its stroke. A somewhat less air pressure will do for this position. 
 
 Repeat the tests through the full stroke of the piston. 
 
 The pressure can be gradually reduced to about 125 pounds per 
 square inch at mid-stroke, and on down to 50 or 60 pounds at the 
 end of the stroke. 
 
 It is generally difficult to observe directly whether the piston 
 leaks on a standing test (motor not running). The elimination 
 of other leaks is the method to be followed in such a case, until 
 it is known that there is no leak at any other place. 
 
 If the cylinder has been detached from the frame of the motor 
 and is small enough to be immersed in water, the piston can be 
 held in by a wooden block and bolts while the air pressure is 
 applied. Bubbles will then appear at every leak. The piston 
 can be set at different positions and the air pressure regulated 
 accordingly as above. 
 
 165. Hydrostatic Test for Piston and Cylinder Leaks. Water 
 or oil pressure can be applied to the interior of the cylinder in the 
 same manner as compressed air, as just described. 
 
 In applying the hydrostatic test the pipe should be disconnected 
 from the bottom of the jacket space and the water or oil drained 
 out. Then if there is a leak from the cylinder into the jacket 
 space, the water will run out at the bottom opening of the jacket 
 space. The caps over the valves, etc., should be removed to 
 
234 THE GAS ENGINE 
 
 allow the parts which may leak to be seen as far as possible. 
 Piston leaks are clearly shown. 
 
 Thin oil or kerosene may be used instead of water. The 
 kerosene will pass through openings that will retain water when 
 the parts are oily or greasy. 
 
 The joints of commercial motors are seldom tight enough to 
 warrant testing in the above manner with gasoline, and its use 
 cuts the oil away so completely from the cylinder bore and piston 
 rings that there is apt to be cutting between them afterward. 
 
CHAPTER XIII. 
 CLEANING AND MISCELLANEOUS. 
 
 166. Carbon Deposit in the Cylinder. When the combustible 
 mixture is too rich, or when an unsuitable quality of lubricating 
 oil is used, some carbon is always deposited on the cylinder walls 
 and piston head. The rate at which it is deposited depends on 
 the richness of the combustible mixture and the amount and 
 unsuitability of the oil used in the cylinder. 
 
 The carbon is deposited in two forms. Some is soft like soot 
 and some hard like coke. 
 
 The soft carbon mingles with the gummy residue of the lubri- 
 cating oil and adheres to the walls of the combustion chamber 
 and to the spark plug. If the lubricant is poor and insufficient 
 in quantity, the soft carbon is deposited to some extent on the 
 walls of the bore of the cylinder over which the piston passes. 
 This does not occur with good oil plentifully applied. 
 
 The hard carbon forms chiefly at the hottest parts of the motor, 
 and especially where the incoming mixture impinges against hot 
 parts, as against the piston of a small motor. It always forms 
 with an uneven, jagged surface, and often collects in lumps. 
 
 The carbon, especially the hard lumps, may become heated 
 to a glowing temperature when the motor is working hard. 
 When thus heated, the carbon will cause back firing and pre- 
 ignition. The preignition has the same effect as advancing the 
 timer or igniter too far. The back firing is caused by the incom- 
 ing charge striking the incandescent carbon. The incandescent 
 carbon will often cause the motor to continue running after the 
 regular ignition is completely cut out. 
 
 "Kicking" when starting the motor soon after stopping and 
 while it is still hot is another result of hot carbon deposit. 
 
 The soft, gummy mixture of carbon and oil residue between 
 the piston and the cylinder wall increases the frictional resistance 
 
 235 
 
236 THE GAS ENGINE 
 
 of the motor, and thus reduces its effective power, at the same 
 time increasing its tendency to heat, both on account of the 
 increased frictional resistance and the larger or more frequent 
 charges of combustible that must be used to overcome the friction. 
 It also works around and under the piston rings so as to counter- 
 act their elastic action and prevent close conformation to the 
 cylinder bore, thus causing leakage around the piston and loss of 
 power. 
 
 A badly gummed piston offers considerable resistance to the 
 rotation of the motor. The ease with which a small motor can 
 be rotated by hand is an indication of the condition of cleanliness 
 and lubrication of the piston. 
 
 The carbon and oil sometimes collect on the stem of the 
 exhaust valve and become baked so as to form a hard coating 
 that causes the stem to bind in its guide. Except in the case of 
 continued back firing, the inlet -valve stem does not become 
 carbon coated to an appreciable extent. 
 
 A sudden loss of compression and power in the motor is some- 
 times caused by a 'flake of the hard carbon detaching itself and 
 lodging under one of the valves, generally the exhaust valve. 
 The effect of this is the more noticeable the fewer the number 
 of combustion chambers in the motor. 
 
 Scoring of the piston and cylinder may be caused by a loose 
 flake of the carbon getting between them. This is very unusual 
 when the lubricating oil is of the right quality and enough is 
 applied. 
 
 A liberal supply of suitable lubricating oil while the motor is 
 running will generally remove the carbon deposit from the valve 
 stem and from between the piston and cylinder. After the motor 
 has been stopped and cooled so as not to be very hot, kerosene 
 can be applied for the same purpose, or gasoline may be used on 
 an entirely cool motor. Kerosene left standing in the cylinder 
 will dissolve the gum in a few hours. Slow rotation of the motor 
 helps to cut out the deposit rapidly. The motor should be well 
 lubricated before starting it after cleaning the cylinder with 
 kerosene, and especially after using gasoline for cleaning. 
 
 Scraping and rubbing is the only method of removing the hard 
 
CLEANING AND MISCELLANEOUS 237 
 
 carbon deposit from the combustion chamber walls and piston 
 head. It cannot be dissolved by anything that can be safely or 
 economically used in the cylinder. 
 
 167. Cleaning the Spark Plug. When the insulation of a 
 spark plug is covered with a coating of carbon and oil, it can 
 generally be cleaned, if accessible, with gasoline and a bristle 
 brush or a piece of cloth and a string for getting into the angles. 
 A wire brush should not be used, for it is apt to scratch and 
 roughen the insulation so that it will gather and hold dirt and be 
 impossible to clean again. Mica insulation should not be scraped 
 with a knife under any circumstances, and the use of a knife 
 must be with care even on porcelain. Foreign matter on the 
 metallic points is not harmful except when it is between the 
 ignition points or contacts. 
 
 Porcelain insulation can sometimes be successfully removed 
 for cleaning it if the plug is not too old in service. The writer's 
 experience in this direction has been that the porcelain generally 
 sticks and binds so tight that it is necessary to break it in order 
 to remove it from the rest of the plug. A new porcelain can be 
 put in its place, which is better and not expensive. 
 
 1 68. Pitting and Warping of the Exhaust Valve. When the 
 ignition is late or the mixture is over rich, the flame is still burning 
 in the cylinder when the exhaust valve is opened. The flame then 
 passes out into the exhaust passages and heats the exhaust valve 
 to a high temperature. The high temperature has a tendency 
 to warp the valve, whatever its material. The combined heating 
 and erosive action of the escaping burning gases often produce 
 small pits and shallow cavities in the part of the valve that rests 
 on the seat when the valve is closed. Forged-steel valves are more 
 subject to pitting than cast-iron ones. 
 
 Pitting is apt to cause leakage at the valve, although a valve 
 may sometimes be very much pitted and still remain tight. The 
 pits are more or less circular in shape, and one may form in the 
 middle of the bearing surface without extending to either edge, or 
 in one side of the bearing surface without extending across it. 
 Warping is certain to cause leakage and loss of power. 
 
 The remedy is to regrind the valve. 
 
238 THE GAS ENGINE 
 
 169. Regrinding a Leaky or a Pitted Valve. Mix a finely 
 granulated or pulverized abrasive, such as emery, ground glass, 
 etc., with vaseline or grease. Stop the port with a piece of cloth 
 or waste, if possible. It may be necessary to remove the valve to 
 do this. 
 
 Place a small amount of the grinding mixture on the bearing 
 surface of the valve. Put the valve back in place (if it has been 
 removed) and rotate it back and forth with an oscillatory motion 
 a few times while applying a slight pressure to hold it against its 
 seat. The movements in one direction may always be a little 
 less than in the other, so that the valve is slowly turned around as 
 well as oscillated. Lift the valve slightly from its seat frequently 
 to allow the abrasive to get between the bearing surfaces. A 
 light spring placed under the valve is convenient for lifting it 
 when the pressure is removed. It is not advisable to rotate the 
 valve through complete revolutions in either direction, for such a 
 movement is apt to make scratches completely around the bearing 
 surfaces. An exception to this may be a valve that is in extremely 
 bad condition from pitting or warping, etc. In such a case the 
 grinding may be more rapid at first by rotating several times first 
 in one direction and then in the other, lifting the valve from its 
 seat at each reversal of the motion. 
 
 Remove the valve and examine it frequently to see how the 
 grinding is progressing. The bearing surfaces take on the same 
 dull appearance all the way around when the grinding becomes 
 uniform and they are nearly or quite fitted together. 
 
 Badly pitted or warped valves can be ground to advantage in 
 a lathe or grinding machine with an emery wheel (or other 
 abrasive wheel), then finished in place as above. 
 
 If the valve is oscillated in the same position always, the sur- 
 faces may become ground off more in some places than in others. 
 The valve will then fit in some positions but not in others. 
 
 An abrasive two or three grades coarser than flour emery may 
 be used at first, and a finer grade to finish. The coarse grade 
 should be removed before putting on the fine. 
 
 Great care should oe exercised to prevent the aorasive from 
 getting into the ports of the cylinder, especially the inlet port. 
 
CLEANING AND MISCELLANEOUS 239 
 
 The parts should be cleaned with extreme care aj the completion 
 of grinding. Any abrasive that enters the cylinder will cut and 
 score it, and cause rapid wear and piston leaks. 
 
 170. Running the Motor with a Disabled Valve or Valve 
 Spring. If a valve of one of the cylinders of a motor with more 
 than one combustion chamber is broken or disabled, or the valve 
 spring useless, the motor can be run in a disabled condition by 
 permanently closing the inlet port of the combustion chamber 
 whose valve is disabled. It is generally advisable to close the 
 exhaust port also to prevent scale and carbon from being drawn 
 into the cylinder through it. 
 
 The port can be closed by putting a piece of sheet metal or 
 strong gasket material, in the form of a blank gasket, in place 
 of the regular gasket in the joint of the connection near the motor. 
 Or, if the valve stem is the part broken, the valve can be clamped 
 down against its seat by removing the cap from over the valve and 
 putting a piece of wood on the valve and then clamping it down 
 by replacing the cap. When the inlet valve is automatic and 
 located opposite the exhaust valve (so that the two open toward 
 each other) the block can be placed between them. In any 
 method of blocking down a mechanically operated valve, the 
 means of lifting it should be removed before blocking it down. 
 
 The compression of the disabled cylinder can be relieved by 
 removing the spark plug, if thought necessary. 
 
 A broken coiled valve spring can sometimes be kept in use by 
 placing a washer-shaped piece of stiff material around the valve 
 stem and between the broken parts of the spring. A round, 
 flanged (shallow cup shaped) piece with a hole in the center 
 may serve better if the coil of the spring is of large diameter in 
 comparison with that of the valve stem; or a flat disk of metal 
 slitted radially from the edge inward a short distance at several 
 places, and part of the strips between the slits bent up and the 
 others down so that they will fit over the outside of the broken 
 parts of the spring, may answer better. 
 
 171. Carbureter Repairs. " Water-logged " Float. Grinding 
 a Needle Valve. A hole in the hollow metal float of a float-feed 
 carbureter may let gasoline enter the float if the hole is below the 
 
240 THE GAS ENGINE 
 
 level of the gasoline. The increased heaviness of the float on 
 this account allows the gasoline to rise higher in the reservoir 
 than it should and thus causes too rich a mixture. To repair it, 
 
 Take the float out of the carbureter and place it in hot water 
 to locate the hole by the bubbles that come from it. Make a 
 small hole in the float, dry it and drive out the gasoline by gentle 
 heating. Solder the leak and test it by blowing into the small 
 hole just made. Let the float cool completely and solder the 
 small hole quickly with a soldering iron so as to heat the float as 
 little as possible. 
 
 If a cork float becomes "water-logged" or heavy, remove it 
 and dry by gentle heating, then varnish it again. 
 
 If the needle valve of the float becomes leaky, press it down 
 on its seat and rotate it, being careful not to bend it. If this does 
 not stop the leak, grind it in with very fine abrasive (as emery) 
 mixed with vaseline or grease. Press lightly on the valve when 
 rotating it to grind, and lift it from its seat frequently to allow the 
 abrasive to get between the valve and its seat. Clean off all of 
 the abrasive carefully when the grinding is finished. 
 
 172. Removing Frost and Ice from the Carbureter. The 
 frost is collected from the air and the ice may come from water 
 which splashes in or is drawn in and freezes. Both obstruct the 
 passage and may hinder the operation of the throttle. 
 
 The ice will generally thaw out if the motor is stopped for a 
 short time. If it does not, lift one of the mixture inlet valves of the 
 motor slightly and crank the motor while the valve is held open; 
 or run the motor by its own power should there be more than one 
 combustion chamber. Holding the inlet valve open will allow 
 the heated gas from the cylinder to be forced back into the inlet 
 passage and the ice will be melted by it. 
 
 Hot water from the cooling system can be poured on to melt 
 the ice. 
 
 173. Pipe Stoppages by Gaskets and Loose Hose Linings. - 
 If a gasket is of soft material, it may be squeezed out into the 
 passage so as to partly or completely stop it. Such materials as 
 leather, rubber composition, and lead (the metal) will .act this way, 
 especially if the leather or rubber becomes soaked and covered 
 
CLEANING AND MISCELLANEOUS 241 
 
 with water and oil. A heavy pressure on a lead gasket will 
 invariably squeeze it out from between the surfaces. The best 
 remedy is not to use such materials where the conditions are of 
 this nature. 
 
 The lining of rubber hose such as is used for the cooling water 
 not infrequently becomes partly detatched from the fabric of the 
 hose. It will sometimes act as a check valve or a flap valve, 
 especially if the loose part is just where the hose fits over a coup- 
 ling into which the water passes from the hose. A loose piece 
 of the hose lining will lodge at such a place and close the passage. 
 
 174. A cracked cylinder or cylinder head is very apt to be the 
 result of overheating on account of failure of the cooling water or 
 cooling oil to circulate. Lack of a full supply of cooling water 
 or cooling oil will produce the same result. Both water-cooled 
 and oil-cooled motors will withstand a great deal of this kind of 
 abuse without cracking, however, when properly made of suitable 
 material. 
 
 A crack in the cylinder or the head may be due to initial 
 stresses in the casting on account of the design or the method of 
 cooling the casting in the mold (or out of it) just after it is poured. 
 
 175. Leaky Piston. Scored Cylinder. A leaky piston is 
 almost invariably due to improperly fitted, worn, grooved, or 
 broken piston rings or a scored (cut, abraded) cylinder bore. 
 Very infrequently it is on account of a cracked piston, the crack 
 generally being in the head end (the end next to the combustion 
 chamber in a single-acting motor). 
 
 The best method of dealing with grooved, cut, or badly worn 
 piston rings is to replace them with new ones. An improperly 
 fitted piston ring or one slightly worn so that, in either case, the 
 bearing against the cylinder bore is only part way around, can be 
 improved by peening it on the inner surface by striking lightly 
 with the ball peen of hammer while the outside of the ring rests 
 on a smooth anvil. This will expand the ring and cause it to 
 bear out against the cylinder harder and therefore to fit to it more 
 closely, if the peening is done properly. Most of the peening 
 should be done opposite the places on the periphery that have 
 been worn bright by rubbing against the cylinder. The peening 
 
242 THE GAS ENGINE 
 
 must be done with great care, since the rings are made of cast 
 iron (except in possible unusual cases). 
 
 If the rings are loose sidewise in the grooves of the piston, it is 
 advisable to get new ones. If a new one is very slightly too wide 
 for the groove, it can be ground down on the sides by rubbing it 
 on a piece of emery (or other abrasive) cloth or paper lying on 
 a truly flat surface. 
 
 A piston ring that is loose sidewise sometimes makes a sharp 
 click when the motor is running. This is more apt to occur if the 
 cylinder is not well lubricated. 
 
 Before placing the rings on a piston, it should be noticed 
 whether the pin or other device for preventing each ring from 
 turning around in its groove is in place. The rings should be 
 held by the pins or stops so that the cuts across them do not come 
 near each other. 
 
 A piston ring can be removed by lifting one of the ends at the 
 cross cut with a piece of soft metal, such as the flattened end of 
 a copper wire, and then twisting the ring around while pressing 
 it sidewise, still keeping the wire under it, or allowing the ring to 
 ride on top of the pin or stop for preventing its rotation when in 
 place. The ring can be kept from snapping back into the groove 
 while removing it, by placing small pieces of wood, leather, wood 
 fiber, etc., under its end in the groove after lifting the end and 
 while twisting the ring around. The ring should not be sprung 
 open any farther than is necessary to remove it. Rings of cast 
 iron are easily broken on account of the brittleness of the metal. 
 
 Putting a piston ring in place is far less difficult than removing 
 it, but the same care must be observed not to open and break it. 
 To prevent its snapping into a groove that is to.be passed over, 
 it can be kept very slightly crooked on the piston. 
 
 The piston, if of the trunk type, can be tested for a crack by 
 removing it from the cylinder, placing it with the open end up, and 
 then pouring gasoline or naphtha inside. The liquid will almost 
 instantly appear on the outside if there is even a very minute crack. 
 Immersing it in gasoline will also show the crack or pore. 
 
 The only way of repairing a badly cut or grooved cylinder is 
 to rebore it. If the wall is thick enough to allow it, the bore may 
 
CLEANING AND MISCELLANEOUS 243 
 
 be made large enough to put in a lining bored to correspond with 
 the diameter of the piston. Otherwise a new piston will be 
 required. 
 
 176. Care and Handling of Combustible Liquids. Removing 
 Water. Gasoline and naphtha vaporize rapidly when exposed 
 to the air. The vapor is heavier than air, and therefore settles 
 to the floor of a room, the bottom of a boat, etc. The mixture 
 at the floor soon becomes rich enough to ignite readily. 
 
 Vents to remove the vapor must be at the bottom of the enclosed 
 space. Openings under doors and through the wall to the 
 atmosphere will generally allow the vapor to escape, but in very 
 quiet, damp or humid weather the circulation of air (and vapor) 
 is apt to be so slight as to leave them practically stagnant. The 
 same is true of venting through flues that lead up from openings 
 at the floor. Forced ventilation with a blower or a hot steam 
 coil in the flue is effective and reliable. 
 
 The safest storage of inflammable liquids is in an underground 
 tank, and the safest way to remove them from the tank is with a 
 suction pump so constructed that any leakage of the valves and 
 other parts will allow the liquid to drain back into the tank. 
 
 Gasoline and other volatile combustible liquids evaporate rap- 
 idly from a closed wooden barrel. This is especially true if the 
 barrel is exposed to the sun. Covering the barrel with a heavy, 
 damp cloth or blanket prevents the evaporation to some extent. 
 
 Gasoline, etc., should not be allowed to drain into sewers. It 
 is liable to be the cause of -explosions in them which will blow 
 manhole covers high in the air and possibly wreck the sewers. 
 
 Water can be removed from gasoline and other volatile products 
 of petroleum either by filtering (straining) or allowing the water 
 to settle to the bottom. A water trap, which may be something 
 like those used in plumbing, but larger and well out of the current 
 of the liquid, will remove the water if the flow past the trap is 
 slow. Chamois skin strains out water and dirt most effectively, 
 but the process is apt to be slow. Felt, linen and cloth do well, 
 but the material should be such as will not give off lint appreciably. 
 The lint will clog the small passages of the carbureter and 
 atomizer. 
 
244 THE GAS ENGINE 
 
 There should be as few sources of accidental ignition of in- 
 flammable vapor in a place where volatile combustibles are 
 present as possible. Some of the things that will cause ignition 
 are: a spark from a nail in one's shoe rubbing over or striking 
 against a cement or stone floor; a spark from metal tools striking 
 together or on a cement floor; an electric spark at a lamp switch 
 or at the brushes of a generator or motor; electric sparks from a 
 running belt; a lighted match, lamp, or candle; a leak in the 
 exhaust connections of an internal -combustion motor. 
 
 The gasoline tank, or a joint in its connections, should never be 
 located so that leakage or drip can fall on or otherwise reach the 
 exhaust pipe, muffler, or other highly heated parts. 
 
 In a launch or boat it is advisable to give the fuel tank sea 
 drainage. This can be done by placing the tank in a water-tight 
 compartment with small openings through the hull to the sea. 
 The tank may be either submerged or above the water level. 
 The connections should have no joints from which leakage can 
 drain into the boat. In no case should joints be hidden from 
 view or inaccessible. It is best to have a solid length of pipe from 
 the tank to the carbureter. Running the fuel pipe line outside of 
 the hull is a safe precaution frequently found in practice. The 
 carbureter should have overboard drainage, or something should 
 be provided to catch any possible drip from it. 
 
CHAPTER XIV. 
 
 INDICATOR CARDS FROM PRACTICE.* 
 
 177. The indicator diagram of an internal -combustion motor 
 with reciprocating piston is obtained in the same general manner 
 as for a similar type of steam engine. The diagram is a record, 
 more or less accurate, of the pressure in the motor cylinder 
 during the operation of the motor through one cycle. 
 
 The form of the diagram and the time required for the 
 tracing point, ray of light, or other recording device to trace it 
 on the card, measured in strokes of the piston, depend on the 
 cycle of the motor. Four strokes of the piston, corresponding to 
 two revolutions of the crank shaft (except in unusual cases), must 
 be made to secure a complete card of a four-cycle motor. A two- 
 cycle motor gives a complete card of the combustion cylinder 
 during two strokes of the piston, corresponding to one revolution 
 of the crank shaft. 
 
 When taking the card, the connections between the indicator 
 and the motor combustion chamber should be as short and direct 
 as possible, and as small in cross-section as will allow the pressure 
 of the combustion chamber to be transmitted to the piston of the 
 indicator without appreciable reduction by frictional resistance 
 to the flow of the gas through the connecting passage. It is 
 more important in the internal-combustion motor that the volume 
 of the space added to the combustion chamber by the indicator 
 and its connections shall be small in comparison to the volume 
 of the motor cylinder than it is for a steam engine. 
 
 The increase of the volume of the compression space of a motor 
 on account of connecting the indicator to it reduces the pressure 
 of compression and consequently that of combustion or explosion, 
 
 * For method of obtaining mean effective pressure from an indicator card 
 see chapter on Pressure -Volume diagrams. 
 
 245 
 
246 
 
 THE GAS ENGINE 
 
 as well as the efficiency of the transformation of the heat energy 
 of the gas into mechanical power. 
 
 An indicator card from a four-cycle motor operating on gas 
 from a suction producer is accurately reproduced in Fig. 77. 
 
 FIG. 77, 
 
 Stop Line 
 
 FIG. 78. 
 
 The atmospheric pressure line is only partly shown in order to 
 leave the diagram as clear as possible. The arrows indicate the 
 direction of motion of the tracing point over the card when making 
 the lines of the diagram. 
 
 The suction stroke begins at A and ends at B. Compression 
 begins at B and continues to the neighborhood of C, wliere ignition 
 occurs, and the pressure rises rapidly to D, while the motor piston 
 
INDICATOR CARDS FROM PRACTICE 247 
 
 makes but little movement. The impulse stroke* begins at some 
 point between C and D. The point of ignition and that where 
 the impulse stroke begins cannot be accurately determined on the 
 card. Combustion is well completed at the reversal of the curve 
 after it begins to drop on the impulse stroke. Expansion of the 
 gases of combustion continues in the tightly closed cylinder till 
 the exhaust valve opens at the point near E, where the expansion 
 line again reverses its curvature. The impulse stroke is com- 
 pleted at the point farthest to the right of and just below E. 
 The exhaust stroke then begins and continues along the upper 
 and nearly horizontal line that crosses the compression line at F 
 and terminates at the starting point A. The junction of the 
 compression line with the combustion curve at about the point C 
 is unusually smooth in this diagram and therefore makes the point 
 C difficult to locate accurately. The ignition occurs slightly 
 before the completion of the compression stroke. 
 
 The pumping action necessary to draw the air into the fuel bed 
 of the gas producer, and the gas there formed, from the producer 
 and through the scrubber and purifier to the motor, causes the 
 suction line of this card to fall farther below the atmospheric 
 pressure line than for a properly designed and installed motor 
 using gas from pressure mains, volatile fuel through a carbureter, 
 or oil injected into the combustion chamber or into a vaporizer. 
 
 The area of the upper loop CDEFC of the indicator card 
 represents the energy that acts to drive the piston of the rnotor. 
 It may be called the positive area. The area of the lower loop 
 ABFA represents energy that acts to retard the motion of the 
 piston, and may be called the negative area. The difference of 
 the two areas (positive negative) therefore represents the 
 energy that is delivered to the piston during a complete cycle of 
 the motor, dealing with one combustion chamber only, and may 
 be called the net area or effective area of the indicator card. To 
 put this in a more convenient form it may be written 
 
 Area CDEFC = positive or impulse energy; 
 
 Area ABFA negative, retarding, or pumping energy; 
 
 Area (CDEFC - ABFA) = net driving or effective energy. 
 
248 THE GAS ENGINE 
 
 The net area of the card can be found with a planimeter by 
 starting at any point on the line and tracing continuously over 
 the boundaries of both loops in the direction of the arrows back 
 to the starting point. The planimeter will record positively for 
 the upper loop and negatively for the lower loop. The net 
 record will be the difference of the areas of the two loops. 
 
 The upper loop CDEFC is often referred to as the impulse 
 diagram, impulse card, or simply the indicator card of the motor. 
 The latter usage has probably arisen from the fact that the area 
 of the lower loop is generally so small in cards from motors that 
 do not draw their fuel through a suction producer, that it is 
 impossible to measure its area with any degree of accuracy even 
 when drawn with a sharp metallic tracing point, when the com- 
 plete double loop is traced continuously, as in Fig. 77. 
 
 When the lines enclosing the area of the lower loop lie so close 
 together as to make it impossible to determine its area with an 
 error less than 50 per cent of its own area, its omission altogether 
 from the complete card will not generally introduce an error as 
 great in actual area as that of determining the area of the upper 
 loop. 
 
 But since the area of the lower loop represents negative work 
 done by the motor, it is desirable to reduce the value of this area 
 to as small an amount as possible that is consistent with other 
 factors to be considered. 
 
 In order to obtain a separate indicator card that will clearly 
 show the characteristics of the lower loop, a weak spring is used 
 in the indicator (in connection with a stop that will prevent the 
 indicator piston and tracing point from being thrown too high 
 if the instrument is not so constructed as to limit the motion of 
 its piston and tracing point within a safe range without a stop). 
 The card thus obtained shows the lower part of the diagram, as 
 of that in Fig. 77, on an enlarged vertical scale, the upper 
 part of the complete diagram being cut off by a line traced parallel 
 to the atmospheric line by the tracing point of the indicator, while 
 its moving parts are held at the limit of their motion caused by 
 the pressure of the gases in the cylinder. 
 
 Such an indicator card is shown in Fig. 78, which is a 
 
INDICATOR CARDS FROM PRACTICE 249 
 
 vertical enlargement of the lower part of Fig. 77. It may 
 be referred to as a low-spring card, pumping card, or pump 
 card. 
 
 Many of the causes that effect changes in the form and area 
 of the impulse card are different from those that produce similar 
 variations in the pumping card. For this reason, as well as on 
 account of the contracted form of the pumping card when taken 
 in connection with the impulse card, it is customary to take a 
 separate low-spring indicator card of the form just described to 
 show the pumping action. A card of this kind is also very 
 useful for examining the valve action. 
 
 The mean effective pressure of either card can be found in the 
 usual manner, by dividing its area (square inches) by its length 
 (inches) and then multiplying by the value of the indicator spring 
 (pounds per inch of height of the indicator card). 
 
 The remainder obtained by subtracting the mean effective 
 pressure of the pumping card from that of the impulse card, 
 both reduced to the same scale, represents the net mean pres- 
 sure that is effective in driving the motor piston when the com- 
 plete cycle is taken into consideration. 
 
 The indicated horsepower of a single-cylinder, single-acting 
 motor or of one combustion chamber of a multi-cylinder or 
 double-acting motor is obtained by multiplying together the net 
 mean effective pressure, the cross-sectional area of the clear 
 space in the cylinder, the length of stroke and the number of 
 explosions or impulses per minute, and dividing the product by 
 33,000. 
 
 The cross-sectional area of the clear space in the cylinder is 
 customarily referred to as the piston area. When there is no 
 piston rod extending through the combustion space this area is 
 that of a circle of the same diameter as the bore of the cylinder; 
 but when there is a piston rod in the space its cross-sectional 
 area must be deducted from that of the circle. The form of the 
 piston head (convex, concave, flat irregular) does not have to be 
 considered. 
 
 In a throttle-controlled four-cycle motor of the common type, 
 there is an explosive impulse every four strokes of the piston 
 
2$0 THE GAS ENGINE 
 
 (two revolutions of the crank) in each combustion chamber 
 provided there are no misfires. In a two-cycle motor there is an 
 impulse every two strokes of the piston (every revolution of the 
 crank) under similar conditions. 
 
 In a hit-or-miss controlled motor the number of explosions per 
 minute is variable and must therefore be recorded to obtain the 
 indicated horsepower. 
 
 The following notation will be used to write the mathe- 
 matical expressions for the indicated horsepower of an indicator 
 diagram : 
 
 A = piston area, effective, square inches; 
 
 G = strokes of piston per cycle; 
 
 L = length of stroke of piston, feet; 
 
 R = revolutions of crank per minute; 
 
 T = piston travel, feet per minute; 
 
 Y = number of explosions or impulses per minute; 
 
 I.h.p.I = impulsive indicated horsepower per combustion 
 
 chamber; 
 I.h.p.R = retarding indicated horsepower per combustion 
 
 chamber; 
 
 I.h.p.N = net indicated horsepower per combustion chamber; 
 M.e.p.I = mean effective impulsive pressure of impulse card 
 
 (CDEFC,Fig. 77); 
 M.e.p.R = mean effective retarding pressure of pumping card 
 
 (ABFA,Fig. 77); 
 M.e.p.N = M.e.p.I M.e.p.R = net mean effective pressure. 
 
 For the general case, including hit-or-miss governing, 
 
 33,000 
 or 
 
 Lh . p . N . ... 
 
 33,000 G 
 
W THB 
 
 UNIVERSITY 
 
 OF 
 
 INDICATOR CARDS FROM PRACTICE 251 
 
 For a four-cycle motor without misfires or cgmplete cut-outs 
 of charges (reduction of charge governing), 
 
 (M.e.p.N) ALR 
 I.h.p.N = - > 
 
 2 X 33,000 
 
 Lh.p.N 
 
 4 X 33,000 
 
 For a two-cycle motor without misfires or complete cut-outs of 
 charges, 
 
 (M.e.p.N) ALR 
 
 Lh.p.N = 
 I.h.p.N - 
 
 33,000 
 or 
 
 (M.e.p.N) AT 
 2 X 33,000 
 
 Equations similar to the above can be written for the mean 
 effective pressure of the impulse loop and for the pumping loop 
 of the diagram, the only change being the substitution of the 
 proper mean effective pressure and indicated horsepower. 
 
 In a two-Cycle motor the pumping loop does not appear on the 
 diagram. If the usual type of indicator, in which the pressure 
 of the gas acts on only one side of the piston, is used, it records 
 only the impulse diagram. A separate card for. the crank case 
 of the simpler type of two-cycle motor must be taken for the 
 pumping diagram. In the more complicated forms of two-cycle 
 motors with precompression pumps, the pumping diagrams are 
 to be taken from the pumps themselves. 
 
 178. Indicator Cards Representing American Practice. A 
 number of indicator cards from American gas, gasoline, and oil 
 motors are reproduced with as much accuracy as possible in this 
 section. In some of them the bottom loop is omitted on account 
 of its being so narrow that it cannot be read or reproduced with 
 a warrantable degree of accuracy. Its value is of course of little 
 weight in determining the indicated power when the loop is so 
 small. 
 
252 
 
 THE GAS ENGINE 
 
 The point of ignition is much more clearly denned in Fig. 79 
 than in Fig. 77. The compression pressure is determined by 
 continuing the compression line as if there had been no ignition 
 
 FIG. 79. 
 
 FOUR-CYCLE MOTOR. HIT-OR-MISS GOVERNED. FULL LOAD. 
 Pressures in pounds per square inch above atmosphere. 
 
 Illuminating gas. 
 
 Compression pressure 60 
 
 Explosion pressure 220 
 
 M.e.p. impulse 84 
 
 210 
 180 
 
 150 
 120 
 90 
 
 Diameter of piston 13 . 5* 
 
 Stroke 24* 
 
 Revolutions per minute 170 
 
 Piston travel, feet per minute . . . 680 
 
 FIG. 80. 
 
 FOUR-CYCLE MOTOR. THROTTLE GOVERNED. PART LOAD. 
 Pressures in pounds per square inch above atmosphere. 
 
 Natural gas. Diameter of piston 15* 
 
 Compression pressure 63 Stroke 24* 
 
 Explosion pressure 200 Revolutions per minute 170 
 
 M.e.p.1 58 Piston travel, feet per minute. . . . 680 
 
 till it intersects the line perpendicular to the atmospheric line and 
 tangent to the combustion line at the right-hand end of the 
 diagram. The bottom loop on the original card appears almost 
 as a line, and is not reproduced. 
 
INDICATOR CARDS FROM PRACTICE 253 
 
 Fig. 8 1 shows the effect of the vibration of the indicator 
 point at the beginning of the impulse stroke, recorded as a wavy 
 line. The area of the card was determined by drawing a smooth 
 curve to represent, as nearly as could be judged, the true pressures 
 that would have been recorded if the indicator had not vibrated. 
 
 100 
 
 FIG. 81. 
 FOUR-CYCLE MOTOR. HIT-OR-MISS GOVERNED. FULL LOAD. 
 
 Pressures in pounds per square inch above atmosphere. 
 
 Illuminating gas . Diameter of piston i r . 25* 
 
 Compression pressure 72 Stroke 19" 
 
 Explosion pressure ' 334 Revolutions per minute 220 
 
 M.e.p.1 96. 5 Piston travel, feet per minute. . . 697 
 
 In this motor the ignition is electric in a small chamber con- 
 nected to the combustion chamber by a straight narrow passage 
 so that a flame spurts out into the main body of the charge to 
 ignite it. 
 
 In Fig. 82 the sharp peak at the top of the diagram with 
 rapidly rising combustion line at the peak seems to indicate that 
 a sharp local explosion occurred in the connections to the indicator 
 after the combustion of the main body of the charge was well 
 under way. 
 
 The bottom loop of this card shows that the exhaust pressure 
 dropped to about atmospheric when the piston was about one- 
 quarter of the way back on the exhaust stroke and then rose 
 higher later in the stroke. This might be caused by a very quick 
 and full opening of the exhaust valve together with a straight 
 exhaust pipe of such proportions that the inertia of the escaping 
 
254 
 
 THE GAS ENGINE 
 
 gas tended to form a partial vacuum soon after their release, 
 which tendency did not continue till the middle of the stroke was 
 reached. 
 
 1 420 
 
 240 
 ISO 
 120 
 
 FIG. 82. 
 
 FOUR-CYCLE MOTOR. HIT-OR-MISS GOVERNED. FULL LOAD. 
 Pressures in pounds per square inch above atmosphere. 
 
 Natural gas. Diameter of piston 15 1* 
 
 Compression pressure 100 Stroke 18* 
 
 Explosion pressure 375 Revolutions per minute 175 
 
 M.e.p.1 104 Piston travel, feet per minute .... 525 
 
 FIG. 83. 
 
 FOUR-CYCLE MOTOR. THROTTLE GOVERNED. FULL LOAD. 
 Pressures in pounds per square inch above atmosphere. 
 
 Gas. Diameter of piston 19* 
 
 Compression pressure 92 Stroke 24" 
 
 Explosion pressure 270 Revolutions per minute 225 
 
 M.e.p.1 71.2 Piston travel, feet per minute 900 
 
 See Fig. 84 for card from same motor throttled to about seven per cent of the full 
 
 load at the brake. 
 
 The lower loop of Fig. 83 has a larger area on account of 
 the comparatively high piston speed than it would "have at the 
 lower piston speeds of the preceding cards. 
 
INDICATOR CARDS FROM PRACTICE 255 
 
 Fig. 84 shows two consecutive diagrams dntwn by keeping 
 the tracing point on the card during two cycles of the motor. 
 
 Both combustion lines slope away from the perpendicular to 
 the atmospheric line. This is due to the slower rate of inflamma- 
 tion and combustion on account of both the lower degree of com- 
 pression and the greater dilution of the mixture than in Fig. 83. 
 The time of ignition is the same for all three of the diagrams 
 
 FIG. 84. 
 
 FOUR-CYCLE MOTOR. THROTTLE GOVERNED. THROTTLED 
 TO ABOUT SEVEN PER CENT OF THE FULL CAPACITY BRAKE 
 LOAD AS DELIVERED BY THE MOTOR. 
 
 Pressures in pounds per square inch above atmosphere. 
 
 Gas. Diameter of piston ig" 
 
 Compression pressure 32 Stroke 24" 
 
 _ . . (58 Revolutions per minute 232 
 
 Explosion pressure < ~. _. 
 
 ( 64 Piston travel, feet per minute .... 928 
 
 M.e.p.L, average 14.6 
 
 See Fig. 83 for full-load card from same motor. 
 
 shown in the two cards. It occurs a little before the completion 
 of the compression stroke in each case. The slower rate of com- 
 bustion and the lower explosion pressure in the smaller of the two 
 diagrams in Fig. 84 is probably due to less fuel in the charge 
 for the smaller card, for the compression pressure is the same in 
 both, as near as can be determined from a comparatively clear 
 original card. 
 
 The slope of the combustion line away from the perpendicular 
 to the atmospheric line would be greater if the indicator spring 
 were of the same strength as that used for Fig. 83 instead of 
 being 80 pounds per inch of compression while that of Fig. 83 is 
 200 pounds per inch of compression. 
 
2 5 6 
 
 THE GAS ENGINE 
 
 The expansionline of the light-load card drops to within a pound 
 or two of atmospheric pressure. In the full-load card its lowest 
 point is about twenty pounds above atmosphere. 
 
 The suction line of the light-load card falls to about six pounds 
 below atmosphere soon after the beginning of the charging stroke, 
 and continues to fall gradually to about eight pounds below atmos- 
 phere at the completion of the charging stroke. The area of 
 the lower loop is not great, however, since the compression line 
 follows it closely back about half way. 
 
 The suction line in Fig. 84 rises above the exhaust line during 
 the early part of the charging stroke. This is probably due to a 
 momentary increase of back pressure in the exhaust pipe, caused 
 by the exhaust from another combustion chamber of the motor at 
 about the time of the completion of the exhaust stroke of this card 
 and while the corresponding exhaust valve was closed. It may 
 be due to slight lost motion in the indicator, but this is hardly 
 probable, since the cards come from one of the leading gas-engine 
 builders. 
 
 FIG. 
 
 FOUR-CYCLE MOTOR. THROTTLE GOVERNED. FULL LOAD. 
 Pressures in pounds per square inch above atmosphere. 
 
 Gas . Diameter of piston 8" 
 
 Compress on pressure 80 Stroke lo* 
 
 Explosion pressure 380 Revolutions per minute. 320 
 
 M.e.p.1 82 Piston travel, feet per minute 533 
 
 See Fig. 86 for light- load card from same motor. 
 
INDICATOR CARDS FROM PRACTICE 257 
 
 The extreme sharpness and height of the peak in Fig. 85 are 
 probably due to the inertia of the moving parts of the indicator 
 causing it to record higher than the actual maximum pressure 
 of the explosion. The sharp waves of the expansion line are 
 records of rapid vibration of the indicator tracing point on account 
 of the inertia of the parts. 
 
 FIG. 86. 
 
 FOUR-CYCLE MOTOR. THROTTLE GOVERNED. THROTTLED 
 TO RUN ON ITS OWN FRICTION LOAD ONLY. 
 
 Pressures in pounds per square inch above atmosphere. 
 
 Gas. Diameter of piston 8" 
 
 Compression pressure 22 Stroke 10" 
 
 Explosion pressure 37 Revolutions per minute 331 
 
 M.e.p.1 12.4 Piston travel, feet per minute .... 550 
 
 See Fig. 85 for full-load card from same motor. 
 
 Fig. 86 represents an extreme case of the retarding effects of low 
 compression and great dilution on the rate of flame propagation 
 and combustion. The card was taken from the same motor as 
 that of Fig. 85. The time of ignition was the same in both cases 
 slightly before the completion of the compression stroke. 
 
 The linear rate of flame propagation is so slow in Fig. 86 that 
 the pressure of combustion is scarcely kept up to that of compres- 
 sion during the early part of the impulse stroke. But the rapidly 
 increasing volume rate of propagation then causes the pressure to 
 rise notwithstanding the increase in the rate of the travel of the 
 piston and in the rate of increase of volume of the enclosed gases.* 
 
 * The propagating flame moves out from the point of ignition with the same 
 constant linear velocity in all directions (theoretically in a quiescent body of 
 gas). The crest of the propagating flame therefore forms a spherical surface 
 whose area increases as the square of the diameter or of the time elapsed after 
 the initial ignition. The rate of inflammation, measured in the volume inflamed 
 per unit time, therefore, increases as the square of the time. And the total 
 
258 THE GAS ENGINE 
 
 The short horizontal portion of the combustion line may be in 
 part due to friction in the indicator after coming to rest at the 
 completion of compression. In such a case it would at first move 
 more rapidly immediately after starting from rest than the in- 
 creasing pressure of the gases alone would cause. Such an action 
 will produce a sharp bend in the curve such as that between the 
 short horizontal line and the upward inclined line. 
 
 If the load on the motor is increased by successive steps from 
 only the friction load, Fig. 86, to full load, Fig. 85, the inclination 
 of the combustion line from the vertical on cards taken for each 
 step of increase of load, will decrease as the load increases, finally 
 reaching the direction of that in Fig. 85 for full load. 
 
 The same is true of Figs. 83 and 84. 
 
 The maximum pressures in Figs. 83 and 84 for full load and 
 light load occur at about the same time in the stroke. But in 
 Fig. 86 the maximum pressure is much later than for the full- 
 load card, Fig. 85, from the same motor. 
 
 Two diagrams taken consecutively from a hit-or-miss governed 
 motor with friction load only are shown in Fig. 87. One 
 diagram was made after a charge was cut out by the governor 
 action, and the other for the following impulse stroke. The 
 compression lines of the two diagrams are coincident except for 
 a short distance just before the completion of compression. They 
 then separate slightly and the distance between them continues 
 to increase till the end of the compression stroke. 
 
 The impulse line of the full-charge diagram lies above the 
 compression line in the usual manner. The expansion line of 
 the cut-out diagram drops slightly below the compression line 
 during the stroke following compression (normally the impulse 
 stroke). The drop of this expansion line at and near the end 
 of the compression stroke is probably chiefly due to leakage. The 
 " exhaust" line following expansion of the cut-out charge cannot 
 
 volume of the gas inflamed increases as the volume of the sphere, or as the 
 cube of the time, the linear rate of propagation remaining constant. Some 
 approximation of this condition probably occurs in a motor when the ignition 
 is at a point in the main body of the charge, as distinguished from ignition in 
 a pocket leading off from the mass of the gas. 
 
INDICATOR CARDS FROM PRACTICE 
 
 259 
 
 FIG. 87. 
 
 FOUR-CYCLE MOTOR. HIT-OR-MISS GOVERNED. FRICTION 
 
 LOAD. 
 
 Pressures in pounds per square inch above atmosphere. 
 
 Natural gas Diameter of piston 13* 
 
 Compression pressure 70 Stroke 22" 
 
 Explosion pressure 310 Revolutions per minute 170 
 
 M.e.p.1 90 Piston travel, feet per minute .... 623 
 
 FIG. 88. 
 
 FIG. 89. 
 
260 
 
 THE GAS ENGINE 
 
 be distinguished from the suction line, but probably lies very 
 slightly above it. 
 
 Fig. 88 shows a series of indicator cards from a gas motor 
 governed by a cut-off valve that allows the mixture to begin to 
 enter at the beginning of the suction stroke and cuts it off during 
 the suction stroke when a volume proportional approximately 
 to the work being done by the motor has entered the cylinder. 
 
 Fig. 89 shows the corresponding diagrams taken with a low 
 spring and stop on the indicator. 
 
 FIG. 90. 
 
 FIG. 91. 
 
 Figs. 90 and 91 are cards from the " complete expansion 
 engine." They show respectively the upper loops of a pair of 
 diagrams and the corresponding low-spring cards. The motor 
 is four cycle and governed by admitting only air during the 
 first part of the suction stroke, and then beginning the admission 
 
INDICATOR CARDS FROM PRACTICE 
 
 26i 
 
 of gas at a time determined by the governor. ' The gas and 
 air are both cut off at the same instant at about half stroke. 
 
 FIG. 92. 
 
 Fig. 92 is a series of diagrams from the same kind of a 
 motor as that from which Figs. 90 and 91 were obtained. It 
 shows the governing action during fifty consecutive cycles. 
 
 192 
 160 
 
 FIG. 93. 
 
 FOUR-CYCLE MOTOR. HIT-OR-MISS GOVERNED. FULL LOAD. 
 Pressures in pounds per square inch above atmosphere. 
 
 Gasoline . Diameter of piston r 2 " 
 
 Compression pressure 50 Stroke 2 o" 
 
 Explosion pressure 245 Revolutions per minute 2 oo 
 
 M.e.p.1 82 Piston travel, feet per minute. . . . 667 
 
 Three consecutive diagrams from a hit-or-miss governed motor 
 are shown in Fig. 93. The ignition was at the same time in 
 each. The rate of combustion (or of flame propagation) is dif- 
 ferent in each, however, as shown by the different inclinations of 
 the combustion lines. The areas and mean effective pressures 
 are practically the same in all three. This indicates that the 
 
262 
 
 THE GAS ENGINE 
 
 same weight of fuel was burned and the same amount of heat 
 energy produced by the combustion of each charge. All the 
 charges were drawn in under the same condition of inlet passages, 
 carbureter, and other parts, by virtue of the method of governing. 
 The coincidence of the compression lines also shows that the 
 charges were of the same weight. 
 
 The difference in the rate of inflammation, or of combustion, 
 or of both, was probably due to a difference in the thoroughness 
 of the mixture of the fuel and the air, or of its richness at and in 
 the neighborhood of the ignition apparatus. 
 
 200 
 
 160 
 
 120 
 
 80 
 
 40 
 
 FIG. 94. 
 
 FOUR-CYCLE MOTOR. HIT-OR-MISS GOVERNED. LIGHT LOAD. 
 
 Pressures in pounds per square inch above atmosphere. 
 
 Gasoline. Diameter of piston 12* 
 
 Stroke 20* 
 
 Revolutions per minute 200 
 
 Piston travel, feet per minute .... 667 
 
 Compression pressure 
 
 Explosion pressure 
 
 M.e.p.I 
 
 60 
 
 270 
 330 
 
 94 
 
 Fig. 94 shows three diagrams from the same motor as that 
 from which the preceding set of cards, Fig. 93, was taken, but 
 the motor was running on light load in the last card. The large 
 diagram is for the first explosion after several misfires. This 
 was followed immediately by the smaller implilse diagram. 
 The cut-out diagram is a composite of several diagrams. 
 
INDICATOR CARDS FROM PRACTICE 
 
 263 
 
 The greater size of the larger diagram is due either to a greater 
 weight of fuel or a better proportion of the mixture. A greater 
 weight of mixture is generally drawn into the cylinder after 
 several cut-outs on account of the cylinder becoming cooler. An 
 inlet valve that lets combustible mixture leak into the cylinder 
 during the suction stroke when the charge is cut out (as on 
 account of too weak a valve spring) will allow scavenging of 
 the cylinder during several consecutive cut-out strokes, so that the 
 following charge is but slightly diluted by the inert products of 
 combustion. The resulting diagram is then larger than those 
 following. 
 
 The cut-out diagram in this card shows but little, if any, leakage. 
 The expansion line of the cut-out diagram will fall below the 
 compression line when the cylinder is cool, even if there is no 
 leakage from the cylinder, for some of the heat of compression 
 is given up to the cylinder during the time the gas is well com- 
 pressed. The same may also be true with a hot cylinder when 
 the incoming charge strikes the hottest parts, as the exhaust 
 valve and ports, and the piston head when not water cooled. In 
 such a case the charge becomes so highly heated while entering 
 that its compression temperature is higher than that of the cylinder 
 walls taken as an average. 
 
 210 
 180 
 150 
 120 
 90 
 
 FIG. 95. 
 FOUR-CYCLE MOTOR. THROTTLE GOVERNED. FULL LOAD. 
 
 Pressures in pounds per square inch above atmosphere. 
 
 Gasoline. Diameter of piston 10.5* 
 
 Compression pressure 60 Stroke 14" 
 
 Explosion pressure 210 Revolutions per minute 250 
 
 M.e.p.1 76 Piston travel, feet per minute 583 
 
264 THE GAS ENGINE 
 
 Fig. 95 shows a card with two diagrams from a gasoline 
 motor of the throttle-governed type. There is considerable 
 difference in the combustion lines, although the compression lines 
 coincide so far as can be seen on the original, clearly drawn, fine 
 line card. The higher combustion line has a decided reverse 
 curve, which seems to indicate, as in Fig. 82, that there was a 
 sharp explosion in the connections between the indicator and the 
 combustion chamber after the main body of the gas was well 
 inflamed. The expansion line of the higher card with the peaked 
 top falls below that of the other, so that the areas of the two cards 
 are practically equal. 
 
 FIG. 96. 
 
 FOUR-CYCLE MOTOR. HIT-OR-MISS GOVERNED. FULL LOAD. 
 
 Pressures in pounds per square inch above atmosphere. 
 
 Gasoline. Diameter of piston 6. 75* 
 
 Compression pressure 62 Stroke 15. 5* 
 
 Explosion pressure 360 Revolutions per minute 260 
 
 M.e.p.1 102 Piston travel, feet per minute. . . 672 
 
 Motor took 126 charges per minute. 
 
 In Fig. 96 the sharp angle between the compression line 
 and the combustion line indicates ignition at the completion of 
 the compression stroke. It compares in this case with Fig. 81 
 from a motor of the same make operating on illuminating gas. 
 
 In both motors, Figs. 81 and 96, the ignition plug is 
 placed in a small chamber connected to the combustion chamber 
 by a small passage. The spark ignites the gas in the small 
 
INDICATOR CARDS FROM PRACTICE 265 
 
 chamber and the expansion of the gas while burning projects a 
 flame into the body of the charge in the combustion chamber, 
 thus inflaming a considerable amount of the charge suddenly. 
 The gas currents caused by the projection of the gas and flame 
 from the ignition pocket into the combustion chamber also help 
 the rapidity of inflammation. This method of ignition accounts 
 for the absence of the rapid falling away of the combustion line 
 from the vertical, which occurs when ignition is at the completion 
 of the compression stroke by a spark or arc in the main body of 
 the gas in the combustion chamber. 
 
 200 
 
 100 
 120 
 
 40 
 
 
 FIG. 97. 
 
 FOUR-CYCLE MOTOR. GOVERNED BY REGULATING THE 
 AMOUNT OF FUEL PER CHARGE. FULL LOAD. 
 
 Pressures in pounds per square inch above atmosphere. 
 
 Kerosene. Diameter of piston 6.5* 
 
 Compression pressure 40 Stroke g" 
 
 ( 1150 Revolutions per minute 405 
 
 Explosion pressure < ^. . , 
 
 ( 170 Piston travel, feet per minute 607 
 
 M.e.p.1 63 
 
 In Fig. 97 ignition occurs rather late, at dead center or very 
 slightly before it, as indicated by the nearly horizontal direction 
 of the first part of the combustion line. The difference of the 
 areas of the two cards is due to the varying quantity of combustible 
 mixture. 
 
 In Fig. 98 the three diagrams are from a Hornsby-Akroyd 
 motor operating at full load. The difference in the areas of the 
 diagrams is due to the governor action in regulating the amount 
 of liquid fuel that is injected into the vaporizer extension of the 
 motor cylinder during each cycle. The compression is of course 
 
266 
 
 THE GAS ENGINE 
 
 always practically the same, since air is always freely admitted 
 during the suction stroke. Ignition occurs some time before the 
 completion of the compression stroke, and is caused by the high 
 temperature of the walls of the vaporizer. 
 
 200 
 
 180 
 
 160 
 
 140 
 
 120 
 
 100 
 
 80 
 
 60 
 
 40 
 
 20 
 
 
 
 FIG. 98. 
 
 HORNSBY-AKROYD FOUR-CYCLE MOTOR. GOVERNED BY REGU- 
 LATING THE AMOUNT OF FUEL PER CHARGE. FULL LOAD. 
 
 Pressures in pounds per square inch above atmosphere. 
 
