GIFT OF Daughter of William Stuart SmithU.S.Navv ENGINEERING ! 12 LOSS BY RADIATION OF ENTIRE PRODUCER BIO B.T.U. GAS, GASOLINE AND OIL ENGINES INCLUDING COMPLETE GAS ENGINE GLOSSARY A Simple, Practical and Comprehensive Book on the Construction, Operation and Repair of All Kinds of Engines. Dealing with the Various Parts in Detail and the Various Types of Engines and Also the Use of Different Kinds of Fuel. By JOHN B. RATHBUN, // Consulting Gas Engineer, Editor "Ignition," formerly Instructor Chicago Technical College, Author Gas Engine Troubles and Installation. 1919 CHICAGO ' PUBLISHERS 5 (COPYRIGHTED 1918 BY STANTON & VAN VLIET CO. DMH^ ENGINEERING LIBRARY TABLE OF CONTENTS CHAPTER I. Heat and Power. Heat Energy, Mechanical Equivalent of Heat, Expansion Heat Units, Heat En- gines, Efficiency, External and Internal Combustion Engines, Compression, Working Medium 5 CHAPTER II. Working Cycles. Definitions of Cycle, Four Stroke Cycle, Two Stroke Cycle, Two Port Two Stroke, Three Port Three Stroke, Reversing, Scavenging, Junker Two Stroke Cycle 26 CHAPTER III. Fuels. Calorific Values of Fuels, Solid, Liquid and Gaseous Fuels, Kerosene, Gasoline, Crude Oil, Producer Gas, Illuminating Gas, Coal, Benzol... 41 CHAPTER IV. Indicator Diagrams. Practical Use of the Indicator, Pressure Measurement, Reading the Card, Four Stroke Cycle Card, Defects in Practical Working, Two Stroke Cycle Card, Diesel Card, Effects of Mix- ture, Effects of Ignition 72 CHAPTER V. Typical Four Stroke Cycle Engines. Single Cylinder, Four Cylinder Automobile, Opposed Type, V Type, Tandem, Twin Tandem, Rotary Cylinder, Radial Diesel, Knight, Argyle, Rotary Valve 87 CHAPTER VI. Typical Two Stroke Cycle Engines. Two Port, Three Port, Marine, Controlled Port, Aeronautic, Oechehauser, Gnome Rotary Two Stroke, Koerting. . . 144 CHAPTER VII. Oil Engines. Elyria, Marine. Diesel In- stallation, Aspiration Types, Fairbanks Morse, Kero- sene Carburetion, Diesel, Semi Diesel, Combustion of Heavy Oils 160 CHAPTER VIII. Ignition Systems. Hot Tube System, Low Tension System, High Tension System, Details of Make and Break, Batteries, Low Tension Magnetos, High Tension Magnetos, Coils, Adjustment, Troubles.. 195 CHAPTER IX. Carburetors. Principles of Carburetion, Jet Carburetors, Water Jacketing, Fuel Supply, Differ- ent Types of Auto Carburetors, Adjustment of Car- buretor Troubles . 271 86G775 TABLE OF CONTENTS CHAPTER X. Lubrication. Forced Feed, Splash System, Oil Pumps, Lubrication Troubles 285 CHAPTER XI. Cooling Systems. Evaporation Systems, Radiators, Air Cooling 299 CHAPTER XII. Speed Governors. Automatic Station- ary, Adjustment, Mixture, Control, Hit and Miss, Mixed Systems 308 CHAPTER XIII. Glossary. Definitions of Gas Engine Words and Phrases 324 * I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I l_ i $IIIIIIIIIIIIQIIIIIIIIIIIOIIIIIIIIIIOIIIIIIIIIIO^ I 'GAS, GASOLINE AND OIL j ENGINES H iiiiiiiiiniiiiiiiiiiioiiimmiinmimimoiiiimiiiiniiiiiim^ "i I I i i i i I i I i I I i i i I i i i i i i i i i i i i i i i i i i I i I I I I I I r CHAPTER I PRINCIPLES OF THE HEAT ENGINE HEAT ENGINES. Heat energy and mechanical energy are mutually convertible; that is, heat energy can be converted into mechanical energy, and mechanical energy can be con- verted into heat energy. The production of heat through fric- tion is a very common example of the latter form of conversion, while the transformation of heat into mechanical energy is represented" by the steam and gas engines. Since these engines transform heat into mechanical force and motion they are known as "Heat Engines," to distinguish them from other forms of prime movers in which electricity or the kinetic energy of falling water is utilized as a source of energy. In both the gas engine and steam engine, the transformation is accomplished by the expansion of a heated gas or vapor, the temperature of the gas falling as the expansion proceeds, the energy liberated being proportional to the reduction in tem- perature. In practical heat engines, the heat energy is supplied to the gas or water vapor by a process known as "Combustion" a chemical combination of the atmospheric oxygen with sub- stances known as "Fuels." The fuels are carbon and hydrogen compounds such as coal, petroleum, or wood, and each sub- stance is capable of developing a certain definite amount of heat for every pound of weight. The fuel can therefore be con- sidered as a heat storage system since the original heat energy imparted to the fuel by the sun during the period of plant growth can later be liberated by the process of combustion. Nearly all fuels are the result of plant growth, the structure being modified by various conditions of pressure, aging, and atmospheric conditions imposed after the death of the plant. 5 6 HEAT ENGINES During combustion, the oxygen of the air combines with the carbon and hydrogen of the fuel to form other gases, commonly known as "Products of Combustion." These gases are entirely different in character from the original ele- ments of the fuel as they must always contain a percentage of chemically combined oxygen. For this reason, every fuel requires a definite amount of oxygen to burn it to its lowest form. The heat, of combustion is then applied to the gas used kt 'jtie expansio-n -(working medium). MECHANICAL EQUIVALENT OF HEAT. The unit of heat quantity used in this country is the British Thermal Unit. Numerically this is the amount of heat required to raise one pound of water through a temperature of one degree Fahrenheit. Thus, if one pound of water is raised from 40 to 60* F, the temperature increase will be 20, hence this will require the addition of 20 British Thermal Units (B. T. U.). If 100 pounds of water is used instead of one pound, the heat quantity will be increased 100 times, or 100 X 20 = 2,000 B. Y. U.'s. If any other working' medium than water is considered the results above must be multiplied by the "Specific Heat" of the substance. Thus if the specific heat of oxygen is 0.156, the number of B. T. U.'s required to raise 100 pounds through 20 Fahrenheit will be given by: 20 X 100 X 0.156 = 312.0 B. T. U.'s. It has been found by experiment that 778 foot-pounds of mechanical energy will produce 1 B. T. U., and conversely, 1 B. T. U. = 78 foot-pounds. The heat contained in the water of the above example will produce 2,000 X 778 = 1,556,000 foot-pounds of mechanical energy. If this heat is liberated in one minute, then 1,556,000 -i- 33,000 = 47.15 horsepower, the figure 33,000 being the number of foot-pounds per minute required for 1 horsepower. In actual practice we can hardly expect to utilize more than 30 percent of this power owing to the many losses that take place in a heat engine. From this problem it will be seen that we can determine the power of a heat engine if we know the heat supplied and the percentage of losses in the engine. ELEMENTS OF THE HEAT ENGINE. When heat is applied to a gas contained within a closed vessel, the pressure will rise with every increase in temperature, providing that the volume of the vessel is kept constant. If this vessel is pro- vided with a means of increasing or expanding the volume of HEAT ENGINES Section Through Four Stroke Cycle Aeronautic Motor, Showing Cylinder and Valves. 8 HEAT ENGINES the contents, the pressure will fall during the expansion if no more heat is supplied during this time. In the first case, where heat is supplied to the gas, energy is being given to the work- ing medium. During the expansion, the heat content is re- duced and work is being given up in giving motion to the ex- panding walls of the vessel. The production of mechanical energy by the heat engine therefore requires an alternate in- crease and decrease in the temperature of the gas. The most common method of obtaining mechanical effort from an expanding gas is to enclose it in a hollow cylinder, provided with a freely sliding piston as shown by Fig. 1. The movement of the piston provides a means of varying the volume and therefore permits the expansion of the enclosed working me- dium. Cylinder (c) is provided with the sliding piston (P), the latter being shown in two positions by the solid and dotted lines, the outer position being at (M) and the inner at (N). At the left end of the 'cylinder, the bore is closed by the wall or cylinder head (R). The heating chamber (B) is connected with the contents of the cylinder by the hollow tube (O), and the chamber (B) is heated by the lamp (L). In moving from the position (M) to (N), the piston turns the shaft (S) through the crank (X) and the connecting rod (T). Consider the bulb (B), and the space between the cylinder head and the piston at (M), to be filled with some gas such as air, this being at a comparatively low temperature. The lamp (L) is now placed under the bulb (B), and the temperature of the enclosed air is greatly increased. This results in an increase in pressure and the piston moves to the right, or from (M) to (N), thus performing mechanical work on the driving shaft (S). If the lamp is removed at the instant that the piston starts to move, the increasing volume will cause a reduction in the pressure and temperature. After the piston has reached the outer end of the stroke at (N), the temperature must be reduced to the original temperature, or the pressure must be re- leased before the piston returns to its original position. When returned to (M), more gas is heated, and the piston performs a second working stroke, and so on, a continuous production of mechanical effort being produced by an alternate heating and cooling of the working medium. An increased amount of work can be obtained by applying heat continuously through the working stroke and thus maintaining a higher working pressure. In practice, the charge is not cooled at the end of the stroke, but is allowed to escape to the atmosphere under pressure, HEAT ENGINES 9, but the final result is the same in either case as far as heat economy is concerned. In Fig. 2 the heating of the working medium is obtained in another way. The medium in this case consists of a mix- ture of air and some combustible gas, such as coal gas or gasoline vapor. With the piston at (H), and the space J-H L. Fig. 1 Shows Heat Applied Externally to Cylinder C by the Lamp Fig. 2 Shows the Combustion of the FueJ Taking Place within the Cylinder. filled with the inflammable mixture, a spark is applied to the gas and combustion occurs directly within the cylinder bore. This increases the temperature tremendously, and the pressure due to the combustion drives the piston (P) to the right, turn- ing the crank (G). As no more heat is applied after the piston leaves (H), the gas expands and decreases in pressure during the stroke. At the point (I), the pressure is reduced by open- ing a valve to atmosphere, thus allowing the piston to be re- turned to (H) for the next power impulse. 10 HEAT ENGINES TYPES OF HEAT ENGINES. According to the method adopted in supplying heat to the cylinder, heat engines may be di- vided into two principal classes: (1) External combustion engines in which the combustion occurs outside of the cylinder walls as in Fig. 1, and (2) Internal combustion engines in which the com- bustion is completed within the cylinder as in Fig. 2. The steam engine is an example of the external combustion engine while the gas engine is an internal combustion type. Both types have been used with great success, but the adoption of either of the engines depends upon the conditions of the service. Each en- gine has its particular fields of usefulness With the internal combustion engine, a greater percentage of the heat is applied usefully to the piston, the only losses being those due to radiation and the exhaust. The fuel must be supplied in gaseous form. The many heat losses of the ex- ternal combustion type are to some extent compromised by the possibility of burning cheap, readily accessible fuels, and in some cases the external combustion engine is actually cheaper to run than the internal combustion type owing to local fuel and labor conditions. THE STEAM ENGINE. Fig. 3 shows the layout of an ele- mentary steam plant. Heat is supplied by the burning fuel (C), under the boiler (B), the heat being transmitted to the water (W) by contact with the flames, and by the heat passing 1 through the tubes (X). The steam from the boiler passes to the engines cylinder (E) through the steam main (R). The products of combustion caused by the burning of the fuel escape from the firebox through the smoke stack (S), and these gases carry a considerable amount of heat with them. Heat is also lost by radiation from the boiler and piping. The piston (P) slides freely in the bore of the cylinder (E), and is connected with the shaft through the piston rod (H), the connecting rod (G), and the crank (F). The belt J-J transmits power from the fly-wheel (I) to the machinery that is to be driven. Steam from the boiler enters the valve chest (A) by the pipe (R), and from this point the steam is alternately admitted and exhausted from the cylinder ends (L) and (K) by the valve (V). This engine is of the double acting type, that is, steam is alternately admited on either side of the piston (P) so that pressure is applied twice per revolution. The arrange- ment is such, that while steam is being admitted to one end, it is allowed to escape from the other end through the exhaust HEAT ENGINES 11 pipe (N). The valve is operated from the crankshaft through the valve rod (H). A detail of the valve action is shown by Fig 3a in which the piston (P) is moving to the right as indicated by the arrow. The live boiler steam enters the cylinder through the port (g) as shown by the arrows, and the exhaust escapes through the port (h), the exhaust cavity (M), and the exhaust Fig. 3. Steam Engine Operation. pipe (Z). Fig 3b shows the valve position when the piston is moving in the opposite direction, the exhaust now being through the port (g), and the live steam admission through port (h). The valve shown is the simple "D" type, but on the modern engine this is considerably modified and elaborated upon. The speed is held constant at different loads by varying the period of steam admission to the cylinder, the valve re- maining open for a shorter part of the stroke with a light load than when the engine is heavily loaded. A modern engine gen- 12 HEAT ENGINES erally cuts off the steam at about one-quarter of the stroke when running at the rated power, and at about one-half stroke when fully overloaded. From the point of cut-off the steam expands to the end of the stroke, and by this expansion the quantity of steam used per horsepower is much reduced below the consumption that would result from allowing the steam to follow the piston throughout the length of the stroke even with a smaller cylinder. The valve travel is regulated by a cen- trifugal or inertia type governor. Fig. 4. Diagrammatic View of Elementary Gas Engine Using Liquid FueJ. Vapor is Formed at J, Enters Cylinder H Through the Inlet Valve B, and is Ignited by Spark Plug C. Explosion Drives Back Piston P, the Burnt Gas Then Being Exhausted Through Exhaust Valve A and Pipe M. THE GAS ENGINE. The most common form of gas engine or internal combustion engine is shown by Fig 4. The cylinder barrel (H) contains the single acting piston (P), the latter being connected with the crank (F) by the connecting rod (G). While gas engines of large size are made with double acting pistons, by far the greater majority are single acting with the pressure applied at one end as shown. The cylinder is sur- rounded with the water jacket (W) which prevents overheating by the successive combustions. The combustible gas mixture is HEAT ENGINES 13 admitted to the cylinder through the admission or inlet valve (B), while the burnt or exhaust gases are allowed to escape through the exhaust valve (A), and the exhaust pipe (M). When gaseous fuels such as illuminating or producer gas are used they are mixed with the proper amount of air in a mixer con- nected to the inlet valve, so that when the latter opens, the suc- tion of the piston fills the cylinder with a combustible mixture through the inlet valve. When liquid fuels such as gasoline or kerosene are used, the liquid is sprayed in with the proper amount of air. The heat vaporizes the-^pray and forms a highly combustible gaseous mixture. The spraying and proportioning of the liquid fuel is performed by a device known as a car- bureter, and is shown in its simplest form by (J). The fuel- nozzle (J) extends into the inlet pipe, and during the suction stroke, sprays the liquid fuel into the entering air at the end of the pipe. The spray consisting of very finely subdivided particles is vaporized by a slight addition of heat, and forms a combustible mixture. The spray nozzle (J) is connected to the fuel tank (T). With the inlet valve (B) open, and the piston moving to the right on the suction stroke, the cylinder is filled with the mixture. The inlet valve closes near the end of the suc- tion stroke, and on the return stroke the mixture is com- pressed to a comparatively high pressure. At the end of the compression stroke at the left, a spark occurs at the spark plug (C), which ignites the compressed mixture, and starts the combustion. The increased pressure due to the combustion drives the piston toward the right on the "power" or "working stroke," and near the end of this stroke the exhaust valve (A) opens and relieves the pressure. This sequence is followed in the "four stroke cycle" type of gas engine. A preliminary compression of the mixture is necessary to increase the final working pressure. Within certain limits, the higher the compression the higher will be the explosion pres- sure. A great deal depends upon the proportion of the mixture and its uniformity. There should be just enough air to com- plete the combustion of the gas or oil vapor. If the air and vapor are not thoroughly mixed, the combustion will not be complete, and hence some of the fuel will be expelled through the exhaust. A particle of air must be in contact with every particle of fuel for complete and instantaneous combustion. The spark should occur at the point of highest compression, or rather the combustion should be completed before the piston 14 HEAT ENGINES has moved far on the working stroke. If the combustion is slow, much heat will be wasted to the walls and through the exhaust. Under proper conditions the temperature of com- bustion in a gas engine cylinder is very high, probably being between 2,500 and 3,000 degrees Fahrenheit. COMPARISON BETWEEN INTERNAL AND EXTER- NAL COMBUSTION ENGINES. The efficiency, or fuel econ- omy, of any heat engine depends upon the range of tem- peratures during the period of expansion. If the steam or burning gas at the beginning of the working stroke has a very high temperature and is then expanded to a very low temperature at the end of the stroke the efficiency will be much higher than with a low initial or high exhaust temperature. If the gas is not expanded down to a low temperature, much heat will be lost when the exhaust valve is opened to the atmos- phere. The theoretical efficiency is the relation of the heat reduction in the cylinder to the total heat supplied. Thus, if the working medium (gas) is heated to 3,000 degrees at the be- ginning of the working stroke, and is reduced to 500 degrees at the end of the stroke, just before the exhaust opens, the tem- perature range in the cylinder will be 3,000 500 = 2,500 degrees. The efficiency will be the ratio of the temperature range to the initial temperature, or 2,500-1-3,000 = 0.833 (83.3 percent). As- suming that the initial temperature is only 1,500 degrees, but with the exhaust temperature still at 500 degrees, then the theoretical efficiency will be: 1,500 500-4-1,500 = 0.666 or 66.6 percent. This does not take the mechanical efficiency of the working parts into account, and hence is often known as the "Thermal efficiency." With steam engines the initial temperature is practically limited to about 500 Fahrenheit since a higher temperature would result in almost unmanageable steam pressures. The pressure of steam increases much more rapidly with a given temperature than with air or any fixed gas, hence the initial temperature in internal combustion engines may be much higher than that employed with steam engines. If saturated steam is raised to 500 the corresponding pressure will be about 700 pounds per square inch, a pressure that is almost impossible to handle satisfactorily under practical working conditions. With air as the working medium, a temperature of 3,000 does not cause prohibitive stresses in the material, HEAT ENGINES 15 16 HEAT ENGINES There are many other losses in the steam plant, such as radiation and friction losses in the steam pipes, radiation from the boiler settings and engine surfaces, heat loss up the stack, power required for auxiliaries such as feed pumps, cylinder con- densation, etc. While the temperature in the boiler furnace approximates 2,000, the temperature of the steam at the cylinder is only in the neighborhood of 350, or 16 percent of the furnace temperature. By generating the saturated steam at a com- paratively low pressure and temperature, and then "superheating it after its generation, the economy of the steam engine has been considerably increased. Unfortunately the temperature of the superheat is limited and is much lower than in the gas engine. The superheat reaches this limit at about 550 to 600 degrees. The efficiency of a modern steam plant equipped with super- heaters is only about 20 percent, while an internal com- bustion engine of the Diesel type may exceed 40 percent. SUPERHEATING AND CONDENSING. Fig. 5 shows a diagram of the method adopted in increasing the temperature range of a steam plant by means of the superheater and con- denser. The superheater increases the temperature of the steam supply while the condenser reduces the temperature of the steam rejected. In practice, either method is often used inde- pendently. Saturated steam is generated at the required pressure in the boiler (K), the hot gases of combustion passing up through the flues (L), and out at the stack. A pipe coil, or equivalent, called the "Superheater," (M) is placed in the smoke box (B) where it is subjected to the heat of the waste gas. One end of the superheater coil is connected with the boiler at (J), the other end of the coil being connected with the steam engine cylinder (N) by the pipe (A) so that the boiler steam passes through the superheater coil on its way to the engine cylinder. Heat is thus supplied to the steam without burning extra fuel since the heat added is that which would otherwise pass up the stack. This increase in temperature does not increase the pressure but simply increases the heat contents. The exhaust from the engine passes to the condenser coil (E) through the pipe (D), the condenser coil being contained in a condenser tank (F) filled with cold water. On striking the cold walls of the tubes the heat of the exhaust steam is ab- sorbed, and the steam is condensed, thus creating a partial vacu- um in the condenser coil and the exhaust pipe (D). Instead of HEAT ENGINES 17 18 HEAT ENGINES exhausting against the atmosphere the engine now exhausts against a much lower pressure which in effect is equivalent to increasing the steam pressure. Thus, if the atmospheric pres- sure is taken at 14.7 pounds per square inch, and the pressure in the condenser as 5.0 pounds, it is equivalent to adding 14.7 5.0 = 9.7 pounds per square inch to the boiler pressure. When exhausting to atmosphere, the steam temperature is above 212 degrees, but as the exhaust temperature depends upon its pressure, it is evident that the condensed steam rejected from the condenser is much below 212 since the condenser pressure is below the atmospheric. This increases the tem- perature range by lowering the temperature of rejection. An "Air pump" (G) is connected to the lower end of the condenser coil which pumps out the water of condensation as at (O). Cold water circulation in the condenser is maintained by the circulating pump (H) and this is rejected at (I). Both the water (O), and the rejection water (I) flow into the "Hot well" (S). From the hot-well, the warm water is drawn through the pipe (P) by the pump (Q), and is fed into the boiler through the pipe (R) to make up for the water lost by evaporation. Some of the heat contained in the rejection water from the condenser is thus returned to the boiler and is saved, but as the water required for condensation is many times the quantity used by the boiler, a greater part of the heat from the con- denser is wasted. Some steam is also wasted in driving the condenser pumps (G) and (H), so that condensing is not a clear gain. A plant exhausting directly into the atmosphere, without a condenser is known as a "Non-condensing plant." As the steam escapes at a higher temperature the exhaust losses are higher, but this is to some extent overcome by the fact that the exhaust steam can be used to heat the feed water to a higher temperature than can be attained with the condenser. The feed water heater, like the condenser generally consists of a coil of pipe surrounded by a shell, the pipe being filled with the boiler feed water while the outer space surrounding the pipe is filled with exhaust steam from the engine. The water is heated to from 200 to 210 degrees. The heater not only affords fuel econ- omy but also reduces the stresses and strain on the boiler shell that would result from the injection of cold water into the hot boiler. Owing to the low temperature of the water taken from the hot well of condensing plants (110 to 130 degrees) an addi- tional feed water heater is used which uses the exhaust steam HEAT ENGINES 19 20 HEAT ENGINES from the feed, air, and circulating pumps for raising the tem- perature of the hot well water. MULTIPLE EXPANSION ENGINES. When the steam is expanded in a series of cylinders instead of the single cylinder illustrated, there is a smaller heat loss by condensation within the cylinders. An engine in which the expansion is carried out in more than one cylinder is known as a "Multiple ex- pansion engine" and may be compound, triple expansion, or quadruple expansion according to whether the expansion is carried out in two, three, or four stages. In a compound engine, the boiler steam is first admitted to the small "High-pressure cylinder," and when a part of the expansion is performed, exhaust enters the larger low pressure cylinder in which it is further expanded. The low pressure cylinder must be considerably greater in volume than the high pressure in order to accommodate the increased volume of steam due to the first expansion. In a triple expansion engine, the partially expanded steam from the high pressure cylinder passes into a large cylinder known as the "Intermediate." After a second expansion in the intermediate, the steam is discharged for the final expansion in the low pressure cylinder. This is a very complicated engine and is only suitable for very large engines used in marine service or in water works. Compound gas engines have been repeatedly proposed by people not familiar with gas engine conditions, believing that the same saving would result from successive expansions of the gas, as in the case of the steam. The very reverse is true, since in the use of two cylinders, more heat is absorbed by the more greatly extended cooling surface of the cylinder walls. The cylinder walls of a steam engine are insulated so that there is little heat loss by radiation, and hence the multiple cylinder idea is perfectly practicable. In the case of the gas engine, all of the cylinder wall surface must necessarily be cooled, hence any increase in wall surface due to the addition of cylinders leads to an additional heat loss to the jacket water. STEAM TURBINES. Since power is the result of a force in motion, we can obtain the same results with a great pres- sure and small velocity as in the case of the steam turbine piston, or we can expand the steam to a high velocity and utilize the energy of impact on the running wheel blades of HEAT ENGINES 21 a steam turbine. In both cases the benefits of expansion are realized, but according to different methods. With the steam turbine, steam under pressure is allowed to issue from a nozzle into a lower pressure, with the result that the steam expands in proportion to the pressure on the discharge side of the nozzle, and the velocity of the stream is enormously increased. The potential energy is thus partly or entirely converted into kinetic energy. The stream of steam on striking a surface such as the Partial Section Through Four Cylinder Automobile Engine Showing Cooling Radiator R. "Paddle" or blade of a turbine wheel creates a driving force and turns the turbine wheel. Essentially, a steam turbine consists of a series of stationary nozzles and a series of small blades mounted on the periphery of a running wheel. The velocity of the wheels is very high to compensate for the low pressure of impact, and for the most efficient results the blade velocity should be about two-thirds of the jet velocity. This cannot be attained in practice owing to the limiting whirling strength of our materials, hence the ex- 22 HEAT ENGINES pansion is carried out in a number of wheels, so that the nozzle velocity at any one stage of expansion is comparatively low. By restricting the expansion at each set of nozzles the velocity can be kept so low that the running wheel velocity can be made to more nearly meet the ideal speed relation. In water turbines, the velocity of the water is so low that it is an easy matter to get the correct relation between the velocity of the water and the running wheel in one stage, or with a single wheel. Like the water turbine, the steam machine can be divided into two principal classes; the impulse and reaction types. All turbines, .however, work on the same elementary principles; that is, motion and power are obtained by the impact of a fluid stream on a series of blades attached to one or more running wheels. During the past few years there has been considerable ex- perimental work done with gas turbines but as yet nothing of a practical nature has been developed. The high temperatures attained by the burning gas, and the necessity of compressing the combustible mixture have been some of the greatest obstacles to the success of the gas turbine. In one turbine, the running wheel is surrounded by a series of combustion chambers, which alternately are filled with the compressed mixture, fired, and then discharged through nozzles on the blades of the run- ning wheels. This of course requires a compressor for the compression of the charge and a rather elaborate system of valves, etc. To withstand the high temperatures, the blades have been made of carborundum or other refractory material, or steam has been injected to reduce the final temperature at the blading. The accompanying figure shows a gas turbine described by A. W. H. Griepe in the Gas Engine. The rotating member (Fig. 1) is similar to that used in a reaction type steam turbine with the blades distributed in four equally spaced groups around the periphery of the wheel. Each group occupies one-eighth of the circumference. On the inside of the rotor spider, carrying the blades, is a valve band R which acts as an admission and cut-off valve between the explosion chamber and the fuel-air supply. The inner stationary element or "Stator" contains the four explosion chambers E-E-E-E, the air chamber, and the fuel chamber, the fuel and air chambers being arranged in the form of rings around the shaft. Compressed air enters the air chamber from the storage tank at from 45 to 74 pounds per square inch, and the gas from the fuel chamber enters at prac- tically atmospheric pressure. The turbine is in duplicate with HEAT ENGINES 23 24 HEAT ENGINES two sets of nozzles and explosion chambers, so that when one side has been ignited and is expanding, the explosion chambers on the other side of the wheel are taking in a charge of explosive mixture. This gives approximately a constant turning effort on the turbine wheel. The nozzles leading out to the wheel blades from the explosion chambers E-E-E-E are staggered on opposite sides of the wheel, the nozzles on the right being turned one- eighth of a revolution from those on the left, or so that they lie between the nozzles on the left. In Fig. 1, the wheel is in a position where the nozzles leading from the explosion chamber to the wheel bades are closed at the outer end, and where the ring R has opened the admission from the fuel and air supply into the explosion chambers. (On the near side.) The compressed air enters through the passage in- dicated by the curved arrows, and in entering acts as an injector in drawing the fuel in through the small straight nozzle in the center of each valve. (Shown by the straight arrows.) This continues until the wheel has revolved into the position shown in Fig. 3. In Fig. 3 it will be seen that the ring valve R has closed the passage between the air and fuel supply, and the explosion chamber, and also that the nozzles are now open between the explosion chamber and the turbine blades. The valve R closes communication between the explosion chamber and fuel supply an instant before the nozzles are opened to the blades. At this instant the charge is ignited and expands. The ring R now opens one side of the air chamber, with the ends of the nozzles still open and before the gas port opens to the chamber E. This allows a blast of pure air to sweep through the explosion chamber E and cleans out the burnt gas before the explosive mixture enters for the next explosion.. The cycle of events is as follows: 1. Ring opens to compressed air which blows out the burnt gas remaining from the previous explosion. 2. Valve opens and admits combustible mixture of air and fuel into explosion chamber, and the mixture is compressed by the continued flow of compressed air into the chamber. 3. Valve entirely closes explosion chamber, ignition takes place, and maximum explosion pressure is reached. 4. Nozzle is opened, and the gas escapes and expands into the blades of the running wheel producing power. After the expansion the same cycle is repeated. An experimental turbine of this type produced from 85 to 90 horse- HEAT ENGINES 25 power at 2,500 revolutions per minute, the efficiency being approximately 20 per cent. In starting, the pressure on the fuel was about 3 pounds, but after a short run, the nozzles acted as an injector and sucked the fuel into the explosion chamber making a carburetor unneces- sary. A heating coil in the base was used to assist vaporization. It is claimed that the combustion never was the cause of any trouble. The rotating blade sections were of cast iron, and were inserted in the rotor, and on the experimental tests have stood up well although it is possible that they would not be so satisfactory in long continued practical service. The thickness ranges from y% inch near the edge to % near the center, and fringing or abrasion only occurred at points where the core left a thin edge. It would seem, however, that a more refractory substance would be necessary for a commercial turbine, for if a thin edge frayed out in so short a time it would not take long to go through a plate only ]/$ inch thick. CHAPTER II WORKING CYCLES (24) Requirements of the Engine. In order that an internal combustion engine shall operate and develop power continuously the following routine of events must occur in the cylinder in the following order, no matter what the type of -engine. (1) The cylinder must be filled with a combustible mixture of air and gaseous fuel at as nearly atmospheric pressure as possible. (2) The mixture must be compressed in order to develop the value of the fuel. (3) Ignition must take place at the end of the compression stroke or at the highest point of compression. (4) Complete combustion of the fuel must follow the ignition of the charge, with an increase of temperature and pressure which will act on the piston to the end of the power stroke. (5) After the piston has completed the working stroke the products of combustion must be ejected from the cylinder com- pletely to make way for the admission of the new combustible mixture. With the exception of the Diesel engine which (1) fills the cylinder with pure air without the fuel, and (2) injects the fuel after compression, all internal combustion engines not only per- form each of these operations but proceed with events in the order given as well. The accomplishment of the five acts is called a "cycle of events," or a "CYCLE," and the series is per- formed in different ways in different types of engines. In the operation of the engine, the series of events occur over and over again, always in the same order, 1-2-3-4-5, 1-2-3-4-5, 1-2-2-3-4-5, etc. The five events are generally given in terms of the num- ber of strokes of the piston taken to accomplish the complete routine, thus a two stroke cycle engine performs the series in two strokes, and a four stroke cycle engine in four strokes, and so on. In order to obtain the benefits of high compression, perfect 26 CYCLES 27 scavenging of the products of combustion from the cylinder and perfect mixtures, a great variety of engines have been developed in which the number of strokes taken to accomplish the five events varies. In some engines the cycle is accomplished in two strokes, in other engines it is accomplished in six strokes, but in the great majority of cases the cycle is performed in either two or four strokes, and as these are by far the most common routines, we will confine our description to engines of these types. (25) Four Stroke Cycle Engine. The four stroke cycle engine, some times improperly called the "four cycle" engine is the most widely used type for all classes of service, except possibly for marine work. Its ex- tended use is due to its superior scavenging, high efficiency and reliability, although it is somewhat more complicated than the two stroke cycle type. Its ability to function properly under a wide variation of speed has driven the two stroke cycle type out of the automobile field, and its many admirable character- istics have cut a wide swath in the marine field, the stronghold of the two stroke cycle type. A four stroke cycle engine performs the cycle of events in four strokes or two revolutions, only one of the strokes being a power of working stroke. In a single cylinder engine the ex- plosion in the working strokes supplies enough power to the fly-wheel to carry the engine and its load through the remain- ing three strokes. Thus the energy stored in the fly wheel is sufficient to carry not only the load during the idle strokes but to "inhale" and compress the charge as well. Due to the long interval that exists between explosions, they are corresponding heavy and are productive of heavy strains in the engine and are the cause of considerable vibration. To reduce the ill effects of the heavy intermittent blows, the majority of automobile and stationary engines are provided with two or more cylinders, the power being equally divided among them. In a four cylinder engine, there are four times as many impulses as in a single cylinder engine and the blow . dealt by the individual cylinder is only one-quarter as great. While a single cylinder engine has an impulse only once in every other revolution, the four cylinder has two impulses in one revolution. Besides the advantages gained by increasing the impulses, the mechanical balance of a multiple cylinder en- gine is always better than that of a single and is also much 28 CYCLES Fig. 4. Diagrammatic View of Four Stroke Cycle Engine with the Piston in Various Positions Corresponding with the Five Events. Diagram A Suction. Diagram B Compression. Diagram C Ignition. Dia- gram D Working Stroke. Diagram E -Release. Diagram F - Scavenging Stroke. CYCLES 29 lighter in weight since less material is required to resist shocks of the explosions. Engines with more than four cylinders have "overlapping" impulses, that is some cylinder on the engine is always deliver- ing power, for before one cylinder reaches the end of the stroke, another has fired its charge and has started to deliver power. Thus the impulses "overlap" one another, and the result is an even and smooth application of power and a minimum of strain is imposed on the engine. Aeronautical and speed boat engine builders have carried the multiple cylinder idea to an extreme because of the nature of their work. Eight cylinder aeronautical engines are very com- mon and there are several built having sixteen cylinders. The latter type of engine gives eight impulses per revolution. To avoid a great multiplicity of cylinders, and to save on floor space, the great majority of heavy duty stationary engines are built double acting, that is an explosion occurs alternately in either end of the cylinder. In effect, a double acting cylinder is the same thing as a two cylinder single acting engine, as it gives twice the number of impulses obtained with a single acting cylinder. The order in which the events occur in a four stroke cycle engine is as follows: STROKE 1. First outward stroke of the piston causes a par- tial vacuum in the combustion chamber thus drawing a charge of combustible gas into the cylinder through the open inlet valve. The exhaust valve is closed. See diagram A in Fig. 4. (Suction Stroke.) STROKE 2. Inlet valve closes at the end of the suction stroke and the piston starts on the inward stroke compressing the charge in the combustion chamber. See diagram B. (Com- pression Stroke.) At the end of the compression stroke, or a little before, the spark "S" occurs causing the ignition of the charge. See diagram C. STROKE 3. Working Stroke. As the pressure is now estab- lished in the cylinder, the piston moves down on the working stroke forcing the crank around against the load and supplying sufficient energy to the fly wheel to carry the engine through the three idle strokes. See diagram D. When the piston reaches the end of the working stroke, or a little before, the exhaust valve opens to reduce the pressure and to allow the greater part of the burnt gas to escape. See diagram E. STROKE 4. Scavenging Stroke. The exhaust valve remains open and the inwardly moving piston expels the remainder of 30 CYCLES the burnt gas through the exhaust valve, clearing the cylinder for the next fresh charge of mixture. See diagram F. The next stroke is the suction stroke explained under "Stroke 1." In all of the diagrams the crank is supposed to turn in a right handed direction as indicated by the arrow, the piston moving in the direction shown by the arrow under the piston head. The valves are operated by cams on an intermediate shaft known as the "cam shaft." As the valves go through their series of movements in two revolutions of the crank shaft, and as the cam shaft must perform all of these operations in one revolution, it is evident that the cam shaft must run at exactly one-half the crank-shaft speed. This change of speed is accom- plished by means of gearing between the cam shaft and crank- shaft from which the cam shaft is driven. In some engines, notably the Diesel engine, pure air is drawn into the cylinder on stroke No. 1 instead of the entire mixture. Fuel is supplied in this type immediately after the end of the compression stroke. While an electric spark is shown as the igniting medium in the diagrams, the ignition is sometimes performed by a hot tube, or simply by the heat of the compression as in the Diesel engine. In the sliding sleeve type of four stroke cycle motor, the poppet or lifting type of valve as shown in Fig. 4, is replaced by a peculiar type of slide valve similar in action to the slide valves used on steam engines, except that it is cylindrical in form and entirely surrounds the piston. While there is a change in the form of the valve, and in a number of small details, the gases are drawn into the cylinder, compressed, ignited, and re- leased in exactly the same way and in the same rotation, as in the poppet valve engine just described. A description of the Knight engine which is the most prominent example of the slide sleeve motor will be found in a succeeding chapter. Since the success of the slide valve type has been acknowledged by many prominent automobile manufacturers, there have been several similar types placed on the market, some with two sleeves and some with one, but in all cases the designers have had but two points in view, that is quiet running and free passages. (26) Two Stroke Cycle Engine. Two stroke cycle engines perform the five events of aspiration (suction), compression, ignition, expansion and release in two strokes or one revolution. Providing that these events are per- CYCLES 31 formed as efficiently as in the four stroke cycle engine, it is evident that with equal cylinder capacity, the two stroke cycle engine would have twice the output of a four stroke cycle since it gives twice the number of impulses per revolution. Un- fortunately it is impossible to attain twice the output of the four stroke cycle type with the small two stroke engines built at the present time because of their imperfect scavenging and poor fuel economy. In the larger two stroke engines, the pumps and blowers used for scavenging the cylinders consume a con- siderable percentage of the output. A general classification of the two stroke cycle engine is not so simple a matter as that of the four stroke because of the DIAGRAM A. TTR5T- STTTOKE' DIAGRAM C- SECOND STROKE Fig. 5. Diagram of Two Port Two Stroke Cycle Engine, Showing the Events in the Crank-Case and Cylinder. differences in construction of large and small sizes. This dif- ference between the large stationary engine and the small type commonly used on boats is due to the efforts of the builders of the large engine to obtain great fuel economy, while the chief endeavors of the builders of small engines is to build a simple and reliable engine for the use of inexperienced persons. While the smaller type of two stroke engine (less than 25 horse- power) has not been used in stationary practice to any extent, owing to the defects just named, or on automobiles, it has been widely used on motor boats, a service for which it is peculiarly adapted. Its extended use on boats is due to the fact that in such service it runs at practically a constant speed and works 32 CYCLES against a steady load, the conditions that are most favorable to the type. With automobiles where the motor speed is constantly varying, as well as the load, this type of motor is not flexible enough to meet the continually varying conditions. The small two stroke motors are divided into two principal classes, the two port and three port type, depending on the method by which the charge is transferred to the cylinder. No valves are used in the cylinders of either type for the admis- sion or release of the gases. As the two strokes of the cycle are the compression stroke and working stroke, it is evident that the charge must be introduced into the cylinder by means other than by the suction of the piston and at a time when there is no pressure in the cylinder. This is accomplished by a pre- liminary compression of the charge in the crank case which places the mixture under sufficient pressure to force it into the cylinder at the end of the working stroke and at the same time to displace the burnt gases left from the previous explosion. It should be noted that the incoming mixture is a substitute for both the suction and scavenging strokes of the four stroke cycle engine. A diagrammatic view of a two port, two stroke cycle engine is shown by Fig. 5, in which P is the piston, C the crank case, I the transfer port, V the inlet valve, E the exhaust, and S the spark plug for igniting the charge. It should be noted that there are no valves in the cylinder and only three moving ports. The cycle of events for the two port type is as follows: STROKE 1. We will consider the piston to be moving up on the compression stroke as shown in view (A), compressing the mixture in the combustion chamber D. While moving upwards in the direction of the arrow, the piston creates a vacuum in the crank case C drawing fresh mixture into the crank case. The piston at this time is covering the opening of the transfer port I and the exhaust port E so that the compressed mixture in the cylinder cannot escape. On reaching the end of the com- pression stroke, a spark occurs at S which drives the piston down and turns the crank towards the right as shown by the arrow. STROKE 2. When the piston uncovers the exhaust port E on its downward working stroke as shown by view B, the exhaust gases being under pressure rush out into the atmosphere as shown by the arrows, and relieve the pressure in the cylinder. Some of the burnt gas remains in the cylinder at atmospheric pressure as there is no scavenging action up to this point. While the piston has moved down on the working stroke it has com- CYCLES 33 pressed the mixture in the crank case ready for admission to the cylinder. The valve V prevents the escape of the gas dur- ing the compression. On reaching the end of the stroke the piston uncovers the transfer port which allows the compressed mixture in the crank case to rush into the cylinder through I, as shown by view C. Owing to the shape of the deflector plate Z on the piston head, the stream of mixture issuing from I is thrown up toward the top of the cylinder, as shown by the arrows, and consequently sweeps the remainder of the burnt gas before it through the exhaust port E. In this way the fresh mixture from the crank case scavenges the cylinder and fills it in one operation. Being filled with gas, the piston now moves up on the compression stroke for the next explosion as shown by view A. Unfortunately the scavenging action of the incoming gas is not complete for the whirling motion of the charge causes it to mix with the residual gas to a certain extent which, of course, reduces the heating effect of the fuel and reduces the power output. Another factor that reduces the output of this type of engine is the loss of explosive mixture through the ex- haust port at low engine speeds with an open throttle. In this case, the piston speed being low, part of the mixture has time to pass over the deflector plate and through the exhaust opening before the piston closes the exhaust port. At very high speeds the charge is diluted by a considerable quantity of burnt gas which has not had time to escape through the port causing a further loss of power. With the throttle nearly closed on a light load, the impact of the incoming mixture is so slight that the percentage of exhaust gas left in the cylinder is very high. This dilution is so great that with moderately low speeds (easily within the capacity of the four stroke cycle engine) it is either impossible to ignite the charge or it is im- possible to ignite two in succession. In marine service where the loads are constant, and the speeds fairly uniform, there is but little trouble from the last mentioned source, and as the fuel is usually a smaller item than the repair bill, the simplicity of the small two stroke en- gine with its freedom from mechanical troubles usually gives satisfactory results in the hands of the novice. (27) Three Port Two Stroke Cycle Engine. The principal difference between the three port and two port types of the two stroke cycle engine is in the manner in which 34 CYCLES the charge is admitted to the crank case for the initial compress- ion. In the two port motor, as previously described, the check valve "V" opens to admit the charge, and closes during its com- pression in order to prevent its escape through the opening by which it was admitted to the cylinder. With the three port type there is no check valve in the crank case, the admission and the retention of the charge being controlled by the move- ment of the piston in practically the same way that the piston controls the opening and closing of the exhaust and transfer ports in the cylinder. Fig. 6. Fig. 7. Figs. 6-7. Diagram of Three Port Two Stroke Cycle Engine in Two Positions. By the piston control of the gases in the crank case, the valve is eliminated, which makes one less moving part to cause trou- ble and expense, and permits the use of the same type of car- buretor that is used on the four stroke cycle engine. As the check valve opens and closes at a high speed, (twice that of the valves on a four stroke cycle engine), there is considerable wear on the valve seats due to the continuous banging, which results finally in a loss of the initial compression. When the initial compression is reduced in this way the engine loses power because of the reduction of the charge in the cylinder. While the three port type is free from valve leakage troubles, CYCLES 35 it has a steady loss due to the high vacuum that exists in the crank chamber when the piston is on its upward stroke. This vacuum drags against the piston and absorbs a considerable amount of power until the piston reaches the upper end of the stroke. At this point the inlet port is opened and the vacuum is broken by the rush of the mixture through the in- let port. Besides the power loss, the vacuum has a bad effect on the lubrication of the main crank shaft bearing. Described by strokes, the cycle of events in the three port, two stroke cycle engine is as follows: Elevation of Fairbanks-Morse Three-Port Two Stroke Marine Motor Show- ing Warming Device for Carburetor Air. STROKE 1. In Fig. 6, the piston is shown at the end of the compression stroke with ignition taking place in the combustion chamber C. The pressure due to the expansion drives the piston down on the working stroke at the same time causing the initial compression of the mixture in the crank case as shown by Fig. 7. The gas in the crank case cannot escape during compression as the inlet port A is covered by the piston. (a) As the piston descends, its upper edge uncovers the ex- haust port D, allowing the greater portion of the exhaust gases to escape and reduces the pressure in the cylinder to that of the atmosphere. 