 Distillate of petroleum. 
 
 Compression pressure 
 
 Explosion pressure, average.. 
 M.e.p.I. average 
 
 Diameter of piston 23* 
 
 58 Stroke 28* 
 
 180 Revolutions per minute 160 
 
 54 Piston travel, feet per minute 747 
 
 With regard to Fig. 99 it will be remembered that the full 
 charge of air is taken in and compressed to a high pressure before 
 the liquid fuel is injected (blown) into the combustion chamber, 
 and that ignition is caused by the heat of compression. The 
 work of compressing the air to blow the fuel into the combustion 
 chamber must be deducted from that of the impulse card to 
 determine the net indicated power. 
 
 Fig. 100 is a low-spring or pumping card corresponding to 
 Fig. 99. 
 
 Fig. 101 is a card from a Koerting two-cycle motor, which 
 has auxiliary cylinders for separately compressing the air and gas. 
 
FIG. 99. 
 
 DIESEL TWO-CYCLE MOTOR. GOVERNED BY REGULATING THE 
 AMOUNT OF FUEL PER CHARGE. FULL LOAD. 
 
 Pressures in pounds per square inch above atmosphere. 
 
 Petroleum distillate, specific gravity. .85 
 
 Compression pressure 480 
 
 Combustion pressure 490 
 
 M.e.p.1 97 
 
 Diameter of piston 16" 
 
 Stroke. 24" 
 
 Revolutions per minute 160 
 
 Piston travel, feet per minute 640 
 
 Suction 
 
 FIG. 100. 
 
 204 
 170 
 
 102 
 
 34 
 
 FIG. 101. 
 
 KOERTING TWO-CYCLE MOTOR. GOVERNED BY REGULATING 
 THE AMOUNT OF FUEL PER CYCLE. FULL LOAD. 
 
 Pressures in pounds per square inch above atmosphere. 
 Producer gas. Diameter of piston 2 5 5* 
 
 Compression pressure 120 
 
 Explosion pressure 225 
 
 M.e.p.I 53 
 
 Stroke 45 
 
 Revolutions per minute 100 
 
 Piston travel, feet per minute 750 
 
268 THE GAS ENGINE 
 
 The governing is by admitting the gas during the latter part of 
 the charging stroke for such a length of time as the governor 
 determines. 
 
 The exhaust comes earlier than in a properly adjusted four- 
 cycle motor on account of the necessity of having the piston 
 uncover the exhaust port early enough to allow the spent gases 
 to escape and the new charge to enter while the port remains 
 uncovered. 
 
 The pumping or charging diagram does not appear on the card, 
 since this part of the work is done in the two auxiliary cylinders. 
 Separate diagrams must be taken from the auxiliary cylinders to 
 obtain the pumping, or charging, diagrams. 
 
 179. Indicator Diagrams Showing Abnormal Pressures. 
 If the pipe connections to the indicator are long, and especially 
 if the passage is contracted at the end next the combustion 
 chamber, the combustion of the gas hi the pipe after the pressure 
 has become high in the combustion chamber on account of the 
 explosion, will generally give diagrams showing abnormally 
 high and suddenly increasing pressures. The inertia of the 
 moving parts of the indicator adds to the recorded apparent 
 pressure. Pockets in the combustion space of the motor will 
 give similar but generally less marked results when the ignition 
 is not in the pocket. 
 
 It has already been pointed out that the indicator connections 
 should be as short as possible, and without contracted passages. 
 
 180. Incorrect Valve Setting as Shown by the Indicator Diagram. 
 Four-Cycle Motors. Figs. 102 to 107 are portions of indicator 
 diagrams showing the characteristic effects of extremely early or 
 late opening or closing of the inlet and exhaust valves. Those 
 for the inlet valve apply only to those that are mechanically 
 operated valves. 
 
 Fig. 1 02 shows the latter part of the expansion line and the 
 early part of the exhaust line. The early opening of the exhaust 
 allows the burned gases to escape before the expansive action and 
 impulse pressure against the piston are completed as far as is 
 practicable and advantageous and can be done without causing 
 too much pressure against the piston during the early part of 
 
INDICATOR CARDS FROM PRACTICE 269 
 
 the exhaust stroke. The result is a reduction of. the area of the 
 impulse loop and of the mean effective pressure of the impulse. 
 
 Exhaust 
 
 FIG. 102. 
 
 This should not be confused with the necessary earlier exhaust 
 of the two-cycle motor, as compared with the four-cycle type. 
 
 Fig. 103 indicates too late an opening of the exhaust valve. 
 This causes considerable pressure resisting the motion of the 
 
 Exhaust 
 
 FIG. 103. 
 
 piston during the early part of the exhaust stroke. The area of the 
 impulse loop and the mean effective pressure are both reduced. 
 
 Fig. 104 is characteristic of an exhaust valve closing too early 
 when the inlet valve opens at the end of the stroke. When 
 the inlet valve opens under this condition, the slightly compressed 
 
 V s Exhaust < 
 
 Suction 
 
 FIG. 104. 
 
 exhaust gases puff out into the inlet passage and are then drawn 
 in again as the piston moves out on the suction stroke. This 
 causes fouling of the inlet valve and its stem, and is a condition 
 that should be particularly avoided. 
 
270 THE GAS ENGINE 
 
 In Fig. 105 the exhaust valve closes too early, as in the 
 preceding figure, but the inlet valve opens later than it should 
 for proper setting of the exhaust valve. The conditions of 
 Fig. 105 are better than those of Fig. 104 mainly because there is 
 
 Exhaust 
 
 Suction > 
 
 FIG. 106. 
 
 no puffing out of the exhaust gases through the inlet valve, but 
 also because the area of the pumping card loop is smaller. The 
 latter is generally insignificant in comparison with the former. 
 
 Fig. 106 indicates, by the horizontal portion of the com- 
 pression line, too late closing of the inlet valve. Under this 
 condition part of the charge that has been drawn in and diluted 
 
 by the residual inert gases is forced back through the inlet valve 
 during the early part of the compression stroke. Compression 
 does not begin till the inlet valve closes. The following charge 
 is somewhat weakened, or made lean, by the inert gases that were 
 forced back into the inlet passage, and the power of the motor 
 is thus reduced. 
 
 Fig. 107 shows early closing of the inlet valve. This is 
 accompanied with no undesirable results. The charge is rarefied 
 after the inlet valve closes, and then compressed along the same 
 line again up to suction pressure, after which the compression 
 continues in the usual manner. This is characteristic of the 
 method of governing by reducing the amount of the mixture per 
 
INDICATOR CARDS FROM PRACTICE 271 
 
 charge by opening the mixture inlet valve always at the same 
 time and closing it at such a part of the stroke as the speed and 
 governor determine. 
 
 FIG. 107. 
 
 This method of operation is also characteristic of the " complete 
 expansion " engine. 
 
 181. Momentary Back Pressure. Fig. 108 shows the effect 
 of back pressure in the exhaust pipes at the time of exhaust 
 of another cylinder whose exhaust opens one-half a revolution 
 from that of the cylinder from which the indicator card is taken. 
 
 Exhaust 
 
 Suction > 
 
 FIG. 108. 
 
 The back pressure comes into the cylinder just before the exhaust 
 valve closes, and drops when the inlet valve opens (after the 
 exhaust valve has closed). This is not an indication of incorrect 
 valve setting. (See disposal of exhaust gases.) 
 
 182. Variation of the Time of Ignition as Affecting the Indi- 
 cator Card. Four-Cycle Motor. When all the other conditions 
 remain constant, and the time of ignition is varied, the effects on 
 the indicator diagram are shown characteristically in Figs. 109 
 to in. 
 
2/2 
 
 THE GAS ENGINE 
 
 Fig. 109 indicates ignition that is later than is suitable for 
 the best results in economy of fuel in motors of the usual con- 
 struction. The great inclination of the combustion line is due to 
 
 FIG. 109. 
 
 the rapid increase of volume of the burning gases as the piston 
 travels out, and also to the consequent lower rate of flame propa- 
 gation and combustion on account of the rarefication of the charge 
 by the movement of the piston. 
 
 In Fig. no the ignition is extremely late, not occurring till 
 the piston has moved out some distance on the impulse stroke. 
 The completion of compression and the early part of the impulse 
 
 FIG. 110. 
 
 stroke are therefore the same as for a cut-out stroke of a hit-or- 
 miss governed motor. The combustion line rises very slowly 
 on account of the comparative low pressure of the charge at the 
 time of ignition and the consequent slower rate of flame propa- 
 gation; also on account of the speed of piston travel being 
 greater after the piston has moved out some distance on the im- 
 pulse stroke than it is near the beginning of the stroke. 
 
 Fig. in indicates extremely early ignition. The explosion 
 pressure rises to its maximum before the completion of the com- 
 pression stroke, and then drops before the piston has moved far 
 out on the impulse stroke, thus causing a loop at the top of the 
 
INDICATOR CARDS FROM PRACTICE 
 
 273 
 
 card. The area of this loop indicates retarding action on the 
 motion of the piston. The pressure falls so as to make a low 
 expansion line. 
 
 The area of the impulse card is the difference of the areas of 
 the two upper loops in a complete card. This condition could 
 
 FIG. 111. 
 
 hardly exist for any considerable length of time in a single- 
 cylinder, single-acting motor, on account of the small amount of 
 power that the motor would deliver. But it can occur con- 
 tinuously in one cylinder of a multi-cylinder motor, as on account 
 of a defect in the timer affecting that cylinder only, and the motor 
 will continue to run by the impulses of the other cylinders. 
 
 FIG. 112. 
 
 183. A dilute mixture gives the full-line part diagram of 
 Fig. 112 in comparison with the broken -line part diagram for 
 a normal mixture in the same figure. The greater inclination 
 of the combustion line and the lower maximum pressure for the 
 
274 
 
 THE GAS ENGINE 
 
 dilute mixture are both due to the slower rate of combustion and 
 the smaller amount of total heat liberated by combustion of the 
 charge. 
 
 184. Variation of Compression Effects on the Indicator Dia- 
 gram. Fig. 113 shows two diagrams such as come from a 
 
 FIG. 113. 
 
 motor when its compression is changed while all the other con- 
 ditions remain the same, including the weight and heat value of 
 the charge. 
 
 185. Speed. Variation Effects on the Indicator Diagram. - 
 Changing the speed of the motor while all the other conditions 
 remain constant has an effect on the diagram that is of the same 
 nature as diluting the mixture. It may be remembered that 
 increasing the speed of rotation of a motor causes the ignition to 
 become later for any form of electric ignition apparatus other 
 than the interrupted-current type with contact points separated 
 by the action of rigid mechanism. The writer's experience with 
 a four-cylinder motor having the latter type of ignition system, 
 operating at too high a speed to take indicator cards, has been 
 that the motor gives practically its maximum torque at high 
 and low speeds without changing the time of ignition when the 
 speed varied from 300 to more than 1000 revolutions per minute. 
 The speed of rotation of the electric generator was proportional 
 to that of the motor. A stronger or "hotter" arc was therefore 
 drawn at the igniter at high speed than at low. This naturally 
 tended to decrease the time interval between the separation of 
 the contact points and the complete inflammation of the charge, 
 
INDICATOR CARDS FROM PRACTICE 275 
 
 and thus to counteract, in a measure at least, the effect of the 
 increased speed in modifying the form of the indicator diagram. 
 
 But when the jump-spark ignition system with an induction 
 coil and vibrating interrupter was put into action and the other 
 thrown out, a very considerable advance of the timer was necessary 
 to obtain the maximum torque at high speed when the motor was 
 speeded up. 
 
 Therefore, could indicator diagrams have been taken in this 
 latter case, there would undoubtedly have been a greatly inclined 
 combustion line and low explosion pressure when the speed was 
 increased and before the timer was advanced. 
 
 
CHAPTER XV. 
 ECONOMY AND EFFICIENCY. 
 
 1 86. Units of Heat Energy and Mechanical Energy. The 
 
 function of the internal-combustion motor is to transform the 
 heat energy of the fueHnto mechanical energy which is delivered 
 to machinery or other apparatus that is driven by the power 
 developed by the motor. 
 
 In order to deal with the economy and efficiency of the trans- 
 formation, it is necessary to select units for measuring the heat 
 energy and the mechanical energy. 
 
 The foot-pound (ft.-lb.) is the unit of measure of mechanical 
 energy most used in this country. It is the energy required to 
 lift one pound (avoirdupois) one foot high. (Strictly at about 
 sea level. A mass that weighs one pound on spring scales at 
 sea level weighs less at higher altitudes.) 
 
 The horsepower (h.p.) is the unit of the rate of working or of 
 delivering mechanical energy. The mechanical value of a 
 horsepower is 550 foot-pounds per second = 33,000 foot-pounds 
 per minute = 1,980,000 foot-pounds per hour. 
 
 The British thermal unit (B.t.u.) is the measure of heat energy 
 most used in this country. It is the amount of heat that will 
 raise the temperature of one pound (avoirdupois) of water one 
 degree by the Fahrenheit thermometer scale, starting from the 
 temperature of maximum density of the water (39.1 F. about). 
 
 The heat value of a fuel is stated, in the discussion which 
 follows, in the number of British thermal units that a specified 
 quantity of the fuel, as a pound or a cubic foot, will give up when 
 burned.* 
 
 The British thermal unit is equivalent to 778 foot-pounds of 
 
 * For higher and lower heat values, and methods of -determining, see 
 chapter on Combustion and Heat Values. 
 
 276 
 
ECONOMY AND EFFICIENCY 277 
 
 mechanical energy transformed into heat, as by friction between 
 two solid bodies. This is the generally accepted value. 
 
 If mechanical energy is transformed into heat at the rate of one 
 horsepower during a period of one hour, the amount of heat 
 produced will be 1,980,000 -f- 778 = 2545 B.t.u. The relation 
 between British thermal units and horsepower per hour, horse- 
 power per minute, and horsepower per second, can therefore be 
 written, for convenience: 
 
 One h.p.-hour = 2545 B.t.u. 
 One h.p.-min. = 42.416 B.t.u. 
 One h.p.-sec. = .70694 B.t.u. 
 
 187. Motor Economy Defined. It is of course desirable to 
 obtain as great an amount of mechanical energy from a given 
 quantity of fuel as is possible under suitable conditions of opera- 
 tion, thus securing the greatest economy of fuel that is compatible 
 with conditions exterior to the motor. Since the term "economy 
 of fuel" does not have a definite meaning when applied to the 
 internal-combustion motor, for the reason that a gas producer 
 may be sometimes included in this economy and at other times 
 not included, it is advisable to use the term motor economy when 
 dealing with the motor only. 
 
 The unqualified terms fuel economy of motor and motor 
 economy will be taken to mean either the amount of fuel or the 
 heat value of all the fuel that is supplied to the motor per delivered 
 horsepower per hour (D.h.p. or B.h.p. hour). The amount of fuel 
 may be expressed in different ways, as pounds of coal, cubic feet 
 of gas, pounds of combustible, British thermal units, etc. 
 
 Motor economy does not have any assumed conditions under 
 which the delivered mechanical energy is equal to the equivalent 
 heat energy of the fuel that it receives. 
 
 If a motor is operating on suction producer gas and drawing 
 the gas through and from the producer by its own power, it will 
 require more pounds of fuel gas to deliver a horsepower than if 
 the motor received the same gas at atmospheric pressure or from 
 gas mains at a pressure higher than atmospheric. More power 
 is required to pump or draw the gas through the producer into the 
 
278 THE GAS ENGINE 
 
 motor than from the atmosphere direct. This additional power 
 must be furnished by a part of the mechanical energy produced 
 by the combustion of the gas in the motor. 
 
 1 88. Motor Efficiency Defined. The measure of the economy 
 of the motor is the ratio between the amount of energy that it 
 delivers during a specified time and the amount of energy that is 
 supplied by the fuel during the same time. The former is equal 
 to the product obtained by multiplying the rate of working 
 (D.h.p.) by the time of working. The two quantities of the ratio 
 must be expressed in the same units. This can be done by multi- 
 plying the delivered horsepower hours by the value of one horse- 
 power-hour = 2545 British thermal units. 
 
 The following are convenient forms for expressing the effi- 
 ciencies : 
 
 2545 (D.h.p.) hours 
 
 Motor efficiency = ^ v e / 1 :> 
 
 B.tu. of all fuel used 
 
 or 
 
 2 545 
 
 Motor efficiency 
 
 B.t.u. of fuel used per h.p. per hour 
 
 in both of which the numerator represents the number of B.t.u. 's 
 that are equivalent to the delivered mechanical energy. 
 
 In the case of a motor whose piston diameter = n inches, 
 stroke = 12 inches, running at 290 revolutions per minute, and 
 whose guaranteed fuel economy is 1200 B.t.u. per delivered 
 horsepower per hour, the 
 
 2<545 X 1 X 1 
 
 Motor efficiency = -^^ = .212 = 21.2 per cent. 
 
 1200 
 
 And in another motor whose piston diameter = 18 inches, 
 stroke = 19 inches, running at 180 r.p.m. and guaranteed to 
 deliver one horsepower-hour at a fuel consumption of 10.5 cubic 
 feet of gas whose lower heat value is 1050 B.t.u. per cubic foot 
 at the temperature and pressure at which the gas is delivered to 
 the motor, the 
 
 Motor efficiency = 2S = .231 = 23.1 percent. 
 
 10.5 X 1050 
 
ECONOMY AND EFFICIENCY 279 
 
 Another motor with piston diameter = 8.5 inches, stroke = 
 12.75 inches, running at 300 r.p.m., is guaranteed to run 10 hours 
 on full load of 17 h.p. (D.h.p.) with a total consumption of 17 
 gallons of commercial gasoline. 
 
 The heat value of gasoline has not been accurately determined 
 on account of difficulty in getting accurate calori metric results. 
 Neither is the heat value the same for all gasoline. It probably 
 lies between 18,000 and 21,000 B.t.u. per pound. The specific 
 gravity of gasoline is different for the different grades. It may 
 be taken as .65 for this case. The weight of a gallon of pure 
 water at a temperature of 62 F. is 8.3356 pounds. The 
 weight of a gallon of gasoline at 62 F. closely approximates 
 .65 X 8.3356 = 5.42 pounds. Taking the heat value of the 
 
 gasoline as 20,000 B.t.u., the 
 
 
 
 2545 X 17 X 10 
 
 Motor efficiency = - - - =.2347 = 23.47 per cent. 
 17 X 5.42 X 20,000 
 
 A quite commonly accepted standard of fuel economy of small 
 motors is one pint of gasoline per horsepower per hour. A pint 
 of gasoline weighs about .678 pounds at 62 F. If the heat value 
 is taken as 20,000 B.t.u. per pound, then the 
 
 Motor efficiency = - - - ' = .1877 = 18.77 P er cen t- 
 .678 X 20,000 
 
 If the heat value of the gasoline is taken at 18,000 B.t.u. per 
 pound, then the 
 
 2545 X 1 X 1 
 
 Motor efficiency = ~^^ - = .208=; = 20.85 per cent. 
 .678 X 18,000 
 
 Under favorable conditions large gas engines reach a motor 
 efficiency as high as 30 per cent, corresponding to a fuel economy 
 of 8480 B.t.u. per brake horsepower (delivered horsepower) per 
 hour. 
 
 189. Impulse-Output Efficiency. The mechanical power 
 that the motor delivers (D.h.p.), which may be called the output 
 of the motor, is what remains of the indicated impulse power 
 
280 THE GAS ENGINE 
 
 (I.h.p.I) after deducting from it (a) the power lost on account of 
 the mechanical friction of the motor, (b) the power required to 
 pump or force the charge into the combustion cylinder, and (c) 
 possibly some other small consumption of power such as that for 
 driving an oil pump. The latter would generally be taken as 
 part of the mechanical friction of the motor. 
 
 The impulse-output efficiency is the ratio of the output to the 
 indicated horsepower as determined from the impulse loop of 
 the indicator diagram. The equation for it is 
 
 Impulse-output efficiency = - 
 
 I.h.p.I 
 
 This ratio is sometimes called the mechanical efficiency of the 
 motor, but this seems hardly correct, since the value of the ratio 
 is changed by variation of the pressure at which the fuel gas is 
 received, or drawn to the intake of the motor. Thus the ratio 
 has a different value when the gas is drawn through a suction 
 producer by the motor, as compared with its value when the gas 
 is received at atmospheric pressure, even though the friction 
 losses in the motor remain unchanged. 
 
 Applying the last equation to a motor whose piston diameter 
 = 6.75 inches (piston area = 35.78 square inches, there being 
 no piston rod in the combustion chamber), stroke = 15.5 inches, 
 running at 260 r.p.m. and taking 126 charges per minute, whose 
 average M.e.p.I is 102 pounds per square inch, and whose D.h.p. 
 = 15.32, first finding the I.h.p.I, gives 
 
 Ih l _ (M.e.p.I) ALY _ 102 X 45-7$ X 15.5 X 126 _ ^ ^ 
 
 33,000 33) 
 
 and 
 
 Impulse-output efficiency = = .846 = 84.6 per cent. 
 
 18.1 
 
 190. Mechanical Efficiency of Motor. The mechanical 
 efficiency of the motor is the ratio of the output (D.hp.) to the net 
 indicated power (I.h.p.N). The mean effective pressure of the 
 pumping diagram of the motor referred to in the preceding section 
 
ECONOMY AND EFFICIENCY 281 
 
 is too small to be determined accurately, and no low-spring card 
 was taken. It will be assumed that the mean effective pressure 
 of the pumping card (M.e.p.R) = two pounds per square inch. 
 The M.e.p.I is 102 pounds per square inch. Therefore the 
 M.e.p.N = 102 2 = 100 pounds per square inch. The net 
 indicated horsepower is 
 
 X 
 
 (M.e.p.N) ALY 100 X 45.78 X 15.5 X 126 
 
 I.h.p.N = = = 17-74, 
 
 33> 33 > . 
 
 and the 
 
 Mechanical efficiency = - = =.864 = 86.4 per cent. 
 
 I.h.p.N 17.74 
 
 This is but slightly different from the impulse-output efficiency, 
 but in a case like that shown in Fig. 77, where the pumping 
 loop is large, there is a very marked difference between the two 
 efficiencies. 
 
 In a two-cycle motor the average rate of the work of precom- 
 pressing the charges so as to force them into the combustion 
 cylinder is to be deducted from the average impulse rate of working 
 in order to obtain the net indicated horsepower. 
 
 191. Thermodynamic or Thermal Efficiency of the Motor. 
 This is the efficiency of transforming heat into mechanical energy. 
 It is the ratio of the mechanical energy delivered to the piston to 
 that of the heat energy liberated by the combustion of the fuel, 
 as applied to a combustion motor. Both quantities must be 
 expressed in the same unit of measure. The energy delivered to 
 the piston is that of the impulse stroke as determined from the 
 impulse loop of the indicator diagram. Remembering that one 
 horsepower-hour equals 2545 British thermal units, the equation 
 can be written, 
 
 2<4< (I.h.p.I) hours 
 
 Therm, efficiency = 3 * ^ > 
 
 B.t.u. of all fuel used 
 
 or 
 
 2 545 
 
 Therm, efficiency 
 
 B.t.u. of all fuel used per I.h.p.I per hr. 
 
282 THE GAS ENGINE 
 
 in both of which B.t.u. represents the amount of heat given up by 
 the fuel to produce the mechanical energy represented by the 
 numerator of the fraction. 
 
 Applied to a motor whose impulse loop of the diagram repre- 
 sents twenty horsepower (20 h.p.) and which operates on 1.7 gal- 
 lons of gasoline per hour, taking the heat value of the gasoline 
 as 20,000 B.t.u. per pound and the weight as 5.42 pounds per 
 gallon, the 
 
 2545 X 20 X 1 
 
 Therm, efficiency = = .276 = 27.6 per cent. 
 
 1.7 X 5.42 X 20,000 
 
 In a motor with piston diameter = 15.185 inches, stroke 
 1 8 inches, running at 175 r.p.m. per minute with an indicated 
 horsepower (I.h.p.I) = 75 and a delivered horsepower (D.h.p.) 
 = 65.1, using 10.5 cubic feet of gas having a heat value of 1050 
 B.t.u. per cubic foot, the 
 
 Therm, efficiency = = .266 = 26.6 per cent. 
 
 65.1 X 10.5 X 1050 
 
 192. Plant Economy and Efficiency. In the case of a suction 
 gas producer operating in connection with an internal-combustion 
 motor, when the power plant is entirely self-contained and there 
 is no demand for power or fuel from outside the plant to operate 
 auxiliary apparatus, the fuel economy of the plant may be expressed 
 as the amount of fuel fed to the producer per delivered horsepower 
 per hour. The amount of fuel may be stated as pounds of coal, 
 or pounds of combustible, etc., per horsepower per hour. 
 
 If fuel is used outside the producer for operating auxiliary 
 apparatus, then the total amount of fuel, or of combustible, etc., 
 must be taken into consideration in stating the economy of the 
 plant. When steam or mechanical or electrical energy from 
 some exterior source is used, and the fuel for developing the 
 power or generating the steam cannot be determined, then the 
 value of the external energy in foot-pounds or B.t.u. may be 
 taken as a basis for determining the equivalent amount of fuel 
 that would have to be used if the power were generated from 
 
ECONOMY AND EFFICIENCY 283 
 
 fuel at the plant under consideration. The details of the vari- 
 ous steps depend so much on the conditions existing that it is 
 hardly possible to give any general statement of the method to be 
 followed other than that the efficiency of the transformation of 
 the heat energy into mechanical energy may be taken the same 
 as that of the complete plant as nearly as this efficiency can be 
 determined. 
 
 The efficiency of a self-contained plant is the ratio of the 
 delivered horsepower for any specified period of time to the heat 
 value of the fuel fed to the producer during the same period. 
 And when all the power used for the motor and auxiliary apparatus 
 is generated from fuel whose amount can be directly deter- 
 mined, the efficiency is the ratio of the power delivered to the heat 
 value of the fuel used. For these two cases the mathematical 
 expression of the efficiency is 
 
 2545 X D.h.p. X hours 
 
 Plant efficiency = -*22 , 
 
 B.t.u. of all fuel used 
 
 or 
 
 2545 
 
 Plant efficiency 
 
 B.t.u. of all fuel used per D.h.p. per hr. 
 
 193. Comparison of Efficiencies. In comparing motors with 
 regard to either their motor efficiency, impulse-output efficiency, 
 or their thermodynamic efficiency, and also in comparing plant 
 efficiencies, it should be carefully observed that corresponding 
 heat values of the fuel are used in all cases. Either the higher 
 heat values should be used for all cases or the lower heat values 
 should be used for all. 
 
 A discussion of heat values is taken up in the chapter on 
 Combustion and Heat Values, 
 
CHAPTER XVI. 
 PHYSICAL PROPERTIES OF GASES. 
 
 194. Introductory to the matter to follow, some of the laws of 
 perfect (or assumed to be perfect) gases will be stated. These 
 are the laws which some of the actual gases follow more or less 
 closely, and which a "perfect" gas would follow absolutely if 
 such a gas were existent. 
 
 Within certain limited ranges of temperature not greatly 
 removed from atmospheric conditions, the actual gases follow 
 the laws of a perfect gas with sufficient accuracy to allow them to 
 be considered perfect gases for the purposes of this work. This 
 does not apply to temperatures as high as those of combustion, 
 or, in some cases, even as high as the temperatures produced by 
 compression in the combustion motor. 
 
 At temperatures as high as those at which the burned gases are 
 discharged from a combustion motor, the actual gases depart so 
 far from the laws of a perfect gas that any assumption that they 
 follow the perfect gas laws even approximately will lead to totally 
 erroneous results. 
 
 195. Density and Weight of Gases. The density of a gas is 
 its heaviness or weight referred to some standard. The standard 
 may be another gas whose density is taken as unity, or a unit 
 of weight used in connection with a unit volume. For the 
 present purpose it is convenient to express the density in pounds 
 per cubic foot. 
 
 The specific volume of a gas is the space occupied by a given 
 weight or mass of it. It will be expressed in cubic feet per 
 pound. The specific volume in cubic feet per pound is equal to 
 the reciprocal of the weight in pounds per cubic foot. 
 
 Since changes in temperature and pressure affect the volume 
 of a given weight of gas, the density and specific volume must be 
 given with reference to a definite temperature and pressure. 
 
 284 
 
PHYSICAL PROPERTIES OF GASES 
 
 28 S 
 
 TABLE I. 
 
 DENSITY AND SPECIFIC VOLUME OF GASES. 
 14.7 Ibs. per sq. in. = 2116.8 Ibs. per sq. ft. pressure. 
 
 Name. 
 
 Chemical 
 Form. 
 
 Density. 
 Lbs. per Cu. Ft. 
 
 Specific Volume. 
 Cu. Ft. per Lb. 
 
 32 F. 
 
 62 F. 
 
 32 F. 
 
 62 F. 
 
 Oxygen 
 
 2 
 
 N 2 
 C0 2 
 
 H 2 
 CO 
 
 .0893 
 .0785 
 .1227 
 .0807 
 .0056 
 .0780 
 
 .0841 
 
 0739 
 .1156 ' 
 
 .07612 
 .00528 
 .0736 
 
 1 1. 20 
 12.73 
 
 8.15 
 12.39 
 178.2 
 12.82 
 
 11.90 
 
 13-53 
 8.6 S 
 
 I3-I4 
 189.4 
 13.61 
 
 Nitrogen 
 
 Carbon dioxide 
 
 Air 
 
 Hydrogen 
 
 Carbon monoxide 
 
 Methane or marsh gas .... 
 
 CH 4 
 
 .0447 
 
 .0421 
 
 22.39 
 
 23-75 
 
 Ethylene or olefiant gas . . . 
 Propylene 
 
 C 2 H 4 
 C 3 H 6 
 C 6 H 6 
 
 .0780 
 . 1172 
 .2173 
 
 735 
 . 1104 
 .2048 
 
 12.82 
 
 8-53 
 4.60 
 
 13.60 
 9.06 
 
 4.88 
 
 Benzene vapor or benzol . * 
 
 * This is not the benzine from petroleum. 
 
 In Table I the densities and specific volumes of the gases with 
 which the combustion motor is most concerned are given for 
 atmospheric pressures and temperatures of 32 F. and 62 F. 
 
 196. Laws of a Perfect Gas. A perfect gas is one which in 
 passing through changes of temperature, pressure, and volume, 
 behaves in accordance with the following laws, using absolute 
 temperatures and pressures : 
 
 Pressure varies inversely as the volume when the temperature 
 is constant. (Law of Mariotte and Boyle. ) 
 
 Pressure varies directly as the absolute temperature when the 
 volume is constant. 
 
 Volume varies directly as the absolute temperature when the 
 pressure is constant. (Law of Charles.) 
 
286 THE GAS ENGINE 
 
 * Specific heat (per unit weight) is constant for all tem- 
 peratures and pressures. This refers to both the specific 
 heat of constant volume and the specific heat of constant pres- 
 sure. The values of these specific heats are different for any 
 gas, but each has its own constant value peculiar to that 
 perfect gas. 
 
 The absolute pressure zero is about 14.7 pounds per square 
 inch below atmospheric pressure near sea level, f 
 
 The zero of absolute temperature is about 459 degrees below 
 the ordinary Fahrenheit zero ( 459 F.). To obtain the abso- 
 lute temperature corresponding to any reading of the Fahrenheit 
 thermometer, 459 degrees must be added to the reading. 
 
 Absolute temp. Fahr. = Thermometer reading + 459 F. 
 
 The volume change of a perfect gas for each Fahrenheit degree 
 change of temperature (at any temperature) is ^y of its volume 
 at 32 F. when the pressure remains constant. If the volume of 
 the gas at 32 F. is 491 cubic feet, then at 31 F. it will be 490 
 cubic feet; at 22 F. 481 cubic feet; at zero F. by the ther- 
 mometer it will be 459 cubic feet; and at 459 F., which is 
 the absolute zero, its volume will be zero theoretically for the 
 perfect gas. 
 
 At a temperature of 33 F. the volume of the gas will be 492 
 cubic feet; at 62 F. it will be 491 + (62 32) = 491 -f 30 = 
 521 cubic feet. 
 
 The pressure change of a perfect gas for each Fahrenheit degree 
 change of temperature (at any temperature) is | T of its pressure 
 at 32 F. when the volume remains constant. The pressure at 
 absolute zero is therefore zero. 
 
 * The term "specific heat" without further qualification is understood to 
 mean the specific heat of unit weight. Volumetric specific heat is also used. 
 The latter is the specific heat of unit volume and is variable with changes of 
 temperature and pressure if the specific heat per unit weight is constant, or 
 in any case except where the specific heat per unit weight varies inversely 
 as the temperature and pressure. 
 
 f A sufficiently accurate approximation of the decrease of pressure with 
 increase of altitude, for the present purpose, is one-half pound per square inch 
 decrease of pressure for each 1000 feet of altitude. 
 
PHYSICAL PROPERTIES OF GASES 
 
 287 
 
 The above laws of a perfect gas may be expressed mathe- 
 matically as follows: 
 
 p. 
 
 F, 
 Vi 
 
 v\ 
 V n 
 
 p_ 
 p, 
 
 P.V, 
 
 For constant volume. 
 
 For constant pressure. 
 
 For constant temperature. 
 
 In each of these equations the sume subscript indicates coin- 
 cident values, and the notation is : 
 
 P = absolute pressure. (The zero pressure is at 14.7 Ibs. per 
 
 sq. in. = 2116. 8 Ibs. per sq. ft. below atmospheric 
 
 pressure at sea level); 
 V = volume; 
 T = absolute temperature. (The zero temperature is at 
 
 459 F., which is 491 F. below the freezing point of 
 
 water at atmospheric pressure); 
 P v V v 7\= the initial condition; 
 P 2 , F 2 , T 2 = the changed or final condition. 
 
 And, in accordance with the laws of a perfect gas, 
 
 P V T 
 
 * \ v i _ * i 
 
 P V T 
 
 r 2 V 2 ^2 
 
 197. Example. Find the weight of a cubic foot of air at a 
 temperature of 102 F. and a pressure of 20 pounds per square 
 inch absolute. 
 
 In Table I the density in pounds per cubic foot is given for 
 both 32 F. and 62 F. at 14.7 pounds per square inch absolute 
 
288 THE GAS ENGINE 
 
 pressure. The air can be reduced to its equivalent volume at 
 either of these temperatures and its weight obtained by multiply- 
 ing the volume at that temperature by the weight per cubic foot 
 at the same temperature. The temperature of 62 F. will be 
 taken as that at which the equivalent volume is to be found. 
 The given quantities are: 
 
 Initial volume = 1 cu. ft. ; 
 
 Initial temp. = 102 F. = 102 + 459 = 561 absolute F.; 
 
 Initial pres. = 20 Ibs. per sq. in. absolute; 
 
 Final temp. = 62 F. = 62 + 459 = 521 absolute F.; 
 
 Final pres. =14.7 Ibs. per sq. in. absolute. 
 
 The computations will be made in two steps by first finding 
 the change of volume due to the change of temperature at constant 
 pressure and then the change of volume due to change of pressure 
 at constant temperature. 
 
 The equations of section 196 can be applied. The subscript 
 1 will be taken to represent the initial conditions for the change 
 under consideration for the moment, and the subscript 2 to repre- 
 sent the final condition of the same change. 
 
 The equation for the change at constant pressure, modified in 
 form for convenience, is 
 
 v- 
 
 The substitution of the initial values in this equation gives 
 
 _ 1X521 = cu ft 
 
 56i 
 
 at 62 F. and 20 pounds per square inch pressure. 
 
 The equation for the change of pressure and volume at constant 
 temperature, modified in form for convenience, is 
 
PHYSICAL PROPERTIES OF GASES 289 
 
 The initial volume to be substituted in this c#se is the .928 
 cubic foot obtained by the last computation. By substituting 
 this and the other quantities in the last equation it becomes 
 
 .928 X 20 
 
 F 2 = - = 1.26 cu. ft, 
 
 14.7 
 
 which is the volume at 62 F. and 14.7 pounds per square inch 
 pressure. 
 
 The weight of air at this temperature and pressure, as given 
 in Table I, is .07612 of a pound per cubic foot. The weight 
 of a cubic foot of air at the given temperature of 102 F. and 
 pressure of 20 pounds per square inch absolute, is therefore 
 
 1.26 X .07612 = .096 Ib. 
 
 Instead of making the computations in two steps, as above, for 
 reducing a cubic foot of gas at the observed temperature and 
 pressure to its equivalent volume at 62 F. and 14.7 pounds per 
 square inch pressure, the reduction can be made direct by the last 
 equation of section 196. This equation, after transposing to a 
 suitable form for application, is 
 
 Whence, by substitution, 
 
 20 X 1 X 521 
 
 F, = - = 1.26 cu. ft, 
 
 14.7 X 561 
 
 198. The specific heat of a gas (per unit weight) is the amount 
 of heat required to raise the temperature one degree. It is often 
 given for two different conditions, one for constant pressure and 
 the other for constant volume. It is convenient for the present 
 purpose to express the specific heat in British thermal units per 
 pound of gas. 
 
THE GAS ENGINE 
 
 TABLE II. 
 
 SPECIFIC HEATS OF GASES. 
 
 For Atmospheric Temperatures. 
 
 Gas. 
 
 Chem- 
 ical 
 Form. 
 
 Specific Heat. Can be taken as 
 B.t.u. per Lb. 
 
 Per Pound. 
 
 Per Cu. Ft. at 
 14.7 Lbs. per Sq. In. 
 
 Con- 
 stant 
 Pres- 
 sure. 
 
 Con- 
 stant 
 Vol- 
 ume. 
 
 Constant 
 Pressure. 
 
 Constant 
 Volume. 
 
 32 F. 
 
 62 F. 
 
 32 F. 
 
 62 F. 
 
 Oxygen 
 
 2 
 
 N 2 
 C0 2 
 
 2175 
 .2438 
 .2170 
 
 2 375 
 3-409 
 .2479 
 
 5929 
 .4040 
 
 155 
 
 173 
 .171 
 .169 
 2.406 
 
 173 
 .467 
 
 332 
 
 .0194 
 .0191 
 . 0266 
 .0192 
 .0191 
 .0195 
 .0265 
 0343 
 
 .0183 
 .0180 
 .0251 
 .0181 
 .0180 
 .0182 
 .0250 
 .0297 
 
 .0138 
 .0136 
 
 .0210 
 .0136 
 0135 
 I35 
 .0209 
 .0259 
 
 .0130 
 .0128 
 .0198 
 .0127 
 .0127 
 .0127 
 .0197 
 .0244 
 
 Nitrogen 
 Carbon dioxide 
 
 Air 
 
 Hydrogen 
 
 H 2 
 CO 
 CH 4 
 C 2 H 4 
 
 Carbon monoxide 
 Methane or marsh gas 
 Ethylene or olefiant gas 
 
 
 The specific heat of constant volume (by weight) is the amount 
 of heat, in British thermal units, that must be given to a pound 
 of gas to raise its temperature one degree Fahrenheit while the 
 volume remains unchanged. This corresponds to adding a 
 B.t.u. of heat to a pound of gas enclosed in a vessel of fixed volume 
 whose walls are impermeable to heat. 
 
 The specific heat of constant pressure (by weight) is the amount 
 of heat that must be given to a pound of the gas to raise its tem- 
 perature one degree Fahrenheit while the pressure remains con- 
 stant. This corresponds to heating the gas in a vertical cylinder 
 with a free frictionless piston closing the upper end, whose weight 
 determines the gaseous pressure. When heat is. added to the 
 gas its temperature rises and it expands so as to lift the piston 
 
PHYSICAL PROPERTIES OF GASES 291 
 
 against the constant resistance of the weight of the piston (and 
 also against atmospheric pressure if the latter acts on the exposed 
 side of the piston), which gives a constant gas pressure. 
 
 The specific heat of constant pressure is greater than that of 
 constant volume. At constant volume only enough heat is added 
 to raise the temperature, but at constant pressure there must be 
 enough heat added not only to increase the temperature but also 
 to do the work of expanding the gas, as in the case of lifting the 
 piston, just mentioned. 
 
 The specific heats just mentioned can be taken as practically 
 constant for atmospheric temperatures. But for the high tem- 
 peratures of combustion the specific heat has been found to 
 increase rapidly with increase of temperature. Variation of 
 pressure, dealing with pressures as high as those of the combustion 
 motor, also causes variation of the specific heats. 
 
 199. Example. Find the amount of heat necessary to raise 
 the temperature of 3 pounds of carbon monoxide (CO) from 
 32 F. to 62 F. at atmospheric pressure. 
 
 This is a case of change of temperature at constant pressure. 
 The specific heat of constant pressure for CO is given in Table II 
 as .248 B.t.u. per pound. The amount of heat required to raise 
 the temperature as stated is 
 
 3 (62 - 32) .248 = 3 X 30 X .248 = 22.32 B.t.u. 
 
 200. Volumetric Specific Heat. It is sometimes convenient 
 to use the amount of heat that will change the temperature of a 
 unit volume (as a cubic foot) of gas one degree. 
 
 The volumetric specific heat of a cubic foot of gas at any tem- 
 perature and pressure can be found by multiplying the specific 
 heat of the gas in British thermal units per pound of the gas by 
 the weight of the gas per cubic foot at the temperature and 
 pressure taken. The specific heat by weight must be that for 
 the temperature and pressure at which the gas is taken. The 
 volumetric specific heat is really the specific heat of a weight of 
 gas determined by the pressure and temperature. It is not the 
 same at different temperatures or at different pressures. 
 
 In Table II the specific heats of the more important fuel gases 
 
292 THE GAS ENGINE 
 
 for the "combustion motor, and of the products of combustion, 
 are given in British thermal units per pound and also per cubic 
 foot for temperatures of 32 F. and 62 F. at atmospheric pres- 
 sure. 
 
 201. Example. Find the heat required to raise the tem- 
 perature of 3 cubic feet of carbon monoxide (CO) from 32 F. to 
 62 F. at atmospheric pressure. The volumetric specific heat of 
 CO is given in the table as .0195 B.t.u. per cubic foot for a constant 
 pressure of 14.7 pounds per square inch pressure and at a tem- 
 perature of 32 F. The amount of heat necessary for the 
 required change is 
 
 3 (62 - 32) .0195 = 3 X 30 X .0195 = 1.755 B.t.u. 
 
 Example. What amount of heat will a cubic foot of CO give 
 out while cooling from 62 F. to 32 F. at atmospheric pressure? 
 
 The volumetric specific heat of CO at 62 F. and 14.7 pounds 
 per square inch pressure is given in the table as .0182 for con- 
 stant pressure. The heat given out during the change will be 
 
 3 (62 - 32) .0182 = 3 X 30 X .0182 = 1.638 B.tu. 
 
CHAPTER XVII. 
 COMBUSTION AND HEAT VALUES. 
 
 202. Combustion and Volumetric Change Due to Combustion. 
 
 - Combustion, taken in the broadest sense, is the chemical 
 combination of elements or compounds accompanied by the 
 liberation or production of heat. As used in relation to the 
 internal-combustion motor and to the manufacture of com- 
 bustible gases from solid and liquid fuels for the motor, com- 
 bustion means, as has been previously stated, the chemical union 
 of oxygen with the carbon, hydrogen, or other chemical elements 
 and compounds in the fuel. Carbon, hydrogen, the hydrocar- 
 bons (which are numerous compounds of hydrogen and carbon 
 in different proportions), and carbon monoxide are practically 
 all the fuels that are considered, however. 
 
 The volume of the gaseous products of combustion differs in 
 many cases from that of the combustible mixture that is burned 
 when both the combustible mixture and the gaseous products of 
 combustion are brought to and compared at the same temperature 
 and pressure. In some cases there is a decrease of specific 
 volume due to combustion, in others an increase, and in still 
 others no change of specific volume. 
 
 If hydrogen and oxygen are chemically combined by burning, 
 the volume of the steam formed is less than that of the mixture of 
 hydrogen and oxygen before combustion, both taken at the same 
 temperature, as just stated. This is shown by the following 
 chemical equation, which deals with molecular quantities. 
 
 2 VOl. I VOl. 2 VOl. 
 
 2 H 2 + O 2 = 2 H 2 O (Hydrogen. Contraction = ^-.) 
 
 The same contraction is shown in the combustion of carbon 
 monoxide burned to carbon dioxide, as follows : 
 
 2 VOl. I VOl. 2 VOl. 
 
 2 CO + 2 = 2 CO 2 (Carbon monoxide. Contraction = ^.) 
 
 293 
 
294 THE GAS ENGINE 
 
 In both the above cases three volumes of the combustible 
 mixture (two volumes of hydrogen and one of oxygen in the first 
 case, and in the second case two volumes of carbon monoxide and 
 one of oxygen) produce two volumes of gas by burning. The 
 volume of the burned gases is only two- thirds that of the mixture 
 in each case. 
 
 But in the combustion of marsh gas (methane) there is no 
 change of volume, and the same is true of ethylene (olenant gas), 
 as shown in the two following equations. 
 
 i vol. 2 vol. i vol. 2 voK 
 
 CH 4 + 2 O 2 = C0 2 + 2 H 2 O (Methane. Volume change = o.) 
 
 1 vol. 3 vol. 2 vol. 2 vol. 
 
 C 2 H 4 + 3 2 = 2 C0 2 + 2 H 2 (Ethylene. Volume change = o.) 
 
 In each of the last two cases three volumes of the combustible 
 mixture produce three volumes of the burned gases. 
 
 Propylene and benzol both show an increase of volume in the 
 products of combustion, as the following two equations indicate. 
 
 2 vol. 9 vol. 6 vol. 6 vol. 
 
 2 C 3 H 6 + gO 2 = 6C0 2 + 6H 2 (Propylene. Expansion = T 1 T .) 
 
 2 vol. 15 vol. 12 vol. 6 vol. 
 
 2 C 6 H 6 + 15 O 2 = 12 C0 2 + 6 H 2 (Benzol. Expansion = iV-) 
 
 Contraction of volume, at equal temperatures and pressures, 
 by combustion has the effect of reducing the pressure that would 
 be produced by combustion if there were no contraction of 
 volume. The indicator diagram takes into account such varia- 
 tion of volume by combustion. The reduction of volume is not 
 as great when air is used to furnish the oxygen for combustion 
 as is shown by the above equations, which deal only with the 
 chemically active constituents of the combustible mixture. The 
 residual inert (burned) gases in the motor cylinder also help to 
 reduce the ratio of contraction. There is therefore a certain 
 advantage, in relation to contraction, in having the combustible 
 mixture diluted with the nitrogen of the air and by the inert 
 residual gases of a preceding combustion. 
 
 There is also an advantage in the dilution of the combustible 
 
COMBUSTION AND HEAT VALUES 295 
 
 mixture on account of keeping down the temperature of the 
 products of combustion in view of the fact that the specific heat 
 increases rapidly with the rise of temperature for temperatures as 
 high as those of combustion, under the conditions of operation 
 of the combustion motor. 
 
 203. Complete and Incomplete Combustion. Complete com- 
 bustion is the combination of chemical elements in the proportion 
 to form their most stable compound. 
 
 Incomplete combustion with oxygen is the process of the 
 chemical union of the fuel element with the oxygen in a proportion 
 that produces a compound which is not stable in the presence of 
 more oxygen under proper conditions for adding more of the 
 oxygen to the compound. 
 
 As an example, carbon combines with oxygen in either of two 
 proportions, according to the conditions of combustion, to form 
 either CO or CO 2 . When there is enough oxygen present, CO 2 
 is formed. An excess of oxygen does not modify this proportion 
 of combination. The change from C to CO 2 is complete com- 
 bustion, for if the CO 2 is heated in the presence of more oxygen 
 it will not combine with any more of it. 
 
 But if there is just enough oxygen present to combine with 
 the carbon to form CO, then all the carbon will burn to CO. 
 This is incomplete combustion. The CO is not a stable com- 
 pound, for if it is mixed with more oxygen and ignited, all or part 
 of the CO will burn to CO 2 according to the amount of free 
 oxygen present. 
 
 If there is more than enough oxygen present with the carbon 
 to form CO, but not enough to form CO 2 of all the carbon, then 
 burning the mixture will produce both CO and CO 2 in such pro- 
 portions as will take up all the oxygen. This action is also called 
 incomplete combustion in engineering practice. 
 
 The chemical reactions of combustion are expressed in the 
 following atomic equations: 
 
 C + 2 = C0 2 . Complete combustion of carbon. 
 C + O = CO. Incomplete combustion of carbon. 
 CO + =5 CO 2 . Complete combustion of CO. 
 
296 THE GAS ENGINE 
 
 The first equation represents the change that occurs when 
 coke or charcoal is burned with a plentiful supply of air and the 
 temperature of the fuel is kept high, as indicated by a white heat. 
 The second equation indicates the change if there is but a scant 
 supply of air and the fuel shows only a red heat. The third 
 equation is the expression for the combustion of the unstable 
 product, CO, of incomplete combustion of carbon. 
 
 204. Heat of Combustion is Constant. The chemical com- 
 bination of carbon with oxygen in the proportion to form carbon 
 dioxide, CO 2 , always liberates the same amount of heat, whether 
 the rate of combustion is rapid or slow. The amount of heat 
 liberated is also always the same whether the combination is 
 made directly into the form CO 2 , or first into CO and then from 
 CO to CO 2 . The heat liberated while changing from C to CO 
 is always a fixed amount, and so is that for the combination of CO 
 with O to form CO 2 . The sum of the amounts of heat produced 
 during the last two steps (C to CO and the resulting CO to CO 2 ) 
 is equal to that produced during the direct change from C to CO 2 . 
 
 In the same manner, hydrogen always liberates the same 
 amount of heat when combined with oxygen to form water vapor 
 or steam, H 2 O. The other combustible elements and compounds 
 follow the same law. 
 
 When a number of different kinds of gases, as H, CO, CH 4 , etc., 
 are mechanically mixed together, as in the case of power gas and 
 illuminating gas, the heat liberated by the combustion of the 
 mixture is the same in amount as if each constituent (H, CO, 
 CH 4 , etc.) were burned separately and all the heat thus produced 
 added together. This does not apply to the breaking up of a 
 chemical compound (such as CH 4 ) into its elements. 
 
 205. The heat value or calorific power of a fuel, when not 
 qualified more definitely, is ordinarily understood to mean the 
 amount of heat that is liberated by burning a unit weight or a 
 unit volume of the fuel and bringing the temperature and pressure 
 of the products of combustion back to the same values that the 
 fuel and the supporter of combustion (generally air) had before 
 ignition. Since it is practically impossible to maintain such a 
 final pressure and temperature during the burning of the fuel in 
 
COMBUSTION AND HEAT VALUES 
 
 297 
 
 a calorimeter, the necessary corrections in the readings obtained 
 are made to secure the same result as if the initial and final 
 temperatures and pressures had been the same. And since water 
 is used in the calorimeter to take up the heat of combustion, both 
 the initial and final temperatures at the calorimeter are necessarily 
 below the boiling point of water. The water vapor produced by 
 combustion when hydrogen is present is therefore condensed 
 into liquid water. 
 
 The proportions by weight in which the fuel and oxygen com- 
 bine, the weight of air necessary to supply the required oxygen 
 when air is used in accordance with the method of commercially 
 burning any fuel, and the weight of the resulting products of 
 combustion can all be determined by the aid of the chemical 
 equations and atomic weights of the chemical elements. In the 
 following illustrative equations, the atomic weights are taken for 
 convenience in the approximate round numbers commonly used 
 for such purposes. 
 
 TABLE III. 
 
 APPROXIMATE ATOMIC WEIGHTS. 
 
 Substance . 
 
 Symbol. 
 
 Atomic 
 Weight. 
 
 Carbon 
 
 c 
 
 12 
 
 Hydrogen 
 
 H 
 
 I 
 
 Oxvffen 
 
 o 
 
 16 
 
 
 
 
 The accurate atomic weight of hydrogen as reported by the American Chemical 
 Society is 1.008. 
 
 The relative proportions by weight in which CO and oxygen 
 combine are shown in the equation 
 
 CO + = C0 2 
 
 28 1 6 44 Proportions by weight. 
 
 When one pound of CO is burned to CO 2 , the weight of the 
 oxygen required and the weight of the products of combustion 
 are directly obtained by dividing the above equation by 28 
 
298 
 
 THE GAS ENGINE 
 
 (which is the weight of CO burned as represented in the above 
 equation) with the following result. 
 
 CO + = C0 2 
 
 Pounds. i .57 1.57 
 
 When the oxygen is supplied by bringing air into contact with 
 the fuel, the weight of the air required and of the resulting products 
 is obtained in a similar manner. 
 
 Air is composed chiefly of oxygen and nitrogen in the propor- 
 tion of i part oxygen and 3.326 parts nitrogen by weight. Water 
 vapor is also present in variable amounts. To get the .57 pounds 
 of O that must be supplied, there must be 4.326 X .57 = 2.470 
 pounds of air, neglecting moisture, of which 2.47 .57 = 1.9 
 pounds are nitrogen. The nitrogen remains chemically inert 
 during combustion. The chemical equation is 
 
 CO + C0 2 
 
 57 i-57 
 
 Pounds. 
 
 2.47 Air. 3.47 Products. 
 
 When carbon is burned to CO 2 the equations similar to the 
 above two are 
 
 and 
 
 C + 
 
 12 16 
 
 C + 
 
 - CO 
 
 28 Proportions by weight. 
 
 
 
 CO 
 
 Pounds. * 
 
 i-33 
 4-43 N 
 5.76 Air. 
 
 2 -33 
 
 4-43 N 
 
 6.76 Products. 
 
 The additional air for burning the products, as determined in 
 the last equation, to CO 2 , and the resulting final products, are 
 
 CO + O = C0 2 
 
 i r 2.33 i-33 3- 66 
 
 Pounds, j 4-43 N 4-43 N 8.86 N 
 
 [6.76 5.76 Air. 12.52 Products. 
 
COMBUSTION AND HEAT VALUES 299 
 
 When carbon is burned directly to CO 2 in air, 
 
 and 
 
 C -f 
 
 12 
 
 -2O = C0 2 
 
 3 2 44 
 
 Proportions 
 
 C 
 
 + 20 
 
 C0 2 
 
 f 1 
 
 Pounds, j 
 
 2.66 
 
 8.86 N 
 
 3.66 
 
 8.86 N 
 
 [ ii. 52 Air. 12.52 Products. 
 
 By adding together the heat of burning one pound of carbon to 
 CO, which is 4206 B.t.u., and that of burning the resulting 2^ 
 pounds of CO to CO 2 ,which is 2^- X 4476 = 10,444 B.t.u., the 
 sum, 
 
 4206 + 10,444 = 14)650 B.t.u., 
 
 is the same as the heat produced by burning the pound of carbon 
 direct to CO 2 . 
 
 The proportions by volume for the burning of CO with O are 
 shown in the following molecular equation. 
 
 212 Volume proportions. 
 2 CO + 2 = C0 2 
 
 56 32 88 Weight proportions. 
 
 The burning of one cubic foot of CO in air is represented in 
 the following equation, in which the volumes are taken at 62 F. 
 and 14.7 pounds per square inch pressure. 
 
 
 \ 
 
 2.39 Air. 
 
 2.89 P: 
 
 Cu. ft. 
 
 1 
 
 1.89 N 
 
 1.89 N 
 
 
 I i 
 
 5 
 
 I.OO 
 
 
 CO 
 
 + 
 
 C0 2 
 
 Pounds. 
 
 .0736 
 
 .0421 
 
 "57 
 
 The cubic feet of oxygen and air involved in burning one pound 
 of carbon to CO, and then burning the resulting CO to CO 2 , are 
 shown in the next two equations. 
 
300 
 
 THE GAS ENGINE 
 
 Cu. ft. 
 
 Pounds, 
 
 Cu. ft. 
 
 Pounds. 
 
 
 75.8 Air. 
 
 91.7 Products. 
 
 
 60.0 N 
 
 60.0 N 
 
 . 
 
 15.8 
 
 3 T -7 
 
 C 
 
 + 
 
 CO 
 
 I 
 
 i-33 
 
 2-33 
 
 '91.7 
 
 75.8 Air. 
 
 151.7 Products. 
 
 60.0 
 
 N 60.0 N 
 
 120.0 N 
 
 .31-7 
 
 15.8 
 
 3*-7 
 
 CO 
 
 + 
 
 = C0 
 
 3! 
 
 For one pound of carbon burned direct to CO 2 the following 
 applies : 
 
 151.7 Air. 151.7 Products. 
 Cu. ft. 
 
 I2O.O N 
 
 C + 20 
 
 Pounds. 
 
 I2O.O N 
 
 3 1 -? 
 CO, 
 
 ->2 
 
 3s 
 
 And for one pound of CO burned to CO 2 : 
 
 32.5 Air - 39-3 Products. 
 
 Cu. ft. J - 25.7 N 25.7 N 
 
 [13.59 6.8 13.6 
 
 CO + C0 2 
 
 Pounds. i .C7 i 57 
 
 +} I O i 
 
 Dealing with hydrogen in a similar manner, the equation for 
 relative weights is 
 
 2H + 
 
 2 16 
 
 H 2 
 
 1 8 Weight proportions. 
 
 And for the volumetric proportions: 
 
 2H 2 + O 2 = 2H 2 (Steam). 
 
COMBUSTION AND HEAT VALUES 
 
 301 
 
 The weight and volume proportions of the gafces involved in 
 the combustion of hydrogen in air are given in the following 
 equation for one pound of hydrogen. 
 
 Cu. ft. 
 
 Pounds. 
 
 
 455 Air - 
 
 550 Products. 
 
 
 360 N 
 
 ^6o~N 
 
 190 
 
 95 
 
 190 
 
 2H 
 
 + 
 
 H 2 
 
 [' 
 
 8 
 
 9 
 
 
 26.6 N 
 
 26.6 N 
 
 
 34.6 Air. 
 
 35.6 Products 
 
 And for one cubic foot of hydrogen : 
 
 Cu. ft. 
 
 Pounds. 
 
 
 2.39 Air. 
 
 2.89 Products. 
 
 1.89 N 
 
 1.89 N 
 
 I 
 
 2H + 
 
 50 
 
 
 i.oo' 
 H 2 
 
 ^00528 
 
 .04205 
 .13968 N 
 
 0473 
 .1397 N 
 
 .17175 Air. .1870 Products. 
 
 206. Economy and Efficiency of a Combustion Motor as 
 Affected by using Calorimeter Determinations of the Heat Value 
 of Hydrogen. The combustible parts of the fuels used in com- 
 bustion motors are hydrogen and carbon with possible inappre- 
 ciable amounts of other chemical elements. The carbon of the 
 fuel is combined with either oxygen in the combustible compound 
 CO or with hydrogen in some of the numerous hydrocarbons. 
 Sometimes more than half of the volume of the fuel gas is free 
 hydrogen, as in some of the water gases. 
 
 In calorimeter determinations of the heat value of fuels the 
 products of combustion are always cooled enough to condense 
 the steam resulting from the combination of H with O. But in 
 the case of the internal-combustion motor the H 2 O, CO 2 , and N 
 are all discharged in a gaseous state. 
 
302 THE GAS ENGINE 
 
 The fuel economy of an internal-combustion motor, or any 
 efficiency that involves the transformation of heat energy into 
 mechanical energy when using fuel mixtures whose combustible 
 part is CO only, will not be the same in value as when the same 
 motor is using a fuel mixture that contains H if the heat value 
 of the H, or of its compounds, is based on calorimeter determina- 
 tions that take into account the heat given up by the condensation 
 of the steam produced by the combustion of the H, when all other 
 conditions that affect the thermal efficiency of the motor are the 
 same in both cases. 
 
 The extreme differences of efficiencies and of economies will 
 occur when the combustible part of the fuel in one case is CO 
 only, and in the other case free H only. While the combustible 
 portions of the fuels that are used in combustion-motor practice 
 are never exclusively CO or H, the assumption that a motor 
 operates at one time on CO as the sole combustible, and at 
 another time on H as the only combustible, gives the simplest 
 means of showing the differences of fuel economies and of effi- 
 ciencies, as stated above. 
 
 It will also be assumed that a given motor operates under a 
 given load and at a constant speed. The indicated horsepower 
 of the impulses (I.h.p.I) must then always be the same without 
 regard to the kind of fuel used, if the mechanical efficiency 
 remains constant. Constant mechanical efficiency will be 
 assumed. 
 
 The indicated horsepower of the impulses (I.h.p.I) of a given 
 motor at constant speed is directly proportional to the mean 
 effective pressure of the impulse (M.e.p.I). The M.e.p.I must 
 therefore have a constant value for a constant load. 
 
 To obtain a given M.e.p.I with the same compression pressure 
 of the fuel charge, the amount of heat added to the charge by 
 combustion in the motor must be the same in all cases, whatever 
 fuel is used, provided the specific heat of the gases in the cylinder 
 after combustion is the same whether CO or H is the combustible 
 part of the fuel used. Equal specific heats will be assumed for the 
 purpose of illustration. 
 
 The only part of the heat of combustion of H, as determined 
 
COMBUSTION AND HEAT VALUES 303 
 
 by the water-cooled calorimeter in which the steam of combus- 
 tion is condensed, that is effective in producing temperature and 
 pressure changes in the steam, is that in excess of the amount 
 given up during the condensation of the steam produced and the 
 cooling of the watef resulting from condensation. This may 
 appear clearer by following the application of heat to water 
 to convert it into steam and then to superheat the steam in a 
 closed vessel which has a free-moving piston. The first part of 
 the heat raises the temperature of the water till the boiling point 
 is reached. Further addition of heat converts the water into 
 steam without increase of temperature, the pressure remaining 
 constant, and when the water is completely evaporated more 
 heat applied goes to superheat the steam, increasing both its 
 temperature and volume if the pressure is still kept constant by 
 the movement of the piston; or, if the piston is locked in position 
 when the evaporation is complete, the temperature and pressure 
 are both increased, while the volume remains constant. The 
 steam behaves as a permanent gas as long as the temperature is 
 kept somewhat above that of condensation at the corresponding 
 pressure. The only part of the heat that is effective in raising 
 the temperature and pressure of the steam is that which is added 
 after the water is completely evaporated. And, conversely, 
 when the steam is cooled, the heat that is given up before con- 
 densation begins represents all the heat that is useful for changing 
 the pressure, volume, and temperature of the steam. The same is 
 true whenever steam gives up its heat, from whatever source the 
 heat was received. 
 
 Each pound of steam formed by the combustion of hydrogen 
 gives up 1146.6 B.t.u. of heat when it is condensed from 212 F. 
 and 14.7 pounds per square inch absolute pressure and the water 
 cooled to 32 F. The 9 pounds of steam formed by the com- 
 bustion of one pound of H therefore give up, during the same 
 change, 
 
 9 X 1146.6 = 10,320 B.t.u. about. 
 
 None of this heat (10,320 B.t.u.) acts on the gases in the motor 
 to cause changes of temperature and pressure, for the tempera- 
 
304 THE GAS ENGINE 
 
 ture and pressure at which the gases are discharged from the 
 motor are higher than those at which steam condenses. 
 
 The total heat of combustion of H, as determined by the calo- 
 rimeter, when the initial temperature of the combustible mixture 
 is 32 F. and the pressure is 14.7 pounds per square inch absolute, 
 and the resulting products cooled to the same temperature, is 
 about 62,100 B.t.u. per pound of H. Of this there are 10,320 
 B.t.u. that have no effect on the temperature and pressure of the 
 steam in the application to the combustion motor. The 
 remainder, 
 
 62,100 - 10,320 = 51,780, 
 
 is all that is effective in producing changes of temperature and 
 pressure in the gases in the motor. 
 
 Therefore the ratio of the total heat of combustion of H (from 
 32 F. and 14.7 pounds per square inch absolute pressure to 
 water at the same temperature) to the part of the heat that is 
 active in the motor is 
 
 62,100 
 
 = 1.2. 
 
 5^780 
 
 Under the assumptions made, if 100 B.t.u. value of CO is 
 necessary to produce the required mean effective pressure of 
 impulse (M.e.p.I) in the motor when CO is the only fuel, then 
 when H alone is used as the fuel 120 B.t.u. value of the H will 
 be required to obtain the same M.e.p.I, dealing with the heat 
 values of the fuels as determined by the calorimeter. 
 
 The ratio of the thermal efficiency with CO to that with H as 
 the fuel is 1.2 in this case. The ratios of the total efficiencies 
 will also be greater than unity. The economies will show 20 per 
 cent more combustible for H than for CO when expressed in 
 heating values. 
 
 In making a guaranty of the performance of a motor, expressed 
 in B.t.u. per delivered horsepower, or in efficiency, it would there- 
 fore be necessary to know the composition of the fuel to be used 
 if the calorimeter-determined heat values are to be -taken. This 
 would bring on endless difficulties. In order to avoid such 
 
COMBUSTION AND HEAT VALUES 305 
 
 complications, a modification of the heat value of H, or of any 
 fuel containing H, as determined by the water-cooled calorimeter, 
 has been brought into engineering use. This modification is 
 known as the " lower heat value" of the fuel. In order to distin- 
 guish between the calorimeter-determined value and the lower 
 heat value the former is called the "higher heat value." 
 
 207. Higher Heat Values. Two higher heat values or 
 calorific powers of a combustible find use in the combined fields 
 of engineering, physics, and chemistry. The initial temperature 
 is generally taken as 32 F. in physics and chemistry. The 
 engineer uses a higher initial and final temperature in order to be 
 nearer to the actual conditions of practice. This higher tem- 
 perature will be taken as 62 F. 
 
 The heat values of combustibles that do not contain H are not 
 appreciably different for the different temperature bases, but 
 there is a marked difference when H is present in considerable 
 proportion. 
 
 208. Higher Heat Values of Hydrogen. The higher heat 
 value of H from 32 F. and 14.7 pounds per square inch pressure 
 to water at the same temperature and pressure has already been 
 given as 62,100 B.t.u. per pound. 
 
 When the initial temperature of the combustible mixture is 
 higher than 32 F., and the water of combustion is condensed to 
 the same (higher) temperature, there will be a modification of 
 the higher heat value just given on account of the difference of the 
 specific heats of the combustible mixture and of the water formed. 
 The combustible mixture contains more heat at the higher tem- 
 perature than at 32 F., and this additional heat is a gain in the 
 heat value. But the condensed water also has more heat at 
 the higher temperature than at 32 F., and this causes a loss in 
 the heat value, since this heat is retained in the condensed water 
 and not given up to the calorimeter. 
 
 For illustrating this, the specific heats of the substances involved 
 must be used. 
 
 B.t.u. 
 
 Specific heat of H per pound at constant pressure 3 .409 
 
 Specific heat of O per pound at constant pressure 2I 75 
 
 Specific heat of water per pound can be taken as sufficiently 
 
 accurate for this purpose at i - ooo 
 
306 THE GAS ENGINE 
 
 For an initial temperature of 62 F. the gain of heat over that 
 at 32 F. for 1 pound of H and 8 pounds of O is: 
 
 B.t.u. 
 
 Gain for the H = 1 (6232) 3.409 = 102.27 
 
 Gain for the O = 8 (6232) 2175= 52.20 
 
 Total heat gain for 9 pounds combustible = . . 154 
 
 The heat deduction for the final temperature (62 F.) of the 
 9 pounds of water produced is, 
 
 B.t.u. 
 Heat loss for 9 pounds water = 9 (6232) = 270 
 
 Therefore the 
 
 B.t.u. 
 Net loss = 270 154= 116 
 
 and the 
 
 B.t.u. 
 Higher heat value of H per pound from 62 F. to 
 
 62 F. water =62, 100 116= 61,984 
 
 This value will be taken as 62,000 
 
 209. Lower Heat Values. The lower heat value of H is 
 sometimes assumed as the amount of heat that would be given 
 up to the calorimeter if the steam product of combustion were 
 to remain gaseous and behave in the same manner as the products 
 of combustion of the other chemical elements of the fuel (and 
 the inert nitrogen when the O for combustion is supplied by air), 
 instead of condensing at 212 F. and 14.7 pounds per square inch 
 pressure. 
 
 Under this assumption the lower heat value is less than the 
 higher by an amount which is the difference between (a) the heat 
 given up by the steam while changing from steam at 212 F. to 
 water at whatever final temperature is taken (below 212 F. and 
 14.7 pounds per square inch pressure) and (b) the heat that would 
 be given up by an equal weight of (imaginary) gas while cooling 
 from 212 F. to the same assumed final temperature. 
 
 The amount of heat given up by a pound of steam in condensing 
 and cooling from 212 F. and atmospheric pressure (14.7 pounds 
 per square inch) to water at 32 F. is 1146.6 B.t.u. The amount 
 
COMBUSTION AND HEAT VALUES 307 
 
 of heat that would be given up by a pound of gas 'whose specific 
 heat is .24* while cooling from 2i2F. to 32 F. (through 
 i8oF.) is 180 X .24 = 43.2 B.t.u. The difference between 
 the heat actually given up by the pound of steam and that given 
 up by the same weight of the imaginary gas is 1146.6 43.2 = 
 1103.4 B.t.u. One pound of H produces 9 pounds of steam. 
 Therefore the difference between the high and low heat values 
 of one pound of H when the products of combustion are cooled to 
 32 F. at atmospheric pressure is 
 
 9 X 1103.4 = 9930 B.t.u. 
 
 When the pound of steam is condensed from 2 1 2 F. and 
 atmospheric pressure to water at 62 F., it gives up 30 B.t.u. 
 less of heat than when it is cooled to water at 32 F. The amount 
 of heat given up by a pound of steam when cooled from 212 F. 
 and atmospheric pressure to water at 62 F. is therefore 1146.6 - 
 30 = 1116.6 B.t.u. One pound of gas with a specific heat of 
 .24 (as has been assumed) gives up while cooling from 2i2F. 
 to 32 F. at constant pressure, heat to the amount of 
 
 1 (212 62) .24 = 150 X .24 = 36 B.t.u. 
 
 The difference between the amount of heat actually given up 
 by the pound of steam and that assumed as given up by the same 
 weight of imaginary gas is 1116.6 36 = 1080.6 B.t.u. There- 
 fore the difference between the high and low heat values of one 
 pound of H when the initial and final temperatures are 62 F. 
 and the pressure 14.7 pounds per square inch is 
 
 9 X 1080.6 = 9725 B.t.u. 
 
 * There is no way of determining what the specific heat of this imaginary 
 gas should be. Its value can only be assumed on what appears to be a reason- 
 able basis. The specific heat per pound of superheated steam increases 
 rapidly as the degree of superheat increases. If the specific heat of the imagi- 
 nary gas is assumed to have the same values and follow the same law down to 
 32 F., its mean specific heat per pound would be in the neighborhood of .24 
 probably. If the imaginary gas were taken as CO 2 the specific heat would 
 be about .22 on the weight basis. Fortunately only a very small relative per- 
 centage change is caused in determining the lower heat value by using differ- 
 ent values, within reasonable limits, of this assumed specific heat. 
 
308 THE GAS ENGINE 
 
 The amount of heat deduction per pound of steam (or water) 
 in the products of combustion which must be made from the 
 higher heat value to obtain the lower value, appears in both of 
 the above cases. It is shown as 1103.4 B.t.u. in the first case and 
 as 1080.6 B.t.u. in the second. 
 
 In applying the correction to the calorimeter-determined heat 
 values of a mixed gas to obtain its lower heat value, it is often 
 convenient to use the correction factor for each pound of steam 
 (or water) in the products of combustion. The values just given 
 can be used for this method of correcting, each in its proper 
 place. 
 
 A summary of the above, together with the lower heat values 
 of H, under the two conditions stated, is given below. 
 
 Deduction per pound of H to be made from the higher heat 
 value of i pound of H to obtain the lower heat value: 
 
 B.t.u. 
 
 For initial and final temperatures of 32 F 993 
 
 For initial and final temperatures of 62 F 97 2 5 
 
 By making the appropriate deductions, whose values have just 
 been given, from the higher heat values of H, the lower heat values 
 are obtained. Thus : 
 
 B.t.u. 
 
 Lower heat value of one pound of H burned from 
 32 F. and 14.7 pounds per square inch and 
 62 F. and the products cooled to water at 
 32 F. is 62,100 9930 = $2,17 
 
 Lower heat value of one pound of H burned from 
 62 F. and 14.7 pounds per square inch and 
 the products cooled to water at 62 F. is 
 62,000-9725= 52,275 
 
 Deduction per pound of steam (or water) in the products of 
 combustion, to be taken from the higher heat value of a fuel to 
 obtain the lower heat value: 
 
 B.t.u. 
 
 For initial and final temperatures of 32 F 1103 
 
 For initial and final temperatures of 62 F 1080 
 
COMBUSTION AND HEAT VALUES 
 
 309 
 
 Whenever H, either free or combined, is prese/it in the gas- 
 motor fuel to any considerable proportion of the total mixture that 
 enters the combustion space of the motor, the difference between 
 the higher and the lower heat values of the fuel is great enough to 
 need consideration in accurate economy and efficiency determi- 
 nations. 
 
 TABLE IV. 
 
 Combustion of Carbon. 
 
 Volumes at 62 F. and 14.7 pounds per square inch. 
 
 
 Heat 
 Value. 
 B.t.u. * 
 
 Air Required. 
 
 Products. 
 
 Lbs. 
 
 Cu. Ft. 
 
 Lbs. 
 
 Cu. Ft. 
 
 i Ib C to CO .... 
 
 4206 
 14650 
 
 5-76 
 11.52 
 
 75-8 
 I5I-7 
 
 6.76 
 12.52 
 
 91.7 
 I5I-7 
 
 i Ib C to CO2 
 
 
 TABLE V. 
 
 Heat Values of Gases. 
 
 32 Fahrenheit. Pound units. 
 
 Gas. 
 
 Air per 
 Lb. of 
 
 Perfect Mix- 
 
 tnt-0 "R 4- 11 
 
 Product per Lb. of 
 
 
 
 
 Gas for 
 
 LuTC" Jj.T.U. 
 
 per Lb. 
 
 gas. Lbs. 
 
 
 
 B.t.u. per Lb. 
 
 Perfect 
 
 
 
 
 Chem- 
 
 
 Mix- 
 
 
 
 Name. 
 
 ical 
 
 
 ture. 
 
 
 
 
 
 
 
 
 
 
 
 Form. 
 
 Higher. 
 
 Lower. 
 
 Lbs.* 
 
 Higher. 
 
 Lower. 
 
 C0 2 
 
 H 2 
 
 N 
 
 Hydrogen 
 
 H 2 
 
 62,100 
 
 ^2,170 
 
 34-6 
 
 1744 
 
 I46c 
 
 
 9OO 
 . ww 
 
 26.6 
 
 Carbon monox- 
 
 
 
 3*>* / w 
 
 O T 
 
 / T-T- 
 
 J -t v O 
 
 
 
 
 ide 
 
 CO 
 
 4,476 
 
 4476 
 
 2 4.6 
 
 I2Q4 
 
 I2Q4 
 
 i c;7 
 
 
 i 80 
 
 Methane or 
 
 
 T-JT- / " 
 
 >T~ / w 
 
 T- W 
 
 j. - l y- 1 
 
 j. - ' ;-| 
 
 L j / 
 
 
 j. . t->y 
 
 marsh gas . . . 
 
 CH 4 
 
 23,850 
 
 21,368 
 
 17-3 
 
 1303 
 
 Il67 
 
 2-75 
 
 2.25 
 
 13-3 
 
 Ethylene or ole- 
 
 
 
 
 
 
 
 
 
 
 fiant gas 
 
 C 2 H 4 
 
 2I,44O 
 
 20,022 
 
 14.83 
 
 1354 
 
 I26l 
 
 3* 
 
 If 
 
 II.4 
 
 Propylene 
 
 C 3 H 6 
 
 21,420 
 
 2O,O02 
 
 14.83 
 
 1353 
 
 1262 
 
 3* 
 
 If 
 
 il. 4 
 
 Benzol or ben- 
 
 
 
 
 
 
 
 
 
 
 zene vapor. . . 
 
 C 6 H 6 
 
 l8,450 
 
 17,686 
 
 13-31 
 
 I2QO 
 
 I2 3 6 
 
 3^ 
 
 A 
 
 10.25 
 
 * 4.326 Ibs. air per Ib. of Oxygen. 
 
 Air = 76.9% H and 23.1% O by weight. 
 
3 io 
 
 THE GAS ENGINE 
 
 TABLE VI. 
 
 Heat Values of Gases. 
 
 Cubic foot units at 32 F. and 14.7 Ibs. per sq. in. pressure. 
 
 Gas. 
 
 Air per 
 Cu. Ft. of 
 Gas for 
 Perfect 
 Mixture. 
 Cu. Ft,* 
 
 Perfect Mix- 
 ture. 
 B.t.u. per 
 Cu. Ft. 
 
 Name. 
 
 Chem- 
 ical 
 Form. 
 
 B.t.u. per 
 Cu. Ft. 
 
 Higher. 
 
 Lower. 
 
 Higher. 
 
 Lower. 
 
 Hydrogen 
 
 H 2 
 CO 
 CH 4 
 C 2 H 4 
 C 3 H 6 
 C 6 H 6 
 
 348 
 
 349 
 1065 
 
 1673 
 2509 
 4010 
 
 292 
 349 
 955 
 1562 
 
 2343 
 3845 
 
 2 -39 
 2-39 
 9-57 
 14-35 
 21.52 
 
 35.87 
 
 102.6 
 
 103.0 
 101 .4 
 109.0 
 111.4 
 108.7 
 
 86. 
 103. 
 90. 
 101.7 
 104.0 
 104.3 
 
 Carbon monoxide 
 
 Methane or marsh gas 
 
 Ethylene or olefiant gas 
 
 Propylene 
 
 Benzol or benzene vapor 
 
 * This is the amount of air required for a perfect mixture. An excess of 
 air is generally used in practice. 
 
 4.78 cu. ft. air for one cu. ft. Oxygen. 
 
 TABLE 
 
 Heat Values 
 
 Cubic Foot units at 62 F. and 
 
 VII. 
 of Gases. 
 
 14.7 Ibs. per sq. in. pressure, 
 
 Gas. 
 
 
 Perfect Mix- 
 
 
 Air per 
 
 ture. 
 
 
 
 
 Cu. Ft. of 
 
 B.t.u. per 
 
 
 
 B.t.u. 
 
 Gas for 
 
 Cu Ft 
 
 Na TTIP 
 
 Chemical 
 
 per Cu. Ft. 
 
 Perfect 
 Mixture j 
 
 
 
 Form. 
 
 
 
 Cu. Ft. 
 
 
 
 
 
 Higher. 
 
 Lower. 
 
 
 Higher. 
 
 Lower. 
 
 Hydrogen . ... 
 
 Ho 
 
 328 
 
 27<J 
 
 2. 3Q 
 
 06 6 
 
 81 
 
 Carbon monoxide 
 
 CO 
 
 32Q 
 
 32Q 
 
 2 . 2O 
 
 07- o 
 
 07. 
 
 Methane or marsh gas 
 
 CH4 
 
 1003 
 
 9OO 
 
 9- 57 
 
 QC . C 
 
 85. 
 
 Ethylene or olefiant gas 
 
 C 2 H 4 
 
 1^77 
 
 1472 
 
 14. 1$ 
 
 IO2 7 
 
 06 
 
 Propylene 
 
 C 3 H 6 
 
 2364 
 
 2205 
 
 21.5* 
 
 105.0 
 
 98. 
 
 Benzol or benzene vapor 
 
 C 6 H 6 
 
 3779 
 
 3624 
 
 35,- 87 
 
 102.5 
 
 98.3 
 
COMBUSTION AND HEAT VALUES 
 
 When no H is present in the fuel, there is only^one heat value 
 for the fuel between any stated initial and final temperatures. 
 (This of course does not refer to different numerical values 
 expressed in different units of measure.) 
 
 Table V gives the heat values per pound at 32 F. and 14.7 
 pounds per square inch pressure, of the gases with which com- 
 bustion motors are most concerned; also the heat values of a 
 perfect combustible mixture of each gas with air. 
 
 Table VI gives the heat value of gases per cubic foot at 32 F. 
 and 14.7 pounds per square inch pressure. 
 
 Table VII gives the heat values of gases per cubic foot at 62 F. 
 and 14.7 pounds per square inch pressure. 
 
 TABLE VIII. PRODUCER GAS * 
 Determination of Heat Value from Chemical Analysis. 
 
 62 F. and 14.7 Ibs. per sq. in pressure. 
 
 Components. 
 
 Chemical 
 Form. 
 
 Percentage 
 by Volume. 
 
 B.t.u. per 
 Cu. Ft. 
 Lower. 
 
 B.t.u. for 
 Each Com- 
 ponent. 
 Lower. 
 
 
 
 P- 
 
 h. 
 
 pXh 
 
 100 
 
 Hydrogen 
 
 H 2 
 
 Q. 7 
 
 27<J 
 
 26 67 
 
 Carbon monoxide 
 
 CO 
 
 16.4 
 
 32Q 
 
 C7 Q6 
 
 Methane 
 
 CH 4 
 
 <;.6 
 
 QOO 
 
 ^O.4.O 
 
 Carbon dioxide 
 
 CO2 
 
 8 2 
 
 
 
 Oxvcren 
 
 C9 
 
 I O 
 
 
 
 Nitrogen 
 
 N? 
 
 CQ I 
 
 
 
 
 
 
 
 
 Total 
 
 
 IOO.O 
 
 
 131 .03 
 
 
 
 
 
 
 * Gas made in a pressure producer from black lignite of the following 
 percentage composition by weight: H = 6.07; C = 57.46; O = 28.78; N = 1.15; 
 S = .55; Ash = 5.99; Total = 100. 
 
 Lower heat value of gas at 62 F. and 14.7 Ibs. per sq. in. = 131 
 B.t.u. per cu. ft. 
 
312 
 
 THE GAS ENGINE 
 
 The volumetric composition of a sample of producer gas, as 
 determined by chemical analysis, is given in Table VIII ; also the 
 tabulated results of computations for the lower heat value of the 
 gas per cubic foot at 62 F. and 14.7 pounds per square inch 
 pressure. 
 
 TABLE IX. PRODUCER GAS. 
 
 Density, Air Required, and Heat Values of Gas and Mixture 
 Determined from Chemical Analysis. 
 
 62 F. and 14.7 Ibs. per sq. in. pressure. 
 
 
 
 "8 
 ?a 
 
 * 1 
 
 ^3 
 
 || 
 
 aa 
 
 J 
 
 *! 
 
 i?g 
 
 Components. 
 
 Chem- 
 ical 
 Form. 
 
 Per Cent Volun 
 Components. 
 
 B.t.u. perCu. F 
 Component. ] 
 Value. 
 
 ? 
 
 C 
 
 if* 
 
 Weight of Each 
 ponent. Lbs. 
 Cu. Ft. of Gas 
 
 jii 
 
 Air for Each C 
 ponent in a Pe 
 Mixture. Cu. 
 
 P- 
 
 k. 
 
 pxh 
 
 P. 
 
 pXD 
 
 a. 
 
 aXp 
 
 IOO 
 
 IOO 
 
 IOO 
 
 Hydrogen 
 
 H 2 
 CO 
 
 24.8 
 
 275 
 329 
 
 23-37 
 81.59 
 
 .0736 
 
 .00045 
 .01825 
 
 2-39 
 2-39 
 
 .203 
 593 
 
 Carbon monoxide . 
 
 Methane 
 
 CH 4 
 
 S- 2 
 
 900 
 
 46.80 
 
 .0421 
 
 .00219 
 
 9-57 
 
 .498 
 
 Ethylene 
 
 C 2 H 4 
 
 0.40 
 
 1472 
 
 5-89 
 
 0735 
 
 . 00029 
 
 M-35 
 
 057 
 
 Carbon dioxide. . . . 
 Oxvcren 
 
 CO 2 
 2 
 
 N 2 
 
 5-6 
 0.40 
 
 55-i 
 
 
 
 .0841 
 .0738 
 
 .00647 
 .00034 
 
 04055 
 
 -4-873 
 
 .019 
 
 Nitrogen . . 
 
 
 
 Totals 
 
 1 00.0 
 
 B.t.u. = 157. 65 
 
 D e n , y =.c68 54 
 
 Air= 1.332 
 
 B.t.u. per cubic foot of gas = 157.65 lower value. 
 
 Air per cubic foot of gas for perfect mixture = .332 cubic foot. 
 
 B.t.u. per cubic foot of perfect mixture = I M' $ =67.5 lower value. 
 
 1 + 1.332 
 
 Density of gas =.0685 pound per cubic foot at 62 F. and 14.7 
 pounds per square inch. 
 
 Table IX gives the volumetric composition of another sample 
 of producer gas together with the computed density, air required, 
 and lower heat values of the gas and combustible mixture. 
 
COMBUSTION AND HEAT VALUES 
 
 313 
 
 Table X is similar to Table IX for an illuminating gas made 
 by distilling off the volatile parts of the coal in a retort. 
 
 TABLE X. RETORT ILLUMINATING GAS. 
 
 Density, Air Required, and Heat Values of Gas and Mixture. 
 Determined from Chemical Analysis. 
 
 62 F. and 14.7 Ibs. per sq. in. pressure. 
 
 
 
 | 
 
 1% 
 
 , <u 
 
 II 
 
 |* 
 
 Jlf. 
 
 !!* 
 
 p o *i 
 
 ||S 
 
 4) 
 
 
 
 o 4 
 
 3 
 
 d s 
 
 JS 
 
 %& 
 
 ^ ^ o 
 
 |5^ 
 
 
 Chem- 
 
 > g 
 
 G 
 
 8. o . 
 
 &3 
 
 
 
 "S 
 * *> 
 
 
 Jij 
 
 Components. 
 
 ical 
 
 O 
 
 Is 
 
 3 S ~ 
 
 +j 
 
 f s 
 
 5 g fe 
 
 &" 
 
 
 
 Form. 
 
 g 
 
 
 fll 
 
 S P 
 
 ? ^ r- 
 
 o3 *"* 
 
 n 
 
 
 
 
 
 
 D P, O 
 
 
 
 
 
 
 0. 
 
 ffl 
 
 
 
 Q 
 
 ^ 
 
 ^ 
 
 ^ 
 
 
 
 
 
 pXh 
 
 7) 
 
 pxD 
 
 
 aXp 
 
 
 
 A 
 
 
 100 
 
 
 100 
 
 
 IOO 
 
 Hydrogen 
 
 H 2 
 
 39-8 
 
 275 
 
 109.45 
 
 0053 
 
 .002 i i 
 
 2-39 
 
 95 1 
 
 Carbon monoxide . 
 
 CO 
 
 7.6 
 
 329 
 
 25.00 
 
 .0736 
 
 00559 
 
 2-39 
 
 .184 
 
 Methane 
 
 CH 4 
 
 36.2 
 
 900 
 
 325.80 
 
 .O42I 
 
 .01524 
 
 9-57 
 
 3-464 
 
 Propylene * 
 
 C 3 H 6 
 
 3-8 
 
 22O5 
 
 83-79 
 
 .IIO4 
 
 .00420 
 
 21.52 
 
 .818 
 
 Benzol f 
 
 C 6 H 6 
 
 0.6 
 
 3624 
 
 21.74 
 
 .2048 
 
 .00123 
 
 35-87 
 
 .215 
 
 Oxygen 
 
 O 2 
 
 o 8 
 
 
 
 O84I 
 
 00068 
 
 4 873 
 
 038 
 
 Nitrogen 
 
 N 2 
 
 II. 2 
 
 
 
 .0 7 38 
 
 .00827 
 
 
 
 Totals 
 
 
 100. 
 
 B.t.u.= 
 
 -565-78 
 
 
 
 ,03^ 
 
 Air 
 
 = 5-594 
 
 * Heavy hydrocarbons taken as propylene. 
 t Light hydrocarbons taken as benzol. 
 
 B.t.u. per cubic foot of gas = 565.78 lower value. 
 
 Air per cubic foot of gas for perfect mixture = 5, 5 94 cubic feet. 
 
 B.t.u. per cubic foot of perfect mixture = * **'- = 85.8 lower value. 
 
 J + 5-594 
 
 Density of gas =.0373 pound per cubic foot at 62 F. and 14.7 
 pounds per square inch. 
 
314 THE GAS ENGINE 
 
 210. Illuminants, light hydrocarbons and heavy hydrocarbons. 
 
 - The illuminating property of a gas flame depends on the 
 presence of certain hydrocarbons known as the "illuminants" or 
 " heavy hydrocarbons." In their absence the flame has little or 
 no illuminating power. 
 
 In gas analysis the illuminating hydrocarbons are not generally 
 separately determined, but are either taken as a single group or 
 divided into two groups known as the "light hydrocarbons" and 
 the "heavy hydrocarbons." These light hydrocarbons are 
 soluble in alcohol, and the heavy hydrocarbons in either fuming 
 sulphuric acid or bromine. 
 
 When all the illuminants are determined as a group, they are 
 often considered as propylene (C 3 H e ). When divided into two 
 groups, the light hydrocarbons may be taken as benzol or benzene 
 (C 6 H 6 ) and the heavy hydrocarbons as propylene. 
 
 The illuminants are also sometimes all taken as ethylene 
 (olefiant gas, C 2 H 4 ). 
 
 211. Saturated and Unsaturated Hydrocarbons. The hydro- 
 carbons whose chemical compositions agree with the formula 
 C n H 2n+2 , of which CH 4 , C 2 H 6 , C 3 H 8 , C 4 H 10 are examples, are 
 called the "paraffins." They are also called "saturated hydro- 
 carbons." The carbon in them is completely saturated with 
 hydrogen, or at least more completely saturated than any of the 
 other known hydrocarbons. 
 
 The other hydrocarbons with which the combustion motor 
 and gas manufacture for it are concerned, are called the "un- 
 saturated hydrocarbons." They are the illuminants mentioned 
 in the preceding section. They conform to various chemical 
 formulas, some of which are given below. 
 
 The olefine group has the formula C n H 2n . Some of the com- 
 pounds are C 2 H 4 , C 3 H 6 , C 4 H 8 . 
 
 The acetylene group has the formula C n H 2n _ 2 . Acetylene gas 
 has the composition C 2 H 2 . 
 
 The benzols or benzenes (not the benzine from petroleum) are 
 represented by the general formula C n H 2n _ c . Of them benzene, 
 C 6 H 6 , is found in coal gas. 
 
 Naphthalene, of another group, has the composition C 10 H 8 . 
 
COMBUSTION AND HEAT VALUES 315 
 
 The tar of coal gas is composed of naphthalene jand other com- 
 pounds of a similar nature. 
 
 212. Physical Form of Hydrocarbons. At or near atmos- 
 pheric pressure the hydrocarbons with which this work is most 
 concerned have the following conditions as to being gas, liquid, or 
 solid. 
 
 Methane (marsh gas, CH ), ethylene (olefiant gas, C 2 H 4 ), 
 propylene, C 3 H e , ethane, C 2 H 6 , and acetylene, C 2 H 2 , all are per- 
 manent gases at atmospheric temperatures. 
 
 Propane, C 3 H 8 , is a gas above 1.4 F. 
 
 Butane, C 4 H 10 , is a gas above 34 F. 
 
 Benzole or benzene, C 6 H 6 (not the benzine from petroleum, 
 or the refined benzol which is used in the same manner as 
 gasoline in combustion motors), melts at 42 F. and boils at 
 177 F., above which temperature it is- a gas. Refined benzol 
 freezes at about 20 F. 
 
 Naphthalene, C 10 H 8 , melts at 175 F. and boils at 424 F. 
 
 The vapors of substances present but not gaseous under the 
 conditions existing are generally present in the gas with which 
 the substance is, or has been, in contact. This is similar to the 
 presence of water vapor in air at atmospheric temperatures. 
 
 213. Dissociation or Decomposition of Chemical Compounds. 
 - Experiments have shown that if steam is heated to a high 
 
 temperature part of it is separated into its elements H and O. 
 The proportion of the whole mass that is dissociated or " split 
 up" is greater the higher the temperature. As far as has been 
 determined and made public, the temperature at which dissocia- 
 tion of H 2 O begins is in the neighborhood of 1800 F. When the 
 temperature is lowered again, the elements H and O recombine 
 if they have not been acted on by other chemical elements. 
 
 Several of the chemical compounds of hydrogen and carbon 
 (hydrocarbons) that are contained in petroleum and its distillates 
 (kerosene, naphtha, gasoline, etc.) and in bituminous coals, are 
 decomposed or split up when heated to a temperature far lower 
 than that of combustion of the liquid or coal. The elements of 
 the hydrocarbons thus separated generally unite immediately in 
 different proportions from those in which they were combined 
 
316 THE GAS ENGINE 
 
 before heating, and thus form new hydrocarbons whose physical 
 and chemical properties are unlike those of the original compound. 
 
 Dissociation is the reverse of chemical combination, and the 
 heat required to cause the dissociation is the same in amount as 
 that which was liberated during the combination of the same 
 amount of elements to form the chemical compound. 
 
 214. Combustion Pressures and Temperatures. If the specific 
 heats of gases, or the total amount of heat in the gases, were 
 known for all temperatures between those of combustion and 
 atmospheric, then the theoretical temperature of the products of 
 combustion could be readily calculated. These heat properties 
 of the gases are not known, however, for the high temperatures 
 of combustion.* It is therefore impossible to calculate even 
 approximately on this basis the pressure that a combustible 
 mixture will produce when burned either in a vessel of fixed 
 volume or in one of variable volume, or otherwise. 
 
 The cooling effect of the walls of the cylinder or vessel in which 
 the gas is contained has much to do with lowering the pressure 
 below that which would be attained if there were interchange of 
 heat between the gas and the walls. The walls of a metal vessel 
 abstract heat with great rapidity from gases at as high tem- 
 peratures as those produced by the combustion of the fuels 
 used in gas-engine practice, when the walls are kept as cool as 
 they must be in the motor. 
 
 Investigations by different experimenters with combustible 
 mixtures of illuminating gas and air, exploded at atmospheric 
 pressure in cast-iron cylinders some 7 or 8 inches in diameter 
 and somewhat longer than the diameter, show, for proportions 
 of air and gas giving the higher pressures, that the pressure drops 
 
 * Recent investigations show that the specific heats of CO, CO 2 , and steam 
 all increase with rise of temperature. The results obtained by different 
 experimenters for CO and CO 2 are so far different at the higher temperatures 
 as to make it impossible to select approximately correct values. The specific 
 heat of steam has been determined by Prof. C. C. Thomas for temperatures 
 up to something more than 850 F. and 300 pounds per square inch pressure. 
 (Proceedings Amer. Soc. Mech. Engrs., December, 1907.) Neither this tem- 
 perature nor pressure is as high as in the combustion motor. The tem- 
 perature especially is far below that of combustion in the motor. 
 
COMBUSTION AND HEAT VALUES 317 
 
 from the maximum to about half the maximum jn one-fourth of 
 a second or less, and during a full second falls to about one-fifth 
 of the maximum, but as low as one-seventh of the maximum in 
 some cases. The maximum pressures of the mixtures giving 
 the higher values are attained in one-fifteenth to one-twentieth of 
 a second, as indicated by the recording apparatus. These 
 values make no allowance for the inertia lag of the moving parts 
 of the indicator. 
 
 With the higher temperatures and pressures that occur in the 
 combustion motor on account of compression before ignition, the 
 rate of heat absorption by the cylinder walls is much more rapid 
 during the early part of the stroke than later in the stroke, 
 except possibly in the case of a very hot motor cylinder. 
 
 215. Rate of Flame Propagation and Combustion. When 
 a quiescent mass of combustible gas and air mixture is ignited by 
 a spark, the flame propagates itself through the mixture by 
 spreading in a spherical wave, at least theoretically. The actual 
 propagation is something of this nature, at least. An appreciable 
 period of time in comparison with that required for one stroke 
 of the piston of a high-speed motor is required for the flame to 
 pass through the entire mass. The location of the igniting spark 
 in the mass of mixture therefore has to do with the time required 
 for complete inflammation of the charge. If the spark occurs in 
 a pocket leading off from the main combustion chamber, as is the 
 case in many gas motors, the charge will not be inflamed as 
 quickly as if the spark were in the center of the combustion 
 chamber. Again, if there is a pocket on each side of the com- 
 bustion chamber, the inflammation will be completed sooner by 
 making simultaneous sparks in the two pockets than by igniting 
 in only one pocket. With the two sparks the flame has only 
 about half as far to travel as with the one. 
 
 When the initial ignition of the charge is in a relatively small 
 reservoir connected to the main mass of the gas by a narrow 
 passage, a jet of flame is projected into the main body of the gas 
 and ignites a large portion quickly. The indicator card in such 
 a case shows a rapidly rising combustion line without any sign of 
 ignition before the completion of the compression stroke. The 
 
318 THE GAS ENGINE 
 
 ignition must be somewhat before the completion of compression, 
 however, in order to have the flame project into the main mass 
 before the piston has moved appreciably on the impulse stroke. 
 
 After inflammation, some time is required for the completion 
 of combustion. This is plainly noticeable in the burning of a 
 candle or a Bunsen flame. In the flame the period of uniting is 
 that during which the atoms travel from the bottom to the top 
 of the flame. 
 
 The rate of combustion is affected by variation of pressure and 
 of the proportions of the air and fuel within the range of com- 
 bustible mixtures. It is probable that the rate of combustion 
 also varies with the temperature, but this has not been conclu- 
 sively proved. 
 
 The combustion is more rapid the higher the pressure of the 
 mixture. 
 
 A perfect mixture burns more rapidly than one that is "lean" 
 or too "rich." A theoretically perfect mixture is one in which 
 there is just enough oxygen present to unite with the fuel in the 
 proportion to form the most stable compound. A practically 
 perfect mixture contains a slight excess of oxygen above the 
 amount for a theoretically perfect mixture. A lean mixture has 
 too little fuel and more oxygen than is necessary for complete 
 combustion. The same name is also applied to a mixture having 
 the proper proportions of fuel and oxygen but which is diluted 
 with inert gases such as those remaining in the combustion 
 chamber of a motor and mixing with the next charge. A rich 
 mixture has more fuel than is necessary for the proper propor- 
 tion relative to the oxygen present for complete combustion. 
 
 The "time of combustion" as herein used means the interval 
 between the ignition of the first part of the mixture and the 
 ceasing of combustion. It includes ignition, inflammation, and 
 combustion, more or less chemically complete, as the case may be. 
 
 216. Unusual Pressures of Combustion. Under certain 
 conditions the pressure produced by the combustion of a gas 
 and air mixture is higher than those ordinarily occurring. The 
 conditions conducive to such unusual pressure, so" far as they 
 seem to have been determined, are those in which the combustion 
 
COMBUSTION AND HEAT VALUES 319 
 
 of one portion of a mass of gas produces high pressure in an 
 unignited portion, and the latter then appears to suddenly ignite 
 and burn with a resulting high pressure. 
 
 The effect of pockets and contracted ducts has already been 
 mentioned in connection with indicator cards. In this relation 
 it may be pointed out that the cooling action of a small contracted 
 duct may prevent the passage of the propagating flame into a 
 pocket thus partly cut off from the main body of the gas till the 
 pressure has become so high that the mixture in the pocket 
 explodes violently. 
 
 There seem to be no conclusive proofs of the infrequent occur- 
 rence of combustion pressures enormously higher than the usual 
 values in gas-engine practice. For many years it was supposed 
 that these pressures did occur in the motor and were the chief 
 cause of broken parts, especially the cylinder. The writer has 
 searched for but never been able to find such a case. Internal 
 stresses due to heating seem to be more accountable for breakages 
 of this nature. 
 
 217. When an over-rich mixture of air and gasoline vapor is 
 ignited, all, or nearly all, of the hydrogen (of the hydrocarbons 
 of which the gasoline is composed) unites with the oxygen present, 
 thus not leaving a sufficient amount of O for all the carbon to 
 unite with. The carbon thus left appears as soot or smoke which, 
 in the case of a combustion motor, is discharged with the exhaust 
 gases, except such of it as adheres to the walls of the combustion 
 chamber, ports, and other parts with which it comes in contact. 
 
 The imperfect combustion is responsible for a loss of heat both 
 on account of the heat required for dissociating the hydrocarbon, 
 part of which is not burned, and on account of the failure of the 
 carbon to burn. 
 
 In the case of gaseous fuels, smoke may or may not appear, 
 according to the nature of the fuel, but in all cases the imperfect 
 combustion of course means loss of heat. A gas rich in illumi- 
 nants will give off smoke when the mixture is too rich. 
 
 Producer gas from bituminous coals is generally richer and 
 contains a greater proportion of illuminants just after a fresh lot 
 of fuel has been charged on than after there has been no fresh 
 
320 THE GAS ENGINE 
 
 fuel added for some time. This is on account of the distillation 
 of the volatile part of the fresh fuel soon after it is put into the 
 producer. 
 
 218. Moisture in Air and Gas. The moisture in air and gas 
 exists in the state of vapor when the quantity does not exceed the 
 limit that the air or gas will take up as vapor. When this limit 
 is reached, the air or gas is said to be saturated with water vapor. 
 
 In the case of fog in air (or gas) there is present more than 
 enough moisture to produce saturation, and the excess is in the 
 form of finely divided (atomized, in popular language) liquid 
 water. The same is true when dew is falling. This atomized 
 water may be called entrained water. 
 
 The weight of the water whose vapor will just saturate a given 
 volume of space varies with the tempera ture,_ but is not changed 
 by change of pressure or of the kind of gas present. The weight 
 of water vapor for just saturating a cubic foot of space at a given 
 temperature is the same whether the space contains air or gas, or 
 is a vacuum before the water vapor is added. If liquid water is 
 flowed into the vacuum it will vaporize very much more quickly 
 to saturate the space than if the "space" is filled with dry air or 
 dry gas at atmospheric pressure before the water is flowed in; 
 but the weight of the water that will finally vaporize is the same 
 in either case. As a concrete example, if something more than 
 14.79 grains of water are added to dry air, dry gas, or a vacuum 
 of one cubic foot enclosed volume, the space will be saturated at 
 90 F. by the vaporization of 14.79 grains of the water. The 
 water in excess of this amount will remain liquid. 
 
 The water vapor in a saturated space has an invariable pressure 
 for each temperature. The pressure of the water vapor is not 
 changed by the presence or absence of air, gas, or other vapors. 
 When the water vaporizes in the enclosed dry space, the pressure 
 against the enclosing walls is increased by the amount of the 
 vapor pressure for the corresponding temperature. The vapor 
 pressure for saturation at 90 degrees is .691 pound per square 
 inch. The pressure against the enclosing walls will be increased 
 by this amount on account of the vaporization of the water. If 
 the cubic foot of space is originally filled with dry air or dry gas 
 
COMBUSTION AND HEAT VALUES 321 
 
 at 14 pounds per square inch pressure, it will have, when saturated 
 with water vapor, a pressure of 14 + .691 = 14.691 pounds per 
 square inch at 90 F. 
 
 The relative volumes occupied by the dry air and water vapor 
 are proportional to their individual pressures. At 90 F. the ratio 
 of the volume of the water vapor to that of the dry air is .691 to 
 14, which corresponds to 4.7 per cent water vapor and 95.3 per 
 cent dry air. 
 
 Table XI gives data of the above nature for different tem- 
 peratures. The table shows that the proportion of water vapor 
 increases rapidly with increase of temperature. 
 
 If the vapor pressure is kept constant at (or below) the satura- 
 tion pressure, all of the liquid will vaporize. Heat must be 
 added to keep the temperature constant. Water boiling in the 
 open air is an example of this. In an enclosed space with an 
 opening for allowing the vapor to escape, the vapor or steam thus 
 ultimately occupies the entire volume of the space. 
 
 The extent of the effect of variation of moisture on the working 
 of a combustion motor can be seen by the aid of a concrete case. 
 A motor operating on gasoline is convenient to deal with. It will 
 be assumed that when the inlet closes the charge has the same 
 temperature in the motor as the air outside. 
 
 At 92 F. and 100 per cent humidity (complete saturation), 
 the moist air will be 95 per cent dry air and 5 per cent water vapor 
 by volume. At 92 F. and 50 per cent humidity (half saturation) 
 the volume of the vapor will be only half as great, as will be the 
 vapor pressure and weight of vapor per cubic foot. The air at 
 90 degrees and 50 per cent humidity will therefore be 97.5 per 
 cent dry air and 2.5 per cent water vapor. This is an increase of 
 about 2.6 per cent in the volume of dry air. The oxygen for 
 supporting combustion is increased in the same proportion. 
 The motor will therefore develop more power on the dry air than 
 on the saturated. A range of humidity as great as that stated, 
 or even greater, is not unusual, and fog gives greater moisture 
 than 100 per cent humidity. 
 
 The cooling 'of air or gas precipitates moisture if present in 
 sufficient quantity, as in the familiar example of dew. 
 
322 
 
 THE GAS ENGINE 
 
 TABLE XI.* 
 
 Moisture in Air, Gas, or Vacuum Completely Saturated With 
 Water Vapor at Different Temperatures. 
 
 Complete saturation corresponds to 100 per cent humidity. 
 
 Temperature. 
 
 Vapor Pressure. 
 
 Percentage by Volume 
 in a Saturated Mix- 
 ture at 14.7 Lbs. 
 
 Weight of Water 
 Vapor per Cubic 
 Foot 
 
 
 
 per Sq. In. 
 
 
 Deg. 
 
 Fahr. 
 
 Deg. 
 Cent. 
 
 Inches of 
 Mercury. 
 
 Pounds 
 per 
 Sq. In. 
 
 Water 
 Vapor. 
 
 Dry Gas. 
 
 Grains. 
 
 Pounds . 
 