36 CYCLES (b) Descending a little farther, the top of the piston uncovers the opening of the transfer port B, allowing the compressed gases in the crank case to enter the cylinder as shown by the arrows. These gases, guided by the deflector plate on the top of the piston are thrown upwardly, as shown by the arrows, and sweep the residual burnt gases before them through the exhaust port. The cylinder is now filled with the combustible mixture ready for compression. STROKE 2. The piston now moves up on the compression stroke, compressing the charge in the cylinder and at the same time creates a vacuum in the crank-case. Just before the piston reaches tne end of the exhaust stroke, the lower edge of the piston uncovers the inlet port A (See Fig. 7), which allows the mixture from the carburetor to flow into the partial vacuum and fill the crank case ready for the next initial compression. When the end of the stroke is reached, the charge in the com- bustion chamber C is fired and the cycle is repeated. It should be noted that the incoming gas and the initial compression are controlled entirely by the action of the lower edge of the piston on the inlet port A . (28) Reversing Two Cycle Motors. As the admission and exhaust in the two stroke cycle engine each occur once per revolution, 'and are controlled directly by the piston position at opposite ends of the stroke, it is evi- dent that the direction of rotation is not affected by gas con- trol or valve timing, as in the case of the four stroke cycle en- gine. The factor that does determine the direction of rotation in the two stroke engine is the time at which ignition occurs in regard to the angular position of the crank. By changing the relation between the crank position at the end of the com- pression stroke and the time at which the spark occurs, it is possible to reverse the engine even when it is running. Should the engine be standing still in the position shown by Fig. 6, with the crank on the dead center, when ignition oc- curred, there would be no more tendency to turn the crank to the right than to the left, providing of course, that there was no effect from the momentum of a revolving fly wheel. If igni- tion occurred with the crank inclined ever so little toward the right, the pressure of the piston would force the crank down- wards in a right handed direction. If the crank were inclined to the left, the tendency would be for left handed rotation. If the ignition system were arranged so that the spark oc- CYCLES 37 curred when the crank was inclined towards the right every time that the piston came up on the compression stroke, we should have continuous rotation in a right hand direction. By shifting the sequence of the spark so that it occurred with the crank on the left we would cause the engine to stop and re- verse to left handed rotation. This is exactly the method used in reversing two stroke motors in practice, the change in the CYLINDER HEAD WATER BY PASS TO MANIFOLD WATER JACKET INLET AND EXHAUST MANIFOLD EXHAUST PORT WATER BY-PASS Jj TO CYLINDER HEAD TRANSFER PORT PISTON RING PISTON PIN PISTON PIN BUSHING OIL GROOVE PLEATED SCREEN IN TRANSFER PASSAGE CONNECTING ROD CRANKSHAFT OJPPEB CRANK CAS CONNECTING ROD BUSHING HIPPER HALF LOWER HALF DUCT FROM OIL RING TO CRANK LOWER CRANK CASE CONNECTING ROD CAP L SCOOP Fig. F-9. Cross Section of Fairbanks-Morse Three Port Two Stroke Cycle Engine, with Parts Named. ignition being accomplished by advancing or retarding the mechanism that dispatches the spark ("Timer" or "Commu- tator"). This is an advantage not possessed by the four stroke cycle engine of the ordinary type, as the cams and valve mechanism require reversal as well as a reversal of the ignition system. This relation between the valve action and rotation in a four stroke cycle engine may be illustrated by the following example. 38 CYCLES Consider the piston at the end of the compression stroke in an engine designed for right hand rotation. After ignition, under the proper conditions, the piston would descend turning the crank to the right until it reached the bottom of the stroke, at which point the exhaust valve would open and relieve the press- ure in the cylinder. Let us now consider an attempt at reversing the engine by causing the spark to occur before the piston reached the end of the compression stroke with the crank still inclined toward the left. In this case the piston would force the crank down in a left hand direction until it reached the end of the stroke. The exhaust valve would not open to relieve the pressure, as the exhaust cam would be moving away from the valve rod in- stead of toward it. Should the crank swing a little past the dead center, because of its momentum, the inlet valve would be opened instead of the exhaust, and the contents of the cylinder would shoot through the intake pipe and carburetor. This would bring matters to a close as far as rotation was concerned. The opening of the inlet valve on the reversed working stroke would occur as the inlet valve closes one stroke, or one-half revolution, before the end of the compression stroke. As the engine turned backward one-half revolution, the inlet cam would again be brought into contact with the inlet valve rod, opening the valve and allowing the burned gases to pass through the carburetor. Should the pressure be sufficiently reduced by in- let valve to allow the piston to reach the end of the second stroke, it would start on the third stroke by inhaling a "charge" of burnt gas through the exhaust valve which would now be open. (29) Scavenging Engines. As the piston does not sweep out all the cylinder volume be- cause of the space left at the end of the cylinder for compression, more or less burned gas remains in the combustion chamber which dilutes the active mixture taken in on the suction stroke. Not only are the residual gases useless in generating heat but they also occupy a considerable space in the cylinder that might otherwise be filled with a heat producing mixture. Their dilut- ing effect also prevents the complete combustion of a certain percent of the fuel actually taken into the cylinder for which the burnt gas is incapable of supporting combustion. The amount of burnt gas remaining in the cylinder depends upon the cycle of the engine and also upon the valve timing CYCLES 39 and size of the exhaust piping. In the four stroke cycle en- gine the volume of residual gas is equal to the volume of the combustion chamber, in the two stroke cycle it varies from one-tenth to one-third of the entire cylinder volume, depend- ing on the load and speed. With correct design and free ex- haust passages, the gas held in the clearance space of a four stroke cycle engine is at a pressure considerably below that of the atmosphere, and consequently its actual volume is even less than the volume of the combustion chamber. Many systems have been devised for the purpose of clear- ing the cylinder of burnt gas in order to minimize the loss of fuel in large engines, but owing to their complication have never been successfully applied to small engines of the automobile or marine types. In general, the "scavenging" is accomplished by pumping out the clearance space at the end of the scaveng- ing stroke, while fresh air is admitted to the cylinder through the inlet valves, or by blowing out the clearance space by a blast of pure air furnished from an air pump attached to the engine. There have been several systems proposed by which the gas in the cylinder is withdrawn by the inertia of the exhaust gas in specially designed ejectors, and by the compression of fresh air in the crank case of the engine. The former system known as "organ pipe ejection," is by far the simplest method of all as the ejector is simply a tube without moving parts, and it also possesses the additional advantage of reducing the back press- ure on the piston. Unfortunately these advantages are obtained only at certain loads, and with certain velocities of the exhaust gases, which makes it impossible to obtain even approximately correct scavenging at other loads and speeds. When air pumps are used for scavenging, a great percentage of the economy obtained is offset by the power required to operate the pumps. In addition to the frictional losses of the pumps, are the increased maintenance charges and repair bills. CHAPTER III FUELS AND COMBUSTION (7) Combustion. The phenomenon called combustion by which we obtain the heat energy necessary for the operation of the internal combus- tion engine is a chemical combination of th^ air with the fuel. This process results in heat and some light which is equal in quantity to the energy required to separate the fuel compound into its elements or to build it up in its present form from the original elements. If the process is comparatively slow, the compound is called a fuel, if it is instantaneous it is called an explosive. Some substances produce mechanical force through an instant, without the evolution of much heat, due to the dis- integration of an unstable compound. The effect of the latter type of which dynamite is an example is static, that is to say, it is not capable of producing power, but only pressure. For this reason, compounds having an instantaneous effect without the ability to produce the pressure through a distance, or an expansion, are not considered as suitable fuels for a heat engine. A fuel is essentially a substance which is capable of generat- ing heat, which is a form of energy, and not static pressure. The heat engine is instrument which transforms this energy into power which is again dissipated into heat through the friction of the engine itself and by the load that it drives. This is an illustration of the physical law that "energy can neither be created nor destroyed," th'at is, the heat energy developed by the fuel is converted into mechanical energy which is again transformed into heat energy through friction. It should be understood that fuel belongs to that class of substances that will not burn nor evolve energy under any temperature, pressure, or shock, without an outside supply of oxygen. This is the characteristic property of all fuels used with the infernal combustion engine. Each element, such as carbon and hydrogen, in a compound fuel, develops a certain definite amount of heat during their complete combustion, and at the close of the process certain compounds are formed that 41 42 FUELS represent the lowest chemical form of the compound. To re- store the products of combustion to their original form as fuel would require an expenditure of energy equal to that given out in the combustion. While all substances that are capable of oxydization or com- bustion can be made to liberate heat energy, it does not follow that all of them can be successfully used as fuels. A fuel suit- able for the production of power must be cheap, accessible and of small bulk, and must burn rapidly. Such fuels must also be products of nature that require no expenditure of energy in their preparation or completion. Fig. F-4. Fairbanks-Morse Producer Plant and Engine, Connected for Operation. In practical work, the natural fuels are coal, mineral oils, natural gas, and wood, which are compounds of the elements carbon and hydrogen. When these fuels are burned to their lowest forms the products of combustion consist of carbon dioxide and water, the first being the result of the oxydization of carbon, and the latter a compound of oxygen and hydrogen. In solid fuels, such as coal, a portion of the compound consists of free carbon and the remainder of a compound of carbon and hydrogen known as a HYDROCARBON. In liquid fuels there is little, if any, free carbon, the greater proportion being in the FUELS 43 form of a hydrocarbon compound. Natural gas is a hydrocarbon compound. It should be noted that a definite amount of oxygen is re- quired for the complete combustion of the fuel elements, and that a smaller amount of oxygen than that called for by the fuel element results in- incomplete combustion, which produces a product of higher form than that produced by the complete reduction. The product of incomplete combustion represents a smaller evolution of heat than that of the complete process, but if reburned in a fresh supply of oxygen the sum of the second combustion together with that of the first will equal the heat of the complete oxydization. When pure carbon is uncom- pletely burned the product is carbon monoxide (CO) instead of carbon dioxide (CO 2 ). Carbon completely burned to carbon dioxide produces 14,500 British thermal units per pound of carbon, while .the incom- plete combustion to carbon monoxide evolves only 4,452 British thermal units, or less than one-third of the heat produced by the complete combustion. Theoretically one pound of car- bon requires 2.66 pounds of oxygen to burn it to carbon dioxide. On supplying additional oxygen, the carbon monoxide may be burned to carbon dioxide and the remainder of the heat may be recovered, or 10,048 British thermal units. When a hydro- carbon, either solid, liquid or gaseous is burned with insufficient oxygen, solid carbon is precipitated together with lower hydro- carbons, and tar. In an internal combustion engine the pre- cipitated solid carbon is evident in the form of smoke. Since the carbon and hydrogen elements of a fuel exist in many different proportions and conditions in coal and oil, differ- ent amounts of oxygen are required for the consumption of dif- ferent fuels. It should also be borne in mind that a greater quantity of air is required for the combustion of a fuel than oxygen, as the air is greatly diluted by an inert gas, nitrogen, which will not support combustion. Because of the impos- sibility of obtaining perfectly homogenous mixtures of air and the fuel, a greater quantity of air is used in practice than is theoretically required. In a steam engine the fuel can be used in any form, solid, liquid, or gaseous, but in an internal combustion it must be in the form of a gas no matter what may have been the form of the primary fuel. Fortunately there is no fuel which may not be transformed into a gas by some process if not already in a gaseous state, The petroleum products are vaporized by 44 FUELS either the heat of the atmosphere or by spraying them on a hot surface. Coal is converted into a gas by distilling it in a retort or by incomplete combustion. The heat energy developed by a gas when burning in the open air depends on its chemical combustion, but its mechanical equivalent in power when burned in the cylinder of the engine depends not only upon its composition but upon the conditions under which it is burned as stated in the chapter devoted to the subject of heat engines. (8) Gaseous Fuels. While the calorific values of the different gases given in the accompanying table are approximately correct for gases burning in the open air at atmospheric pressure they develop widely different values in the cylinder of an engine because of the effects of compression and preheating. The table serves, however, as an index to the relative values of the fuels under ordinary conditions without compression. While natural gas has nearly eight times the calorific value of producer gas in the open air, its actual heat value in the cylinder is only about 45 per cent greater. While acetylene has an exceedingly high calorific value and explodes five times as fast as gasoline gas, it develops only 20 per cent more power in the same cylinder. Another item affecting the value of a gas is the rate at which it burns, which is in part a characteristic of the fuel and partly a factor of the conditions under which it is burnt. This sub- ject is treated of in the chapter devoted to the heat engine. The calorific value of a gas may either be computed from its chemical composition or by burning it in an instrument known as a calorimeter. A gas calorimeter consists of a small boiler or heating tank which is carefully covered with some non- conducting material so as to prevent a loss of heat to the at- mosphere. The gas under test is burned in the boiler whose extended surface catches as much of the heat as possible and transfers it to the water in the boiler. The weight of the water heated and its temperature are taken when a certain amount of the gas has been burned (say 100 cubic feet), and from this data, the heat units per cubic foot of gas are com- puted. As a British thermal unit is the amount of heat required to raise the temperature of one pound of water through one Fahrenheit degree (at about 39.1 F.), the total heat per cubic foot of gas as observed by the calorimeter is equal to the weight FUELS 45 3AU03JJ3 8800 >n 88^18 ot^oooo t^ t^oooo"oc? 1 J3MOJ 8 8 the gas, z sqq '300^ DiqiO jad iqSpAV ! ?f f ^_ 1 bjD 'o 3 d 8OOOO O o^^Oio OOLO"") \O irjCSM-^- C V uoijsuquiof) jo o? 1 ^2 3 J3 rt 1* ui -bg jad - sqn[ ui aanssajj uoisojdxg ss^ if;;vi- i If 5 a 4ty oj SBQ JO OlJIZy ~\OOVM 00 MCp'OOO but also ^ ic gases sasvfl bg jad 'sq^ M ;^ , ^ > engine used ve value of t PUEL 'S 1- C * 4) in m m ^ o\ .j !2 t only with the >ea of the relat ii i o jj vS 8 v iN'oS>S8"rt' en O.s B c >.I c jooj oiqn^ 2 8 S 3 OOOOOQ-*QOOO O Sin-^-^OOOoOiNNis N I 1 M v 2 ^~* ' ' ' ' ' ' ii O 11 I H i a i | c.-ti:iu cirtrt*^ values give icter of the I I 1 1 1 | 1 I 1 1 1 1 1 1 1 (jC^^?PQ^OOOU!U i < Tlie dhe char 46 FUELS of the water multiplied by its use in temperature in degrees, divided by the number of cubic feet of gas burned in the calori- meter. Since a British thermal unit is equal to 778 foot pounds in mechanical energy, its mechanical equivalent is equal to the number of British thermal units multiplied by 778. Another difference between the actual and theoretical results obtained is that due the perfect combustion in the calorimeter and the imperfect combustion in the engine. Since some gases require more air for their combustion than others, less of the first gas will be taken into the cylinder on a charge than the latter, which tends still further to balance the heating effect of rich and lean gases in the cylinder. (9) Gasifying Coal. Coal Gas or Illuminating Gas is generated by baking the coal in a closed retort or chamber out of contact with the air so that no combustion takes place either complete or incomplete. The hydrocarbon gases and tars are set free from the coal as permanent gases and are then piped to a gas holder after going through various purifying processes to remove the tars, oils, moisture and dust. The free or solid part of the coal remains in the retort in the form of coke, which is again burned for fuel. Because of its high carbon content, coal gas burns with a yellowish-white flame and is extensively used for lighting pur- poses, hence the name illuminating gas. In many ways coal gas is an ideal fuel for power purposes as it has a high calorific value (650-750 B.T.U. per cubic ft.), is supplied by the illumi- nating company at practically a constant pressure, and is uni- form in quality. Its only drawback is its comparatively high cost. This gas is always obtained from the city service mains as its preparation is too expensive and complicated for the gas en- gine owner. Because of its cost, the use of coal gas is restricted to small engines. (10) Water Gas. Water gas is made by blowing air through a thick bed of some coal that is low in hydrocarbons until the coal becomes incandescent, the gases that are formed are allowed to escape to the atmosphere. At this point a jet of steam is blown into the incandescent bed, which is broken up into its elements, oxy- gen and hydrogen, by the heat of the fuel, As there is no FUELS 47 air present the oxygen combines with the carbon of the fuel to form carbon monoxide while the hydrogen goes free. Both of these gases, carbon monoxide and hydrogen, are collected and supplied to the engine. The production of water gas is intermittent, as the steam blast cools down the fuel bed, and requires further blowing before more steam can be passed. While this gas has a lower heating value than coal gas, it is much cheaper to make and all of the coal is consumed in the process. Water gas is high in hydrogen and is too "snappy" for gas engines; the hydrogen places a limit on the allowable com- pression. For each thousand feet of water gas generated, approximately 24 pounds of water are required. By the introduction of hydrocarbons or vaporized oil, illumi- nating value is given to water gas, this process is called car- buretion. Carbureted gas is not usually used for power, as it is expensive, and is not proportionately high in heating value. (11) Blast Furnace Gas. Many steel companies are utilizing the unconsumed gas of the blast furnaces for power. Blast furnace gas is of very low calorific value, rarely if ever, exceeding 85 B.T.U. per cubic foot. This allows of very high compression, which greatly increases the actual power delivered by the engine. A smelter produces approximately 88,000 cubic feet of gas per ton of iron smelted. Blast furnace gas is so lean that it cannot be burned satis-. factorily under a boiler; the high compression of the gas en- gine makes its use possible. (12) Producer Gas. Producer gas which is generated by the incomplete combus- tion of fuels in a deep bed is the most commonly used gas for engines having a capacity of 50 horsepower and over, because of the simplicity and economy of its production. While pro- ducer gas has been obtained from practically every solid fuel, of which coal, coke, wood, lignite, peat, and charcoal are ex- amples, the fuel most generally used is either coal or coke. While producer gas is much lower in calorific value than either natural or illuminating gas it gives admirable results in the gas engine and is a much cheaper fuel than coal gas in units above 48 FUELS 50 horse-power capacity. The fuel is completely burned to ash in the producer without the intermediate coke product that exists in the manufacture of coke. A producer consists of three independent elements as shown by Fig. F-6; the PRODUCER or generator (A), the steam boiler (B), and the SCRUBBER or purifier (C). The incandescent fuel (F) in the form of a cone lies on the grate bars (G) at the lower end of the producer. Above the burning fuel is a deep bed of coal (D) which reaches to the top of the producer at which point it is admitted to the bed through the charging valve or gate (H). The gas resulting from the combustion in the producer is drawn out of the tank through the gas out- let pipe (E) by the suction of the engine. The air for the combustion is drawn up through an opening in the ash pit (J) by the engine. When the oxygen of the air strikes the incandescent fuel on the grate it combines with a portion of it forming carbon dioxide (CO 2 ) which is an incombustible gas, but on passing through the burning fuel above this point, one atom of the oxygen in the CO 2 recombines with the fuel forming the com- bustible gas carbon monoxide (CO). Because of the dis- tilling effect of the heat in the bed, the volatile hydrocarbons of the coal are set free and mingle with the CO formed by the combustion. The producer gas consists, therefore, prin- cipally of CO, with a certain proportion of the volatile hydro- carbons of the coal such as marsh gas, ethylene, and some oil vapor. Since the hydrocarbons are easily condensed on coming into contact with the coal walls of the piping, to form trouble mak- ing tars and oils, they must either be washed out of the gas in the purifier or passed again through the high temperature zone to convert them into permanent gases. In the usual pro- ducer, the hydrocarbons are reheated, as they form a consider- able percentage of the heat value of the gas. After the volatile constituents are reheated, the gases pass through the boiler (B), which absorbs the heat of the gas in generating steam, and from this point the gases enter the scrubber where the dust and the residual tars are removed. The scrubber, which is a sort of filter, is an important factor in the generating plant, for if the dust and dirt were allowed to pass into the cylinder of the engine it would only be a question of a short time until the valves and cylinder would be ground to pieces. When the steam from the boiler is allowed to flow into the FUELS 49 ash pit of the producer and up through the incandescent fuel, the heat separates the water vapor into its two elements, oxy- gen and hydrogen. The oxygen set free combines with the carbon in the coal forming more carbon monoxide, while the hydrogen which is unaffected by the combustion adds to the heat value of the gas. The last additions to the combustion dut to the disassociation of the steam are really what is known as "water gas." A limited amount of steam may be admitted H- Fig. F-6. Diagram of Suction Gas Producer Showing the Generator, Boiler and Washer. continuously in this manner without lowering the temperature of the fuel below the gasifying point, and its presence is bene- ficial for it not only provides more CO and hydrogen but pro- duces it without introducing atmospheric nitrogen. The steam is also a great aid in preventing the formation of clinkers on the grate bars. Since the air used in burning the fuel in the first reaction contains about 79 per cent of nitrogen, which^is an inert gas, the producer gas is greatly diluted by this unavoid- able admixture, which accounts for its low calorific value. While the air required for the combustion of the fuel is drawn through the producer by the suction of the engine in the example shown (SUCTION PRODUCER), there is a tvoe 50 FUELS in common use called a PRESSURE PRODUCER in which the air is supplied under pressure to the ash pit by a small blower, which causes a continuous flow of gas above atmospheric pressure. Gas producers are divided into two classes: suction producers and pressure producers. The suction producer presents the following advantages: 1. The pipe line is always less than atmospheric pressure, hence no leaks of gas to the air are possible. 2. The regulation of the gas supply is automatic. 3. No gas storage tank is required. 4. The production of gas begins and stops with the engine. 5. Uniform quality of gas. The suction producer is limited to power application and cannot be used where the gas is to be used for heating, as in furnaces, ovens, etc., or where the engine is at a distance from the producer, unless pumped to its destination. The pressure producer does not yield a uniform quality of gas, hence requires a storage tank where low quality gas will blend with gas of higher calorific values and produce a gas of fairly uniform quality. The pressure producer is adapted to the use of all grades of fuels, such as bituminous coal and lignite. Anthracite coal contains little volatile matter and is an ideal fuel for the manufacture of producer gas, while bituminous coal with its high percentage of volatile matter and tar, requires more efficient scrubbing, as these substances must be removed from the gas. On starting the producer shown by Fig. 6, the producer is filled with the proper amount of kindling and coal, and a blast of air is sent into the ash pit by a small blower, the products of combustion being sent through the by-pass stack (K) until the escaping gas becomes of the quality required for the operation of the engine. The by-pass valve is now closed, and the gas is forced through the scrubber to the engine until the entire system is filled with gas. When good gas appears at the engine test cock the engine is started, and the blower stopped, the gas now being circulated by the engine piston. The volume of gas generated by the producer is always equal to that required by the engine so that no gas receiver or reservoir is required. Because of the friction of the gas in passing through the fuel, scrubber and piping its pressure at the engine is always considerably below that of the atmosphere, FUELS' 51 which of course reduces the amount of charge taken into the cylinder. Because of the weak gas and the low pressure in the piping, it is necessary to carry a much higher compression with producer gas than with natural or illuminating gas. The efficiency of a producer is from 75 to 85 per cent, that is, the producer will furnish gas that has a calorific value of an average of 80 per cent of the calorific value of the fuel from which it is made, the remaining 15 to 20 per cent being con- sumed in performing the combustion. This is far above the efficiency of the furnace in a steam boiler, as an almost theo- retically exact amount of air can be supplied in the producer to effect the combustion, while in the boiler furnace about ten times the theoretical amount is passed through the fuel bed to burn it. Heating up this enormous volume of air to the temperature of the products of combustion consumes a large amount of fuel and reduces the efficiency of the furnace con- siderably. Because of the reduction in the air supply, a gas fired furnace is always more efficient than one fired with coal. Producer gas with 300,000 British thermal units per thousand cubic feet, and oil having 130,000 British thermal units per gal- lon will result in 1,000 cubic feet of gas being equal to about 2.20 gallons of fuel oil. If the gas is to be used for heating ovens or furnaces in con- nection with the generation of power, the character of the fuel will be determined to a great extent by the requirements of the ovens and by the type of producer used, as each fuel will give the gas certain properties. Thus gas used for firing crockery will not be suitable for use in open hearth steel furnaces, as the impurities in the various fuels may have an injurious effect on the manufactured product. The cost of the fuel, cost of trans- portation, heat value, purity, and ease of handling are all factors in the selection of a fuel. The size and condition of a fuel is also of importance. Ex- ceedingly large lumps and fine dust are both objectionable. Wet fuel reduces the efficiency of the producer, as the water must be evaporated, this causing a serious heat loss. With careful attention a producer gas engine will develop a horse-power hour on from 1 to 1J4 pounds of anthracite pea coal, and in many instances the consumption has been less than this figure. The efficiency in dropping from full load to half load varies by little, one test showing a consumption of 1.1 pounds of coal per horse-power hour at full load and 1.6 pounds of coal at half load. Producer gas power is nearly as 52 FUELS cheap as water power, in fact the producer gas engine has dis- placed at least two water plants to the writer's knowledge. According to an estimate made by a well known authority, Mr. Bingham, it is possible for a producer gas engine to gen- erate power for only .1 of one cent more per K.W. hour than it is generated at Niagara Falls. According to the United States Bureau of Mines, "The tests in the gas producer have shown that many fuels of so low grade as to be practically valueless for steaming pur- poses, such as slack coal, bone coal and lignite, may be econom- ically converted into producer gas and may thus generate suffi- cient power to render them of high commercial value. "It is estimated that on an average each coal tested in the producer-gas plant developed two and one-half times the power that it would develop in the ordinary steam-boiler plant. "It was found that the low-grade lignite of North Dakota developed as much power when converted into producer gas as did the best West Virginia bituminous coals burned under the steam boiler. "Investigations into the waste of coal in mining have shown that it probably aggregates 250,000,000 to 300,000,000 tons yearly, of which at least one-half might be saved. It has been dem- onstrated that the low-grade coals, high in sulphur and ash, now left underground, can be used economically in the gas pro- ducer for the ultimate production of power, heat and light, and should, therefore, be mined at the same time as the high- grade coal. , "As a smoke preventer, the gas producer is one of the most efficient devices on the market, and furthermore, it reduces the fuel consumption not 10 to 15 per cent, as claimed for the ordinary smoke preventing device offered for use in steam plants, but 50 to 60 per cent. (13) Producer Gas From Peat. The production of gas from peat having a low water content (up to about 20 per cent) for use in suction gas engines has already met with considerable success in Germany, but for a number of years efforts have been made to utilize peat with a water content as high as 50 to 60 per cent and thus eliminate the costly process of drying the raw material. Difficulties have been encountered in preventing a loss of heat through radiation and other causes, and in getting rid of the dust and tar vapors carried over by the gases to the FUELS 53 engine; but great strides have been made recently in over- coming these obstacles. Peat with a water content up to 60 per cent has been found to be a suitable fuel. Owing to its great porosity and low specific gravity it presents a large com- bustion surface in the generator, so that the oxygen in the air used as a draft can easily unite with the carbon of the peat. One of the great difficulties is to eliminate the tar vapors that clog up many of the working parts of the engine. The passing of the gas through the wet coke washers and dry. saw- Fig. F-7. German Producer for Generating Producer Gas from Peat. dust cleansers does not appear to have thoroughly remedied the evil. Efforts were therefore made to remove the tar-form- ing particles of the gas in the generator itself or to render them harmless. That of the Aktien-Gesellschaft Gorlitzer Masch- inenbau Ansalt und Eissengiesserei of Gorlitz, was displayed at the exposition at Posen in 1911. The gas from the generating plant was employed in a gas suction engine of 300 horse-power used to drive a dynamo for developing the electric energy for the exposition. The fuel used was peat with a water content of about 40 per cent. The efficiency and economy results obtained were very promising. 54 . FUELS The advantages claimed for the Gorlitz engine are that the sulphurous gases and those containing great quantities of tar products are drawn down by the suction of the engine through burning masses of peat and thus rid of their deleterious con- stituents. The air for the combustion purposes is well heated before entering the combustion chamber, thereby producing economical results. It is claimed also that the gas produced by its system is so free from impurities that the cleaning and drying apparatus may be of the simplest kind. In Stahl und Eisen, an abstract is given of a paper by Carl Heinz describing a peat gas producer, built by the Goerlitzer Maschinenbauanstalt. We are indebted to Metallurgical and Chemical Engineering for the translation of this paper: Air and fuel enter the producer at the top, and the gas exit is in the center of the bottom so that the air is forced to pass through the center of the producer, decomposing the volatile matter into gases of calorific value. The moisture which is present in the peat fuel in considerable quantities must be taken into consideration. For its decomposition which passing through the hot-fire, zone only a certain amount of heat is available. It is, therefore, important that the heat from the gasification be fully utilized. There are two kinds of heat losses in a gas producer, due to radiation and to the sensible heat of escaping gases. Both these amounts of heat, however, are utilized according to the special design of this producer. The air circulates first through the lower conduit and comes so in contact with the warm scrubber water. A part of the air which has been preheated is carried upwards through the pipe A in the center of the producer where it is thoroughly preheated by the hot gases and enters then the air superheater B in which the temperature rises to a still higher degree. The other part of the air passes through the feet of the producer into an air jacket which envelops the whole shell of the producer and enters finally the producer by the reversing valve C on top of the producer. In this way the outer surface of the producer is maintained at a temperature hardly higher than that of the surrounding air. The escaping gases are cooled down so far that the gas outlet into the scrubber may be touched by hand. All ordinary heat losses are thus made use of in the gasification process. If there is a large excess of moisture in peat, the process is somewhat modified by regulating both air supplies in such a FUELS 55 way that the gasification in the upper part of the fuel-bed takes place in two directions, one downwards and the other upwards. It seems that a content of 80 per cent moisture and 20 per cent dry fuel in the peat is about the limit permitting evapora- tion of the water, but it is, of course, impossible to obtain in this case a gas of calorific value. The modification of the process for very wet fuel is as follows: When the fire on top of the fuel bed appears to disappear, the heater opens the stack and valve D. Valve C is then closed, to prevent air from entering on top. The preheated air en- ters by D causing a down draft combustion due to the suction of the gas engine and an upward combustion due to the draft in the stack. The moisture is evaporated and escapes through the stack. When the fire has burned through at the top, the valve is switched over. The bad smelling gases rising from the scrubber enter the producer together with air and are there consumed. In commercial use at the exhibition in Posen the whole plant worked continuously day and night and cleaning of the gas en- gines was necessary only every three months. Slagging of ashes is done during the operation of the producer, without any nuisance from dust. The highest percentage of moisture in peat gasified was 50 per cent. The fuel consumption per horse-power hour is 2.2 Ib. (1 kg.) of peat. Careful tests made by Prof. Baer, of Breslau, showed that with a cost of peat of $1 per ton the kw-hour at the switchboard costs 0.15 cent. (14) Crude Oil Producers. The development of the crude oil gas producer, for which there is great demand, in oil regions remote from the coal field, has been exceedingly slow but it is believed that definite progress has recently been made along this line. The most recent notes on this subject relate to the Grine oil producer. In this type steam spray is used for atomizing the oil which is introduced into the upper part of the generator where partial combustion takes place. The downdraft principle is then ap- plied and the hydrocarbon broken up and the tar fixed by passing through a bed of incandescent coke. Mr. Grine reports that a power plant using one of these producers has been in operation a year in California. With crude oil as a fuel costing 56 FUELS 95 cents per barrel, or 2.3 cents per gallon, the plant is reported to develop the same amount of power per gallon of crude as is ordinarily developed by the standard internal combustion en- gine operating on distillates at 7 cents per gallon. Including the cost of fuel, labor, supplies, interest, depreciation and taxes, Mr. Grine states the cost per b.h.p. hour to be 0.76 cents for a plant of 100 h.p. rating. (15) Operation of Producers. A good producer operator is simply a good fireman, he must know how to keep a uniform bed of coal and how to draw the fire. While there are many thousands of men running pro- ducer plants without previous mechanical training, there are now but few steam engineers running steam engines of the same capacity but what have had at least two years' training and suffi- cient mechanical knowledge to pass an examination and obtain a license. While a considerable amount of skill is necessary to obtain the best efficiency from a producer, it is a knack that is easily acquired in a short time by "sticking around" the plant. Skill in operating a producer consists chiefly in keeping the right sort of a fire without damage to the lining by poking down ashes and clinkers. When a new plant is installed, the manufacturer generally sends an instructor to operate the plant for a short time so that with a few days running in his hands any man with ordinary intelligence can overcome the difficulties which arise from time to time. While there are many types of producers, the main difference will be found in the character of the draft, that is whether it is up, down, or crossways. Down draft producers are generally used with bituminous coals, as the tars and oils that emanate from the coal are drawn through the fire which converts them into a permanent gas, and avoids the difficulty of removing great quantities of the tar from the producer. An up draft producer will not do this as the gas is drawn directly into the mains without coming into contact with the fire. This would result in considerable expense due to the, frequent cleaning. Anthracite coal which does not contain much tar can be used successfully in an up draft producer. A compromise between the up draft and down draft producer is had in the DOUBLE ZONE producer, which "burns the candle at both ends" as it were, a fire being at both the top and bottom of the producer. Nearly any class of fuel may be used with this type. FUELS 57 It should be remembered that a hot fire and fuel are required for the manufacture of gas, and that the ash pit and grate must be kept clear of the ashes and clinkers that not only reduce the temperature of the fire, but also reduce the gas available at the cylinder by increasing the friction. Shaking down and cleaning out will in 'nearly every instance start a bucking pro- ducer into operation. When operating under full load a much hotter fire is re- quired than when operating under a reduced load, or the pro- ducer will not furnish the necessary gas. According to the size of the producer, the depth of the incandescent fuel will run from 30 inches in the large sizes to 15 inches in the smaller. After being charged up, suction producers will con- tinue to give gas in sufficient quantities with the bed at half this depth. This is only possible with a hot producer, and when no fuel is being fed, as the feeding of a cold charge will reduce the output. A steady depth of fire should be kept to maintain a uniform quality of gas. In suction producers careful watch should be kept for leaks, as the gas being below atmospheric pressure gives no outward signs of dilution. If water seals are used in the system they should be given careful attention. When using coals that are rich in tar or hydrocarbons, or with fuels that have much fine dust, considerable trouble is had with some types of pro- ducers due to "caking" or to the adhesion of the coal particles to the walls of the producers or to their adhesion to one another. In the latter case the "stickiness" of the fuel prevent the proper feed. This difficulty may often be overcome by a change in the rate of feeding or by regulating the depth of the incandescent bed. Porosity of the fuel, and the rate at which the air is sup- plied to the producer determines the depth of the incandescent bed. Particular care should be taken that the blast or draft occurs evenly over the fire surface, and that no holes occur in the fire which will cause more rapid combustion in one spot than in another. Neglect of this precaution not only causes a waste of fuel but often results in the fuel "arching" and preventing further feed. The producer should be so pro- portioned that at full load, the rate of combustion does not exceed 24 pounds of fuel per square foot of producer area per hour. In his researches, Professor Bone (Iron and Steel Institute, May, 1907) has shown that up to 0.32 Ibs. of steam per Ib. of 58 FUELS coal can be completely decomposed in a producer, but that, from 0.45 Ibs. to 0.55 Ibs. should be used, approximately 80% more. Now, in considering the question of the proper proportion of steam for the production of gas for power purposes we must bear in mind that as much heat as possible should be utilized in the producer itself. Some manufacturers of plant go so far as to state that as much as 1 Ib. of steam per Ib. of coal should be used, but we are safe in saying that 0.5 Ib. to 0.7 Ib. should be the figure for a power plant. The common practice is to use a blast saturation of 55% whenever the clinkering char- acter of the coal renders it possible. This figure corresponds to about .57 of steam per Ib. of coal gasified. It is of the utmost importance that the proportion of steam and air should be constant, and the best figure being de- termined, it should not be varied to any degree. It is equally important that the fuel depth should be left constant. By this I mean that not only should the coal in the producer be kept at a specific level, but the position of the fire on the ash bed should be kept as near as possible a fixed point. Ashes should be drawn at regular intervals, or, if desired, continuously by mechanical means. Further, the supply of air and steam should be regularly distributed, so that the velocity of the gases through the fuel shall be as nearly as possible regular across its whole area. In some cases the by-products of a producer, such as am- monia, tar, etc., have a commercial value, and if a large amount of gas is generated it will sometimes pay to select a fuel that is rich in these particular substances. (16) Coal. Coal which is the basis of producer gas, is composed gen- erally speaking of the combustible matter, moisture, ash and sulphur. The combustible element may be subdivided into the HYDROCARBONS, OR VOLATILES, and the solid fixed car- bon. The exact composition of coal is generally given by what is known as PROXIMATE analysis, which analysis divides the constituents of the coal into five groups, viz.: MOISTURE, VOLATILES, FIXED CARBON, ASH, and SULPHUR. Ultimate analysis resolves the coal into its ultimate chemical elements, such as hydrogen, carbon, nitrogen, sulphur, etc., and being a difficult and tedious process it is not much used. FUELS 59 The proximate analysis gives all the necessary information and takes less time to perform. The CALORIFIC VALUE of a fuel may be calculated from its analysis, or may be determined by means of the CALORI- VALUES OF COAL Location of Mine PROXIMATE ANALYSIS Calorific Value in B. T. U. per Lb. of Coal Moisture Volatile Matter Fixed Carbon Ash Sulphur ANTHRACITE Moitliern Pa. 3-39 4.41 83-30 8.17 73 13,200 Eastern Pa. }37 3-7 86.42 6.18 63 13.440 Western Pa. 3-12 3-76 81.60 10.61 53 12,875 SEMI- ANTHRACITE 1.25 8.15 83-30 627 1.63 13,900 SEMI- BITUMINOUS Pennsylvania .80 15.60 77.40 5-35 85 14.900 Pennsylvania i-55 i6-45 71-50 8.63 1.87 14,200 Pocahontai Va. 1. 00 21.00 24.40 3-02 -58 15,100 West Virginia .9 17-83 77.70 3-30 .27 15.230 BITUMINOUS Youghiogheny Pa. I.OO 3 6 -5o 59.00 2 -59 .86 14.400 Sample No. 2 " 1.2O 30.18 59.00 8.84 .78 14,000 Hocking Valley 6-5 35-o6 48.80 8.05 i-59 12.100 Kentucky 4.00 34-0 54-70 7.00 03 I2,800 Indiana 8.00 30.20 54 20 7.60 I2,5OO Illinois 10.50 36 15 37.00 12.90 3-45 10,500 Colorado 6.00 38.01 47.90 8.09 12,200 LIGNITE 9.00 42 26 44-30 3-27 1.18 11,000 60 FUELS METER from a sample of the coal; the latter method is the most reliable. Table gives approximately the calorific values, and the proximate analysis of several representative coals from various sections of the country. The values given in the table are not exact, as the coal from each locality varies considerably in quality, but the figures will indicate what may be expected from .each type of coal. Connellsville, Pa., Coke has a calorific value of approximately 13,000 B.T.U.S. per pound, contains no volatile matter, and has an approximate content of 10% ash. Coke is a valuable fuel for the gas producer, but is rather expensive. It is clean and the absence of volatile matter reduces the "scrubbing" problem to a minimum. Small coal such as buckwheat and pea contain a much higher percentage of moisture than given in the table, running from 5% to 10% higher than the given values. Bituminous coal is high in hydrocarbons or volatiles which condense easily and form tar. If the tar is not removed or converted into a permanent gas, it will clog the passages of the producer and the engine and cause trouble. The removal of the tar and ash from a gas is called SCRUB- BING, and is performed by a device much resembling a filter. Anthracite coal and coke are low in volatiles or hydrocarbons, and therefore do not cause trouble with tar deposits. A high percentage of volatile matter also causes trouble by the tar cementing the particles of fuel together. This inter- feres with the proper action of the producer. Fuels having a high percentage of ash call for perfect filter- ing or "scrubbing" as such fuels will fill the gas passages with dust Dust should be kept out of the engine at all costs, for the dust even in a quantity will cause wear in the cylinder. Depending on the quality of the fuel, bituminous coal will produce about 4*/2 pounds of ammonia and 12 gallons of tar with about 5% of sulphur. Anthracite coal will produce approximately six pounds of tar, and two pounds of ammonia with traces of sulphur. Loose Anthracite coal requires approximately 40 cubic feet of storage space per ton of 2240 pounds and weighs about 56 pounds per cubic foot (market sizes). Loose Bituminous coal requires approximately 45 cubic feet of storage space per ton of 2240 pounds, and weighs about 52 pounds per cubic foot in market sizes. Dry coke requires approximately 85 cubic feet of storage FUELS 61 space per ton of 2240 pounds, and weighs about 26 pounds per cubic foot. (17) Fuel Oils. Crude oil, a natural product, is the base of the fuels most commonly used in internal combustion engines, especially in the smaller sizes. From this compound the following deriva- tives are obtained by the process of distillation, a separation possible because of the different boiling points of the various oils. As each derivative or DISTILLATE has a different boiling point, the temperature of the crude oil is maintained at the boiling point of that product that is desired, and the resulting vapor is condensed. The following list is not anywhere near complete for there are several hundred distinctly different dis- tillates, but it contains those that are of the most interest to the engine man. 1. Crude Oil. 2. Gasoline. 3. Naptha. 4. Solar Oil. 5. Kerosene. The specific gravity of the crude oil as obtained in the field will range from 12 to 56 Beaume scale. The crude from Pennsylvania will average 40 Beaume while that from Texas will average 20 ? . The accompanying table will give the calo- rific values and general properties of the principle liquid fuels. It should be noted that the weight or density of the liquids is given in terms of specific gravity or Beaume scale, in which the SPECIFIC GRAVITY of the fuel is the ratio of its weight per unit volume to the weight of an equivalent volume of water. The specific gravity of a liquid is generally determined by an in- strument known as a HYDROMETER which consists of a glass tube sealed at both ends carrying a graduated scale on the upper portion of the stem, and a ballast weight of shot or mercury at the bottom. The hydrometer is floated in the liquid to be tested, and the lower the specific gravity, the lower the hydrometer sinks, and vice versa. The specific gravity of the liquid is read directly from the graduation on the stem that are on a level with the .surface of the liquid under test. As in the case of thermometers, hydrometers are all graduated in two different scales, the specific gravity scale and the Beaume scale. The spe- 62 FUELS cific gravity scale reads at 1.00 when floated on distilled water, and the Beaume at 10.00 when floated on the same liquid. A difference in temperature affects the density of a liquid, hence all hydrometers are graduated for a standard temperature of 60F unless otherwise specified. For a difference of 10F there is a variation of one degree gravity in the Beaume scale, and for a difference of 20F in temperature there is a change of one degree on the specific gravity scale. If the temperature differs from 60F, the corresponding correction should be made in the reading. To convert the Beaume reading (B) to terms of the specific gravity scale (S) use the following formula: 140 S = = specific gravity. 