 20 
 
 -28.9 
 
 .0126 
 
 .0062 
 
 .04 
 
 99.96 
 
 .166 
 
 . 000024 
 
 10 
 
 - 2 3-3 
 
 .0222 
 
 .0109 
 
 .07 
 
 99-93 
 
 .285 
 
 .000041 
 
 o 
 
 -I 7 .8 
 
 0383 
 
 .0188 
 
 13 
 
 99.87 
 
 .481 
 
 .000069 
 
 5 
 
 -15 
 
 .0491 
 
 .0241 
 
 .16 
 
 99.84 
 
 .610 
 
 .000087 
 
 IO 
 
 12.2 
 
 .0631 
 
 .0310 
 
 .21 
 
 99-79 
 
 .776 
 
 .0001 I i 
 
 15 
 
 - 9-4 
 
 .0810 
 
 .0398 
 
 .27 
 
 99-73 
 
 .986 
 
 .000141 
 
 20 
 
 - 6.7 
 
 . 1026 
 
 .0504 
 
 34 
 
 99.66 
 
 l- 2 35 
 
 .000176 
 
 25 
 
 - 3-9 
 
 .130 
 
 .0639 
 
 43 
 
 99-57 
 
 J-SS 1 
 
 .000221 
 
 30 
 
 i.i 
 
 .164 
 
 .0806 
 
 55 
 
 99-45 
 
 J-935 
 
 .000276 
 
 3 2 
 
 
 
 .180 
 
 .0884 
 
 .60 
 
 99.40 
 
 2.113 
 
 . OO0302 
 
 35 
 
 i-7 
 
 .203 
 
 .099 
 
 .62 
 
 99-38 
 
 2.366 
 
 000338 
 
 40 
 
 4-4 
 
 247 
 
 . 121 
 
 .82 
 
 99.28 
 
 2.849 
 
 . O00407 
 
 45 
 
 7.2 
 
 .298 
 
 .146 
 
 99 
 
 99.01 
 
 3-414 
 
 . 000488 
 
 5 
 
 10. 
 
 .360 
 
 .177 
 
 .20 
 
 98.80 
 
 4.076 
 
 .000582 
 
 5 2 
 
 ii . i 
 
 .387 
 
 . I9O 
 
 .29 
 
 98.71 
 
 4-372 
 
 .000625 
 
 54 
 
 12.2 
 
 .417 
 
 .205 
 
 .40 
 
 98.60 
 
 4.685 
 
 . 000669 
 
 56 
 
 13-3 
 
 .448 
 
 .220 
 
 5 
 
 98.50 
 
 5.016 
 
 .000717 
 
 58 
 
 14.4 
 
 .482 
 
 236 
 
 .61 
 
 98.39 
 
 5-37o 
 
 .000767 
 
 60 
 
 I 5 .6 
 
 5i7 
 
 254 
 
 73 
 
 98.27 
 
 5-745 
 
 . 00082 I 
 
 62 
 
 l6-7 
 
 555 
 
 2 73 
 
 .86 
 
 98.14 
 
 6. 142 
 
 .000877 
 
 64 
 
 I 7 .8 
 
 595 
 
 .292 
 
 99 
 
 98.01 
 
 6-563 
 
 . 000938 
 
 66 
 
 18.9 
 
 .638 
 
 314 
 
 2.14 
 
 97.86 
 
 7.009 
 
 .OOIOOI 
 
 68 
 
 20.0 
 
 .684 
 
 336 
 
 2.28 
 
 97.72 
 
 7.480 
 
 .001069 
 
 70 
 
 21 . I 
 
 73 2 
 
 359 
 
 2.44 
 
 97-56 
 
 7.980 
 
 .001140 
 
 * Inches of mercury for vapor pressure and grains weight of water vapor 
 taken from Psychrometric Tables of the United States Weather Bureau. 
 Other items computed by the author. 
 
COMBUSTION AND HEAT VALUES 
 
 323 
 
 TABLE XI.* CONTINUED. 
 
 Moisture in Air, Gas, or Vacuum Completely Saturated With 
 Water Vapor at Different Temperatures. 
 
 Complete saturation corresponds to 100 per cent humidity. 
 
 Temperature. 
 
 Vapor Pressure. 
 
 Percentage by Volume 
 in a Saturated Mix- 
 ture at 14.7 Lbs. 
 per Sq. In.- 
 
 Weight of Water 
 Vapor per Cubic 
 Foot. 
 
 Deg. 
 Fahr. 
 
 Deg. 
 Cent. 
 
 Inches of 
 Mercury. 
 
 Pounds 
 per 
 Sq. In. 
 
 Water 
 Vapor. 
 
 Dry Gas. 
 
 Grains. 
 
 Pounds. 
 
 7 2 
 74 
 7 6 
 
 22.2 
 
 23-3 
 24.4 
 
 .783 
 .838 
 .896 
 
 .384 
 .412 
 .440 
 
 2.61 
 
 2-79 
 2.99 
 
 97-39 
 97.21 
 97.01 
 
 8.508 
 9.066 
 9.655 
 
 .001215 
 .001295 
 .001379 
 
 g 
 
 82 
 
 25.6 
 26.7 
 
 27.8 
 
 957 
 i. 022 
 1.091 
 
 47 
 .502 
 
 .536 
 
 3-20 
 
 3-42 
 3-65 
 
 96.80 
 96.58 
 96.35 
 
 10.277 
 10.934 
 II .626 
 
 .001468 
 .001562 
 .001661 
 
 84 
 86 
 
 88 
 
 28.9 
 30.0 
 31-1 
 
 1.163 
 1.241 
 1.322 
 
 .p 
 .610 
 .650 
 
 3-89 
 4.15 
 4.42 
 
 96. II 
 95-85 
 95-58 
 
 12.356 
 13.127 
 
 13-937 
 
 .001765 
 .001875 
 .001991 
 
 90 
 92 
 94 
 
 32.2 
 
 33-3 
 
 34.4 
 
 1.408 
 1.499 
 1-595 
 
 .691 
 .736 
 .784 
 
 4.70 
 5.00 
 5-33 
 
 95-3 
 95.00 
 94.67 
 
 14.790 
 15-689 
 16.634 
 
 .002113 
 .002241 
 .002376 
 
 96 
 98 
 
 IOO 
 
 35.6 
 
 3 6 -7 
 37-8 
 
 1.696 
 1.803 
 1.916 
 
 833 
 .887 
 .942 
 
 5.67 
 
 6.03 
 
 6.41 
 
 94-33 
 93-97 
 93-59 
 
 17. 626 
 18.671 
 19. 766 
 
 .002518 
 .002667 
 .002824 
 
 102 
 104 
 
 106 
 
 38.9 
 40.0 
 41.1 
 
 2-035 
 2.160 
 2.292 
 
 I. 00 
 
 1.061 
 1.126 
 
 6.81 
 
 7 % 22 
 
 7.67 
 
 93-19 
 92.72 
 
 92.33 
 
 20.917 
 
 22. 125 
 23.392 
 
 . 002988 
 .003161 
 .00334! 
 
 108 
 no 
 
 210 
 
 42.2 
 43-3 
 
 08. Q 
 
 2-431 
 2.576 
 
 28.7=; 
 
 1.194 
 i. 264 
 
 14. II 
 
 8.12 
 
 8.60 
 
 06.00 
 
 91-87 
 91.40 
 
 4.00 
 
 24.720 
 26. 112 
 
 003531 
 .003730 
 
 * Inches of mercury for vapor pressure and grains weight of water vapor 
 taken from Psychrometric Tables of the United States Weather Bureau. 
 Other items computed by the author. 
 
324 THE GAS ENGINE 
 
 A cubic foot of saturated air at 32 F. contains but 13.5 per 
 cent as much moisture by weight as a cubic foot at 92 F. and the 
 volume occupied by the vapor is but 12 per cent of that at 92 F. 
 A cubic foot of saturated air at 92 F. when cooled to 32 degrees 
 contains only 11.5 per cent as much water vapor by weight as 
 at 92 F. 
 
 Compressing saturated air or gas at constant temperature 
 reduces the weight of water vapor in it by condensation. For 
 the vapor pressure remains constant and the weight of vapor in 
 the reduced space is proportional to the volume of the space; 
 but compressing air or permanent gas does not decrease its 
 weight, therefore the weight proportion of water vapor is decreased 
 by compression. 
 
 Sudden expansion of saturated compressed air or gas cools it 
 so that some of the water vapor is condensed and may be pre- 
 cipitated. 
 
 Producer gas is, on account of cooling while being washed with 
 water, saturated with water vapor when it leaves the scrubber. 
 It may also carry entrained liquid water. In warm weather the 
 amount of moisture may be enough to affect the power of the 
 motor sufficiently to deserve attention. 
 
 Saturated gas at 92 F. and 14.7 pounds per square inch has 
 only 95 per cent of the heating capacity of dry gas at the same 
 temperature and pressure, dealing with volumes. 
 
 A saturated combustible mixture at 92 F. and 14.7 pounds 
 per square inch also has 95 per cent of the heating value per cubic 
 foot that the dry mixture has. The pressure of combustion is 
 reduced by the water vapor both on 'account of the reduction of 
 the heat value and the higher specific heat of water vapor or steam. 
 Water in suspension requires heat to vaporize it, which is lost in 
 gas-engine practice. 
 
 The moisture can be largely removed by compressing and 
 cooling the gas and then allowing it to expand suddenly. Cen- 
 trifugal motion after compression will remove water of conden- 
 sation. 
 
 219. Gas Analyses Relative to Moisture. Published reports 
 of gas analyses seldom make any statement regarding moisture. 
 
COMBUSTION AND HEAT VALUES 325 
 
 Computed heat values based on chemical analyse* which do not 
 take moisture into account give higher heat values for the gas 
 than the actual values. 
 
 Humidity of gas, or moisture not exceeding the saturation 
 point, can be determined by the wet- and dry-bulb thermometer 
 apparatus in common use by the Weather Bureau. Entrained 
 moisture can be measured by absorption methods. 
 
CHAPTER XVIII. 
 
 FUELS AND GAS MAKING. 
 
 220. General. The commercial form in which fuel is 
 obtainable, its cost, and the convenience with which it can be 
 used in the internal-combustion motor are the chief items in the 
 consideration of the selection of the type of motor and in deter- 
 mining the kind of fuel. 
 
 The fuels either found on the market or resulting as by-products 
 of industrial processes, with which the combustion motor is 
 mostly concerned, and the general methods of utilizing them, are : 
 
 Coal. 
 
 Lignite. 
 
 Peat. 
 
 Wood. 
 
 Charcoal 
 
 Crude petroleum. 
 Heavy distillates of 
 petroleum. 
 
 Kerosene. 
 
 Naphtha. 
 Gasoline. 
 Alcohol. 
 Benzol. 
 
 Natural gas. 
 Illuminating gas. 
 Fuel gas. 
 Blast-furnace gas. 
 Coke-oven gas. 
 
 Converted into gas in a gas producer 
 before using. Washing and puri- 
 fying the gas are generally advis- 
 able. 
 
 Injected into the motor cylinder or 
 transformed into permanent gas 
 by the application of heat. 
 
 /Injected into the motor cylinder or 
 I vaporized in a heated carbureter. 
 
 Vaporized in a carbureter. 
 
 Used as received, except that clean- 
 ing or washing is necessary for 
 the by-product gases of the blast 
 furnace and coke oven. 
 
 * The recently invented process of making alcohol from peat by Professor 
 Lagerheim and Mr. Frestadius seems to open up great possibilities in this 
 
 326 
 
FUELS AND GAS MAKING 327 
 
 The solid fuels are transformed, more or less completely, into 
 permanent combustible gases before using in tne motor. The 
 cheaper soft coals can be utilized in this manner about as well as 
 the more expensive grades. The lignites can also be transformed 
 into satisfactory power gas with practically the same ease as 
 bituminous coal. Even peat can be dealt with in the same 
 manner. Wood, refuse, straw, bagasse, and other vegetable 
 matter not too wet can also be used. Anthracite coal is more 
 easily converted into fuel gas than any other fuel. 
 
 In the transformation of solid fuel into power gas it is desir- 
 able, especially in power plants of small and moderate capacities, 
 to convert all of the fuel part of the solid combustible into per- 
 manent gas, and thus avoid the formation of any by-products. 
 In a large plant, by-products can generally be disposed of to 
 advantage, but not usually in those of small power capacity. 
 
 In general there are in common use two types of producers 
 for converting solid fuel into permanent gas for power purposes. 
 The distinguishing features are that in one type pressure pro- 
 duced by auxiliary apparatus is used to force air, or steam, or 
 both together, through the bed of solid fuel; and in the other the 
 air and water are drawn through by the suction of the motor 
 itself, or of an auxiliary "exhauster." In the pressure producer 
 the gas is made at a more or less uniform rate while the producer 
 is operating, and the gas is stored in tanks, generally of small 
 capacity, from which it is drawn to meet the varying needs of 
 the motor. In the suction producer plant without auxiliary 
 exhauster there is no storage of gas. The gas is generated at 
 the rate that the motor demands it, stroke by stroke. When the 
 motor stops, the generation of gas stops with it. 
 
 In the methods especially applied to making power gas from 
 
 field on account of the small cost at which the alcohol can be produced and 
 the fact that all necessary materials for the process, except sulphuric acid 
 exist in some of the immense peat swamps of the United States. See Engineer- 
 ing Magazine, August, 1908. 
 
 The improved method of recovering sulphuric acid during the reduction 
 of copper ore etc., recently adopted by the Ducktown Copper Company of 
 Ducktown, Tennessee, makes possible the use of sulphuric acid on a com- 
 mercial basis for the production of alcohol from peat. 
 
328 
 
 THE GAS ENGINE 
 
 FIG. 114. 
 
FUELS AND GAS MAKING 329 
 
 FIG. 114. 
 
 Continuous Updraught Gas Producer for Bituminous Coal with Automatic Feed. 
 Air-and- Water Gas Process. Pressure or Suction Draught. R. D. Wood & 
 Co., Philadelphia, Pa. 
 
 The fuel is charged on from the small hopper at the top with conical bottom. The 
 vertical shaft of the automatic feed passes through the central part of the hopper 
 and has a worm-wheel at the top for power driving by means of the intermesh- 
 ing worm. The fuel-distributing device is attached to the bottom of the vertical 
 shaft and is so shaped as to distribute the fuel evenly over the fuel bed. 
 
 The blast enters at the bottom through the central pipe and passes out from under 
 the small hood into the ash and then up into the fuel. The blast is caused either 
 by a steam jet or a mechanical blower. In either case steam enters with the air. 
 
 The ash bed is supported on a revolving table which can be rotated by means of 
 the hand crank, pinion and spur gear outside of the ash pit, and the small bevel 
 gear that meshes with the large bevel gear on the under side of the table. The 
 rods projecting from the outside into the ash just above the revolving table are 
 for scraping the ash from the table as it revolves; they are adjustable as to the 
 distance they extend into the ash. 
 
 The gas passes out through the side flue near the top of the gasification chamber. 
 The ash pit is tightly closed while the blast is on. 
 
 Small holes for observing and poking the fuel are provided at the top and sides. 
 
 This producer is practically the same as that used in the tests at St. Louis by the 
 U. S. Geological Survey, operated as a pressure producer. One of these tests 
 was run 562 hours continuously. See Chap. XXL 
 
330 
 
 THE GAS ENGINE 
 
 FIG. 114a. 
 
FUELS AND GAS MAKING 331 
 
 FIG. 114a. 
 
 Continuous Updraught Pressure Producer for Bituminous Coal, with Automatic 
 
 Feed and Water-sealed Ash Pit. Either Pressure or Suction Draught. 
 
 R. D. Wood & Co., Philadelphia, Pa. 
 
 This is much the same as the producer shown in Fig. 114 except the water seal at 
 the bottom. This method of closing the ash pit allows the removal "of ashes 
 while the blast is on, and thus the continuous operation of the producer for an 
 indefinite period without cutting off the blast. 
 
 The pipe for carrying the steam to the jet that produces the blast is shown at the 
 lower left-hand side. 
 
 A producer of this general type, without the automatic feed, is in use at the works 
 of the American Locomotive Co., Richmond, Va. A test of the gas power plant 
 at these works is reported in the Proc. Amer. Inst. Elec. Engrs., July, 1908. 
 
332 THE GAS ENGINE 
 
 solid fuel, the process is either one of burning the fuel with so 
 small a supply of air that only incomplete combustion takes place 
 with the production of combustible gases, or one in which water 
 vapor or steam is brought into contact with the hot fuel and the 
 fuel and steam act mutually on each other so that fuel gas is 
 formed. Both methods are often applied simultaneously to the 
 fuel. The only solid matter left in any appreciable quantity is 
 the ash. In some methods practically all of the combustible of 
 the fuel is converted into permanent gas. In others an appreciable 
 quantity of semi-liquid matter is formed by the condensation of 
 some of the gas. This is abstracted from the gas. Some of the 
 methods of making gas for illuminating purposes differ radically 
 from those for power gas. 
 
 The heat values per cubic foot of the combustible mixtures 
 formed by mixing different fuels with air are different. For 
 example, a mixture of blast-furnace gas and air has only about 
 60 per cent of the amount of heat available per cubic foot that a 
 mixture of gasoline vapor and air has, both mixtures being 
 proportioned for perfect combustion. And a mixture of illuminat- 
 ing gas and air has about 90 per cent of the heat value of the 
 gasoline vapor and air mixture, both mixtures taken at the same 
 volume, temperature, and pressure. 
 
 The power that a motor will develop is in a measure proportional 
 to the lower heat value per cubic foot of the combustible mixture 
 used (but not to either the lower or the higher heat value of the 
 fuel gas). If the compression pressure is kept the same for all 
 mixtures, then the power capacity of the motor on the different 
 mixtures is nearly proportional to the heat value of the mixture. 
 
 A motor that is to develop a certain amount of power at a given 
 speed of piston travel must be considerably larger in cylinder 
 capacity for blast-furnace gas than for natural gas, illuminating 
 gas, gasoline, naphtha, kerosene, or fuel oil. The compression 
 pressure can be carried considerably higher for blast-furnace gas 
 than for the other fuels just mentioned. Since the higher com- 
 pression pressure increases the efficiency of heat transformation 
 into mechanical energy, the ratio of the cylinder capacity of the 
 motor using blast-furnace gas to that of the one using natural 
 
FUELS AND GAS MAKING 333 
 
 gas is therefore somewhat less for the same power developed than 
 the ratio of the lower heat value of the natural gas and air mixture 
 to that of the blast-furnace gas and air mixture. 
 
 221. Retort Gas by Distillation of Bituminous Coal. Coal 
 Gas. Bituminous coal (soft coal) is placed in a retort which is 
 then tightly closed except where a pipe is connected for carrying 
 off the gas. An external fire heats the retort to incandescence 
 and drives off from one-fourth to one-third of the coal as gas, 
 according to the grade of coal used. The gas is passed through 
 a water-cooled pipe, where some .of the unstable gas is condensed 
 to the form of tar. The remaining gases are still further cooled, 
 washed with water, and chemically treated to remove the remain- 
 ing tar vapors, ammonia vapor, carbon dioxide, sulphur, and any 
 other impurity that may be present. If the coal is of a certain 
 composition, the resulting gas is suitable for illuminating pur- 
 poses when burned as an open flame. But when there are not 
 enough illuminants present in the distilled gas it is enriched with 
 illuminants, generally from petroleum or petroleum products. 
 Two-thirds to three-quarters of the weight of the coal remains 
 in the retort as coke, composed of carbon and earthy matter. 
 The principal by-products of the retort process are coke (gas 
 coke), tar, and ammonia. These and the other by-products are 
 converted into almost innumerable other substances by suitable 
 processes. 
 
 The composition of retort-distilled gas varies with both the kind 
 of coal used and the temperature (or rapidity) of distillation. 
 
 Assuming, for a very rough method of comparison between 
 the heat value of the gas distilled and of the coal, that each pound 
 of coal gives 5 cubic feet of gas having a heat value of 600 B.t.u. 
 per cubic foot before enriching, which is a high value, and that 
 the heat value of the coal is 15,000 B.t.u. per pound, it will be 
 seen that only twenty, per cent of the heat of the coal appears in 
 the gas. 
 
 While retort gas made as just described burns with entire 
 satisfaction in the combustion motor, it is too expensive for use 
 in large motors on account of the method of production and the 
 high grade of coal that must be used. This refers especially to 
 
334 THE GAS ENGINE 
 
 power plants of medium size where recovery of by-products is 
 not commercially advantageous. 
 
 The other extreme point of view is that a coal-distilling plant 
 may be operated with gas as a by-product, and the other sub- 
 stances produced as the valuable commodities sought. This 
 condition is realized in the manufacture of coke and the use of 
 the excess gas for combustion motors. 
 
 222. Air Gas by Burning Solid Fuel with Insufficient Air. 
 While this method is not used for producing gas for power pur- 
 poses, it will be described because various combinations of it and 
 the water-gas process (to be described later) constitute practically 
 all the commercial methods of manufacturing power gas (and also 
 fuel gas for furnaces). 
 
 The air-gas process is similar, in a way, to incomplete com- 
 bustion in a furnace whose function is to produce heat. This is 
 such a condition as exists, to some extent, when the fuel bed is 
 carried too thick or too deep for heating purposes. In such a 
 case the products of combustion, especially when anthracite coal 
 or coke is used as a fuel, contain a large percentage of carbon 
 monoxide, CO. 
 
 In the simpler forms of air-gas producers in which air enters 
 the fuel bed at the bottom and passes off at the top, there is 
 generally a considerable thickness of ash between the burning 
 fuel and the grate bars or other device for supporting the charge. 
 
 When the air comes into contact with the incandescent carbon, 
 the O of the air and some of the carbon unite to form either CO 
 or CO 2 . Just what the chemical reactions are has never been 
 determined. The resulting gases that pass from the fuel contain 
 both CO and CO 2 under ordinary conditions of. operating a 
 producer. Since the CO 2 is not combustible, the process is 
 carried out so as to cause the C to combine with the O as CO as 
 far as possible. 
 
 Most of the heat liberated by the burning of the carbon goes 
 to raise the temperature of the products of combustion and is 
 carried from the producer by the gas. A small proportion goes 
 to raise the temperature of the fuel, to vaporize the .volatile part, 
 and to balance the heat lost by radiation, etc. 
 
FUELS AND GAS MAKING 335 
 
 There is generally an appreciable amount pf water vapor 
 (moisture) in the air. The coal contains water, or hydrogen 
 and oxygen in the proportion to form water, sometimes to the 
 extent of several per cent of its weight. But even with the cooling 
 effects of atmospheric and fuel moisture, radiation and excess of 
 air, and other causes, the temperature of the gases passing from 
 the fuel is high. The complete combustion of some of the carbon 
 which occurs keeps the temperature higher than that of incom- 
 plete combustion alone. 
 
 When bituminous coal is used in the gas producer, the volatile 
 parts are first distilled off in much the same manner as in the 
 retort process, so far as the action on the coal is concerned. The 
 coke thus formed is then burned by the oxygen of the air. Tar 
 and ammonia products, etc., are formed as in the retort process, 
 unless the generator is especially constructed to dissociate the 
 unstable gases and allow recombination of their elements into 
 stable gases. This latter action will be taken up in connection 
 with the processes more suitable for making power gas. 
 
 A large amount of heat is carried from the fuel by the gases in 
 the air-gas process. This heat can be utilized to some extent for 
 heating the air going to the producer, but still the gas will be very 
 hot even after the heat for this purpose has been abstracted. 
 
 The gas must be washed and otherwise purified before going 
 to the motor. This has the effect of cooling it. The major part of 
 the heat that is carried from the producer by the gas is thus lost 
 unless unusual means are provided to utilize it for purposes other 
 than for the motor. On account of this great waste of heat the 
 simple air-gas process is not economical for generating power gas. 
 
 The theoretical value of all the heat that can be obtained by 
 chemically accurate carrying out of the air-gas process when the 
 fuel is assumed to be pure carbon, can be determined as follows : 
 
 Bt.u. 
 
 Heat value of i pound C burned to CO 2 14650 
 
 Heat liberated by burning i pound C to CO 4206 
 
 Heat in 2j pounds CO produced = 146504206 = 10444 
 
 Ratio of heat value of total ) _ 10444 _ _ 
 
 CO produced to that in the C \ ~ 14650 ~' 713 ~ ?I ' 3 PC 
 
336 THE GAS ENGINE 
 
 This is the theoretical limit of the efficiency of the air-gas proc- 
 ess with pure dry carbon and no moisture in the atmosphere. 
 
 The theoretical efficiency of the air-gas process with coals con- 
 taining volatile matter will in general be somewhat different from 
 the value just obtained. Moisture in the fuel and the atmosphere 
 also modifies this efficiency. 
 
 223. Water Gas in General. Water gas is made by bringing 
 steam into contact with highly heated fuel. The steam is decom- 
 posed into its elements, H and O, and the O then combines with 
 the C of the fuel to form carbonic oxide, CO. The hydrogen 
 escapes as free H. This is when the only combustible in the fuel 
 is C and the process is theoretically perfect. In practice some 
 carbonic acid, CO 2 , is also formed. There are also other com- 
 bustible substances generally present in the gas formed on account 
 of impurities and hydrocarbons in the fuel. 
 
 The chemical equations representing the theoretical process of 
 water-gas formation from the carbon constituent of the fuel are: 
 
 2 VOl. 2 VOl. 2 VOl. 
 
 2 H 2 O + C 2 = 2 CO + 2 H 2 , 
 
 H 2 + C = CO + 2 H 
 
 1 8 12 28 2 Weight proportions. 
 Pounds 1 f -V- i 
 
 The last two equations show that the volumes of CO and H 
 produced are equal to each other, and that the total volume of the 
 combustible gas produced is twice that of the steam used, dealing 
 with equal temperatures and pressures. 
 
 The equations also show that the weight of the CO produced is 
 fourteen times that of the H that is set free. 
 
 There are two distinct methods of manufacturing water gas. 
 One is known as the continuous or retort process, and the other 
 is an intermittent process. The retort process is but little used. 
 The intermittent process finds a large field of application. 
 
 There is also a process of alternately making air gas and 
 water gas in a producer. It is only a slight modification of the 
 intermittent water-gas process, and finds broad application. 
 
FUELS AND GAS MAKING 337 
 
 Water gas does not give an illuminating flame, s^ince it contains 
 little or none of the heavy hydrocarbons which, as has been stated, 
 are the illuminating constituents of a gas. Water gas can be 
 made illuminating by carbureting by the addition of heavy 
 hydrocarbons. This is generally done by adding to it the 
 heavy hydrocarbon gases of petroleum, obtained, in some cases 
 at least, by decomposing the heavy distillates of petroleum 
 by heat. Carburation increases the cost of production per 
 cubic foot. 
 
 The three processes which have been mentioned in this section 
 will be separately discussed later. 
 
 224. Producer Gas by Combined Air-Gas and Water-Gas 
 Processes. The gas intended especially for power (and heating) 
 purposes is practically all made by processes that are combinations 
 of the air-gas and water-gas processes. There are several different 
 ways in common use for combining these two processes. One 
 method is to admit both air and steam or water vapor simulta- 
 neously and continuously to the fuel, thus producing continuously 
 a mixture of air- and water-gas. Another method is to burn the 
 fuel with air for a while till the fuel bed has become highly 
 incandescent, and then to cut off the air and pass steam or water 
 vapor into the hot mass, alternating the periods of air and water 
 admission so as to keep the temperature of the fuel within a range 
 suitable for satisfactorily carrying on the manufacture of the gas. 
 Air gas is made during the period of " bio wing" while the air 
 alone is admitted, and water gas only during the "run" while 
 steam alone is admitted. 
 
 The name "producer gas" is quite generally understood to 
 mean the mixture of air- and water-gas made by any of these 
 processes, but it is also applied sometimes to air gas alone and 
 sometimes to water gas alone. 
 
 225. Suction Producer for Anthracite Coal or Coke. Suction 
 Due to Intake Stroke of Motor Piston. Power gas for motors 
 up to three hundred horsepower can be made satisfactorily 
 by drawing air and steam or water vapor by suction through a 
 deep bed of anthracite coal. The more common form of suction 
 producer is a vertical cylinder of metal lined with fire-brick. The 
 
338 THE GAS ENGINE 
 
 fuel is supported by a grate or some other form of rest that partly 
 fills the lower part of the enclosed space, leaving a circular opening 
 near the wall through which the ash can drop out. The producer 
 is closed air tight except the openings for admitting air and steam 
 and another for the escape of the gas. In the usual forms the 
 suction of the. motor draws air and steam or water vapor through 
 the fuel, where the chemical changes of dissociating the steam 
 and burning the coal take place. In one type of suction producer 
 plant the gases pass from the producer to an economizer and 
 there give up part of their heat for warming the air that is going 
 to the producer, and also to vaporize the water to supply the 
 requisite amount of steam to the producer. The gases then pass 
 into the bottom of a scrubber for cleaning the gas by washing it 
 with water. The scrubber is generally a vertical cylinder filled 
 with rather finely broken coke, or having a large number of wood 
 slats, etc., over and through which water trickles from the top 
 to the bottom. The gas is freed more or less completely from 
 soot, dust, and some of the other impurities while passing upward 
 through the scrubber. From the top of the scrubber the gas goes 
 into a purifier, dry cleaner, or moisture separator, in which it 
 passes through some finely divided substance such as sawdust 
 or fine wood shavings, for final cleaning and freeing from mois- 
 ture and solid particles. From the purifier the gas goes directly 
 to the motor cylinder in the required amount during the charg- 
 ing stroke of the piston. A small drum is sometimes placed 
 between the motor and the purifier. It provides a mass of 
 gas for expanding and flowing into the motor during the suc- 
 tion stroke, thus maintaining a more steady flow through the 
 producer and its accessories and offering less resistance to the 
 suction of the motor than when no such drum is used. 
 
 The air going to the producer passes through the economizer, 
 where it receives heat from the producer gas before entering the 
 ash pit or air space of the producer. The steam from the vapor- 
 izer also passes into the sealed ash pit, from which the mingled 
 air and steam are drawn into the fuel. 
 
 The function of the economizer is to utilize as much as possible 
 the heat carried from the producer by the gases. 
 
FUELS AND GAS MAKING 339 
 
 The exhaust from the motor is sometimes utilized for pre- 
 heating the air that goes to the producer. 
 
 The theoretical changes that take place in the producer are the 
 incomplete combustion of a part of the carbon of the fuel by the 
 oxygen of the air to form CO; the decomposition of the steam 
 into its elements H and O; and the combination of the O thus 
 liberated with the remainder of the carbon to form more CO. 
 
 The decomposition of the steam absorbs sensible heat in a 
 larger amount than is liberated by the combustion of its O with 
 the C to form CO. Heat is therefore required for the water-gas 
 part of the process of gas generation. 
 
 The air-burned part of the fuel supplies the heat necessary 
 for the water-gas part of the process, and also the heat carried 
 off by the gas, lost by radiation, required to heat the fuel, etc. 
 
 Since, in the suction producer direct connected to the motor 
 as described, the demand for gas varies with the amount of power 
 that the motor must furnish at any moment, and because the 
 temperature of the fuel bed should remain nearly constant, it is 
 evident that the rate of supplying steam to the fuel bed must be 
 variable in somewhat the same proportion as the rate at which 
 gas is generated. Automatic regulation of the amount of steam 
 supplied therefore becomes a necessity for the direct-connected 
 suction gas producer. 
 
 The construction of the gas-generating plant just described is 
 such as to secure automatic control of the steam supply. In it 
 as long as the gas is generated at a certain rate the steam will be 
 formed at a practically constant corresponding rate, for if the 
 temperature of the fire and the gas passing from it should rise, 
 the gas will carry more heat to the water in the vaporizer and the 
 rate of steaming will consequently be increased. The increased 
 amount of steam will in turn cool the fire down to the proper 
 temperature. A reverse action occurs when the fire tends to 
 get too cool. 
 
 Again, when the load on the motor increases, more air is drawn 
 into the generator than before. The increased amount of air 
 increases the temperature of the fire slightly, and the greater 
 amount of slightly warmer gas carries more heat over to the 
 
340 THE GAS ENGINE 
 
 vaporizer, so that more steam is formed to keep both the tem- 
 perature and the composition of the gas constant. The reverse 
 occurs when the load on the motor decreases. 
 
 In some designs of suction producers the vaporizer is part of the 
 producer. The water space in such cases is generally over the 
 top and around the upper part of the generator. 
 
 The steam is sometimes admitted to the fuel some distance 
 above the bottom of the fire. This is done to secure the most 
 complete consumption of the fuel by allowing only air to come 
 in contact with it at the lowest zone of combustion and thus to 
 maintain a high temperature while the last of each piece of fuel 
 is consumed. The fact that considerable coal passes unburned 
 into the ash in some types of producers makes it essential to 
 consider some means, as that just mentioned, for the prevention 
 of fuel waste in this manner. 
 
 For starting the fire in a suction producer of the size and type 
 under discussion, or for bringing up the fire after it has been idle 
 for some time, as over night or a holiday, an air blower is necessary. 
 When the blower is hand operated, which is generally the case for 
 the small plants, the plant is entirely independent of any other 
 source of power. While blowing up the fire a vent is opened 
 between the producer and scrubber to allow the gas to pass off. 
 The vent is generally between the economizer and scrubber. 
 When the vent is thus located, the economizer is heated during 
 the period of blowing up the fire. 
 
 226. Theoretical Case of Gas Producer. A convenient 
 method of following out the operations of a gas producer operating 
 continuously in the manner of the suction type described in the 
 preceding section, is to assume that there is neither loss of heat 
 by radiation, carrying off by the gas, etc., nor gain of heat from 
 energy supplied by any exterior source. Such a case cannot 
 possibly exist, of course. But this manner of simplifying the 
 operations of the process warrants such assumptions in order 
 to secure ready means for following out the essential parts of 
 the process. 
 
 It will therefore be assumed, for the purpose jast stated, that 
 the producer delivers gas at the same temperature and pressure 
 
FUELS AND GAS MAKING 341 
 
 as that of the atmosphere, that there is no heat loss by radiation, 
 and that the gain of heat on account of the energy consumed in 
 creating a draft through the apparatus is just balanced by the 
 loss in the heat carried off by the ash. 
 
 Under such assumptions the total heat value of the gas pro- 
 duced is the same as that of the fuel consumed. The com- 
 putations which are given below deal with the gas produced 
 from a pound of carbon burned by the combined air- and water- 
 gas process. 
 
 227. Computations for Theoretical Gas Producer. Supplies 
 received and products delivered at 62 F. and 14.7 pounds per 
 square inch pressure. 
 
 Higher heat values used. 
 
 Heat liberated by i Ib. C burned to CO 2 4206 B.t.u. 
 
 Heat required to vaporize and decompose i Ib. 
 
 water = 61,984 4-9= 6887 B.t.u. 
 
 Heat liberated by burning two-thirds Ib. C to 
 CO with the eight-ninths pound O liberated 
 by the decomposition of i Ib. of water = X 
 
 4206 = 2804 B.t.u. 
 
 (See section 223 and table of heat values.) 
 
 Heat to be supplied by air-burned C for main- 
 taining a uniform temperature of the fuel while 
 i Ib. water is decomposed and its O united 
 with C to form CO = 6887 - 2804 = 4083 B.t.u. 
 
 Water per pound of air-burned C that will 
 
 keep the temperature of the fuel bed 
 
 -, 4083 
 
 uniform 
 
 4206 
 
 = 1.0301 Ibs. 
 
 Carbon burned by O from above amount of 
 water = 1.0301 X = 6867 Ib. 
 
 Total C burned for each pound of air-burned C i .6867 Ibs. 
 
 Water dissociated and resulting O com-] _ 
 bined with C per Ib. of C burned. 
 
 Percentage of air-burned C = I0 X I = ... .59.29 per cent. 
 
 1.6867 
 
 Percentage of water-burned C= I0 X ' 686 7 = 40.71 percent. 
 
 1.6867 
 
 :om-| = _ L .o 3 oi_ = 
 [. j i + .6867 
 
342 THE GAS ENGINE 
 
 For the air -burned part oj 1 pound carbon. 
 
 Pounds Cubic Feet 
 
 Air-burned part of 1 Ib. C ................... .593 ..... 
 
 Air for burning .593 Ib. C = .593 X 5.76 = . . . 3.415 44.8 
 
 CO formed by air burning = 2\ X .5928= .,U 1.383 18.83 
 
 (1 Ib. C forms i\ Ibs. CO.) 
 
 N from air burning = 3.415 X .7688 .......... 2.625 35.51 
 
 Total products from air-burned part of 1 Ib. C 4.008 54-34 
 Total heat value of air gas from air-burned part 
 
 of 1 Ib. carbon = 1.383 X 4476 = ...... ' ........... 6190 B.t.u. 
 
 B.t.u. per cubic foot of air eras = " = ............. TI A B.t.u. 
 
 For the water -burned part of 1 pound carbon. 
 
 Pounds Cubic Feet 
 
 Water-burned part of 1 Ib. C .................. 4071 ..... 
 
 Water used for burning .4071 Ib. C ............ 6107 .^TTT^ 
 
 CO formed by water burning = 2^ X .4071 = .9500 12.93* 
 
 Hsetfree = ^2= ......................... 0679 12.85* 
 
 9 
 
 Total product from water-burned part of 1 Ib. C = i .0179 25.78 
 Heat value of CO from water-burned part of 
 
 1 Ib. C = .95 X 4476 = .......................... 4252 B.t.u. 
 
 Higher heat value of H from) ^6107 x 6 ^ = ^ fi t u 
 
 water-burned part of 1 Ib. CJ 9 
 
 Total higher heat value of water gas from water-burned 
 
 part of 1 Ib. C = 4252 + 4206 = ................ 8458 B.t.u. 
 
 O . -Q 
 
 B.t.u. (higher) per cubic foot of water gas = = 328 B.t.u. 
 
 25 .78 
 
 * According to the volumetric relations in the chemical equation for water- 
 gas formation, the volume of H = volume of CO. This result is not obtained 
 in the computations, partly at least on account of using the approximate 
 atomic weights in the application of the equations in connection with tabular 
 values that are based on the accurate atomic weights. The atomic weight of 
 H is taken as 1 in the computations, while its accurately determined and 
 accepted value is 1.008. 
 
FUELS AND GAS MAKING 
 
 343 
 
 For burning 1 pound carbon to CO by the combined air- and 
 water-gas process; theoretical case of 100 per cent efficiency. 
 
 PRODUCTS. 
 
 
 Weight of 
 
 Volume Each 
 
 Heat Value of 
 Each Product 
 
 Perce 
 
 ntage. 
 
 
 Each Product. 
 Lbs. 
 
 Product. 
 Cu. Ft. 
 
 B.t.u. 
 Higher. 
 
 By Weight. 
 
 By Volume. 
 
 CO 
 
 2 . T.T.T. 
 
 3I-76 
 
 10,444 
 
 46.42 
 
 30- 64 
 
 H 
 N 
 
 .068 
 2 . 62? 
 
 12.85 
 35.51 
 
 4,206 
 
 ?-35 
 
 (52.23 
 
 16.04 
 
 44. 72 
 
 
 
 
 
 
 
 Totals . . 
 
 5.020 
 
 80.12 
 
 14,650 
 
 IOO.OO 
 
 IOO.OO 
 
 Air used in producer per Ib. of carbon = 3.45 Ibs. = 44.8 cubic feet. 
 Water used in producer per Ib. of carbon = .6107 Ib. 
 
 Higher heat value of gas produced = I4 ' ^ =183 B.t.u. per cubic 
 
 80.12 
 
 foot. 
 
 Specific heat of gas produced = .288 B.t.u. per Ib. at constant pressure. 
 
 Air per cubic foot of gas for perfect combustible mixture (.3964 + 
 .1614) 2.39 = .5578 X 2.39 = 1.33 cubic feet. 
 
 B.t.u. per cubic foot perfect mixture = - =78.4 B.t.u. 
 
 The total heat carried in by each pound of carbon is 14,650 
 B.t.u., which is the same as is returned in the combustible gas 
 under the theoretical conditions assumed. 
 
 The results obtained above can be checked by comparing 
 (a) the product of the heat liberated by the formation of 1 pound 
 of CO multiplied by the pounds of CO formed with (b) the 
 product of the heat absorbed per pound of H liberated multiplied 
 by the pounds of H liberated. The two products should be equal 
 for the 100 per cent efficiency assumed. The same reasoning is 
 true for cubic foot units (or any other units). 
 
 The amounts of heat liberated or absorbed per unit of product 
 are given below for 62 F. and 14.7 pounds per square inch pres- 
 sure absolute. 
 
344 THE GAS ENGINE 
 
 Heat liberated during the combination of: 
 
 C and O to form 1 cu. ft. CO = 132.5 B.t.u. per cu. ft. CO. 
 
 C and O to form 1 cu. ft. CO 2 = 462. B.t.u. per cu. ft. CO 2 . 
 
 C and O to form 1 Ib. CO = 1803 B.t.u. per Ib. CO. 
 
 C and O to form 1 Ib. CO 2 = 3995 B.t.u. per Ib. CO 2 . 
 
 Heat absorbed during the dissociation of: 
 
 H 2 O to liberate 1 cu. ft. H = 328 B.t.u. per cu. ft. H. 
 H 2 O to liberate 1 Ib. H = 61,984 B.t.u. per Ib. H. 
 
 The amounts of CO and H resulting from the gasification as 
 assumed above are 39.64 cubic feet CO and 16.04 cubic feet H. 
 By multiplying these amounts by their respective heat factors, 
 just given, the results are: 
 
 I 3 2 -5 X 3 J -76 = 4208 B.t.u. 
 328 X 12.85 = 4214 B.t.u. 
 
 which is as near an agreement of values as can be expected with 
 the use of round numbers for the heat values and the other errors 
 due to approximate values. 
 
 Using pound units in a similar manner, the results are: 
 
 1803 X 2.333 = 4206 B.t.u. 
 61,984 X .0679 = 4208 B.t.u. 
 
 The percentage composition can be used in a similar manner, 
 the percentage of each constituent of the gas being considered as 
 cubic feet in 100 cubic feet, or as pounds in 100 pounds of the gas. 
 
 If the C were burned to CO 2 in a theoretical case similar to 
 that just considered when there are no hydrocarbons in the gas, 
 the relative amounts of CO 2 and H for 100 per cent efficiency of 
 gas production are obtained from the following equations: 
 
 For cubic foot units, 
 
 328 H = 462 CO 2 ; 
 for pound units, 
 
 61,984 H = 3995 C0 2 , 
 
 in which the numerical quantities are the higher heat values of 
 the gases. 
 
FUELS AND GAS MAKING 
 
 345 
 
 The composition of suction producer gas from fuel that has 
 only C as the combustible can be determined from these equations 
 for the theoretical assumed case, as is done below. 
 
 Since each pound of H in the gas represents 8 pounds of O 
 from the decomposed water, and each pound of O combines 
 with twelve-thirty-seconds of a pound of C to form CO 2 (CO 2 = 12 
 parts C and 32 parts O by weight), therefore 
 
 For each pound of H in the gas produced there are 8 X Jf = 
 3 pounds C water-burned to CO 2 . 
 
 Heat liberated in burning 3 Ibs. C to CO 2 X 145650 =4390 B.t.u. 
 Heat to be supplied by air-burned C for each Ib. of 
 
 H in the gas produced = 61,984 43,95 = 18,034 B.t.u. 
 
 Pounds of air-burned C = l8 ' 34 = 1.231 Ibs. C 
 
 14,650 
 
 Total C burned per Ib. of H in the gas = 3 + 1.231 =4.231 Ibs. C 
 Nitrogen carried in with air for air-burning 1.231 
 
 Ibs. C = 1.231 X8.86 = 10.9 Ibs. N 
 
 Lbs. CO 2 from 4.231 Ibs. C = 4.231 X 3 = .... 15.515 Ibs. CO 2 
 
 Composition of Gas when C is Burned to C0 2 by the 
 Combined Air- and Water-Gas Processes. 
 
 Theoretical case of 100 per cent efficiency. 
 
 
 Weights. 
 
 Volumes. 
 
 Percentage 
 
 Percentage 
 
 
 
 
 by Weight. 
 
 by Volume. 
 
 fc:: 
 
 N 
 
 I5-5I4 
 
 I. 000 
 
 10.906 
 
 134.2 
 189.4 
 147.6 
 
 56.58 
 3.65 
 39-77 
 
 28.48 
 40.20 
 3I-3 2 
 
 Totals 
 
 27.320 
 
 471-2 
 
 100.00 
 
 100 . 00 
 
 The weights and volumes per Ib. of C burned can be obtained by 
 dividing by 4.231. 
 
 Pounds of gas produced per Ib. of C = 2 ?-3 2 =6.46 Ibs. gas. 
 
 4.231 
 
 Cu. ft. of gas produced per Ib. of C 
 
 4.231 
 
 111.4 cu. ft. gas. 
 
 Hydrogen produced per Ib. of C = 9 ' 4 = 44.7 cu. ft. H. 
 
 4.231 
 
346 THE GAS ENGINE 
 
 Heat value of H liberated per Ib. of C. burned = 44.7 X 328 = 
 14,650 B.t.u. about. 
 
 Higher heat value of gas for 40.2 per cent H, which is the only com- 
 bustible, = .402 X 328 = 131.8 B.t.u. per cu. ft. 
 
 Specific heat of gas produced = .345 B.t.u. per Ib. at constant pressure. 
 
 Air per cu. ft. of gas for perfect mixture = .402 X 2.39 = .96 cu. ft. 
 
 B.t.u. per cu. ft. of perfect mixture = I * 1 ' =67 B.t.u. higher. 
 
 i + .96 
 
 A comparison of the above two cases shows that both the gas 
 produced and the perfect mixture have higher heating values per 
 cubic foot when the carbon is burned to CO than when it is 
 burned to CO 2 . There is a smaller quantity of gas in the former 
 case, however, so that the total heat values of the gas produced 
 from a given amount of carbon are the same in both cases. 
 
 When both CO and CO 2 are formed in and carried from the 
 producer, the equations for the heat balance in the theoretical 
 case of ico per cent efficiency have the forms: 
 
 For cubic foot units, 
 
 328 H = 132.500 + 462 CO 2 ; 
 
 for pound units, 
 
 61,984 H = 1803 CO + 3995 C0 2 , 
 
 in which the numerical coefficients are heat values at 62 F. and 
 14.7 pounds per square inch absolute pressure. 
 
 The accuracy of the above equations depends on the correct- 
 ness of the heat values used. The ones here adopted seem to 
 have been determined with great care. 
 
 If when numerical substitutions and computations are made 
 for these equations the left-hand member in either is greater 
 than the right-hand member, it is an indication that the pro- 
 ducer is absorbing more heat for the decomposition of water than 
 is being generated by the combustion of carbon in the producer. 
 Such a condition can exist temporarily in a producer that does 
 not receive heat or energy from outside sources, but must be 
 paid for with leaner gas during a consecutive period of operation. 
 
 The above equations are not applicable when hydrocarbons 
 are present in the fuel or in the gas produced. 
 
FUELS AND GAS MAKING 347 
 
 228. Comparative Heat Losses for Burning C to CO or to C0 2 
 in the Air-and- Water- Gas Process When the Gas Leaves the 
 Producer at a High Temperature. It was shown in the pre- 
 ceding section that when C is burned to CO in the producer 
 there are theoretically 5.026 pounds of gas, whose specific heat 
 is .288 B.t.u. per pound, generated per pound of C burned to CO; 
 and that when the C is burned to CO 2 in the producer there are 
 6.46 pounds of gas, having a specific heat of .345 B.t.u. per pound, 
 generated per pound of C burned to CO 2 . 
 
 The heat required for raising the temperature of the gas i F. 
 in each case is : 
 
 For 1 pound C burned to CO, 
 
 5.026 X .288 = 1.446 B.t.u., 
 and for 1 pound C burned to CO 2 
 
 6.46 X .345 = 2.225 B.t.u. 
 
 The ratio of the two amounts of heat, 
 
 2.225 
 
 -, = 1-54, 
 1.446 
 
 shows that when in the air-and-water gas process the gas leaves 
 the producer at a higher temperature than that of the air, water, 
 and fuel used, 54 per cent more heat is carried from the producer 
 by the gas when the C is burned to CO 2 than when it is burned 
 to CO. This numerical value applies only to the theoretical case 
 of the preceding section, and also assumes that the specific 
 heats of the gases produced by the two methods of burning 
 retain the same ratio through all temperatures up to that at which 
 the gas leaves the producer. The latter assumption is probably 
 true in a measure. 
 
 The heat thus carried out from the producer is mostly lost 
 during the cooling of the gas by the usual methods. It is 
 therefore desirable to have a minimum of CO 2 in the gas. 
 
 229. Fuels for Continuously Operated Suction Producers. - 
 Since the continuously operated updraught suction producer can- 
 not be opened above the combustion zone for stoking or other- 
 
348 THE GAS ENGINE 
 
 wise breaking up the fuel, on account of air being drawn in 
 through such an opening, it is necessary to use a fuel that does not 
 cake or adhere to the walls of the combustion space. This means 
 that the fuel must be practically free from volatile hydrocarbons. 
 Mechanical stoking or stirring devices that enter above the com- 
 bustion zone are subject to detrimental leaks. 
 
 Hard coal (anthracite) and coke are therefore the only fuels 
 that are adapted to the continuously operated suction producer 
 direct connected to the motor after the manner that has been 
 described. 
 
 230. Pressure Gas Producers for Continuous Operation. - 
 The general form of this class of producer is much the same as 
 that of the continuous suction producer. The draught through 
 the producer and its accessory apparatus is caused generally by 
 either a steam jet blower that forces both steam and air into the 
 tightly sealed bottom of the producer or by a mechanical blower 
 which forces the air in while steam is brought in separately. In 
 the latter case the steam may be generated, at least in part, in a 
 vaporizer heated by the gases escaping from the producer. The 
 steam is sometimes taken from an entirely detached steam- 
 generating plant. 
 
 The gas passes, in the more usual construction, from the 
 producer successively through a vaporizer, an economizer for 
 heating the air going to the producer, a scrubber, a purifier, and 
 thence to a storage tank. A tar extractor is sometimes placed 
 between the scrubber and the purifier, and tar drips are suitably 
 located. There is generally one between the economizer and 
 the scrubber, with drainage from both. Water seals are used, 
 through which the gas passes on its way to storage, but cannot 
 return. The seals act as check valves. 
 
 The fuel can be stoked through openings above the combustion 
 zone by temporarily reducing the blast that forces the air through 
 the producer. This can be done without checking the operation 
 of the motor, since the storage tank will supply gas during a 
 short stoking interval. 
 
 The charging apparatus is made so that fresh, fuel can be 
 charged on at any time during the operation of the producer. 
 
FUELS AND GAS MAKING 349 
 
 A pair of small doors or gates, placed in series after the manner 
 of those in an air lock, are used for charging the fuel when it is 
 done by hand. Mechanical chargers have suitable provisions 
 enabling them to be used at any time. 
 
 Caking coals, as well as any other kinds, can be used in the 
 pressure producer. The convenience with which stoking can be 
 done by hand to break up caked coal makes it entirely practicable 
 to use those which cake to the highest extent. Mechanical 
 stokers or stirrers driven from above the combustion space for 
 continuously stirring the fuel are used to some extent. Leak- 
 age and rapid deterioration by the heat are serious features to be 
 dealt with in the use of a mechanical stoker of this class. 
 
 Various methods of sealing the ash pit find application. Water 
 is very commonly used for the seal. Mechanical sealing is also 
 extensively used. 
 
 When fuel containing volatile hydrocarbons is used, the 
 volatile part is distilled off and passes out with the other con- 
 stituents of the gas. Unless care is taken to have the producer 
 of a suitable form, and to operate it properly, a large portion of 
 the volatile gas will be of such a nature as to condense at or above 
 atmospheric temperature and pressure, that is, during the 
 cleaning and cooling of the gas. But if the producer has ample 
 and properly formed space above the fuel bed and the temperature 
 is kept high, part of the hydrocarbons that are distilled off from 
 the fuel as condensable gases (at atmospheric temperatures and 
 pressures) will be dissociated and their elements will recombine 
 in gases that are permanent under the ordinary conditions of 
 utilization. There are objections to keeping the temperature of 
 the fuel bed very high. Some of these objections are on account 
 of the increased loss of heat carried away by the gases, and 
 increased fusing and clinkering of the fusible part of the ash. 
 
 The government tests at St. Louis, of bituminous coals and 
 lignites in an up-draught, pressure producer for continuous 
 operation and of the general class just described, gave tar in 
 quantities approximately from 10 gallons to 23 gallons per ton of 
 coal used in the producer. The volatile matter in the coal varied 
 from about 21 to 40 per cent in the different varieties. The tar 
 
350 THE GAS ENGINE 
 
 from the bituminous coals was black, and that from some of the 
 lignites was of a brown color. 
 
 The tar is practically all waste in such cases, and is disagree- 
 able to have about the apparatus. 
 
 The aim of many producers using bituminous coals and lignites 
 is to completely break up the condensable hydrocarbons so that 
 they will form into others that are permanent gases. 
 
 Tar-burning apparatus for burning the tar under steam 
 boilers is used in connection with some gas power plants. The 
 method of burning is similar to that for oil fuels, the tar being 
 preheated to liquefy it. 
 
 231. Down-Draught Continuous Gas Producer. If coal is 
 charged or fed on at the top of the fuel bed and the draught 
 through it is downward from the top to the ash pit, then the 
 volatile gases distilled off from the green fuel will have to pass 
 down through the hot zone of combustion before escaping from 
 the producer. By this process the heat of the fuel bed dissociates 
 the condensable hydrocarbons and converts them into perma- 
 nent gases more completely than when the draught is upward 
 and the fuel fed on at the top. 
 