130 + B 140 B = Beaume scale. S Properties of Oils Degrees Specific Weight B. T. U.'S B. T. U.'S Baume Gasoline 67.2 Heavy naphtha 64.6 Kerosene 48.8 W. Virginia crude 40.0 Penn. fuel oil 31.9 Kansas crude 29.0 Fuel oil 22.7 California crude 22.5 California crude 15.2 Alcohol, 95% 41.9 It will be noted that the petroleum products contain an enor- mous amount of heat energy, nearly 25% more than that of the same weight of pure carbon. It will also be noted that the lighter products such as gasoline, kerosene, etc., have more heat per pound but less per gallon than the heavier oils. This is rather confusing at first, but as will be seen after deliberation that the heavier fuel is the most economical since the least is used per horse-power, and is bought by the gallon. The calorific values given in the table are obtained by a colorimeter, and are burnt in the open air, and consequently have a different heating value when under compression in the cylinder of the engine. Gravity .7125 .7216 .7848 .8251 .8660 .8816 .9176 .9248 .9646 .816 per gal. 5.932 6.011 6.538 6.874 7.215 7.345 7.645 7.710 8.036 6.798 per Ib. 21120 20527 20018 19766 19656 19435 19103 18779 18589 10500 per gal. 125,284 123,388 130,877 135,871 141,818 142,750 146,042 144,786 149,381 71,380 FUELS 63 In all cases the liquids are vaporized before being introduced in the cylinder, the more volatile liquids such as gasoline being converted into vapor at atmospheric temperature, and the heavier non-volatiles by being sprayed into a heated vessel or preheated air. The percentage of liquid fuel contained in a cubic foot of air vapor mixture depends on the temperature, the boil- ing point of the liquid and upon the pressure and humidity. Gasoline consists principally of compounds of the methane series, the one representative of gasoline being Hexane (C 6 Hi 4 ). It requires 15.5 pounds of air for combustion theoretically and about 10 per cent more in practice. The formation of gasoline vapor produces a drop in temperature of 50F, and should be heated 100F above the atmosphere for the best results. The volume of air required for the combustion is about 192 cubic feet. With alcohol at 20 cents per gallon and gasoline at \2 l / 2 cents the number of B.T.U.'s for one cent in the case of alcohol is 3594 and 9265 in the case of gasoline. In the engine the difference is not so great owing to the difference in compression pressures. (18) Tar for Fuel. Because of the increasing interest in the Diesel type engine and the low grade fuels that it has made possible, we quote the specifications laid down by Dr. Rudolph Diesel, the in- ventor, before the English Institution of Engineers. (1.) Tar-oils should not contain more than a trace of consti- tuents insoluble in xylol. The test on this is performed as follows: 25 grammes (0.88 oz. av.) of oil are mixed with 25 cm. 3 (1.525 cub. in.) of xylol, shaken and filtered. The filter- paper before being used is dried and weighed, and after filtra- tion has taken place it is thoroughly washed with hot xylol. After re-drying the weight should not be increased by more than 0.1 gr. (2.) The water contents should not exceed 1 per cent. -The testing of the water contents is made by the well-known xylol method. (3.) The residue of the coke should not exceed 3 per cent. (4.) When performing the boiling analysis, at least 60 per cent by volume of the oil should be distilled on heating up ta 300 C. The boiling and analysis should be carried out accord- ing to the rules laid down by the Trust. (German Tar Produc- tion Trust on Essen-Ruhr.) (5.) The minimum calorific power must not be less than 64 FUELS 8,800 cal. per kg. For oils of less calorific power the purchaser has the right of deducting 2 per cent of the net price of the delivered oil, for each 100 cal. below this minimum. (6.) The flash-point, as determined in an open crucible by Von Holde's method for lubricating oils, must not be below 65 C. (7.) The oil must be quite fluid at 15 C. The purchaser has not the right to reject oils on the ground that emulsions appear after five minutes' stirring when the oil is cooled to 8. Purchasers should be urged to fit their oil-storing tanks and oil-pipes with warming arrangements to redissolve emulsions by the temperature falling below 15 C. (8.) If emulsions have been caused by the cooling of the oils in the tank during transport, the purchaser must redissolve them by means of this apparatus. Insoluble residues may be deducted from the weight of oil supplied. Coal tar oil is the distillate of the tar obtained from gas works, from which all valuable commercial materials such as aniline have been removed. Coal oil tar is also known as creosote oil and anthracene oil, the heat value of which is not quite 16,000 B.T.U. per pound. (19) Residual Oils. Residual oil is the residue left after the lighter oils have been distilled from the petroleum, which before the advent of the Diesel engine were useless. Residual oil which was hardly fluid at ordinary temperatures has been successfully used in the Diesel and semi-Diesel types of engines, by preheating it be- fore admission to the inlet valves. The enormously increased demand for gasoline has resulted in a great increase of the formerly useless residual oil so that it is possible that the de- mand for gasoline will make the production of the residual great enough so that it can be seriously considered as a fuel- (20) Gasoline. Gasoline is by the far the most widely used fuel for internal combustion engines because of its great volatility and the ease with which it forms inflammable mixtures with the air at ordi- nary temperatures. Another point in its favor is the fact that it burns with a minimum of sooty or tarry deposits, without a disagreeable smell with moderate compression pressures and without preheating through a v/ide range of air ratios. Gasoline FUELS 65 is a product of crude oil from which it is obtained by a process of distillation, and as it forms but a small percentage of the crude oil it is rapidly becoming more and more expensive as the demand increases. Some Pennsylvania crude oils will yield as much as 20 per cent of their weight in gasoline, while the low grade Texas and California crudes very seldom contain more than 3 per cent. When considered as a term applying to some specific product, the word "Gasoline" is a very flexible expression as it covers a wide range of specific gravities, boiling points, and composi- tions, the latter items depending on the demand for the fuel and the taste of the manufacturer. Since the specific gravity of gasoline is a factor that determines its suitability for the engine, at least in regard to its evaporating power or volatility, it is graded according to its density in Beaume degrees as de- termined by the hydrometer. According to this scale gasoline will range from 85 to 60 Beaume, and even lower, although 60 is supposed to mark the lowest limit and to form the dividing line between gasoline and naphtha. The density of the gasoline in Beaume degrees is an index to the volatility, for the higher the degree as indicated on the hydrometer, the higher is the volatility at a given temperature, consequently a high degree gasoline will give a better mixture at a low temperature than one of a low degree. In cold weather all gasoline should be tested with a hydrometer when pur- chased to insure a grade that will be volatile enough for easy starting when the engine is cold. In cold weather the gasoline should not be lower than 68, and for the best results should be above 72, at least for starting the engine. Good gasoline should evaporate rapidly and should produce quite a degree of cold when a small amount is spread on the palm of the hand, and it should leave neither a greasy feeling nor a disagreeable odor after its evaporation. The high gravity gasoline is of course the most expensive, as there is less of it in a gallon of the crude oil from which it is made; gasoline of 76 Beaume being approximately 15c. per gal- lon in carload lots, while naphtha of 58 Beaume brings 8^c. per gallon. The calorific value of gasoline increases as the gravity Beaume decreases per gallon; 85 gasoline having approximately 113,000 B. T. U. per gallon while 58 naphtha has an approximate value of 122,000 B.T.U. per gallon. The calorific value remains nearly constant per pound for all gravities. 66 FUELS It should be remembered that heat is absorbed in evaporating gasoline as well as in evaporating water, and that effects of cold weather are greatly increased by the amount of heat ab- sorbed, (or cold produced) by the vaporization of the fuel. While the heat absorbed by evaporating a given quantity of gasoline is only .45 per cent of that absorbed by an equal amount of water, it is a fact that this heat must be supplied from some source to prevent a reduction in the vapor density. In starting the engine, the heat of evaporation is supplied by the atmosphere* and should the temperature of the air be below that required for a given vapor density, the engine will refuse to start. By the use of two tanks and a three way valve, it is possible to use two grades of fuel: one tank containing high gravity gasoline, and the other low gravity; the high gravity being used for starting the engine in cold weather, and the cheaper, low gravity, being used for continuous running after the engine is warmed up the change of fuels being made by throwing over the three way valve. The VAPOR DENSITY of gasoline vapor is the ratio of the weight of the vapor compared with the weight of an equal vol- ume of dry air at the same temperature. If the weight of a cubic foot of gasoline vapor is divided by the weight of a cubic foot of air the same temperature the result will be the vapor density of the gasoline vapor. Compared to air, the gasoline vapor is quite heavy so that if a small quantity' of gasoline is poured on the top of a table, the vapor will flow over the edge of the table and drop to the floor where it will remain until it has united with the air by the process of diffusion. Experiments have shown that pure, dry gasoline vapor has a density of about 3.28, or in other words weighs 3.28 times as much as an equal volume of dry air. This weight of course is the weight of pure vapor which is considerably heavier than the mixture of vapor and air that is used in the cylinder of the engine. Dampness, or the presence of water vapor in the air reduces the quantity of gasoline vapor taken up by the air, but only by a small amount, the maximum difference being only about 2 per cent. Since it is very likely that the water vapor is broken up into its original elements, oxygen and hydrogen, by the heat of the combustion it is likely that there is no heat loss due to the vapor passing out through the exhaust. The principal trouble due to dampness is the mixture of water and liquid gasoline caused by the condensation of the water vapor. All gasolines and oils contain water to a more or less de- FUELS 67 gree, hence provision should be made for the draining of the water which collects in the bottom of the tank. Water in liquid fuels is the cause of much trouble. Water in gasoline may be detected by dropping scrapings from an indelible pencil into a sample of the suspected fluid. If water is present in any quantity the gasoline will assume a violet color. In filling a supply tank with gasoline, a chamois filter or chamois lined funnel should always be used, as the chamois skin allows the gasoline to pass but retains the water and im- purities contained therein. There are many funnels of this type now on the market. The rate at which gasoline burns depends on the amount of surface presented to the air by the fluid, for a given quantity of gasoline burns faster in a wide shallow vessel than in a deep jar. Since a spray of minute particles presents an enormously greater surface than the liquid- its burning speed is correspondingly greater, and as a true vapor has an almost limitless area, its speed is much greater than that of the spray, the combustion under the latter condition being almost instantaneous. Besides the question of subdivision of the liquid, the rate of combustion also depends on the intimacy of contact of the vapor with the air and on the pressure applied to the vapor as previously ex- plained under the head of "COMPRESSION" in another chapter. CARBURETING AIR, or producing an explosive mixture of gasoline vapor and air is accomplished by two different methods, first by passing the air over the surface of the liquid, or by pass- ing it through the liquid in bubbles; second by spraying the liquid into the air. The latter is the method most generally in use at the present time, the spray being formed by the suction of the intake air upon the open end of the spray nozzle. The vapor density of the mixture thus formed depends on the suction of the air and upon the nozzle opening, either of which may be varied in the modern carburetor to vary the richness of the mixture. As a suggestion to the users of gasoline we append the following remarks. Gasoline vapor will readily combine with air to form ex- plosive mixtures, at ordinary temperature. This property at once makes it the most suitable fuel and the most dangerous to handle. Never fill tanks or expose gasoline to the air in the presence of an open flame, or do not attempt to determine the amount 68 FUELS - of gasoline in a tank with the aid of a match. There are a number of people who have successfully accomplished this feat, and a very great number who have not. Be very sparing in the use of matches around a gasoline engine; there are such things a leaks. Always carefully replace the stopper or filler cap in a gaso- line tank after filling. Never use the same funnel for water and gasoline, and avoid any possibility of water finding its way into the tank. If you do succeed in igniting a quantity of free gasoline, do not attempt to extinguish the fire with water. Pouring water on burning gasoline spreads the fire. Extinguish it with earth or sand, or by the use of one of the dry powder extinguishers now on the market. Water may be removed from gasoline by placing a few lumps of dessicated calcium chloride in the tank, the amount depend- ing on the quantity of water. Calcium chloride, has a great capacity for absorbing water, and in a short space of time will absorb all of the moisture contained in the tank. The best way to introduce the chloride is to wrap the lumps in a sheet of wire gauze and lower into tank with a wire, the wire allowing it to be easily removed when saturated with water. (21) Benzol. Benzol has been used to some extent in Europe as a fuel, its use being due to the rapidly increasing cost of gasoline. Benzol is a distillate of coal tar, and is a by-product of the coke industry. In England benzol brings approximately the same price as gasoline (called petrol), but benzol proves eco- nomical for the reason that it develops more power per gallon. Benzol is not as volatile as gasoline, but is sufficiently volatile to allow of easy motor starting. Benzol is also used for denaturing alcohol. (22) Alcohol. Alcohol is of vegetable origin, being the result of the de- structive distillation of various kinds of starchy plants or vege- tables. Starch is the base of alcohol. ' As a fuel, alcohol has much in its favor, as it causes no carbon deposit, has smokeless and odorless exhaust, can stand high compression, and requires less cooling water than gasoline, as FUELS 69 the heat loss is less through the cylinder walls, and for this reason it is more efficient fuel than gasoline. At the present time the price of alcohol prohibits its general use. In order that alcohol equal gasoline in price per horse power hour, it should sell for lOc. per gallon, the price of gasoline being 15c. per gallon. Alcohol can be used in any ordinary gasoline engine with readjustment of carburetor and the compression. The nozzle in the carburetor has to be of larger bore for alco- hol than for gasoline, and the compression for alcohol than for in the neighborhood of 180 pounds per square inch. The inlet air should be heated to about 280F for alcohol fuel; approximately 6% of the heat of the alcohol is required for its vaporization. Alcohol is much safer to handle than gasoline owing to its low volatility. 90% alcohol has a calorific value of 10,100 B.T.U. per pound, its specific gravity being .815. WOOD, or METHYL alcohol is made by distilling the starch contained in the fibres of some species of wood (Poisonous). GRAIN, or ETHYL alcohol is the result of the distillation of the starch contained in grains, potatoes, molasses, etc. ETHYL, or GRAIN alcohol rendered unfit for drinking by the addition of certain substances, is called DENATURED ALCOHOL. The process of denaturing does not affect the calorific value of alcohol to any extent. (23) Kerosene Oil. Kerosene is a fractional distillate of crude oil which has a considerably higher vaporizing temperature than gasoline. It does not form an inflammable mixture with the air at ordinary temperatures, but is vaporized in practice by spraying it into a chamber heated to above 200F. Kerosene forms a greater per- centage of crude oil than gasoline and as there has been less demand for it up to the present time it is much cheaper. Penn- sylvania crude oil produces only 20 per cent of gasoline while the kerosene contents will average nearly 42 per cent accord- ing to figures at hand. Kerosene has a very high calorific value per gallon, 8.5 gal- lons of kerosene having the same heating effect as 10 gallons of gasoline. Because of its high calorific value and its low cost per gallon, many types of engines have been developed for its use during the last few years, several of which have been very successful. Before the advent of the modern kerosene engine 70 FUELS much difficulty was experienced with the fuel because of its high vaporizing temperature and its tendency to carbonize in the cylinder, but as the price of gasoline continued to rise, the inventive genius of the gas engine builder overcame these troubles so that the kerosene engine is now as reliable as any form of prime mover. Kerosene Vaporizer on Fairbanks-Morse Engine. The Engine is Started on Gasoline and When Hot, the Kerosene Feed is Turned on. Any gasoline engine will run on kerosene, after a manner, if the engine is thoroughly heated to insure the vaporization of the kerosene, and if the fuel heated in the carburetor. Such an arrangement is make-shift, however, and is not productive of good results in continuous service. If kerosene is to be used as a regular fuel, a kerosene engine should be used to avoid vaporizing and carbonizing difficulties as well as the sooty, offensive exhaust, and the loss of fuel represented by the soot. FUELS 71 Many kerosene engines are arranged to start on gasoline, and, after becoming heated, have the running feed of kerosene admitted through a three way valve. The gasoline feed is then stopped. The above arrangement admits of easy starting in all weathers and temperatures. In the Diesel engine there is no evaporating of fuel, and no deposits of carbon because of the high temperature of the com- bustion chamber. With engines that draw the mixture of vapor and air into the cylinder there are several methods of applying heat to the liquid, and the combustion o the vapor thus formed is perfected by the injection of water into the combustion Kerosene Vaporizer on Fairbanks-Morse Vertical Engine. Started on Kerosene Directly by Heating Vaporizer with Torch. chamber. It has been found by experiment that a small amount of water vapor introduced into the cylinder of a kerosene en- gine makes the engine run more smoothly and prevents a smoky exhaust and carbon deposits in the cylinder. The water is introduced into the cylinder through an atomizer in the form of a mist or fog, the particles of water being in a very finely subdivided state. The deposits of free carbon (soot) caused by the "cracking" or decomposition of the kerosene vapor before ignition, due to the high temperature of the cylinder, are burnt to carbon dioxide by the oxygen of the water which is also set free by the heat of the cylinder. This produces an odorless gas (CO 2 ) which in- dicates complete combustion. Besides the increase of fuel ef- ficiency due to the water vapor, the cylinder is more thoroughly cooled and is more efficiently lubricated because of the reduc- tion in temperature. CHAPTER IV INDICATOR DIAGRAMS GENERAL DESCRIPTION. An indicator is an instrument used for measuring and recording the pressures in a gas engine cylinder. It traces a scale diagram on a piece of paper from which it is possible to directly determine the valve setting, ignition timing, or pressure. By a few calculations it is possible to use it in obtaining the power developed within the cylinder. The indicator consists essentially of a small cylinder connected with the gas engine cylinder. Variations in the engine cylinder pressure cause the indicator piston to trace a line whose height is proportional to the gas pressure. The indicator piston works against a spring of known tension. The paper on which the diagram is traced is wrapped around a drum, and the drum is connected to the engine piston so that it is turned an amount corresponding to the travel of the piston. The up and down motion of the pencil caused by the piston of the indicator, combined with the oscillation of the drum about its axis, produces a diagram that shows the pressure variations in regard to the position of the piston. The indicator piston rises and falls with the gas pressure, while the point at which any event takes place is located by the position of the swinging drum. The "mean effective pressure" or the average pressure can be found by dividing the area of the diagram by its length, and then by multiplying this quotient by the number of pounds pressure required to move the recording pencil one inch. As explained in a former paragraph the length of the vertical lines represents certain definite pressures, each inch of length rep- resenting so many pounds as per square inch, the exact amount per inch depending on the indicator spring strength or adjust- ment. To make this point clear, all of the indicator diagrams shown in this chapter will be provided with a scale of pressures at the left of the diagram by which the pressure at any point may be accurately measured off for practice. It should be noted that points on the curves which are above the atmospheric line 72 GAS, OIL AND STEAM ENGINES 73 represent positive pressures above the atmosphere, and that the points lying below the atmospheric line represent partial vac- uums which may be expressed as_ being so many pounds per square inch below the atmosphere. The vacuum pressures in- dicate the extent of the "suction" created by the piston when drawing in a charge of air and gas. Straight vertical lines show that the increase of pressure along that line has been practically instantaneous in regard to the pis- ton velocity, for if the pressure increased at a slow rate this line would be inclined toward the direction in which the pis- ton was moving, as the piston would have moved a considerable distance horizontally while the pencil was moving vertically. This inclination of the vertical line gives an idea of the rate at which the pressure increases in relation to the piston speed, the greater the inclination, the slower is the rate of pressure in- crease. Straight horizontal lines that lie parallel to the at- mospheric line denote a constant pressure or vacuum. The rate at which horizontal lines descend or incline to the atmospheric line represents the rate at which the pressure in- creases or decreases, in respect to the piston position (not piston velocity). A ste'ep curve represents a rapid expansion or com- pression from one piston position to the next. A waving or rippling line indicates vibration due to valve chattering or explosion vibrations. A straight inclined line shows that the pressure is decreasing or increasing in direct proportion to the piston position. (36) Diagram of Four Stroke Cycle Engine. By referring to paragraph 25, Chapter III, it will be seen that the five events of suction, compression, ignition, expansion and exhaust are accomplished in four strokes, in the following order: Stroke 1. Suction (Mixture drawn into cylinder). Stroke 2. Compression (Mixture compressed). * *, ( Ignition. Stroke 3. \ * , . . ^ Expansion (working stroke). Stroke 4. Exhaust (Scavenging stroke). These events with the pressures incident to each drawn to some relative scale are shown graphically in Fig. 10 by four lines representing the four strokes of the piston. In order to show the relation between the diagram and the piston, a sketch pf the cylinder with a stroke equal to the length of. the dia- gram is shown directly beneath the curve. The vertical line IJ 74 GAS, OIL AND STEAM ENGINES Figs. 10-11-12. Showing Respectively a Typical Four Stroke Diagram, Retarded Combustion and Retarded Spark. GAS, OIL AND STEAM ENGINES 75 is the scale of pressures (somewhat exaggerated in order that the small vacuum and scavenging pressures shall be clearly shown). The line marked "atmosphere" represents atmospheric pressure and it is from this line that all measurements of pressure are taken. Consider the piston starting on the suction stroke, the piston moving from the position L to K, or from left to right. The movement creates a partial vacuum in the combustion chamber N which is shown on the diagram as the distance OA, equal to 2 pounds below atmosphere according to the pressure scale. The suction line remains at this distance below the atmospheric line until within a short distance of the end of the stroke when it rises to meet the atmospheric line at B when the piston reaches the end of the stroke at K. This rise at the end of the stroke is due to the fact that the piston moves more slowly when approaching the end of the stroke while the velocity of the incoming gases remains nearly constant so that the piston exerts no pull nor suction. On the diagram the entire suction stroke is represented by AB. The piston now returns on the compression stroke from K to J compressing the mixture in the combustion chamber N. On the diagram this stroke is shown beginning at B, with the pres- sure slowly rising until the pressure is a maximum at the point C at the end of the stroke. During the compression, the pres- sure has risen from that of the atmosphere at B to 125 pounds pressure at C as shown by the scale. At a point slightly before C is reached, ignition occurs, and the pressure rapidly rises from C to D, due to the expansion of the heated gas. In this case the combustion is practically instantaneous as shown by the straight, vertical combustion line CD. At D the piston starts on the working stroke from left to right increasing the volume of the gas and at the same time di- minishing the pressure because of the expansion until the maxi- mum pressure of 400 pounds per square inch at D is reduced to 30 pounds per square inch at E, the line DE being called the ex- pansion line. During this time the heated gas has been perform- ing work on the piston. At E the exhaust valve opens and the pressure drops from E to T, a point still about 10 pounds above atmospheric pressure. Theoretically the pressure should drop instantly from E to atmosphere, or from 30 pounds per square inch to zero, but practically this is impossible because of the back pressure due the slow escape of the exhaust gases through the comparatively small valve openings and exhaust pipes. 76 GAS, OIL AND STEAM ENGINES Since considerable pressure is exerted by the piston on the return stroke in forcing the gases out of the exhaust valve, the exhaust line TO on the diagram is nearly 10 pounds above the atmospheric pressure from T to O. At a point near O, the piston slows up on nearing the end of the stroke so the gases have more time to escape through the valves, and the pressure drops to the atmosphere, reading for the succeeding suction stroke. It should be noted that the points A, B, E, and F represent periods of valve action. At A the inlet valve opens; at B the inlet closes; at E the exhaust opens; at F the exhaust closes, and at A the inlet again opens at the beginning of the suction stroke AB. That this is true is apparent from the fact the inlet must open at the beginning of the suction stroke, and both valves must be closed from the point B to the point E in order to prevent the escape of the compressed charge and expanded gases from the cylinder. At the end of the working- stroke the exhaust valve must liberate the gases and remain open to the end of the scavenging stroke to eliminate the residual gas while the closed inlet valve prevents the burnt gases from being forced through the inlet pipe and carburetor. As shown on the diagram, the exhaust valve closes at the same time that the inlet opens, as F, and O both occur on the same vertical line DL. This is true theoretically, but owing to the different conditions met in practice, the actual setting of the valves may vary slightly from that shown on the diagram. Some makers of high speed engines open the inlet slightly be- fore the exhaust clones as it is claimed that the inertia of the exhaust gas passing through the exhaust pipe creates a slight vacuum that is an aid in filling the cylinder with a fresh charge. It should be borne in mind that this condition only exists when the piston has come to rest and exerts no pressure on the exhaust gas. The vacuum is due to the velocity inertia of the gas after it has been reduced to atmospheric pressure. Other makers close the exhaust valve a very little before the inlet opens, but no matter what the setting, the difference in the time of opening and closing is very small, and the results obtained probably differ by an almost negligible amount. During the suction and scavenging strokes, the fly wheel of the engine is expending energy on the gas since it is moving a considerable volume at a fairly high pressure. In the case of the scavenging stroke, the piston is working against 10 pounds back pressure, which on a 10 inch piston would amount GAS, OIL AND STEAM ENGINES 77 to a force of 785 pounds. With the 2 pound vacuum the drag on the piston would amount to 157 pounds, no small item when the velocity of the piston is considered. Of course the pressure of 10 pounds per square inch is rather high, but it is often at- tained with long and dirty exhaust pipes. It is items of this nature that cut into the efficiency of the engine, and increase the fuel bills, and it is only by the indicator that we can de- termine the extent of such "leaks" and remedy them. Since the area of the indicator card represents the power of the engine, it is evident that we lose the power represented by the area included in the rectangle FEBO on the scavenging stroke plus the area BOA on the suction stroke. The area in- cluded in BCO represents the work taken from the engine in compressing the charge, but this is returned to us during the next stroke plus the benefits gained by compressing the mix- ture. The arrows show the direction in which the piston is moving during that event. An actual engine does not follow the form of the diagram shown by Fig. 10 exactly because of certain conditions met with in practice such as imperfect mixtures, faulty valve and ignition timing, small valve areas or leakage. The combustion in the real engine is neither instantaneous nor complete but it approximates the "IDEAL" cycle just described more or less closely with a high compression and a fairly well proportioned mixture. (37) Detecting Faults With the Indicator. For the best results the gas must be completely ignited at the point of maximum compression, and the pressure must be estab- lished on the dead center, so that the indicator card will show a straight and vertical combustion line. As all gases require a certain 'length of time in which to burn, the ignition should have LEAD, that is, should be started before the end of the stroke so that combustion will be complete at dead center. The amount of ignition lead required depends on the fuel and the compression. In Fig. 10 the point of ignition (I) is shown as occurring before the end of the compression at (C), which insures a straight combustion line CD. With a lean or slow burning gas, that is, a gas slower than used on the diagram, combustion would not be complete at the end of the stroke i'f the same point of ignition were used. This effect is shown by Fig. (11), in which the full line diagram BCDE represents the ideal diagram (Y), and BCFG represents the slow burning mixture with the same point of ignition (X). 78 GAS, OIL AND STEAM ENGINES The compression curves of both diagrams are coincident as far as C, the ideal diagram shooting straight up at this point and the weak mixture diagram staying at the same level. When under the influence of the mixture (X) the piston starts from left to right and reaches the point F before the slow burning gas reaches its maximum pressure. During this part of the stroke there has been very little pressure on the piston and it Figs. 13-14. The First Diagram (13) Shows a Two Port Two Stroke Diagram, the Second Shows a Typical Diesel Card. will be noticed that the maximum pressure is far below that of the ideal diagram. This low maximum is due principally to the reduced compression under which the gas has been burn- ing, from C to F. As the gas has but a small part of the stroke left in which to expand, the pressure at the point of release is much higher than the release pressure of the ideal diagram, which means that a considerable amount 'of heat and pressure have been wasted through the exhaust pipe, Besides the heat loss, the GAS, OIL AND STEAM ENGINES 79 high temperature of the escaping gas has a bad effect on the exhaust valve and passage. The great volume of gas passing through the exhaust valve also increases the back pressure on the scavenging stroke. Delayed or retarded ignition will cause a low combustion pressure and slow combustion with any type of fuel or compres- sion pressure as will be seen from Fig. 12. In this case the compression pressures of the ideal diagram Y and the dia- gram X showing the retarded spark are of course the same, the compression line extending from B to C in the direction of the arrows. At C the ignition occurs for curve Y, and the pressure immediately rises to D. In the case of curve X, igni- tion does not occur until the point I is reached, the compres- sion falling on the line CI with the forward movement of the piston as far as the point I. At this point the compression pressure is very low which results in the slow combustion in- dicated by the slant of the combustion line IF. The point of maximum pressure F is much below D of the ideal curve, and as there is no opportunity for complete expansion during the rest of the stroke, the release pressure is high causing a great heat loss. If running on a LATE or RETARDED spark is continued for any length of time the excessive heat that passes out of the exhaust will destroy the valves. It is apparent that for the best results, the spark should occur slightly before ignition in order to gain the effects of the com- pression, and a high working pressure on the piston. It is also evident that the point of ignition should be varied for different mixtures that have different rates of burning. With engines that govern their speeds by throttling or by changing the quality of the mixture it is necessary for the best results, to vary the point of ignition with each quality of fuel that is admitted by the governor. The retard and advance of the ignition is very necessary on an automobile engine because of the throttling control and constant variation of the load and speed. All auto- mobilists know of the heating troubles caused by running on a retarded spark. (38) Two Stroke Cycle Diagram. In the two stroke cycle diagram, the lines showing the suc- tion and scavenging strokes are missing if the indicator is ap- plied only to the working cylinder. Starting at the beginning of the working stroke as at A in Fig. 13, the gas expands during the working stroke until the 80 GAS, OIL AND STEAM ENGINES piston uncovers the exhaust port at B where the pressure drops to C. A slight travel uncovers the inlet port with .the pressure still above atmosphere due to the pressure in the crank case filling the cylinder. The crank case pressure continues from C to D or to the end of the stroke, the pressure dropping slightly at the latter point. The compression stroke now takes place with the piston moving from right to left, the compression pressure reaching a maximum at F. Ignition occurs slightly before the point of greatest compression, at I, and the expanded gas increases in pressure until the point A is reached. From this point the same cycle of events is repeated. Because of the dilution of the charge by the burnt gases of the preceding combustion, the mixture burns slowly as will be seen from the inclined combus- tion line FA. Due to this delayed combustion, the piston travels the distance S on the working stroke before the pressure reaches a maximum. This diagram is typical of the small marine type of two stroke cycle engine which has no further scavenging than that performed by the rush of the entering mixture. The diagram of the pressures and vacuums in the crank case are similar to those of suction and compression in the four stroke cycle type. (39) Diagram of Diesel Engine. A diagram of the Diesel engine is different in many par- ticulars from that of an ordinary gas engine, as will be seen from the diagram in Fig. 14. The pressures rise in an even, gradual line from the end of the compression curve, and in- stead of having a sharp peak at the end of the combustion, as in a gas engine, the top of the curve is broad and greatly resembles the indicator diagram of a steam engine. The com- pression curve constitutes a greater proportion of the pressure line than that of a steam engine, the rise of pressure due to the ignition being very slight in comparison to the height of the compression curve. There is no explosion in the usual sense of the word, only a slight increase in pressure as dis- tinguished from the rapid combustion in the gas engine. Starting at the beginning of the compression stroke at H, the pressure of the pure air charge increases to about 500 pounds to the square inch at I, the point at which the fuel is injected. From I to C is the increase of pressure due to the combustion. The pressure stays at a Constant height from C to D as the fuel supply is continued between these points, and is cut off when GAS, OIL AND STEAM ENGINES 81 the piston reaches the position D. It will be seen that the admission of the fuel through the distance A covers a consider- able proportion of the working stroke, and that the points of fuel injection and ignition are coincident. From the point of fuel cut-off at D expansion begins and is continued in the usual manner to F, the point of release. When the load is increased, the period of oil injection is also increased, the other events remaining constant. Should the light load require an oil injection period as shown by A, the greater load would require injection for the period B. In the latter case, the expansion line would be E G, which would pro- duce a diagram having a greater area than the line DF, and there would be a great increase in the release pressure GH as well. It will be seen from the diagram that the quantity of air taken into the cylinder and the compression pressure remain constant with any load, and that for this reason it is possible to have a constant point of ignition, or rather point of fuel injection. As there is no mixture compressed, there are no dif- ficulties encountered at light loads due *to attenuated mixtures. An excess of air over that required to burn the fuel is also present at every load within the range of the engine. For the sake of simplicity, the suction and scavenging lines on the Diesel engine have been omitted, but they are the same in all respects as the corresponding lines shown in the diagram, Fig. 14. (40) Gas Turbine Development. In the attempt to gain mechanical simplicity, small weight, and diminutive size of the steam turbine, many able experi- menters have endeavored to obtain an internal combustion motor in which the energy of the expanding gas is converted into mechanical power by its reaction on a bladed wheel, but so far the problem is far from being solved. In 1906 two ex- perimental turbines were built by Rene Armengand and M. Lemale, of the constant pressure type, one of which developed 30 Brake horse-power and the other 300 horse-power. A 25 horse-power De Laval steam turbine was altered by Armengand says Dugald Clerk so that it operated with com- pressed air instead of steam. The compressed air was passed into a combustion chamber together with measured quantities of gasoline vapor, and the mixture was ignited by an incan- descent platinum wire as it entered the chamber, thus maintain- 82 GAS, OIL AND STEAM ENGINES ing a constant pressure with continuous combustion. Around the carborundum lined combustion chamber was imbedded a coil in which steam was generated by the heat of the burning gas, the steam being used to reduce the temperature of the gas from 1800 C to about 400 as it issued from the orifice and came into contact with the running wheel. The working medium was therefore composed of two elements, the products of combus- tion and the ^ steam at the comparatively low temperature of 400 C. The constant pressure maintained in the combustion chamber was about 10 atmospheres, and the hot gases were allowed to expand through a conical Lava jet in which the expansion pro- duced a high velocity, and reduced the temperature of the fluid. At this reduced temperature and high velocity the gases im- pinged upon the Laval wheel, and rotated the wheel in the same way as steam would have done. The experiments showed that under these conditions the total power obtained from the turbine separate from the compressor was double that neces- sary to drive the compressor. In the large 300 H. P. turbine the first part of the combus- tion chamber was lined with carborundum, backed by sand, but the second part was surrounded by a coil through which water was circulated. The water kept the temperature of the combustion chamber within safe limits, and after absorbing heat, it passed also around the jet nozzle, and was discharged into the passage leading to the jet, and there converted into steam by the hot gases. A mixture of products of combustion and steam thus impinged upon the turbine wheel. The ex- panding jet was arranged to convert the whole of the energy into motion before the fluid struck the wheel; the temperature was thus reduced to a minimum before the gases touched the blades. Notwithstanding this, the wheel itself had passages through which cooling water flowed, and each blade was sup- plied with a hollow into which water found its way. In the large turbine the compressor was mounted on the turbine spindle; it was of the Rateau type, and consisted of an inverted turbine of four stages, which delivered the compressed air finally to the combustion chamber at a pressure of 112 Ib. per sq. in. absolute. The efficiency of this turbine compressor was found to be about 65 per cent. The total efficiency of the combined turbine and compressor was low, as the fuel consumption amounted to nearly 3.9 Ib. of gasoline per B. H. P. hour. An ordinary gasoline engine with a moderate compression can GAS, OIL AND STEAM ENGINES 83 readily give its power at the rate of 0.5 Ib. of gasoline per B. H. P. hour. The combined turbine and compressor was stated to have run at 4,000 R. P. M. and to have developed 300 H. P. over and above the negative work absorbed by the compressor. A gas turbine in which there was no compression was buHt in the following year by M. Karovodine which gave 1.6 horse- power at a speed of about 10,000 revolutions per minute. It contained four explosion chambers having four jets actuat- ing a single turbine wheel, which wheel was of the Laval type, about 6 inches diameter, having a speed of 10,000 R. P. M. The explosion, chambers were vertical, and had a water jacket sur- rounding the lower end. The upper portion contained the igniting plug on one side, and the discharge pipe connecting with the expanding jet on the other. In the lower water- jacketed part there was provided a circular cover, held in place by a screwed cap. This circular plate was perforated with many holes, and it carried a light steel plate valve of the flap or hinging type, which pulled down by a spring contained within the admission passage. This spring could be adjusted, and the lift of the valve was regulated by means of a set screw passing diagonally through the water jacket. Air was admitted at one side by a pipe leading into the valve inlet chamber and a corresponding passage or pipe admitted gasoline and air or gas to mix with the air before reaching the thin plate valve. Ad- justing contrivances were supplied in both air and fuel ducts. To start the apparatus, an air blast was forced through the valve, carrying with it sufficient gasoline vapor to make the mixture explosive. The electrical igniter was started, and the spark kept passing continuously. Whenever the inflammable mixture reached the upper part of the combustion chamber igni- tion took place, and the pressure rose in the ordinary way, due to gaseous explosion. The gases were then discharged through the pipe and nozzle on the Laval wheel. The cooling of the flame after explosion and the momentum of the moving gas column reduced the pressure within the explosion chamber to about 2 Ib. per sq. in. below atmosphere. Air and gasoline vapor then flowed in to fill up the chamber, and as soon as the mixture reached the igniter, explosion again occurred. In this way a series of explosions was automatically obtained, and a series of gaseous discharges was made upon the turbine wheel. Diagrams taken from the explosion chamber showed a fall in pressure during suction of 2 Ib. per sq. in.; ignition occurred 84 GAS, OIL AND STEAM ENGINES while the pressure was low, and the pressure rapidly rose to about 1 1-3 atmospheres absolute. The pressure propelling the gas column and jet was thus only 5 Ib. per sq. in. above at- mosphere. The pressure rapidly fell, and the whole process was repeated again. According to the diagrams taken, a com- plete oscillation required about 0.026 second, so that about 40 explosions per second were obtained. The most promising type of turbine that has been built to date is that designed by Hans Holzwarth, an engineer of some prominence in the steam turbine field. A 1000 horse- Fig. 15. Cross-Section of the Combustion Chamber of the Holzworth Gas Turbine. From the Scientific American. power machine has been built at this writing and as ex- perimental machines go has made most remarkable performance. The turbine in general arrangement outwardly resembles the Curtis steam turbine, in that the turbine wheel rotates in a horizontal plane, the spindle or shaft is vertical and a dynamo is mounted on this spindle above the turbine. In the Holzwarth turbine ten combustion chambers are provided, each of a pear or bag shape. They are arranged in a circle around the wheel, GAS, OIL AND STEAM ENGINES 85 and are cast so as to form the base of the machine. The wheel is of the Curtis type, with two rows of moving and one row of stationary blades. In this turbine the energy of the fuel is liberated intermit- tently by successive explosions, instead of by continuous com- bustion, and in much the same way that the explosions occur in a reciprocating engine. Tests made on the new machine have shown that it is in no way inferior in efficiency to the ordinary type of motor, and that at full load, the weight per horse-power is only about one-quarter of that of the reciprocating engine. The weight factor, as is well known, is of the utmost im- portance in marine service and should prove of value to the marine engineer, if this alone were its only characteristic. Any of the ordinary power gases may be used with success, as well as vaporized liquid fuels, and the lower grade oils such as crude and kerosene have given much better results in the turbine, than in reciprocating engines, even at this early stage of its development. As the heat losses are much smaller than met with in ordinary practice, the temperature is higher, which, of course, greatly facilitates the vaporization of the lower grade liquids. Mr. Holzwarth does not give the dimensions of his turbine wheel, but from the drawings and some of the velocities given by him it appears to be about 1 m. in external diameter. The lower part of each combustion chamber carries gas and air inlet valves, and the upper part carries a nozzle arranged to cause the gases to impinge upon the first row of moving blades. This nozzle is connected to and disconnected from the combustion chamber by means of an ingeniously operated valve. The ex- plosion chambers are charged with a mixture of gas and air, which appears to attain a pressure of about two atmospheres within the chamber before explosion. The air and gas are supplied under sufficient pressure from turbine compressors, actuated by steam raised from the waste heat of the explosion and the gases of combustion, so that whatever work is done in compression is obtained by this regenerative action, and does not put any negative work upon the turbine itself. The com- bustion chambers are fired in series, by means of high-tension jump spark ignition. Referring to the cut, the explosion chamber A is filled in- termittently with the explosive mixture at a low pressure (about 8 to 12 pounds per square inch). When ignition has occurred, the pressure of explosion opens the nozzle valve F, allowing 86 GAS, OIL AND STEAM ENGINES the compressed gases to flow through the nozzle G to the bladed turbine H, on which the energy is to be expended. The ex- pansion of the heated gases in the nozzle reduces the pressure to that of the exhaust, with the resulting increase in the velocity of the gas. By means of fresh air, the nozzle valve F is kept open throughout the expansion and scavenging periods. After the expansion has been completed, the air that is forced through the valve D, at a low pressure, thoroughly scavenges or removes the residual burned gases left in the combustion cham- ber and nozzle, forcing it into the exhaust. When the scaveng- ing has been completed, the nozzle valve and the air valve D are closed. The combustion chamber A is now filled with pure cold air, which not only enables a fresh charge of gas to be introduced into the chamber but which also aids in keeping the chamber cool. Pure fuel gas, or atomized oil, is now injected through the fuel valve E, forming an explosive mixture ready for the en- suing cycle of events. A number of these chambers are ar- ranged around the turbine wheel in order to have a uniform application of power, by having the several chambers working intermittently. This is in effect, the same proposition as in- creasing the number of cylinders on a reciprocating engine. CHAPTER V TYPICAL FOUR STROKE CYCLE ENGINES (41) Essential Parts of the Gas Engine. On all gas engines of accepted type are found certain devices necessary for the performance of the events or cycles outlined in the preceding section. For the sake of simplicity these devices are treated as a part complete in itself. The details of construction, and the refine- ments found necessary in the actual construction will be de- scribed in the succeeding chapters. The names and purpose of these essential components, and their relation to the operation of the engine as a whole, will be found in the following outline: 1. The CARBURETOR is a device whose purpose is to vaporize the liquid fuel, and mix the vapor thoroughly and in correct proportions with the air required for the combustion, in the engine cylinder. The combustible mixture thus formed is drawn into the cylinder of the four stroke cycle engine or into the crank cham- ber of the two stroke cycle engine. GENERATOR VALVES or MIXING VALVES are similar to the carburetor in principle but are slightly different in detail. 2. The CYLINDER is the containing vessel in which the combustion and expansion of the gas takes place. The cylinder as its name would suggest has a circular open- ing or bore extending from end to end, the bore being smoothly finished to receive the reciprocating piston. 3. The PISTON is a plunger or movable plug fitting the bore closely enough to prevent the escape of gas, but at the same time is capable of sliding freely to and fro. When pressure is established in the cylinder from the com- bustion, pressure is also exerted on the end of the piston tend- ing to force it out of the cylinder. The extent of this force is governed by the area of the end of the piston and also by the pressure of the gas. 87 88 GAS, OIL AND STEAM ENGINES Thus the purpose of the piston is to convert the pressure of the expanding gas into direct mechanical force, and also to transform the increasing volume of gas into motion. Another, Piston and Connecting Rod of the Sturtevant Aero Motor, Showing Three Piston Rings. and no less important function of the piston is to compress the combustible gas in the upper end of the cylinder for ignition. 4., The CONNECTING ROD (Sometimes called the Pit- man) transmits the pressure; on the piston to the crank, the connecting rod being the means through which the to and fro motion of the piston is transmitted into the rotary motion of the crank; its action being similar to that of the human arm turn- ing the crank of a pump or windlass. 5. The CRANK receives the pressure and motion of the piston from the connecting rod, changing the reciprocating mo- tion of the piston into the rotary motion required by the machinery which the engine drives. In the majority of cases the crank revolves, while the cylinder stands still, but in some of the recently developed aeronautic motors this is reversed, the cylinders revolving with the crank stationary. The relative motion, however, is the same in both cases. (6.) The CRANK SHAFT, of which the crank is an integral part, transmits the rotary motion of the crank to the driving pulley. (7.) The admission and release of the gases to and from the cylinder are controlled by the INLET VALVE and EXHAUST VALVE, respectively, in a four stroke cycle engine. The valves are merely gates, allowing the gas to flow, or stopping it, at the proper intervals, depending on the event taking place at that time in the cylinder. GAS, OIL AND STEAM ENGINES 89 In the two stroke cycle engine there are no valves, the ad- mission and release of the gas being controlled by the position of the piston, and the openings cut in the cylinder walls. 6. IGNITION or the firing of the combustible charge is ac- complished by the IGNITION SYSTEM. In most modern engines the mixture is ignited when it is under the greatest pressure or at the end of the stroke. For maximum efficiency the mixture should be ignited when it is under the greatest pressure or compression. The time at which ignition occurs is also controlled by the ignition system. 7. The GOVERNOR regulates the speed of the engine; either by changing the richness of the mixture, by changing the num- ber of working strokes in a given time or by altering the quantity of gas admitted to the cylinder, or sometimes by a combination of these methods. 8. The BELT WHEELS or PULLEYS are the means of transmitting the power of the engine to the work to be per- formed. The engine is generally connected to- the driven ma- chinery by a belt connecting the engine pulley with the pulley of the driven machine. 9. The FLY WHEELS by reason of their mass and their momentum, store up a portion of the energy expended during the working stroke, and return it to the engine in order to carry it through the idle strokes of compression, admission and ex- pulsion. In some engines the fly wheels serve in double the capacity as pulleys. 10. The BASE or FRAME of the engine acts as a foundation for the various working parts, holding them in their proper positions. (42) Application of the Four Stroke Principle. While the five events of every commercial four stroke cycle engine are accomplished in exactly the same order, or routine as explained in paragraph (8), Chapter 3, the actual design and method of applying the cycle varies greatly in different makes of engines. This great difference in the details of construction often makes it difficult for the novice to identify the cycle of operations in that particular engine. The different forms of valve gears that are used to perform the same functions in the cycle are good examples of the variation in design, some makers using the poppet or disc type, some the sliding sleeve, and others the rotary type. Multiple cylinder engines vary in the cylinder grouping or 90 GAS, OIL AND STEAM ENGINES Fig. 16. Ball Bearing Crank Shaft, Pistons and Connecting Rods of the "Maximotor," in Their Relative Positions. arrangement, the arrangement and number of cylinders depend- ing on the service for which the engine is intended, the amount of vibration permissible, or the weight. The question of speed also introduces modifications in the design, but no matter what valve arrangement is adopted or what grouping of cylinders is GAS, OIL AND STEAM ENGINES 91 used, a four stroke cycle engine performs the five events of suction, compression, ignition, expansion and exhaust in four strokes, in each and every cylinder. With the exception of fuel injection (which in reality corresponds to the ignition event) in the four stroke Diesel engine, the indicator cards of all four stroke cycle engines passes the same characteristics as the dia- gram shown in Fig. 10. In this chapter, the engine will be described without regard to the fuel used, or to the means adopted in vaporizing it, for the vaporizing appliances are considered as being external to the engine proper, except in some of the heavy oil engines, and as the fuel is gasified before entering the cylinder the question of fuel does not affect the general construction of the engine. The majority of engines are readily converted from gasoline to gas, or in some cases kerosene, by changes in the vaporizing device, and with the exception of changing the compression pressure, little further alteration is needed. Since the vaporiza- tion and admission of the heavier oils, such as crude oil and kerosene has a more intimate relation to the engine than the use of gasoline or gas, the heavy oil engines will be described in a separate chapter in order that the process of oil burning may be. more fully explained. It should not be understood that the cycle, or principle of the oil engine differs from that of any other engine, but that the vaporizer forms such a close connection with the engine proper that they must be described as one unit. (43) Horizontal Single Cylinder Engine. An example of a modern single cylinder engine operating on the four stroke cycle principle is the "Muenzel" engine shown in Section by Fig. 17. It is of the single acting type, that is, the pressure of the gases acts only on the left end of the piston which reciprocates in a horizontal direction. Surrounding the cylinder in which the piston slides, is the water jacket (shown by the short horizontal dashes) which keeps the cylinder walls from becoming overheated by the successive explosions of the mixture. The cooling water is pumped into the jacket through the pipe shown over the cylinder, and flows out of the jacket through an outlet near the bottom of the cylinder. Both the inlet and exhaust valves are situated in an ex- tended portion of the combustion chamber to the left of the piston, the upper valve being the inlet and the lower valve, the exhaust. The valves are held on their seats by means of coil Fig. 17. Longitudinal Section Through the Muenzel Horizontal Engine. GAS, OIL AND STEAM ENGINES 93 springs that act on the upper ends of the valve springs. Admis- sion of the explosive mixture is controlled by the upper valve, and the release of the burnt gases by the lower. Pipes at the bottom of the cylinder marked "Gas Supply" and "Exhaust" convey the gases to and from the inlet and exhaust valves re- spectively. The inlet valve, and the inlet valve spring are held in one unit by a removable metal housing known as a "Valve Cage", which is arranged so that the cage, valve, and spring may be re- moved as one piece from the cylinder casting when the valves need attention by removing a few bolts. As the cage is directly over the exhaust valve, and is considerably larger in diameter, it is possible to remove the exhaust valve through the opening Fig. 18. Elevation of Muenzel Engine Showing Lay Shaft and Valve Connections. left by the removal of the inlet valve cage. Both valves are surrounded by a water jacket, as are the passages that lead to them. Both the inlet and exhaust valves are opened and closed at the proper moments in the stroke by means of cams mounted on the horizontal cam shaft shown by Fig. 18 through a system of levers. The cam shaft is the shaft running parallel to the engine bed from the crank-shaft to the end of the cylinder and turns at one-half the speed of the crank-shaft. At a point directly below the inlet valve in Fig. 18, will be seen an en- largement on the shaft on which rests the rod running from the inlet valve to the cam shaft. This is the cam. A cylindrical casing shown above the cylinder contains the 94 GAS, OIL AND STEAM ENGINES governor which maintains a constant speed at all loads by oper- ating a valve in the intake pipe which varies the quantity of mixture entering the cylinder in proportion to the load. The governor is driven from the cam-shaft by spiral gears. The igniter which furnishes the spark for igniting the gas is located between the two valves at the extreme left of the combustion chamber (Fig. 17). It should be noted that the cylinder head which closes the left end of the cylinder, and which carries the valves is separate from the main body of the cylinder. By unscrewing the bolts that hold it to the cylinder, the head may be removed when it becomes necessary to remove dirt and carbonized oil from the combustion chamber, or when it becomes necessary to re- move the piston. The cylinder barrel in which the piston works may also be removed through the opening left by the piston head when it becomes worn, and another barrel or liner may be substituted, thus practically renewing the engine at a small fraction of the cost of a new cylinder. The liner is fastened firmly to the outer cylinder casting at the left but is free to slide back and forth in the casting at the right hand end, this end being provided with a packed joint. This play given to the liner allows it to expand and contract freely with the dif- ferent changes of temperature without causing strains either in the cylinder or in the liner. (44) Multiple Cylinder Engines. Since the power exerted by a single cylinder four stroke cycle engine is intermittent, the explosive force exerted on each power stroke is much heavier than would be the case if the power application were continuous, as the explosions must be heavier to compensate for the idle periods. To reduce the strain on the engine and the vibration as well and to obtain an even turning moment it has been customary to provide more than one cylinder on engine of over 10 horse-power capacity. In this way the total power is divided among a number of cylinders, and as no two cylinders are under ignition at any one time the turning moment is more even, the vibration is less, and the strain on the engine is considerably reduced. Dividing the power in this way makes it possible to reduce the weight of the engine as less material is required to resist the strains and a small fly-wheel may be used because of the even engine torque. In order to gain the full benefit of this reduction in weight, the builders of aeronautic motors have GAS, OIL AND STEAM ENGINES 95 carried the multiplication of cylinders to an extreme, the An- toinette for example having sixteen cylinders. Engines having more than six cylinders exert a continuous pull as the impulses "overlap," that is, ignition occurs in one cylinder before another cylinder in the series ends its working stroke. The greater the F-12. Six Cylinder Maximotor. number of cylinders, the more continuous will be the torgue or turning moment. The multiple cylinder engine may be considered as a group of single cylinder engines connected to- gether, and receiving their fuel from a common source, the only Fig. F-13. Four Cylinder Buffalo Motor for Marine Service. difference between the single and multiple being in the inlet and exhaust piping and the ignition system. As a single cylinder four stroke cycle engine has one working impulse in every two revolutions, a two cylinder engine will have an impulse for every revolution as there are twice as many impulses in the same time. It should be remembered that the number of impulses given per revolution by a four 96 GAS, OIL AND STEAM ENGINES stroke cycle engine is equal to the number of cylinders divided by two. Thus, a six cylinder engine has 6 -4- 2 =. 3 impulses per revolution, and an eight cylinder, 8 -f- 2 = 4 impulses, pro- viding of course, that the engine is single acting. Arrangement of the cylinders varies with the service for which the engine is intended and the perfection of balance that is required, the principal arrangements being the "V," the "upright," the opposed, the "radial," "tandem," and "twin." The upright engine has the cylinders all on one side of the crank-shaft in a straight line, as in the four cylinder automobile engine. In this form, each cylinder has an individual crank throw the number of throws being equal to the number of cylinders. This engine is fairly well balanced in the four, six and eight cylinder types, as one-half of the connecting rods and throws are up, while the other half are down, but as the con- necting rods do not all make equal angles with the center line of the cylinder at the same time there is a slight unbalance in the four and six cylinder types. Because of the ignition se- quence, two cylinder vertical motors are in no better balance than the single cylinder type since both crank throws and con- necting rods are on the same side of the shaft at the same time. For this reason the two cylinder engine is most commonly built in the opposed type which gives perfect balance. In "V" type arrangement, one-half of the cylinders are set at an angle of about 90 with the rest of the cylinders, or in the two cylinder "V" the cylinders are set in the same plane, perpendicular to the shaft, at angle varying from 57y 2 to 90. The "V" type arrangement is adopted where light weight and compactness are the principal requirements, as the weight and length are both reduced by putting the cylinders opposite to one another by pairs, the "V" being practically one-half the length of an upright having the same number of cylinders. This arrangement permits the use of one-half the number of crank throws used in the vertical type as each crank throw acts for two cylinders. For the reason that both the cylinders of a two cylinder "V" act on a common crank throw, the two cylinder "V" is in no better balance than a single cylinder engine. An "opposed" type engine is in the most perfect mechanical balance of any engine as the crank shafts and connecting rods are not only on opposite sides of the crank-shaft, but make equal angles with the center line of the cylinders as well, at all points in the revolution. ' The explosive impulses occur at equal GAS, OIL AND STEAM ENGINES 97 C V . " O '*" . O > K o u c8 jn c <- ^j C 98 GAS, OIL AND STEAM ENGINES angles in the revolution as in the four and six cylinder vertical type. An opposed engine may be considered as a "V" having a cylinder angle of 180. In the opposed type, one crank throw is provided for each cylinder, the pistons of the opposite cyl- inders traveling in opposite directions at the same time. A "radial" or "Fan" type motor, as the name would suggest has the cylinders arranged in one or two rows around the crank case, each cylinder being on a radial line passing through the center of the cylinder with one crank throw for each row. The Gnome engine illustrated elsewhere in the book is an ex- ample of this type, the seven equally spaced cylinders acting on a common crank throw. When more than seven cylinders are used on this engine, as in the fourteen cylinder engine, two cranks are provided, each crank serving seven cylinders. This arrangement cuts down the weight of a motor enormously be- cause of the short crank shaft and case. With the ignition properly timed and the cylinders correctly spaced the firing im- pulses occur at equal angles. "Tandem" cylinders are employed only on stationary engines, the cylinders being placed on the same center line, one in front of the other, and when this arrangement is adopted it is the usual practice to make the cylinders double acting. The two pistons are connected by a rod known as the "piston rod" which extends from the rear end of one cylinder into the front of the following cylinder. Tandem cylinders require too much room for use on automobiles or motor boats, and for this reason are seldom seen in this service. The "twin" engine is a modification of the vertical cylinder arrangement, both cylinders being on the same side of the shaft and in line with one another. It is the type most gen- erally used oh very large stationary engines that have more than one cylinder, and instead of being vertical as in their prototype are generally laid horizontally. Since the twin en- gine is generally double acting, the crank throws are placed on opposite sides of the shaft. (45) Pour Cylinder Vertical Auto Motor. A common type of four cylinder vertical motor is shown by Fig. 19, which is of the type commonly used on automobiles. In order to show the general construction of the cylinder, each cylinder is cut through at a different point. The cylinder at the extreme left is shown in elevation, or as we would see it from the outside. In the second cylinder from the left, the section GAS, OIL AND STEAM ENGINES 99 is taken through the valve chamber, which projects from the side of the cylinder. A section through the center of the cyl- inder is shown on the third cylinder, and the fourth cylinder is in elevation. On cylinder No. 1, (left) is seen the exhaust pipe (32) and the inlet pipe (31) entering to valve chamber and connected to the exhaust valve and inlet valve respectively. The pipes are held in place by the clamp or "crab" (33). The exhaust pipe connects with the exhaust valve of each cylinder, and terminates at the fourth cylinder as shown by (32). Screwed into the top of the valve chamber on cylinder No. 1 are the two spark plugs (34) and the relief cock (35). Referring to cylinder No. 2, the inlet valve (42) is shown at the left of the chamber and the exhaust valve also shown by (42) is shown at the right. Above the valves are the spark plugs (34) which project into the space above the valves. Press- ing against the lower ends of the valve stems and holding the valves tight on their seats are the springs (44) which fit into the washers (45) fastened to the stems. The valve stems terminate in a nut at (48). The valve stem guides (43) form a support for the valves and at the same time form an air tight connec- tion for the stems to slide in. Immediately beneath the stems are the push rods (46) which are provided with an adjustment (48) at the upper end, and a roller (49) at the lower end. The rollers (49) rest directly on the cams mounted on the cam shaft (27), and as the irreg- ular cams revolve, the push rods are moved up and down which in turn act on the valve stems and raise the valves at the proper moment. The cams raise the valves and the springs close them. The two cams (exhaust and inlet) appear as two rectangular enlargements on the shaft (27). The bearings (53), support the cam shaft, one being supplied for each cylinder. At the extreme left of the crank shaft is shown the half time gear (20) which meshes with the gear on the crank-shaft and drives the cams. Next to this gear is the large cam shaft bearing 26. It should be noted that the section through the valve chamber taken on cylinder No. 2 is at a point consider- ably back from the center line of the cylinders and not in the same plane as the section shown on cylinder No. 3, which is taken through the center line of the cylinders. In the section of cylinder No. 3, we see the water space sur- rounding the upper portion of the cylinder with the opening (37) connected to the water manifold (36), through which the 100 GAS, OIL AND STEAM ENGINES Fig. 19. Cr9ss-Section Through Typical Four Cylinder Automobile Engine. Courtesy of the Chicago Technical College. GAS, OIL AND STEAM ENGINES 101 water leaves the cylinder and passes to the radiator. At the lower end of the stroke is the piston, one-half of which is shown in section and one-half in elevation so that internal and external appearance may be readily seen. The piston pin (60) is located approximately in the center of the piston to which it is secured by means of the set-screw (61). By means of the connecting rod (56), the motion of the piston is transmitted to the crank-shaft throw 1^54), both ends of which are provided with bronze bushings ^(59) and (58), fitting on the piston pin and crank-pin respectively.' J J3fitweea J each crank throw are the main crank shaft ^e^fin'gs' (5#) which- are provided with the bronze bushings (54). -B^lov^th-t con- necting rod ends is. the small drip trough^ con tailing" oil 'intol which the pipes on the rod ends dip when passing around the lower end of the stroke. When the pipes enter the oil puddle a small amount of lubricating oil is driven into the crank-pin bearing because of the force of impact, this force also causing oil to splash about in the crank case for the lubrication of the main crank shaft bearings and cam shaft. In order to main- tain a constant level of oil in the puddle so that the bearings shall receive a constant supply of oil, a small overflow opening is placed in the center of the puddle which allows an excess of oil to overflow into the return oil sump below. This excess of oil drains by gravity back to the oil circulat- ing pump (73), at the right which again forces the oil to the various bearings. In this way, the same oil is used over and over again until it becomes unfit for lubricating purposes be- cause of dirt or decomposition. The oil pump is driven from the cam-shaft through the level gears (66) and the vertical shaft (72). To the right of the oil pump is the fly-wheel (75) which furnishes the power for the idle strokes of the engine. At the upper end of the vertical shaft that drives the oil pump is an extension (68) which passes through the bearing (70) and drives the ignition timer shown at the top of the housing (69). The timer controls the period of ignition in the cylinders in regard to the piston position so that the spark occurs at the end of the compression stroke. At the extreme left of the engine is the radiator fan (1) which is driven from the crank-shaft pulley (16), the belt (10), and the fan pulley (1122). This fan increases the amount of cold air that is drawn through the radiator, (mounted to the left of the engine) and increases its capacity for cooling the jacket water of the en- gine. The water circulating pump is located on the opposite side of the motor. 102 GAS, OIL AND STEAM ENGINES WPS- N m Fig. 19-a. Buda Four Cylinder Automobile Motor. Carburetor Side. Fig. 19-b. Buda Motor, Pump Side, Cylinders "En Bloc." GAS, OIL AND STEAM ENGINES 103 In this motor both the inlet and exhaust valves are located on the same side of the cylinder which arrangement classifies the engine as an "L" type, the extended valve pockets forming an "L" with the center line of the cylinder. In the motor shown by Figs. F-14 F-15, the inlet and exhaust valves are on opposite sides of the cylinder as shown in the "cross-section, which classi- fies the motor as a "T" type, as the valve chambers together with the cylinder forms a "T." The latter type of motor has Fig. F-14. Cross-Section Through Wisconsin Truck Motor. "T" Type. several advantages over the "L" type, but as it requires two cam shafts, one for the inlet and one for the exhaust valves, it is not adopted by the builders of the cheaper grades of automobiles. Since the exhaust valves are on the opposite side of the cylinder, in the "T" type, the inlet air is not ex- panded nor the output diminished by the heat of the exhaust passages. The piping is less complicated which permits of a more effective arrangement of the carburetor and magneto. Since the piping in the latter type can be arranged to better advantage, less back pressure is the result. 104 GAS, OIL AND STEAM ENGINES As in the previous case, the valves are acted on directly by the cams and push rods, one cam shaft being provided on each side of the cylinders. In order to reduce the noise made by the push rods and springs, all of the springs are enclosed by F-15. Longitudinal Through Wisconsin Truck Motor. sheet metal housings or tubes. The circulating pump is shown at the left nearly on a line with the left hand cam shaft, the pump outlet being inclined toward the cylinder so that it enters the water jacket under the exhaust valves. Water leaves the jacket by the pipe shown on the cylinder tops. GAS, OIL AND STEAM ENGINES 105 From the longitudinal section it will be seen that the cylin- ders are cast in pairs, two cylinders to the pair, instead of singly as in the previous case. The large pipe crossing at about the center of the cylinders is the exhaust pipe (shown in front of the left pair), and the pipe shown under the exhaust is the water inlet pipe from the circulating pump. It will be seen from the longitudinal section that the main crank-shaft bearings are fastened to the upper half of the crank case, and are entirely independent of the lower half which acts simply as an oil shield. This construction allows Six Cylinder Rutenber Automobile Motor, with Cylinders Cast in Pairs. the oil shield (lower half) to be removed without disturbing the adjustment of the bearings, when it becomes necessary to inspect the internal mechanism. Large removable plates cover the top of the water jackets so that it is a simple matter to clean out the water space in case that it becomes coated with deposits from the water. This is an important feature as a great many of the heating troubles may be overcome by having access to the interior of the water jacket. The water outlet pipes connect with the jacket covers. Both cam shafts are driven by the gears at the right which connect with the crank shaft pinion. Fan is belt driven from an extension to the cam shaft. All bearings are supplied with oil by a high pressure force feed pump, the crank pins receiving their supply through 106 GAS, OIL AND STEAM ENGINES channels drilled in the crank shaft and pin, which in turn are connected to the oil supply of the main bearings, no dependence being placed on a splash system. After leaving the bearings, the oil drops into the crank case and drains into the sump shown at the left of the longitudinal section. From the sump, the oil returns to the oil pump from which point it is returned to the circulating system under high pressure. (46) Stationary Four Cylinder Engine. An English stationary engine, the Browett-Lindly, similar in many respects to the automobile engines just described, is Fig. 21. Cross-Section Through Browett-Lindly Engine. shown in longitudinal and cross-section by Figs. 20 and 21. This is of the "L" type of valve arrangement, but instead of having the valves side by side as in the preceding case, the inlet valve is placed over the exhaust as will be seen from the cross-section view. The exhaust valve is operated directly from the cam shaft by the push rod as in the auto engines, but the inlet valve receives its motion through a long vertical rod and horizon- tal lever, the latter being located on the cylinder head as shown GAS, OIL AND STEAM ENGINES 107 by the longitudinal section. A supplementary valve is mounted loosely on the stem of the inlet valve, and this valve is held against the seat of the gas inlet port by a short spring. A collar on the main valve spindle opens this gas valve, and, by adjusting the position, a certain amount of lag can be given, Fig. 20. Section Through Browett-Lindly Four Cylinder Stationary Engine. so that air first enters the cylinder and then, by further travel of the main valve, the gas valve opens and the combined charge is taken in. This prevents any "back fires" as the gas and air are entirely separated until they enter the cylinder. 108 GAS, OIL AND STEAM ENGINES Starting is effected by means of compressed air, and is en- tirely automatic. No compression release is provided, as this is unnecessary under the system adopted. By opening tne main compressed air valve compressed air is admitted to two valve boxes placed underneath the cam shaft, and the pressure of air raises the valves against their levers and cams. Should the swell on the cam be opposite a lever as it will be in the correct starting position, the valve cannot close, and the com- pressed air then passes to the cylinder through a check valve on the face of the cylinder, and the engine starts. The auto- matic check allows the cylinders to take in a charge of mix- Fig. 21 -a. Section Through Cylinder of Fairbanks-Morse Type "R E" Engine, with Valves in the Head. ture on the second stroke and firing takes place immediately. When the explosion pressure is greater than the air pressure the check remains closed and no more starting air enters the cylinder. Governing is effected by varying both the quantity and qual- ity of the mixture. The main valve, plunger, and rod springs, and all springs on the valves and valve motion, are arranged to be in compression. The exhaust valves are of cast-iron, and are fitted with renew- able seats in the cylinders. The admission valves are of nickel steel, and are arranged in boxes, which, when removed from the cylinders, provide the ports which give access to and space for the removal of the exhaust valves which are withdrawn vertically. GAS, OIL AND STEAM ENGINES 109 Forced lubrication is fitted throughout all bearings, valves, plunger guides, governor, cam shaft, etc., the oil under pressure being supplied by two valveless pumps, either of which is sum- cient to maintain the working pressure of oil. The normal output of the engine is 400 brake horse-power, with an allowable overload of 40 horse-power for ^ hour. The exhaust pipe is water jacketed, each section being supplied from the small pump shown at the end of the cross section. Double ignition is provided for an emergency, by two high tension magnetos, each of which is connected to a separate set of plugs. When starting the engine, an ordinary spark coil and storage battery are used until the engine gets up to speed, when the coil is cut out and the magneto is thrown in. (47) The ''V" Type Motor. An example of the "V" type motor is shown by Fig. 22, which is a front elevation of the Frontier aeronautic motor, a type that occupies a minimum of space with a minimum of weight. The cylinders are cast separately and are furnished either with iron or copper water jackets, the copper jackets being deposited over the cylinder barrels by an electrolytic process Fig. 22. End Elevation of Frontier 8 Cylinder "V" Type Motor. 110 GAS, OIL AND STEAM ENGINES in much the same way as that of the celebrated French Antoin- ette. Bolts passing through flanges on the bottom of the cyl- inder fasten them to the base. A special aluminum alloy is used for the base which is cast in a single piece with webs to receive the bearings. A unit crank-case insures perfect align- ment, prevents a greater part of the oil leakage, and forms a much stronger construction than the usual split pattern. A chamber is provided for the cam shaft at the apex of the case through which issue the pusfr-rods. Shafts and piston pins are hollow. All push rods are adjustable for wear and have steel balls running on the cams which eliminate the possibility of mis-timing through wear. Lubrication is by a bronze pump geared from the crank-shaft and is connected to an oil tank located in the base from which the oil is forced through the crank-shaft up through the hollow connecting rods to the piston pins, thence to the cylinder walls, the surplus returning to the tank in which the strainer is located. The circulating pump is driven from the cam shaft as shown in the cut and supplies the cylinders and radiator with water through the copper. water manifolds which are designed to give an equal supply to each cylinder. Exhaust manifolds are of seamless steel tubing. The cylinders are 4^ bore x 4^ stroke, and develop 60 to 70 horse-power at 1,100 revolutions per minute, which speed has been attained with an 8-foot 6-inch propeller having a pitch of 5 feet. Without radiator or propeller, the iron jacketed motor weighs 312 pounds, and copper jacketed weighs 290 pounds, the latter making a difference of 22 pounds in the weight. A high tension Bosch magneto is used which is mounted on a pad cast on the top of the crank-case and is driven from a gear meshing with the cam shaft gear. Connection is made from the magneto to plugs placed over the inlet valves in the valve caps. A 100 horse-power aero engine of the "V" type is shown by Figs. 23-24-25, which is built by the All British Engine Com- pany for the aeronautical branch of the English War Depart- ment. It has eight cylinders of 5 inch bore, by 4% inch stroke, and develops its rated horse-power at 1,200 revolutions per minute. Data from "Aero," London. ' The crankshaft, which is of three per cent nickel chrome steel, having an ultimate tensile strength of 157,000 Ibs. per sq. in., is of distinctly large diameter, and is carried in plain bearings GAS, OIL AND STEAM ENGINES 111 Fig. 23, Longitudinal Section Through A. B. * C. 100 Horse-Power "V" Motor. 112 GAS, OIL AND STEAM ENGINES lined with white metal. It is provided with four throws, each crank pin being arranged to take the big end bearings of two connecting rods from cylinders on opposite sides of the crank case. There is a bearing between each throw, and in order to reduce the overall length of the engine the cylinders are stag- gered on the crank case. The H section connecting rods are stamped out of steel having a tensile strength of 90,000 Ibs. per sq. in., and for the purpose of lubrication a hole is drilled from end to end down the center of the web. As mentioned before, Fig. 24. Valves and Valve Motion of A. B. C. Motor. ("Aero," London.) the cylinders are staggered, and there is no overhanging of the big end bearings at the point of attachment to the con- necting rod. The bearings themselves are lined with white metal. The small end bearings are provided with phosphor bronze bushes, and the piston pin is of steel bored out hollow and hardened. A very interesting detail of the engine is the combination of the water outlet pipe from the top of the cylinder with the bearings for the rocking arms (which are steel stampings) actuating the valves. This is shown in Fig. 25. A hollow steel column is bolted to the top of the cylinder and protrudes from the water jacket, which is fastened to it with the usual shrunk GAS, OIL AND STEAM ENGINES 113 ring. To this column rs attached a hollow T shaped pipe of phosphor bronze, the column of the T piece forming the out- let for the water. On one arm of the T piece the exhaust rocker takes its bearing and on the other the inlet rocker. Each T piece arm is connect A to its fellow on the next cylin- der by means of rubber pip . Fig. 25. End Elevation of A. B. C. Motor. A small bracket projecting from the T piece forms a saddle on which the valve spring rests. This is a plain semi-elliptical leaf spring which works both valves. It is slotted at each end and slightly turned up so as to engage with a cotter pin passed through a slot in the end of the valve stem. The crank case is of rather unusual design, being absolutely circular in section and machined all over. It is practically a tube with flanged portions bolted on to form the ends. Having no horizontal joints, it is strong and easily kept oil tight. Three 114 GAS, OIL AND STEAM ENGINES radial arms, with slight webs and reinforced with steel colums down the center, support each bearing. The crank case is car- ried by four feet, which are arranged to accommodate three different widths of engine bearer. To the fore end of the crank case is bolted a long conical aluminum nose carrying at its ex- tremity a compound push and pull ball bearing 6 in. in diameter, which supports an extension shaft bolted to the crankshaft by means of a flanged coupling. Fig. 24-a. "Sixteen" Cylinder Favata Radial Type Aero Motor, Con- sisting of Four Groups of Two Cylinders Per Group. Cylinders are of the Double Acting Type and are Stationary. At the outer end of this extension is a flange to which the propeller is bolted, but the arrangement is specially devised to make quick detachment possible. The boss of the propeller has a hollow hub and is plate bolted permanently to it by twelve bolts. The direct nose is interchangeable with a speed reduction gear so that the propeller can be driven at a lower speed than the engine. Fitting this gear nose raises the center line of the propeller-shaft some 5% in. The gears are carried on sub- GAS, OIL AND STEAM ENGINES 115 stantial ball bearings, plain bearings being used also in such a way that they take up the load if the ball bearings through any cause should fail. The reduction is by means of silent chains. The arrangement of the gear wheels is plain from the drawing, and it will be noticed that there is no intermediate wheel be- tween the crankshaft pinion and the camshaft wheel, which are of steel and phosphor bronze respectively. A separate gear wheel is provided on the camshaft for driving the magneto. The water and oil pumps are carried low down outside the crank case, and are driven by intermediate wheels at double the engine speed. The shafts are joined together through Oldham couplings, so that it is possible to remove the pumps separately. Both these pumps are of the gear type. The camshaft is made in one piece with the cams, and is hardened, being drilled out for lightness. It is enclosed in a casing of steel tube, which .is practically separate from the crank case, being attached thereto at one end by the timing gear case and at the other by a saddle. The camshaft is car- ried in six bearings. An interesting point is the fact that the gear wheels are bolted to flanges on the shafts instead of be- ing attached by keys. Carried in the tube directly above the camshaft is a second shaft forming the fulcrum of the rocking arms for the cam rollers. A very interesting point is the pro- vision of an arrangement for lifting the exhaust valves. The little rocking arms carrying the rollers which bear upon the cams are provided with webs, parallel with the camshaft and between it and the shaft carrying the rockers is a third shaft,' the sides of which normally just clear the webs of the rock- ing arms on either side. This shaft is provided with wedge shape pieces along it, so that by sliding it along the wedges lift the rocking arms clear of the cams, and thus, through the tappet rods and rockers, the valves themselves are opened. Not the least interesting particular of this engine is the thorough way in which the lubrication is carried out. Four of the bolts which attach the caps of the main bearings are prolonged through the bottom of the crank case, and serve to carry a detachable oil sump which holds sufficient oil for a run of six hours. As already mentioned, the oil pump is driven at twice the engine speed, and maintains a pressure of something like 110 pounds per square inch. It delivers directly into a straight steel tube placed along the bottom of the crank case, and from this tube a vertical tubular connection is taken to each of the caps of the main bearings. The crankshaft and crank pins are 116 GAS, OIL AND STEAM ENGINES Fig. 26. Mesta Engines on Test Floor. GAS, OIL AND STEAM ENGINES 117 hollow, and, as in the previous engine, in the hollow portions tubes of a slightly smaller diameter are placed, the tubes being expanded over at the ends, so that closed annular spaces are formed which are used as lubrication leads. The lubricating oil passes through the main bearings into these annular spaces in the shafts, from them to the annular spaces in the crank pins, and so to the big-end bearings. From the big-end bear- ings it travels up the connecting rods to the gudgeon pins. It is interesting to note at this point that the connecting rods work in slots in tfce crank case which just allow sufficient clear- ance for their travel, in order to prevent the flooding of oil into the cylinders. A steel-lined oil lead is taken up to the saddle which supports the tubular camshaft casing at the pro- peller end of the crank case. The bearings carrying the cam- shaft are cut away at their lower edges clear of the tube so that the oil can flow along the full length of the casing, the level being sufficient to allow the cams to dip. Precautions are taken to keep oil from flowing out of the bearings, and the casing over the gears is specially arranged to prevent the oil from flooding below. (48) Mesta Gas Engines. The Mesta four stroke cycle, double acting gas engine, built by the Mesta Machine Co., Pittsburgh, is an excellent example of American big engine practice. Mesta engines are built in sizes from 400 horse-power up to the largest used, and is built either in tandem or twin tandem units. While the engine does not differ widely in either principle or construction from en- gines of the same size it has several features worthy of note that are not found on other engines. Up to the medium sizes, the cylinders are cast in one piece, the largest cylinders being made in two parts of cast steel with air furnace iron bushings. The central part of the cylinder is open as will be seen from the cuts, and is covered with a cast iron split band bolted at the center line. The valve cham- bers are located directly opposite one another on a vertical center line, the inlet valve being at the top and the exhaust valve at the bottom. This arrangement gives a better dis- tribution of the mixture, increases the output with given size of cylinder and equalizes the stresses occasioned by the ex- plosions. As the e"ngine is double acting in all cases there is one inlet and one exhaust at each end of the cylinder. Both the inlet valve and the corresponding exhaust valve on 118 GAS, OIL AND STEAM ENGINES each end of the cylinder are operated by a single eccentric on the horizontal lay-shaft shown running below and parallel to the cylinders. The regulating valves which are controlled by the action of the governor are perfectly balanced against the pressure in the cylinder which results in a very small resist- ance to tHe governor action, therefore no oil relay nor similar complications are required. Any of these valves are easily re- moved for clearing, a point of great importance when running on a gas that is laden with tar or other impurities. Fig. 27. End View of Mesta Engine. The chrome-vanadium piston rod carries the pistons float- ing free from the cylinder walls reducing the wear on the bore, while the piston rings maintain a gas tight contact with the cylinder walls. Each piston rod is made in two halves, the joint between the sections being made between the cylinders at which point the rods are supported by an .intermediate cross- head and guide. Both parts of the rod are interchangeable. The pistons are made in one casting. As will be seen from GAS, OIL AND STEAM ENGINES 119 the accompanying cuts the front end of the piston rod is car- ried by a cross-head which relieves the pressure on the piston and packing glands. Speed regulation is performed by the governor by control- ling both the quantity and the quality of the mixture. Inde- pendent valves in the gas and air passages are actuated by the governor according to changes in the load. This method of control combines all of the good features of quantity and quality regulation. Make and break ignition is used, with the igniter trip gear so designed as to allow all of the igniters to be timed from one lever, or adjusted independently as the case may require. Each combustion chamber is supplied with two igniters, one at the top and on at the bottom, which insures regular and rapid combustion and therefore gives a maximum of efficiency and reliability. Compressed air is introduced into the cylinders for starting at a period corresponding to the power stroke in normal opera- tion. This is accomplished by cam operated poppet valves located in the air main a/id check valves in the cylinders. By this system the engine can be started and put on full load in less than one minute. (49) Knight Sliding Sleeve Motor. The Knight motor was the first four stroke cycle automobile motor to employ an annular slide valve in place of the usual poppet valve. Its success has led to the development of sev- eral other motors of a similar type which follow the construc- tion of the original engine more or less closely. Being free from the slap bang of eight to twelve cam actuated poppet valves which hammer on their seats at the rate of a thousand blows per minute, the Knight motor is free from noise and vibration. Instead of the jumping of a number of small parts, there is only the slow sliding of the sleeves over well lubricated surfaces. They make no noise because they strike nothing and can cause no vibration because they are a perfect sliding fit in their respective cylinders. Besides insuring noiseless operation, the valves increase the output, efficiency and flexibility of the motor for they are posi- tively driven and are not affected in timing by fluctuations in the speed. The wear of the reciprocating increases the effi- ciency of the sleeve instead of destroying it. With poppet valves at high speeds, the valves do not seat properly irr rela- 120 GAS, OIL AND STEAM ENGINES tion to the crank position owing to the inertia of the valves and to the gradual weakening of the valve springs which delays the closing of the valves.. Carbon also gets on the seats of the poppet valves and prevents proper closure. These faults cannot exist with sliding sleeves when they are once set right Fig. 28. Section Through Knight Motor Showing the Sleeves, Eccen- trics, and Automatic Adjustment for Lubrication. Inlet is at the Right, Exhaust at the Left. as they are positively driven through a crank and connecting rod. At high engine speeds the velocity of the exhaust and inlet gases is very high in the poppet valve type due to the many restrictions and turns in the passages which causes back pres- GAS, OIL AND STEAM ENGINES 121 sure and a considerable loss of power. With the sliding sleeve type an ideal form of combustion chamber is possible and the passages to and from the chamber are short and direct. Very large port areas with a low gas velocity are also possible. The sleeves are more effectively cooled than the poppet type, being in direct contact with the water cooled walls for their entire INLET OPENS INLET CLOSES INNER SLEEVE UP OUTER SLEEVE IS MOVING DOWN BOTH SLEEVES ARE MOVING UP IN REGISTER. BOTH SLEEVES ARE MOVING INNETR CLOSEIS. 29 30 Figs. 28-29-30. Showing Sleeve Positions on the Inlet Stroke. (Knight Motor.) length. Because of the large port areas, the cylinders receive a full charge of mixture, and as a result the engine accelerates and gets under way with remarkable ease. The arrangement of the slide valves, or sleeves, is shown by Fig. 28, which also gives an idea of the cylinder form, and 122 GAS, OIL AND STEAM ENGINES the location of the piston. Fitting the engine cylinder closely, one within the other, are the two sliding valve sleeves, and within the inner sleeve slides the power piston. Each sleeve has two slots cut in it, one on each side, which form an outlet and inlet for the exhaust and inlet gases respect- ively. When the slots on the intake side of both the outer and OPEN EXHAUST CLOSES BOTH ARE MOV- ING DOWN; BOTH BLOTS ENTERING BOTH ARE MOV- ING DOWN IN INNER SLEEVE UP. OUTER SLEEVE IQ MOVIN DOWN. 31 32 33 Figs. 31-32-33. Showing Sleeve Positions on the Exhaust Stroke. the inner sleeves register, or come opposite to one another, and also opposite to the intake pipe, a charge of gas is drawn into the cylinder. After the explosion has taken place, the sliding motion of the sleeves brings the other two openings, on the exhaust side, opposite to one another, and opposite the GAS, OIL AND STEAM ENGINES 123 exhaust pipe, which allows the burnt gas to escape to the at- mosphere through the exhaust manifold. The sleeves are driven from cranks on the half-time shaft shown at the side of each cut, through the small connecting rods, which gives them a reciprocating motion. Like the cam shaft on a poppet valve motor, the lay shaft runs at half the crank shaft speed, since the engine is of the four-stroke cycle type. The lower ends of the sleeves,, to which the connecting rods are fastened, are made thicker than the portion within the cylinder, and are heavily ribbed for strength in the over- hang. The sleeves are of the same composition of cast iron as the cylinder and are provided with oil grooves cut in their outer surfaces for gas packing, and the distribution of oil. Leakage between the inner sleeve, and the cylinder head is prevented by a packing ring, or "junk" ring that is fastened to the bot- tom of the inwardly projecting cylinder head. The junk ring not only prevents the leakage of gas during the explosion, but it also serves another purpose. The exhaust ports or slots in the inner sleeve are above the junk ring during the explosion, in which position they are pro- tected from contact with the burning gas. The life of valves is greatly increased by this protection. It will be noted that the entire surface of the sleeves is in contact with water jacketed surfaces, making perfect lubrication and smooth working pos- sible. The two spark plugs for the dual ignition system are shown in the depressed cylinder head. Complete water jacketing encircles the cylinders, cylinder heads, the circulation area enclosing the plugs and the gas passages so that a uniform heat is maintained the entire length of the piston travel. The half-time shaft, the magneto, and the water pump are driven by a silent chain from the crank case; this drive being found superior to the gears commonly used for this -class of work. The cranks on the half-time shaft are made in one in- tegral piece with the shaft. Although the piston on the- Stoddard-Dayton Knight motor has a stroke of 5 l / 2 inches, it is scarcely as much as this con- sidered as friction producing travel, because the inner sleeve in which it rests moves down in the same direction l^j inches. This distribution of the working stroke to two surfaces reduces the wear on the side of the sleeve caused by the angu- larity or thrust of the main connecting rod. On the compres- 124 GAS, OIL AND STEAM ENGINES sion stroke, both outer and inner sleeves go up in the same direction as the piston, the inner sleeve moving the faster. On the exhaust stroke and suction stroke the sleeves move in a direction opposite to the direction of the piston, but on these strokes there is very little work performed by the piston and consequently little thrust is produced on the sleeves and walls of the cylinder. It is a valuable feature to have the sleeves descend with the piston on the working stroke because this is the stroke in which the piston has the greatest amount of side thrust. The up and down movement of the sleeves is very little com- pared with that of the piston. A stroke of S l / 2 inches gives a piston speed of 916 feet per minute at a speed of 1,000 revolu- tions per minute. The stroke of the sleeves is 1^ inches and its speed is but 93.7 feet per minute, or a little more than one-tenth that of the piston. This fact makes the problem of lubrication a feasible one, the slow-movement of the sleeves distributing the oil thoroughly between them as well as be- tween the outer sleeves and the cylinder walls. The action of the valves, and their position at different points in the cycle, is shown in diagrammatic form by Figs. 28-29-30- 31-32-33, the particular event to which each diagram refers being marked at the foot of the cuts. The direction of the sleeve movement is indicated by the arrows at the bottom of the sleeves. Particular attention should be paid to the posi- tion of the slots in the sleeves. The first three diagrams show the position of the inlet shots that govern the admission of the combustible gas from the carburetor. Fig. 28 shows the slots coming together to form an opening in the inlet port as the lower edge of the outer sleeve separates from the upper edge of the inner sleeve. The outer sleeve is now moving rapidly downward while the inner sleeve is slowly rising, and as their motion is opposite the opening 'is quickly formed. Fig. 29 shows the full opening with the slots in register. When closing (Fig. 30) the outer sleeve is nearly stationary while the inner sleeve is rising ra'pidly. When the inner sleeve port is covered by the lower edge of the junk ring, the valve opening is closed, the slot in the outer sleeve remaining oppo- site the inlet opening. The exhaust port opens (Fig. 31) when the lower edge of the slot in the inner sleeve leaves the junk ring in the cyl- inder head, the sleeve moving rapidly downward at the mo- GAS, OIL AND STEAM ENGINES 125 ment of opening. To obtain a rapid opening of the exhaust, the ports are arranged so that the inner sleeve is just about to reach its maximum speed at the time of opening. The outer sleeve closes the port (Fig. 33), closure starting when the upper edge of the outer sleeve coincides with the lower edge of the cylinder wall port. At this time the outer sleeve is traveling downward at maximum speed, so that the closing of the exhaust is as rapid as the opening. The lubrication of the Knight motor is accomplished by what is known as the movable dam system, which overcomes the tendency of the motor to over-lubricate. A movable trough is placed under each connecting rod, in the crank case, that is connected to the carburetor throttle lever in such a way that the opening and closing of the throttle raises and lowers the troughs. When the throttle is opened, raising the troughs, the points on the ends of the connecting rods dip deeper into the oil which creates a splashing of oil on the lower ends of the sliding sleeves. In this way the oil is fed to the engine in direct pro- portion to the load and the heat produced in the cylinder. When the motor is throttled down, the points barely dip into the oil. An excess of oil is fed to the troughs by an oil pump, which keeps them constantly overflowing. The overflow is caught in the pumps located in the crank case, and returned to the circu- lation so that it is used over and over again. Claims of great efficiency are made for this system, there hav- ing been many tests made showing 750 miles per gallon of oil, while even as high as 1,200 miles per gallon has been made un- der favorable conditions. The oil pump is contained in the crank case, and is of the gear type, insuring positive action. The pump also acts as a distributer, a slot being cut in one of the gears which register successively with each of the six oil leads. In this way it is possible to obtain the full pump pressure in each lead should they become obstructed in any way. In the upper half of the crank case are cored passageways through which the air passes before reaching the carburetor. These passages not only eliminate ^he rushing sound of the intake air, but also form an efficient method of warming the air supplied to the carburetor and cooling the crank-case. It is possible to furnish warm air after the engine has been idle for several hours, as the oil in the crank case remains warm longer than any other part of the engine. 