 In practice both air and steam are blown or drawn into the 
 upper part of the continuous producer and the gas taken out from 
 the bottom. Hand stoking for breaking up the caked fuel can 
 be done readily when the draught is produced by the suction 
 of an exhauster connected to the bottom of the producer for 
 drawing out the gas. 
 
 232. Under-Feed Continuous Gas Producer. Another method 
 of causing the distilled gases to pass through the hot bed of the 
 fuel before leaving the producer, is to feed the fuel in at the bottom 
 of the producer and have the draught through the fuel from the 
 bottom to the top. Numerous forms of this class of producer 
 have been used more or less extensively. The steam and air may 
 be either blown in or drawn in by suction, entering the producer 
 below the fuel bed, and the produced gases taken out at the top of 
 the producer. 
 
 233. Air and Carbon Dioxide Continuous Gas-Making Process. 
 It has been pointed out that when simple air gas is made there 
 
FUELS AND GAS MAKING 351 
 
 is a great loss of heat on account of the high temperature at which 
 gas leaves the producer, when the gas is cooled before using, unless 
 unusual means are adopted for utilizing its sensible heat. The 
 combined air- and water-gas processes that have been mentioned 
 prevent the loss of heat to so great an extent on account of keeping 
 down the temperature of the gas by utilizing trie surplus heat of 
 combustion to some extent for dissociating the water. 
 
 A method of keeping down the temperature of the fuel and of 
 the gas without the use of water or steam has recently, been 
 devised and put into operation. In this method exhaust gases 
 from the combustion motor are mixed with the air entering the 
 fuel bed in the producer. Since no water is used in the process, 
 the exhaust gas from the motor contains a large amount of CO 2 . 
 The CO 2 upon entering the fuel bed with the air is transformed 
 into CO in the producer by dissociation, during which part of the 
 O of the CO 2 takes up C from the fuel. The heat absorbed by 
 the dissociation of the CO 2 is greater than that liberated by the 
 recombination of the nascent O with C, so that the net result is a 
 cooling effect. The temperature of the fuel bed is kept up by the 
 air-burned part of the fuel.* 
 
 The plant was operated on both anthracite and bituminous 
 coal. The cooling effect of the water vapor from the motor 
 exhaust gas when hydrocarbons are present in considerable quan- 
 tity with the use of bituminous coal, is not taken up by the 
 inventor of the process in his description of it as referred to. 
 
 A fuel consumption of .7 of a pound of coal per horsepower 
 per hour when the plant operated continuously at full load for 
 24 hours a day for a considerable period is reported. When 
 operating ten hours a day and closing down Sundays with a load 
 factor of about two-thirds, the fuel per horsepower per hour 
 averaged 1J pounds of coal. 
 
 The motor was of the four-cycle, single-acting, three-cylinder 
 vertical type with a capacity of about 100 horsepower. 
 
 234. Combined Pressure and Suction Producer. By com- 
 bining both the pressure and the exhaust methods of operating 
 a producer, the pressure above the fuel can be maintained at or 
 * Proceedings Amer. Soc. Mech. Engrs., June, 1908, Vol. 30. 
 
352 
 
 THE GAS ENGINE 
 
FUELS AND GAS MAKING 
 
 353 
 
 | .g -g | -gj~g 
 I J" IP1 1 ^ 
 
 :1*^ Yj ** g 1 
 
 I ^&| 8 f r?'"iill* >8 riaL* I 
 
 S A 
 
 :a g, 
 
 I* I 
 
 II I 
 
 
 M 
 
 .2 .s ; ' ' S y "^ 
 S c g ^ 
 
 "cSSGoM ^'C^TJ'^^- 1 ^ " 4> C v 
 
 ^ 2^.s &?.fI-aAl^ ^': -S S 
 
 
 
 
354 THE GAS ENGINE 
 
 very slightly above atmospheric, so that stoke holes can be opened 
 into the gas space without appreciable escape of gas while the 
 gasifying process is under way. This combination is found in 
 the practical field. 
 
 235. Miscellaneous Types of Continuous Gas Producers for 
 Volatile Coals. There are numerous types of continuous-acting 
 gas producers intended to eliminate the tarry products from the 
 gas generated from coals containing volatile hydrocarbons. In 
 all of them the object is to heat the distilled gases to a high tem- 
 perature before they leave the producer. 
 
 A quite common method of doing this when the coal is charged 
 on at the top or upper part of the producer and the steam and air 
 enter from the bottom or from the ash pit, is to have the inner 
 orifice for the outlet of the gas from the producer below the top 
 level of the fuel. The distilled gases then fill such a portion of 
 the upper part of the chamber above the zone of combustion as 
 is not occupied by fuel, and pass down through the incandescent 
 fuel to the orifice of the outlet. The outlet is sometimes a water- 
 jacketed tube or pipe extending down into the central part of the 
 fuel bed and open at the lower end. In other cases there are a 
 number of ports in the wall of the producer below the top level 
 of the fuel. 
 
 Air and steam are sometimes admitted at both the top and 
 bottom of the fuel bed and the gas is carried out through ports 
 well below the top level of the fuel bed and of the combustion 
 zone. 
 
 Another method of highly heating the distilled gases is to have 
 a secondary fire in the producer so located that the gas from the 
 main fuel bed must pass through the secondary fire before 
 escaping from the producer. The secondary fire is naturally of 
 a non-volatile fuel, as coke or anthracite coal. 
 
 Still another method is to have a pipe or other down-take 
 passage lead from the. top of the gasification chamber to the ash 
 pit so that the distilled gases will be carried down and enter the 
 bottom of the fuel bed with the air and steam. Some means of 
 creating a down draught, as a steam blower, is necessary in the 
 down-take passage. 
 
FUELS AND GAS MAKING 355 
 
 Two producers are sometimes used in conjunction for the con- 
 tinuous production of gas from bituminous coal. The draught 
 is in either direction in the first one, but enters the fuel bed of the 
 other at the green or fresh fuel side, so that all the gases from the 
 first producer and all the distilled gases from the second must 
 pass through the hot combustion zone of the second producer. 
 Air and steam are added to the gas ,from the first producer before 
 it enters the fuel of the second one. 
 
 236. Intermittent Gas-Making Processes in General. Instead 
 of carrying out the combined operations of burning coal with air 
 and decomposing steam to burn more of the carbon and liberate 
 hydrogen, the two processes are carried on separately in some 
 cases. 
 
 For power gas purposes, a pair of producers operating in con- 
 junction are generally used for the intermittent process. This 
 is not always the method, however. 
 
 If in any of the forms of producers that have been briefly 
 discussed, air only is blown or drawn through the fuel at a rate 
 as great as compatible with gas-making processes, the body of the 
 fuel will soon become highly heated. Then, after it has attained 
 a sufficiently high temperature, if the air is cut off and steam 
 blown into the incandescent fuel, water gas will be formed as 
 long as the fuel remains hot enough to cause the necessary 
 chemical changes. When the fuel becomes as cool as allowable, 
 turning the air blast on again after cutting off the steam will 
 reheat the fuel, and so on. 
 
 The nature of the gases passing off during the blow with air 
 depends chiefly on the compactness and thickness, or depth, of 
 the fuel bed and the rate of blowing. If the fuel bed is deep and 
 compact, the resulting gas will be combustible on account of 
 containing a considerable amount of CO and generally very 
 little CO 2 . But, on the other hand, if the fuel bed is thin and 
 open, a strong blast will send so much air into the fuel that CO 2 
 will be the principal compound of C and O formed, and the gas 
 will not be combustible. The heating of the fuel bed will be 
 much more rapid when CO 2 is formed chiefly than when a 
 combustible air gas is produced. 
 
356 THE GAS ENGINE 
 
 Both the above methods of blowing air into the fuel find appli- 
 cation in intermittent gas-making processes. Which shall be 
 selected depends on the kind of gas desired. That in which 
 combustible gas is made during the period of air blowing seems 
 to have been in use much longer and finds far more extensive 
 application than that in which non-combustible gas is made 
 during the period of blowing. The air gas and water gas of the 
 latter method can be mixed and used together in the combustion 
 motor with entirely satisfactory results. 
 
 237. Twin Producers for Intermittent Gas Making. Producers 
 are often used in pairs, the main object in pairing them being to 
 secure the secondary fire action on the unstable gases that are 
 distilled from the green fuel. A third producer is sometimes 
 installed as a relay in such plants when there is a practically 
 continuous demand for gas no shut downs. 
 
 One method of operating the twin producers on bituminous 
 coal is to blow both (with air only) from the top in parallel so 
 that the air passes down through the fuel that is charged on at 
 the top and the non-stable gases of distillation are broken up 
 into stable gases (and some free carbon generally) by passing 
 down through the hot zone of combustion. The blow is continued 
 till the fuel is sufficiently hot. The air is then cut off and the 
 steam admitted into the sealed space below the fuel in one of 
 the producers, so that it passes up through the fuel in one of the 
 producers and then over to the top of the other producer, and 
 thence down through the second fuel bed. All the gases distilled 
 during the "run" with steam have to pass through the incan- 
 descent fuel in the second bed and are there acted on by the heat 
 to dissociate and convert the unstable ones into permanent gases. 
 Air is then blown in again after shutting off the steam. After 
 sufficient heating the air is cut off again and another run made 
 with steam, but this time the steam is admitted at the bottom of 
 the other producer, so that the path of the water gas and the 
 distillates that accompany it is reversed. Air blowing then 
 comes again and the whole cycle is repeated. 
 
 If the draught of air during the blowing period fe induced by 
 an exhauster interposed in the gas main from the producer, the 
 
FUELS AND GAS MAKING 
 
 357 
 
 Hydraulic Piston 
 
 Steam Valve 
 
 Ash pit , 
 
 DoorW^ Generate 
 
 /\ ^ 
 
 aning 
 
 To Exhauster and Producer 
 ~~* Gas Holder 
 
 FIG. 116. 
 Intermittent Downdraught Gas Producer Plant. 
 
 Showing contents of producer after 51 hours' run at practically full load without 
 shutdown of engine. 5oo-horsepower engine. 
 
 The fresh or green fuel charge was made up largely of anthracite with a topping of 
 bituminous coal. Bituminous coal was charged on at the top as needed. 
 
 The producers were blasted at the same time in parallel with a down draft of air. 
 Steam was blown into the bottoms of the producers alternately between air- 
 blasting periods; into No. i after the first period of air blasting, and into No. 2 
 after the second air blast, etc. Proc. Amer. Soc. Mech. Engrs., mid-November, 
 1997. 
 
358 THE GAS ENGINE 
 
 producers can be left open at the top during this part of the 
 operation and fuel fed in. This obviates the use of an air lock 
 at the charging door. 
 
 It can doubtless be seen that there are several other methods 
 of working producers in pairs while always securing the 
 breaking up of the unstable gases by passing them through hot 
 fuel. 
 
 238. Blast -Furnace Gas. The blast furnace for reducing 
 iron ore to pig iron discharges combustible gas from the top of 
 the burden of ore, fuel, and flux that is charged into it. Air only 
 is blown in through the tuyeres near the bottom of the enclosed 
 chamber. In the lower part of the burden the process is probably 
 nearly identical with that for making air gas. As the air gas 
 made in the lower part passes upward it undergoes various 
 chemical changes of which the net result is the addition of oxygen 
 to a part of the CO that started up from the lower part of the 
 furnace. This additional oxygen comes from the ore during its 
 reduction from an oxide of iron to metallic iron. When lime- 
 stone, CaCO g , is used for the flux, CO 2 is driven off from it at the 
 upper part of the furnace and mingles with the escaping gas. 
 
 CaC0 3 = CaO + CO 2 . 
 
 The air gas that was formed at the lower part of the furnace 
 is therefore reduced in richness (made leaner) as it passes up 
 through the furnace. If lime is used as a flux, there is less 
 dilution of the gas than with limestone as the flux. If the fuel 
 contains volatile hydrocarbons, these will be distilled off and the 
 gas will be enriched by them. 
 
 The composition of blast-furnace gas varies therefore with the 
 kinds of fuel, flux, and ore. As produced in the general method 
 of practice of iron-ore reduction, it has a lower heating value per 
 cubic foot than that made by any of the producer methods under 
 proper conditions of operation. A richer gas will generally come 
 from a blast furnace using coal than from one using coke, 
 the increased richness being due to the volatile portion of the 
 coal. 
 
FUELS AND GAS MAKING 359 
 
 With coke as a fuel in the blast furnace there is very little 
 hydrogen in the gas, since the moisture in the air and the charge 
 is then the chief source of hydrogen. It has been pointed out by 
 those dealing with blast furnaces that if the blast carries water 
 in from a slight water leak at a tuyere, there will be a very material 
 addition of hydrogen to the gas and a change of heat value. 
 The gas must of course be cleaned so as to be free from dust 
 and grit before using in the combustion motor. 
 
 239. Coke-Oven Gas. In the manufacture of coke, bitu- 
 minous coal is heated so that the volatile part is driven off almost 
 completely. The remainder is the coke product for which the 
 operation is carried on. Coke making is in a general way similar 
 to gas making by the retort process with bituminous coal. The 
 chief product in one case is the by-product in the other. The 
 chief difference in the two processes is in the rate of gasification. 
 In gas making the rate of distillation is such as to secure the best 
 results in the gas made; in coking the rate is regulated to procure 
 the best coke, which is generally that which is the strongest 
 for resisting mechanical stress. The coals for the two proc- 
 esses are of course selected with a view to the best results in 
 each case. 
 
 In retort processes of coking coal the heat is supplied by 
 burning the gas that is distilled off. With a fat coal there is 
 more of the gas than is needed for coking when the coke oven 
 is suitably made. This excess of gas can be used in the 
 combustion motor successfully. It is a richer gas generally 
 than that made by any of the producer processes that have 
 been mentioned. Its richness varies with the kind of coal 
 and the stage of completion of the distillation. The following 
 is taken from a paper on "The By-Product Coke Oven" by 
 Mr. W. H. Blauvelt* 
 
 "The surplus from the by-product coke oven is the portion 
 remaining after sufficient gas has been used for heating the ovens, 
 and the amount varies greatly with the fuel used. In lean coals, 
 low in volatile matter, there might perhaps be no surplus, while 
 in rich gassy coals the amount may be from 4000 to 4500 feet per 
 * Proceedings Amer. Soc. Mech. Engrs., March, 1908, Vol. 30. 
 
360 THE GAS ENGINE 
 
 net ton of coal. ... the gas is essentially similar to that made 
 in gas works. Following is a typical analysis: 
 
 Carbon dioxide 1.3 
 
 Benzene 1.2 
 
 Ethylene 4.2 
 
 Oxygen 0.5 
 
 Carbon monoxide 5.1 
 
 Methane 35.5 
 
 Hydrogen 48 . o 
 
 Nitrogen 4.2 
 
 B.t.u. per cubic foot 679 
 
 "The calorific value of the gas may vary from 550 to 750 B.t.u. 
 per cubic foot. " 
 
 240. Oil Gas from Petroleum. When petroleum is destruc- 
 tively distilled by bringing small quantities at a time in contact 
 with red-hot substances, the heavy hydrocarbons are changed 
 into others which are mostly permanent gases under atmospheric 
 conditions. The gas varies in composition with the temperature 
 of distilling and the fineness of division of the liquid when it 
 comes into contact with the hot surface. In a general way the 
 oil gas made in this manner resembles coal gas by the retort 
 process. Oil-water gas is also made from petroleum by mixing 
 steam with the vaporized oil. 
 
 Oil gas is too expensive for economical use in the combustion 
 motor. 
 
 241. Gasoline Gas or Carbureted Air. If air is caused to 
 bubble through gasoline, or is brought into contact with fabrics, 
 wire gauze, etc., that are saturated with gasoline, it will become 
 impregnated with the vapor of gasoline to an extent that depends 
 on the time and intimacy of contact of the air with the gasoline. 
 If the amount of gasoline taken up does not exceed two gallons 
 per 1000 cubic feet of air, the gasoline vapor will remain a vapor 
 in the air under atmospheric conditions. 
 
 Gas made in this manner can be used in the internal-combustion 
 motor and for illuminating. The gas must be mixed with air for 
 burning in the motor, after the manner of other gases. 
 
FUELS AND GAS MAKING 361 
 
 242. Tar Destruction in Gas Making. Some .of the methods 
 of tar destruction by passing the unstable gases from coal and 
 lignites through carbon or fuel heated to incandescence have 
 been mentioned in connection with different processes of gas 
 making. The destruction of the tar is practically complete by 
 at least part of these methods when the apparatus is properly 
 operated. 
 
 There is generally a formation of free carbon in a granular or 
 graphitic state accompanying the destruction of tar vapors in 
 this manner. The gas-making plant must therefore be designed 
 with provision for cleaning the carbon deposit from such places 
 as it may lodge, and for removing the carbon from the gas. The 
 graphitic carbon does not wash out in the ordinary coke or other 
 types of scrubber as well or completely as the carbon that comes 
 from a producer that has no special provision for tar destruction 
 and which allows most of the heavy hydrocarbons to pass out as 
 condensable gases that form tar. 
 
 The graphitic carbon can be filtered out by passing the gas 
 through excelsior, cloth, burlap, etc., which should not be so 
 closely woven or packed as to prevent reasonably free flow of the 
 gas through it. This method is similar to that used sometimes 
 for cleaning air for ventilation. 
 
 243. Variation in Quality of Producer Gas. There are 
 several causes that make considerable variation in the quality or 
 heating power of the gas from a producer. 
 
 It has already been pointed out that temporary increase of 
 the steam or water supplied to a continuous producer will give a 
 temporarily richer gas than the producer can regularly supply. 
 Cutting down the steam temporarily or continuously will give a 
 leaner gas. 
 
 Cracks in the bed of fuel, or settling of the fuel away from 
 the walls of the producer when bituminous coal is used, tends to 
 let the air and steam pass through without undergoing the 
 required chemical changes. Generally more than the normal 
 amount of CO 2 and a lean gas result. This trouble can be 
 obviated by proper attention to stoking and charging of the fuel. 
 
 Variation in the thickness of the fuel bed, as by the bed becom- 
 
362 THE GAS ENGINE 
 
 ing thin by the accumulation of ash while the top level is kept at 
 a constant height,' also affects the quality of the gas. 
 
 The chemical changes are not the same in their ultimate results 
 when the temperature of the fuel is low as when it is high. Dif- 
 ferent qualities of gas result under the two conditions. The 
 nature of the variation with the change of temperature depends 
 so much on the condition and kind of fuel, the thickness of the 
 fuel bed, and the force of the blast, that it is hardly possible to 
 make general statements regarding them. 
 
 244. Observation of Quality of Gas from a Producer. When 
 operating a gas producer in regular service, it is desirable to 
 know practically all the time the quality or heating value of the 
 gas flowing from the producer, and essential to know it at frequent 
 intervals. Some means that indicate the quality of the gas 
 within a few seconds at most after it has passed from the producer 
 is necessary for the best operation. Promptness in indicating 
 the quality is of more importance than accuracy of the results 
 except when efficiency tests of the producer or motor are being 
 made. 
 
 An open flame of the gas is a fair indication to the trained 
 eye of its nature. The gas burner can be attached to the 
 gas main leading from the scrubber. If the gas is led to the 
 burner through a glass tube stuffed with absorbent cotton, the 
 condition of the cleanliness of the gas can be observed. 
 
 Since most producer gas burns with a non-luminous flame, the 
 quality can often be observed more accurately by the use of an 
 incandescent mantle on the burner, or some other device which 
 immediately shows change of temperature to the eye. The 
 pressure of the gas going to the burner must be kept constant for 
 such a burner. 
 
 The pressure of the gas at the burner can be kept constant by 
 the use of a simple and inexpensive aspirator or other device for 
 drawing it continuously from the mains and delivering it to the 
 burner at constant pressure. 
 
 If the incandescent test burner is placed near a light of uniform 
 strength, a still more accurate means is arrived at'for noting the 
 quality of the gas. A simple photometric device for comparing 
 
FUELS AND GAS MAKING 363 
 
 the degree of luminosity of the incandescent pa/ts obviates the 
 error incident to direct observation of the lights. 
 
 The temperature of the products of combustion when some of 
 the producer gas is burned in an open flue is a prompt method 
 of determining the quality of the gas for the purpose of managing 
 a producer. 
 
 The temperature of the gases leaving the producer is also an 
 indication of how the producer is working. It can be taken 
 with a thermometer inserted in the gas main, which may be 
 arranged to read at a distance in a suitable location. 
 
 245. Continuous Calorimeter Tests of Gas from Producer. 
 More refined tests of the quality of the gas within a short time after 
 it leaves the producer can be made by suitable types of calo- 
 rimeters. Several instruments for this purpose have been devised 
 and operated. The principle of operation is generally that of 
 feeding the calorimeter both gas and water in predetermined 
 rates and observing the change of temperature of the water while 
 flowing through the calorimeter. The most common method 
 seems to be to keep a constant ratio between the water passed 
 through the calorimeter and the Amount of gas consumed in the 
 same instrument. 
 
 The gas for the calorimeter is generally drawn continuously 
 at a constant rate from the gas main of the producer at a suitable 
 point. The calorimeter will therefore show the average heat 
 value of the gas only when the rate of flow from the producer 
 is uniform. If there is any variation in the rate at which the 
 producer makes gas, the mean value of observations of the calorim- 
 eter taken at equal time intervals, or a continuous record, will 
 not give the average heat value of the gas that is stored in a 
 tank during the operation of the producer for any period of time. 
 There is generally considerable variation in both the quality of 
 the gas and the rate of its production even in continuous types of 
 producers. 
 
 For accurate results in the use of a continuous calorimeter of 
 the kind just mentioned, the gas should be drawn from the 
 producer main at a rate proportional to the rate at which the gas 
 flows through the main; in other words, at a rate proportional 
 
364 THE GAS ENGINE 
 
 to the rate at which the producer is making gas of a standard 
 temperature and pressure. Since it would be difficult to burn 
 the gas in the calorimeter at a greatly different and rapidly 
 varying rate, another method is to give each reading of the calorim- 
 eter a weight in averaging that is proportional to the rate of 
 gas production at the instant the gas corresponding to the reading 
 was taken from the main, or to move a recording chart at a rate 
 similarly proportional to the rate of making the gas. There 
 would generally be difficulty in getting accurate records in the 
 latter manner, however, on account of the lag of the calorimeter 
 in indicating the quality of the gas. 
 
 The nature and extent of the error introduced in determining 
 the average heat value of gas flowing through a main by the use 
 of the method of taking samples of gas from the main at equal 
 time intervals and giving each determination equal weight in 
 averaging is shown by the following numerical example. 
 
 A combustion motor delivering mechanical power at a constant 
 rate requires 2,000,000 B.t.u. of gas per hour. The gas varies in 
 lower (effective) heat value from 100 to 125 B.t.u. per cubic foot 
 of, standard gas. When the gas is of the 100 B.t.u. quality, the 
 motor will take 20,000 cubic feet per hour; and when it is of 
 the 125 B.t.u. quality, 16,000 cubic feet per hour will be con- 
 sumed. The required volume of the leaner gas is 25 per cent 
 greater than that of the richer gas. 
 
 If the motor runs on each kind of gas an hour, the average 
 heat value of the total amount of gas used, taking volumes into 
 account, which is the correct method, is 
 
 20.000 X zoo -f 16,000 X 125 r , 
 
 ^ = in B.t.u. per cu. ft. 
 36,000 
 
 The incorrect average heat value, as found by giving each 
 determination (100 and 125 B.t.u.) equal weight, is 
 
 100 + "S = 112.5 B.t.u. per cu. ft. 
 
 The difference of the two heat values thus obtained is 1.5 
 B.t.u. The incorrect method gives a value ij pef cent greater 
 than the true average heat value. 
 
FUELS AND GAS MAKING 365 
 
 The same amount of error occurs when the readings of a con- 
 tinuous calorimeter that takes gas from a main at uniform rate 
 are used without correction for the different rates of flow of the 
 lean and rich gas through the main. 
 
 The error just pointed out is favorable to the producer and 
 against the motor. 
 
 Variations in the heat value of producer gas as great as those 
 that have been used in this example, and even greater, are not 
 unusual in practice. 
 
 246. Efficiency Bases of Gas Producers. The efficiency of 
 the gas producer that is of interest to the manufacturer and 
 consumer of gas for the internal-combustion motor is the ratio 
 of the heat value of all the gas produced from a stated amount of 
 fuel to the heat value of all the fuel and all the mechanical or 
 electrical energy used for all purposes relative to the production 
 of the gas. The rate of gasification is also of importance, since 
 the higher the rate the less the initial cost of a gas plant of a given 
 capacity. 
 
 It is an open question whether the higher or the lower heat 
 value of the gas shall be taken in determining the efficiency of 
 a gas producer. It should therefore be distinctly stated which 
 heat value is to be used in any guaranty of efficiency. 
 
 Instead of expressing the effectiveness of the action of the 
 producer as efficiency, a convenient and suitable method is to state 
 the amount of gas at a standard temperature and pressure, and 
 the heat value (higher or lower) per unit volume (as a cubic foot) 
 that a producer and its accessories will deliver from a stated 
 weight of coal or other fuel of a stated quality (heat value per 
 pound, from a specified mine and how prepared, etc.), also taking 
 into account the mechanical, electrical, or other energy received 
 from outside sources. 
 
 In both the above cases the loss of unburned fuel in the ash 
 counts against the producer. 
 
 On account of the loss of unburned fuel in the ash, the efficiency 
 is, for some purposes, divided into grate efficiency and efficiency 
 of such other parts of the process as are under consideration. 
 The product obtained by multiplying together the grate efficiency 
 
366 THE GAS ENGINE 
 
 and the efficiency of the other parts of the process under consider- 
 ation is the real efficiency of such parts of the process. 
 
 The expressions for the commercial efficiency and the grate 
 efficiency of a gas producer are: 
 
 Commercial ) B.t.u. of total gas made. 
 
 efficiency $ B.t.u. of fuel fed to producer + B.t.u. equivalent of 
 energy received by producer from outside sources. 
 
 B.t.u. of fuel actually burned in producer. 
 
 Grate efficiency = 
 
 B.t.u. of fuel fed to producer. 
 
 For other efficiencies the items included depend so much on 
 the kind of producer and the methods of operating the auxiliaries 
 that it is hardly possible to give formulas that will cover more 
 than one type of producer and its accessories. Outside of the 
 commercial efficiency and the grate efficiency it is practically 
 always necessary to define the efficiency by the items included 
 rather than by a specific name. 
 
 The comparison of different steps of the process in producers 
 similarly operated with regard to the method of producing draught 
 is not generally difficult. But in some cases, as when the draught 
 is induced by mechanical means in one producer, and by a steam 
 blower in the other, the refinements necessary to compare effi- 
 ciencies that exclude the energy for inducing the draught become 
 such as to necessitate the greatest care and judgment in deter- 
 mining the required data by trial. 
 
 In the case of a gas power plant producing its own gas, the 
 total efficiency of the conversion of the heat energy of the coal 
 into mechanical energy delivered by the motor is determined 
 more frequently than the efficiency of the producer alone. The 
 reason for this is that there are seldom adequate means 'for 
 measuring the amount of gas produced. Gas meters of sufficient 
 capacity are cumbersome and expensive, and less expensive 
 means are not sufficiently accurate for reliable results under 
 ordinary circumstances. 
 
CHAPTER XIX. 
 PRESSURE-VOLUME DIAGRAMS. 
 
 247. Equations for Work. When the pressure of a gas or 
 liquid acts on a piston and moves it with a rectilinear motion, 
 then, if the piston face acted on by the pressure is flat and per- 
 pendicular to the direction of its motion, the energy expended, 
 or work dqne in moving the piston, is expressed by the equation 
 
 W= pAL, 
 in which 
 
 p= pressure per unit area, 
 
 A area of piston face, 
 
 L = length of stroke of piston. 
 
 When the piston face does not lie in a plane perpendicular to 
 the direction of its motion, as when the face is crowned, convex, 
 irregular, or slanted, then A can be taken as the area of the cross- 
 section of the space through which the piston moves, the cross - 
 section being perpendicular to the direction of motion of the 
 piston. 
 
 In the equation just written, the product of 
 
 A X L = volume swept through by face of piston. 
 The equation for the energy expended can therefore be written 
 
 ir->, 
 
 in which 
 
 v = volume swept through by face of piston, 
 
 and the other notation is as given for the preceding equation. 
 
 If the piston moves against (toward) the resistance of the 
 pressure on its face, then the energy delivered to the gas or liquid 
 by the piston is expressed by the same equations. 
 
 367 
 
368 THE GAS ENGINE 
 
 The expression W= pv can be represented graphically on a 
 diagram with rectangular coordinates. This is done in Fig. 117. 
 Pressures are measured from the horizontal axis OF in a direc- 
 tion perpendicular to OF. Volumes 
 are measured from the vertical 
 axis OP in a direction perpendic- 
 ular to OP. 
 
 When the pressure is constant, 
 as has been assumed, it is repre- 
 sented throughout the stroke of the 
 piston by the horizontal line at a 
 distance Op from the F axis. The 
 
 Area = 
 
 volume swept through by the face FIG. 117. 
 
 of the piston is represented by the 
 
 distance Ov. The product Op X Ov is therefore represented by 
 the area of the rectangle bounded by the coordinate axes OP 
 and OF together with the lines drawn through p and v to com- 
 plete the rectangle. Instead of taking Op and Ov as the nota- 
 tion to indicate corresponding distances, it is customary to use 
 only p and v for this purpose. By this notation 
 
 pv = area of rectangle. 
 
 The area of the rectangle represents, in accordance with the 
 scales of pressure and volume selected, the energy transferred 
 from the gas or liquid to the piston, or vice versa. 
 
 If the pressure is variable during the stroke of the piston, as 
 indicated by the curved line in Fig. 118, then the area enclosed 
 by the curved pressure line, the coordinate axes, and the vertical 
 through V can be determined approximately by dividing it into 
 several vertical strips or partial areas by lines parallel to the 
 vertical coordinate axis, then multiplying the width of each strip 
 by its average, or mean, height, and adding all the products 
 together. The mean height of each strip must be determined 
 by judgment, and is therefore not mathematically accurate. 
 The sum of the partial areas determined as stated is therefore 
 the approximate area of the total enclosed space. 
 
 The area thus determined for each small strip approximately 
 
PRESSURE-VOLUME DIAGRAMS 
 
 369 
 
 represents the work done while the piston is sweeping through a 
 volume corresponding to the width of the strip. If the width of 
 the first strip is A X F, and its mean height is P v then the work done 
 while the piston sweeps through the volume A t F is w l = P^F. 
 And similarly for the second partial area, w 2 = P 2 A 2 F. And so 
 on for all the partial areas. 
 
 FIG. 118. 
 
 The total work done during the complete stroke of the piston 
 is therefore approximately 
 
 W 
 
 + P 2 A 2 F + 
 
 + . . + P m A m 7. 
 
 If all the partial areas are of the same width, so that A X F = A 2 F 
 = A 3 F, etc., the mean value of the pressure can be found by adding 
 together all the P's and dividing their sum by the number of 
 partial areas. The total area is then found by multiplying the 
 volume V by the mean value of the pressure, thus, 
 
 W = total area = P mean V. 
 
 When the partial areas into which the total area is divided 
 become almost infinitely great in number, then the method of 
 determining the total area becomes that of integral calculus. The 
 width of each strip is then represented by the differential quantity 
 
370 
 
 THE GAS ENGINE 
 
 dV, and the height of each strip is represented by p, as in Fig. 
 1-19. The area of each differential strip is therefore pdV. The 
 value of p is in general different for each elementary strip. The 
 work or mechanical energy corresponding to each differential 
 strip can be called dW. The equation for the differential 
 quantities is then 
 
 dW = pdV. 
 
 The accurate total area, or work, is represented by the integral 
 of the differential areas, thus, 
 
 W = total area = 
 
 This integration can be performed mathematically only when 
 there is a definite known relation between p and V. In general 
 there is no such relation, so the mathematical integration is in 
 general impossible. 
 
 The planimeter can always be used to make the integration 
 mechanically. 
 
 FIG. 119. 
 
 Fig. 119 shows in a general way the nature of the variation of 
 the pressure when gas compressed in a closed cylinder to the 
 volume F! is allowed to expand and drive out a piston until the 
 volume becomes V r The work or energy transferred from the gas 
 to the piston is here represented by the area bounded by the 
 
lines 
 is 
 
 PRESSURE-VOLUME DIAGRAMS 371 
 
 ^ The calculus expression for ttye work or area 
 
 f*V 
 
 W = total area = / pdV. 
 
 If the piston compresses the gas from the volume F 2 to V v the 
 energy that the piston delivers to the gas is represented by the 
 
 FIG. 120. 
 
 248. Pressure-Volume Diagram for Complete Cycle. Fig. 
 1 20 represents in a general way the events in a combustion motor 
 from the time the charge of combustible mixture is received in the 
 motor cylinder till the charge has been compressed, burned, 
 expanded, and discharged so that the pressure in the cylinder is 
 again the same as at first and the piston has returned to its initial 
 position. In this case the horizontal axis OV represents zero 
 pressure (about 14.7 pounds per square inch below atmospheric 
 pressure). 
 
 The charge at the initial position of the piston has the volume 
 V a and the pressure P a at the point A on the diagram. During 
 the instroke of the piston the charge is compressed to the volume 
 V b and the pressures during compression are represented by the 
 line AB. After the completion of compression the pressure is 
 increased from P b to P c by the partial combustion of the charge, 
 
372 THE GAS ENGINE 
 
 while the volume remains unchanged. The volume then increases 
 during the outstroke of the piston from V b to the initial value V a . 
 The pressure line during the expansion is CD. The pressure 
 then falls from P d to the initial pressure P a , while the volume 
 remains constant. 
 
 The energy delivered to the gas by the piston during com- 
 pression is represented by the area AV a V b BA; and the energy 
 delivered to the piston by the gas during the outstroke is repre- 
 sented by the area CDV a V b C. The difference of these two areas, 
 which is the area A BCD A, represents the energy received by 
 the piston during the complete cycle. No mechanical energy is 
 received or delivered by the piston during the changes of pressure 
 at constant volume from B to C and from D to A. 
 
 The diagram A BCD is the pressure-volume diagram of the 
 motor during the cycle. Its area can be found by the methods 
 given above. The calculus expression of its area and of the 
 energy transferred is 
 
 W = area ABCD = f F * hdV, 
 
 JVb 
 
 in which h is the height of any differential vertical strip of the 
 area enclosed by the. lines of the diagram and is in general a 
 variable. The value of h for any differential strip is equal to 
 the difference of the pressures acting on the piston while it 
 occupies the two corresponding positions on the instroke and on 
 the outstroke. 
 
 When the area of the diagram has been determined with a 
 planimeter, the mean value of h is found by dividing the area by 
 the horizontal length of the diagram = V a V b . The mathematical 
 expression is 
 
 A BCD area ABCD 
 
 length of diagram V a V b 
 or 
 
 Mean effective _ ,, _ _ Area of diagram. _ 
 pressure Length of diagram X Ibs. per sq. in. per 
 
 inch compression of indicator spring 
 
 which is the mean effective pressure of the diagram. 
 
PRESSURE-VOLUME DIAGRAMS 373 
 
 249. Indicator Diagram. The indicator diagram is essen- 
 tially a pressure-volume diagram, generally on a miniature scale. 
 The fact that the horizontal length represents volumes is seldom 
 taken into consideration, however, in determining indicated 
 power by its aid. In this connection its use is to give the mean 
 effective pressure. The latter is generally determined from it 
 either by the aid of a planimeter for finding its area, and then 
 dividing the area by the length of the diagram, or by the use of 
 an averaging instrument that gives a direct reading of the mean 
 height of the diagram after its tracing point has been passed 
 around its profile in a proper manner. 
 
 The mean effective pressure thus determined is then used in 
 connection with the proper factors for determining horsepower, 
 etc. 
 
 Mechanical integrators which, when set to correspond to the 
 piston area, length of stroke, and speed of rotation of the motor 
 from which the indicator card was taken, give a direct reading of 
 the horsepower, are also used. 
 
CHAPTER XX. 
 THEORETICAL HEAT CYCLES. 
 
 250. Assumptions for Theoretical Cycles. By the assump- 
 tion of conditions that differ more or less from those under 
 which an internal-combustion motor actually operates, it becomes 
 possible to obtain theoretical pressure-volume diagrams whose 
 boundary lines represent mathematical equations and whose 
 areas can be determined by mathematical integration. Such 
 diagrams are useful in pointing out in a general way the features 
 essential to securing the greatest efficiency in actual practice for 
 the kind of cycle under consideration, and the kind of cycle that 
 will give the greatest theoretical efficiency with a perfect gas. 
 
 Among the assumptions to be made from the theoretical cases 
 there are three that are common to all the theoretical cycles. 
 They are: 
 
 First. That the piston moves without frictional resistance. 
 
 Second. That the walls of the space in which the gas is enclosed 
 during the cycle are impervious to heat; or expressed 
 otherwise, that the motor piston, cylinder, etc., 
 neither abstract heat from the gas nor give up heat 
 to the gas. 
 
 Third. That a perfect gas is used. 
 
 251. Notation. - 
 
 C p = specific heat of constant pressure, B.t.u. per pound. 
 Cv = specific heat of constant volume, B.t.u. per pound. 
 
 G = j = factor for converting foot-pounds into B.t.u.; 
 
 GW= B.t.u. 
 H = total heat added to or abstracted from the gas, B.t.u. 
 
 374 
 
THEORETICAL HEAT CYCLES 375 
 
 Hi = heat input by combustion, B.t.u. 
 H d = heat discharged or discarded, B.t.u. 
 J = mechanical equivalent of heat. / = 778 ft.-lbs. = 
 
 1 B.t.u. 
 
 P = absolute pressure, pounds per square foot = 144 X Ibs. 
 per sq. in. 
 
 P V P V 
 
 R = Q = * i- = mechanical work done by the expan- 
 
 ^0 *I 
 
 sion of unit weight or mass of a perfect gas at constant 
 
 pressure while heat is added to increase its temperature 
 
 one degree. Foot-pounds per Fahrenheit degree for one 
 
 pound of gas. 
 S = sensible heat added to or taken from a gas to cause change 
 
 of temperature. Sensible heat is that which affects the 
 
 thermometer. B.t.u. per pound. 
 T = absolute temperature, Fahrenheit degrees. The zero 
 
 of absolute Fahrenheit temperature is 459 below zero 
 
 Fahrenheit, which is 491 F. below the freezing point of 
 
 water at atmospheric temperature. 
 V = volume, cubic feet. 
 W = mechanical work, foot-pounds. 
 /? = ratio of specific volume of products of combustion to 
 
 specific volume of the charge before combustion. 
 
 Q 
 
 X = - = ratio of specific heat of constant pressure to specific 
 C r 
 
 heat of constant volume. 
 
 s = 2.71828 = io' 4342945 = the base of hyperbolic, natural, 
 or Naperian logarithms. Log ^4 = 2.3026 X Iog 10 ^4. 
 Log 10 ^4 is the common logarithm of A. 
 
 252. Additional Laws of a Perfect Gas. Some of the laws of 
 a perfect gas have been given in Chapter XVI. The last equation 
 of section 196, modified as to subscripts, is 
 
 PV T 
 
3/6 THE GAS ENGINE 
 
 in which P, F, and T represent the pressure, volume, and tem- 
 perature of a perfect gas for any assumed condition, and P and 
 T may be taken conveniently as the pressure and temperature 
 at which the specific volume of gas is usually given. F is then 
 the corresponding specific volume. The latter is usually given 
 at atmospheric pressure and either the freezing point of pure 
 water or at a slightly higher temperature that approaches more 
 nearly to average atmospheric temperature. 
 
 The specific volumes of actual gases are given in Table I for 
 both 32 F. and 62 F., corresponding to 491 and 521 degrees 
 absolute Fahrenheit. 
 
 By transposition, the last equation can be brought to the 
 form 
 
 The expression 
 
 - - = a constant for any particular perfect gas. 
 
 Its value can be found by substituting numerical values belonging 
 to the gas. The numerical values must, of course, accord with 
 the system of units adopted. Thus, for a pressure of 14.7 pounds 
 per square inch = 2116.8 pounds per square foot, and 32 F. = 
 491 degrees absolute Fahrenheit, the specific volume of air is 
 12.39 cubic feet per pound. Therefore, for air, taking the 
 pressure in pounds per square foot to correspond to the cubic 
 foot unit of volume, 
 
 PF =- J - 8Xl2 ' 39 r = 53 . 42 r, 
 
 491 
 
 whence 
 
 PF 
 
 = 53.42 for air. 
 
 The expression P F represents, for any perfect gas, the 
 mechanical work done by its expansion, while, the pressure 
 remains constant at P , from an initial condition of zero volume 
 
THEORETICAL HEAT CYCLES 377 
 
 to a final condition represented by P ,F ,r o . Xhe change of 
 
 y 
 volume for each degree of temperature = - The mechanical 
 
 TQ 
 
 work done by the expansion of the gas during a rise of temperature 
 of one degree while the pressure remains constant is therefore 
 
 When the temperature is taken at 32 F. (T Q = 491 abs. F.), 
 the change of volume of a perfect gas for each degree Fahrenheit 
 change of temperature, when the pressure remains constant 
 during the change, is T | T of its volume at 32 F. 
 
 The mechanical work done by the expansion of 1 pound of 
 air while enough heat is being added to it to increase its tempera- 
 ture 1 F., the pressure remaining constant, is, in accordance with 
 the numerical computation just made, 53.42 foot-pounds for air 
 considered as a perfect gas. 
 
 When a gas is cooled by abstracting heat from it, the work it 
 does during contraction is negative. The amount of this negative 
 work per degree change of temperature is the same as when the 
 temperature is increased one degree, the pressure remaining 
 constant in each case. For air the negative mechanical work due 
 to cooling 1 F. at constant pressure is 53.42 foot-pounds as 
 before. 
 
 P V 
 
 will, for convenience, be represented by R. One of the 
 
 TQ 
 
 general expressions of the relation between the pressure, volume, 
 and temperature of a perfect gas thus becomes 
 
 PV= RT. 
 
 The numerical value of R can be computed for any perfect gas 
 in a manner similar to that by which it has been computed for 
 air, for which R = 53.42 foot-pounds. (This must not be taken 
 to mean that air is a perfect gas.) 
 
 Another property of a perfect gas is that when the temperature 
 of any given quantity (mass, weight) of the gas is increased any 
 given amount (as a specified number of degrees) by the addition 
 
3/8 THE GAS ENGINE 
 
 of heat, the amount of heat that is retained in the gas to produce 
 the given change of temperature is always the same whether the 
 pressure or the volume remains constant or both change. The 
 significance of this is that none of the heat energy added is con- 
 verted into latent heat for changing the internal or molecular 
 condition of the gas with change of pressure, volume, and tem- 
 perature.* 
 
 The heat which causes change of temperature only is called 
 " sensible " heat. 
 
 253. Relation between Specific Heat of Constant Volume and 
 of Constant Pressure for a Perfect Gas. The specific heat of 
 constant volume of a gas has already been defined as the amount 
 of heat required to increase the temperature of a given weight 
 of gas 1 degree while the volume remains constant; and the 
 specific heat of constant pressure has also been defined as the 
 amount of heat required to increase the temperature of a given 
 weight of the gas 1 degree while the pressure remains unchanged. 
 
 In the case of the specific heat of constant volume no external 
 (mechanical) work is done, since there is no change of volume 
 during the change of temperature. 
 
 The specific heat of constant pressure includes both the heat to 
 
 * The conversion of water into steam by the addition of heat is an example 
 that affords a means of conceiving what is meant by "latent heat." When 
 heat is added to water after it has been brought up to the boiling point (about 
 2i2F. at atmospheric pressure) the water is all converted into steam with- 
 out rise of temperature if the pressure is kept constant. One pound of water 
 at 2i2F. and 14.7 pounds per square inch pressure requires to convert it into 
 steam at the same pressure and temperature, about 965.7 B.t.u. of heat. 
 The pound of water makes about 26.36 cubic feet of steam at the given pressure 
 and temperature, which practically measures the increase of volume during 
 the change from water to steam. (The volume of the water is so small in 
 comparison with that of the steam as to be negligible.) 
 
 The mechanical work done by the expansion of the water into steam is 
 therefore (14.7 X 144) 26.36 = 55,800 foot-pounds about, which corresponds 
 to 55,800 *- 778 = 71.7 B.t.u. The difference between this last quantity 
 and the total heat of conversion, 965.7 71.7 = 894 B.t.u., is the amount 
 of heat that has become latent and is not measurable in the steam as change 
 of temperature, or in mechanical work done during the formation of the 
 steam. 
 
THEORETICAL HEAT CYCLES 379 
 
 increase the temperature of the gas 1 degree and that converted 
 into external (mechanical) work done by the expansion of the gas 
 at constant pressure while heat is added to increase the tempera- 
 ture 1 degree. It has been shown in the preceding section that 
 the external work done during 1 degree change of temperature 
 
 P V 
 
 while the pressure remains constant is ^ = R. It has also 
 
 * o 
 
 been stated as one of the properties of a perfect gas, that the amount 
 of heat retained in the gas to increase the temperature of a given 
 weight of the gas 1 degree is always the same whether the pressure 
 or the volume is constant, or both vary. Therefore the amount 
 of heat retained in the gas to increase its temperature 1 degree 
 when the pressure is kept constant and the volume changes is the 
 same as the specific heat of constant volume when unit weight 
 of the gas is taken. The specific heat of constant pressure, for a 
 perfect gas, is therefore equal to the specific heat of constant 
 volume plus the heat equivalent of the external work done by the 
 expansion of the gas on account of its increase of temperature. 
 
 The mathematical expressions given below show the relation 
 between the specific heat of constant volume and the specific 
 heat of constant pressure for unit weight (or mass) of a perfect 
 gas. 
 
 R GVP PV 
 
 = C +- C+ = C 
 
 In foot-pound and Fahrenheit-degree units, the specific heat 
 of constant volume, Cv, for air is .1687 B.t.u. per pound. The 
 value of R has been calculated for air as 53.42 foot-pounds. The 
 mechanical equivalent of heat in the units taken is./= 778 foot- 
 pounds per B.t.u. By substitution in the above equation, 
 
 C p = .1687 + ^^ = .1687 + .0688 = .2375 B.t.u. for air. 
 
 778 
 
 254. Thermodynamic Changes in which One of the Quantities, 
 Pressure, Volume, Temperature, or Total Heat in the Gas, Remains 
 Constant. The four methods of change in the condition of a 
 gas for which the relations between P, F, and T are most readily 
 
380 
 
 THE GAS ENGINE 
 
 computable in the case of a perfect gas, and for which the heat 
 added to or discarded by the gas, as well as the corresponding 
 work done, can also be mathematically determined for the perfect 
 gas, are: 
 
 a. Pressure and temperature change at constant volume. 
 
 (Isometric change.) 
 
 b. Volume and temperature change at constant pressure. 
 
 (Isobaric or isopiestic change.) 
 
 c. Pressure and volume change at constant temperature. 
 
 (Isothermal change.) 
 
 d. Pressure, volume, and temperature all change, but no heat 
 
 is supplied to or abstracted from the gas. (Adiabatic 
 change. ) 
 
 In all the following changes it is convenient to assume that one 
 pound of gas is used. 
 
 255. Isometric Change. In Fig. 121 isometric change is 
 represented on the pressure-volume diagram 
 by the vertical line 1 2 parallel to the 
 pressure axis. Since the volume remains 
 constant, the changes of pressure and tem- 
 perature due to the addition or abstraction 
 of heat are both directly proportional to 
 the change in the amount of heat in the gas. 
 The amount of heat to be added to the gas 
 to change its temperature from T v corre- 
 spending to P X F, to T v corresponding to 
 
 FIG. 121. 
 
 whence 
 
 r , at constant volume is 
 H = C v (T 2 - 7\), 
 
 H H 
 
 The corresponding increase of pressure due to the heat H can 
 be determined from the above equations by substituting for T l 
 and T their values in terms of the ressure. These values are 
 
THEORETICAL HEAT CYCLES 
 
 381 
 
 obtained from the relation, common to all perfect gases, PV = 
 RT, whence 
 
 P V P V 
 
 .-Sr. 
 
 and 
 
 The substitution of these values in the equation H = 
 C v (T, - r,) gives 
 
 C V 
 
 H - -z (P - P) 
 R (F > ^ 
 
 P P 
 
 c,r 
 
 The following equations are also true for a perfect gas at con- 
 stant volume : 
 
 p, r, P 2 - p t r, - r t 
 
 ? = - and ^ - = J 
 
 p i T i p i T i 
 
 There is no external (mechanical) work done, since there is no 
 change of volume. This is expressed by the equation 
 
 W = o. 
 
 256. Isobaric Change. In Fig. 122 the change at constant 
 pressure is indicated by the horizontal line 1 2 parallel to the 
 
 V 2 
 
 FIG. 122. 
 
 volume axis of the diagram. Heat must be added to keep the 
 pressure constant while the volume increases. Part of the heat 
 added goes to perform external work, and the remainder to increase 
 the temperature of the gas so as to maintain a constant pressure. 
 
382 THE GAS ENGINE 
 
 The amount of external (mechanical) work done during the 
 expansion of the gas from F 1 to F 2 is 
 
 W = P (F 2 - V,). 
 
 The amount of sensible heat retained in the gas necessary to 
 increase the initial temperature 7\ to the final temperature T 2 
 corresponding with the volume F 2 is 
 
 5 = c, (T, - r,). 
 
 The values of 7\ and T 2 in terms of the corresponding volumes 
 are determined by the equation PV= RT, in which P is constant 
 in this case. Thus, 
 
 T, = - R F 2 ; and T, -- | V v 
 
 whence 
 
 The total amount of heat that must be added to the gas to 
 produce the change of temperature and do the external work is 
 
 H = S + GW 
 
 F 2 - FJ + GP (F 2 - FJ 
 
 
 The relation between the volume and the temperature is 
 
 T V T T V V 
 
 il-J-2; and ii - -'--1-2 - !-'. 
 
 r, F,' r, F, 
 
 257. Isothermal Change. In this case only enough heat is 
 added to the gas during its expansion to keep the temperature 
 constant. 
 
THEORETICAL HEAT CYCLES 
 
 383 
 
 In Fig. 123 the line 1 2 represents the general form of the 
 diagram for limited expansion of a perfect gas at constant tem- 
 perature. 
 
 Isothermal for 
 a Perfect Gas. 
 
 FIG. 123. 
 
 The external (mechanical) work done during the expansion 
 from F t to F 2 is represented by the area F t l 2F 2 F r The 
 mathematical expression for the external work is 
 
 W 
 
 r 
 / 
 
 J v. 
 
 PdV. 
 
 Since the temperature is constant, the pressure varies inversely 
 as the volume; therefore if F = volume at any point of the curve, 
 then 
 
 , 
 = -J l ; whence P 
 
 P l V 
 
 P l V l 
 
 - 
 V 
 
 By substituting this value of P in the quantity under the 
 integral sign, the equation for the external work done becomes 
 
 dV 
 
 = P.F, (log.F 2 - 
 
 (Log e = natural log. ) 
 
THE GAS ENGINE 
 
 For P 4 Fj may be substituted the equivalent value as given in 
 the equation PV = RT = P 1 V V whence 
 
 Since the temperature of the gas does not change, all the heat 
 given to it is converted into mechanical work. Therefore 
 
 W 
 - 
 
 J 
 
 V 
 
 258. Adiabatic Change. Since in this case no heat is either 
 added to or abstracted from the gas during its change of volume, 
 the pressure falls more rapidly during expansion than for iso- 
 thermal expansion. The temperature also drops during expan- 
 
 son. 
 
 FIG. 124. 
 
 In Fig. 124 adiabatic expansion is represented by the line 
 1 2. The initial volume is V l and the final volume V v 
 
 The external (mechanical) work done by the gas during any 
 infinitesimal increase of its volume is 
 
 dW = PdV 
 
THEORETICAL HEAT CYCLES 385 
 
 and the corresponding decrease of sensible heat* in the gas, as 
 indicated by its change of temperature, is 
 
 dS = C v dT. 
 
 There being no heat added to or abstracted from the gas by 
 any exterior source, the change of sensible heat must be equal to 
 the heat equivalent of the external work done. This is expressed 
 by the equation 
 
 dS = - GdW; or C v dT = - GPdV. 
 
 The negative sign appears in the last two equations because 
 when positive work is done by the expansion of the gas it causes 
 a decrease in the sensible heat in the gas, and the negative work 
 done by the gas during its compression causes an increase in the 
 sensible heat of the gas. 
 
 The last equation may be written, for convenience in further 
 development, in the form 
 
 o = C v dT + GPdV. 
 
 The value of dT can be expressed in terms of dV and dP as 
 found from the equation PV= RT, which, by differentiating, 
 becomes (remembering that p, V, and T are all variables in 
 adiabatic change) 
 
 PdV + VdP = RdT; whence dT = -dV + -dP. 
 
 R R 
 
 By substituting this value of dT in the next to the last equation, 
 it becomes 
 
 o = 2 VdP + & + G\ PdV 
 
 which, by multiplying by R, dividing by PV, and writing for 
 
 C v + GR its value C p , becomes 
 
 dP C^dV 
 
 O = - + "- - > 
 
 P C. V 
 
386 THE GAS ENGINE 
 
 Q 
 
 and by putting the ratio = X in the last equation, it is reduced 
 totheform ^ 
 
 p ~ l v ' 
 
 The integration of the last equation from zero to the values 
 P and V gives 
 
 Constant = log e P + I log e V 
 
 = log e P + lo ge V* 
 
 whence ,,; 
 
 PV A = constant. 
 
 Since PF^ has a constant value, 
 
 pyX = p y X = p y X 
 
 * l 1 A 2 r 2 > 
 
 of which the following are convenient forms for application : 
 p y X = p y X. _2 = [ _j ) . 
 
 M r i ^2 K 2 > p \F / ' 
 
 And from the equation PF= R7^, in which /? is a constant for 
 any particular perfect gas, the relations between the temperatures 
 and volumes are: 
 
 and 
 
 Again, for the relation between temperatures and pressures, 
 
 T P V P \P 
 * 1 * i r i i ^: 
 
 i 
 
 and 
 
 P l 
 
THEORETICAL HEAT CYCLES 387 
 
 The total external work done by the expansion ^of the gas from 
 V, to F 2 is 
 
 W = 
 
 The value of P as determined from the equation PF A =P 1 F 1 X is 
 
 P y A i.. i 
 
 p = 1 1 = p V V~ 
 yl 
 
 which, when substituted in the preceding equation, gives it the 
 form 
 
 w - py* 
 
 P F 
 
 
 Or, since P t V t * = P 2 F 2 ^, the second from the last equation 
 can be brought to the form 
 
 P,V, F/' 1 P 2 F 2 F/' 1 
 
 rrr _ 
 
 ~ 
 
 1 F- 1 X - 1 
 
 P 7 _ P 7 
 
 r l y 1 J 2 K 2 
 
 /t- 1 
 
 Whence, by substituting for P i V 1 its value RT V and for P 2 F 2 its 
 
 value RT 2 , 
 
 T T 
 W = R 
 
 A """ 
 
388 THE GAS ENGINE 
 
 The equation for the change of sensible heat in the gas is 
 S = C, (T t - 7\) 
 
 c 
 
 
 
 
 V P V } 
 l r l * l r l/J 
 
 which has a negative value for expansion of the gas. 
 
 A check on the computation can be made by use of the equation 
 
 S - - GW. 
 
 259. Comparison of Expansion and Compression Lines. 
 Fig. 125 shows the relative positions of the expansion lines of 
 a perfect gas whose initial condition is A } for expansion in 
 
 Constant Pressure 
 
 Adiabatic X-1.41 
 
 FIG. 125. 
 
 accordance with the four methods of expansion for which equa- 
 tions have just been developed. The expansion lines are respec- 
 tively for constant volume, constant pressure, for isothermal and 
 for adiabatic change. The initial condition of the ga is the same 
 in each case and is represented by the point A. The constant 
 
THEORETICAL HEAT CYCLES 
 
 389 
 
 volume and constant temperature lines are the same, for all gases, 
 perfect or imperfect. The isothermal line occupies the same 
 position for all perfect gases. The adiabatic line is generally 
 different for each gas, or more definitely, it has a different posi- 
 tion for each value of the ratio of the specific heat of constant 
 pressure to the specific heat of constant volume. This ratio has 
 been distinguished by the letter A in the notation. The adia- 
 batic line of expansion lies below the isothermal expansion line. 
 
 Isothermal 
 
 Constant Pressure 
 
 FIG. 126. 
 
 Fig. 126 shows the relative positions of the compression lines 
 of a perfect gas, starting in each case from the same initial 
 condition A. 
 
 260. Theoretically Perfect Otto Cycle. - - Fig. 127 shows 
 the pressure-volume diagram of a theoretically perfect Otto 
 cycle. 
 
 As applied to the internal-combustion motor, the initial state 
 of the combustible charge is represented by the point A. The 
 charge is compressed adiabatically from A to B. It is then 
 heated by its own total combustion, while the volume remains 
 constant at V b . During combustion the pressure rises to P c 
 at C with a corresponding temperature T c . The products of 
 combustion then expand adiabatically from V b back to the 
 initial volume V a , the condition at the completion of adiabatic 
 expansion being represented on the diagram by the point D. 
 Heat is then abstracted at constant volume V a till the pressure 
 
390 
 
 THE GAS ENGINE 
 
 falls to the initial value as represented by the point A and the 
 temperature is the same as that of the charge in its initial state. 
 The last change (the reduction of pressure and temperature at 
 constant volume) has an approximate equivalent in the actual 
 Otto cycle in the discharge of the burned gases from the cylinder 
 of the motor and the taking in of a new charge. 
 
 FIG. 127. 
 
 In order that the products of combustion, when brought to the 
 initial volume and pressure of the charge, V a and P a , shall have 
 a temperature the same as the initial temperature of the charge, 
 the conditions are, in general, that the specific heats of constant 
 pressure, C v and C p , of the burned gases shall be the same as those 
 of the combustible charge, and that the products of combustion 
 and the combustible mixture, when both are at the same tempera- 
 ture and pressure, shall have equal volumes.* 
 
 Since the introduction of a factor for the variation of specific 
 volume (at equal temperatures and pressures) due to combustion 
 has but a slight effect on the form of those of the equations already 
 written that apply to this cycle, such a factor /? will be introduced 
 for following out the cycle mathematically. And since the in- 
 troduction of different specific heats of the charge and of the 
 
 * See chapter on Combustion and Heat Values for contraction and expan- 
 sion of specific volume due to the chemical reactions of combustion. 
 
THEORETICAL HEAT CYCLES 391 
 
 products of combustion merely means the use of different 
 values of the specific heats and their ratios in part of the 
 equations that have been developed, different values of specific 
 heats will be used. The following section treats the cycle on 
 this basis. 
 
 261. Equations for Otto Cycle. In Fig. 127 the initial 
 pressure, volume, and temperature are P a , V a , and T a . The 
 same letters with subscripts b, c, and d are used to indicate the 
 corresponding values at the points B, C, and D on the diagram. 
 
 The factor /? = the ratio of the volume of the burned gases to 
 the initial volume of the combustible mixture when both are at 
 the same temperature and pressure = the ratio of the specific 
 volumes of the products and of the charge. 
 
 The specific heats, C v f and C p ', and the ratio of the latter to 
 the former = A' for the charge, have, in general, values that 
 differ from the corresponding values of C/', C p ", and \" for the 
 burned gases. The combustible mixture and the mixture of 
 burned gases are both assumed to be perfect gases. 
 
 The equations relate to a definite weight, as 1 pound, of the 
 fuel gas. 
 
 For adiabatic compression of the combustible charge from A 
 to B, 
 
 PV X ' = constant. 
 
 The work done on the gas during compresssion is 
 
 P V - - P V 
 
 W == b a a 
 
 X - 1 
 The heat stored in the gas during adiabatic compression is 
 
 S'-^ (P b V b - PJ a ) 
 = GW. 
 
39 2 THE GAS ENGINE 
 
 Combustion at constant volume of combustion space 
 
 
 c 
 ' 
 
 P - SP T-T b 
 
 / 7~ l ft P T 1 
 
 t JJ - b * b P*b * b 
 
 The work done is 
 
 W" = o. 
 
 The heat stored in the gas during combustion at constant 
 volume is 
 
 O// _ TT 
 
 For adiabatic expansion of the products of combustion from 
 C to D, 
 
 " = constant. 
 
 P V T 
 
 __ rp i ' o \ . * d' a __ *- d 
 
 _ P ALA* - 
 
 P *(v ' 
 
 The mechanical work done by the gas during adiabatic expan- 
 sion is 
 
 The heat abstracted from the gas during adiabatic expansion is 
 S '" = %7 ( p ' v ~ P * V J- 
 
 K 
 = GW". 
 
 Discharge of products of combustion : 
 
 No useful work is done during the discharge of the products 
 of combustion after they have expanded in the motor to the 
 
THEORETICAL HEAT CYCLES 393 
 
 initial volume Va of the charge. The portion of tlje heat, of that 
 added to and stored in the gas during compression and combus- 
 tion, which is still retained in the products of combustion at the 
 condition F a , Pd, Tj is therefore wasted so far as transformation 
 into mechanical energy by the motor is concerned. 
 
 The heat stored in the gas during adiabatic compression and 
 during combustion equals 
 
 S' + S" = GW + Hi. 
 
 The heat abstracted during adiabatic expansion equals 
 
 S'" = GW'". 
 
 The heat wasted is the difference between the quantities repre- 
 sented in the last two equations, and equals 
 
 H d = S' + S" - S'" 
 - GW + Hi - GW'" 
 = Hi-G (W" - W). 
 
 It may be noted that, on account of the difference between 
 the specific heats (by weight) of the charge and of the products 
 of combustion, the heat that would be abstracted frorp. the ex- 
 haust gases by cooling them to the initial temperature of the 
 charge will not be the same in amount, at the initial pressure, as 
 the wasted heat. The total heat in the charge and in the dis- 
 charged products above absolute zero temperature must therefore 
 be taken injto consideration to obtain the waste heat by equations 
 involving temperatures. The practical value of such equations 
 is slight. 1 \. 
 
 In cases where there is no change of specific heat the follow- 
 ing equation can be applied : 
 
 H d = C v " (T d - T a ). 
 
 Efficiency. The efficiency of the transformation of heat energy 
 into useful mechanical energy during this theoretical Otto cycle 
 
394 
 
 THE GAS ENGINE 
 
 is the ratio of (a), the difference between the total heat added to 
 the gas and that discharged to (b), the total heat added by com- 
 bustion. That is, 
 
 H i - H d 
 Efficiency = ^~ 
 
 **i 
 
 The efficiency can also be expressed as the ratio between the 
 heat equivalent of the mechanical work done and the total heat 
 of combustion. Thus, 
 
 G (W" f - W) 
 Efficiency = ' 
 
 262. Efficiency as Affected by Variation of Compression. - 
 It has been stated that increase of the pressure of compression 
 increases the efficiency of an internal-combustion motor as deter- 
 mined in the actual operation of the motor. The reason for this 
 can be shown by the aid of the theoretical pressure-volume 
 diagram. 
 
 FIG. 128. 
 
 In Fig. 128, suppose that the theoretical pressure- volume 
 diagram is at first as shown by the full-line diagram. The 
 
THEORETICAL HEAT CYCLES 
 
 395 
 
 mechanical work done is represented by the area ,4 BCD. Now 
 suppose that, starting with the same amount of charge at the same 
 condition A as before, the compression is carried to the point E 1 
 on the adiabatic AB, so that the compressed volume of the charge 
 is smaller than on the full-line diagram. When the heat added, 
 as by combustion, is the same as before, the pressure will rise on 
 account of the added heat to the point C', which is on an extension 
 of the adiabatic line CD. The expansion will then follow the 
 line C'CD. The new diagram with the higher compression 
 ratio will be larger than the first one by the area BB'C'CB, which 
 represents a corresponding increase of work over that of the first 
 diagram. 
 
 The ratio of the efficiencies of the two cases will be the same 
 as that of the areas B'C'DAB' and BCDAB, since the same 
 amount of heat is added by combustion in each case. 
 
 263. Effect of Variation of Specific Volume on Account of 
 Combustion. In Fig. 129 the full-line diagram ABCD is the 
 
 theoretical form for a combustible mixture whose specific volume 
 does not change on account of combustion. Another gas which 
 has the same specific heats and heat value but whose specific 
 volume contracts on account of the chemical action of combustion, 
 will give the diagram ABC'D'AB, in which the expansion line 
 C'D f falls below that of the gas that has no contraction of specific 
 
396 
 
 THE GAS ENGINE 
 
 volume on account of combustion. The mechanical work that 
 the gas whose specific volume contracts by combustion will do is 
 therefore less per unit of its heat value, and its efficiency will 
 consequently be less than that of one that undergoes no con- 
 traction. 
 
 On the other hand, a gas whose specific volume increases by 
 combustion will do more work, other conditions being equal, 
 than one whose specific volume does not change by combustion. 
 
 (Increase of specific volume by combustion means that the volume 
 of the products of combustion is greater than that of the com- 
 .bustible mixture, both at the same temperature and pressure, as 
 has been stated before.) 
 
 The effect of specific expansion of a gas during combustion is 
 indicated by the dotted line in Fig. 130. 
 
 264. Effect of Different Specific Heats of Combustible Gases 
 and of Products of Combustion. Fig. 131. The full-line dia- 
 gram is for a perfect gas whose products of combustion have the 
 same specific heats as the combustible charge. Another com- 
 bustible gas having the same specific heats and heat value but 
 whose products have higher specific heats, will give the diagram 
 whose expansion is represented by the dotted line. It will be 
 
THEORETICAL HEAT CYCLES 
 
 397 
 
 seen that the increased specific heat has the effecj of decreasing 
 the area of the diagram. The efficiency is correspondingly 
 decreased. 
 
 265. Effect of Change of Ratio ^ of Specific Heats by Com- 
 bustion. If the ratio of the specific heat of constant pressure to 
 
 Q 
 
 that of constant volume, = A, is less for the products of com- 
 
 C v 
 
 bustion than for the combustible mixture, then the expansion 
 line will not drop so rapidly as when the ratio is the same in both 
 
 cases. 
 
 c 
 
 I 
 
 This is indicated in Fig. 132, in which the full lines form the 
 diagram for the same value of the ratio X in both the charge 
 
398 
 
 THE GAS ENGINE 
 
 and the products. The dotted line CD' is for products of com- 
 bustion having a lower value of X than its value for the charge. 
 266. Effect of Imperfect Gas on the Theoretical Otto Cycle. - 
 The products of combustion of the gases used in internal-com- 
 bustion motors do not have constant values of their specific heats. 
 The specific heat increases with increase of temperature, and, so 
 far as is known, decreases with increase of pressure. The net 
 result is generally that the specific heats are higher as the tem- 
 perature and pressure both increase on account of combustion. 
 While not positively known, it will be assumed for the purpose of 
 
 Q 
 
 illustration that the ratio = X decreases as the products of 
 
 C v 
 combustion expand. 
 
 The effect of these departures from the properties of a perfect 
 gas is illustrated in Fig. 133. The full line represents the 
 
 theoretical pressure-volume diagram for a perfect gas. The 
 dotted line is the expansion line for an imperfect gas having the 
 properties just set forth. 
 
 On account of the increased specific heat of constant volume, 
 the pressure rises only to C f instead of C during combustion. It 
 may be assumed that the specific heats of the perfect gas and of 
 the imperfect gas are equal at B. 
 
THEORETICAL HEAT CYCLES 399 
 
 The decreasing value of ^ as the gases expand causes the 
 line C'D' to become more nearly horizontal than a corre- 
 sponding line for a constant value of A, so that the terminal 
 pressure at D r is higher than that for a perfect gas expanding 
 from C'. 
 
 267. Other Causes that Modify the Theoretical Otto Cycle. - 
 The principal causes, in addition to those already cited, that 
 modify the theoretical Otto cycle in its practical application 
 are : 
 
 1. Heat transfer between the cylinder walls and the gas. 
 
 2. Combustion is not at constant volume. 
 
 3. Discharge of products of combustion is not at constant 
 
 volume of cylinder space. 
 
 4. Leakage of gas from motor cylinder around the piston, 
 
 valves, etc.). 
 
 Under normal conditions of operation with a water-cooled or 
 oil-cooled cylinder, the charge of gas receives heat from the 
 metal of the cylinder at least during the early part of compression. 
 As the temperature increases during compression, it is possible 
 that the gas has a higher temperature than the metal during the 
 latter part of compression and thus loses heat to the metal. 
 During combustion and at least the early part of expansion 
 heat is abstracted from the gas by the metal. Whether this 
 abstraction of heat from the gas continues till the exhaust 
 port is opened depends on the temperature of the charge, the 
 extent of expansion, and the temperature of the metal. It 
 is probable that the metal abstracts heat from the gas during 
 all or nearly all of the expansion stroke under the usual condi- 
 tions of working. 
 
 In an air-cooled motor working with a very hot cylinder the 
 charge probably receives heat from the metal during all of the 
 compression stroke, and heat is abstracted from the products 
 during at least the early part of expansion. 
 
 The effects of the other three causes are shown in the indicator 
 cards from practice in the chapter under that heading. 
 
400 
 
 THE GAS ENGINE 
 
 268. Modified Theoretical Otto Cycle. Fig. 134 shows the 
 theoretical type of diagram that gives the highest thermodynamic 
 efficiency for cycles of the nature of the Otto. The initial volume 
 of charge is V a at the pressure P a . It is compressed adiabatically 
 to V bJ heated by combustion at constant volume V b to T C P C , and 
 then expanded adiabatically till the pressure falls to the initial 
 pressure P a at the volume V e . 
 
 Constant 
 A Pressure E ^o A 
 
 FIG. 134. 
 
 Taking P a = P e = atmospheric pressure, the line AE is a 
 line of atmospheric pressure. This corresponds in practice to 
 the displacement of the products against atmospheric resistance 
 while the piston moves from E to A. The heat wasted is that 
 necessary to increase the volume of the gas from V a to V e at 
 constant (atmospheric) pressure. The area of the diagram is 
 larger than that in which the initial and final volumes are equal, 
 by the amount ADEA. 
 
 This diagram is of the same nature as those of a four-stroke 
 Otto cycle motor that cuts off the admission of combustible 
 mixture completely when the piston has moved only part way on 
 the suction stroke. (See Fig. 107.) 
 
 While this cycle has a high thermodynamic efficiency in relation 
 to indicated power, it does not have a correspondingly high 
 efficiency for the conversion of heat into delivered mechanical 
 energy which must take into account the mechanical efficiency 
 of the machine (motor). At some point on the expansion line 
 CDE the pressure falls to an amount that is just sufficient to 
 
THEORETICAL HEAT CYCLES 
 
 401 
 
 overcome the mechanical friction of the motor. 4^ er this point 
 is reached there is no gain in the amount of power delivered by 
 the motor during the remainder of the expansion, but an actual 
 loss of power occurs if expansion is carried out beyond the point 
 just mentioned. 
 
 A Constant Y 
 Pressure 
 
 FIG. 135. 
 
 In Fig. 135, if X is the point where the driving effort of the 
 expanding gas and the frictional resistance of the machine just 
 balance each other, then this diagram is the one for the maximum 
 motor efficiency at a fixed compression pressure. (See Fig. 107 
 for method of approximating this diagram in practice.) 
 
 Constant 
 
 Constant !_ 
 
 _ -'C 
 
 A Pressure 
 
 FIG. 136. 
 
 269. Theoretical Brayton Cycle. Fig. 136. This cycle 
 theoretically consists in adiabatically compressing a charge of 
 
402 THE GAS ENGINE 
 
 non-combustible gas from the condition A to B, and then main- 
 taining a constant pressure during the early part of the outstroke 
 of the piston by adding more gas which is combustible and burns 
 as it enters the motor cylinder, thus increasing the temperature 
 of the charge as the volume in the cylinder increases. The 
 addition and burning of gas are stopped at C, and the contents 
 of the cylinder expand adiabatically to the end of the stroke. 
 The burned gas is then expelled, while the volume of the cylinder 
 space remains constant, which completes the cycle. 
 
 The expansion may be carried to any point D on the adia- 
 batic DD' ', and the exhaust valve kept open on the compres- 
 sion stroke till the point A, where compression is to begin, is 
 reached. 
 
 270. General Equations for Thermodynamic Change. In 
 the preceding discussion the equation PV* constant has been 
 used for adiabatic expansion, in which X is the ratio of the specific 
 heat of constant pressure to that of constant volume. This 
 equation can be extended to more general application by making 
 the exponent such that it can be assigned any value. This is done 
 in the equation, 
 
 PV n = constant, 
 
 in which any value may be assigned to n. 
 
 If n = 1 then the equation applies to isothermal expansion or 
 compression. By making n = o the equation for constant 
 pressure is obtained, since F = 1 and therefore PV = constant. 
 When n = oo the equation becomes that for constant pressure, 
 since F* = oo . 
 
 For any finite value of n, equations can be developed for 
 determining points on the expansion and compression lines of a 
 perfect gas. 
 
 In view of the fact that there are so many modifying factors 
 met with in the application of these equations to practical con- 
 ditions, as has been pointed out in relation to the Otto cycle, they 
 are of little or no use in practice. 
 
 271. Other "Thermodynamic Cycles. It will doubtless readily 
 be seen that by combining different lines of expansion and com- 
 
THEORETICAL HEAT CYCLES 403 
 
 pression, an infinite number of thermodynamic Cycles can be 
 obtained. In the present state of the internal-combustion motor 
 art none of the cycles except those that have been mentioned 
 seem to find application however, and there appear to be such 
 great difficulties in utilizing efficiently cycles other than the ones 
 now in use as to prevent their early application. 
 
CHAPTER XXI. 
 RESULTS OF TRIALS. 
 
 272. Introductory. The matter relative to tests which is 
 given in this chapter has been selected on account, on the one 
 hand, of its covering a great variety of bituminous coals and 
 lignites, and on the other hand as being representative of modern 
 gas engine practice in regular service. Also because two kinds of 
 gas producers are brought into consideration. In one case a con- 
 tinuous updraught producer was used, and in the other a pair 
 of intermittent downdraught producers. 
 
 273. United States Government Tests at St. Louis. These 
 tests were made largely for the purpose of determining the 
 suitability of various bituminous coals, lignites and peat for con- 
 version into gas for combustion motor use. A great number of 
 different coals and lignites were tested. The trials were so 
 extensive, complete and fully reported as to be the most valuable 
 information in this connection. A very small proportion of the 
 mass of data will be presented. 
 
 The gas producer used was of the continuous, updraught pres- 
 sure type, of the general form of Fig. 114. The gasification 
 chamber was about 7 feet diameter (inside) at the fire zone. The 
 producer was rated at 250 horsepower capacity. 
 
 The gas engine was of the three-cylinder, single-acting, ver- 
 tical four-cycle type, rated 235 horsepower at 200 r.p.m. The 
 engine cylinders were 19 inches diameter and the stroke 22 
 inches. 
 
 A gas J:ank 20 feet diameter, 13 feet high and of 4000 cubic 
 feet capacity was used in connection with the producer. 
 
 Steam for producing the blast and aiding in the gasification 
 of the fuel was taken from separate boilers. Power was used for 
 driving the automatic fuel-feeding device attached to the producer, 
 and also for driving the centrifugal tar extractor. The items in 
 
 404 
 
RESULTS OF TRIALS 405 
 
 the tables under headings containing the words " equivalent used 
 by producer plant" include the energy of the steam supplied and 
 that used for driving the apparatus auxiliary to the producer, 
 including the tar extractor. 
 
 Tables XII to XVI, compiled from the report, and Figs. 137 
 and 138, reproduced from the report, give several of the items of 
 the tests. 
 
 Test 29 is notable on account of running continuously for 562 
 hours. 
 
 The fuels used in tests 71-78, lignites, peat, and bone coals, 
 show what can be done with fuels that have been practically 
 unused in this country heretofore. Bone coal is ordinarily 
 thrown out as waste at the mines. Some of that tested was com- 
 posed of so much hard, stony matter that a hammer would strike 
 fire from it. The hand-picked bone coal was of larger sizes than 
 the run of such coal and therefore was not as rich in combustible 
 matter as the run (of bone) on account of the softer parts break- 
 ing off in small pieces when the bone was thrown aside from the 
 tipple. 
 
 The tar collected from the producer gas, as shown in Table 
 XIII, represents a considerable loss of the heat value of the coal 
 and a consequent reduction of the efficiency of the producer, as 
 these tests were carried out. The tar was not utilized so far as 
 the production of power from the coal was concerned. 
 
 The heat values of the tars from the different fuels naturally 
 vary greatly on account of the different compositions of the tars. 
 Some tars are black and heavy as compared with others. The 
 brown tar from the lignites is generally much lighter than the 
 black from bituminous coal. The heavy tars generally have higher 
 heating values than the lighter ones, as they occur in connection 
 with producer gas manufacture. 
 
 The gain in economy by breaking up the tar during the gas- 
 making process into compounds that are permanent gases, or of 
 providing some means of usefully burning the tar, will appear 
 when the amount formed in some cases is noted as given in the 
 table. 
 
406 
 
 THE GAS ENGINE 
 
 10.05 12.05 2.05 4.05 6.05 8.05 10 05 12.05 2.05 
 
 6.05 8.05 10.05 12.05 
 
 FIG. 137. 
 
 GRAPHIC LOG SHEET, PRODUCER GAS TEST, IOWA NO. 2 COAL. 
 From " Report on Coal-Testing Plant, " U. S. Geological Survey, 1906. 
 
 1. Manometer No. i at gas meter. 
 
 2. Manometer No. 2 at gas meter. 
 
 3. B.t.u. of gas by analysis. (Higher value.) 
 
 4. B.t.u. of gas by calorimeter. (Higher value.) 
 
 5. Rev. per min. of engine. 
 
 6. Temperature of gas leaving producer 
 
 7. Amperes, generator load. 
 
 8. H.p. of auxiliary motor. 
 
 9. H.p. output of generator. 
 
 10. Temperature of gas at meter. 
 
 11. Volts, generator load. 
 
 12. Water used by producer plant 
 
 13. Coal consumed by producer. 
 
 14. Cubic feet of gas produced. 
 
RESULTS OF TRIALS 
 
 407 
 
 PERCENTAGE OF CHEMICAL COMPOSITION OF COAL. 
 
 WEST VIRGINIA #12 
 WEST VIRGINIA #10 
 WEST VIRGINIA #12 BRIQ. 
 PENNSYLVANIA #2 
 WtST VIRGINIA #8 
 WEST VIRGINIA #6 
 PENNSYLVANIA #1 
 ARKANSAS #2 
 
 ARKANSAS #4 BRIQ. 
 WEST VIRGINIA #9 
 WEST VIRGINIA #8 
 WEST VIRGINIA #11 
 PENNSYLVANIA #-4 
 ARKANSAS #1 BRIQ. 
 
 WEST VIRGINIA #1 
 ARKANSAS #3 
 
 KENTUCKY #1 
 
 WEST VIRGINIA #1 
 ARKANSAS #5 
 
 ARKANSAS #4 BRIQ. 
 WEST VIRGINIA #4 
 ARKANSA8#2 BRIQ. 
 WEST VIRGINIA #5 
 ARKANSAS #1 
 
 MISSOURI #4 
 
 WEST VIRGINIA #3 
 INDIANA #1 BRIQ. 
 KANSAS#2 WASHED 
 WEST VIRGINIA #2 
 PENNSYLVANIA'S BRIQ. 
 INDIAN TERRITORY #2 
 
 KANSAS #1 
 
 INDIANA #1 WASHED 
 ALABAMA #1 BRIQ. 
 ARKANSAS #3 BRIQ. 
 KENTUCKY #2 
 
 ALABAMA #1 
 
 KANSAS #3 
 
 ILLINOIS #3 
 
 MISSOURI rl WASHED 
 KANSAS #5 
 
 COLORADO #1 
 
 INDIAN TERRITORY#3 
 INDIAN TERRITORY #1 
 NEW MEXICO # 1 
 
 KENTUCKY #3 
 
 KANSAS #3 
 
 KENTUCKY #4 
 
 MISSOURI #3 WASHED 
 ILLINOIS #4 
 
 KENTUCKY#2 BRIQ. 
 ILLINOIS #4 
 
 ALABAMA 0-2 
 
 WYOMING #1 
 
 ILLINOIS #2 WASHED 
 KANSAS #1 
 
 IOWA #4 BRIQ. 
 MISSOURI '1 BRIQ. 
 INDIANA $-2 
 
 INDIAN TERRITORY #4 
 NEW MEXICO#2 BRIQ. 
 
 MISSOURI 
 
 KANSAS 
 
 IOWA 
 
 KANSAS 
 
 ILLINOIS 
 
 NEW MEXICO 
 
 IOWA 
 
 ILLINOIS 
 
 TEXAS 
 
 MISSOURI 
 
 IOWA 
 
 IOWA 
 
 MISSOURI 
 
 IOWA 
 
 NORTH DAKOTA 
 
 WYOMING 
 
 MISSOURI 
 
 #1 
 
 #4 
 
 I? 
 
 #2 
 #4 
 
 i; 
 
 #a 
 
 $: 
 
 #2 
 #1 
 #1 
 #2 
 #3 
 
 FIG. 138. 
 
 From "Report on Coal -Testing Plant," 
 U. S. Geological Survey, 1906. 
 
408 
 
 THE GAS ENGINE 
 
 TABLE XII. 
 
 Average Compositions of Producer Gases from Various 
 Bituminous Coals and Lignites.* 
 
 (See also Tables XIII, XIV, XV, XVI, and Fig. 138.) 
 All gas made in the same producer of the continuous up-draught pressure type. 
 
 Num- 
 ber. 
 
 Name of Coal or Lignite. 
 
 Average Composition of Gas by Volume. 
 Per cent. 
 
 CO2 
 
 2 
 
 CO 
 
 H 2 
 
 CH 4 
 
 N 2 
 
 I 
 
 Alabama No. 2 ) 
 Clean and hard. ) 
 
 8.16 
 
 0. 10 
 
 16.65 
 
 7.20 
 
 5-64 
 
 62. 24 
 
 2 
 
 Colorado No. i ) 
 
 10. II 
 
 55 
 
 17-38 
 
 11.05 
 
 5.00 
 
 55-9<> 
 
 Black lignite. ) 
 
 t 3 
 
 Illinois No. 3 
 
 IO. C,3 
 
 i 5 ; 
 
 i 1 ?. 31 
 
 8. 
 
 4.46 
 
 61 . 19 
 
 1 O 
 
 t 4 
 
 Illinois No 4 
 
 oo 
 
 972 
 
 o 
 . 12 
 
 o o 
 
 I C 12 
 
 OD 
 
 o 08 
 
 6. oo 
 
 rn 06 
 
 1 *f 
 
 ts 
 
 Indiana No. i 
 
 / 
 
 9.89 
 
 25 
 
 A o ** 
 14. 10 
 
 y y" 
 9-5 6 
 
 6.08 
 
 oV V'' 
 60-13 
 
 
 f 6 
 
 Indiana No. 2 
 
 11.80 
 
 .07 
 
 1 1 46 
 
 10. 60 
 
 6. 10 
 
 en 07 
 
 F 
 
 7 
 
 Indian Territory No. i 
 
 8-25 
 
 / 
 
 . ii 
 
 J. L , f.W 
 19-39 
 
 7.69 
 
 4-92 
 
 ov y / 
 59.65 
 
 8 
 
 Indian Territory No. 4 
 
 7.29 
 
 .236 
 
 17.636 
 
 10.427 
 
 6.30 
 
 58.109 
 
 9 
 
 Iowa No 2 
 
 10.057 
 
 .171 
 
 12.571 
 
 9-529 
 
 7.671 
 
 60.000 
 
 
 10 
 
 Kansas No. 5 ) 
 Fine slack, good prod'r coal ) 
 
 10.267 
 
 133 
 
 I2.4O 
 
 9-05 
 
 7-417 
 
 60 -733 
 
 tn 
 
 Kentucky No. 3 
 Good, hard producer coal ) 
 
 10.87 
 
 .29 
 
 12-45 
 
 10.92 
 
 6.52 
 
 58.95 
 
 + 12 
 
 Missouri No. 2 
 
 12.07 
 
 . 20 
 
 IO ^ 3 
 
 7 6? 
 
 6 33 
 
 63 23 
 
 1 * 
 
 fll 
 
 Montana No. i 
 
 / 
 
 9.04 
 
 36 
 
 w< oo 
 18 67 
 
 / "o 
 
 9OO 
 . w 
 
 oj 
 
 4 8d 
 
 W J *J 
 CQ jo 
 
 1 A .3 
 
 ti4 
 
 North Dakota No. 2 ) 
 Brown lignite. ) 
 
 V V4 T 
 
 8.69 
 
 o 
 
 2 3 
 
 " **f 
 
 20.90 
 
 H-33 
 
 *T ^T- 
 
 4.85 
 
 0V * Aw 
 
 51 .02 
 
 ti5 
 
 Texas No. i ) 
 
 TI.IO 
 
 . 22 
 
 14-43 
 
 10.54 
 
 7-85 
 
 56.22 
 
 Brown lignite. ) 
 
 16 
 
 Texas No. 2 ) 
 
 9.60 
 
 . 20 
 
 18.22 
 
 9-63 
 
 4.81 
 
 57-53 
 
 Brown lignite. ) 
 
 !? 
 
 West Virginia No. i 
 
 IO.50 
 
 . 10 
 
 14-34 
 
 2.81 
 
 5-56 
 
 66.69 
 
 18 
 
 West Virginia No. 4 
 
 10. 16 
 
 2 4 
 
 1 5.82 
 
 1 1 . 16 
 
 3 74 
 
 58.88 
 
 19 
 
 West Virginia No. 7 
 
 9.617 
 
 .084 
 
 *3 ' 
 
 12-75 
 
 10.308 
 
 j /T- 
 6.758 
 
 60.483 
 
 
 20 
 
 West Virginia No. 8 
 
 10.327 
 
 .218 
 
 11.927 
 
 9-454 
 
 6.40 
 
 61 .672 
 
 21 
 
 West Virginia No. 9 
 
 10.40 
 
 . 20 
 
 ii . 70 
 
 9-55 
 
 6.60 
 
 59-55 
 
 22 
 
 West Virginia No. 9 
 
 8.90 
 
 33 
 
 14-77 
 
 9.508 
 
 6.65 
 
 59-856 
 
 t*3 
 
 West Virginia No. 12 
 
 IO. 34 
 
 . 12 
 
 14. 21 
 
 12.08 
 
 4.61 
 
 ^7 71; 
 
 1 O 
 
 24 
 
 Wyoming No. 2 
 
 W O T^ 
 
 10. 21 
 
 59 
 
 15.46 
 
 10.79 
 
 S-S 2 
 
 o / / j 
 
 57-43 
 
 * From " Report on Coal-Testing Plant," United States Geological Survey, 
 1906. See pages 407 and 409 for composition of coal, 
 f Gas producer hopper leaked during these tests. 
 
RESULTS OF TRIALS 
 TABLE XIII. 
 
 Proximate Analyses of Bituminous Coals and Lignites. 
 Temperatures and Tar Products of Gasification.* 
 
 (See also Tables XII, XIV, XVI, and Fig 138.) 
 
 409 
 
 Number. 
 
 Average Composition of Coal. 
 Per cent. 
 
 Total 
 Coal Con- 
 sumed in 
 Producer. 
 Pounds. 
 
 Total Tar 
 Collected. 
 
 Aver- 
 age 
 Temp, 
 of Gas 
 Leav- 
 ing 
 Pro- 
 ducer. 
 Deg. 
 Fahr.f 
 
 Mois- 
 ture. 
 
 Vola- 
 tile 
 Matter. 
 
 Fixed 
 Car- 
 bon. 
 
 Ash. 
 
 Sul- 
 phur. 
 
 i 
 
 3-76 
 20.24 
 7.62 
 12-43 
 
 II. 5! 
 
 8.72 
 
 5.00 
 
 9.00 
 
 16.69 
 4.35 
 
 7.28 
 
 1 1. 60 
 11.40 
 
 39-56 
 
 33-5 
 33-7i 
 1.61 
 1.99 
 2.99 
 2.66 
 2.66 
 
 2.22 
 1-43 
 
 9-44 
 
 33-45 
 32.26 
 30.87 
 
 3 2 -65 
 36.04 
 39.60 
 36.51 
 33-96 
 31.42 
 
 31-97 
 38.57 
 35-28 
 
 34-55 
 
 27.78 
 
 32.34 
 29.25 
 36-85 
 28.89 
 
 21 . 19 
 
 32.58 
 32.00 
 
 3I-5 
 18.93 
 
 35- 02 
 
 53-29 
 41.65 
 
 51-78 
 45-70 
 42.37 
 41-95 
 49-98 
 40.68 
 
 31 19 
 52.43 
 45.16 
 38.28 
 
 43-31 
 26.30 
 23.80 
 29.76 
 55-40 
 60.30 
 69.15 
 59-oo 
 59.61 
 59-83 
 73-19 
 34.82 
 
 9-50 
 5-85 
 9-73 
 9.22 
 10. 08 
 9-73 
 8-5! 
 16.36 
 
 2O-. 70 
 11.25 
 
 8-99 
 14.84 
 10.74 
 6.36 
 10.36 
 7.28 
 6. 14 
 8.82 
 6.67 
 5-76 
 
 5-73 
 6.90 
 
 6-45 
 20.72 
 
 0.86 
 O.6o 
 1.69 
 1.41 
 2.61 
 
 4.23 
 
 i-43 
 4.12 
 
 5-50 
 3-oo 
 3-86 
 4-56 
 1.72 
 
 -93 
 0.63 
 
 o-53 
 0.87 
 
 o-79 
 0.92 
 0.94 
 
 I.OO 
 
 0.79 
 0.95 
 3-91 
 
 13350 
 I0 933 
 10500 
 10500 
 11700 
 6900 
 1 1 200 
 6300 
 
 4833 
 4000 
 
 IIIOO 
 
 33o 
 
 IO2OO 
 13800 
 12800 
 9050 
 6900 
 2100 
 6OOO 
 6900 
 1300 
 600O 
 8lOO 
 I2IOO 
 
 ? 
 ? 
 60 gal. 
 
 75 gal- 
 70 gal. 
 
 p 
 
 2. 5 bbl. 
 
 50 gal. 
 50 gal. 
 ? 
 100 gal. 
 
 ? 
 ? 
 
 5 gal- 
 150 gal. 
 60 gal. 
 
 p 
 p 
 ? 
 
 75 gal. 
 120 gal. 
 50 gal. 
 50 gal. 
 60 gal. 
 
 p 
 650 
 
 753 
 882 
 
 975 
 914 
 ? 
 686 
 
 893 
 840 
 
 p 
 
 883 
 
 738 
 p 
 
 > 
 
 559 
 768 
 804 
 1228 
 847 
 752 
 1064 
 898 
 680 
 
 2 
 
 7 . . 
 
 
 e 
 
 6 . 
 
 7 
 8 
 
 9 
 10 
 
 n 
 
 12 
 
 13- 
 
 14 
 
 I<r 
 
 16 . 
 
 17 
 
 18 
 
 19 
 
 20 
 21 
 22 '. 
 23 . . 
 
 24. 
 
 
 * Compiled from " Report on Coal 
 Survey, 1906. 
 
 f Temperature of gas taken in main 
 
 -Testing Plant," United States Geological 
 gas flue near producer. 
 
4io 
 
 THE GAS ENGINE 
 
 TABLE 
 
 Rate of Gasification and Average Heat Values of Producer 
 
 (See also Tables XII, XIII, XV, XVI, 
 
 All gas made in the same producer of the continuous, updraught 
 
 at 62 F. and 14.7 pounds 
 
 Number. 
 
 Coal per Hour. Pounds. 
 
 Consumed in Producer. 
 
 Equivalent Used by Producer Plant. 
 
 Coal as 
 Fired. 
 
 Dry Coal. 
 
 Combus- 
 tible. 
 
 Coal as 
 Fired. 
 
 Dry Coal. 
 
 Combustible . 
 
 a 
 
 b 
 
 c 
 
 d 
 
 e 
 
 / 
 
 g 
 
 i 
 
 310-5 
 
 299.0 
 
 280.0 
 
 341-4 
 
 328.7 
 
 306.8 
 
 2 
 
 3 6 4-4 
 
 290.7 
 
 269.3 
 
 428.4 
 
 341-7 
 
 316.6 
 
 t3 
 
 35 - 
 
 323-3 
 
 289.3 
 
 386.0 
 
 356.7 
 
 319.2 
 
 t4 
 
 350-1 
 
 306.3 
 
 274.1 
 
 398.2 
 
 348-5 
 
 3II-9 
 
 ts 
 
 394-5 
 
 349-3 
 
 309-5 
 
 434-6 
 
 384.8 
 
 341-0 
 
 t6 
 
 300.0 
 
 274.0 
 
 244.8 
 
 338-o 
 
 312.0 
 
 278.8 
 
 7 
 
 361 .0 
 
 344-0 
 
 312.0 
 
 392-7 
 
 374-0 
 
 339-3 
 
 8 
 
 278.0 
 
 253-2 
 
 207.8 
 
 312-5 
 
 284.6 
 
 233-6 
 
 9 
 
 3 62 -5 
 
 302.5 . 
 
 227.5 
 
 408.4 
 
 340.7 
 
 256. 2 
 
 10 
 
 307.8 
 
 294-3 
 
 259.8 
 
 338.4 
 
 323-6 
 
 285.7 
 
 tn 
 
 370.0 
 
 343-3 
 
 310.0 
 
 410.8 
 
 381-2 
 
 344-2 
 
 tl2 
 
 346.5 
 
 306.0 
 
 255-0 
 
 384.5 
 
 339-6 
 
 283.0 
 
 ti3 
 
 456.5 
 
 404 5 
 
 355-8 
 
 506.8 
 
 449.1 
 
 395-o 
 
 tu 
 
 460.0 
 
 278.0 
 
 249.0 
 
 510.0 
 
 308.0 
 
 275-8 
 
 fis 
 
 590.0 
 
 393-o 
 
 33 2 -o 
 
 660.0 
 
 439-5 
 
 371-3 
 
 16 
 
 468.0 
 
 310-3 
 
 276.2 
 
 5I9-5 
 
 344-4 
 
 306.6 
 
 i? 
 
 287.5 
 
 283.0 
 
 265-5 
 
 320.6 
 
 3I5-6 
 
 296.1 
 
 18 
 
 233-o 
 
 229.0 
 
 208.0 
 
 262.8 
 
 258.2 
 
 234-5 
 
 19 
 
 269.9 
 
 256.9 
 
 239.1 
 
 299.2 
 
 290.2 
 
 270. i 
 
 20 
 
 328.6 
 
 320.8 
 
 301 . i 
 
 364-7 
 
 355-i 
 
 334-1 
 
 21 
 
 300.0 
 
 290.0 
 
 274.9 
 
 328.9 
 
 320.1 
 
 301.4 
 
 22 
 
 250.0 
 
 244-5 
 
 227.0 
 
 284.8 
 
 278-5 
 
 258.6 
 
 t2 3 
 
 270.0 
 
 266.1 
 
 248.7 
 
 34-9 
 
 300-5 
 
 280.9 
 
 24 
 
 403.2 
 
 365-3 
 
 281.6 
 
 459-8 
 
 416.5 
 
 321.1 
 
 * Partly from " Report on Coal -Testing 
 f Gas producer hopper leaked during 
 J Lower heat values computed by the 
 
RESULTS OF TRIALS 
 
 XIV. 
 
 Gases from Various Bituminous Coals and Lignites.* 
 
 and Fig. 138.) 
 
 pressure type, about 7 feet inside diameter at fire zone, 
 per square inch pressure. 
 
 Gas taken 
 
 British Thermal Units, Higher Heat Values. 
 
 B.t.u. per 
 Cu. Ft. of 
 Gas Computec 
 from Average 
 Chemical An- 
 alyses. Lower 
 Value. J 
 
 Number. 
 
 Coal as 
 Fired per 
 Pound . 
 
 Dry Coal 
 per Pound. 
 
 Combus- 
 tible per 
 Pound. 
 
 Gas from 
 one Pounc 
 Dry Coal 
 Consumed 
 in Prod'r. 
 
 Per Cu. 
 Ft. of 
 Gas. 
 
 k 
 
 i 
 
 7 
 
 k 
 
 I 
 
 m 
 
 n 
 
 12865 
 
 13365 
 
 14820 
 
 9000 
 
 149.2 
 
 I2 5 
 
 i 
 
 9767 
 
 12245 
 
 13210 
 
 7860 
 
 149.0 
 
 i33 
 
 2 
 
 12046 
 
 13041 
 
 14506 
 
 8330 
 
 ' 154.8 
 
 "3 
 
 3 
 
 11237 
 
 12834 
 
 14344 
 
 8840 
 
 I5I-5 
 
 J3 1 
 
 4 
 
 "534 
 
 13037 
 
 14720 
 
 7730 
 
 J 53-7 
 
 127 
 
 5 
 
 11822 
 
 12953 
 
 14500 
 
 10140 
 
 159-3 
 
 122 
 
 6 
 
 12787 
 
 !3455 
 
 14800 
 
 8620 
 
 159.2 
 
 I2 9 
 
 7 
 
 10364 
 
 11392 
 
 13890 
 
 9980 
 
 161. i 
 
 143 
 
 8 
 
 8735 
 
 10489 
 
 1395 
 
 9300 
 
 160. 2 
 
 136 
 
 9 
 
 12836 
 
 13421 
 
 15200 
 
 10500 
 
 167.2 
 
 132 
 
 10 
 
 12283 
 
 13226 
 
 14650 
 
 8610 
 
 155-9 
 
 130 
 
 n 
 
 10505 
 
 11882 
 
 14280 
 
 8820 
 
 140.0 
 
 113 
 
 12 
 
 i575 
 
 H934 
 
 13580 
 
 6580 
 
 160.8 
 
 127 
 
 13 
 
 6802 
 
 n 2 55 
 
 12600 
 
 7830 
 
 188.5 
 
 J 5 2 
 
 14 
 
 7267 
 
 10928 
 
 12945 
 
 7260 
 
 169.7 
 
 144 
 
 15 
 
 7348 
 
 11086 
 
 12450 
 
 8060 
 
 156.2 
 
 130 
 
 16 
 
 14166 
 
 14396 
 
 15350 
 
 9260 
 
 144.4 
 
 104 
 
 i7 
 
 13918 
 
 14202 
 
 15600 
 
 11610 
 
 143-2 
 
 117 
 
 18 
 
 14283 
 
 14720 
 
 15800 
 
 13140 
 
 154.2 
 
 132 
 
 19 
 
 14168 
 
 14558 
 
 15470 
 
 9070 
 
 i55-i 
 
 133 
 
 20 
 
 UI95 
 
 14580 
 
 15500 
 
 8150 
 
 151.0 
 
 131 
 
 21 
 
 14224 
 
 14548 
 
 15650 
 
 11380 
 
 160.5 
 
 134 
 
 22 
 
 14614 
 
 14825 
 
 15860 
 
 10150 
 
 142.5 
 
 124 
 
 23 
 
 9650 
 
 10656 
 
 13820 
 
 6168 
 
 151.0 
 
 130 
 
 24 
 
 Plant," United States Geological Survey, 1906. 
 
 these tests. 
 
 writer, using heat values given in Table VII. 
 
412 
 
 THE GAS ENGINE 
 
 TABLE XV. 
 
 Cubic Feet of Gas from Various Bituminous Coals 
 
 and Lignites. 1 * 
 
 (See also Tables XII, XIII, XIV, XVI, and Fig. 138.) 
 All gas made in the same producer of the continuous updraught pres- 
 sure type. Gas at 62 F. and 14.7 pounds per square inch pressure. 
 
 
 Cubic Feet of Gas Produced. 
 
 
 Per Pound Consumed in Pro- 
 
 Per Pound Equivalent Used by 
 
 Number. 
 
 ducer. 
 
 Producer Plant. 
 
 
 Coal as 
 Fired. 
 
 Dry Coal. 
 
 Combus- 
 tible. 
 
 Coal as 
 Fired. 
 
 Dry Coal. 
 
 Combus- 
 tible. 
 
 
 
 P 
 
 9 
 
 r 
 
 S 
 
 / 
 
 u 
 
 i 
 
 58.1 
 
 60.4 
 
 64-5 
 
 52.9 
 
 55-o 
 
 58.9 
 
 2 
 
 42.1 
 
 5^8 
 
 57-o 
 
 35-8 
 
 44-9 
 
 48.5 
 
 t3 
 
 49.8 
 
 53-9 
 
 60.2 
 
 45-i 
 
 48.8 
 
 54-5 
 
 t4 
 
 5I-I 
 
 58-4 
 
 65-3 
 
 44-8 
 
 5i-4 
 
 57-4 
 
 t5 
 
 44-5 
 
 5-3 
 
 56.7 
 
 40.4 
 
 45-6 
 
 5i-5 
 
 t6 
 
 58-2 
 
 63.6 
 
 7i-3 
 
 51-6 
 
 55-9 
 
 62.6 
 
 7 
 
 51-6 
 
 54-1 
 
 59-4 
 
 47-4 
 
 49.9 
 
 54-6 
 
 8 
 
 56.4 
 
 61.9 
 
 75-5 
 
 50.2 
 
 55-i 
 
 67.1 
 
 9 
 
 48.5 
 
 58-1 
 
 77-2 
 
 43- 
 
 51.6 
 
 68.5 
 
 10 
 
 60. i 
 
 62.8 
 
 71.2 
 
 54-6 
 
 57-2 
 
 64.8 
 
 tn 
 
 51.2 
 
 55-i 
 
 61.1 
 
 46.2 
 
 49-7 
 
 55- 
 
 tl2 
 
 55-7 
 
 66.0 
 
 75-7 
 
 50.2 
 
 56.8 
 
 68.2 
 
 tl3 
 
 36-2 
 
 40.9 
 
 46.5 
 
 32.6 
 
 36.8 
 
 41.9 
 
 ti4 
 
 25.2 
 
 41-5 
 
 46.4 
 
 22.7 
 
 37-5 
 
 41.9 
 
 ti 5 
 
 28.4 
 
 42.7 
 
 50.6 
 
 2 5-S 
 
 38.2 
 
 45-3 
 
 16 
 
 34-2 
 
 51-6 
 
 57-9 
 
 30.8 
 
 46.4 
 
 52-2 
 
 i? 
 
 63.2 
 
 64. i 
 
 68.4 
 
 56.6 
 
 57-5 
 
 61.3 
 
 18 
 
 79.6 
 
 81.2 
 
 89.2 
 
 70.6 
 
 71.9 
 
 79.2 
 
 iQ 
 
 82.5 
 
 85-1 
 
 91.4 
 
 73-o 
 
 75-3 
 
 80.9 
 
 20 
 
 5 6 -9 
 
 58.4 
 
 62.0 
 
 Si-3 
 
 52.6 
 
 55-9 
 
 21 
 
 52.6 
 
 54-o 
 
 57-4 
 
 48.0 
 
 49-3 
 
 52-3 
 
 22 
 
 69-3 
 
 70.9 
 
 76.3 
 
 60.9 
 
 62.2 
 
 67.0 
 
 t23 
 
 70.1 
 
 71.2 
 
 76.2 
 
 62.1 
 
 63.2 
 
 67.5 
 
 24 
 
 37-o 
 
 40.9 
 
 53-o 
 
 35-5 
 
 35-8 
 
 46.5 
 
 * From "Report on Coal-Testing Plant," United States Geological Survey, 
 1906. 
 
 t Gas producer hopper leaked during these tests. 
 
RESULTS OF TRIALS 
 
 413 
 
 TABLE XVI. f 
 
 Pounds of Various Coals and Lignites per Brake Horsepower 
 per Hour Delivered by Gas Engine.* 
 
 See also Tables XII, XIII, XIV, XV, and Fig. 138. 
 
 Three-cylinder, single-acting gas engine, 19 inches diameter by 22 
 inches stroke. Rated 235 brake horsepower at 200 revolutions per 
 minute. 
 
 All gas made in the same producer of the continuous up-draught 
 pressure type, about 7 feet inside diameter at the fire zone. 
 
 No. 
 
 Pounds of Coal per Brake Horsepower Hour. 
 
 Consumed in Producer. 
 
 Equivalent Value Used by Pro- 
 ducer Plant. 
 
 Coal as 
 Fired. 
 
 Dry Coal. 
 
 Combus- 
 tible. 
 
 Coal as 
 Fired. 
 
 Dry Coal. 
 
 Combus- 
 tible. 
 