126 GAS, OIL AND STEAM ENGINES (50) Reeves Slide Sleeve Valve. A simple and compact form of slide sleeve valve gear has been developed in England that is of more than passing interest. It permits of a maximum area for both the inlet and exhaust gases which of course keeps the velocity and back pressure at a minimum for a given valve lift. The small lift also insures noiseless operation and a small amount of wear. The sleeve Fig. 34. Reeves Slide Valve Gear. is balanced at the end of the working stroke. The combustion chamber is nearly hemispherical in shape which reduces the heat loss to the walls. Referring to the section of the end of cylinder given in the diagram, (34) A is an .open-ended water-jacketed cylinder in which the piston B works. At the upper end of the cylinder is attached a ring C forming an extension of the stationary cylin- drical head D carrying the sparking plug. At the lower end of the head D is provided a seating E for the sliding cylindrical GAS, OIL AND STEAM ENGINES 127 inlet valve F, which takes its bearing around the circular head. This inlet valve is provided with expanding rings G to keep it gas-tight. Surrounding the inlet valve F is a second cylindri- cal exhaust valve H, which is provided with an angular seating at J. The outer circumference of the cylindrical exhaust valve H bears against the walls of the cylinder. Cast in the cylinder is an annular space K communicating with a passage L for the admission of the inlet gases. These pass through suitable ports cut in the sides of the exhaust valve H and the inlet valve F, so that they are free to pass through the space made when the inlet valve F is lowered from its seat. A similar type of annular space M is cast in the cylinder in connection with an opening O for the passage of the exhaust gas when the cylindrical valve H is raised from its seating at J. The cylinder head is not water jacketed as the builder states that the continual passage of the intake gases keeps it reason- ably cool. The exhaust passages are thoroughly water cooled. (51) Argyll Single Sleeve Motor. The Argyll sliding sleeve automobile motor is unique in the fact that only one sleeve is used to control both the inlet and exhaust gases instead of the two sleeves commonly used on the Knight motor. This sleeve, instead of having either a purely vertical or horizontal motion, has a peculiar combina- tion of the two, that is to say, it moves a certain amount in rotation within the cylinder, and an equal amount vertically, the combined motion constituting an ellipse. The external ap- pearance of the engine is shown by Fig. 35, which will give an idea of the general arrangement of the cylinders, ports and piping. In Fig. 36, is shown the successive movements and events determined by the sleeve, and the method of opening and clos- ing the inlet and exhaust ports by the elliptical movement of the sleeve. The shaded ports are one of the inlet and one of the outlet ports, respectively, which are cast in the cylinder wall, and are afterwards machined true. The dotted port, which changes its position in each diagram, is one of the ports in the moving sleeve, its position in each of the figures is marked by the event that is occurring in the "cylinder at that time. In diagram 1, the shaded port to the right is the exhaust port, and the shaded port to the left, the inlet, this relative arrangement being true, of course, in each of the succeeding 128 GAS, OIL AND STEAM ENGINES diagrams. It will be noted, that in the position shown, in the exhaust stroke (beginning of stroke), the sleeve port has just started on its downward stroke, moving also a trifle to the right as it progresses. Its progress to the right may be more clearly seen by consulting diagram 2, for the movement. By consulting the other five figures it will be seen that the dotted port, in its relation to the shaded ports, first moves out to the right, and then reverses, moving to the left, and this combined wih the up and down movement constitutes an ellip- Fig. 35. Elevation of Argyll Single Sleeve Motor from The Motor, London. tical path. In diagram 6 the exhaust is closed, and the inlet port has just begun to open, the dotted port now starting to move out to the left, and to rise. In diagram 10, the inlet is nearly closed, the sleeve port pass- ing away from the cylinder ports to the water jacketed portion of the cylinder above. This series of diagrams shows the operation of the dupli- cated port of the sleeve (which port is the one shown dotted) in relation with one of the inlet ports and one of the exhaust ports in the cylinder wall, the latter ports being marked re- spectively I and E. The elliptical movement referred to in the text can be traced by following the different positions of the GAS, OIL AND STEAM ENGINES 129 dotted port in the sleeve. In the top row of diagrams it is seen to come downwards and also to move over to the left, whilst in the lower set it rises bearing still to the left until, after Fig. 10, it goes higher up for the compression and ex- plosion strokes, during which it bears over to the right and comes down again ready to commence once more the cycle, as in Fig. 1. The other ports in the cylinder wall are the same CXMAUfcT BCCINS TO ClO<> inter.. \oecmsTo CLOSE r,c. a X 'IN1XT MBAIU.Y CLOSED / I FlC.9. PlC. 10 Fig. 36. Valve Motion Diagram of Argyll Motor Showing the Valve Positions at Different Parts of the Working Stroke. as those shown, and the other ports in the sleeve are akin in shape to half of the dotted port, but they are without the little tongue cut in the base of this double purpose port. This little tongue in the duplicated port is designed to give as much lead to the exhaust opening as possible, without interfering with the correct timing of the inlet port. The way in which it just misses interfering with the closing of the inlet port is seen in Fig. 10. We are indebted to "The Motor" for these cuts. 130 GAS, OIL AND STEAM ENGINES (53) Sturtevant Aeronautical Motor. The cylinders of the Sturtevant aeronautical motor are of the "L" type and are cast separately with the cylinder barrel and water jacket in one integral casting. A special iron is used for these castings that has an ultimate tensile strength of 40,000 pounds per square inch. The valves which are easily accessible through valve covers, are operated directly from the cam shaft without valve rockers. A hollow cam shaft is used with integral cams to insure a maximum of strength with a minimum of weight, and bearings are placed between each set Fig. 41. Six Cylinder Sturtevant Aero Motor. of cams. A bronze gear fitted on the cam shaft meshes with a gear on the crank shaft without intermediate idlers. Like the cam shaft, the crank is bored out from end to end with a propeller flange applied on a taper at one end of the shaft. A bearing is provided between each throw with an addi- tional thrust bearing at the forward end of the shaft which may be arranged to take either the thrust or the pull of the pro- peller. Lubricating oil is applied to all the bearings under a pressure of twenty pounds per square inch, this pressure being maintained by a gear pump attached directly to the end of the cam shaft. The oil is transferred from the pump to the bearings through passages cast in the base, no piping being used> Oil enters the hollow crank shaft at the main bearings and is con- GAS, OIL AND STEAM ENGINES 131 ducted through the arms to the connecting rod bearings. The oil flying from the crank shaft falls into the oil sump at the bottom of the case where it is cooled before being used again. A second gear pump in tandem with the first takes the oil from the sump and forces it through a filter into the tank. This system enables the use of a more efficient filter than with the suction type and eliminates any danger of its becoming clogged and stopping the oil supply, since, in the event of such an occurrence the pump would furnish sufficient pressure to 132 GAS, OIL AND STEAM ENGINES burst the filter. However, the filter is particularly accessible and may be instantly removed for cleaning without disturbing the oil. The tank regularly fitted to the motor holds sufficient oil for three hours' use. If the engine is required to operate for a longer time without opportunity for replenishing the oil sup- ply, a larger tank can be used. As no oil is allowed to accu- mulate in the base with this system of lubrication, the motor can be operated continuously at an angle. Water circulation is maintained by a centrifugal pump of large capacity, the impeller of which is mounted directly on an extension of the crank shaft, eliminating the usual bearings and its grease cup. The ignition is provided by a high-tension Mea magneto, its special construction permitting the motor to be started under a retarded spark avoiding the danger of back kick from the propeller. The cylinder and all exposed parts are rendered absolutely weather-proof by means of a heavy coat of nickel plating. (54) The Rotating Cylinder Motor. While it is the common belief that the rotary cylinder gaso- line motor is of French origin it may safely be said that this type of motor was in actual use in America for several years before it even reached the experimental stage in Europe. The Adams-Farwell Company of Dubuque, Iowa, were driving auto- mobiles successfully with a rotary cylinder motor before Or- ville Wright flew at Fort Meyer, Va. Although the original Farwell motor more than proved its right to existence by faith- ful service under the most exacting conditions, the motor never received the consideration that it deserved, probably because of its great divergence from what is known as "accepted prac- tice." In Europe no such prejudice existed, and consequently the type made rapid strides, although, to the writer's belief, the European model is inferior in many ways to the original Ameri- can type. The fact that this type of motor holds practically all of the world's aviati9n records speaks for its practicability in spite of its unusual construction. With the rotary motor, the cylinders and crank case revolve about a stationary crank shaft, the latter part not only serv- ing as a point of reaction of the cylinders but as a support and intake pipe as well. Since the crank throw remains stationary, the cylinders and pistons revolve about two different centers, GAS, OIL AND STEAM ENGINES 133 the cylinders revolving about the crank case and the pistons and connecting rods about the crank pin. Since the pistons, cylinders, and connecting rods must necessarily revolve to- gether, as one unit, there is absolutely no reciprocating mo- tion in regard to the crank shaft except for a very slight move- ment due to the difference in angularity of the connecting rods. The motion of all the parts is strictly rotary in every sense, ex- cept for the relation of the pistons to the cylinders, and the motion is as continuous as in a turbine. This insures freedom from vibration. As the cylinders and crank case have consider- able inertia there is no need of the added weight of a fly-wheel. The movement of the piston in the cylinder" bore is brought about by the difference in the centers about which these parts revolve. This gives cylinder displacement without the reversal of stresses or shock or. jar. Because of the revolving cylinders, the mixture is supplied to the crank case through a hollow shaft, the gas being drawn into the cylinder on the suction stroke through an inlet valve placed in the head of the piston. As a rule, the exhaust is direct to the air through the exhaust valves and without manifolds or mufflers. The motion of the cylinders through the air multiplies the efficiency of the radiating Fins. . (55) The Gyro Rotary Motor. In the Gyro motor, made by the Gyro Motor Company of Washington, D. C., are embodied all of the principles of the typical revolving motor, but with extensive improvements in the design and in the details. It weighs 3^4 poun-ds per horse- power, complete. This light weight is due to the design of the_ motor and to the use of alloy steels, and is attained without sacrificing strength or durability. Each cylinder is machined out of a heavy 3^ per cent tubular nickle steel forging that weighs nearly 40 pounds. After the metal is removed and the cylinder worked down to size, the shell weighs but 6y 2 pounds. The radiating ribs on the outside of the cyl- inder are machined out of the solid bar, and are arranged in helicoid or screw-like formation around the cylinder barrel. This adds to the strength of the cylinder and also aids in the circulation of the air. The comparative thickness of the cyl- inder wall may be seen from Fig. 44. The stiffening effect of the radiating ribs will also be noted. The crank case to which the cylinders are fastened is of vanadium steel, and is divided into two parts. In addition to supporting the cylinders, the 134 GAS, OIL, AND STEAM ENGINES Fig. 45. Section Through Rotary Gyro Motor. GAS, OIL AND STEAM ENGINES 135 crank case also serves as a mixing chamber for the gasoline and air. By removing the bolts seen between each cylinder, the entire working mechanism can be laid bare for inspection. The exterior of the case carries the exhaust valve mechanism and the ignition distributer. The crank shaft is a nickel steel forging with an elastic limit of 110,000 pounds. It is bored hollow throughout its length and serves as an intake mani- fold by conveying the mixture from the carbureter, attached to its outer end, to the crank case. The intake valves in the heads of the piston are mechanically operated by a specially patented movement which consists of two parts, a counter-balancing member, and an operating mem- ber. The counter balance balances the valve against the dis- turbing influence of the centrifugal force, while the operating member, which is fastened to the connecting rod, controls the opening or closing of the valve by the angular position of the connecting rod. This valve action insures a full opening of the valve and a full charge during practically all of the suction stroke. There are two separate paths provided for the exhaust gases, one being through the auxiliary exhaust ports at the end of the stroke, and the other path through the exhaust valve located in the cylinder head. The auxiliary ports may be seen in the cross- section directly below the piston head in cylinders 4 and 5. The auxiliary ports are uncovered by the piston at the inner end of the working stroke, and it is at this point that the greater percentage of the exhaust leaves the cylinder. These ports or holes are formed on a projecting annular ring in which enough material is provided to make up for the strength lost by boring the ports. As these ports are, in the majority of cases, bored at an acute angle with the center line of the cylinder, it is im- possible for the cylinder oil to escape. All exhaust valves are operated by levers and push rods con- nected to a cam mechanism on the outside of the crank case. A single cam ring operates all of the valves except where a step-by-step compression is desired. The exhaust mechanism is provided with a simple device by which the closing of the exhaust valve may be delayed through any portion of the ex- haust stroke, thus reducing the compression and adding to the facility of cranking. The motor is started with the compression entirely released in which condition it can be spun about its shaft with ease. After giving the motor its initial spin, the compression and 136 GAS, OIL AND STEAM ENGINES spark are thrown in and the engine begins its normal opera- tion. The compression release lever may be used for starting or slow running and in cutting off the power regardless of the ignition advance or retard. One connecting rod, called the "master" rod, is an integral part of the spider that contains the ball bearings of the crank pin, thus controlling the angular relation between the connect- ing rods and cylinders. The remaining six rods are, of course, articulated on the spider by pins so that the rods may move in regard to the spider when in different parts of the stroke. The shell of the pistons is of a fine grade of iron, very thin and elastic, so that it may conform readily to the outline of the cyl- inder bore. The head of the piston consists principally of the intake valve cage, the cage carrying the piston pin as well as the valve. Oil is supplied by a positive pump that measures the lubri- cant in exact proportion to the load on the engine. Both the oil and the gasoline mixture enter the crank case through the hollow crank shaft and mingle in the form of a vapor. This oil mist reaches every moving part and results in perfect lubri- cation. The pistons are provided with oil shields which carry the oil directly to the cylinder walls and prevent the loss of oil through the exhaust valve. Ignition is performed by a high tension magneto through a distributer which directs the current to the proper cylinder. As in all rotary engines, the Gyro has an uneven number of cylinders (3, 5, and 7) in order that the cylinders receive firing impulses through equal angles of rotation. An even distribu- tion of firing is impossible with an even number of cylinders, as two adjacent cylinders, out of six alternately fire together and then 180 apart. This produces a very jerky turning move- ment, and is productive of much vibration. In the seven cyl- inder motor the magneto is driven by gears having a ratio of 4 to 7, and the high tension current is distributed to the cyl- inders by 7 brushes, the leads from the brushes being taken direct to the spark plugs. (56) Gnome Rotary Motor. The Gnome was the first rotary aviation motor built in Europe and is still one of the most capable flight motors abroad as its many victories and records prove. It is built in four sizes, 50, 70, 100, and 140 horse-power, the 50 and 70 horse- power motors having 7 cylinders, and the 100 and 140 horse- GAS, OIL AND STEAM ENGINES 137 power, having 14 cylinders, which consist of two rows of 7 cylinders per row. The cylinders of all sizes rotate about a stationary crank shaft while the pistons rotate in a circle, the center of which is the crank pin. Vibration is practically elim- inated at high speed as the pistons do not reciprocate in the ordinary sense of the word, but simply revolve in a circle, the reciprocating relation between the cylinders and pistons being obtained by the difference in the centers of the two revolving Fig. 50. Cross-Section Through the Seven Cylinder Rotary Gnome Motor, Showing the Crank Shaft Arrangement and Valves. systems. The cooling effect of the radiating ribs is greatly increased by the air circulation set up' by the rotation of the cylinders. This method of cooling introduces a great loss of power due to the blower action of the cooling ribs, this loss often amounting to 15 per cent of the output of the engine. The crank shaft is stationary and acts as a support for the engine, one end being fastened into a supporting spider which forms a part of the aeroplane frame. The crank shaft is hollow and also serves to conduct the mixture from the carburetor 138 GAS, OIL AND STEAM ENGINES fastened at its outer end to the crank-case of the motor. Only one crank throw is provided on the seven cylinder engine as the cylinders are all arranged in one plane which passes through the center of the crank throw. In the fourteen cylinder engine where the cylinders are in two rows, there are two crank throws, one for each row of cylinders. The seven cylinders are arranged radially, as will be seen in Fig. 50, each being spaced at an equal distance from the crank shaft and at equal angles with one another, the arrange- ment in general being similar to that of the "Gyro" motor shown in the preceding section. All cylinders are turned Fig. 51. Firing Diagram of Seven Cylinder Rotary Motor. On Starting at Cylinder No. 1, and Following the Zig-Zag Line in the Direction of the Arrows, it Will be Seen that Ignition Occurs at Every other Cylinder at even Intervals Through Two Revolutions, Ending at Cylinder No. 1. out of solid forged steel bars, the cylinder walls being only 1.2 millimeters thick after the machining operation. This results in the strongest and lightest cylinder possible to build, as all superfluous material is removed and the chances of defects in the material are reduced to a minimum as the char- acter of the metal is revealed by the extended machining opera- tions. As the motor operates on the four stroke cycle system, an odd number of cylinders is chosen in order that the firing may be carried out through equal angles in the revolution to obtain a uniform turning movement. Since a four stroke motor must complete two revolutions before all of the cylinders have GAS, OIL AND STEAM ENGINES 139 fired, or completed their "routine of events, it is evident that the number of cylinders must be odd in order to bring the last cylinder into firing position in the last revolution. When seven cylinders are used, the cylinder are fired alternately as they pass a given fixed point, that is, one cylinder is fired, the next skipped, the third fired, and the fourth skipped, and so on around the circle, so that the firing order in terms of the cylinder numbers is 1, 3, 5, 7, 2, 4, 6. The cylinders fired in the first revolution in order are 1, 3, 5, 7, and in the second revolution, 7, 2, 4, 6, the cylinder 7 being common to both revolutions. The cylinders are numbered according to their Fig. 52. Firing Diagram of Six Cylinder Rotary Motor. On Following the Zig-Zag Line it Will be Seen that All of the Cylinders Are Not Fired at Equal Intervals. In Some Cases Two Adjacent Cylinders Fire in Sequence, and in Others Two or Three Spaces are Jumped. position on the engine, and NOT according to the firing se- quence. See Fig. 51. With a six cylinder engine it is possible to fire the cylinders in two ways, the first being in direct rotation; 1, 2, 3, 4, 5, 6 thus obtaining six impulses in the first revolution, and none in the second. The second method is to fire them alternately, 1, 3, 5, 2, 4, 6, in which case the engine will have turned through equal angles between impulses 1 and 3, and 3 and 5, but through a greater angle between 5 and 2, and even again between 2 and 4, and 4 and 6. See Fig, 52. Mixture is drawn into the cylinder by the suction of the piston through an inlet valve in the piston head, in practically 140 GAS, OIL AND STEAM ENGINES the same way as in the "Gyro" motor, but unlike the latter motor, the valve is lifted by the suction (automatic valve) and not by the mechanical actuation of the connecting rod. The inlet valve is balanced against the effects of centrifugal force by a small counter-weight in the piston head, and the valve is held normally on its seat by a flat spring acting on the valve stem. The gases are brought into the crank case from the Fig. 53. Longitudinal Section Through Gnome Rotary Motor. carburetor through the hollow crank-shaft as described else- where. See Fig. 53. All exhaust valves are located in the cylinder head and are actuated by long push rods that are moved by individual cams in an extension of the crank case. The exhaust valves are counter-balanced against centrifugal force and are retained on their seats by a flat spring. The counter weights do not entirely overcome the effects of the centrifugal force but allow a slight excess to exist which will permit the engine to run with a broken spring. All of the exhaust gases escape directly to the atmosphere without piping or mufflers. GAS, OIL AND STEAM ENGINES 141 Owing to the fact that the advancing or leading face of the cylinder is cooler than the trailing face, the cylinder bore is thrown dut of line by the difference in expansion between the two sides. Because of this distortion of the bore, a special form of piston ring is used, which, by its flexibility, adapts it- self to variations in the bore. These rings are of brass and are shaped like the pump leathers of a water pump so that the pres- sure of the explosion acting on the inside of the ring tends Fig. 54. Gnome Motor on Testing Stand. From Scientific American. to force the thin shell against the cylinder. In spite of this precaution, the compression pressure is very low at the best, in the most of cases not over 45 pounds per square inch. The exhaust valve screws into the end of the cylinder and may be removed, complete with its seat, for the frequent regrinding necessary to efficient operation. After the cylinders are ground with the greatest care and accuracy, the finishing is carried still further by wearing-in the cylinder with an actual piston carrying an "obturateur" or piston ring. The bushing into which the spark plug screws is not integral with the cylinder as in a cast construction, but is welded into 142 GAS, OIL AND STEAM ENGINES the side of the cylinder head by means of the autogenous proc- ess. It is also evident that this construction enables the inlet valves to be easily removed, since these screw into the piston head. Both inlet and exhaust valves in the Gnome engine are removed with the greatest ease, special socket wrenches being supplied for the purpose. The castor oil, which is used as a lubricant, and the gasoline, are fed by a positive acting piston pump to the hollow crank shaft. The lubricant and fuel then Fig. 55. Gnome Motor Running On Test Stand. From Scientific American. pass through the automatic inlet valve in the head of the cylinder. The spark produced by the high tension magneto is led to the proper cylinder through a brush that presses on a revolving ring of insulating material in which is imbedded 7 metallic segments, one of the segments being connected to a corresponding cylinder. As the distributor ring revolves the segments come into contact with the brush in the proper order, The magneto is stationary and is supported by a bracket in an inverted position. A pinion on the magneto shaft meshes with GAS, OIL AND STEAM ENGINES 143 a large gear mounted on the revolving crank case so that the armature of the magneto always bears a positive relation to the piston position. As the engine requires seven sparks for every two revolutions, or $ l / 2 sparks per revolution it is evident that the magneto must turn 1.75 times as fast as the engine, if the magneto is of the ordinary type that generates two sparks per revolution. In other words the magneto speed is to the en- gine speed as 7 is to 4. The "Indian" Rotary Aero Motor. The arrangement of connecting rods is interesting, the big end of one r.od being formed into a cage for the reception of the crank-pin ball race. The outer circumference of the cage carries the pins to which the other six connecting rods are fastened. It is necessary that one rod be integral with the cage to prevent its rotation in regard to the cylinders. An- nular ball bearings are used on both the main bearings, for the thrust bearing to take the thrust of the propeller, and on the large end of the master connecting rod. The large ends of the auxiliary connecting rods and the small ends of all the rods have plain bearings. CHAPTER VI TWO STROKE CYCLE ENGINES (30) The Junker Two Stroke Cycle Engine. The Junker two stroke cycle engine stands unique among the large stationary units not only in the principle of its work- ing cycle but in its construction as well, and while it may be considered freakish when compared to standard practice it has proved its value in many European installations. The combus- tion occurs in the center of an open ended cylinder between two pistons that are forced in opposite directions by the expansion of the gas, and as there is a single acting piston in each end of the cylinder at the end of the stroke, there is no need of stuffing boxes, cylinder heads or valves. It is apparent that by moving the pistons in opposite direc- tions, the effective piston velocity is twice that of the actual velocity of either of the pistons, and that it is therefore possi- ble to gain a high heat efficiency at high piston velocities with a low rate of rotation. The double pistons increase the scaveng- ing effects, reduce the losses to the cooling water and increase the efficiency at light loads. A marked reduction in weight over the four stroke cycle engine is made possible because of the absence of valves and valve gear. This engine is of the injected fuel type that is the fuel is sprayed into the combustion chamber after the completion of the compression stroke in a manner similar to the Diesel en- gine. By prolonging the injection of fuel after the piston has started on the outward working stroke it is possible to main- tain the maximum pressure due to the combustion for a con- siderable period. This gives an indicator card that is very similar to that of a steam engine as the flat top of the Junker's card due to the continued combustion and pressure corresponds to the admission line of the steam engine. As ignition is caused by the high temperature of the compression, almost any low grade oil may be used even down asphaltum oils and coal tar. In Fig. 8 five piston positions corresponding to five events are shown by the diagrams a, b, c, d, e. From the diagrams one 144 ' GAS, OIL AND STEAM ENGINES 145 may also get an idea of the arrangement of the principal parts of the engine and their relation to one another. P and P2 are the two pistons, C the open ended cylinder, G the connecting rod of the inner piston P, H-H the two connecting rods of the Fig. 8. The Junker Two Stroke Cycle Engine. piston P2, I-I the side rods of the piston P2, and V is the three throw crank shaft which is acted on by the three connecting rods H-H-G. The piston P2 is connected to the side rods through the yoke Y. It will be noted that the crank throws 146 GAS, OIL AND STEAM ENGINES controlling the piston P2 are 180 from the crank connected to piston P, which causes the pistons to move in opposite direc- tions. With the pistons together at the inner dead center, the space between them is filled with highly compressed air from the pre- vious combustion stroke. At this point the fuel is injected into the highly heated air, and the expansion of the charge begins, the combustion proceeding under constant pressure during the first part of the stroke, or during that part of the stroke in which the fuel is admitted to the cylinder. When the supply of fuel is cut off the working stroke continues by the increase of volume, or expansion of the gas, the gases being reduced to nearly atmospheric pressure at the end of the stroke with the pistons at the position shown by diagram (b). At this point the piston P. is just opening the edge of the exhaust port M, allowing the products of combustion to escape to the atmos- phere through the annular exhaust passage that surrounds the port M. As the pistons continue to move outwards the gases continue to issue from the exhaust port at practically atmospheric press- ure until the position shown by diagram (c) is reached by piston P2. At this point P2 is just opening the inlet port N allowing fresh air to enter the cylinder for the purpose of scavenging the engine. The passage of the air through the intake port N and out through the exhaust port M continues until the pistons pass the outer dead center, shown by diagram (d), and begin to come back on the return stroke. In diagram (e) the pistons have traveled far enough to close both ports, and as the space between them is filled with pure air from that furnished by the port N, the pistons will continue to move toward one an- other on the compression stroke. When they have reached the end of their travel as shown by diagram A, the fuel is injected into the cylinder and combustion occurs due to the temperature of the high compression temperature. This is the complete cycle of events made in two strokes, and it will be noted that the cycle has been accomplished with- out the use of valves. The compressed air for scavenging the cylinder is provided by air pumps that are driven from the con- necting rods by a link motion. One low pressure pump for the scavenging and one high pressure pump for spraying the fuel into the cylinder against compression are provided. Ag the inside of the piston is always exposed to the atmosphere through the open end of the cylinder and is never exposed GAS, OIL AND STEAM ENGINES 147 to the heat of combustion, perfect cooling is secured, and as a matter of course, perfect lubrication. In the two cylinder engine in which four pistons are used, the cylinders are arranged in tandem with the two adjacent pistons, and the two outer pistons connected respectively. In fact the second cylinder pistons are duplicates of those just shown and are connected to the linkage in such a manner a-s to have the corresponding pistons in one cylinder act with the corresponding pistons in the second. (34) Koerting Two Stroke Cycle Engine. One of the most prominent of the two stroke cycle scaveng- ing engines built for heavy stationary service is the Koerting engine. Because of its peculiar scavenging arrangement, and F-ll. Koerting Two Stroke Cycle Engine with Scavenging and Charging Cylinders. as it is of the double acting type, it will serve to illustrate the cycle of that class of engine equipped with independent air pumps. Several of these engines are in use in Europe that have an output of over 4,000 horse-power, the general arrange- ment of which is the same as shown in the accompanying dia- gram Fig. F-ll. Since the engine is double acting, two similar combustion chambers are provided at each end of the piston as shown by C and Ci, and as each of the chambers gives one impulse per revolution because of the two stroke cycle, the single cylinder shown in the figure delivers two impulses per revolution to the crank-shaft. In order to have one exhaust port serve for both combustion chambers, the annular port E is placed in the cen- ter of the cylinder so that it is alternately opened to C and then Ci as the piston travels to and fro, the port being covered by 148 GAS, OIL AND STEAM ENGINES the piston at intermediate points in its travel. As the piston must cover the port for a considerable portion of the stroke, it is made very long, nearly as long as the stroke. The piston rod R that connects the piston with the crank passes through the cylinder head of chamber C u surrounded by a gas tight packing that prevents the leakage of the charge from Ci. Unlike the ordinary type of two stroke cycle engine, the two combustion chambers are provided with mechanically operated inlet valves, V-Vj-Va-Vs that are opened at definite points in the stroke by the lay shaft X which is driven from the crank shaft. As the exhaust port E serves all of the functions of an exhaust valve, there are no valves provided at this point. Ex- haust pipes connected to E carry the burnt gases to the atmos- phere. Two auxiliary air pumps of the double acting type are pro- vided, shown at A and A,, one pumping gas and the other air. They are driven from the crank-shaft through the connecting rod Y, and are proportioned so that together they force a mix- ture of the correct proportion for complete combustion into the working cylinder at a pressure of about ten pounds per square inch. Air and gas are compressed on one side of each pump piston in the spaces B and B 2 , and the air and gas are drawn in on the other side as at H and H 2 . The connections from the compressor cylinders to the working cylinder are arranged so that the two crank ends of the compressor C3^1inders discharge into the crank end of the working cylinder, and the front ends of the compressors discharge into the front end of the working cylinder, the exact moment of discharge being controlled by the inlet valves V-Vi-V,-V 3 . The pumps are arranged so that only pure air is admitted at first in order to force the products of combustion through the exhaust port so that they will not contaminate the following mixture of air and gas. The inlet valve opens immediately after the piston of the working cylinder uncovers the port E and reduces the pressure of the burnt gases to that of the atmosphere. By the action of the admission control, the scavenging air first admitted, is prevented from mixing with the residual gas from the previous explosion, and in the same way the device prevents the loss of fuel through the exhaust ports, thus over- coming the principal objections of the simple two stroke types described earlier in this chapter. The compressor cylinders pro- vide only enough air and mixture for one stroke and no reser- voir is provided for a surplus of air or mixture. GAS, OIL AND STEAM ENGINES 149 As the piston moves forward, on the compression stroke and covers the exhaust port, the inlet valves also close, and the compressor pistons arrive at the end of their stroke so that no more air or mixture is delivered to the inlet valves. At the end of the compression stroke ignition occurs and the ex- pansion or working stroke begins. The piston again moves to the right on the working stroke until the front edge uncovers the port E where the exhaust gases escape to the atmosphere. The valve gear on the gas compressing cylinder is arranged so that no gas is delivered to the inlet valves of the working cylinder until the air cylinder has provided sufficient air to in- sure perfect scavenging of the products of combustion, this pre- venting the fuel from becoming contaminated with the burnt gas. Speed regulation for varying loads is effected by shifting the valve gear of the gas pump so that the gas is delivered at an earlier or later period in the stroke of the working piston, thus causing a variation in the quantity of gas delivered to the work- ing cylinder. This is controlled by the governor directly on the valve gear of the pump or upon a by-pass in the pump cylinder or both. The by-pass, when open returns all of the gas in the passage leading to the inlet valve, that is beyond a certain pressure to the cylinder, so that the gas is delivered to the cylinder at a constant pressure, and therefore in propor- tion to the load and point of cut off. This method of governing produces a mixture that varies in richness with the different loads that are carried by the engine, but as the air enters the cylinder first and is prevented from mixing to any extent with the gas by the shape of the cylinder heads, the igniting value of the mixture is not disturbed par- ticularly as the rich gas remains in the cylinder heads and in contact with the igniters. Like all large engines, the Koerting is started by compressed air taken from a reservoir. A special starting valve is provided for each end of the cylinder which is operated from the cam shaft by means of an eccentric. The air valves may be thrown in or out of gear by a clutch. (57) Two Stroke Cycle Rail Motor Cars. A unique application of the two stroke cycle motor will be seen in Fig. 56 which shows a Fairbanks-Morse two stroke cycle motor direct connected to the driving wheel of a railway motor car. The three cylinders are mounted between the driving wheel with the ends of the axle terminating in the 150 GAS, OIL AND STEAM ENGINES crank cases of the motors. Access to the bearings is had through a cover on the crank-case. The simplicity of this motor and its freedom from valves, cams, springs, gears, and other trouble causing parts makes it particularly adapted for the service that it performs in the hands of unskilled track laborers. As there is no water to freeze or leak, and as the lubricant is mixed with gasoline, the car needs very little more attention than the old type hand car. The car is started by opening the gasoline supply cock, clos- ing the ignition switch, and pushing the car along the track until the first explosion occurs. The speed is controlled in the usual manner by means of the spark advance and throttle. As the motor is of the two stroke cycle type, it may be reversed Fig. 56. Two Stroke Cycle Fairbanks Motor for Driving Railway Section Cars. by simply changing the position of the timer without the use of the gears. The speed is the same in either direction. By the use of three cylinders; three impulses are obtained per revo- lution which gives a distribution of power equal to that of the ordinary six cylinder, four stroke cycle automobile motor. For larger cars built for carrying large gangs of men, a three cylinder motor is used which drives through a clutch and gears, similar to that used on automobiles. It is located near the center of the axle and is supported on a frame that is independ- ent of the car proper. This motor unit is easily removed from the car for inspection with all of the parts intact. A universal coupling is provided on the motor shaft to prevent strains due to changes in the alignment from being thrown into the motor. The motor of this car is started with a crank,' and may be left standing with the motor running. As .with the two cylinder car, the engine is reversible, and is lubricated by mixing the lubricating oil with the gasoline. GAS, OIL AND STEAM ENGINES 151 (58) Rotating Cylinder Two Stroke Cycle Motor. An unusual type of two stroke cycle engine is that designed by M. Farcot for aeronautic work. It is of the rotating cyl- inder type in which the cylinders rotate about a stationary Fig. 63. Farcot Rotary Two Stroke Motor. crankshaft, and unlike all previous two stroke motors, whether of the revolving or stationary cylinder type, no initial compres- sion is performed either in the crank-case or otherwise. 152 GAS, OIL AND STEAM ENGINES Undoubtedly the two-cycle rotating multi-cylinder engine has a future when some of the particularly difficult designing prob- lems involved in its production have been successfully tackled. Crank case compression has had its devotees, but so far it has entailed the use of a low compression, owing largely to the difficulties involved in lubricating the bearings and maintain- ing gas-tight joints, besides other defects. Some of these bar- riers appear to have been surmounted in this design. Fig. 63 of the accompanying drawings is a sectional side ele- vation of the engine, which, it will be seen, is similar in gen- eral disposition to the usual arrangement of the rotating cyl- inder type. In this particular case, however, the short end A of the stationary crankshaft is reduced in diameter at B, and on this part are mounted ball bearings C carrying the circular casing of a rotating centrifugal blower D. To the inner end of the hub of this blower is attached a gear wheel E, the teeth Fig. 64. Farcot Fan Plates. of which mesh with small intermediate pinions carried on a spider F attached to the crankshaft. These pinions are in turn driven by an internally toothed ring G attached to the hub of the crank case H. Thus the blower D is driven in the opposite direction to the crank-case and at a higher speed. In the interior of the blower casing radial blades K are provided. A hollow annular casing L is bolted to the cylinders, and communicates with their interiors by means of inlet ports M covered and uncovered by the pistons. The blower casing D has on either side circumferentially flanged rings N, which are a running fit in circular register slots provided in the annular casing L and its cover plate P, in order to provide a gas-tight joint between the opposite re- volving casings D and L. Fan blades Q are also provided in the casing L to accelerate still further the incoming gas. The arrangement of the two sets of blades is made clear in the sectional sketch (Fig. 64). It will be realized that by means of this compound blower device a considerable pressure can be attained. The crankshaft is drilled to provide a feed for the gasoline, GAS, OIL AND STEAM ENGINES 153 which is atomized by a device R in the large central opening of the blower casing D by means of pressure fed from the annular casing L through suitable leads S. As each piston nears the bottom of its stroke, exhaust ports T, provided with expansion cones for the purpose of increasing the velocity of the exhaust gases, are opened. The inlet port M is then uncovered, and the compressed charge rushes into the combustion chamber. The general design of the engine is made plain by Fig. 63, but there is one other point to which reference should be made, and that is the provision of rings V, one on either side of the cylinders, to enhance the strength of the construction. Although the difficulty of compression appears to have been cleverly tackled in this invention, the possibility of the com- pressed mixture in the inlet casing and blower becoming ignited at the moment of admission by a residue of exhaust gas in the combustion chamber still exists. However, the effect of such a backfire should not prove quite so serious as in some de- signs. Apart from other considerations, owing to the large area of the blower intake, such an occurrence should merely have a more or less elastic braking effect. (60) Gnome Radial Two Stroke Motor. The builders of the famous Gnome four stroke cycle rotary motor, Sequin Freres, have recently developed a radial two stroke cycle motor that bids fair to supplant their original type. Referring to the diagramatic cross-sections which show only a single cylinder unit, a very long tubular piston will be seen that is divided into two independent chambers, A and B. Both chambers are placed in communication with the outside space, C and D. The upper end of the piston is continued above the top divi- sion head of the chamber A, and the extension is provided with the slot F. Near the center of the piston, the walls of the piston are run out into a flat circular plate or trunk piston E, which is the actual piston head that receives the force of the explosion. The piston E reciprocates in the large cylinder H, which is reduced at its upper end to the diameter of the main piston barrel, for which it affords a sliding support, or guide, and also serves to aid the exhaust port closure. The lower end of the cylinder H is enlarged in diameter as shown by K so that a clear annular space is left between the cylinder walls and the piston head E, when the latter is at the bottom of the 154 GAS, OIL AND STEAM ENGINES stroke. The cylinder diameter is then reduced to the diameter of the main piston barrel. The motor operates as follows: Suppose the piston to be ascending (Fig. 1), compressing the mixture above the piston head in the cylinder E, and at the same time the volume of the space M, below E, is being in- creased until the piston reaches the position shown in Fig. 2. Referring to Fig. 1; the interior chamber A of the piston is in direct communication through the holes C with the space Fig. 65. Gnome Rotary Two Stroke Motor Diagram. Diagrams 1 and 2. M, consequently as the piston goes up, a partial vacuum will be formed in these two chambers. When the piston reaches the top of its stroke as shown in Fig. 2, the holes D in the lower end B of the piston are uncovered as they rise into the in- creased diameter of the cylinder, and therefore the mixture is sucked in from the crank case until the chambers A and M are filled to atmospheric pressure. The spark now occurs at the plug S, and the explosion takes place, driving the piston downwards as shown by Fig. 3, just GAS, OIL AND STEAM ENGINES 155 before the exhaust takes place. The volume of the chamber M has now been decreased with the result that the mixture will have been compressed into the chamber A. In Fig. 4, the piston has now reached the bottom of the stroke, and the ports F have opened as the slots carry below the upp'er end of the cylinder where the bore is increased. At the same time, as the piston plate E passes the bottom of the cylinder H into the enlarged diameter K, the compressed mix- ture in A and M rushes through the annular space opened Gnome Rotary, Diagrams 3 and 4. around E into the combustion chamber and drives out the residual burned gases which still remain after the explosion. On starting the second revolution the piston rises and the cycle repeats as shown by Fig. 1. This engine may be built with any number of the cylinder units described, preferably with an uneven number, as in the case of the Gnome radial four stroke cycle, and with twice the number of impulses of the four stroke type a very uniform turning movement should be had. 156 GAS, OIL AND STEAM ENGINES m m m mm mm m Fig. 64-b. Roberts Two Stroke Aero Motor Using a Rotating Tubular Valve that Controls the Mixture from the Carburetor so that it Enters Only One Crank Case at a Time. This Gives Each Cylinder an Equal Charge of Gas. Fig. 64-c. Roberts Distributor Valve. The Ports Are Cut in the Valve so that Only One Crank Case is in Communication with the Car- buretor at Any One Time. The Central Hole Connects with the Carburetor. GAS, OIL AND STEAM ENGINES 157 Since the valves are the parts that give the most trouble in the four-stroke cycle Gnome, this motor should be better adapted for aviation than the original type of Gnome. (62) Variable Speed Two Stroke Motor. A variable speed two stroke cycle motor is described by C. Francis Jenkins in the Scientific American that seems to Fig. 66. Jenkins Two Stroke Cycle Motor. solve many of the problems encountered in designing a two stroke cycle motor for automobile purposes. As is well known, the present design of the crank-case compression type is waste- ful of fuel, and ignites irregularly at low speeds and light run- ning, and as nearly all automobiles are well throttled for a greater portion of the time it means that this type of motor is working under the greatest disadvantage. Since the greater part of the trouble is due to the dilution of charge by the residual gases, and as the spark plug of the 158 GAS, OIL AND STEAM ENGINES motor is situated in the most diluted portion of the gas, it would seem that a change of spark plug location, or a change in the circulation of the fresh mixture in the cylinder would be a great aid in remedying the difficulty. With the spark con- tinually in contact with fresh undiluted mixture it would be possible to run it as low speeds as with the four stroke motor, with a corresponding increase in the efficiency, and opportunity to run with a constant advance of the point of ignition. This is accomplished by any or all of the following conditions: (1.) By keeping good gas separate from bad. (2.) By placing the spark near the intake port. (3.) By leaving the plug in its present position and deflect- ing the fresh gas to meet it. (4.) By changing the location of the inlet port. Fig. 58-a. Two Cylinder Marine Engine, of the Two Stroke Type. Built By Fairbanks-Morse and Company. In the motor invented and described by Mr. Jenkins, the method given by (4) is adopted as shown by Fig. 66, in which the spark plug is placed at the point of admission of the gas and in a confined passage. The operation of the motor is as follows: Carbureted gas is drawn into crank-case from the carburetor (not shown) in the usual manner, i. e., by the upward move- ment of the piston; and by its downward movement is forced through the rectangular port in the wall of the piston into the combustion passage within the water-jacket when the port in GAS, OIL AND STEAM ENGINES 159 the piston wall registers with the lower end of this combustion passage, and drives ahead of it the bad gas remaining after the previous explosion. If the throttle is wide open the combus- tion space above the piston will be completely filled, and on the ignition of the charge the maximum pressure will be exerted on the piston. If, however, the throttle is but slightly open, the combustion passage only may be filled and none overflow into the combustion space above the piston. This small charge will be just as efficient in proportion to its volume as was the large charge, for it was compressed to practically the same extent and Fig. 64-d. Rpberts Cylinder Showing Cellular Screen in the Intake Port. This Screen Prevents Crank Case Fires by Chilling the Cyl- inder Flame Before it Enters the Crank Case. none was mixed with the bad gas of the previous explosion. It will, therefore, be obvious that the spark-plug is always swept by the fresh charge, be it large or small, and the ignition will be just as certain in one case as in the other, although the charge and consequent impulse may be only just sufficient to keep the engine turning over, and without missing a single explosion. In the motor built to test and demonstrate this design, provision was made for a second spark-plug to be located in the top of the cylinder for speed work, if this was found nec- essary. No opportunity has yet been had for making track tests, though without regret, as this two-cycle motor will run idle without missing or "stuttering," which was the thing here- tofore impossible. CHAPTER VII OIL ENGINES (31) Diesel Oil Engine. The Diesel engine marks the greatest progress in the internal combustion field made in the last few years. It marks a dis- tinct advance in both thermal efficiency, and in the character of the fuel that it has made a commercial possibility. By the use of cheap fuel heretofore unavailable for any type of prime mover, such as the asphaltum residual oils, coal tar, etc., it has lowered the cost of power production to a point where it is unapproached by any type of heat engine. Besides its thermal efficiency, the engine is free from the annoyances due to delicacy of the auxiliary appliances such as the carburetor, and ignition system which are indispensable with the ordinary type of gaso- line engine. This engine belongs to that type of engine in which combus- tion takes place at constant pressure (Brayton Cycle), that is the combustion pressure is maintained at a constant value for a considerable distance on the working stroke of the piston. This method differs from the Otto cycle in which the combus- tion proceeds at a constant volume, or the type in which com- bustion is completed before the piston moves forward on the working stroke. In the Diesel cycle the first stroke of the piston draws pure air into the cylinder; the piston then moves forward on the compression stroke, compressing the air to 500 or 600 pounds per square inch and raising the temperature of the air to about 1,000 degrees C, the exact temperature and pressure depending on the character of the fuel used in the engine. The high pressure is obtained by using a small clearance space in the end of the cylinder. At the end of the compression stroke a spray of oil is injected into the cylinder which is instantly ignited by the high temperature of the compressed air. The oil continues to burn as long as it is sprayed into the cylinder, this period being from one-quarter to one-third of the working stroke. After the oil is cut off, the hot gas is ex- 160 GAS, OIL AND STEAM ENGINES 161 panded to the end of the stroke at which point the pressure is very considerably reduced due to the mechanical work per- formed. It should be noted that the type of engine just de- scribed performs the complete cycle in four strokes, the fourth stroke being the scavenging stroke as in the ordinary four stroke cycle engine. While the four stroke cycle type of Diesel engine is by far the most common type, it is also built as a two stroke cycle that is similar to the two stroke cycle gas engine previously described except that pure air is received and com- pressed in the air compressor in place of the combustible mix- ture. It will be noted, that as there is no fuel in the cylinder dur- ing the compression stroke that there is no danger from pre- ignition from an over heated charge, nor is there trouble from Fig. 9. Cross Section of Four Stroke Cycle Diesel Engine. The Center Valve is the Fuel Admission Valve. decomposed fuels due to a gradually increasing temperature so often met with in oil engines that compress the entire mixture. As the clearance space is exceptionally small there is a minimum of residual gas held in the cylinder after the explosion with the result that the fuel is completely consumed, and that a full charge is taken 'into the cylinder. The speed and output are regulated by controlling the point in the working stroke at which the oil spray is cut off, and as this has no effect on the maximum pressure developed in the cylinder, as in the case of the ordinary gas engine control, the pressure charge under varying loads is not so severe. Be- cause of the high compression, and the continued combustion, there is a very gradual increase of pressure. Since the amount of pure air admitted to the cylinder is the same at no load as at full load there is always sufficient air for the complete com- bustion of the fuel, and as there is a constant compression 162 GAS, OIL AND STEAM ENGINES pressure there is a constant ignition temperature and constant quantity -of the working medium. Because of the high com- pression obtained by the Diesel type, it has an efficiency that is far beyond that of any other form of internal combustion motor. Fuel Nozzle of the Koerting Diesel Engine Showing Operating Cam and Lever, and Compressed Air Connection. Since the fuel is introduced gradually into the combustion chamber the combustion pressure rises very slowly so that it is not an explosive engine in any sense of the word, the com- bustion pressure rising steadily from the compression pressure to the maximum in porportion to the supply of fuel. In the ordinary type of gas engine with- a compression pressure of from 60 to 70 pounds per square inch the pressure rises abruptly to about three and one-half times the compression pressure, GAS, OIL AND STEAM ENGINES 163 with a correspondingly rapid drop in the pressure on the ex- pansion stroke. In the Diesel engine the drop of pressure in expansion is much more gradual, the indicator diagram expan- sion curve being nearly horizontal. The uniform pressures thus obtained result in smooth action and even driving power, ob- tained with no other type of engine. Fuel Pump of Koerting Diesel Engine with Operating Cam. As the fuels used vary from the lightest hydrocarbons to the heaviest crude oils, there are many types of oil injection valves in use, the valves being in general divided into two classes, those in which the oil is vaporized mechanically by the pres- sure of a force pump, and those in which the fuel is vaporized by the atomizing effect of compressed air. Atomization by com- pressed air is however, the most common method since less trouble is experienced with the air pumps than with the liquid force pumps. The compressed air is supplied by pumps that 164 GAS, OIL AND STEAM ENGINES are either operated by the main engine or by an independent compressor engine. The fuel valve is a plug screwed into the cylinder containing an inwardly opening check valve in the inward end. The hole in the center of the plug receives the oil charge under a few pounds pressure from the tanks, during the compression stroke of the engine, and at the end of the compression stroke, a blast of air at a pressure of about 250 pounds above the com- pression pressure blows it into the cylinder in the form of a fine spray. Injection valves of the forced feed type consist of a plug with a small passage and a needle valve for regulating the spray. Fuel is pumped into the valve at about 250 -pounds above the compression pressure of the engine by a small single acting pump which is built so that the length of the stroke may be adjusted to meet the load. In practice the length of stroke is regulated by the governor, so that the full contents of the pump are delivered at full load, and a reduced amount with a short stroke at small loads. On issuing. from the fuel nozzle, the liquid strikes a gauze screen by which it is broken up into very fine spray. Fluidity is practically the only factor that governs the quality of fuel that may be used with the engine, since exceptionally heavy oils and tars cannot be successfully sprayed. In Fig. 9 is shown a cross-section of a Diesel engine cylinder in which the center valve in the cylinder head is the fuel valve, and the valves to the right and left are the air inlet and exhaust valves respectively. The two latter valves correspond to the inlet and exhaust valves of the Otto cycle engine. Compressed air is used in starting the engine, which is ad- mitted to the cylinder through an auxiliary valve which is oper- ated by a starting cam on the cam shaft. By this mechanism, high pressure air is furnished to the cylinder during a portion of the working stroke, turning it over on the first few revolu- tions as a common air engine. As soon as the engine picks up speed, the starting valves are thrown out of operation, and the engine proceeds on its regular working cycle with the oil fuel. When used for marine purposes in sizes over 100 horse-power, where it is not possible to use reverse gears, the Diesel engine whether of the two stroke cycle or four stroke cycle type must be made reversible. This may be accomplished by either of two methods, first, by changing the angular position of the cams in regard to the piston position, and second by using two GAS, OIL AND STEAM ENGINES 165 sets of cams, one being for right hand rotation and the other for left hand. When a single cam is used, the relation of the cam shaft on which the oil pump cams and oil valve cams are located, is advanced or retarded in" respect to the crank shaft by means of sliding the two spiral gears that drive the cam shaft, over one another, in a direction parallel to their axes. The spiral gears are moved back and forth by a hand controlled reverse lever. This type is used principally on the two stroke cycle type of engine as there are not so many factors to con- tend with as on the four stroke cycle. With double cams, the system almost invariably used with the four stroke cycle engine, the cams may be mounted either on one shaft, or the ahead cams on one cam shaft and the reverse cams on another. When two shafts are used they are arranged so that either set of cams may be swung under the valve lifters by swinging the shafts in a radial direction by brackets. The single type of cam shaft is usually moved back and forth in a direction parallel to its axis, the ahead cams coming under the valve lifts at one position, and the reverse cams at the other. In the four stroke cycle Diesel it is evident that not only the relations of the oil pump and oil valves must be changed in respect to the piston position but the relations of the air inlet and exhaust valves must be changed as well. This necessitates double cams for the inlet and exhaust valves in order to reverse rotation. Compressed air for starting and injection is generally supplied by a three stage air compressor or a compressor in which the pressure is built up in three different steps, the second cylinder taking the air from the discharge of the first, and the third cylinder taking the air from the second," and compressing it to about 250 pounds above 'the compression pressure of the en- gine. Perfect scavenging is possible with this engine because of the large excess of air supplied during the suction stroke and the period of injection. On the marine type the air pumps and water circulating pumps occupy about the same amount of space as the condenser and circulating pumps of a steam engine having the same outputs. In a recent test made with an Atlas- Diesel engine it was found that 11 per cent of the output was lost in driving the air pumps or more than 50 per cent of the total loss by friction and inipact. Unlike the ordinary gasoline engine in which an increase of speed increases the output in an almost direct proportion, the output of the Diesel engine decreases when the speed rises Fig. 67. Cross-Section Through the Working Cylinders of the M. S. Monte Penado Two Stroke Cycle Diesel Engine. From the Motor Ship, London. GAS, OIL AND STEAM ENGINES ' 167 beyond a certain limit due to imperfect combustion at speeds much over 350 revolutions per minute. Because of this fact it has been practically impossible to apply the type to automobile service which ordinarily requires a speed of from 400 to 800 revolutions per minute under ordinary conditions. In addi- tion to the speed limitations, the Diesel engine weighs approxi- mately 70 pounds per horse-power against an average weight of 17 pounds per horse-power with the ordinary type of gasoline automobile motor. Of course these objections may be over- come in time, as the engine is only in its infancy, and the two stroke cycle Diesel has not yet been fully developed, but at the present time it does not seem probable that this engine will ever be an active competitor of the gasoline automobile motor, at least from the standpoint of flexibility. As the Diesel engine depends entirely upon compression for its operation, it is necessary that all of the parts such as the pistons, valves, etc., shall be perfectly fitted and air tight under extremely high pressures. The careful workmanship required for such fitting and the adjustments make the Diesel much more expensive to build than the ordinary type of gas engine, and for this reason the first cost and overhead charges cut into the fuel item to a considerable extent. A description of the Diesel engines will be found in the chapter devoted to oil engines. (63) Diesel Engine (Marine Type). As a practical example of a Diesel engine, which was de- scribed in Chapter III, we will give a brief description of the two 850 horse-power Diesel engines installed in the cargo vessel "M. S. Monte Penedo," which were built by Sulzer Brothers of Wintherthur, Switzerland. We are indebted to the Motor Ship, London, for the details. The engines are of the two stroke cycle, single acting type, with four working cylinders, a double acting scavenging pump cylinder, and a three stage ignition compressor cylinder. The bore of the working cylinders is 18.8 inches, and the stroke 27 inches. While the crank case is of the enclosed type, there are two sets of covers which can be easily removed for in- spection while the engine is running, for as the scavenging pump performs the work of the crank case of the ordinary two stroke cycle engine there is no need of a tight case to retain the compression. The scavenging pump is mounted on one end of the engine 168 GAS, OIL AND STEAM ENGINES e Fig. G8. Cross-Section Through the Air Cylinders of the Two Stroke Diesel Motors on the M. S. Monte Penado. GAS, OIL AND STEAM ENGINES 169 and is driven from the crank-shaft, the cross-head of the pump forming one piece with the piston of the low pressure cylinder of the injection air cylinder. All of the compressor stages are water cooled and fitted with automatic valves. The double act- ing scavenging pump has a piston valve driven by a link mo- tion for reversing it when the engine is reversed. The air enters the pump through the top valve chamber from a pipe leading into the engine room. The air discharges a pressure of about 3 pounds per square inch in a header that passes in front of all four working cylinders. By means of a valve the air entering the low pressure stage of the compressor can be taken either from the atmosphere or from the discharge of the scavenging pump; taking the air from the latter allows of a greater weight of air taken by the compressor and consequently a higher compression for use in emergencies. As in the ordinary type of two stroke cycle engine, two in- dependent sets of exhaust ports are used, one set being for the scavenging air and the other for the exhaust gases, both sets being at the end of the stroke as usual. The air inlet ports are divided into two groups, however, one group being controlled by the piston of the working cylinder, and the other group by an independent piston valve driven from the cam-shaft. Both sets of ports connect with the main scavenging air header. By means of the valve controlled ports it is possible to admit scavenging air even after the other ports are closed by the piston, which greatly increases the scavenging effect. With the air at 3 pounds pressure the air from the valve controlled ports throw the scavenging air to the top of the cylinder even after the exhaust ports are closed. This valve is provided with a reverse mechanism. A single cam is used for operating the fuel inlet valve and the air starting valve, and the reversal of the engine is obtained by turning the cam shaft through a small angle relative to the crank-shaft, which of course also reverses the lead of the fuel valve. Starting is accomplished by com- pressed air, with the air valve lever on the cam, and the fuel valve lever off. After turning through a few revolutions, the air valve levers are raised, and the fuel levers dropped back on the cams which results in the engine taking up its regular cycle, By moving the tappet rod of the fuel valve out of or into a vertical position, the time of the fuel valve opening is reg- ulated and the amount of air is controlled. This movement is normally performed by a compressed air motor, but in an emer- gency hand wheels mey be used. 170 GAS, OIL AND STEAM ENGINES One of these serves to rotate the camshaft through the re- quired angle in order to set the cams in the positions for astern or ahead running and also reverses the link motion of the scavenging pump valve by the rotation of shaft, as mentioned above. The other auxiliary motor operates the fuel and starting air valves by moving the small spindle longitudinally to bring the tappet lever of the air valve about the required cam for ahead or reverse and also lifts this or the fuel valve tappet rod off its cam, according as it is desired to run on fuel or air. The spindle on which the valve levers are pivoted is in two parts, divided at the center. This is to allow two of the cyl- inders to run on air whilst the other two are running on fuel, and, as can be seen from the dial where the pointer indicates the position, in starting up, whether astern or ahead, first two cylinders are put on air, then four on air, next two on air and two on fuel, and finally all four on fuel. This allows very rapid attainment of full speed. The amount of fuel entering each cylinder can be regulated separately by small hand wheels. Below the fuel pumps are arranged three auxiliary pumps, two of these being oil pumps for the oil circulation, whilst the other is of the piston cooling water. On the left of the en- gine and driven in a similar manner from the cross-head by links are three other pumps, one for the circulating water and the other for the general water supply of the ship. Lubrication for the cylinders is furnished by 8 small pumps, just above the water pumps, two oil pumps being provided for each cylinder. As the supply pipe is divided into two parts, the oil reaches the cylinder at four points in its circumference. Four oil pumps are provided for the air compressor. Four steel columns are provided for the support of each cyl- inder in addition to the cast iron frame of the base, and by this means the explosion stresses are transmitted directly to the bed plate. The cast iron columns provide guide surfaces for the cross-head shoes. The guides are all water cooled. (64) The M.A.N. Diesel Engine. The Maschinenfabrik Augsburg-Niirnburg, G. A., a German firm have built some remarkably large Diesel engines both of the vertical and horizontal types. The peculiar merits of the horizontal type of Diesel engine of which the M.A.N. company are pioneers are still open to discussion at present, but there is no doubt but what this type will be the ultimate form of GAS, OIL AND STEAM ENGINES 171 vary large engines when certain alterations are made in the design. In Fig. 69 is shown a 2,000 brake-horse-power horizontal M.A.N. Diesel engine of the four stroke cycle type which is installed at the Halle Municipal Electricity Works, Halle, Ger- Fig. 69. Horizontal M. A. N. Diesel Engine at the Halle Municipal Plant. Fig. 70. High Speed Mirlees-Diesel Engine. many. It is of the double acting type with twin-tandem cyl- inders giving four working impulses per revolution. This en- gine was installed in addition to the six producer gas engines already in place to take the peak load of the station at different times during the day, the gas engines meeting the normal, steady demand. 172 GAS, OIL AND STEAM ENGINES This firm has built many thousands of the vertical type of Diesel engine of all sizes, and has recently installed 13 engines of 4,500 brake horse-power for operating the Kreff tramways. The company is now building cylinders giving outputs of from 1,200 to 1,500 brake horse-power per cylinder, giving outputs of from 5,000 to 6,000 horse-power in tandem twin type engines. As will be seen from the cut, the horizontal Diesel engine is remarkably free from complicated valve gear. (65) Mirlees-Diesel Engines. The Mirlees-Diesel engine is built by the English firm, Mir- lees, Bickerton and Day both for stationary and marine service. Fig. 71. Mirlees-Diesels at Dundalk. A generating plant consisting of two, 200 horse-power Mirlees engines direct co'nnected to Siemens generators has been in- stalled in the municipal plant at Dundalk as shown by Fig. 71. On test these units consumed 0.647 pounds of oil per horse- power at full load and 0.704 pounds per horse-power at half load with a regulation of 3.24 per cent from full load to no load. All of the engines built by this firm are of the four stroke cycle type. (66) Willans-Diesel Engines. The Willans-Diesel engines built by the Willans and Robinson Company of Rugby, England, are in sizes up to 400 brake horse- GAS, OIL AND STEAM ENGINES 173 power, and run at speeds up to 250 revolutions per minute. They are all of the four stroke cycle type and are applied prin- cipally to the driving of electric generators. The cut shows one of the four, 280 horse-power units supplied to the Alranza Company and the Rosario Nitrate Works in South America. Unlike the Mirlees engine, the Willans has an individual frame for each cylinder as in steam engine practice. Like the steam engine frame, the bottom is left open for the inspection of the connecting rod ends and the main bearings which is a most desirable feature. The air compressor and pumps are arranged in a most compact form at the left end of the crank- Fig. 72. Willans Vertical Diesel Engine. shaft from which the pipes may be seen issuing to the four cyl- inders. The valves and over head gear are of the conventional type, which, with the exception of a few minor details are the same as those on the recently developed Sulzer-Diesel. The individual grouping of the cylinder units has many desirable features and should, we believe, be more extensively copied. (67) Installation and Consumption of Diesel Plant. An English gas-electric station was completed at Egham, England, that is a good example of the changes that have been made recently in the electricity supply abroad, with Diesel power. 174 GAS, OIL AND STEAM ENGINES The generating plant comprises two 94 K. W. Diesel en- gines built by Mirrless, Bickerton and Day, direct connected to single phase alternators generating at 2,000 volts. The exciters are direct connected to the main shaft, and the plant is capable of generating an overload of 10 per cent for two hours. Space has been left for the installation of two more units of a larger size. The following fuel consumption was guaranteed for a load of unity power factor, and the official tests show slightly bet- ter figures than the guarantee. Full load 0.68 Ib. oil per K. W. H. Three-quarter load 0.72 Ib. oil per K. W. H. Half load 0.79 Ib. oil per K. W. H. Quarter load 1.15 Ib. oil per K. W. H. Cross-Section Through Egham, England Municipal Plant. Particular attention has been given to the water supply for the jackets of the engines; the circulation being by two elec- trically driven, direct connected centrifugal pumps, one of which is a spare. A Little Company's cooler has been installed, which consists of a horizontal cylindrical chamber, the lower part of which contains water. In the tank are arranged a number of concentric metal cylinders spaced about ^-inch apart, and in several sections, that are carried on a slowly revolving shaft, driven from the fan shaft. The cylinders are all of the same length, and are open at both ends. The lower half of the cylinders dips into the water in the casing, and as they revolve, a thin film of water on each side of the plate is carried into the upper portion of the casing where it meets a blast of cold air from the fan. The fan is driven from the circulating pumps, and passes the air through GAS, OIL AND STEAM ENGINES 175 the chamber in a direction opposite to that of the water, baffles being placed so that correct circulation is maintained. The small loss is made up by connecting the ball cock in the tanks with another tank charged from the works well by means of a self-starting rotary pump, electrically driven. Very little power is required for the pumps and cooler. Fuel oil is stored in a tank outside the building, the oil being supplied to the tanks from an oil wagon by means of a small hand pump. Oil is taken from the tanks and forced into the engine room by a rotary pump, from which it enters two graduated tanks located in the roof of the station. The graduations on the tanks allow the consumption of oil to be carefully recorded by alternately filling and emptying the two auxiliary fuel tanks. The entire building is electrically heated, and the kitchen of the flat above the station is equipped with an electric cook- ing-stove for the use of one of the engineers who make it his residence. DIESEL HORSE-POWER FORMULA P. A. Holliday, in the Engineer, derives a new formula for computing the horse-power of the four stroke cycle, single- acting engine. For each horse-power developed by these en- gines about 21,000 cubic inches of displacement is necessary, per minute. D = Cylinder bore in inches. S = Stroke in inches. M.P.S. = Mean piston speed in feet per minute. R = Ration of stroke to bore. N = Revolutions per minute, then V B.H.P. X 222.0 D = M.P.S. 6 M.P.S. Knowing the value of D, N S For high speed, low ratio (R), four stroke cycle engines, approximately 22,000 cubic inches displacement per minute is required. V 2,330 B.H.P. D = M.P.S. In both formulae, the air compressor for fuel injection is Included. 176 GAS, OIL AND STEAM ENGINES (32) Semi-Diesel Type Engine. In the "Semi-Diesel" Type Engine the oil is injected into the cylinder at the point of greatest compression in the same manner as in the Diesel engine, and like the Diesel it compresses only pure air. In regard to the compression pressure, however, it stands midway between the pressure of the Diesel engine and that of the ordinary "aspirating" type oil engine, as the com- pression averages about 150 pounds per square inch. While this is a much higher pressure than that carried by the ordinary kerosene engine which compresses a mixture of kerosene vapor and air, it is not sufficiently high to ignite the oil spray by the increase in temperature due to the compression, but ignites the charge by means of a red hot bulb or plate placed in the com- bustion chamber. This type of engine is built both in the two stroke and four stroke cycle types, the events occurring in the same order as in the two stroke and four stroke Diesel types, that is, pure air is drawn into the cylinder on the suction stroke (four stroke cycle) or is forced in at the beginning of the compression stroke (two stroke cycle), and is compressed in the combustion cham- ber. At the end of the compression stroke, the fuel is injected against the red hot bulb or plate by which the charge is ignited. Expansion follows on the working stroke after the fuel is cut off, and release occurs at the end of the stroke. Fuel oil is supplied to the spray nozzles by a governor con- trolled pump having a variable stroke or by compressed air as in the Diesel engine, making the supply of fire proportional to the load. A separate pump is generally supplied for each cylinder, which is capable of developing a pressure of about 400 pounds per square inch. Several of the Semi-Diesel type engines have water sprayed into the cylinder for the purpose of cooling the cylinder and piston, and as an aid in the combus- tion. This water spray increases the output of a given size cylinder by the amount of the steam formed by the heat of the cylinder and piston walls, and by the increased rate of combus- tion. The amount of water supplied to the cylinder is equal, approximately to the amount of fuel oil. The water connection is made in the air intake pipe so that the water spray and the intake air are drawn into the cylinder at the same time. There is very little difference in the efficiency of the Diesel and Semi-Diesel in favor of the true Diesel type for both have accomplished records of a brake horse-power hour on .45 pound of crude oil in units of the same capacity. Neglecting GAS, OIL AND STEAM ENGINES 177 the question of efficiency the Semi-Diesel has many advantages which are due principally to the differences in compression pressures. Valve and piston perfection in regard to leakage is not as essential with the semi-type as with the Diesel, as the former is not dependent on compression for its ignition. This means that the Semi-Diesel has a lower first cost and a lower maintenance expense. Its low compression pressure makes starting possible without the use of compressed air with engines of a considerable horse-power. As the explosion pressure is much lower than with the Diesel type there is less strain on the working parts and lubrication is much more easily per- formed. Compared with the ordinary type of kerosene engine the Semi- Diesel is much more positive in its action as the oil is sure to ignite when sprayed on the hot surface of the bulb or plate when under the comparatively high compression. In the engine where the air is mixed with the vaporized fuel before it is drawn into the cylinder, it is difficult to obtain perfect combustion be- cause of the uncertain mixtures obtained on varying loads by the throttling method of governing. At light loads the only difficulty encountered with the Semi-Diesel type is that of keeping the igniting surface hot enough to fire all of the charges. In the majority of cases the two stroke cycle type of Semi- Diesel engines compress the scavenging air in the crank cham- ber in the same way that a two stroke cycle gasoline motor performs the initial compression, although there are several makes that compress the air in an enlarged portion of the cyl- inder bore by what is known as a "trunk" piston. This initial compression determines the speed of the engine, the pressure limiting the time in which the air traverses the cylinder bore and sweeps out the burnt gases of the previous explosion. (68) De La Vergne Oil Engines. Two types of four stroke cycle oil engines are built by the De La Vergne Machine "Company, which differ principally in the method and period of injecting the fuel into the cylinder. While both types compress only pure air in the working cylin- der, the oil is injected in a heated vaporizer during the suction stroke in the smaller engine (type HA), and is injected directly into the combustion chamber of the larger engine (type FH) at the point of greatest compression. This fuel timing classi- GAS, OIL AND STEAM ENGINES 179 fies the type FH as a semi-Diesel, while type HA comes under the head of that class of engines known as aspirators. Semi-Diesel (Type FH) During the suction stroke, air is drawn into the cylinder through the inlet valve located on the top of the cylinder head, and on the return, or compression stroke, the air is compressed i I 76-b. Cross-Section of Type F H, De La Vergne Oil Engine. to about 300 pounds per square inch in the combustion cham- ber. The compression heats the air to a high temperature which is still further increased by contact with the hot walls of a cast iron vaporizer D, shown by Fig. 76-b. At the com- pletion of the compression, the fuel is injected in a highly atomized state by compressed air through the spray nozzle F, the spray being thrown into the vaporizer. The vapor formed by the contact of the spray with the walls 180 GAS, OIL AND STEAM ENGINES of the vaporizer mixes with the compressed air in the com- bustion chamber and is ignited at the instant of fuel admission by the combined temperatures of the vaporizer and compres- sion pressure. As the fuel is not injected until the proper instant for igni- tion, it is possible to obtain a relatively high compression without danger of the charge preigniting. The oil is supplied to the nozzle by a fuel pump under pressure. The atomizing air takes the oil at pump pressure and performs the actual injection. Details of the spray valve are shown by Fig. 76, in which the oil and air are entered at a pressure of about 600 poun.ds per square inch. . Fig. 76. De La Vergne Spray Nozzle. The air and oil enter the nozzle at opposite sides of the cylinder B which fits snugly into the valve body A. As the air and oil proceed side by side along the ^outside of B, they are forced to pass through a series of chambers connected by a system of fine diagonal channels on the surface of B which results in a very fine subdivision and intimate mixture. The charge is admitted to the cylinder by a sort of needle valve about one-half inch in diameter which is provided with a spring that holds it closed on its seat as shown by C, in Fig. 76. The needle is so constructed that it may be readily removed at any time for inspection. The spray valve is located on the right hand side of the valve chamber directly opposite GAS, OIL AND STEAM ENGINES 181 the vaporizer and is operated by an independent cam on the camshaft. The vaporizer consists of an iron thimble having ribs on the inside to increase the radiating surface. In start- Fig. 76-c. De La Vergne Governor and Fuel Pump. ing, the vaporizer is heated for a few moments until it reaches the temperature necessary for vaporizing the fuel, but after the engine is running, the blast lamp is removed and the tem- perature is maintained by the heat generated by the com- 182 GAS, OIL AND STEAM ENGINES bustion of the successive charges. Since the fuel is ignited at the instant that it makes contact with the vaporizer, it is possible to accurately adjust the point of ignition by adjusting the position of the fuel cam on the camshaft. Air for spraying the fuel is supplied by a two stage air compressor that is driven from the crankshaft by an eccen- tric. The air compressed by the first stage is stored in tanks at about 150 pounds pressure for starting the engine. The second stage compresses the air to about 600 pounds pressure, but is correspondingly small in volumetric capacity since it handles only enough air to spray the oil which amounts to about 2 per cent of the cylinder volume. A governor con- trolled butterfly valve in the air intake pipe regulates the amount of air taken in on the second stage to suit the vary- ing charges of oil injected at each load. In starting by compressed air, a quick opening lever oper- ated valve on the cylinder head is used to admit air from the tanks to turn the engine over until the first explosion takes place. If the vaporizer is sufficiently heated by the torch, the explosion occurs during the first revolution of the crank shaft. At a point about 85 per cent of the expansion stroke, the exhaust valve is opened, and the products of combustion are expelled into the atmosphere. When starting, the com- pression may be relieved by shifting the starting lever from the exhaust cam to the auxiliary starting cam provided for that purpose. Speed regulation is affected by a Hartung governor, driven from the camshaft, which actuates the oil supply pump through levers by shifting the point of contact between the pump levers and its actuating cam. This lengthens or shortens the stroke of the pump in accordance with the requirements of the loa'd. The type FH engines are built in both single and twin cylinders ranging from 90 to 180 horse-power in the single cylinder type to 360 horse-power in the twin. Since the fuel injection of the smaller engine type HA differs from that just described, it will be described separately in the following section. The De La Vergne Oil Engine (Type HA) In the small four stroke cycle De La Vergne Oil Engine, the fuel is injected into a heated vaporizer during the suction stroke in such a way that the vapor and intake air do not form a mixture in the cylinder proper. On the return stroke of GAS, OIL AND STEAM ENGINES 183 the piston, the compression of the pure air takes place which forces the air into the vaporizer and into intimate contact with the oil vapor. This forms an explosive mixture which ignites and forces the piston outwardly on the working stroke. The release and scavenging are performed in a similar man- ner to that of a four stroke cycle gas engine. Both the inlet and exhaust valves are of the mechanically operated poppet type, and as both the inlet and exhaust gases pass through the same passage, the entering air i heated to a comparatively high temperature. The injection pump receives the fuel from a constant level stand pipe or tank, located near the engine and injects the fuel into the vaporizer through a spray nozzle. The vaporizer is a bulb shaped vessel that is connected with the cylinder through a short post and really forms a part of the combus- tion chamber. Since no water jacket surrounds the vaporizer, it remains at a high temperature and vaporizes the oil at the instant of its injection. Because of the residual gases remain- ing in the chamber, ignition does not occur until air is forced through the passage by the compression. The air inlet valve and the fuel injection valve are opened at the same instant by a cam lever that also operates the pump. On the compression stroke, the air which is at a pressure of approximately 75 pounds per square inch enters the vapor- izer, and ignition occurs, partly because of the increased heat due to 'the compression and partly because of the supply of additional oxygen. Internal ribs provided in the vaporizer greatly increase the heat radiating surface and add to the thoroughness with which the atomized oil is vaporized. Since no mixture of air and fuel takes place in the cylinder proper, sudden changes in the load do not affect the ignition of the charge as the heated surfaces are surrounded with compara- tively rich gas under all conditions. Before the engine is started, the vaporizing chamber is heated to a dull red heat by means of a blast torch in order to vaporize the oil for the first stroke. As soon as the engine is running, the lamp is cut out and the temperature is maintained by the heat of the successive explosions. The combustion at- tained by this method is very complete even with the heaviest fuels, and whatever carbon deposit is formed occurs in the vaporizer from which it is easily removed. The contracted opening of the vaporizer passage effectually prevents the solid matter from working in the bore or valves. 184 GAS, OIL AND STEAM ENGINES A Porter-type fly ball governor maintains a constant speed at varying loads by regulating the quantity of fuel supply to the" vaporizer, the air intake remaining constant. A by-pass valve, controlled by the governor divides the oil supplied by the pump, into two branches, one of which leads to the spray nozzle and the other to the supply tank. In the case where all of the oil is not supplied to the vaporizer because of a light load, the by-pass valve will return the surplus to the tank, thus maintaining a constant pressure at the spray nozzle. When operating under ordinary loads, the governor opens ' only the small inside valve which regulates the amount of oil injected into the vaporizer. But should the engine speed up, due to a sudden change in the load, the governor will not only open the small valve but also the large concentric valve, in which case all of the oil will return to the tank. The mak- ers guarantee the following speed variation limits under the different loads. Ordinary Variation 2*/ 2 per cent. Full load to one-quarter load 4 per cent. Full load to no load 5 per cent. (69) Operating Costs of the Semi-Diesel Type. As the semi-Diesel type engine will operate successfully on the lowest grades of crude oils, with an efficiency that compares favorably with the true Diesel type, the operating expenses are very much lower than with the gas or gasoline engine. With the same fuels, the semi-Diesel will show greater net saving than the Diesel with a low load factor, as the fuel saving is not eaten up by the high first cost, and overhead charges of the true Diesel. Western trude oils with a specific gravity of .960 (16 Beaume) are being used daily with this type of en- gine while nearly every builder of the semi-Diesel type will guarantee results with oils up to 18 Beaume (.948 Specific Gravity). Fuel of this grade will cost anywhere from \ l /2 cents to 3^2 cents per gallon in tank car lots, depending on the dis- tance of the engine from the wells or refinery. With fuel oil weighing 7 l /2 pounds per gallon, an engine consuming .65 pounds per horse-power hour (a usual guarantee) at full load, the cost of a horse-power hour delivered at the shaft will be .26 cent with fuel at 3 cents per gallon. This the lowest fuel expense of any prime mover even with steam or gas units of great power. In a twenty-four hour test of a GAS, OIL AND STEAM ENGINES 185 De La Vergne oil engine running on 19 Beaume oil, the con- sumption was considerably below the figure assumed above, being .508 pounds per horse-power hour. Even the engine was exceeded in a test made on a 175 horse-power engine by Dr. Waldo, which gave a consumption of .347 pounds of oil per horse-power hour with oil of .86 Specific Gravity. The following is a tabulation of reports received by the De La Vergne Machine Company from the Snead Iron Works, giving the cost of power at their plant under actual working conditions extending over a period of twenty-four months. The plant consisted of a 17 X 27^ inch De La Vergne semi- Diesel type engine of 180 horse-power rated capacity, the load factor being 54.2 per cent. The total power produced during the record was 552,217 horse-power hours, with a work- ing period of 588 days. Fuel = 28.8 Beaume 7.35 pounds per gallon. TABULATION Items Total Cost Cost per Cost per K.W. Hour H.P. Hour Fuel Oil, 38,211 gallons $859.75 $.00232 $.00155 Lubricating Oil 228.72 .00061 .00041 Miscellaneous Stores and Repairs... 123.20 .00032 .00022 Labor and Attendance 1361.42 .00368 .00246 Total $.00693 $.00464 Fuel oil used = .761 pounds per K. W. hour = .508 pounds per horse-power hour. Computing from the load factor of 54.2 per cent, the cost of power produced under the above conditions would be $9.30 per horse-power year, or $13.98 per kilowatt year. This result is obtained by assuming that the horse-power hours would be increased from 552,217 to 1,077,354, or in proportion to the actual load factor, the period, of course being the same in both cases. (70) Elyria Semi-Diesel Type. A type of semi-Diesel type oil engine has been recently developed by the Elyria Gas Power Co., Elyria, O., that presents many features of interest. It operates on the two stroke cycle principle, and with the exception of the spray nozzle has no valves in the working cylinder. The prin- ciple of the semi-Diesel type cycle as distinguished from the true Diesel engine, was described in Chapter III, as having 186 GAS, OIL AND STEAM ENGINES the following characteristics. (1) Fuel injection. (2) Medium compression pressure. (3) Hot plate ignition. (4) An ef- ficiency approximating that of the true Diesel type. It is claimed that the change from the ordinary four stroke cycle Diesel cycle has been accomplished with practically no loss of thermal efficiency, and that the elimination of the many moving parts of that type has done away with many of the operating difficulties. By the introduction of a false piston end and an unjacketed cylinder head, the loss of efficiency due to the lower compression is compensated by the reduction of Fig. 77. Working Cylinder of Elyria Oil Engine. heat loss to the jacket water. Because of the high temper- ature it is possible to burn the heaviest fuels with a maximum pressure not exceeding 400 pounds per square inch, and with- out trouble due to missed ignition at light loads. With a given cylinder capacity this heating effect has increased the output about 75 per cent. The loss due to the friction of the scaveng- ing apparatus causes a fuel consumption of approximately 10 percent more than a standard four stroke Diesel. Unlike the Diesel, this engine automatically controls the quantity of injection air admitted to the cylinder at different loads, the air corresponding with the amount of fuel injected. This is in marked contrast with the Diesel engine which admits a constant volume of air at all loads. In place of the usual GAS, OIL AND STEAM ENGINES 187 crank-case compression of the scavenging air met with in the ordinary two stroke cycle engine, the initial compression in the Elyria engine is performed by a "differential piston" which acts in an enlarged 'portion of the cylinder bore. This con- struction increases the volumetric efficiency from 70 percent, in the case of the marine type, to well over 90 percent, and it also does away with the bad effect of the compression on the lubrication of the main crank shaft bearings. The working piston and differential piston as shown by Fig. 77 is separate castings fastened together by four studs, and the Fig. 78. Compressor Cylinder of Elyria Oil Engine. piston pin is carried by the differential piston which acts as a cross-head, taking all of the sjde thrust from the main piston. The working piston is easily taken from the cylinder by remov- ing the cylinder head and the four nuts that fasten it to the differential piston casting. The displacement of the differential piston is approximately 1.9 times the displacement of the work ing piston which is more than enough for thoroughly scaveng ing the cylinder and supplying air for combustion. The air suction is controlled by a, piston valve which eliminates much of the loss encountered in the marine type of two stroke cycle. In the figure may be seen the separate or auxiliary piston head which is bolted to the piston proper, a construction that greatly increases the working temperature, and allows a sym- metrical form of piston. By removing the cap over the inlet 188 GAS, OIL AND STEAM ENGINES port, -it is possible to inspect the condition of the six piston rings with removing the piston from the cylinder. Because of the clean burning of .the fuel lubrication, is easily effected by the force pump which supplies oil at three points around the cylinder wall. Three stages of compression are employed for providing the air for fuel injection, the first stage being accomplished by the differential piston, and the remaining two stages by a separate air pump driven by an eccentric from the crankshaft. This cylinder also supplies the air for starting the engine, the air being taken from the second stage and piped to the storage tank. The suction of the second stage pump which receives its air from the differential pump (first stage) is controlled auto- matically so that it is possible to keep the supply tank at any desired pressure regardless of the pressure or amount of air used for the fuel injection. Air from the tank (at approximately 200 pounds pressure) is piped to the suction side of the third stage air pump. In this suction line is a valve, controlled by the governor, which regulates the amount of air admitted to the injection nozzle, and also the amount. This pressure at the nozzle will vary from 500 pounds per square inch to 1000 pounds depending on the load and the nature of the fuel. The high pressure air travels directly from the pump to the fuel valve casing, and -is equipped with a safety valve and pressure gauge. The fuel pump is driven by a Rites Inertia Governor located in the fly-wheel which varies the stroke of the pqmp plunger and gives a correct proportion of fuel to the load. This type of governor has been extensively used on high speed engines and is exceeding accurate. The fuel pump may be disconnected from the governor drive, and operated by hand when it is nec- essary to provide fuel for starting. The spray or injection valve is operated by a cam, which lifts the valve at the proper mo- ment in a very simple manner. The valve proper is made of a single piece of steel with openings of ample size, so that there is no danger of clogging with the heaviest fuels. As the valve only lifts 1/16 of an inch, the amount of work required to operate the valve is very small. Starting is accomplished by spraying cold gasoline into the cylinder through the fuel valve in the same manner that the heavier oil is fed during operation, and the ignition is performed by a high tension coil and batteries. No spark time device is used, so that a continuous shower of sparks is thrown into GAS, OIL AND STEAM ENGINES 189 the mixture during the starting period. Within a minute after the engine is started, the ignition switch may be opened, the gasoline cut off, and the heavy oil. turned on for continuous running on full load. Starting by an electric spark avoids the inconvenience and danger of torch starting with a retort. Cooling water is admitted around the compressor cylinder from which point it goes to the working cylinder, and is there discharged. Less water is required for this type of engine than for the ordinary gasoline engine, for with the water en- tering at 60F, only 3 gallons per horse-power hour is used. With fuel oil weighing 7.33 pounds per gallon the makers claim a fuel consumption of .65 pounds per horse-power at the rated load. The amount of cylinder oil used does not exceed 1 pint per 100 horse-power hours, while the loss of the bearing oil is extremely small because of the return system. (71) Remington Oil Engine. The Remington Oil Engine is a vertical oil engine operating on the three port, two stroke cycle, and is an oil engine in the strict meaning of the word, the oil consumed being introduced into the combustion chamber as a liquid and gasified within this chamber. The method of gasifying and igniting the charge of oil in the Remington Oil Engine is unique. Only clean air un- mixed with any charge, is taken into the crankcase. This air is afterwards passed up into the cylinder and compressed until its temperature has raised to a point high enough to vaporize the oil which is injected into it. The charge of oil is then atomized into this hot compressed air and turns immediately into a vapor, which finds itself well mixed with the charge of air, comes in contact with a firing pin recessed in the head, ignite and burns. This method of having the oil well gasified and mixed with air before ignition begins, prevents the forma- tion of carbon which is formed when oil not well gasified and mixed with air comes suddenly MI contact with very hot surfaces. This perfect system of gasifying the oil has the effect not only of preventing the formation of carbon in the cylinder, but also of increasing the mean effective pressure and therefore de- creasing the amount of fuel necessary for doing a certain amount of work. The engine passes through its cycle of oper- ations smoothly, and does not have to be constructed with ex- cessive weight. 390 GAS, OIL AND STEAM ENGINES Fig. 79. Cross-Section of Remington Oil Engine. GAS, OIL AND STEAM ENGINES 191 The Remington Engine is of the valveless type, delivering a power impulse in each cylinder for each revolution of flywheel. The gases are moved in and out of the cylinder through ports uncovered by the movement of the piston, which itself performs also the function of a pump. On the up stroke of the piston a partial vacuum is created in the enclosed crankcase, causing air to rush in when the bot- tom of the piston uncovers the inlet port seen directly under the exhaust port (23), Fig. 79. On the next down stroke this air is compressed in the crankcase to about four or five pounds pressure per square inch. Meanwhile the mixture of oil vapor and air already in the cylinder is burning and expanding. When the piston approaches the end of its down stroke, it uncovers the exhaust port (23), permitting the burnt charge to escape, until its pressure reaches that of the atmosphere. Fig. 80. Remington Spray Nozzle. Directly afterward the transfer port on the opposite side of the cylinder is uncovered by the piston, thereby allowing a portion of the air compressed in the crankcase to rush into the cylinder, where it is deflected upwards by the shape of the top of the piston and caused to fill the cylinder, thereby expell- ing the remainder of the burnt charge. The piston now starts upward, compressing the fresh charge of air into the hot cylinder head. Near the end of the stroke, a small oil pump, mounted on the crankcase and controlled by the governor, in- jects the proper amount of oil through the nozzle (13), into the compressed and heated air. This oil is atomized in a vertical direction through a hole near the end of the nozzle. It is therefore vaporized and gasi- fied before there is a possibility of its reaching the cylinder walls. The spray of oil is ignited by the nickel steel plug (12), which is kept red hot by the explosions because the iron walls surrounding it are protected from radiation by the hood (11). 192 GAS, OIL AND STEAM ENGINES By the burning of the oil spray in the air the pressure is grad- ually increased and the piston forced downward, this being the power or impulse stroke. Near the end of the down stroke, the ''exhaust port is again uncovered and the burnt gases dis- charged. Fig. 81. Fuel Pump and Mechanism of Remington Oil Engine. The operations above described take place in the cylinder and crankcase with every revolution. Each upstroke of the piston draws fresh air into the crankcase and compresses the air transferred to the cylinder. Each down stroke is a power stroke, and at the same time compresses the air in the crank- case preparatory to transferring it to the cylinder by its own pressure at the end of the stroke. The same volume of air enters the cylinder under all condi- tions, and the power is regulated by modifying the stroke of the GAS, OIL AND STEAM ENGINES 193 oil pump, which may be done by hand or automatically by the governor in the flywheel. A separate fuel pump is provided for each cylinder when multiple cylinders are used, making it absolutely certain that each cylinder shall receive the same amount of fuel for a position of the control lever. When starting the engine, the hollow cast iron prong rising from the cylinder head is heated by a kerosene torch, and when hot, a single charge of oil is admitted to the cylinder by work- ing the hand pump. The flywheel is now turned backward, thereby compressing the charge which ignites the fuel before the piston reaches the highest position. After being started the engine, the torch may be extinguished. Fig. 82. Two Cylinder Remington Oil Engine Direct Connected to Dynamo. The governor is of the centrifugal type. It has an L-shaped weight, pivoted to the piece attached to the flywheel. As the engine speed increases, the weight tends to swing outward toward the flywheel rim, and thereby moves the arm attached to it so as to shift the cam along the crankshaft toward the left. This cam turns with the shaft, and operates the kerosene oil pump. According to the position of the cam on the shaft, it will impart to the pump plunger a long or a short stroke, thereby injecting more or less oil into the cylinder. The lever pivoted on the bracket moves with the cam and is used for 194 GAS, OIL AND STEAM ENGINES controlling the engine's speed by hand. To stop the engine the handle of the lever is pulled towards the flywheel, thereby interrupting the pump action altogether. The handle of the control lever can be fitted with an ad- justable speed regulator when required. This device is for use on marine engines to enable the operator to slow down the engine. The speed regulator does not interfere with the action of the governor but acts in conjunction with it. What- ever the speed of the engine may be, it is under the control of the governor. The engine can be controlled from the pilot house if such an arrangement is desirable. The fuel pump is made of bronze. The valves are made of bronze and are designed with very large areas. The plunger is made of tool steel. A bronze cup strainer is attached to the lower end of the pump to prevent sediment or foreign matter from reaching the pump valves. As a result of the care used in its construction, the fuel pump is not only very sensitive in measuring the oil required by the governor, but is also very strong and durable. The nozzle through which the fuel is atomized into the cylinder is thoroughly water jacketed to prevent the forma- tion of carbon within the nozzle. It is so constructed that the water jacket spaces and fuel spaces can be opened for inspection. Lubrication of all the important bearing joints is effected by a mechanical force feed oiler, pressure feed oiler or by gravity sight feed oilers, depending upon the service for which the en- gine is designed. Oil is fed in this manner to the piston, the main bearings and the crankpin bearings. The oil for the crankpin is dropped from a tube into an internally flanged ring attached to the crank by which it is carried by centrifugal force to a hole drilled diagonally through the crank and crankpin to the centre of the bearing. This insures that all the oil intended for the crankpin shall reach it. This feature, as well as the use of the sight feed oiler itself, is in line with the best modern high speed engine practice, and is an important factor in the reliability of the engine. CHAPTER VIII IGNITION SYSTEMS (73) Principles of Ignition. It is the purpose of the ignition system to raise a small portion of the mixture to the combustion temperature, or the temperature at which the air and fuel will start to enter into chemical combination. When combustion is once started in a compressed combustible gas it will spread throughout the mass no matter how small the original portion inflamed. The rate at which the flame spreads through the combustion cham- ber depends upon the compression pressure, the richness of the mixture, the nature of the fuel and upon the number of points at which it is ignited. In practice perfect ignition is seldom realized. This is due not only to the ignition system itself but to poor mixture proportions, imperfect vaporizing of the fuel, and low com- pression; all of which tend to a slow burning mixture with the attendant losses. The best ignition system will be that which will cause the ignition to occur invariably at the point of highest compres- sion and which will supply ample heat to start the process of combustion with a cold cylinder, imperfect mixtures, and low compressions. An efficient and reliable ignition system is with- out a doubt the most important unit in the construction of a gas engine. As ignition systems have improved and become more reliable, so has the gas engine become more widely used and appreciated, and in almost a direct proportion to these im- provements. Many ingenious ignition systems have been proposed, but only two of these have met with any degree of success in practice; i. e., electrical ignition and ignition by means of the hot tube. Sponge platinum has the peculiar property of igniting jets of hydrogen gas, or hydrocarbons, without the aid of heat; this is due to the condensing effect of the platinum on these gases. 195 196 GAS, OIL AND STEAM ENGINES It was proposed to ignite the gaseous charge of the gas en- gine by means of the platinum sponge (catalytic ignition) but the system proved a failure because of the clogging of the pores in the sponge by fine particles of soot. Dr. Otto employed an open flame which was introduced into the mixture by means of a slide valve. This met with only a fair measure of success. Cerium, Lanthum and several other rare metals cause a considerable spark when brought into contact with iron or steel. The objection to this method was the expense of the Cerium plugs which required frequent renewal. The writer remembers a quaint attempt at firing the charge by means of a piece of flint and steel; the failure of this is obvious. The Diesel Engine, a great success from a thermodynamic standpoint, is fired by means of the heat produced by the com- pression of air, the fuel being sprayed into air which is com- pressed to several hundred pounds pressure. Mr. Victor Lougheed proposes ignition by means of a plati- num wire rendered incandescent by a current of electricity. The plan sounds feasible, but we are still waiting to be shown. Electric ignition is applicable to all classes of engines; in fact this system made the variable speed engine as used on automobiles, etc., a possibility, as accurate timing with the electric spark covers the range from the lowest possible speed to speeds of 4,500 revolutions per minute and over. (74) Advance and Retard. While the combustion of the mixture is extremely rapid under favorable conditions, there is, nevertheless, a percep- tible lapse between the instant of ignition and the final pres- sure established by the heat of the combustion. For this rea- son it is necessary that ignition should be started a certain length of time before the pressure is required if we are to ex- pect a maximum pressure at a definite point in the stroke of the piston. The amount by which the time of ignition precedes that of combustion is called the ADVANCE, and is usually given in terms of angular degrees made by the crank in travel- ing from the time of ignition to time of maximum pressure. Since the pressure is always required at the extreme end of the compression stroke, the degree of advance is given as the angle made by the center line of the cylinder with the center line of the crank at the instant of ignition. Should the ad- GAS, OIL AND STEAM ENGINES 197 vance be given as 10, for example, it is meant that the crank is still 10 from completing the compression when ignition occurs. Owing to variations in the richness of the mixture, and changes in the compression pressure, due to throttling the incoming charge, the rate of inflammation varies from time to time under varying loads. To keep the maximum pressure at a given point under these conditions it is necessary to vary the point of ignition to correspond with the increase or de- crease of inflammation. This variation of advance to meet varying loads is approximated by the governor in some engines, and manually in others. The advance of an automobile is an example of manual ignition control. Should the point of igni- tion vary from the theoretical point it will result in a loss of fuel and power, and for this reason the ignition should be under at least an approximate control. A wide variation in engine speed has a very considerable effect on the ignition point as there is less time in which to burn the mixture' at high piston speeds, and consequently the ignition must be further advanced to insure complete combustion at the end of the stroke. This fact is evident to those who have driven auto- mobiles. Should the ignition occur too early, so that combustion is complete before the piston reaches the end of the stroke, there will be a loss of power due to the tendency of the pressure to reverse the rotation of the engine. When starting an engine, over-advanced ignition will throw the crank over in the reverse direction from which it is intended to go, and will not only prevent the engine from coming up to speed but will prove dangerous to the operator. Due to the effects of inertia and self induction in several types of ignition apparatus, a greater advance will be required than that demanded by the combustion rate of the mixture. This sluggishness of the apparatus in responding to the piston position is called ignition LAG. The total advance required to have the combustion complete at the end of the stroke is equal to the advance required by the burning speed plus the ignition lag. Since lag is principally due to inertia effects, it is much greater at high speeds than at low, and it therefore causes an additional advance at high speeds. Causing the igni- tion to occur before the crank reaches the upper dead center is called ADVANCED IGNITION, causing it to occur after the piston has reached the upper dead center, or when on the outward stroke, is called RETARDED IGNITION. 