 V 
 
 w 
 
 X 
 
 y 
 
 2 
 
 2l 
 
 22 
 
 I 
 
 1.32 
 
 1.27 
 
 1.19 
 
 1-45 
 
 1.40 
 
 1.30 
 
 2 
 
 i-55 
 
 1.23 
 
 1.14 
 
 1.82 
 
 J -45 
 
 1.34 
 
 ta 
 
 1.49 
 
 1.38 
 
 1.23 
 
 1.64 
 
 1.52 
 
 1.36 
 
 t4 
 
 1.50 
 
 1-31 
 
 1.17 
 
 1.71 
 
 1.50 
 
 1.34 
 
 t5 
 
 1.68 
 
 1.49 
 
 1.32 
 
 1.85 
 
 1.64 
 
 1-45 
 
 t6 
 
 1.27 
 
 1.16 
 
 1.03 
 
 1-43 
 
 1.32 
 
 1.18 
 
 7 
 
 1.50 
 
 1-43 
 
 1.30 
 
 1.64 
 
 1.56 
 
 1.41 
 
 8 
 
 1.18 
 
 i. 08 
 
 .89 
 
 1.33 
 
 I. 21 
 
 I.OO 
 
 9 
 
 1.56 
 
 1.30 
 
 .98 
 
 1.76 
 
 1.47 
 
 I . 10 
 
 10 
 
 i-3i 
 
 1.25 
 
 I. 10 
 
 1.44 
 
 i-37 
 
 I. 21 
 
 t ii 
 
 i-57 
 
 1.46 
 
 1.32 
 
 i-75 
 
 1.62 
 
 1.46 
 
 t 12 
 
 1.48 
 
 i-3i 
 
 1.09 
 
 1.65 
 
 1-45 
 
 I. 21 
 
 ti3 
 
 i-9S 
 
 1.72 
 
 1.52 
 
 2.16 
 
 1.91 
 
 1.68 
 
 tu 
 
 2.91 
 
 1.76 
 
 1.58 
 
 3-23 
 
 i. 95 
 
 1.74 
 
 txs 
 
 2-54 
 
 1.69 
 
 1-43 
 
 2.83 
 
 1.99 
 
 i. 60 
 
 16 
 
 1.98 
 
 J -3i 
 
 1.17 
 
 2. 2O 
 
 1.46 
 
 1.30 
 
 17 
 
 1.22 
 
 1.20 
 
 I -*3 
 
 1-36 
 
 1-34 
 
 1.26 
 
 18 
 
 .99 
 
 .98 
 
 .89 
 
 I. 12 
 
 I. IO 
 
 I.OO 
 
 19 
 
 I- 13 
 
 I. 10 
 
 i. 02 
 
 1.28 
 
 1.24 
 
 1-15 
 
 20 
 
 1^40 
 
 1.36 
 
 1.28 
 
 i-55 
 
 1-51 
 
 1.42 
 
 21 
 
 1.27 
 
 1.24 
 
 1.16 
 
 i-39 
 
 i-35 
 
 1.27 
 
 22 
 
 1.07 
 
 1.04 
 
 97 
 
 I. 21 
 
 1.19 
 
 I.IO 
 
 t 23 
 
 MS 
 
 I-I3 
 
 i. 06 
 
 1.30 
 
 i 28 
 
 I 20 
 
 24 
 
 1.70 
 
 1-54 
 
 1.19 
 
 1-94 
 
 1.76 
 
 1.36 
 
 * Compiled from " Report on Coal-Testing 
 cal Survey, 1906. 
 
 t Gas producer hopper leaked during these 
 
 Plant," United States Geologi- 
 tests. 
 
414 
 
 THE GAS ENGINE 
 
 TABLE XVII. 
 Proximate Analyses of Bituminous Coals.* 
 
 Percentage composition. See also Tables XX and XXII. 
 
 No. 
 
 Name of Coal. 
 
 Mois- 
 ture. 
 
 Vola- 
 tile 
 Matter. 
 
 Fixed 
 Carbon 
 
 Ash. 
 
 Sul- 
 phur. 
 
 2 C 
 
 Alabama No 4 Rm 
 
 3 Os 
 
 2Q 3 
 
 S4 78 
 
 12 64 
 
 I I ^ 
 
 26 
 
 Alabama No 6 Rm 
 
 2 44 
 
 2S 06 
 
 64 7c 
 
 6 QO 
 
 CQ 
 
 27 
 
 Arkansas No. 7 A Lump 
 
 4. 27 
 
 1 6 04 
 
 67 43 
 
 12 26 
 
 2 IS 
 
 28 
 
 Illinois No. lyC Rm 
 
 0.82 
 
 2Q 64 
 
 SO. 34 
 
 IO 2O 
 
 . 4O 
 
 2Q 
 
 Illinois No. 29 Lump 
 
 14.68 
 
 3O . O' C 
 
 42 .03 
 
 1 1 . 41 
 
 1 . 33 
 
 TO 
 
 Illinois No 22A Lump 
 
 1 1 20 
 
 3S 6c 
 
 3Q O4 
 
 13 17 
 
 4 88 
 
 31 
 
 Illinois No 23 Slack 
 
 ii . ^y 
 
 II 87 
 
 36 37 
 
 3O 87 
 
 II 89 
 
 4 6^ 
 
 72 
 
 Illinois No 246 Lump 
 
 1 1 44 
 
 33 O3 
 
 43 O2 
 
 IO 7l 
 
 4 O4. 
 
 75 
 
 Illinois No. 256 Lump 
 
 1 1 64. 
 
 3 S 41 
 
 44 2Q 
 
 8 66 
 
 341 
 
 74 
 
 Illinois No. 26 Rm. . 
 
 13 2O 
 
 32 O2 
 
 38 81 
 
 is 88 
 
 3 S2 
 
 2C 
 
 Illinois No. 27 Rm 
 
 II . 3S 
 
 33 SO 
 
 41 . 2C 
 
 13 86 
 
 4- S4 
 
 36 
 
 Illinois No. 2pB Rm 
 
 12. 2S 
 
 33. 76 
 
 41.66 
 
 12. 22 
 
 4.42 
 
 77 
 
 Illinois No. 30 Washed 
 
 S . CO 
 
 30- 3O 
 
 4S . 4s 
 
 a.66 
 
 7. 37 
 
 ^8 
 
 Indiana No 12 Rm 
 
 IO 42 
 
 36 2Q 
 
 4O 1^ 
 
 1 2 ?4 
 
 3 06 
 
 7Q 
 
 Indiana No 13 Rm. 
 
 1 1 . S3 
 
 34 80 
 
 4O 44 
 
 13 23 
 
 31 1 
 
 4O 
 
 Indiana No. 14 Rm 
 
 
 36 8c 
 
 41 O7 
 
 14 2O 
 
 S 14 
 
 4.1 
 
 Indiana No. 16 Rm 
 
 7. 70 
 
 32 32 
 
 44 07 
 
 1 1 02 
 
 4 OI 
 
 42 
 
 Indiana No. i8B Lump 
 
 12 . II 
 
 34 IQ 
 
 46 87 
 
 6 83 
 
 1 .44 
 
 4-2 
 
 Kansas No. 6 Lump 
 
 0.8s: 
 
 3O. 10 
 
 46.6? 
 
 13.2^ 
 
 3.04 
 
 44 
 
 New Mexico No. 3A Rm 
 
 3.62 
 
 31 S6 
 
 4S 10 
 
 10- 63 
 
 72 
 
 4S 
 
 New Mexico No. 4A Rm 
 
 2 .42 
 
 34.82 
 
 40-23 
 
 17 . S3 
 
 .63 
 
 46 
 
 New Mexico No s Rm 
 
 I 70 
 
 31 32 
 
 e I AC 
 
 I ^ 4O 
 
 66 
 
 4.7 
 
 Ohio No 10 Lump 
 
 4 05 
 
 3O 28 
 
 47 7^ 
 
 8 Q2 
 
 302 
 
 8 
 
 Ohio No. 1 1 Lump . . . * . 
 
 344 
 
 36 oj 
 
 t/ IJ 
 
 47 S8 
 
 12 Q4 
 
 4 32 
 
 40 
 
 Ohio No. 12 Rm. 
 
 3.82 
 
 37 77 
 
 47 42 
 
 IO QQ 
 
 3 30 
 
 SO 
 
 Pennsylvania No. 1 1 Rm 
 
 i .QS 
 
 34 O7 
 
 S6 6q 
 
 7. 2Q 
 
 1.18 
 
 Si 
 
 Pennsylvania No. 12 Rm 
 
 i .Q 
 
 3O. SS 
 
 S8.24 
 
 0- 2S 
 
 2. 10 
 
 S2 
 
 Pennsylvania No. 13 Rm 
 
 i. 6s 
 
 33. 06 
 
 S3- 22 
 
 12 .07 
 
 I. 80 
 
 C-7 
 
 Pennsylvania No i s Lump 
 
 2 17 
 
 18 09 
 
 69 oi 
 
 IO 33 
 
 3O7 
 
 c?4 
 
 Pennsylvania No. 16 Rm 
 
 S "72 
 
 21 7C 
 
 64 04 
 
 7 OC 
 
 I 60 
 
 SS 
 
 Pennsylvania No. 17 Rm 
 
 44C 
 
 A 13 
 
 28 oi 
 
 S4 87 
 
 12 72 
 
 1 . 72 
 
 56 
 
 S7 
 
 Pennsylvania No. 22 Rm 
 Tennessee No. i Rm 
 
 3.98 
 2 . 72 
 
 28.13 
 
 31. 81 
 
 57-73 
 
 ^3- 2C 
 
 10. if 
 12 . 27 
 
 I.OO 
 
 1.26 
 
 58 
 
 CQ 
 
 Tennessee No. 2 Rm 
 Tennessee No 3 Rm 
 
 3-4C 
 
 4 88 
 
 37.58 
 
 34 84 
 
 54-27 
 
 r 7 C7 
 
 4-75 
 6 71 
 
 .83 
 
 i 16 
 
 60 
 
 Tennessee No 4 Rm 
 
 320 
 
 34 4O 
 
 S4 82 
 
 7 4O 
 
 88 
 
 61 
 
 Tennessee No s, Rm 
 
 2 S4 
 
 34 64 
 
 S3 06 
 
 8 86 
 
 7 . 7Q 
 
 62 
 
 Tennessee No. 6 Rm 
 
 3 SS 
 
 26 oo 
 
 40 85 
 
 2O S7 
 
 6 -6V 
 
 . 76 
 
 63 
 
 Tennessee No. 7 A Rm. 
 
 3.O3 
 
 34-01 
 
 40- 21 
 
 12.85 
 
 3.26 
 
 64 
 
 Tennessee No. 8 Washed Rm 
 
 2 .43 
 
 3S -41 
 
 S2. 2Q 
 
 0-87 
 
 3-o6 
 
 6s 
 
 Utah No. i Rm 
 
 5.83 
 
 42 .46 
 
 47. os 
 
 4.66 
 
 =?7 
 
 66 
 
 Virginia No 6 Rm 
 
 4ej 
 
 22 77 
 
 62 64 
 
 10 08 
 
 I SO 
 
 
 ^Vashington No 2 Lump 
 
 4OI 
 
 34 6l 
 
 47 40 
 
 13.80 
 
 .38 
 
 68 
 
 \Vest Virginia No 25 Lump 
 
 3 83 
 
 34 34 
 
 S3. 6l 
 
 8.22 
 
 .62 
 
 63 
 
 \Vyoming No. 4 Rm. .... 
 
 II . 3O 
 
 4O. 32 
 
 41 .07 
 
 7. 31 
 
 .28 
 
 70 
 
 Wyoming No. 5 Rm. 
 
 II .44 
 
 36. 37 
 
 48.40 
 
 3. 70 
 
 Oi 
 
 
 
 
 
 
 
 
 * Compiled from " Report on U. S. Fuel Testing Plant," Geological Sur- 
 vey, 1908. 
 
 Rm. = run of mine. 
 
RESULTS OF TRIALS 
 
 415 
 
 TABLE XVIII. 
 
 Pounds of Bituminous Coal per Brake Horsepower Delivered 
 
 by Engine.* 
 
 See also Tables XVII and XXI. Three-cylinder, single-acting gas engine, 19 in. diam. 
 by 22 in. stroke, rated 235 brake horsepower at 200 rev. per min. All gas made 
 in the same producer of the continuous up-draught pressure type, about 7 feet inside 
 diameter at the fire zone. 
 
 No. 
 
 Consumed in Producer. 
 
 Equivalent Value Used 
 by Producer Plant. 
 
 Length 
 of Test. 
 Hours. 
 
 Total 
 Coal 
 Fired. 
 Pounds. 
 
 Coal as 
 Fired. 
 
 Dry 
 
 Coal. 
 
 Combus- 
 tible. 
 
 Coal as 
 Fired. 
 
 Dry 
 Coal. 
 
 Combus- 
 tible. 
 
 25 
 
 1. 06 
 
 1.03 
 
 .90 
 
 1.16 
 
 I. 12 
 
 97 
 
 24 
 
 5,850 
 
 26 
 
 77 
 
 75 
 
 7 
 
 .84 
 
 .82 
 
 .76 
 
 5 
 
 9,000 
 
 27 
 
 I. 60 
 
 J-53 
 
 i-34 
 
 74 
 
 .66 
 
 i-45 
 
 5 
 
 12,900 
 
 28 
 
 1.74 
 
 i-57 
 
 i-39 
 
 .90 
 
 7i 
 
 1.52 
 
 5 
 
 14,400 
 
 29 
 
 1 . 64 
 
 i .40 
 
 I . 22 
 
 .76 
 
 5 
 
 1.30 
 
 562 
 
 208,350 
 
 3 
 
 1.50 
 
 !-33 
 
 *-I3 
 
 59 
 
 .41 
 
 i. 20 
 
 47 
 
 16,300 
 
 3 1 
 
 i-54 
 
 1-36 
 
 1.18 
 
 63 
 
 43 
 
 1.24 
 
 5 
 
 18,000 
 
 3 2 
 
 1.24 
 
 I. 10 
 
 97 
 
 3 2 
 
 17 
 
 1.03 
 
 5 
 
 14,650 
 
 33 
 
 1.36 
 
 I . 20 
 
 I .02 
 
 43 
 
 .27 
 
 i. 08 
 
 5 
 
 16,000 
 
 34 
 
 1.56 
 
 1.36 
 
 I . II 
 
 7 
 
 47 
 
 1.20 
 
 5 
 
 16,050 
 
 35 
 
 2.19 
 
 1.94 
 
 1.6 3 
 
 36 
 
 2.IO 
 
 1.77 
 
 ? 
 
 16,050 
 
 36 
 
 r-5* 
 
 1-33 
 
 I.I4 
 
 .62 
 
 .42 
 
 1.22 
 
 So 
 
 17.250 
 
 37 
 
 1.38 
 
 i-3i 
 
 I.I7 
 
 45 
 
 37 
 
 1.23 
 
 5 
 
 16,200 
 
 38 
 
 1.50 
 
 i-35 
 
 1.16 
 
 59 
 
 43 
 
 1.23 
 
 5 
 
 17,200 
 
 39 
 
 1.26 
 
 1-13 
 
 99 
 
 39 
 
 .22 
 
 1.07 
 
 24 
 
 6 >75 
 
 40 
 
 i-45 
 
 i-34 
 
 i-i3 
 
 54 
 
 .42 
 
 I .20 
 
 5 
 
 16,200 
 
 4i 
 
 1.82 
 
 1.68 
 
 1.46 
 
 54 
 
 .42 
 
 1.24 
 
 5 
 
 16,100 
 
 42 
 
 1.26 
 
 I. 12 
 
 1.03 
 
 35 
 
 . 2O 
 
 I. II 
 
 36 
 
 10,35 
 
 43 
 
 1.41 
 
 1.27 
 
 i. 08 
 
 49 
 
 35 
 
 *'1S 
 
 i3 
 
 4,5 
 
 44 
 
 I. 10 
 
 I. 06 
 
 85 
 
 .18 
 
 .14 
 
 .91 
 
 5 
 
 12,850 
 
 45 
 
 1.18 
 
 *-*5 
 
 99 
 
 .29 
 
 .26 
 
 I. 08 
 
 5o 
 
 13,110 
 
 46 
 
 1.20 
 
 1.18 
 
 99 
 
 .29 
 
 .26 
 
 I. 06 
 
 45 
 
 12,500 
 
 47 
 
 I. 08 
 
 i .04 
 
 94 
 
 !5 
 
 . 10 
 
 I .00 
 
 .5 
 
 12,650 
 
 48 
 
 1.18 
 
 1.14 
 
 99 
 
 .26 
 
 .22 
 
 I. 06 
 
 5 
 
 13,850 
 
 49 
 
 1.23 
 
 1.18 
 
 1.05 
 
 3 2 
 
 .27 
 
 I-I3 
 
 5 
 
 14,35 
 
 5 
 
 I . 22 
 
 1.19 
 
 I. IO 
 
 3 2 
 
 .29 
 
 I. 2O 
 
 5 
 
 12,200 
 
 5 1 
 
 95 
 
 93 
 
 .84 
 
 5 
 
 3 
 
 93 
 
 28 
 
 6,100 
 
 5 2 
 
 1.02 
 
 I.OO 
 
 .88 
 
 . 10 
 
 .09 
 
 95 
 
 5 
 
 ii>75 
 
 53 
 
 1.05 
 
 1.03 
 
 .92 
 
 J 7 
 
 .14 
 
 i. 02 
 
 24 
 
 5.7oo 
 
 54 
 
 .85 
 
 .80 
 
 74 
 
 95 
 
 .90 
 
 .82 
 
 5 
 
 9.95 
 
 55 
 
 I.I 9 
 
 1.14 
 
 99 
 
 .26 
 
 .21 
 
 1.05 
 
 5 
 
 13,200 
 
 56 
 
 I .01 
 
 97 
 
 .86 
 
 .07 
 
 3 
 
 .92 
 
 5 
 
 11,700 
 
 57 
 
 1.24 
 
 1.20 
 
 1.05 
 
 3 2 
 
 .29 
 
 I. 12 
 
 So 
 
 12,300 
 
 58 
 
 -95 
 
 .92 
 
 .87 
 
 5 
 
 .02 
 
 .96 
 
 5 
 
 11,250 
 
 59 
 
 I . 10 
 
 I.O4 
 
 97 
 
 .19 
 
 13 
 
 1.0 5 
 
 5 
 
 12,950 
 
 60 
 
 1-13 
 
 I. 10 
 
 .01 
 
 23 
 
 .I 9 
 
 I. 10 
 
 50 
 
 12,150 
 
 61 
 
 1.18 
 
 I-I5 
 
 .04 
 
 .28 
 
 2 5 
 
 I. 14 
 
 5 
 
 12,900 
 
 62 
 
 i-45 
 
 i-39 
 
 . 10 
 
 . ^Q 
 
 53 
 
 I . 20 
 
 3 
 
 7,95 
 
 63 
 
 1.27 
 
 1.23 
 
 .07 
 
 ^^ 
 
 35 
 
 1.16 
 
 5 
 
 14,400 
 
 64 
 
 1,18 
 
 i-i5 
 
 03 
 
 .26 
 
 2 3 
 
 I. 10 
 
 24 
 
 6,55 
 
 65 
 
 i-38 
 
 1.30 
 
 .24 
 
 i7 
 
 . ii 
 
 1.05 
 
 5 
 
 14,250 
 
 66 
 
 97 
 
 .92 
 
 83 
 
 .06 
 
 .01 
 
 .91 
 
 5 
 
 11,000 
 
 67 
 
 i-i5 
 
 i. ii 
 
 95 
 
 .22 
 
 17 
 
 I .01 
 
 35 
 
 9.30 
 
 68 
 
 i. ii 
 
 1.07 
 
 .98 
 
 17 
 
 I. 12 
 
 1.03 
 
 50 
 
 13,000 
 
 69 
 
 1.76 
 
 1-56 
 
 i-43 
 
 I.9I 
 
 1.69 
 
 i-55 
 
 5 
 
 20,200 
 
 70 
 
 1.36 
 
 I. 21 
 
 1.16 
 
 p 
 
 ? 
 
 ? 
 
 5 
 
 15.600 
 
 * Compiled from "Report on U. S. Fuel Testing Plant," Geological Survey, 1908. 
 
416 
 
 THE GAS ENGINE 
 
 TABLE XIX. 
 
 Proximate Analyses of Lignites, Peat, Bone Coal, Subbituminous, 
 Semianthracite, Anthracite, and Coke.* 
 
 See also Tables XX and XXII. 
 Percentage Composition. 
 
 No. 
 
 Name of Fuel. 
 
 Mois- 
 ture. 
 
 Vola- 
 tile 
 Matter. 
 
 Fixed 
 Car- 
 bon. 
 
 Ash. 
 
 Sul- 
 phur. 
 
 71 
 
 Lignites : 
 Arkansas No. 10 Rm. 
 
 7Q A 7 
 
 26 49 
 
 24 7,7 
 
 971 
 
 
 72 
 
 Montana No. 2 . 
 
 8 51 
 
 31 58 
 
 44 ^2 
 
 1 5 2,0 
 
 60 
 
 
 Montana No. 3 
 
 
 
 45.69 
 
 
 
 74 
 
 Texas No. 3 Lump 
 
 2,2. 2O 
 
 2.0. ii 
 
 28.82 
 
 8.87 
 
 .88 
 
 
 Texas No. 4 Rm.. 
 
 
 77 I C 
 
 2C 7,2 
 
 7 45 
 
 4O 
 
 76 
 
 Peat:f 
 Florida No. i Compressed 
 
 21 .OO 
 
 ri . 72 
 
 22 . 1 1 
 
 5. 1 7 
 
 
 77 
 78 
 
 Bone coal: 
 West Virginia No. n B Hand ) 
 picked from waste J 
 West Virginia No. 24 
 
 47 
 
 2.QI 
 
 8.83 
 
 ii. 81 
 
 46.96 
 
 CJ . IQ 
 
 43-74 
 28.08 
 
 .27 
 
 70 
 
 Subbituminous : 
 \Vashington No. lA Pea 
 
 
 34 oo 
 
 7.7 27 
 
 12 56 
 
 
 80 
 
 8r 
 
 Washington No. iB Rm. Small sizes 
 Wyoming No. 6 Rm 
 
 16.02 
 
 18.26 
 
 33-27 
 37.18 
 
 36.81 
 41.82 
 
 13.90 
 2 . 74 
 
 59 
 
 .47 
 
 8? 
 
 Semianthracite : 
 Arkansas No. 8 
 
 2 . 74 
 
 0- 7O 
 
 71.95 
 
 15.61 
 
 2.45 
 
 8? 
 
 Anthracite : 
 Virginia No 5A Pea 
 
 37.4 
 
 II 28 
 
 67 24 
 
 18 14 
 
 
 84 
 
 Coke: 
 ]Viscell aneous 
 
 7 86 
 
 60 
 
 79 
 
 ii 51 
 
 I 14 
 
 
 
 
 
 
 
 
 * Compiled from " Report on U. S. Fuel Testing Plant," Geological 
 Survey, 1008. 
 
 t Peat from a bog at Orlando, Orange County, Florida, on the Seaboard 
 Air Line Railway. The raw peat contains about 92 per cent of moisture. 
 The sample tested was machined and sun dried. In this process the raw 
 peat is first passed through a condenser to disintegrate it and destroy the 
 fiber. It is then passed through a molding machine which molds it into 
 bricks 8 X 4 x 2.5 inches. The bricks are taken to the drying ground and 
 left till they lose from 60 to 75 per cent of their moisture. 
 
 Rm. = run of mine. 
 
RESULTS OF TRIALS 
 
 417 
 
 TABLE XX. 
 Pounds of Fuel per Brake Horsepower Delivered by Engine.* 
 
 See also Tables XIX and XXII. Three -cylinder, single-acting gas engine, 
 19 in. diam. by 22 in. stroke, rated at 235 horsepower at 200 rev. per 
 min. All gas made in the same producer of the continuous up-draught 
 pressure type, about 7 ft. inside diam. at the fire zone. 
 
 No. 
 
 Consumed in Producer. 
 
 Equivalent Value Used 
 by Producer Plant. 
 
 Length 
 of Test. 
 Hours. 
 
 Total 
 Coal 
 Fired. 
 Pounds. 
 
 Coal as 
 Fired. 
 
 Dry 
 Coal. 
 
 Combus- 
 tible. 
 
 Coal as 
 Fired. 
 
 Dry 
 Coal. 
 
 Combus- 
 tible. 
 
 7 1 
 
 3-3 
 
 1.83 
 
 i-54 
 
 3 45 
 
 2.09 
 
 l. 7 6 
 
 18 
 
 8250 
 
 72 
 
 1.74 
 
 i-59 
 
 1.32 
 
 1.91 
 
 i-75 
 
 1-45 
 
 40 
 
 1545 
 
 73 
 
 i-39 
 
 1.27 
 
 1. 08 
 
 1.48 
 
 i-35 
 
 *-iS 
 
 49 
 
 1595 
 
 74 
 
 2.17 
 
 1.47 
 
 1.28 
 
 2 -33 
 
 1-58 
 
 1-38 
 
 5 
 
 25500 
 
 75 
 
 2.16 
 
 1.42 
 
 1.26 
 
 2-33 
 
 i-54 
 
 1.36 
 
 5 
 
 2455 
 
 76 
 
 2-43 
 
 1.92 
 
 1.79 
 
 2-57 
 
 2.03 
 
 i .90 
 
 5 
 
 29250 
 
 77 
 
 1-65 
 
 1.64 
 
 .92 
 
 ? 
 
 ? 
 
 p 
 
 5 
 
 18900 
 
 78 
 
 1.26 
 
 1.22 
 
 .87 
 
 ? 
 
 ? 
 
 p 
 
 5 
 
 1 1 000 
 
 79 
 
 2-79 
 
 2-34 
 
 1.99 
 
 2-93 
 
 2-45 
 
 2.08 
 
 40 
 
 18900 
 
 So 
 
 2.03 
 
 I.7I 
 
 1-43 
 
 2.20 
 
 1.85 
 
 i-54 
 
 14 
 
 6550 
 
 Si 
 
 1.86 
 
 1.52 . 
 
 1.47 
 
 2.02 
 
 1.65 
 
 i-59 
 
 5 
 
 21900 
 
 82 
 
 1.58 
 
 i-54 
 
 1.29 
 
 1.72 
 
 1.67 
 
 1.40 
 
 26 
 
 8550 
 
 83 
 
 i-i3 
 
 1.09 
 
 .89 
 
 1.22 
 
 1.18 
 
 .96 
 
 30 
 
 795 
 
 84 
 
 .87 
 
 .80 
 
 .70 
 
 p 
 
 p 
 
 ? 
 
 41 
 
 8400 
 
 * Compiled from "Report on U. S. Fuel Testing Plant," Geological 
 Survey, 1908. 
 
4i8 
 
 THE GAS ENGINE 
 
 TABLE XXI. 
 
 Average Compositions of Producer Gases from 
 Bituminous Coals.* 
 
 See also Tables XVII and XVIII. All gas made in the same producer of 
 the continuous up-draught pressure type. Average composition of gas 
 by volume. Per cent. 
 
 No. 
 
 C0 2 
 
 2 
 
 CO 
 
 H 2 
 
 CH 4 
 
 N 2 
 
 C 2 H 4 
 
 % 
 
 IO. I 
 
 9 6 
 
 
 17.0 
 
 IO. C 
 
 14-5 
 I4-Q 
 
 1.9 
 I 7 
 
 56.1 
 
 <4. 2 
 
 4 
 i 
 
 27 
 
 V' 
 
 14. 8 
 
 
 12. I 
 
 16.1 
 
 1.6 
 
 CC.4 
 
 
 28 
 29 
 
 3 
 
 ii. 6 
 9.2 
 
 9-4 
 
 8 4. 
 
 
 
 16.8 
 20.9 
 
 2O. 2 
 2O O 
 
 16.2 
 15-6 
 
 13-7 
 12 9 
 
 1.9 
 1.9 
 
 2.0 
 
 i 6 
 
 52.9 
 52.0 
 
 54-0 
 
 CC 7 
 
 3 
 4 
 
 7 
 c 
 
 o 1 
 3 2 
 
 8.4 
 8 t 
 
 . i 
 
 22.6 
 22 C 
 
 I3 '? 
 
 13 6 
 
 2. I 
 
 2 2 
 
 52.5 
 C2 
 
 J 
 
 5 
 
 r 
 
 00 
 
 IO C 
 
 
 10 4 
 
 ir . t: 
 
 I 7 
 
 C2 C 
 
 4 
 
 0^ 
 
 35 
 36 
 
 H 
 
 39 
 
 12.4 
 ii. 4 
 9-3 
 9.0 
 10.9 
 o 8 
 
 
 15.0 
 
 17-3 
 19.6 
 19.0 
 
 18.0 
 
 2O 4 
 
 12.9 
 14.0 
 13-8 
 I 3 .0 
 IS.2 
 
 14- 4- 
 
 1.6 
 
 2.0 
 2.0 
 2.0 
 1-9 
 2 2 
 
 57-7 
 54-8 
 
 54-7 
 56.0 
 
 53-6 
 
 C2 7 
 
 4 
 
 :! 
 
 i .0 
 
 4 
 c 
 
 4i 
 
 11.4 
 
 
 16.8 
 
 10 4 
 
 13-3 
 16.0 
 
 i-7 
 
 2. I 
 
 56.3 
 C2 . 2 
 
 5 
 . -i 
 
 
 8 2 
 
 
 21 O 
 
 12. 7 
 
 2. I 
 
 re .4 
 
 .6 
 
 4,5 
 
 92 
 
 
 2O C 
 
 14- "? 
 
 2 .O 
 
 C2 . 4 
 
 4 
 
 
 10 6 
 
 
 17 O 
 
 12.6 
 
 2 .O 
 
 C7. 2 
 
 .6 
 
 46 
 
 8 6 
 
 
 21 .4 
 
 14. 6 
 
 2 . 2 
 
 C2 . 7 
 
 . c 
 
 47 
 
 94 
 
 
 2O. 7 
 
 14. 2 
 
 2.6 
 
 C2.6 
 
 . c 
 
 48 
 
 9O 
 
 
 2O. 2 
 
 1C. 5 
 
 2. 7 
 
 C2. ? 
 
 . c 
 
 49 
 5 
 Si 
 
 9-3 
 10.4 
 10.8 
 
 
 19.9 
 
 18.5 
 
 16.6 
 
 ii c 
 
 15.2 
 16.3 
 
 14.9 
 
 12.6 
 
 2-5 
 2.0 
 2.4 
 2 . I 
 
 5 2.6 
 52-6 
 
 54-8 
 
 c;7. i 
 
 5 
 
 .2 
 
 i 
 
 J* 
 53 
 54 
 55 
 56 
 
 P 
 
 CO 
 
 10.7 
 
 10. I 
 IO.O 
 10. I 
 IO.O 
 
 10.9 
 9 8 
 
 . i 
 
 17.2 
 18.2 
 
 *7-5 
 17.6 
 19.6 
 18.8 
 
 2O. 2 
 
 15.8 
 15.8 
 
 13-7 
 13-3 
 
 J 5-3 
 18.6 
 16.5 
 
 2.2 
 
 2 -3 
 
 2.2 
 2.2 
 2. I 
 2.2 
 
 2-4 
 
 53-8 
 S3- 2 
 56-1 
 56.4 
 52.6 
 49.0 
 co. 7 
 
 3 
 4 
 4 
 4 
 4 
 5 
 4 
 
 2 9 
 60 
 
 IO 4 
 
 
 I9.O 
 
 , J 
 16.7 
 
 2.4 
 
 51.0 
 
 .5 
 
 61 
 
 II 1 
 
 
 I7.O 
 
 1C. 7 
 
 1.7 
 
 54.2 
 
 .5 
 
 62 
 
 12 3 
 
 
 ICO 
 
 14.0 
 
 I.Q 
 
 C.6.4 
 
 .4 
 
 63 
 64 
 
 65 
 66 
 
 67 
 63 
 
 II. 2 
 
 9-7 
 8-5 
 10.5 
 
 7-9 
 
 7.0 
 
 
 
 17.4 
 I9.I 
 22.2 
 17.4 
 22.2 
 23.4 
 
 15-3 
 
 IS- 1 
 15-7 
 14-3 
 i5-4 
 17. i 
 
 2 -3 
 
 2. I 
 2.6 
 2.0 
 2.6 
 2. I 
 
 53-3 
 53-5 
 50-5 
 55-5 
 5i-5 
 49. i 
 
 5 
 5 
 
 5 
 3 
 4 
 4 
 
 60 
 
 12. 2 
 
 
 2 * 
 10.4 
 
 15.1 
 
 2-7 
 
 53.2 
 
 4 
 
 70 
 
 10. I 
 
 
 2O-4 
 
 18.2 
 
 2.6 
 
 48.3 
 
 4 
 
 * Compiled from 
 Survey, 1908. 
 
 Report on U. S. Fuel Testing Plant," Geological 
 
RESULTS OF TRIALS 
 
 419 
 
 TABLE XXII. f 
 
 Average Compositions of Producer Gases from Lignites, Peat, 
 Bone Coal, Subbituminous, Semianthracite, Anthracite, and 
 Coke.* 
 
 See also Tables XIX and XX. All gas made in the same producer of the 
 continuous up-draught pressure type. Average composition of gas by 
 volume. Per cent. 
 
 No. 
 
 CO 2 
 
 2 
 
 CO 
 
 H 2 
 
 CH 4 
 
 N 2 
 
 C 2 H 4 
 
 71 
 
 17 C 
 
 
 14.0 
 
 O. 2 
 
 2 . 4 
 
 6O.O 
 
 
 72 
 
 13.2 
 
 .2 
 
 14.2 
 
 16.0 
 
 2.9 
 
 5 2 -9 
 
 .6 
 
 73 
 
 8.0 
 
 
 27.. 2 
 
 i"> -9 
 
 7. 3 
 
 49- 2 
 
 4 
 
 74 
 
 10.3 
 
 7 
 
 19.8 
 
 14-8 
 
 2.4 
 
 51-3 
 
 7 
 
 7c 
 
 IO 3 
 
 
 2O. O 
 
 IS .4 
 
 2 . C 
 
 Si. 8 
 
 
 76 
 
 12 4 
 
 
 21 .O 
 
 l8.< 
 
 2 . 2 
 
 4:; . c 
 
 4 
 
 77 
 
 0. 7 
 
 
 IO. ? 
 
 16.6 
 
 1.6 
 
 52.6 
 
 
 78 
 
 12.4 
 
 
 I4.O 
 
 13.8 
 
 I . 2 
 
 58.6 
 
 
 7Q 
 
 II 3 
 
 
 1^4 
 
 IO. < 
 
 3-6 
 
 CO. 2 
 
 
 80 
 
 12.6 
 
 . 2 
 
 13-9 
 
 12.8 
 
 2.6 
 
 57-4 
 
 7 
 
 81 
 
 12. I 
 
 
 l8. 7 
 
 19-3 
 
 3- 
 
 46.5 
 
 4 
 
 82 
 
 n-3 
 
 . 2 
 
 15-9 
 
 14.7 
 
 I.O 
 
 56.7 
 
 .2 
 
 83 
 
 IO. 2 
 
 
 19.1 
 
 20.5 
 
 1.9 
 
 48.2 
 
 . I 
 
 84 
 
 92 
 
 
 2IO 
 
 ii . i 
 
 . 2 
 
 C7. C 
 
 . I 
 
 
 
 
 
 
 
 
 
 * Compiled from " Report on U. S. Fuel Testing Plant," Geological Sur- 
 vey, 1908. 
 
4 20 
 
 THE GAS ENGINE 
 
 274. Test of a soo-Horsepower Gas Engine Plant at Worcester, 
 
 Mass.* The gas engine tested was rated 500 horsepower at 
 155 r.p.m. It was of the tandem, double-acting, horizontal, 
 four-cycle type (four combustion chambers) with cylinders 23.5 
 inches diameter and a stroke of 33 inches, direct connected to an 
 electric generator. 
 
 The gas producers were of the intermittent, down-draught type. 
 Two were used as a pair. 
 
 FIG. 139. Plan of Gas Engine Power Plant. 
 
 The general arrangement of the plant is shown in Fig. 139. 
 The producers are shown more in detail in Fig. 116. 
 
 The fuel used was bituminous coal, except the lower part of 
 the fuel bed, which was anthracite coal put on when building the 
 fires at the beginning of the test. The analyses of the fuel are 
 given in Table XXVI. 
 
 It is worthy of note that the engine ran at 522 brake horse- 
 power (D.h.p.) for six consecutive hours on gas of 109 B.t.u. per 
 cubic foot, lower heat value, and that it ran for a few moments 
 at slightly more than 600 brake horsepower, 20 per cent overload, 
 "without evidence of l stalling.'" 
 
 In the gas producers the duration of the run with steam for 
 making water gas (blowing in steam at the bottom with the air 
 blast shut off) was from 20 to 30 seconds. The ratio of the time of 
 duration of the water gas run to that of the air blasting is shown 
 in Fig. 141. 
 
 * Trans. Amer. Soc. Mech. Engrs., Vol. 29, 1907. 
 
RESULTS OF TRIALS 421 
 
 The " holder drop tests" were made by completely cutting off 
 the producers from the gas holder, so that no gas was admitted 
 to the holder. The drop of the holder was measured as the 
 engine drew gas from it, and the amount of gas used computed 
 from the drop. 
 
 The " digest of results" is taken verbatim from the report. 
 The tables and such of the figures as are used are reproduced 
 practically unchanged. They are self-explanatory. A few foot- 
 notes have been added to transform certain expressions into the 
 terms used in the text of this book. 
 
 Lower or effective heat values are used throughout the report. 
 
 Digest of Results of Test of 500- Horsepower Gas Engine Plant. 
 
 1. Full load test, 51 hours duration, continuous run without 
 service interruptions of any kind; average load 11 per cent 
 above generator rating, or practically full engine rating 332 kw., 
 483 b.h.p. 
 
 2. Fractional load tests by the holder drop method; runs made 
 at five different loads, from no load to full engine rating. 
 
 3. A load of 600 h.p., sustained for a short time without abnor- 
 mal drop in speed. 
 
 4. Average coal consumption at the producer, i.4lb. per kw.-hr., 
 equivalent to 0.97 Ib. per b.h.p. hr., using Clearfield bituminous 
 run-of-mine (14,321 B.t.u. per Ib.). 
 
 5. Average heat consumption at the engine, 10,100 B.t.u. per 
 b.h.p. hr. at full load; 10,200 B.t.u. per b.h.p. hr. at average test 
 load, equivalent to 25.29 per cent thermal efficiency * a! full 
 rating. 
 
 6. Mechanical efnciency,f full rating, 83.8 per cent, average 
 test load, 83.5 per cent. 
 
 7. Average water consumption for engine only, 9.74 gal. per 
 b.h.p. hr. with 66 F. inlet temperature and 47.1 F. rise, equiva- 
 lent to 9.4 gal. per b.h.p. hr. at full rating. 
 
 * Corresponds to motor efficiency as defined in Chapter XV. 
 
 t Corresponds to impulse-output efficiency as defined in Chapter XV. 
 
422 THE GAS ENGINE 
 
 8. Average cylinder oil consumption, 1.44 gal. per 24 hour, 
 equivalent to 0.6 gal. per operating day, or 3.2 gal. per operating 
 week. 
 
 9. Speed regulation, no load to full load, 2.5 per cent above 
 and below mean. 
 
 10. Average producer efficiency, 74.4 per cent at full load; 
 73.8 per cent at average test load both based upon lower or 
 effective heat value of gas. 
 
 11. Producer gas, average, 114.6 effective* B.t.u. during 
 5 1 -hour test; maximum variation 11.5 per cent above and below 
 mean. Difference between total and effective heat values, about 
 4f per cent. 
 
 TABLE XXIII. 
 Normal Operating Economy. 
 
 Averages for Nine Weeks. 500 -Horsepower Gas Engine Power Plant. 
 
 Number of hours per week run on load 54-4 hours. 
 
 Output 13500. o kw.-hrs. 
 
 Average running load 248 . i kw. 
 
 Average running load per cent rating of engine 72 . 2 per cent. 
 
 Coal gasified (including stand-by losses) 24839 . o pounds. 
 
 Coal for new fires 2369 . o pounds. 
 
 Coal for new fires (per cent of producer coal) 9.5 per cent. 
 
 Total coal for all purposes 27204. o pounds. 
 
 Average total coal per hour including new fires 500.00 pounds. 
 
 Coal consumed (excluding new fires) per kw.-hr i . 83 pounds. 
 
 Total coal consumed per kw.-hr 2 . 015 pounds. 
 
 * Lower heat value. 
 
RESULTS OF TRIALS 
 
 423 
 
 TABLE XXIV. 
 5 1 -Hour Test of Gas Power Plant. 
 
 5oo-Horsepower Gas Engine. Summary of Results. 
 
 
 Load. 
 Kilowatts . 
 
 Water. 
 Cubic Feet. 
 
 Oil. 
 Gallons. 
 
 Coal.* 
 Pounds. 
 
 Quantity at finish 
 
 3 6 3>55 - 
 345,710.0 
 16,840.0 
 + 117.3 
 
 i6,957-3 
 51 hrs. 
 
 332-5 
 
 94,900 . o 
 63,560.0 
 31.340.0 
 
 2.875 
 
 23.775 
 
 Quantity at start 
 
 "Difference . 
 
 2.875 
 
 23.775 
 
 23.775 
 51 hrs. 
 466 
 
 
 Corrected difference 
 
 
 31,340.0 
 50 hrs. 
 626.8 
 
 2.875 
 48 hrs. 
 0.06 
 
 Elapsed time 
 
 Rate per hour 
 
 
 
 Water. 
 Cu. Ft. 
 
 Water. 
 Gal. 
 
 Oil. 
 Gal. 
 
 Coal. 
 Pounds. 
 
 Rate per kw.-hr (332 . 5 kw.) 
 Rate per b.h.p. hr (482 . 9 b.h.p.) 
 Rate per i.h.p. hr (579 .0 i.h.p.) 
 
 1.885 
 1.078 
 
 14. 12 
 
 9-74 
 8.075 
 
 0.00018 
 0.000125 
 0.000104 
 
 1.402 
 0.965 
 0.805 
 
 * Clearfield run-of-mine 14,321 B.t.u. per pound as fired. Average thermal 
 efficiency of plant, 18.43 per cent; engine, 24.93 P er cent; producer, 73.81 per cent. 
 Average gasification rate, 13.36 pounds per square foot per hour. . 
 
424 
 
 THE GAS ENGINE 
 
 
 
 
 
 
 NO O 
 
 
 
 T2 M 
 
 i 
 
 CM M CO 
 
 CM t^ CO CO CM O 
 
 O 
 
 NO 
 
 00 Tf 
 
 oo oo t^ 
 
 5 2 
 
 NO 
 vo Tf O vo 
 
 2 2 
 
 o 
 
 
 
 CM OO CM r~- VONO 
 
 CO CM OO f- CO Tf 
 CO CO Tf Tf CO CM 
 
 i 
 
 CO 
 
 NO M ON 
 CM 
 
 NO 
 
 S ^ 
 
 Tf CN NO M 
 M M CM O 
 
 j 
 
 VO 
 
 M 
 
 
 
 
 
 
 
 
 
 
 NO 
 
 
 
 O 
 
 CO 
 
 
 NO 
 
 O t^-oo O O co 
 
 
 
 ON 
 
 H ON 
 
 co NO 
 
 ON M O Tf 
 
 
 1 
 
 ON O CM M NO CO 
 
 rj 
 
 CM 
 
 t^ CM 
 
 
 O VONO M 
 
 
 
 M M NO VO t* Tf 
 
 I/J 
 
 
 
 NO -3- 
 
 CS M CM M 
 
 2 
 
 
 CO CO Tf Tf CM CM 
 
 
 
 NO 
 
 
 
 s 
 
 
 O t^ co O 
 
 O 
 
 
 
 O 
 
 CM ^ 
 
 O "fr 
 
 O O 
 
 NO 00 
 
 CO 
 
 CO M 00 CM 
 
 
 
 NO 
 
 CM M NO NO O Tf 
 CO CO Tf Tf CO CM 
 
 M 
 
 If) 
 
 " 
 
 H CM O 
 VO M 
 
 NO 
 
 NO CO 
 
 NO Tf 
 
 ON NO CM O 
 
 M M CM M 
 
 N 
 
 f 
 
 OO CM CM VO O O 
 
 l> 
 
 8, 
 
 vo 
 
 CM !> 
 
 O ON CM 
 
 O NO 
 
 OO vo CO CM 
 
 
 CM 
 
 00 00 CM H CO O 
 CO co ON ON vo vo 
 
 c- 
 
 C^ 
 
 M 
 
 CM M ON 
 
 NO NO 
 
 NO Tf 
 
 M H M 
 M M M M 
 
 
 
 vo co Tf O O O 
 
 00 
 
 & 
 
 HO?S 
 
 8 8 
 
 VO VO H OO 
 
 
 M 
 
 Tf VO t~- r H O 
 
 r*3 
 
 ro 
 
 CO M O 
 
 f^. NO 
 
 COCO t^ ON 
 
 
 NO 
 
 VO COCO 00 Tf 10 
 CO CO Tf Tf CO CM 
 
 HH 
 
 ^c 
 
 M 
 
 ^ M 
 
 
 M HH 
 
 M M M M 
 
 OH 
 
 S 5 
 
 co CM vo O O O 
 
 
 
 N0 
 
 O O 
 
 VONO 
 NO 00 CM 
 
 & eg 
 
 00 
 
 VD 
 
 I 
 
 O NO M VO O VO 
 CM O vo Tf vo Tf 
 
 M 
 
 in 
 
 co 
 
 CM M ON 
 
 ON 
 VO 
 
 ? 
 
 ON ON VO M 
 M O CM M 
 
 Q 
 
 > > 
 
 CM 
 
 M Tf 00 VO O VO 
 
 8 
 
 NO 
 
 CO 
 
 NO O 
 
 00 O 
 
 CO t^- CM 
 
 a 
 
 t^ Tf 00 ON 
 
 3 
 
 i 
 
 
 ^ 
 
 ? 
 
 VO H ON 
 
 ON 
 
 VO 
 
 vo 00 
 
 NO Tf 
 
 NO O VO M 
 M H CM O 
 
 M M M H 
 
 
 1 
 
 VO 
 
 CM ONCO t^ M 
 
 i>- CM' Tf CM H 6 
 Tf vo O M M vo 
 co co vo vo -3- CM 
 
 M 
 
 f5 
 
 10 
 
 1O 
 
 !g 
 
 CO 
 
 CO t^ H 
 
 CO H ON 
 
 M 
 NO 
 
 O 
 O t^- 
 
 vo t^ 
 
 NO Tf 
 
 O ON HI vo 
 CO VO CM M 
 
 O O CM O 
 
 HH M H H 
 
 
 CM 
 
 ON ON CM Tf O M 
 
 ^ 
 
 g" 
 
 VO 
 
 CM CO 
 
 H NO VO 
 
 
 vo NO 
 
 NO Tf ^o 
 
 rf 
 
 < 
 
 OO ^t CM NO CM W 
 VO VO CM H IH VO 
 
 co co vo vo rt- CM 
 
 m 
 
 CO 
 
 vo 
 
 VO Tf 
 NO VO 
 
 ON ON CM OO 
 O M CM O 
 
 M M M M 
 
 S 
 
 
 NO CM t^ O O co 
 
 V) 
 
 P. 
 
 NO 
 
 CM CO 
 CO H Tf 
 
 80 
 00 
 
 CO CM O 
 
 3 
 
 'Y 
 
 CONO O vo O t>- 
 
 tr) 
 
 CM 
 
 CO CM O 
 
 VO CM 
 
 CM CO vo 
 
 
 CO 
 
 O O ^t" ^t" ON CO 
 CO CO 5 5 CM 
 
 M 
 
 
 
 NO 
 
 NO Tf 
 
 M CM 
 
 
 
 tj ; , 
 
 gi 
 
 J 
 
 -4 
 
 :-l"i| 
 
 : ! : 
 
 i :'-= : : 
 
 
 
 S J 5 
 
 ^ 
 
 CJ 1 
 
 -I ^ & Q. 
 
 ' S 
 
 ' c *' ' 
 
 d 
 
 
 I ^li 
 
 o 
 
 1* 
 
 . o * 9- 
 
 
 ^+1 x 'g 
 
 .2 
 
 
 "rt " g g g *rt 
 
 & 
 
 **N j 
 
 ^ M M ^ "^ 
 
 ^ n -9 t 
 
 <" _, <u <U OJ 
 
 & 
 
 
 3 ^ 8 8 w o 
 
 di 
 
 g ^ 
 
 : S.S.'S 
 
 fr Sfe 
 
 ^f -S'-l-i-i 
 
 
 
 ^ **t **^ H 
 
 >-s ' 
 
 a ^ 
 
 M -M a, 2 
 
 fl 
 
 > g > > > 
 
 
 
 ^ J ^^ || 
 
 j 
 
 ^ ^ 
 
 "5*2 13 > 
 
 <u <u 
 -r) ^-d 
 
 t *C t* tj ti 
 
 Co Q C3 Cy C3 
 
 
 
 M^PQPQO 
 
 H^H 
 
 -1 
 
 UUO< 
 
 
 L!J ^[1 
 
RESULTS OF TRIALS 
 
 425 
 
426 
 
 THE GAS ENGINE 
 
 I 
 
RESULTS OF TRIALS 
 
 427 
 
 TABLE XXVI. 
 
 Fuel Analysis. 
 5 1 -Hour Test of Gas Power Plant. soo-Horsepower Gas Engine. 
 
 
 
 
 
 
 
 B.t.u. per Pound. 
 
 Sample. 
 
 No. 
 
 Volatile 
 
 Matter. 
 
 Fixed 
 Carbon. 
 
 Mois- 
 ture. 
 
 Ash. 
 
 
 
 
 
 
 
 
 
 
 Dry. 
 
 Actual. 
 
 
 i 
 
 I9-I5 
 
 73-5 
 
 0.85 
 
 6-5 
 
 I43I3 
 
 14181 
 
 
 2 
 
 20. 12 
 
 73.60 
 
 1.09 
 
 5-i9 
 
 I453I 
 
 14360 
 
 
 3 
 
 2O.4O 
 
 73-3 
 
 0.70 
 
 5.6 
 
 14407 
 
 14306 
 
 Clearfield bitu- 
 
 4 
 
 18.30 
 
 75-40 
 
 0.90 
 
 5-4 
 
 14484 
 
 14347 
 
 minous* used 
 
 7 
 
 20.78 
 
 73.20 
 
 0.60 
 
 5-42 
 
 I453 1 
 
 14445 
 
 during test. 
 
 10 
 
 20.75 
 
 71.81 
 
 o-75 
 
 6.69 
 
 14345 
 
 14236 
 
 
 i5 
 
 19.70 
 
 74-79 
 
 0.90 
 
 4.61 
 
 14594 
 
 14457 
 
 
 18 
 
 19.30 
 
 76.40 
 
 I .00 
 
 3-30 
 
 14641 
 
 14486 
 
 
 20 
 
 20.43 
 
 71.41 
 
 1.05 
 
 7.11 
 
 14232 
 
 14069 
 
 Average of 9 samples. . 
 
 I 9 .8 7 
 
 73-7i 
 
 0.87 
 
 5-54 
 
 1445 
 
 14321 
 
 Anthracite for building 
 
 
 
 
 
 
 
 fires 
 
 5-20 
 
 78.95 
 
 3-20 
 
 12.65 
 
 12709 
 
 12320 
 
 Ash anthracite f 
 
 
 88.25 
 
 I - I 5 
 
 10.6 
 
 11977 
 
 11840 
 
 from under clinker 
 
 
 87 80 
 
 I 4.0 
 
 10.8 
 
 1 1946 
 
 1 1780 
 
 including ash in pro- 
 
 
 
 
 
 
 
 ducer ash pits 
 
 
 88.70 
 
 o. 70 
 
 ii .0 
 
 11946 
 
 1 1850 
 
 
 
 
 
 
 
 
 Averages 
 
 
 88.12 
 
 1. 08 
 
 10.8 
 
 11956 
 
 11823 
 
 * Sulphur in Clearfield Samples 2, 1.05 per cent; 10, 0,75 per cent; 20, 0.69 per 
 cent. Average, 0.83 per cent. 
 
 f See section of producer bed, Fig. 116. 
 
428 
 
 THE GAS ENGINE 
 
 Thermal Efficiency 
 
 Gas Power Plant 
 The Norton Co. 
 
 500 
 
 600 
 
 400 
 Load B.H.P. 
 
 FIG. 142. 
 
 The producer efficiency shown in this chart is based on the lower (effective) 
 heat value of the gas. 
 
RESULTS OF TRIALS 
 
 429 
 
 TABLE XXVII. t 
 
 Distribution of Heat at Average Load of 483 B.H.P. 
 
 5 1 -Hour .Test. 5oo-Horsepower Gas Engine. 
 
 
 Engine 
 
 5 only. 
 
 Entire 
 
 Plant. 
 
 
 Brake. 
 
 Elec. 
 
 Brake. 
 
 Elec. 
 
 Useful work 
 Electrical losses 
 
 24.9 
 
 22.98 
 
 I Q2 
 
 18.38 
 
 16.97 
 I 41 
 
 Friction and pump work 
 Jacket absorption 
 
 4-58 
 
 34. 22 
 
 4.58 
 JA 22 
 
 3-37 
 2 r 22 
 
 3-37 
 
 Exhaust and radiation (by bal ) 
 
 l6 3 
 
 ^6 T. 
 
 *;> ** 
 
 26 81 
 
 o z ^ 
 26 81 
 
 Loss in producer 
 
 
 
 26 22 
 
 
 
 
 
 
 
 
 IOO.OO 
 
 IOO.OO 
 
 100.00 
 
 100.00 
 
 TABLE XXVIII. 
 Speed Variation Tests. 5oo-Horsepower Gas Engine. 
 
 Speed, r.p.m 
 Volts 
 
 155 
 
 154.0 
 
 152.0 
 
 2C.7 . O 
 
 1-50.0 
 
 149.0 
 2?8.0 
 
 148.0 
 
 2 ?7 O 
 
 Amperes 
 
 
 327 . c. 
 