198 GAS, OIL AND STEAM ENGINES Ignition is retarded when starting an engine to prevent it from taking its initial turn in the wrong direction. As the combustion takes place after the- compression, with the piston moving on the working stroke, in retard, it is impossible for the pressure, to force the piston in any direction but the right one. - Excessively retarded ignition will cause a power loss and will also cause overheating of the cylinder and valves as the combustion is slower. (75) Preignition. Preignition which is in effect the same as over-advanced ignition as due to causes within the cylinder such as incandes- cent carbon deposits- or thin sharp edges in the cylinder that have become incandescent through the heat of the successive explosions. Preignition is very objectionable since it causes heavy strains on the engine parts and causes a loss of power in the same way as . over-advanced ignition. Any condition that causes the preigniting of the charge should be removed immediately. (76) Misfiring. The failure of the ignition apparatus to ignite every charge is called MISFIRING. This missing not only causes a waste of fuel and a loss of power but it also causes an increased strain on the engine parts because of the violence of the explosion following the missed stroke. The heavy explosion is due to the fact that the stroke following the "miss" is more thoroughly scavenged by the two admissions of the mixture than the or- dinary working stroke, and consequently contains a more active charge. (77) Hot Tube Ignition. A combustible gas may be ignited by bringing it into contact with surface heated to, or above the ignition temperature. It is upon this principle that hot tube ignition is based. In practice this surface is provided by the bore of a tube which is in communication with the charge in the cylinder, the outer end of the tube being closed or stopped up. Around this tube is an asbestos-lined chimney which causes the flame from the Bunsen burner to come into contact with the tube and also prevents draughts of air from chilling it. A Bunsen burner is located near the base of the tube and maintains it at bright red heat. The gas for the burner is sup- GAS, OIL AND STEAM ENGINES 199 plied from a source external to the engine. When the fuel used is gasoline, a gasoline burner is used, which is fed from a small supply tank located five or six feet above the burner. During the admission stroke, the hot tube is filled with the non-combustible gases remaining from the previous explosion, therefore, the fresh entering gases cannot come into contact with the hot walls of the tube and cause a premature explo- sion, before the charge is compressed. As the compression of the new charge proceeds, the fresh gas is forced farther and farther into the tube and at the highest point of compression it has penetrated far enough to come into contact with the hot portion. At this point the explosion occurs. The tube being of small bore, does not allow of the burnt gases mingling with the fresh within the tube; the waste gases in the tube acting as a regulating cushion. The distance of travel of the new mixture is proportional to the compression, hence the explosion does not occur until a certain degree of compression is attained. The length of the tube required for a given engine is a mat- ter of experiment, as is also the location of the heated portion. High compression naturally forces the mixture farther into the tube than low, therefore the flame should come into con- tact with the tube at a point nearer the outer end with high compression than with a low compression. Shortening the tube causes advanced ignition, as the mixture reaches the heated portion sooner, or earlier in the stroke, because of the decreased cushioning effect of the residue gases in the tube. The length of tube and location of maximum heat zone should be so proportioned that combustion will take place at the highest compression. Moving flame to outer end of the tube retards ignition. Moving the flame toward the cylinder advances it. While the hot tube is the acme of simplicity in construction, it is not the easiest thing to properly adjust, as the adjustment depends on compression, temperature of the tube, and the quality of the mixture. Any of these variables may cause im- proper firing. The hot tube is rather an expensive type of ignition with high priced fuel, as the burner consumes a considerable amount of gas, and is burning continuously during the idle strokes as well as during the time of firing. 200 GAS, OIL AND STEAM ENGINES It is practically impossible to obtain satisfactory results from a hot tube on an engine that regulates its speed by varying the mixture or compression, as engines running on a light load will not have sufficient compression to cause the mixture to come into contact with the hot surface, the engine misfiring on light loads. The tubes are made of porcelain, nickel steel alloy, or com- mon gas pipe, and are of various diameters and lengths. All of these materials have their faults. Porcelain being very brittle, is liable to breakage. Gas pipe burns out and corrodes rapidly. Nickel alloy is not liable to breakage, is not so susceptible to corrosion as iron, but is far from being a permanent fixture. Timing valves are a feature of some systems of hot tube ignition, which correct to a certain extent the irregularity of firing of the plain type of tube. The timing valve is introduced in the passage connecting the cylinder and tube, and prevents the gas in the cylinder from coming into contact with the heated surface until ignition is desired. The valve is operated by means of mechanism connecting it with the crank shaft. It is evident that with sufficient com- pression in the cylinder, the time of ignition can be obtained with certainty. This mechanism is rather complicated, and subject to wear, and the advantage gained by the fixed point of ignition is offset by mechanical complication and consequent trouble. The action of hot tube igniters is erratic and their use is not advisable unless under unusual conditions. The open flame used in heating the tube is a constant menace, as it is surrounded by inflammable vapors. This feature alone condemns it in the eyes of the insurance underwriters; in many places the use of the hot tube is prohibited both by the underwriters and city ordinances. The above inherent defects of hot tubes are supplemented by breakage, "blowing," and clogging of the tube or passage with soot and products of corrosion, each factor of which will cause misfiring. In case of misfiring, after determining that the tube is not broken or clogged with soot or dirt, see that the engine is being supplied with the proper mixture; that you are obtain- ing the proper compression; and that the Bunsen burner is de- livering a bright blue flame on the tube at the proper point, GAS, OIL AND STEAM ENGINES 201 Never allow the burner to develop a yellow sooty flame. A yellow flame indicates that insufficient air is being admitted to the burner. Remember that an overheated tube is quickly destroyed, and will cause misfiring as surely as an underheated tube. Regulate the gas supply to the burner. A small leak near the outer end of the tube will destroy the cushioning effect of the burnt gas, and hence will cause pre- mature firing of the charge. Procure a new tube. - Many engines are provided with a sliding burner and chim- ney which allows of some adjustment of the flame on the tube. In cases of persistent misfiring, move the chimney one way or the other. It may improve the ignition. (78) Electrical Ignition. Ignition by means of an electric spark is by far the most satisfactory method as it makes accurate timing and prompt starting possible. It is the most reliable of all systems and is easily inspected and adjusted by anyone having even a rudimentary idea of electricity or the gas engine. For this reason electric ignition is used on practically all modern en- gines (with the exception of the Diesel types). The spark is caused by the current jumping an opening or gap in the con- ducting path of the current, and the ignition of the charge is obtained by placing this cap in the midst of the combustible mixture to which the spark communicates its heat. The method of producing the spark gap, and the method by which the current is forced to jump the gap, divides the electrical ignition system into two principal classes: (1) The MAKE AND BREAK, or LOW TENSION system. (2) The JUMP SPARK or HIGH TENSION system. In either system the spark is produced by the electrical fric- tion of the current passing through the high resistance of the gas in the spark gap. The incandescent vapor in the gap formed by this increase of temperatures causes the flash that is known as the spark. The temperature of the gap depends principally upon the current flowing through it, the amount of heat developed being proportionat to the square of the current. There is of course a practical limit to the amount of current used in the ignition apparatus to produce spark heat. The limit is generally set by considerations of the life of the bat- tery furnishing the current, expense of generating the cur- rent, and the life of the contact points between which the spark occurs. 202 GAS, OIL AND STEAM ENGINES The heat developed by an electric current is proportional to the amount of resistance offered to its flow and the strength of the current employed. The greater the resistance, the more heat developed. The resistance of copper wire (the usual conducting path), being very low causes little rise in temperature, but the air in the opening or break has a resistance of many thousands of times the resistance of the copper; hence the current passing across the opening spark or gap raises the air to an exceed- ingly high temperature. With a comparatively heavy- current flowing across the break, the temperature developed is high enough to boil or vaporize any metal in contact with the spark or flame, render- ing the metallic vapors incandescent. With sufficient current, the ends of the wires which constitute the break may be melted away. For the successful and continuous operation of the engine it is imperative that ends of the conducting path or terminals be made of a metal of a high fusing point in order to with- stand the heat of the spark and also that the current be kept to as low a value as possible. In actual construction the spark gap terminals are generally made of platinum or platino-iridium, or an alloy of high fus- ing point. Iron is sometimes used, but deterioates rapidly. Nickel steel lasts longer than common iron or steel but is not as durable as platinum or its alloys. As the temperature of the electric spark or arc is approxi- mately 7,500 F., and the ignition temperature of an ordinary rich gas at 70 Ibs. compression is 1,100 F., it is evident that the quantity of current for ignition may be kept to an exceedingly low value. High compression increases the resistance of the spark gap, and requires higher electrical pressure to force a given current across a gap of given length. (79) Sources of Current. The electric current that causes the ignition spark is usually generated or supplied by one of the three following methods: 1. By the primary battery which converts the chemical en- ergy of metal, and some corroding fluid, into electrical energy, by chemical means. 2. By the magneto or dynamo that converts mechanical work or energy into electrical energy through the method of magnetic induction. 3. By the storage or secondary battery which acts as a GAS, OIL AND STEAM ENGINES 203 reservoir or storage tank for current that has been generated by either of the two above methods. A storage battery sim- ply returns electrical energy that has been expended on it by an external generator. A storage battery does not really gen- erate electricity but as it is often used as a source of current for an ignition system, we will consider it as a generator. Current producers that convert chemical or mechanical en- ergy into electrical energy are called primary generators, and are represented by the primary battery and dynamo. The above methods are used for generating current for either the high or low tension systems. Electricity may also be produced by friction, but as such current is without heat value it is not used for ignition pur- poses. Electricity produced by friction is called static electricity. Primary and storage batteries always deliver a direct or continuous current of electricity, that is a current which flows continually in one direction. Dynamos are usually made to furnish a direct current, but can be built to deliver either direct or alternating. Alternating current, unlike the continuous current, changes the direction of its flow periodically; flowing first in one direc- tion and then in the other, the flow alternating in equal periods of time. Magnetos being a special form of dynamo can furnish either class of current, but with few exceptions are built for generat- ing alternating current. Either current may be used for ignition purposes for either high or low tension systems. Alternating current has several advantages not possessed by the continuous current, when used for ignition purposes. The principal advantages are: 1. Alternating current does not transfer the electrode metal of contact points, and consequently causes less trouble with vibrators and "make" and "break" igniters. 2. Magnetos generating alternating current are less com- plicated, have fewer parts to get out of order, and are cheaper to keep in repair. 3. Alternating current is not liable to burn out spark coils or overheat with an excessive voltage. 4. Alternating current generators can be used at any speed without the use of governors. When installing an ignition system give due consideration to the reliability of the source of current. The gas engine is no 204 GAS, OIL AND STEAM ENGINES 43-a. The Esselbe Rotary Aero Motor. Four Pistons are Contained in the Ring Shaped Cylinder at the Left Which are so Connected with Cranks and Gears in the Gear Box that the Pistons and the Cylinder Rotate in Opposite Directions. As the Pistons Rotate they also Oscillate Back and Forth in Regard to One Another, so that the Working and Compression Strokes are Performed. From Aero London. GAS, OIL AND STEAM ENGINES 205 more reliable than its source of current. Failure of the current means the failure of the engine. (80) Primary Batteries. Current is produced in a primary battery by the chemical action of a fluid known as an ELECTROLYTE upon two dis- similar metals or solids known as the electrodes. One of the electrodes, the negative, is usually made of zinc which is more readily attacked by the electrolyte than the positive electrode. As the metal of the negative electrode is dissolved and passes into the solution during the process of current generation, the electrolyte is also exhausted. The production of current is accompanied by the liberation of hydrogen gas from the elec- trolyte from which it is displaced by the zinc taken into solu- tion. When the electrodes are immersed in the electrolyte, and the outer ends of the electrodes are connected with a wire, a current will flow from the positive electrode to the negative through the wire, and from the negative to the positive elec- trode through the fluid. It will be seen that to complete the circuit between the electrodes it is necessary that the current flows through the electrolyte. Electrical energy is actually generated in the primary bat- tery by the chemical combustion of the negative electrode in the same way that heat energy is developed by the burning of a fuel. By connecting the binding posts of the electrodes to the two wires of the external circuit, a current will flow through the circuit as long as the electrodes remain undissolved, or until the positive electrode is covered with hydrogen gas bubbles. .The bubbles of gas tend to insulate the positive electrode from the electrolyte or fluid, thus breaking the circuit through the* fluid, and stopping the flow of current. This action is known as polarization. When a battery is polarized, the only remedy is to discon- nect it from the circuit and allow it to rest or recuperate. The greater the current drawn from a battery, the more rapid the polarization, and it is evident that if the battery is to be used for long periods, polarization must be eliminated, or the cur- rent must be considerably reduced in volume. A battery that delivers a small current has a much greater capacity in am- pere hours than a battery that has a higher rate of discharge. 206 GAS, OIL AND STEAM ENGINES The greater the discharge rate the longer must be the rest periods. A battery that is designed for continuous service, or for de- livering heavy currents of long duration, is called a closed- circuit battery. Polarization is eliminated in closed circuit batteries by various methods, the usual methods being to place some substance in the electrolyte that will destroy the hydrogen film; or by packing some solid oxidizing material around the positive electrode that will absorb the hydrogen; or by making the positive electrode of some material that will destroy the hydrogen as soon as it is developed. Batteries that are capable of being operated only for short periods, on account of polarization, are called open circuit batteries. Open circuit batteries are cheaper and more simple than closed circuit batteries. For ignition purposes, a battery is made that is a compromise between the closed and open circuit cells, this being a battery in which the polarization is only partially suppressed. As the demand for current on an ignition battery is small with comparatively long rests between contacts, the compromise battery answers the purpose and is fairly cheap. All primary batteries are in reality wet batteries, for the reason that it would be impossible to cause a chemical reac- tion and a current with a dry electrolyte. The action of dry and wet batteries is identical. There are many types of wet battery in use for various pur- poses, but few of them are adapted for gas engine ignition be- cause of a tendency to polarize or because of the cost of main- tenance. All wet batteries are not suitable for portable or automobile engines because of the slopping of the liquid electrolyte and the danger of breaking the containing jars. Their weight and bulj< is also a drawback. If the electrolyte or the electrodes be made of impure ma- terial local currents will be generated. These currents de- crease the life of the cell without producing any useful current in the ignition circuit. Due to the deteriorating effects of the local currents, batteries standing idle for several months will often be found to be completely discharged and worthless without having done any useful work. In the better grade of cells this loss is reduced to a minimum. A type of wet battery using a solution of caustic soda for an electrolyte, and having zinc and copper oxide electrodes, is GAS, OIL AND STEAM ENGINES 207 extensively used for stationary ignition purposes, and is the most satisfactory type of wet cell for continuous work with this class of engine. The caustic soda battery is of the CLOSED circuit type, and is capable of furnishing a strong uniform current without danger of polarization. The hydrogen bubbles which cause polarization are oxidized or eliminated by the copper oxide electrode as soon as they are formed. The hydrogen combines with the oxygen of the cop- per oxide forming water. The copper oxide is gradually reduced to metallic copper by the reaction with the hydrogen, and in the. course of time re- quires renewal. The copper oxide element is rather expensive and cannot be obtained as readily as the electrodes used in other cells. It will be noted that both electrodes are consumed in the caustic battery, the consumption of the zinc furnishing the current, and the reducing of the oxide furnishing the chemical energy for depolarizing the cell. (81) Dry Batteries. "Dry batteries are by far, the most convenient and economical form of primary battery to use, for there is no fluid to slop and leak, the first cost is low, the output is large for the weight, and last but not least, the cell can be thrown away when exhausted without great monetary loss. This does away with the expense and annoyance of changing wet cells, a factor that will be appreciated by those that are far from a source of chemical supplies. Since the advent of the automobile the use of dry cells has extended so that they may be obtained in almost any country town or village. While the cell is not dry, strictly speaking, the solution is held in such a way that it cannot slop around in the cell nor leak out of the seal. The only fault of a dry cell is its ten- dency to deteriorate with age because of the constant contact of the electrolyte with the electrodes. The negative electrode of the dry cell (zinc) is in the form of a cup which serves as a containing vessel for the electro- lyte and the depolarizer. The electrolyte is usually composed of a solution of am- monium chloride, with a small percentage of zinc sulphate, this fluid being held by some absorbent material such as blotting paper, or paper pulp. The electrolyte is applied to the electrodes by means of the 208 GAS, OIL AND STEAM ENGINES saturated blotting paper, which is also used to line the zinc container, thus providing insulation between the electrodes. A rod of solid carbon which forms the positive electrode is placed in the center of the container, and the space between the rod and the zinc is packed solidly with granulated carbon, the blotting paper lining preventing contact of the zinc with the carbon. Pulverized manganese dioxide is mixed with the granulated carbon for a depolarizer. After the zinc container is filled with the electrolyte and pulverized carbon, the top of the container is closed hermetic- Brookes Four Cylinder Gasoline Engine Direct Connected to Dynamo. ally by means of sealing wax. Granulated carbon is used for it presents a large surface to the electrolyte, reduces the internal resistance of the. cell, and therefore increases the cur- rent output of the battery. As soon as the battery starts generating current, polarization begins, with the liberation of hydrogen gas. If the cell is discharged at a high rate, the manganese dioxide will be un- able to absorb all of the gas, and consequently pressure will be erected within the cell. The greater the rate of discharge, the greater will be the amount of hydrogen set free, and the higher the pressure. If a short circuit exists for any length of time, the pressure of the excess hydrogen will speedily ruin it, as the cell will GAS, OIL AND STEAM ENGINES 209 puff up, or. even burst under the pressure. If the rate of dis- charge be kept so low that all of the gas will be absorbed by the manganese, as soon as generated, the cell will furnish a steady current until the elements of the cell or the electrolyte are exhausted. The steady current limit, or non-polarizing limit is about one-half ampere and if long life of the cell is expected, the cur- rent drain should be less than this amount. A good spark coil will develop a satisfactory spark on a quarter to one-half ampere, so that the demand of a good coil is well within the safe limits of battery capacity. The voltage of the average dry cell when in good condition is 1.5 volts on open circuit. When the cell is old or exhausted, the voltage falls rapidly when any demand for current is made on the cell, and the voltage also varies with the rate of current flow, the voltage decreasing with an increase of .current. As there is not much difference in voltage between a new and old cell when on open circuit, it will be seen that the am- meter giving the current output will give a more accurate de- termination of the condition of the battery. The voltage is in- dependent of the size of cell. The battery showing the greatest amperage is not neces- sarily the best for general use, as cells having an unusually high current capacity are generally short lived. The strong electro- lyte used in high ampere batteries causes them to burn out or deteriorate rapidly when not in use. Under ordinary conditions, a correctly proportioned No. 6 ignition cell should show a current of from fifteen to twenty amperes on short circuit when the cell is new, although higher results may be obtained safely with some makes of cells. While the voltage is the same for all sizes of batteries, and depends on the material used in the construction, the amperes increase with the size of the cell, and the area of the electrodes. If a cell does not show more than ten amperes on short circuit, it should be thrown out and another substituted for it, as the cell is liable to go out of commission at any minute when reaching this point of exhaustion. A small battery testing voltmeter or ammeter should be in the kit of every gas engine operator using a battery for igni- tion, as the exact condition of a vital part of the power plant can be determined quickly and with accuracy. For dry bat- teries an ammeter is preferable; for storage batteries a volt- meter must be used. 210 GAS, OIL AND STEAM ENGINES When buying dry batteries insist on having new, fresh cells, as any battery depreciates in value with age. Never take a cell without testing it, as it is the practice of dealers to work off their old stock on unsuspecting customers. Examine the bat- tery closely for the makers' dates, and if the battery is several months old, it is probable that the electrolyte is dried up or that the electrodes are wasted through long continued local action. As heat stimulates chemical action in the cell, they should be stored in a cool place to retard the wasting action as much as possible. Under all conditions, the cell should be kept dry, since the moisture that is deposited on the cell forms a closed circuit for the current which soon exhausts the battery. Cold retards chemical action in the cell and consequently re- duces the output in zero weather to such an extent that start- ing is frequently impossible. Multiple cylinder engines exhaust a battery quicker than those with a single cylinder, as there are more current impulses in a given time and consequently more current is used. A bat- tery may be compared with a bottle that holds a certain quantity of fluid. If the water is allowed to drip out slowly it will last for a long time, but if allowed to flow in a continuous stream will soon be exhausted. With badly designed or poorly adjusted spark coil, the de- mand on the batteries is greater than with one that is in proper condition. An engine that runs continuously exhausts a battery faster than one that is run at long intervals. Always open the battery switch when the engine is to be idle for any length of time, as the engine may have stopped with the igniter in con- tact, allowing the battery to expend its energy uselessly. Test batteries immediately after a run, as the batteries will recover after standing a while, and will show a fictitious value. A weak, partially exhausted battery will cause a poor spark that will result in misfiring or a loss of power. It is poor economy to attempt running an engine on a weak battery. An engine may run on a weak battery for a short time, and then gradually decrease in speed until it conies to a full stop. Mis- firing is generally in evidence as the engine dies down. In case of an emergency, weak batteries may be made to run an engine of an automobile or boat to its destination, by stopping the engine frequently and allowing the batteries to recuperate during the idle periods. A battery that is temporarily weak- ened by hard service or by a temporary short circuit will usually revive or partially recover its strength if allowed to "rest" for GAS, OIL AND STEAM ENGINES 211 a short time until the hydrogen is absorbed by the depolarizing material. The life of a dry cell can be extended for a few hours by punching a hole in the sealing wax on the top of the battery, and pouring water, or a solution of water and sal- ammoniac into the cell. This will reduce the internal resistance and increase the current. The batteries will run under these conditions for a short time only, and new cells should be pro- cured at the earliest possible moment. No old cell can be made as good as new by any method. Never drop the cells on the floor nor subject them to hard usage mechanically, for if the active material is loosened, the current output will be reduced. A short circuit through a closed switch with the engine stopped or a loose dangling wire will put the cells beyond repair. If the binding screw on the carbon electrode does not make good contact with the carbon, tighten it to decrease the re- sistance. Fasten the connecting wires firmly under the bind- ing screws and keep the connections clean. In the absence of an ammeter, a rough estimate of the con- dition of the cell may be made by fastening a short wire tightly in the zinc binding post, and touching the carbon surface lightly and intermittently with the free end of the wire. When contact is made with the free end of the wire, a small puff of smoke will arise and a red spark will be seen if the cell is in good condition. Sometimes the contact made on the carbon will produce only a small black ring on the surface of the electrode. This indi- cates a battery that is nearly exhausted, and one which is good for only a few more hours of service. When a number of cells are connected together in such a way that they collectively form a single source of current, the group is called a battery, and the resulting voltage and am- peres of the group depends on the way in which the cells are interconnected. It is possible to connect the cells of a battery in such a way that total voltage of the group or battery is equal to the sum of the voltages of the individual cells. A battery connected in this manner is said to be connected in series. While the volt- age of a battery is increased, by series connection, the number of amperes is the same as that given by a single cell, the same current flowing through the set. (82) Series and Multiple Connections. Fig. 86 shows the cells connected in series, the carbon ter- minal of one cell being connected to the zinc terminal of the 212 GAS, OIL AND STEAM ENGINES second. The carbon of the second cell is connected to the zinc of the third, and so on throughout the series, the two remaining terminals of the battery being connected with the ignition circuit. The number of watts or power developed by the group is equal to the sum of the outputs of the separate cells. If the voltage of each cell shown in diagram % is 1.5 volts, the total voltage of the group of five cells will be 1.5X5 = 7.5 volts, and if the current of a single cell is 15 amperes, the current output of the group will be 15 amperes, or the same as that of a single cell. Almost all ignition appa- ratus now on the market requires six volts for its operation, so with cells having a voltage of 1.5 volts such apparatus would call for four cells in series, as 6 -f- 1.5 = 4. Owing to the increase of internal resistance caused by series connections it is usual to add one more cell than is theoretically required, making a group of five cells to supply the six volts Fig. 86. Five Cells in Series. required. A large number of cells will give a hotter spark than a smaller, but the excessive current causes the contact points^ of the igniter or vibrator to burn off rapidly and also hastens the destruction of the cells themselves. Batteries connected in such a way that the total amperes of the group is increased without increased voltage are said to be connected in multiple or parallel. When batteries are connected in multiple, the total current in amperes is equal to the sum of the amperes delivered by the separate cells; and, while the current in amperes is increased by multiple connection, the voltage of the group remains equal to that of a single cell. If each cell connected in multiple has an electromotive force of 1.5 volts, and can deliver 15 amperes, the total current de- livered by this system of connection will be 15 X 5 = 75 amperes with five cells, and the electromotive force will be 1.5 volts as in the case of the single cell. By connecting batteries in multiple, the resistance is reduced, allowing a maximum flow of current. The demand on the individual cells is reduced by multiple GAS, OIL AND STEAM ENGINES 213 connection, as each cell only furnishes a small part of the total current. The greater the number of cells, the less will be the current required per cell, with a given total current. As the life of a battery depends entirely upon the rate at which it is discharged, it is necessary, for economical reasons, to keep the current per cell as small as possible, therefore the multiple system would prove of value as it reduces the load to the small- est possible limit. Enough cells should be placed in multiple to reduce the current to less than a quarter of an ampere per cell. The cells shown will not have sufficient voltage to oper- ate ordinary ignition apparatus requiring a potential of six volts, hence the multiple system must be modified in order to have an increased voltage, and at the same time secure the advantages of multiple connections. (83) Multiple-Series Connections. A compromise is affected by the multiple series system of con- nections in which are combined the advantages of both the series and multiple systems of connection. This arrangement allows sufficient voltage to operate 6 volt apparatus and at the same time reduces the rate of discharge on the individual cells. The series-multiple battery shown in the diagram 88 consists of four groups of batteries connected in multiple, each group of which consists of five cells that are connected in series. The current and voltage in the various branches is shown in the diagram. The series-multiple system is adapted for use with multiple cylinder engines, as engines with more than one cylinder cause a severe drain on the igni- tion system. Arranging the series groups in parrallel increases the life and efficiency of the cells. If an efficient coil is used, the drain of a single cylinder is not too great to be met with a single set of series cells. If possible the set should be pro- vided with a duplicate, so that the load could be transferred from -one set to the other at proper intervals by means of a double throw switch. With a single set of batteries in series the working life of the cells will be approximately twenty hours under ordinary conditions. With four groups of four cells in series, the life of the cell will be approximately 160 hours, or eight times the life of the single set under similar conditions. While the cost of the cells will be only four times that of the single set, it will be seen that the cost of battery upkeep is halved by reducing the demand on the cells. 214 GAS, OIL AND STEAM ENGINES Sometimes duplicate sets of series multiple connected bat- teries are used for heavy duty engines, the engine running on one set for a while and then on the other, allowing the first set to thoroughly recuperate before it is again thrown in service, by means of the double throw switch. When batteries are multiple or series-multiple connected they should be of the same size and make. and of the same voltage. If the cells are of different voltages useless local currents will circulate among the cross-connections, shortening the life of the battery and reducing the output. Fig. 88. Cells in Multiple Series. In connecting a dry cell use a good grade of rubber insulated wire, preferably wire with a stranded conductor, as it is less liable to break or loosen at the binding screw of the battery. Carefully remove the insulation from the end of fhe wire that is to be fastened under the binding screw of the battery. Scrape it until it is bright and perfectly free from dirt before fastening it in the battery terminal. Never allow a dirty or corroded connection or a loose wire to exist. An open battery circuit or loose connection will stop engine suddenly, or will prevent starting. The battery connections should be screwed down tight with the pliers, care being taken that the screws are not broken by GAS, OIL AND STEAM ENGINES 215 the tightening process. See that frayed ends of the wire do not project beyond the binding screw to which they are con- nected and make contact with other cells or metal objects. Be sure that no insulation gets between the contact braces of the binding screw. (84) Operation of Dry Cells. The following hints should be observed to obtain the best results with dry cells. (1) Never remove the paper jackets from the cells. (2) Never lay tools or other metallic objects on top of the cells for this will cause a "short" that will quickly exhaust them. (3) Do not connect old and new cells together, especially with the multiple-series system of connections, for the old cells will limit the output of the new, or else will cause cross-cur- rents that will exhaust all of them. (4) When trouble developes in the battery, test each cell separately and remove the faulty cells. Do not reject all of the battery because of one or two dead cells. (5) Place the cells in a wooden box that will protect them from dirt or moisture, and if possible divide the box off into pigeon holes with a cell in each hole. For the best protection against moisture, the box should be boiled in paraffine. (6) Provide a battery switch on the box that will cut both leads from the cells completely out of circuit when the en- gine is stopped. (7) Never place a dry cell in a box that has contained stor- age cells unless the box has been thoroughly washed out, for the residual acid of the battery will destroy the zinc elements. (8) Make all connections firmly with well insulated wire and take care that the wire does not make contact with any part of the battery except that to which it is connected. (9) Keep the battery dry. (85) Storage Batteries. The purpose of the storage battery is to store or accumulate the current generated by a dynamo until so that the current will be available when the dynamo is not running. A storage cell does not "store" current in the same way that water is held in a tank, but returns the energy expended on it through the chemical changes caused in the cell by the current. When the charging current passes through the storage bat- tery chemical changes are produced in the electrodes and 216 GAS, OIL AND STEAM ENGINES electrolyte, and the energy expended on the cell is in the form of latent chemical energy, in which state it remains until the electrodes are connected with one another by a wire or some other conducting medium. When the electrodes are connected through an external circuit, the electrolyte acts on the elec- trodes causing them to assume their original composition. As they pass into their previous chemical condition the latent chem- ical energy is converted into electrical energy. The current thus produced may be used in the same way as in a primary cell. When discharging, the action of a storage battery is similar to that of a primary battery, the current being produced by the action of a fluid on two dissimilar electrodes. Instead of sup- plying new elements when the battery is discharged, as in the case of the primary cell, the elements are brought back to their original state by passing a current through the cell in the oppo- site direction to that of the discharge. There are several combinations of materials which may be used in the making of storage battery electrodes and electro- lytes, but with the exception of the lead sulphuric battery and the new Edison battery none have proven a commercial suc- cess. The most common type of storage or secondary cell is the lead-sulphuric type in which the electrolyte is dilute sulphuric acid and the electrodes are lead plates, covered with a chem- ical composition known as the active material. These plates usually consist of a lead grid', or lattice frame -in the pockets of which is" pasted the active material. The pockets or lattice bars of the plates are for the purpose of supporting the active material which is of a weak and spongy nature. The active material on the positive plate is usually litharge, while that on the negative plate is red lead. After charging, the active material on the positive plate is changed to lead peroxide by the action of the current, and the active material on the negative plafe is changed into spongy metallic peroxide. The composition of the active material on the plates determines the direction of flow of the discharge, or secondary current. The current flows from the positive plate to the negative through the external circuit. When fully charged, and in good condition, the positive and negative plates may be readily distinguished by their colors, the positive plate being a dark brown or chocolate color, and the negative a slate or grey color. GAS, OIL AND STEAM ENGINES 217 The positive active material is hard, while the negative may be easily cut into by the finger nail. The density of the ma- terial changes slightly with the charge, as the material ex- pands during the discharge. The problem of holding the active material securely to the plates during expansion and contraction has been a hard one to solve, each manufacturer having some favorite form of grid or material plug to which he pins his faith. While great im- provements have been made in this direction, it is certain that we have not yet reached perfection. Loose active material will cause short circuits and will reduce the output of the cell; loose active material frequently ruins a cell. The current capacity of a storage battery depends on the area of the plates or electrodes, and in order to increase the capacity of a battery, and consequently the area, it is usual to use a number of plates connected in parallel. A number of small plates of a given area are to be preferred to two large plates of the same area, as the battery will be of a more con- venient size. Customarily there is one more negative plate than positive, so that the extreme end plates in a cell are negative, as the positive and negative plates alternate with each other when as- sembled. An ignition battery usually consists of two negative plates and one positive. Cells used for power purposes have as high as sixty plates. A single cell of storage battery should show about two volts when fairly well charged. It more than two volts are desired more cells should be connected in series. The total voltage will be equal to the number of cells, in series, multiplied by the voltage per cell. The voltage per cell should never be allowed to drop below 1.7 volts, as the cell is likely to be destroyed when operated with a low voltage. Recharge as soon as the voltage drops to 1.8 volts. The ordinary six volt ignition battery consists of three separ- ate cells connected in series, which are encased in one protecting box. The plates are prevented from touching each other within the cell by means of a perforated sheet of hard rubber that is in- serted in the space between the plates. The perforations allow the liquid to circulate between the plates. The storage battery is furnished as standard equipment with several well known gas engine builders, and its use is advocated by nearly all. When used in connection with a low tension 218 GAS, OIL AND STEAM ENGINES direct current magneto two independent sources of current are at hand, either of which will ignite the engine in an emergency. With the magneto-storage battery combination, it is possible to obtain a few small lights at any time, whether the engine is running or not, and the engine is always ready to start on the first "over" with the storage battery and a good mixture. If a magneto is not used, difficulty is sometimes experienced in obtaining a suitable source of charging current, as many localities do not possess direct current plants. Batteries may be charged from the direct current exciter in an alternating current station, or may be charged by an alternating current rectifier such as is used by automobile garages. The principal objections to the storage cell are: inconvenience of charging; sulphating of cell when standing without a charge; ease with which the cell is ruined by short circuits; the damage caused by the spilling of the electrolyte; and the fact that the cell gives no warning of failing or discharged condition. Since the composition of the plates depends on the direction in which the current flows through the cell, it is obvious, that an alternating current which periodically changes its direction of flow will first charge the plates and then discharge them al- ternately. The result of an attempt at charging with alternating current would be that the plates would be in the same or a worse condition in a short space of time than they were at the beginning. In charging a storage cell care should be taken to determine the character of the current, especially when the cell is to be charged from a magneto. When under charge, the cell is connected to the charging circuit in such a way that the current flows backwards through the cell or in a direction opposite to that when the cell is discharging. (86) Care of the Storage Cell. The storage battery should never be left in an uncharged condition with the acid electrolyte in the cell, for the solution will quickly attack the uncharged plates and combine with them to form lead sulphate. As lead sulphate has a high electrical resistance and is insoluble in the electrolyte the sulphate coat- ing will reduce the output or if present in excess, ruin the cell. The sulphate appears as a white coating on the surface of the plates. The only remedy for this condition at the hands of the average engine operator is a prolonged charge, or over charge, at a slow rate. There are several chemical processes but they are too complicated for the average man. GAS, OIL AND STEAM ENGINES 219 As sediment collects on the bottom of the battery jars, and is liable to cause a short circuit, the plates should be held about half an inch from the bottom of the jar. Care should be taken that the cells of the stationary type of battery are kept dry and clean. Do not allow dirt to drop into the solution as it is liable to destroy the cell. A volt meter should be used to determine the condition of the battery, and should be used frequently. An ammeter should never be used on a storage battery, as it is of very low resist- ance, and would probably cause a rush of current that would destroy both the battery and the instrument. Never short circuit a storage battery, even for an instant, as excessive current will cause the plates to buckle, or will loosen the active material on the plates. The plates are immersed in the electrolyte, which should cover the entire plate or active surface. If the solution does not cover the plate, the capacity of the cell will be reduced. Plates that are partially covered with solution deteriorate rapidly from "sulphating." This is caused by the air and acid acting on the damp inactive portion of the plate. Usually the electrolyte consists of a dilute solution of sul- phuric acid and water, but in some ignition cells the solution is "solidified" by some substance to about the consistency of table jelly. The object of this thickened solution is to prevent the solution from slopping and leaking when the battery is being transported. The solution used in a storage battery is exceedingly corrosive in its action, and if spilled on metal or wood will destroy it immediately. Care should be taken in handling the electrolyte. A cell should never be discharged below 1.7 volts for below this point, the plates are likely sulphate. When the solution is replaced by fresh, or water is added for the purpose of restoring the electrolyte to its original level, use only distilled water, free from metallic salts and suspended matter. Many people "test" their cells by snapping a wire across the terminals to "see if there is a good spark." Nothing could be more injurious to the battery, and as this test indicates nothing, the practice should be discontinued. Make all your tests either with a hydrometer or a voltmeter, the latter is preferable in the average case. The electrolyte is a solution containing approximately 10% of chemically pure sulphuric acid and 90% of distilled water. The specific gravity of the fluid should be from 1,210 to 1,212 220 GAS, OIL AND STEAM ENGINES in all cases. A standard battery hydrometer should be used by all storage battery users to ascertain the exact density of the solution as the specific gravity is a direct index to the condition of the cell. A gasoline hydrometer is useless for a storage battery. When mixing the electrolyte it should be placed in a glass or porcelain jar, and the process should never be performed in the battery jar in the presence of the plates. The solution is very active chemically and should not be brought into contact with metallic or organic substances because of the danger of contaminating the fluid. The acid should always be poured into the water in a thin stream while the mixture is being stirred with a glass or porcelain rod. Pouring the water into the acid is likely to produce an explosion and should therefore be care- fully avoided. As the acid heats the water during the mixing the hydrometer reading should not be taken until the heat caused by the first addition of acid has been reduced to that of the room. Taking a reading with a hot solution will give inaccurate results, un- less, of course, the reading is reduced to normal by the method described in a previous chapter. When the reading has been taken and found to be correct and the solution has been re- duced to the temperature of the room, the electrolyte may be poured into the cell through the filler openings in the top of the cell. Pour into each cell sufficient fluid to cover the plates but avoid filling the cell to the top, or flooding it. At the end of the charging time given by the maker, with- draw a sample, of the electrolyte by means of a syringe and test the specific gravity. This should not be over 1,290 fof a fully charged cell, and if the solution exceeds this amount, pure water should be added until the proper point is reached. Al- ways correct the specific gravity in this way every time the battery is charged as evaporation and internal chemical changes cause the density to change from time to time. The voltage of a good storage battery will be about 2.1 volts when fully charged. Overcharging is wasteful and finally destroys the cell, the effects being similar to those caused by excessive dis- charges, that is, buckled plates and loosened active material. Overcharging a sulphated battery may cure the trouble, a little overcharging at intervals being better than a long con- tinued overcharge. An increase in the specific gravity of the electrolyte of from GAS, OIL AND STEAM ENGINES 221 30 to 50 degrees, with a corresponding rise of voltage, shows that the cell is fully charged. After the charging is completed remove all of the solution spilled on the battery, preferably by washing, and wipe bone dry. If the solution is higher in the air, remove the excess with the syringe. i (87) Make and Break System (Low Tension). When a circuit carrying a current is opened or broken at any place in its length, an electric spark will occur at the point at which the wires or contacts are separated. This is due to what might be termed the "momentum" of the current which causes it to persist in its course even to the extent of jumping over a short distance of the highly resistant air in the gap. The size and heat of the spark may be increased by placing a coil of copper wire in series with the circuit that has an iron core in the center of the turns. This coil increases the tendency of the current to jump the gap, or in other words in- creases the momentum of the circuit. Each separation of the terminals of the circuit causes but a single spark, so that in order to obtain another the terminals must be again brought into contact and the current reestablished in the circuit before the circuit is again opened. Thus the func- tion of the make and break igniter is to alternately make and break the circuit in the presence of the combustible mixture. To obtain the greatest spark and most certain ignition, the con- tact points should be opened with the greatest possible speed, an action that is accomplished in the actual engine by springs and triggers. A typical cylindrical make and break coil consisting of an iron wire core surrounded by a coarse copper wire core is shown by Fig. 91. At one end of the coil will be seen the two terminal screws by which it is connected with the circuit. Another make and break coil is shown by Fig. 92, which has the same type of winding, but differs in having the core wire coil extended beyond the winding and heads. By closely exam- ining the cut, the iron wires will be seen in the projecting core tube at the left end of the coil. A flat base is also provided for fastening it to a stationary foundation. A typical make and break igniter is shown by Fig. 93, to- gether with the usual circuit consisting of a primary coil and battery. In this figure, A and C are the two electrodes pro- vided with platinum contact points N and O respectively. The 222 GAS, OIL AND STEAM ENGINES electrode A is stationary and is insulated from the iron casing K by the insulating washer H, and the insulating bush- ing or tube I. The electrode C is oscillated intermittently by the engine through its shaft E, and the trigger G, the springs S serving to snap the platinum contact O away from N at the proper moment. This electrode (C) is in electrical con- Fig. 91. Kingston Cylindrical Make and Break Coil. nection with the shell K, and the engine frame at all times, and is provided with a brass bushing F for a bearing surface. The outer containing casing K is bolted to the combustion chamber, of the engine by the bolts LL, so that the electrodes A and C project into the combustion chamber. Fig. 92. Kingston Make and Break Coil. Short Type. Current from the battery R passes through the coil winding P to the coil terminal U from which it passes from V to the igniter binding post J. From J it flows along the rod D to the stationary electrode A. Since the rod D is surrounded by the insulating washers and tube H, T and I, the current can- not escape directly to the casing K. With the two platinum points N and O in contact, the current flows through C to the shell K from which point it flows back to the battery R through the conducting path V, completing the circuit. The greater GAS, OIL AND STEAM ENGINES 223 portion of the path V consists of the engine frame. When the electrode is moved in the direction of arrow B, the current is opened and a spark occurs at the point of separation M, in con- tact with the gas in the combustion chamber. The electrode C being connected with the engine frame is said to be "grounded." If the stationary electrode A were not insulated from the casting K, the current would pass directly from the terminal J back to the battery R without passing through the contact points at all, and consequently no spark would be pro- duced on the separation of the points. Fig. 93. Diagram of Igniter and Connections. A push rod which is actuated by a cam on the engine, en- gages with the trigger G, and causes the spark to occur when the piston is on the end of the compression stroke. In nearly all engines, the relation between the time of the spark and the piston position can be regulated to suit the requirements for advance and retard. This adjustment is necessary in order that the spark may be varied to meet the difference between the starting and running requirements. While the ignition should be considerably advanced while running, it is necessary to retard it when starting, as the engine is liable to "kick back" with an advanced spark. This advance and retard device should be accessible while the engine is running, and the operator should be able to control 224 GAS, OIL AND STEAM ENGINES the point of ignition at all times. Many men have been seriously injured by the lack of this device or by neglecting to use it. The contact points make contact only for a short time be- fore the spark is required in order to reduce the amount of cur- rent to the minimum, and therefore increase the life of the batteries. The duration of the "make" or contact should be as short as possible. Prolonged contact weakens the batteries and causes them to run down rapidly. For the same reason the electrodes should remain separated until the make is actually required. A certain period of contact is necessary, however, to allow the spark coil to ''build up," but with a properly designed coil the time required is very short. Some engines provide a device that cuts out the ignition current altogether during the idle strokes. This adds materially to the life of the batteries. The igniter should be located near the inlet valve, as the cold incoming gases tend to keep it cool and clean, besides insuring the presence of combustible gas around the igniter electrodes. Improper placing of the igniter will greatly reduce the efficiency of the engine. Avoid placing the igniter in a pocket, or in the path of the exhaust gases. The make and break ignition system has many good features, but cannot successfully be applied to, engines running over 500 revolutions per minute, nor can it be applied to engines of less than 3 H. P. as the parts would be too small and delicate to be durable. The make and break igniter produces the largest and "hottest" spark of any type of ignition, and is especially derirable for large or slow running engines. Being operated at a low volt- age, it is not as easily affected by moisture, poor insulation, or dirt as the high tension or jump spark system, nor is it liable to give the operator such a violent "shock." Engines governing by the "hit and miss" system have a device that cuts out the current during the "missed" power strokes. This effects a considerable saving in battery current, especially on light loads when the engine misses a great num- ber of strokes. While possessing many points of merit, the make and break system is open to several serious objections: 1. Due to the high combustion temperature there is excessive wear of the working parts in the cylinder, this wear causes a change in the ignition timing. GAS, OIL AND STEAM ENGINES 225 2. The low voltage used in the make and break system calls for perfect contact of the electrodes in the cylinder. This con- tact is often interfered with or entirely prevented by the accu- mulation of carbonized oil and soot deposited on the surfaces. 