 66? . o 
 
 net o 
 
 1303. o 
 
 1347 O 
 
 Kw . . .? 
 
 
 86.1 
 
 170.8 
 
 246.6 
 
 336. I 
 
 346.O 
 
 B h p 
 
 
 I2O. 6 
 
 247 6 
 
 356. 5 
 
 489 1 
 
 503 o 
 
 Per cent full rating. 
 Speed drop, per cent 
 
 
 25-9 
 
 o 810 
 
 49-5 
 o 0^8 
 
 71.2 
 
 I ?.Q7 
 
 97-9 
 i 916 
 
 100.5 
 
 2 2 "?6 
 
 
 
 
 
 
 
 
 Instantaneous Load Test. 
 No load to full load, 280 volts, 1190 amperes, 345 kilowatts, 502 brake horsepower. 
 
 No-load speed 155 revolutions per minute. 
 
 Load thrown on 148 revolutions per minute. 
 
 Load thrown off 155 revolutions per minute. 
 
 Difference 7 revolutions per minute. 
 
 Speed variation 4.6 per cent of total; 2.3 per cent mean speed. 
 
430 
 
 THE GAS ENGINE 
 
 s 
 
 1 
 
 J 
 
 
 
 "S ^ 1 t' 
 
 
 
 bO 
 
 
 
 . HQO 1 
 
 
 
 | 
 
 ^" 
 
 
 s a 5 1 
 
 
 
 r-j 
 
 c5 
 
 
 w u o 
 
 
 
 
 3 
 
 
 r> J-H ^ ^ "*~* 
 
 
 
 
 
 i 
 
 
 j I d| H " ^ 
 
 
 
 | 
 
 
 
 g S rt S H 
 
 
 
 1 
 
 
 
 3 O" 4 "*^"^!^ >H > 
 
 
 
 M* 
 
 
 
 ^i C3 J> ^ r> O 
 
 
 
 ja 
 
 
 
 ' , J * v ^ 
 
 
 
 s~~*. p 
 
 
 
 O O 10 
 CNI vo O O ^O O W O 
 
 000 o, 
 O O ro rf 
 
 
 42 2 
 
 "S 
 
 w 
 
 
 
 M U"> CO M O4 MM 
 
 00 
 
 6 to ro 
 
 <T5O CS O) 
 
 s 
 
 B 
 
 ft 2 
 
 
 
 
 
 *" 
 
 8 
 
 
 
 
 
 .S 
 
 Q -5 
 
 
 
 OO^oOOO O IOM ^- 
 
 8 8S S 
 
 1 
 
 1 ; 
 
 G 
 
 
 
 t^* 10 T}~ 10 ^O OO O to O 
 
 to O PI O 
 
 M 00 CS <N 
 C^ d 
 
 
 O -4-> 
 
 
 
 to 
 
 M M 
 
 ^ 
 
 W+J 
 
 
 
 
 
 
 . 1 M 
 
 
 
 <N 
 
 80 ^c >o 
 
 ^o '0 
 
 HH ^ t3 
 
 
 
 
 ON Tf 
 
 "S ^ 
 
 R I' s w 
 
 X jri &> 3 
 
 w * 
 
 O 
 
 o 
 
 ^^-- ^ 1 "- 2 
 
 o o ** ^o 
 
 ^O (N) M M 
 M (S 
 
 *-B 
 
 "S 
 
 3 1 s a 
 
 
 
 o o 
 
 rj-QMOON O MOO '4 - 
 
 O O to 
 
 o o o o 
 
 c/3 vx 
 
 < O T3 <! 
 
 H ft 3 a 
 
 PQ 
 
 00 
 
 to t^ ^"^O ^ O ^0*0 ^O 
 
 (N(NOOtO<N t^. OOt^ O 
 
 MM (N MOM 
 
 O O* fO M 
 
 C C3 
 
 
 
 
 P*5 
 
 ON ON 
 
 
 Sv W3 
 DO 
 
 
 
 
 
 *0 "u 
 
 - -s 
 
 
 
 
 
 >H 
 
 Q 
 
 
 
 808^ ^ 
 
 
 
 O 
 
 
 M 
 
 oo' \d o ^ vd 
 
 
 
 
 42 OH 
 
 *^ 
 
 ^ 
 
 to M *O O 
 
 
 ^^ ^5 
 
 W 
 
 Hi 
 
 
 
 : ? g 
 
 
 J/ -t_^ 
 
 t: 6 ^ 
 
 
 
 
 : ^ ,_ 
 
 
 1 *! 
 
 CO T3 e 
 
 D <L) 
 
 
 
 j 
 
 ; If 
 
 
 2 </> 
 
 i ^ 
 
 
 
 g> :| . s d 
 
 JJ2 ^ 
 
 
 e 
 
 
 
 ^ S .. 3 
 
 ,S S- ! 
 
 
 " ^ 
 
 6 
 
 c 
 
 >H M ^ ^jj 1> M (_, 
 
 . 
 
 
 1 & 
 
 5 
 
 
 w> a ^ W g .^ _ e. 
 
 J u y' 
 
 
 1 8 
 
 2 
 
 1 
 
 d 
 
 4_>^ O .j fOO^^bO' 
 CO *J3 C . VM ^ ^4 *^ 
 
 l^ll : 
 
 
 S -^ 
 
 
 M 
 
 O p 1 ^ N *^ OU t. L, ^^ pH 
 
 r^ j> ^^ gj 
 
 
 8 8 
 
 
 ^ 
 
 ^ g 1 o^ "S | &ag gj 
 
 ^^-3-^ : 
 
 
 3 
 
 O 
 
 C/3 
 
 
 Duration 
 
 *" D fe tT U "^ 8 ' t2i 
 
 "O-^^aj*T3 **"* pP-i-><C 
 rf-3O^J5 . wrjO^Ci] 
 o i_I r73 X O 3 ctf ^^ QJ *"^ 
 
 ^^c^ a u o a 
 
 J|!l! 
 
 pq M * -t- 
 
 
RESULTS OF TRIALS 
 
 431 
 
 TABLE XXX. 
 Fractional Load Efficiencies of 5oo-Horsepower Gas Engine. 
 
 HOLDER DROP TESTS. 
 
 
 
 
 
 
 Over- 
 
 Nominal Load . 
 
 i 
 
 } 
 
 f 
 
 Pull. 
 
 load. 
 
 Load, brake horsepower 
 
 125 .00 
 
 25O.OO 
 
 37=C .00 
 
 500.00 
 
 550.0 
 
 Gas cons.,* cu. ft. perb.h.p. hr... 
 
 190.00 
 
 I27.OO 
 
 o / o 
 
 105.5 
 
 95.00 
 
 92.20 
 
 Heat cons.,* B.t.u. per b.h.p. hr. 
 
 2O2IO.OO 
 
 13510.00 
 
 11240.00 
 
 IOIOO.OO 
 
 9800 . oo 
 
 Heat cons.,* B.t.u. per kw.-hr. . . 
 
 30530.00 
 
 IQ700.00 
 
 16340.00 
 
 14675.00 
 
 14300.00 
 
 Heat cons.,* B.t.u. peri.h.p. hr. . 
 
 IIlSo.OO 
 
 10600.00 
 
 9050 . oo 
 
 8460 . oo 
 
 8295.00 
 
 t Thermal efficiency, per cent 
 
 
 
 
 
 
 brake 
 
 12 <8 
 
 18 84. 
 
 21.66 
 
 2 e 21 
 
 2C 07 
 
 $ Thermal efficiency, per cent 
 
 j.^ . ^u 
 
 X<_> l*Cf 
 
 
 *J * l 
 
 *o y / 
 
 electric 
 
 ii. 16 
 
 17.32 
 
 20.9 
 
 23-25 
 
 23-85 
 
 Thermal efficiency, per cent 
 
 
 
 
 
 
 indicated 
 
 22 7? 
 
 24 . 1 
 
 28. 14 
 
 30 . I 
 
 3O 7 
 
 
 / J 
 
 
 
 
 O 1 
 
 Equivalent Coal Consumption for Various Producer Efficiencies. 
 Pounds per Unit Hour. 
 
 Producer 
 Efficiency. 
 
 Coal Consumed per 
 
 Coal, pounds. 
 
 100 per cent 
 
 brake horse powerhour 
 
 I-4I3 
 
 0.994 
 
 0.785 
 
 75 
 
 0.685 
 
 
 kilowatt hour 
 
 2. 13 
 
 1.376 
 
 1. 141 
 
 i .025 
 
 0.999 
 
 80 per cent 
 
 brake horse powerhour 
 
 1.766 
 
 i. 812 
 
 0.980 
 
 0.882 
 
 0.857 
 
 
 kilowatt hour 
 
 2.663 
 
 i . 720 
 
 i .426 
 
 1.281 
 
 i .250 
 
 70 per cent 
 
 brake horse power hour 
 
 2.015 
 
 1-347 
 
 I . I2O 
 
 i. 006 
 
 0.977 
 
 
 kilowatt hour 
 
 3 4o 
 
 i .964 
 
 1.6 3 
 
 1.465 
 
 1.426 
 
 * Assuming same coal used on test 14,321 B.t.u. 
 
 t Motor efficiency as used in text of book. 
 
 { Motor efficiency x electrical efficiency. 
 
 Standard Gas 106.4 B.t.u. (effective), 62 degrees 30 inches Hg. 
 
432 THE GAS ENGINE 
 
 HEAT UNITS. 
 
 1 British thermal unit = 0.252 calorie (French). 
 = | of a pound -calorie. 
 = 778 foot-pounds. 
 
 1 Calorie (French) = 3.9683 British thermal units. 
 = 2.2046 pound -calories. 
 = 3091 foot-pounds. 
 
 1 Pound -calorie = 0.4536 calorie (French). 
 = i. 8 British thermal units. 
 
 = 1400.4 foot-pounds. 
 
 Molecular heat units : To reduce French calories to molecular heat units for 
 any substance, multiply the calories by the molecular weight of the substance. 
 Thus, the heat of one pound of carbon burned to CO is 1128 calories. The molec- 
 ular weight of carbon is 12. The molecular heat value of a pound of carbon 
 burned to CO is therefore 
 
 12 XII28= 13,536. 
 
 POWER. 
 
 1 Horsepower for 1 hour = 2545 British thermal units. 
 
 = 1,980,000 foot-pounds. 
 1 Horsepower for 1 minute = 42.416 British thermal units. 
 
 = 33,000 foot-pounds. 
 1 Horsepower for 1 second = .70794 British thermal unit. 
 
 = 550 foot-pounds. 
 
 PRESSURES. 
 
 760 mm. of mercury = 29 .922 in. mercury = 14.696 Ibs. per sq. in. 
 1 Centimeter of mercury = .19336 Ib. per sq. in. 
 1 Inch of mercury = .4908 Ib. per sq. in. 
 30 Inches of mercury = 14.724 Ibs. per sq. in. 
 1 Inch head of water = .577 ounce per sq. in. 
 = .0361 Ib. per sq. in. 
 
 THERMOMETER SCALES. 
 
 Degrees Fahrenheit = 1.8 X C + 32. 
 Degrees Centigrade = f (F - 32). 
 
INDEX. 
 
 ABN 
 
 ABNORMAL pressures, 268. 
 Abrasives for regrinding valve, 238. 
 Absolute zero of pressure, 286. 
 
 temperature, 286. 
 Accelerator for variable speed motor, 
 
 *55- 
 
 Accumulators, electric, 90. 
 Adiabatic change of gas, 384. 
 Adjustments, instructions for, 190. 
 Advancing the spark, 149. 
 Air, carbureted for gas, 360. 
 
 composition of, 296. 
 
 heating for mixture, 57. 
 
 moisture in, 320. 
 
 preheating for mixture, 58. 
 
 saturation of, with fuel, 56. 
 Air cooling the motor, 3. 
 
 Air gap width in spark plug, 79. 
 Air-gas making, 334. 
 Air jacket, 3. 
 
 Air lock in fuel supply system, 61. 
 Air pump for two-cycle motor, 25. 
 Air valve, compensating, 49. 
 Air valve of carbureter, 49. 
 Altitude and pressure decrease, 286. 
 Ammeter for testing electric batteries, 
 
 93- 
 
 Analyses, moisture in gas, 324. 
 Asphyxiation by exhaust gases, 177. 
 Aspirator for drawing gas from 
 
 mains, 362. 
 Atkinson motor, 15. 
 Atomic weights, table, 297. 
 Atomizer for heavy oil fuel, 38. 
 
 BAT 
 
 Automobile, adjusting carbureter on, 
 198. 
 
 compound motor, 42. 
 
 control of motor, 147, 153. 
 Automobile motor, air cooled, 8. 
 
 control of, 147, 153. 
 
 valve timing, 204. 
 
 BACKFIRING, 101, 235. 
 
 adjustment for, 193. 
 
 causes of, 214. 
 
 screen to prevent, 23, 27. 
 Back pressure, 180. 
 
 exhaust, 180. 
 
 indicator card showing, 271. 
 
 momentary increase of, 256. 
 
 Baffle plate on piston, 35. 
 Batteries compared for ignition, 93. 
 Battery, testing electric, 93. 
 
 accumulator, 90. 
 
 charging storage, 90. 
 
 charging, rectifier for alternating 
 current, 92. 
 
 connection for ignition, 88. 
 
 current of, 85. 
 
 dynamo and storage, for ignition, 
 106. 
 
 electric, for starting, 72. 
 
 elements of electric, 84. 
 
 exhausted, 89. 
 
 floated on the line, 106. 
 
 ignition, 83. 
 
 incorrect connections, 88. 
 
 multiple connected, 86. 
 
 433 
 
434 
 
 INDEX 
 
 BAT 
 
 Battery, multiple series, 87. 
 
 parallel connected, 86. 
 
 recuperating, 90. 
 
 series connected, 84. 
 
 storage, 90. 
 
 testing for positive and negative, 91. 
 
 troubles, 213. 
 
 voltage of, 84. 
 
 Battery coil of induction coil, 81. 
 Beau de Rochas cycle, 5. 
 Blast-furnace gas, 358. 
 Brayton cycle, theoretical, 401. 
 Bray ton motor, 27. 
 British thermal unit, denned, 276. 
 Bulb, ignition with hot, 34. 
 
 torch for heating, 35. 
 
 CALORIFIC power of fuel, denned, 296. 
 Calorimeter determinations and effi- 
 ciencies, 301. 
 
 tests of gas, continuous. 363. 
 
 error of, 364. 
 Cam, 12. 
 
 Cam shaft, speed of, 2. 
 Carbon, combustion table, 309. 
 
 in cylinder, 235. 
 
 removing, 236. 
 Carburation, 47. 
 
 of air, methods, 4. 
 
 surface, etc., 59. 
 
 to saturation point, 56. 
 Carbureter, adjusting on automobile, 
 
 198. 
 
 adjustment of, 191. 
 
 auxiliary flame for heating, 58. 
 
 cooled by vaporization, 57. 
 
 diaphragm feed, 53. 
 
 disk feed, 52. 
 
 double, 57. 
 
 early forms, 59. 
 
 float feed, 49. 
 
 freezing by vaporization, 57. 
 
 fuel supply for, 61. 
 
 COM 
 Carbureter, general types, 56. 
 
 heating, 57. 
 
 hot-water jacket for, 57. 
 
 ice and frost in, 57. 
 
 ice in, removing, 240. 
 
 in place, 2. 
 
 kerosene, 58. 
 
 leaky float, repairing, 239. 
 
 multiple nozzle, 51. 
 
 for non-volatile liquids, 58. 
 
 primer for, 47. 
 
 pump feed, 52. 
 
 repairs, 239. 
 
 spray nozzle, 48. 
 
 spray type in general, 54. 
 
 water in, 218. 
 
 waterlogged float, 239. 
 
 with water nozzle, 57. 
 Carbureter air valve, 49. 
 Carbureter measuring cup, 52. 
 Carbureter throttle, 49. 
 Carbureter troubles, 212. 
 Carbureter valve, 54. 
 Charge, large after cut-out, 263. 
 
 precompression of, 24. 
 
 saturated and diluted, 56. 
 
 stratification of, 27, 133. 
 Choke coil for ignition system, 71. 
 Coal, composition, chart showing, 
 
 407. 
 - table, 409, 414, 416, 427. 
 
 cubic feet of gas per pound, table, 
 412. 
 
 gas from, table, 410. 
 
 pounds per horse power, table, 413, 
 
 4*5> 4i7- 
 
 rate of gasification of, 410. 
 Coal gas, 333. 
 
 Coke, composition of, table, 416. 
 Coke oven gas, 359. 
 
 composition of, 360. 
 
 Combustible liquids, care and han- 
 dling, 243. 
 
INDEX 
 
 435 
 
 COM 
 
 Combustible mixture, range of, 4. 
 Combustion, change of specific 
 
 volume due to, 293. 
 chemical equations for, 297. 
 
 complete and incomplete, 295. 
 
 constant heat of, 296. 
 
 at constant pressure, 27. 
 
 denned, 4, 293. 
 
 drop of pressure after, 316. 
 
 extinguished by small ducts, 319. 
 
 imperfect, for over-rich mixture, 
 
 3*9- 
 
 pressures of, 316. 
 
 of producer gas, 312. 
 
 rate affected by compression, 151. 
 
 rate of, 317. 
 
 of retort gas, 313. 
 
 specific heat changed by, 396. 
 
 specific heat ratio changed, 397. 
 
 temperatures of, 20, 316. 
 
 time of, defined, 318. 
 
 unusual pressures of, 318. 
 
 variation of volume due to, 293, 
 
 395- 
 
 Combustion chamber, defined, r. 
 Combustion space, pockets in, 268, 
 
 3i7- 
 Complete expansion engine, 134. 
 
 indicator card, 260. 
 Compound motors, 41. 
 
 with two crank shafts, 43. 
 Compressed air for starting the mo- 
 tor, 38. 
 Compression, adjusting, 34. 
 
 curve for gas, 370. 
 
 economy gain by, 5. 
 
 efficiency affected by, 394. 
 
 heat of, for igniting, 37. 
 
 indicator card for variation of, 274. 
 
 lost suddenly, 236. 
 
 relieving, for starting the motor, 
 181. 
 
 varied by valve-chest cover, 27. 
 
 CRA 
 
 Compression cylinders for two-cycle 
 motors, 24. 
 
 Compression fuel tank, 53. 
 
 Compression space, defined, i. 
 
 Compression tanks for Brayton mo- 
 tor, 27. 
 
 Compression test by hand, 231. 
 
 Compressor plant, central, 28. 
 
 Compressors, auxiliary, 24, 27. 
 
 Condenser, electric, for induction 
 coil, 82. 
 
 Connecting rod, varying length to 
 adjust compression, 34. 
 
 Connections for gas motor, 33. 
 
 Constant pressure combustion, 27. 
 
 Control, accelerator for, 155. 
 
 of motor, 115. 
 
 throttle and spark, 153. 
 Conversion tables, 432. 
 Cooler, 165. 
 
 exhaust jets for, 16. 
 Cooling effect of vaporization, 57. 
 Cooling fan, 8. 
 
 Cooling flanges, 8. 
 Cooling system, 138. 
 
 troubles, 211. 
 Cooling the motor, 2, 3. 
 
 power affected by hot and 
 cool cylinder, 162. 
 
 methods, 162. 
 thermal circulation, 165. 
 
 by vaporization of water, 35. 
 water consumption, 421. 
 
 with air, 163. 
 with oil, 3, 168. 
 
 with water, 164. 
 
 Cooling water, adjusting flow of, 190. 
 
 heats unduly, causes, 220. 
 
 vaporized, 35. 
 Crank for starting, 8, 184. 
 Crankshafts, 2. 
 
 double, 43. 
 
 rotation of, per impulse, 44. 
 
INDEX 
 
 CUT 
 
 Cut-out indicator diagram, 259, 262. 
 Cycle of motor, defined, 5. 
 
 Beau de Rochas, 5. 
 
 Brayton, 27, 401. 
 
 diagram for complete theo- 
 retical, 371. 
 
 effect of imperfect gas, 
 
 398. 
 
 modifying causes, 399. 
 
 - Otto, 5. 
 
 Otto theoretical, 389. 
 
 theoretical heat, 374. 
 Cylinder, carbon deposit and re- 
 moval, 235. 
 
 cracked, cause of, 241. 
 
 cracked or porous, 230. 
 
 denned, i. 
 
 headless, 20. 
 
 open at both ends, 20. 
 
 pockets in, 268, 317. 
 
 scored, cause of, 241. 
 Cylinder heads, elimination of, 20. 
 Cylinder jacket, 3. 
 
 Cylinders, arrangement of, 44. 
 
 DEAD center of motor, 202. 
 Decomposition of gas, 315. 
 Deflector plate on piston, 36. 
 Density of gases, 284. 
 
 - table of, 285. 
 
 Diagram, nature for indicator, 373. 
 Diagrams, indicator, 251. 
 
 pressure- volume, 367. 
 
 Diesel motor, indicator card, 267. 
 
 Diesel oil motor, 37. 
 
 Dissociation of gases, 315. 
 
 Dynamo, see also Magneto and Gen- 
 erator. 
 
 Dynamo, automatic cut-out for, no, 
 in. 
 
 test of, 224, 227. 
 
 Dynamo-battery ignition system, 106. 
 
 Dynamo troubles, 214. 
 
 EXH 
 ECONOMY, 276. 
 
 based on calorimeter determina- 
 tions, 301. 
 
 of fuel, 277. 
 
 of motor, denned, 278, 279. 
 
 of plant, defined, 282. 
 Efficiencies, comparison of, 283. 
 Efficiency, 276. 
 
 compression effect on, 394. 
 
 free-piston motor, 40. 
 
 gas turbine, 3. 
 
 impulse-output of motor, defined, 
 279. 
 
 mechanical, of motor, defined, 280. 
 
 of motor, defined, 278. 
 
 of plant, defined, 282. 
 
 power plant, 366. 
 
 producer, equation for commer- 
 cial, 366. 
 
 producer, from trial, 422. 
 
 tar loss, 405. 
 
 thermal, of motor, defined, 281. 
 
 thermodynamic, defined, 281. 
 Electric generators, see also Dynamo 
 
 and Generator. 
 
 for ignition, 69. 
 
 Energy, equations for, 367. 
 
 unit of, defined, 276. 
 Engine, see also Motor. 
 
 "complete expansion," 18, 134. 
 Equalizer for gas pressure, 33. 
 Equations, general, for thermody- 
 namic change, 402. 
 
 Exhaust, asphyxiation by, 177. 
 
 auxiliary, 16. 
 
 back pressure of, 180. 
 
 back pressure, indicator card show- 
 ing, 271. 
 
 detection of CO in, 193. 
 
 momentary increase of back pres- 
 sure, 256. 
 
 mufflers, 1 78. 
 silencing, 177. 
 
INDEX 
 
 437 
 
 EXH 
 
 Exhaust, submerged, 179. 
 
 test for excess of fuel, 193. 
 Exhaust gases, disposal of, 177. 
 Exhaust jets for air circulation, 16. 
 Exhaust pipe for scavenging, 40. 
 Exhaust port, auxiliary, 8, 15. 
 Expansion, complete, in motor, 19. 
 Expansion, curve for gas, 370. 
 
 frequency of, 44. 
 
 Explosion pressures, abnormal, 268. 
 Explosions, sharp, 264. 
 
 local, in cylinder, 253. 
 
 FAN for cooling, 8. 
 
 Flame propagation, rate of, 257, 317. 
 
 Float, repairing leaky, 239. 
 
 Foot-pound, denned, 276. 
 
 Free-piston motor, 39. 
 
 Freezing of carbureter, 57. 
 
 Friction due to carbon deposit in 
 
 cylinder, 232. 
 Fuel, carburation with non-volatile, 
 
 58. 
 
 calorific power of, defined, 296. 
 
 composition, table, 427. 
 
 control of power and speed by 
 regulating, 115. 
 
 defined, 4. 
 
 economy of, 277. 
 
 excess of, detection in exhaust, 193. 
 
 heat value, defined, 296. 
 
 injecting liquid, 5. 
 
 mixing with air, 4. 
 
 per horse power per hour in service, 
 
 35i- 
 
 proportion range in combustible 
 mixture, 4. 
 
 pulverized, 4. 
 
 troubles, 212. 
 
 Fuel economy, pounds per horse 
 power, table, 413, 415, 417. 
 shown by commercial plant, 
 
 GAS 
 
 Fuel economy, trial for, 422. 
 Fuel mixture, rich and lean, 191. 
 Fuel oil, burning, 28. 
 
 injected by compressed air, 37. 
 Fuel pipes, 61. 
 
 Fuel pump, 52. 
 
 for oil, 30, 62. 
 
 Fuel supply for carbureter, 61. 
 Fuel tank, 53. 
 
 location of, for safety, 244. 
 Fuel valve, 10. 
 
 Fuels, 326. 
 
 for suction producer, 347. 
 
 GAS, adiabatic change of, 384. 
 
 analysis relative to moisture, 324. 
 
 blast-furnace, 358. 
 
 calorimeter tests, continuous, 363. 
 
 coke-oven, composition of, 360. 
 
 comparison of expansion lines, 388. 
 
 composition of, table, 408, 418, 
 419. 
 
 composition of, from trial, graph, 
 426. 
 
 compression curve of, 370. 
 
 cubic feet per pound of coal, 412. 
 
 expansion curve of, 370. 
 
 heat values, table, 309, 310, 410. 
 trial, 422. 
 
 imperfect, effect on theoretical 
 cycle, 398. 
 
 isobaric change of, 381. 
 
 isometric change of, 380. 
 
 isothermal change of, 382. 
 
 laws of perfect, 285, 375. 
 
 measuring, by drop of holder, 421. 
 
 moisture in, 320, 324. 
 
 observation of quality, 362. 
 
 petroleum gas, 360. 
 
 physical properties of, 284. 
 
 producer gas, combustion of, 312. 
 heat value from analysis, 
 
438 
 
 INDEX 
 
 GAS 
 
 Gas, producer gas, temporarily rich, 
 310. 
 
 removal of moisture from, 324. 
 
 retort gas, combustion of, 313. 
 
 specific volume, denned, 284. 
 
 thermodynamic changes, theoret- 
 ical, 379. 
 
 variation in quality from producer, 
 361. 
 
 Gas connections, 33. 
 
 Gas holder, measuring by drop of, 
 
 421. 
 Gas making, 326. 
 
 air gas, efficiency limit, 335. 
 
 air and carbon dioxide process, 
 350. 
 
 blowing the producer, 420. 
 
 calorimeter tests, continuous, 
 
 363- 
 
 carbureted air gas, 360. 
 
 combined suction and pressure 
 producer, 351. 
 
 continuous pressure producer, 
 348. 
 
 cubic feet per pound of coal, 
 table, 412. 
 
 distillation of volatile parts, 335. 
 
 economizer, 338. 
 
 efficiency basis, 365. 
 
 efficiency, equations for com- 
 mercial, 366. 
 
 efficiency from trial, 428. 
 
 efficiency of producer, trial, 422. 
 
 equations for proportions of 
 gases, 344, 346. 
 
 exhaust from motor fed to 
 producer, 350. 
 
 fuels for suction producers, 347. 
 
 gasoline gas, 360. 
 
 intermittent processes, 355. 
 
 intermittent, twin producers, 
 356. 
 
 meters for gas, 366. 
 
 GAS 
 
 Gas making, moisture separator, 338. 
 
 observation of quality of gas, 
 362. 
 
 oil-water gas, 360. 
 
 petroleum gas, 360. 
 -preheater, 338. 
 
 preheating air by motor 
 exhaust, 339. 
 
 - producer gas, 337. 
 
 producer, downdraught, 350. 
 
 producer plant, 352. 
 
 producer, underfeed, 350. 
 
 producers in pairs, 355. 
 
 producers, miscellaneous types, 
 
 354- 
 
 - purifier, 338. 
 
 rate of, table, 410. 
 
 - retort gas, 333. 
 
 scrubber for gas, 338. 
 
 stoking the fuel, 348. 
 
 tar destruction, 361. 
 tar loss, 405. 
 
 tar, quantity of, 349. 
 
 tar, table of, 409. 
 
 temporary richness of gas, 346. 
 
 theoretical case, 340. 
 
 variation in quality of gas, 361. 
 
 - water gas, 336. 
 Gas meter, 366. 
 
 Gas producer, suction type, 337. 
 
 - twin, 357. 
 -types of, 327. 
 
 Gas pump for two-cycle motor, 25. 
 Gas tank, 404. 
 Gas turbine, 3. 
 Gasification, rate of, 410. 
 Gaskets, 169. 
 
 stoppages by, 240. 
 Gasoline, care and handling, 243. 
 Gasoline gas, 360. 
 
 removing water from, 243. 
 
 straining, 243. 
 Gasoline pipes, 244. 
 
INDEX 
 
 439 
 
 GAS 
 
 Gasoline tank, location for safety, 
 
 244. 
 
 Gear, cam-shaft, 2. 
 Gears, marking, for replacement, 
 
 201. 
 Generator, electric, magneto, 101. 
 
 for ignition, 69. 
 
 oscillating, 73. 
 troubles, 214. 
 
 with interrupted magnetic cir- 
 cuit, 76. 
 
 Governing, 38, 116. 
 
 accuracy of different methods com- 
 pared, 157. 
 
 automatic cut-off, 125. 
 
 by exhaust valve, 119. 
 
 by fuel valve, 120, 130. 
 
 by inlet valve, 125. 
 
 by throttling, 122. 
 
 by varying amount of fuel per 
 charge, 122. 
 
 hit-or-miss, 117, 118. 
 
 large charge after cut-out, 262. 
 Governing and hand control, 116. 
 Governor, 123. 
 
 for oil motor, 32. 
 
 for timer, 155. 
 
 pendulum, 118. 
 
 Governors, centrifugal and hydrau- 
 lic, 146. 
 
 HAMMERING in motor, causes, 217. 
 Hand control, manipulation of, 147, 
 
 153- 
 
 Hand control and governing, 116. 
 Heat, distribution of, trial, 429. 
 
 latent, defined, 378. 
 
 sensible, 378. 
 
 specific, constant volume and con- 
 stant pressure, 378. 
 
 Heat cycles, theoretical, 374. 
 Heat value, deduction per pound of 
 hydrogen, 308. 
 
 1C.N 
 
 Heat value, deduction per pound of 
 steam, 308. 
 
 error of determining, 364. 
 
 from analysis, producer gas, 
 
 3- 
 
 lower, defined, 305. 
 
 of fuel, defined, 296. 
 Heat values, higher, defined, 305. 
 
 - of gas, table, 309, 310, 410. 
 
 of hydrogen, 305. 
 
 lower, defined, 306. 
 
 variable, in mixtures, 332. 
 Heat units, compared, 432. 
 
 molecular, 432. 
 Heating air for charge, 57. 
 Heating due to carbon deposit in 
 
 cylinder, 236. 
 
 Heating the carbureter, 57. 
 Hit-or-miss governing, 115. 
 Hornsby-Akroyd motor, 28. 
 indicator card, 266. 
 Horse power, defined, 276. 
 
 conversion table, 432. 
 
 indicated, 249. 
 
 Hose, loose lining in, 112. 
 
 Hot-tube ignition, 112. 
 
 Hot-wire ignition, 114. 
 
 Humidity, determination of, 325. 
 
 Hydrocarbons, 314. 
 
 Hydrogen, heat deduction per pound, 
 
 308. 
 
 heat values, 305, 306. 
 
 ICE, removing from carbureter, 240. 
 Igniter, double make-and-break, 66. 
 
 hammer blow type, 69. 
 
 insulation for, 67. 
 
 low-tension, with solenoid circuit 
 breaker, 72. 
 
 make-and-break, 64. 
 
 rotary, 68. 
 Ignition, 63. 
 
 accidental, sources of, 244. 
 
440 
 
 INDEX 
 
 IGN 
 
 Ignition, adjusting, 194. 
 
 adjusting the timer, 207. 
 
 advancing and retarding, 149. 
 
 advancing, for increased speed, 275. 
 
 alternating, current rectifier, 92. 
 
 at atmospheric pressure, 39. 
 
 batteries for electrical, 71, 83. 
 
 battery floated on the line, 106. 
 
 break-and-make, 64. 
 
 by compression in oil motor, 31. 
 Diesel motor, 37. 
 
 by hot vaporizer, 31. 
 
 by overheated motor, 113. 
 
 catalysis method, 114. 
 
 comparing time in different cylin- 
 ders, 208. 
 
 comparison of high-tension sys- 
 tems, 99. 
 
 contact points, material for, 66. 
 
 double, 63. 
 
 dynamo-battery system, storage 
 battery, 106. 
 
 dynamo cut-out, automatic, no, 
 in. 
 
 early and late, 148. 
 
 electric supply for, 69. 
 
 generators for electric, 66. 
 
 heating motor by late, 150. 
 
 high-tension distributer system, 98. 
 
 high-tension electric in general, 77. 
 
 high-tension magneto, 77. 
 
 hot-bulb, 34. 
 
 hot-metal, 113. 
 
 hot -tube, 112. 
 
 hot-wire, 114. 
 
 indicator card showing premature, 
 
 273- 
 
 indicator cards showing effect of 
 time variation, 271. 
 
 induction coil, 77, 81. 
 
 in small chamber, 253, 264. 
 
 jump-spark, 77. 
 
 lag of, 75, 149, 152. 
 
 IND 
 
 Ignition, late, indicator diagram, 265. 
 
 low-tension, 64. 
 
 magneto, 10. 
 
 magneto for jump-spark, 102. 
 
 make-and-break, 64. 
 
 one induction coil for two cylinders, 
 100. 
 
 pilot flame for, 27. 
 
 platinum-sponge, 114. 
 
 premature, 192. 
 
 reversal of motor by early, 150. 
 
 strength of spark variation, 274. 
 
 testing the batteries, 93. 
 
 time of, 13. 
 
 time affected by compression, 34, 
 
 151- 
 
 timer for, 77, 80. 
 
 timing- valve for hot-tube, 112. 
 
 wiring scheme, 95, 97. 
 Ignition system, choke coil for, 71. 
 desirable features of low -ten- 
 sion, 73. 
 
 in place, 2. 
 
 kick-coil for, 71. 
 
 testing, 221. 
 
 with magneto, jump-spark, 102. 
 Ignition troubles, 212. 
 Illuminants, 314. 
 
 Impulse, frequency of, 44. 
 Impulse-output efficiency defined, 279. 
 Indicated horse power, 249. 
 Indicator, stop and weak spring for, 
 248. 
 
 vibration of, 253. 
 
 Indicator card, complete expansion 
 engine, 260. 
 
 Diesel motor, 267. 
 
 effect of speed variation, 274. 
 
 effective or net area of, 247. 
 
 for dilute mixture, 273. 
 
 for two-cycle motor, 251. 
 
 Hornsby-Akroyd motor, 266. 
 
 impulse loop, 248. 
 
INDEX 
 
 441 
 
 IND 
 
 Indicator card, Koerting motor, 
 267. 
 
 late ignition, 265. 
 
 nature of, 373. 
 
 negative area of, 247. 
 
 negative loop, 248. 
 
 positive area of, 247. 
 
 positive loop, 248. 
 
 premature ignition, 273. 
 -pumping, 249. p 
 
 showing cut-out, 259, 262. 
 
 showing variation of compres- 
 sion, 274. 
 
 weak spring, 246. 
 Indicator cards from practice, 245. 
 
 representing American practice, 
 251. 
 
 showing effect of change of time 
 of ignition, 271. 
 
 valve setting incorrect, 268. 
 Indicator connections, 245. 
 Induction coils, 81. 
 Induction coil, condenser, 82. 
 
 for ignition, 77. 
 
 trouble, 213. 
 
 voltage for operating, 83. 
 
 without interrupter, 106. 
 Inflammation, 318. 
 Injecting liquid fuel, 5. 
 Injector nozzle for oil fuel, 31. 
 Interrupter of induction coil, 81. 
 Isobaric change of gas, 381. 
 Isometric change of gas, 380. 
 Isothermal change of gas, 382. 
 
 JACKET of cylinder, 3. 
 Jump-spark ignition, 77. 
 
 KEROSENE carbureters, 58. 
 Kerosene motor, 16. 
 Kick coil for ignition, 71. 
 Kicking of motor, 235. 
 Koerting two-cycle motor, 24. 
 indicator card, 267. 
 
 MIX 
 
 LATENT heat, denned, 378. 
 Launch motor, adjusting, 198. 
 Leakage shown on indicator card, 
 
 259, 262. 
 Leaks in motor, tests for, 230. 
 
 between cylinder and water 
 jacket, detection of, 232. 
 
 hydrostatic test for, 233. 
 Lignites, gas from, table, 410. 
 
 composition of, table, 409. 
 Lubrication, 171. 
 
 adjustment of, 190. 
 
 oil consumption by trial, 422. 
 Lubricators, 174. 
 
 MAGNETO, see also Dynamo and 
 
 Generator. 
 Magneto electric generator, 10, 70, 
 
 101. 
 
 high tension, 77, 102. 
 
 remagnetization of, 225. 
 
 test of, 224. 
 Mean effective pressure, 249. 
 
 equation for, 372. 
 Measuring cup of carbureter, 52. 
 Mechanical efficiency of motor, de- 
 fined, 280. 
 
 Metering gas, 366. 
 
 Mietz & Weiss oil motor, 35. 
 
 Misfiring, causes of, 216, 220. 
 
 test for, 223. 
 
 Mixture, combustible, 4. 
 
 dilute, indicator card showing, 
 
 273- 
 . effect of moisture in, 321. 
 
 heating air for, 57. 
 
 over-rich, detection by exhaust, 
 
 193- 
 
 over-rich, imperfect combustion 
 
 of, 319. 
 
 perfect, defined, 318. 
 
 perfect, rate of burning, 318. 
 
 proportioning device, 124. 
 
442 
 
 INDEX 
 
 MIX 
 
 Mixture combustible, rich and lean, 
 191. 
 
 saturated air, 4. 
 
 saturated and diluted, 56. 
 
 variable in heat value, 332. 
 Moisture in air and gas, 320. 
 
 determination of, 325. 
 
 gas analysis relative to, 324. 
 
 in mixture, effect on power of 
 motor, 321. 
 
 precipitation by cooling, 321. 
 
 precipitation by sudden expansion, 
 
 324- 
 
 reduced by compression, 324. 
 
 removal from gas, 324. 
 
 table, 322. 
 
 producer gas, 324. 
 Moisture separator, 338. 
 Motor, see also Engine. 
 
 air cooled, 8. 
 
 air pump for two-cycle, 25. 
 
 Atkinson, 15. 
 
 automobile, 8. 
 
 Brayton, 27, 
 
 capacity dependent on heat value 
 of mixture, 332. 
 
 cleaning, 235. 
 
 complete diagrammatic, 2. 
 
 compound, 41. 
 
 compression pumps for two-cycle, 
 
 ~3* 
 
 cooling, 2. 
 
 cylinder open at both ends, 20. 
 Diesel oil-burning, 37. 
 
 disabled, running of, 239. 
 
 efficiency, mechanical, denned, 
 280. 
 
 efficiency at part load, from trial, 
 
 43i- 
 
 efficiency by trial, 421, 428. 
 
 erratic behavior of, 219. 
 
 error of heat value unfavorable to, 
 365- 
 
 MOT 
 
 Motor, four-cycle, 7. 
 four-cycle Otto, 10. 
 
 four-cycle, not reversible, 46. 
 
 free-piston, 39. 
 
 fuel economy in service, 351. 
 
 fuel economy, table, 413, 415, 417. 
 
 gas pump for two-cycle, 25. 
 
 Gobron-Brillie, 20. 
 
 heat consumption of, 421. 
 Hornsby-Akroyd, 28. 
 
 kerosene, 16. 
 
 kicking of, 235. 
 
 - Koerting two-cycle, 24. 
 
 leaks, running test for, 231. 
 
 liquid fuel, 28. 
 
 mechanical efficiency of, denned, 
 280. 
 
 non -compressing, 5. 
 
 Nuremberg, 20. 
 
 oil-burning, 28. 
 
 oil-cooled, 3, 16, 168. 
 
 operation, method,- 5, 13. 
 
 operation of two-cycle, 22. 
 
 - pioneer, 39. 
 
 ports of, 10. 
 
 power affected by heat value of 
 mixture, 332. 
 
 priming, 50. 
 
 pumping loop for two-cycle, indi- 
 cator card, 251. 
 
 speed variation of governed, trial, 
 429. 
 
 starling, 181. 
 
 tandem, 14. 
 
 tests for leaks, 230. 
 
 three-port valveless, 22. 
 
 traction engine, 16. 
 
 two-cycle, 7, 21. 
 
 two-cycle, power capacity, 22. 
 
 two-cycle reversible, 46. 
 -types, i. 
 
 valveless, 22. 
 
 vaporizer for oil fuel, 28. 
 
INDEX 
 
 443 
 
 MOT 
 
 Motor economy, defined, 277. 
 Motor efficiency, defined, 278. 
 Motor guaranty based on calorimeter 
 
 determined values, 304. 
 Motor trials, results of, 16, 404, 430. 
 
 5oo-horsepower motor, 420. 
 
 graphic log of, 406, 425. 
 
 summary of, 423, 424. 
 Motor troubles, 210. 
 Muffler cut-out, 180. 
 Muffler for exhaust, 178. 
 
 NOZZLE for gasoline spray, 57. 
 for injecting fuel oil, 31. 
 Nuremberg motor, 20. 
 
 OIL-BURNING motors, 28. 
 
 - fuel for, 28. 
 
 Oil consumption, lubricating oil, trial, 
 
 422. 
 
 Oil-cooled motor, 3, 16, 168. 
 Oil fuel, atomizer for heavy, 38. 
 
 injected by compressed air, 37. 
 
 injecting system for motor, 32. 
 Oil gas from petroleum, 360. 
 
 Oil motor, adjusting, 199. 
 
 - Diesel, 37. 
 
 Oil pump for fuel, 30. 
 
 for lubricating oil, gear type, 
 
 139- 
 Otto cycle, 5. 
 
 effect of imperfect gas on, 398. 
 
 modified theoretical, 400. 
 
 modifying causes, 399. 
 
 theoretical equations, 389, 391. 
 Overheating and loss of power, 
 
 causes, 220. 
 ignition by, 113. 
 
 PACKING, materials for, 169. 
 Peat, composition of, table, 416. 
 Perfect gas, laws of, 285, 375. 
 Petroleum, gas from, 360. 
 
 POW 
 
 
 
 Pioneer motors, 39. 
 Pipe stoppages, 240. 
 Piston, area of, 249. 
 baffle plate on, 35. 
 
 cracked, gasoline test for, 242. 
 
 deflector plate on, 36. 
 
 leaky, cause of, 241. 
 
 oil-cooled, 3. 
 
 trunk type, i, 3. 
 
 water-cooled, 3, 167. 
 Piston rings, 3. 
 
 gummed, 236. 
 
 joints, 3. 
 
 leaky, 230. 
 
 loose, 242. 
 
 peening to expand, 241. 
 
 removing and replacing, 242. 
 
 Pitting of valve, 237. 
 Plant economy and efficiency, de- 
 fined, 282. 
 
 Platinum -sponge ignition, 114. 
 Pocket in combustion space, 268, 
 
 3i7- 
 Ports, i, 10, 19. 
 
 at middle of cylinder, 21. 
 
 auxiliary exhaust, 15. 
 Pounding of motor, causes, 217. 
 Power affected by heat value of mix- 
 ture, 332. 
 
 by preheating the charge, 60. 
 by time of ignition, 149. 
 
 conversion table, 432. 
 
 equations for, 250. 
 
 hand control of, 147. 
 
 unit of, defined, 276. 
 Power decrease, cause of, 218. 
 Power less than it should be, causes 
 
 of, 219. 
 
 lost suddenly, 236. 
 
 Power plant, distribution of heat, 
 
 trial, 429. 
 economy of operation, trial, 
 
 422. 
 
444 
 
 INDEX 
 
 POW 
 Power plant, efficiency, 366. 
 
 plan of, 420. 
 
 trial by holder drop test, 430. 
 
 trial, data from, 428. 
 
 trial, graphic chart, 425. 
 
 trial of, 404. 
 
 at Worcester, Mass., trial of, 420. 
 Precompression, 27. 
 
 for two-cycle motor, 24. 
 
 of air for charge, 27. 
 Preheating air for mixture, 58. 
 
 the charge, effect on power, 60. 
 Preignition, 235. 
 
 causes of, 217. 
 
 indicator card showing, 273. 
 Pressure, abnormal, of explosion, 268, 
 
 318. 
 
 relief valve for, 145. 
 
 absolute zero of, 286. 
 
 barometer and manometer, 432. 
 
 of combustion, 316. 
 
 of combustion, unusual, 268, 318. 
 
 decrease with altitude, 286. 
 
 mean effective, equation for, 372. 
 
 water and mercury, 432. 
 Pressure equalizer for gas, 33. 
 Pressure-volume diagrams, 367. 
 Primary coil of induction coil, 81. 
 Primer for carbureter, 47. 
 Priming the motor, 50. 
 Priming valve, 6, 185. 
 Producer gas, combustion of, 312. 
 
 composition, table, 408, 418, 
 419. 
 
 composition from trial, graph, 
 426. 
 
 heat value of, 422. 
 
 heat value from analysis, 311. 
 
 heat value, table, 410. 
 
 observation of quality, 362. 
 
 temporarily rich, 319. 
 variation in quality, 361. 
 
 ROT 
 
 Producer plant, 352. 
 Producer test, graphic log of, 406. 
 Producer trials, 404. 
 Producers, combined pressure and 
 suction type, 351. 
 
 continuous downdraught, 350. 
 
 continuous pressure type, 248. 
 
 continuous updraught, 328, 330. 
 
 efficiency basis of, 365. 
 
 efficiency from trial, 422, 428. 
 
 error of heat value favorable to, 365. 
 
 fuels for suction type, 347. 
 
 grate efficiency, equation for, 366. 
 
 miscellaneous types, 354. 
 
 suction type, 337. 
 
 twin, 355. 
 
 twin intermittent, 357. 
 
 types of, 327. 
 
 underfeed type, 350. 
 
 Pump for circulating cooling water 
 or oil, 16, 166. 
 
 for fuel, 52, 62. 
 
 for lubricating oil, 139. 
 
 packing for, 1 70. 
 
 Pumping card (indicator diagram), 
 
 267. 
 Pumping loop of indicator card, 248. 
 
 for two-cycle motor, 251. 
 
 Purifier for gas, 338. 
 
 RADIATOR, 16, 166. 
 
 Rectifier for alternating, electric cur- 
 rent, 92. 
 
 Regrinding a valve, 238. 
 
 Relief valve for compression, 6. 
 
 Retarding the spark, 149. 
 
 Retort gas, combustion of, 313. 
 making, 333. 
 
 Reversing rotation of motor crank- 
 shaft, 46. 
 
 Rings for piston, 3. ^ 
 
 Rotation of crankshaft per impulse, 44. 
 
INDEX 
 
 445 
 
 SAT 
 
 SATURATED mixture, 56. 
 
 Saturation and dilution of charge, 
 
 , 56. 
 
 Scavenging the motor, 40, 129. 
 
 Screen, wire, to prevent backfiring, 
 
 23, 27. 
 
 Scrubber for gas, 338. 
 Secondary coil of induction coil, 82. 
 Shaft, cam, 2. 
 
 crank, 2. 
 
 Smoke in exhaust, from fuel, 193. 
 from lubricating oil, 190. 
 Spark, variation of strength, 274. 
 Spark plug, 78. 
 
 air gap, width of, 79. 
 
 cleaning, 237. 
 
 testing, 222. 
 
 troubles, '212. 
 
 Spark-plug coil of induction coil, 
 
 82. 
 Specific heat of gases, defined, 289. 
 
 relation between constant 
 volume and constant pressure, 378. 
 
 table of, 290. 
 
 variation of, 316. 
 
 variation effects by com- 
 bustion, 396. 
 
 volumetric, 291. 
 
 Specific heats, change of ratio by 
 
 combustion, 397. 
 Specific volume of gases, defined, 
 
 284. 
 
 changed by combustion, 
 
 293, 39- 
 
 factor of variation for, 
 
 39- 
 
 table, 285. 
 Speed, hand control of, 147. 
 
 regulation of, 117. 
 
 Speed variation, effect on indicator 
 card, 274. 
 by trial, 429. 
 
 TJES 
 
 Spray nozzle, 57. 
 Springs, valve, 4, 119. 
 Starting the motor, 181. 
 
 battery for ignition when, 72. 
 
 blank cartridge for, 188. 
 
 by compressed air, 38, 145, 
 189. 
 
 by hand, 184. 
 
 by its own impulse, 186. 
 
 by mechanical power, 185. 
 
 crank for, 8. 
 
 on compression, 186. 
 
 - preparations for, 182. 
 
 relieving compression for, 
 181. 
 
 stresses due to, 188. 
 
 warming for, 185. 
 Steam, heat of, 302. 
 
 heat deduction per pound, 308. 
 Storage battery, 90. 
 Stratification of charge, 27, 133. 
 Supply tank for fuel, 53. 
 
 TANKS, compressed air, 37. 
 
 constant-level water tank, 36. 
 
 for fuel, 61. 
 - for gas, 404. 
 
 Tar, amount produced, 409. 
 
 burning apparatus, 350. 
 
 composition of, 315. 
 
 destruction of, in gas making, 361. 
 
 loss due to, 405. 
 
 quantity in gas making, 349. 
 Test for air and gas leaks, 230. 
 
 hydrostatic, 233. 
 with compressed air, 
 232. 
 Temperature, absolute zero of, 286. 
 
 of combustion, 20, 316. 
 Terminals of induction coil, 82. 
 Testing the ignition system, 221. 
 magneto generator, 224. 
 
446 
 
 INDEX 
 
 THE 
 
 Thermal circulation of cooling water, 
 
 165. 
 Thermal efficiency of motor, defined, 
 
 281. 
 Thermodynamic change, adiabatic, 
 
 384- 
 
 comparison of lines, 388. 
 
 constant pressure^ 381. 
 
 equations, general, 401. 
 
 isobaric, 381. 
 
 isometric, 380. 
 
 isothermal, 382. 
 
 of perfect gas, 379. 
 Thermodynamic efficiency, defined, 
 
 281. 
 Thermometer scales, conversion of, 
 
 432- 
 
 Throttle, 49. 
 
 Thumping of motor, causes, 217. 
 Timer for high-tension ignition, 80. 
 
 adjusting, 207. 
 
 adjusting, for reversing rotation of 
 motor, 46. 
 
 advancing, for increased speed, 
 
 275- 
 
 function of, 77. 
 
 governor for, 155. 
 
 speed of rotation of, 81, 100. 
 
 troubles, 213. 
 Timing the valves, 200. 
 Torch for heating hot bulb, 35. 
 Traction engine motor, 16. 
 Trembler of induction coil, 81. 
 Trial of motor, 16. 
 
 data from, 428. 
 
 Trial of power plant, 425. 
 
 at Worcester, Mass., 420. 
 by U. S. government, 
 404. 
 Troubles, remedies and repairs, 
 
 210. 
 
 Trunk piston, 3. 
 Turbine gas motor, 3. 
 
 VAL 
 
 Two-cycle motor, 21. 
 
 compression cylinders for, 24 
 
 Koerting, 24. 
 
 operation of, 22. 
 
 power capacity of, 22. 
 
 UNITS of energy, power and heat, 
 defined, 276. 
 
 conversion tables, 
 
 432. 
 
 VALVE, 4. 
 
 automatic inlet, 13. 
 
 auxiliary exhaust, 8, 16. 
 
 disabled, running motor with, 239. 
 
 fuel, ii. 
 
 inlet, hollow, 8. 
 
 method of opening, 13. 
 
 - pitting of, 237. 
 
 regrinding, 238. 
 
 relief, for high explosion pressure, 
 
 6, 145- 
 
 for starting motor with com- 
 pressed air, 187. 
 
 for timing ignition, 112. 
 
 - warping of, 237. 
 
 water-cooled exhaust, 127, 167. 
 Valves, i. 
 
 arrangement of, 31. 
 
 concentric, 8, 140. 
 
 testing, for leaks, 232. 
 
 timing of, 200. 
 
 Valve mechanism, 130, 136. 
 Valve setting, see also Valve timing, 
 200, 204. 
 
 indicator card showing, 268. 
 
 Valve spring, 4. 
 
 repairing, 239. 
 
 strength of, 119. 
 
 Valve stem, binding or sticking, 236. 
 Valve timing, see also Valve setting. 
 
 automobile motor, 204. 
 
 dead centers for, 202. 
 
INDEX 
 
 447 
 
 VAL WOR 
 
 Valve timing, effect of worn and loose Volume of gases changed by com- 
 parts, 206. bustion, 293, 395. 
 marking the flywheel for, specific, 285. 
 
 205. 
 Vaporization, cooling effect 
 
 57- 
 
 Vaporizer, ignition by hot, 31. 
 for oil motor, 28. 
 Vibrator of induction coil, 81. 
 
 Voltmeter for testing electric batter- 
 of, ies, 93. 
 
 WATER tank, constant level, 36. 
 Weights of gases, 284. 
 Work, equations for, 367. 
 
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 .087 
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