3. The wear of the operating spindle or shaft, which passes through the cylinder wall causes leakage, which in turn causes a loss of compression in the cylinder. 4. The wear of the external operating mechanism produces a change in the timing. The edge of the fingers, wiper blades, etc., tend to cause an advance in the ignition as a general rule, with the attendant danger of broken crank shafts. 5. The system is mechanically complicated, correct operation calling for constant care as to adjustment. All ignition apparatus wears in the course of time and changes the timing of the engine. The electrodes and push-rods wear and require readjustment. Generally the tendency of worn parts is to advance the ignition. This change in timing occurs so gradually that the operator does not notice it until the en- gine begins to pound, or until the efficiency has been consider- ably reduced. When the engine is new it is well to mark the ignition mechanism in such a way that the relative positions of the crank and igniter will be shown at the time when the igniter trips. It will then be possible for the operator to refer to the marks at any time to tell whether his ignition is occurring at the proper time. Always mark the half-time gears when tak- ing the engine apart for the difference of one tooth when reassembling will be sufficient to throw the engine out of time. The usual method of marking the gears, is to center punch, or scratch one tooth on the small gear, and then mark the two teeth of the large gear that lie on either side of it. With these marks it is possible to replace the gears in their original and proper positions. The igniter should trip, causing the electrodes to separate just before the end of the compression stroke is reached, or just before the crank reaches the inner dead center. The dis- tance lacking the exact dead center represents the instant of time between the time of ignition and the actual pressure es- tablished by the combustion. As most engines have the ignition considerably retarded when starting, the igniter will trip later with the lever in the "start" position than when in the "running" position. Never fail to retard spark when starting nor forget to advance it when engine is up to speed. 226 GAS, OIL AND STEAM ENGINES The actual advance given to an engine depends on" the char- acter of the fuel and on the speed. An engine is said to have an advance of 10, if the crank lacks 10 of having made the inner dead center at the time of ignition. The most economical point of ignition is easily determined when the engine is running on a steady load, by varying the point of ignition and noting the position assumed by the gov- ernor. (88) Operation of the Make and Break Igniter. To keep the igniter in order, and to obtain the best results with the least trouble, the following hints should be observed: (1) Clean the igniter frequently, and remove all deposits of oil and carbon. For cleaning, the igniter must be removed from the cylinder, care being taken to avoid injury to the pack- ing or gasket. Graphite dusted on the gasket will prevent it from sticking to either the igniter or cylinder. (2) If the contact points are rough, pitted, or covered with a carbon deposit, the scale should be removed, and the points smoothed down with a fine file, taking care that the two faces are filed parallel with one another. (3) Insulating washers and tubes should be removed and washed in gasoline. The hole through which the igniter rod passes should be scraped free from any deposit for much trou- ble can be caused by a tight working shaft. (4) Examine the hole or bushing through which operating spindle passes, for wear. A worn spindle or bushing may cause a serious loss of compression; replace worn bushing at once. See that the insulation of the stationary electrode is not broken. If it is injured in the slightest degree, replace it with new. (5) Often the sparking points may be cleaned temporarily without removing the igniter from the cylinder by pulling upon the outside finger or trigger until the points come together, and then pushing in towards the cylinder several times on the movable electrode, which slides them one on the other, scrap- ing off the deposit. This method is only a make shift. (6) After removing igniter, replace all wires, screwing them firmly into place. The ends of wires and connecting screws should be perfectly clean when the conection is made; to insure perfect contact, the surfaces should be scraped or sand-papered until bright and shining. See that no foreign matter of any GAS, OIL AND STEAM ENGINES 227 kind gets between the wires and the metal of the binding screws. Wherever possible connections should be soldered. (7) A small coil of the wire should be made at the point of connection; i. e., the wire should be a trifle longer than neces- sary to reach the binding screw, the excess wire being coiled up on a pencil. This coil allows of removing igniter, allows for broken wire ends and reduces the tendency to loosen the con- nection. (8) Ground wires, or wires connected with the frame of the engine should receive careful attention. They are generally fastened under some screw or bolt on the engine which may become loose or fail to make contact, thus opening the entire circuit and causing the engine to stop. The ground wires are generally connected in inaccessible places, and require all the more attention for this reason. (9) For the primary of low tension wiring, use only the best grade of stranded rubber covered wire. A special wire for igni- tion purposes is on the market. It is rather expensive but is just the thing for the service. Never use cotton covered or waxed wire. This covering af- fords absolutely no protection against moisture or abrasion. (10) As the voltage of a primary circuit, or circuit for make and break is very low, and the current comparatively high, it is well to have the copper as large as possible. It should never be less than number 14 gauge. Don't use solid wire if you can obtain stranded conductor. (Stranded wire is made up of a number of fine wires which are twisted into a cable or rope of the desired size.) (11) Oil destroys rubber insulation and should be kept off the wiring. Try to locate the conductors so that they will be out of range of oil thrown by the moving parts. (89) Jump Spark System (High Tension System). Due to its simplicity and the light weight of its moving parts, the high tension ignition system is applied to practically all small, high speed engines running 500 R.P.M. or over. The high tension system is also desirable from the fact that it has no moving parts in the cylinder of the engine. The principal objection to the high tension system is the ease with which the high voltage current leaks or short circuits, moisture being fatal to the operation of a jump spark engine. Instead of producing the spark by breaking the circuit of a low tension current, the spark is produced by increasing the volt- 228 GAS, OIL AND STEAM ENGINES age to such a point that the current will jump directly across a fixed gap. To cause the current to jump through the air requires an extremely high voltage, and as the battery current is very low it is necessary to introduce a device known as a "transformer" to stop the current up to the required tension. In addition to the voltage required at atmospheric pressure (about 50,000 volt per inch of spark) we must also furnish suffi- cient pressure to overcome the increased resistance due to the compression in the cylinder. Unlike the spark coil used on the low tension make and break system, the induction coil or transformer coil has two separate and distinct coils, that are thoroughly insulated from each other. One coil has a few turns of heavy copper wire which is called the primary. The other consists of many thou- sands of turns of very fine copper wire, and is called the sec- ondary. Both coils are wound around a bundle of soft iron wire called the core, from which they are carefully insulated. When a battery or magneto current flows through the primary coil, the core is magnetized, and throws its magnetic influence through the turns of the secondary coil. In Fig. 94 the primary coil and the low tension battery and magneto circuit are represented by heavy lines. The second- ary coil, and high tension circuit are represented by light lines. In order to obtain a continuous discharge of sparks it is necessary to make and break the current in the primary coil very rapidly. This is done by means of the interrupter or vibrator, which is indicated in the diagram by V. The inter- rupter consists ordinarily of a spring A on which is fastened a soft iron disc D and a platinum contact point B. When the core is magnetized it attracts the iron disc D which is pulled toward the core, bending the spring A and breaking the con- tact between the platinum point B and C. When the contact points are separated, and the current broken, the core loses its magnetism, and the spring assumes its normal position, which brings the platinum points B and C into contact once more, and reestablishes the current through the primary. The core is again magnetized and the primary current is again broken, and so on. This make and break of the current is thus accom- plished automatically, the current being broken many thousands of times per minute, the vibrator moving so fast as to cause a continuous hum. As soon as the current starts flowing, the magnetic force spreads out through the secondary coil and threads through the GAS, OIL AND STEAM ENGINES 229 turns of which it is composed. The instant that the current ceases, the magnetic force decreases and the turns are again threaded by the magnetic field on its return to the core. Thus two magnetic waves are sent through the secondary coil, one when the circuit is "made," and one when the circu is "broken." When a magnetic wave threads or spreads through the tun of a coil of wire, a current of electricity is generated in the co the quantity and pressure or voltage of which is proportion 230 GAS, OIL AND STEAM ENGINES to the intensity of the magnetism, and to the number of turns of wire in the secondary coil. Thus it will be seen that at every make and break of the low tension current in the primary coil, a current is generated in the secondary. As the voltage generated in the secondary is roughly proportional to the number of turns in the secondary, and as there are many thousands of turns, it is evident that the voltage in the secondary will be very high. Thus by the use of the induction coil, the low tension battery current is transformed into a high tension current of sufficient voltage to break down the high resistance of the spark gap. The condenser is shown at L which has one wire leading to the vibrator spring A, and one wire to the contact screw M. The function of the condenser is to absorb the spark produced at the vibrator points so that the break is made quickly, produc- ing a maximum spark. The intensity of the spark depends upon the quickness with which the primary current is broken, and if it were not for the condenser the length and intensity of the spark would be greatly reduced. This device consists of alter- nate layers of paper and fin foil, every other leaf of foil being alternately connected to the vibrator spring and to the con- tact screw. A method of using two independent sets of battery is shown in the diagram, so that either set may be thrown into circuit by means of the double throw switch O. When handle J is in contact with E, the current of battery set H flows through the coil as shown by the arrows. When J is in contact with F, the battery C is thrown into circuit. The spark gap is shown by X, which represents the spark plug in the cylinder. In practice, the portion of the circuit shown by I-U is gen- erally formed by the frame of the engine, or is grounded. The terminal P of the high tension circuit is always grounded through the threaded shell of the spark plug, the grounded circuit being shown by the dotted lines. Grounding saves wire and many connections, for with P and U connected to ground it follows that one binding post will serve the place of one high tension and one primary post, making .three coil connections instead of four. In order that the spark will occur in the cylinder of the engine at the proper time, a switch must be placed in the pri- mary circuit of the soil, that will open and close the circuit at proper intervals. Such a switch is called a timer, and is always driven by the engine. The timer is connected to the GAS, OIL AND STEAM ENGINES 231 engine shaft in such a way that contact is made at, or slightly before, the time at which the explosion is required, and as soon as possible after spark occurs the current is cut off. For multiple cylinder engines it is usual to provide one coil for each cylinder, the primaries of which are controlled by a single timer and battery. A high tension wire from each coil runs to the corresponding cylinder. Instead of having a num- ber of coils with a battery system, there are two or three makes that operate with one coil in combination with a special de- vice known as a distributor which controls the high tension current. The high tension distributor directs the current to the proper cylinder that is in the order of firing, the timing being performed by a timer similar to that used with multiple coils except that a single contact sequent is supplied. (90) Vibrator Construction. Since the efficiency of the high tension coil depends largely on the construction and efficiency of the vibrator, the different coil makers have developed various types of vibrators that differ Fig. 95. Kingston Vibrator. greatly from the simple device shown in the coil diagram in details. The main objects in view in the construction of a successful vibrator are: 1. To reduce the weight of the moving part as much as pos- sible in order to increase the speed of vibration, and to make the trembler instantly responsive to the timer. 232 GAS, OIL AND STEAM ENGINES 2. To cause the contact points to separate as rapidly as pos- sible in order to cause the maximum spark. 3. To have the contacts as hard and infusible as possible to resist wear and the action of the spark between the contacts. 4. To make any adjustments that may be required, due to wear, as simple and accessible as possible. The types of vibrators are legion, and we have not the space to go into the details of all the prominent makes, but will illus- trate and describe two well known types. The Kingston vibrator made by the Kokomo Electric Com- pany, is a good example of a modern vibrator and is shown in detail by Fig. 95. All adjustments between the contact points are made by means of the contact screw A which carries a platinum point at its inner end. The retaining spring D keeps the contact screw from being jarred out of place by the engine vibration, without the use of lock nuts. Turning A against the vibrator, the tension of the spring B is increased, raising the creases the length and heat of the spark, and also increases screw decreases the tension. Increasing the tension screw in- the current consumption. At N is a separate thin iron plate which is acted on by the magnetized core, a rivet fastening the plate to the main vibrator spring is shown at the end of the spring. The current enters through the lug C, and from this point the circuit is the same as shown in the coil diagram. (91) Operation of the Jump Spark Coil. The spark produced by a coil in good condition should be blue-white with a small pinkish flame surrounding it, when the gap is y$ of an mcn or l ess - The sparks should pass in a con- tinuous stream with this length of gap without irregular stop- ping and starting of the vibrator. Coils giving a sputtering, weak discharge that causes sparks to fly in all directions are broken down and should be remedied. The secondary windings of coils are often punctured or broken down by operating the coil with the high tension circuit open, or by trying to cause long sparks by increasing the spark gap over ^ of an inch in the open air. Coils are also broken down by allowing excessive currents to flow in the primary coil. Never cause a spark to jump over ^ of an inch. High compression in the cylinder shortens the jumping dis- tance of a high tension spark. Coils that will cause a stream of sparks to flow across a gap of ]/ 2 an inch in the open air are often unable to cause a single spark to jump a gap of 3*2 GAS, OIL AND STEAM ENGINES 233 of an inch under a compression of 80 pounds per square inch in the cylinder. Remember that a hot spark causes rapid combustion, and will fire a greater range of mixtures and "leaner" charges, than a straggling, thin, weak spark. Spark coils that give poor results with a long spark gap under high compression aTe often benefited by the shortening of the spark gap. Shortening the gap will increase the heat of the spark, and will insure the passing of a spark each time that the timer makes contact. A good coil should have no difficulty in igniting a piece of paper inserted between the wires forming the spark gap in the open air. Fig. 96. Kingston Dash Coil. The adjusting screw affords a means of increasing or de- creasing the tension of the vibrator spring, and the amount of battery or magneto current flowing through the primary coil. Increasing the tension of the spring requires stronger magnetiza- tion of the core to break the circuit of the contact points. This in turn calls for more current from the battery; hence in order to lessen the demand for current on the battery, the tension should be as little as possible to obtain the necessary spark. An increased tension produces more spark as the magnetization of the core is increased, but for the sake of your batteries de- crease the tension as much as possible with a satisfactory spark. Almost all operators have a tendency to run with too stiff a vibrator, and hence use too much current. An efficient coil should develop a satisfactory spark with l / to ^ of an ampere of current in the primary coil. I have often found coils that would work well with ]/ 2 ampere, that were screwed up so tight that the coils were consuming 4 to 5 amperes or 8 to 10 times as much as they should. 234 GAS, OIL AND STEAM ENGINES A battery ammeter used for testing the current consumed by coil will save its cost many times over in batteries and burnt points if used at frequent intervals in the primary circuit. An automobile or marine engine should be tested for vibrator adjustment in the following way: Adjust vibrator so that spring is rather stiff. Start engine and get it thoroughly warmed up and running at full speed, then slowly and gradually decrease the tension of the spring until misfiring starts in; then slowly increase tension until misfiring stops. Increase the tension no farther; this is the correct ad- justment. Poor vibrator adjustment is the cause of much trouble and expense as it uses up the batteries and wastes fuel. The prin- ciples of correct adjustment are simple, the adjustment easily made, and there is no possible excuse for the high current con- sumption and rapid battery deterioration met in every day practice. The usual practice of the average operator is to tighten the vibrator until the spark (observed in the open air) is at its maximum. This is commonly known as "adjusting the coil;" shortly after you hear of him thi owing out his batteries as no good. After once getting the vibrator in proper trim the ear will give much information as to the adjustment. A vibrator adjusted too lightly will cause "skipping" or mis- firing with the consequent loss of power. Never attempt to operate a coil that is damp; the coil will be ruined beyond repair. Above all, do not place the coil in a hot oven to dry, as the box is filled with wax, and if this is melted it will run out and reduce the insulation of the coil. Dry coil gradually. If the batteries are new or too strong the vibrator may be held against the core of the coil so that the vibrator will not buzz. If this is the case loosen the screw until it works at the proper speed. -If the batteries are weak, the coil may not be magnetized sufficiently to draw the vibrator and break the cir- cuit. If this is the case tighten the screw. If the vibrator refuses to work with the battery and wiring in good condition, and if you are sure that the current reaches the coil, look for dirty or pitted contacts on the vibrator. Should the contact points be dirty, clean them thoroughly by scraping with a knife or sandpaper. Water on the points will stop the vibrator, as will oil or grease. If contact points are of a uniform gray color on their con- tact surfaces, and are smooth and flat without holes, pits or GAS, OIL AND STEAM ENGINES 235 raised points, they are in good condition. If pits, discolorations or projections are noted, the contact surfaces should be brought to a square, even bearing by means of a small, fine file. Th^ point should not come into contact on an edge, but should bear on each other over their entire surface. Do not use sand paper to remove pitting, as it is almost impossible to secure an even, flat surface by this means. It is best to remove the contact screw and vibrator blade for examination and cleaning, as it is much easier to file the points square and straight when removed from the coil. Be careful not to bend the vibrator spring when cleaning, as the adjustment will be impaired. When replacing con^ct screw and vibrator blade in coil, be careful that they are in exactly the same relative position as they were before removing. Also be sure that the contacts meet and bear uniformly on their surfaces. (92) Primary Timer. The duty of the primary timer is to close the primary circuit of the spp.rk coil at, or a little before the time at which the explosive of the charge is required. The exact time at which the timer closes the circuit depends on the load, the speed, and the nature of the fuel. The lapse of time between the instant that the timer closes the circuit and the instant at which the piston reaches the end of the compression stroke is called the "advance" of the timer. When the timer closes the circuit after the piston reaches the end of the stroke, the timer is said to be "retarded." The timer is constructed so that the time of igni- tion or the advance and retard can be varied between wide limits. Advancing the spark too far will cause hammering and power loss as the piston will work against the pressure of the explosion. Retarding the spark will cause a loss of power, as the com- pression will be less when the piston starts on the outward stroke; and also for the reason that more of the heat will be given up to the cylinder walls as the combustion will be slower. The pressure in the cylinder is less with retarded ignition. Greatly retarded ignition often causes overheating of the cyl- inder walls, especially with air cooled engines, and also over- heats and destroys the seat and valve stem of the exhaust valve. Do not expect the engine to develop its rated horse-power or run efficiently with a late, or. retarded spark. When the engine is installed, and before the timer wears or 236 GAS, OIL AND STEAM ENGINES has a chance to get out of adjustment, look it over carefully and see whether the maker has left any marks relating to the timing of the spark. If there are no marks, it is well to deter- mine the relation between the position of the piston and the timer, as the efficiency of the engine depends to a great degree upon the firing point. Timers are advanced and retarded by partially rotating the housing either in one direction or the other. When the timer is mounted directly on the cam shaft with the cam shaft travel- in a direction opposite to that of the crank shaft, the timer will be retarded by moving it in the same direction as the cam shaft travels, moving it against cam shaft rotation advances the spark. Timers for two stroke cycle engines rotate at crank shaft speed, and the direction of advance and retard varies with the methods adopted for driving the timer. (93) Timer Construction. Fig. 97 shows a typical timer and circuit arranged for a four cylinder engine. The device can be arranged for any number of cylinders, however, by changing the number of sectors, the sectors being equal to the number of cylinders. There are timers on the market that differ from the one shown in the diagram but the principle of operation is the same with all. The shaft E is usually connected to the cam shaft and is electrically grounded to the engine frame at L* by means of the bearing in which the shaft rotates. The lever F mounted on the shaft E carries the pivoted arm H which is free to move on the pivot to a limited extent to allow for wear on the walls W-W-W-W. At one extremity of H is the roller I which rotates on the pin J, as the roller runs around W-W-W-W. At the other extremity of H is fastened the spring S, which forces I into contact with the walls. A-B-C-D are metallic contact sectors whose connections lead to the four spark coils. When the metal roller I comes into contact with one of the sectors as at B, the sector is grounded to the engine frame by the roller, the current traveling through the roller and its pin, through lever H and its pin, through the lever F and shaft E to ground at L, the course of the current being indicated by the arrows. As the shaft E rotates and carries wfth it roller I, the roller makes contact with the sectors in order B-C-D-A, if rotated in GAS, OIL AND STEAM ENGINES 237 the direction shown by arrow, which rotation grounds the pri- mary coils of the spark coils R 3 -R 4 -R 1 -R 2 in succession; the connection from the timer to the primary being to the primary Fig. 97. Timer Diagram. binding posts P3-P*-P1-P2. A high tension spark occurs at each contact of the roller with the sectors, as the contact allows cur- rent to flow through the primary of the coils. The high tension 238 GAS, OIL AND STEAM ENGINES binding posts S 1 -S 2 -S 3 -S 4 are connected with the spark plugs or spark gaps TJi-U'Z-lJs-U 4 by means of high tension cables. As soon as the timer grounds a coil, the coil produces a high tension spark in its corresponding spark plug. It is evident from the foregoing that the timer not only deter- mines the time at which a spark will take place, but it also determines the cylinder in which the spark will be produced, providing of course that a spark coil is provided for each cylinder. The contact sectors A-B-C-D are insulated from each other by the insulating walls W-W-W-W, the inner surface of which provides a path on which the contact roller I revolves. The contact sectors and insulating walls are encased by the protective housing Z, to which they are rigidly fastened. The housing Z can be moved back and forth on the shaft E for advance and retard, by means of the lever K. The current flows from the battery terminal V (with the roller in the position shown) through the switch M, through coil R 3 , post P 3 to sector B, from which it passes through the roller I, levers H and F to ground. From the ground on the engine frame the current flows back to its source, the battery O, thus completing the circuit. When the roller makes contact with sector C, the coil R* is energized, contact with D energizes R 1 , and so on. No two coils can be thrown on simultaneously as only one coil is grounded at a time. The high tension current flows from each coil to its plug as soon as the current passes through the primary of that coil. In some timers, the current is taken from the revolving arm through a separate connection to ground instead of grounding the shaft through the bearings. With these timers, the connec- tion is not affected by worn bearings or an oil film that tends to insulate the shaft from the bearings. (94) Operation of Timers. Timers frequently cause misfiring which is generally due to dirt or oil getting between the contacts, or to the wear of the insulating walls W-W-W-W, or to the wear of the moving parts. Dirt or gummy oil will prevent the contact coming together and completing the circuit, or will clog up the rollers or levers so that they cannot perform their functions properly. This will of course interfere with production of the spark. The contacts and 'moving parts of the timer should be kept as clean as possible, all dirt and heavy oil being removed by means GAS, OIL AND STEAM ENGINES 239 of gasoline at regular periods. Make a practice of cleaning out the timer at intervals not greater than one month; oftener if possible. Parts subject to wear, such as the roller pin J and the bear- ings should be well lubricated, none but the lightest oil being employed for this purpose. Heavy grease will gum the con- tacts and cause trouble. There should be no rough places or shoulders on the contact sectors or on the walls W-W-W-W as roughness will cause the roller to jump over the high places which in turn result in misfiring. The remedy is to machine the surfaces of the sectors and walls by grinding or turning in the lathe. Care should be taken in this operation to have the interior perfectly smooth and the sectors perfectly flush with the walls. Repair black or burnt sectors immediately by grind- ing or sand paper. Burnt spots or blackened surface on the contact sectors pre- vent good contact between roller and sector, sectors should show a bright, shining metallic surface. Sometimes the insulation warps or swells above the contacts so that the roller jumps over the contacts without touching them, or if for any reason that contact is made under these conditions, it is of a short, period and results in a poor spark. Timers often make good contact when starting, or at low speed, and misfire badly at high speed. This will be caused generally by the contact sectors or insulation projecting beyond one another, the roller has time to make good contact at low speed but jumps over the sector at high. The roller I may become rough or develop a flat stop which will cause it to jump over the contact occasionally, or it may become loose on its bearing pin J, causing intermittent misfiring. The wearing or loosening of pins J and X result in poor con- tact. Should pin J fall out of the lever H, the roller would drop out of the fork and cause serious damage. This has happened in two cases to my knowledge. Should the spring G weaken or break, contact will be made intermittently at high speed, and no contact at low. In this case it would probably be impossible to start the engine. In case the spring breaks, a rubber band may be used temporarily. Wire connections to the timer should be examined frequently as the continual back and forth movement tends to twist and loosen the wire. Use stranded or flexible wire for these con- nections, if possible. Before removing the timer mark the hub and the shaft so 240 GAS, OIL AND STEAM ENGINES that the hub can be properly replaced. If this is not done the engine will be out of time with the usual results of hammer- ing or power loss. Should the gears which drive timer shaft be removed, be sure and mark the teeth of both gears in such a manner that there will be no mistake possible in reassembling them. Mark a tooth on the small gear by scratching or with a center punch (the tooth selected should be in mesh with the large gear). Then mark the two teeth of the large gear that lay on either side of the marked tooth of the small gear. Thus it will be easy to locate the proper relative position of the two gears at any time. (95) High Tension Spark Plug. The high tension spark plug is a device that introduces the spark gap and spark into the combustion chamber, and at the same time insulates the current carrying conductor from the cylinder walls. Since the voltage of the jump spark current is very high it is evident that the insulation of the plugs must be of a very high order and that this insulation must be capable of withstanding the high temperature of the combustion cham- ber. A cross-section of a typical plug is shown by Fig. 98, to- gether with its connections and the course of the current, the latter being shown by the arrow heads. The electrode B through which the current enters the cylinder is thoroughly insulated from the walls by the porcelain rod C. The porcelain forms a gas tight joint with the threaded metal bushing F at the point P, the tension caused by the elec- trode B and the nut I holds the porcelain firmly on its seat at P. The nut is supported by the porcelain shell H which rests in the top of the metal bushing F. A washer L is inserted be- tween H and F to insure against the leakage of gas from the plug should a leak develop at P. L being a soft washer (usually asbestos) allows the porcelains C and H to expand and contract without breaking. A packing washer or gasket is also placed at the point where the electrode B passes through the porcelain H. This is the washer Q, held in position by the nut I. This washer is elastic and reduces strain on porcelain caused by the expansion. The cylinder wall G has a threaded opening R into which 'the plug is screwed, the threads of the opening corresponding with the threads on the metal sleeve E. The plug may be removed from the cylinder for examination without disturbing GAS, OIL AND STEAM ENGINES 241 the adjustment of the electrode and porcelains by unscrewing it at R. Allowing the current to jump from the electrode to the cyl- inder wall via the metal sleeve saves one wire and connection, the cylinder and the frame of the engine serving as a return path for the current. This simplifies the wiring and minimizes the danger of high tension short circuits. Fig. 98. Cross-Section of Typical Spark Plug. By unscrewing the threaded metal bushing F it is possible to examine the condition of the porcelain rod C at the point where it is exposed to the heat of the cylinder. This inspection can be made without disturbing the packed joints at L or Q. In the high tension, or jump spark system, the spark gap D-K is of fixed length, hence there are no moving parts or contacts within the cylinder to wear, to cause leakage of gas, or to cause a change in the timing. This advantage is offset 242 GAS, OIL AND STEAM ENGINES to some degree by the difficulty experienced in maintaining the insulation of the high tension current. The high tension current leaves the spark coil M at the bind- ing screw N, flows along the wire J, and enters the spark plug at the binding screw A. From the binding post the current follows the central electrode B to its terminal at D. At D a break in the circuit occurs which is called the spark gap. It is at this point that the spark occurs, the current jumping from D to point K through the air. Point K is fastened in the threaded metal sleeve E which is in turn screwed into the cyl- inder wall G or ground. From the ground the current returns to its source through binding post O to the coil. The spark therefore occurs inside of the cylinder wall and in contact with Fig. 99. Bosch Spark Plugs the combustible charge, at the point marked "spark" in the cut. If the fuel, lubricating oil, and air are not supplied in proper proportions, soot will be deposited on the lower surface of the porcelain, and as soot is an excellent conductor of high tension current, the current will follow the soot rather than the high resistance of the spark gap, a condition that will result in mis- firing or a complete stoppage of the motor. Carbonized lubri- cating oil or moisture have the same effect. Preventing the deposits of soot, moisture and carbonized oil is the chief object of plug manufacturers, many of whom have brought out designs of merit. In fact the problem of elimina- tion of soot is the principal cause of the many types of plugs now on the market. While many plugs differ in minor refinement of detail from the typical plug shown, the connections and general construe- GAS, OIL AND STEAM ENGINES 243 tion are the same in all types, the spark being produced in a gap of fixed length which is insulated from the cylinder. A well known form of plug, the Bosch, is shown by Fig. 99 a-b. In this plug a special material known as Steatite is used instead of the usual porcelain. The three external electrodes surrounding the center electrode is a particularly efficient ar- rangement, especially for magnetos. A peculiar form of pocket minimizes the soot problem. As porcelain is brittle and is easily broken by the effects of heat or blows, mica insulation is often used in place of the porcelain. The central core of a mica plug is formed by a stack of mica washers, which are held in place by the central electrode and the upper lock nuts. A poorly constructed mica plug is easily destroyed by a weak, stretching, electrode, or by an overheated cylinder. The latter causing the washers to shrink and admit oil between the layers of mica washers causes a short circuit. As soon as the mica washers loosen and separate, they should be forced to- gether by means of the mica lock nuts on the top of the plug. If by any reason the mica core becomes saturated with oil, it is best to obtain a new one, as it is almost impossible to remove the oil by simple means open to the average operator. The chief value of a mica plug lies in its toughness and me- chanical strength, a good mica plug being practically indestruct- ible. When heated, porcelain does not expand at the same rate as the metal sleeves, hence in poorly designed or imperfect plugs, heavy strains are thrown on the delicate porcelains which causes them to crack. When a crack develops it provides a lodging place for soot and carbon which of course causes a short circuit. Should a compression leak occur through faulty packing be- tween the porcelain and sleeve, it should be immediately tight- ened up for eventually it will leak enough to destroy the plug or reduce the output of the engine. When ordering a plug be sure that you know the size and type required by your engine. Some engines require a longer plug to reach the combustion chamber than others. Never in- stall a shorter plug than that originally furnished with the en- gine. Be sure that the plug is not too long as it may interfere with the action of the valves or may be damaged by them. Plugs are furnished with several threads and taps, i. e. : 5^ inch pipe thread (Generally used on stationary engines). Metric Thread (Generally used on imported autos). 244 GAS, OIL AND STEAM ENGINES % inch A. L. A. M. Standard (Used on Domestic automobiles). Using a plug in a hole tapped with the wrong thread will destroy the thread in the cylinder casting and cause compression leaks. (96) Care of Spark Plug. Porcelains are often broken by screwing the plug too tightly in a cold cylinder, as the cylinder expands when heated and crushes the frail plug. A plug installed in this manner is dim- cult to remove as the expanded walls grip the thread. The plug should be screwed in just enough to prevent the leakage of gas. A short thin wrench should "be used in screwing the plug home such as a bicycle wrench. A wrench of this type is so short that it will be almost impossible to exert too much force, and will be thin enough to avoid any possible injury to the packing nut. Bad leaks may be detected by a hissing sound that is in step with the speed of the engine, small leaks may be detected by pouring a few drops of water around the joint. If a leak exists bubbles will pass up through the water and show its location. Plugs are more easily removed from a cold cylinder than a hot. If the plug sticks when the engine is cold and is impossi- ble to remove with a moderate pressure on the wrench squirt a few drops of kerosene around the threads. Never exert any force on the porcelain or insulation. The high tension cables should be connected to the plugs by means of some type of "Snap Terminal," such terminals may be had from automobile dealers. These terminals make a firm contact with the plug and do not jar loose from the plug by the vibration of the engine. They are easily disconnected when the inspection of the plug becomes necessary, and are generally a most desirable attachment. The high tension cable should be firmly connected to the plug terminal under all circumstances. A loose connection will cause misfiring or will bring the engine to an abrupt halt. If snap terminals are not used the plug binding screw should be screwed down tightly on the wire. When making connections see that the wire is bright and clean, and that frayed ends of the wire do not project beyond the plug and make contact with other parts of the engine. A large percentage of high tension ignition troubles are due to short circuits in the spark plug which are generally caused by deposits on the surface of the plug insulation. Soot or oil GAS, OIL AND STEAM ENGINES 245 may be removed from the plug by scrubbing the porcelain and the interior of the chamber with gasoline applied by a tooth brush. Examine the plug for cracks, and if any are found, re- place the porcelain or throw the plug away. A cracked por- celain is always a cause of trouble. To test a plug for short circuits, remove it from the cylinder, reconnect the wire, and lay the sleeve of the plug on some bright metal part of the engine in such a way that only the threaded portion is in contact with the metal of the engine. Close the switch and see if sparks pass through the gap. If no sparks appear, and if the coil is operating prop- erly, clean the plug. As an additional test for the condition of the coil, hold the end of the high tension cable about J4 mcn from the metal of the engine while the coil is operating. If a heavy discharge of sparks takes place between the end of the cable and the metal of the engine, the coil is in good condition. If a partial short circuit exists, the spark at the gap will be weak and without heat; the result will be intermittent, or mistfir- ing with a loss of power. Moisture in the cylinder is a common cause of plug short circuits, the moisture coming from leaks in the water jacket or from the condensation of gases in a cold cylinder. A drop of water may bridge the spark gap, allowing the current to flow from one electrode to the other without causing a spark. If a cloud of bluish white smoke has been issuing from the exhaust pipe before the misfiring started, you will probably find that the trouble is due to sooted or short circuited plug. The remedy is to decrease the amount of lubricating oil fed to the cylinder. When a magneto is used the intense heat of the spark causes minute particles of metal to be torn from the electrodes and deposited on the insulation as a fine metallic dust. This will of course cause a short circuit and must be removed. Short circuits are sometimes caused by the magneto current melting the electrodes and dropping small beads of the metal between the conductors. All metallic particles should be removed from the plug. While a spark plug may show a fair spark in the open air test, it will not always produce a satisfactory spark in the cyl- inder on account of the increased resistance of the spark gap due to compression. Compression increases the resistance of the spark gap enor- mously and thin, highly resisting carbon films that would cause 246 GAS, OIL AND STEAM ENGINES very little leakage in the open air will entirely short circuit the gap under high pressure, the current taking the easiest path which in the latter case is the carbon deposit. In order to produce conditions in the open air test similar to those in the cylinder we must devise some method of in- creasing the resistance of the spark gap in the open air above any possible resistance that could be offered by the carbon film. Placing a sheet of mica or hard rubber between the electrodes, or in the spark gap, will increase the resistance to the required degree. If the spark plug is in good condition the spark will jump from the insulated terminal to the shell when the mica is in the spark gap, but if a short circuit exists the current will go through it without causing a spark. It is assumed that the battery and coil are in good condition when making the above test. If the electrodes or spark points are dirty they should be cleaned with fine sand paper, special att-ention being paid to the surfaces from which the spark issues. When reassembling the plug, see that all of the washers and gaskets are replaced and that the length of the spark gap is unchanged. A little change in the spark gap may make a great change in the spark. A good spark is blue white with a faint reddish flame sur- rounding it. When the discharge is intermittent or sputters in all directions, either the coil or the plug are partially short cir- cuited. Always have a spare plug on hand. Ordinarily the length of the gap or the distance between the electrodes should be about 3*2 inch for batteries, and a trifle less for magnetos. A silver dime is a good gauge for the gap. If the engine misfires with the coil and batteries in good condi- tion, try the effects of shortening the gap a trifle, usually this will remedy the difficulty. Exhausted batteries may be made operative temporarily by closing up the plug gap to 1/64 inch or even less. Shortening the gap increases the heat of the spark and nothing is gained by having it over ^2 inch. Almost all high tension magnetos have visible safety spark gaps that show instantly the presence of an open circuit in the secondary or high tension circuit. If an open circuit exists, a stream of sparks will flow across the safety spark gap at low speed. To determine the cylinder that is misfiring in a four cylinder engine proceed as follows: Remove cover on spark coil, and hold down one vibrator spring firmly against the core while the engine is running. GAS, OIL AND STEAM ENGINES 247 If the engine speed is not decreased by cutting this coil out of action, it is probable that this is the coil connected to the misfiring cylinder. Now release this vibrator and proceed to the next coil, and hold its vibrator down. If this decreases the speed of the engine you may be sure that the first coil is in the defective circuit. If the vibrator buzzes on the coil under in- spection the trouble will be found in the plug. Cutting out a coil connected to an active cylinder decreases the speed of the engine. Cutting out the coil connected with a dead cylinder makes no difference. (97) Magnetos. A magneto is a device that converts the mechanical energy received from the engine into electrical energy, the electricity thus produced being used to ignite the charge in the engine. This appliance does away with all of the troubles incident to a rapidly deteriorating chemical battery and produces a much hotter and uniform spark. A magneto is especially desirable with multiple cylinder engines where the demand for current is almost continuous, as the amount of current delivered by the magneto has no effect on its life or upon the quality of the spark. The principal parts of the generating system of the magneto are the magnets, the armature, the armature winding, and the current collecting device, of which the armature and its wind- ings are the rotating parts. The production of current in the magneto is the result of moving or rotating the armature coil in the magnetic field of force of the magnets. When any conductor is moved in a space that is under the influence of a magnet a current is generated in the conductor which flows in a direction perpendicular to the direction of motion. The value of the current thus generated depends on the strength of the magnetic field, the speed with which it is cut, and the number of conductors cutting it that are connected in series. Roughly, the voltage is doubled, with an increase of twice the former speed, and with all other things equal, the voltage is doubled by doubling the number of conductors connected in series. By employing powerful magnets, and a large number of con- ductors (turns of wire) on the armature it is possible to ob- tain sufficient voltage for the ignition system at a compara- tively low speed. The number of amperes delivered depends principally upon the internal resistance of the armature and the external circuit, and not on the number of conductors, nor 248 GAS, OIL AND STEAM ENGINES directly upon the strength of the field. For this reason, low voltage machines f'Jiat are intended to deliver a great amperage have only a few conductors of large cross section, while high tension machines have a great number of conductors of small size. In all cases the magneto, or ignition dynamo must be considered simply as a generator of current in the same way that a battery is a source of current since the current generated by them is utilized in precisely the same way. The class of ignition system on which the magneto is used determines the class of the magneto. The low tension mag- neto is used principally for the make and break system, although it is sometimes used in connection with a high ten- sion spark coil or transformed in the same way that a bat- tery is used with a vibrator coil. The high tension magneto is used exclusively with the jump spark system and high tension spark plug. These classes are again subdivided into the direct and alter- nating current divisions, depending on the character of the cur- rent furnished by the magneto. Briefly a continuous current is one that flows continually in one direction while an alternating current periodically reverses its direction of flow. As the alter- nating current magneto is the most commonly used type, we will confine our description to this class of magneto. The alternating current magneto is much the simplest form of ma- chine as it has no commutator, complicated armature winding, nor field magnet coils, and in some types the brushes and revolving wire are eliminated. As the magnetic flux of an alternating magneto is changed in value, that is increased and decreased, twice per revolution, it follows that the current changes its direction twice for every revolution of the armature. Each change in the direction of current flow is called an alternation. The voltage developed in each alternation or period of flow is not uniform, the voltage being low at the start of the alter- nation, rapidly increasing in voltage until it is a maximum at the middle, and then rapidly decreasing to zero, from which point the current reverses in direction. As we have two such alternations, in a shuttle type magneto, per revolution we have two points at which the maximum voltage occurs; that is in the center of each alternation. These high voltage points are called the peak of the wave and consequently the sparking devices should operate at the peak of the wave or at the point of high- est voltage. The spark therefore should occur when the shuttle GAS, OIL AND STEAM ENGINES 249 or inductors are at a oertain fixed point in the revolution at which point the peak of the wave occurs. The peak of the wave occurs when the shuttle is being pulled or turned away from the magnets. In what is known as the "shuttle type" alternating current magneto, the generating coil is wound in the opening of an "H" type armature. This iron armature 'core is fastened rigidly to the driving shaft and revolves with it. As the armature revolves, it is necessary to collect the current that is generated by means of a brush that slides on a contact button B f the button being connected to one end of the winding. (98) Low Tension Magneto. The winding of the low tension magneto consists of a few turns of very heavy wire or copper strip, one end of which is grounded to the armature shaft and the other passing through the hollow shaft from which it is insulated. The end of the insulated wire is connected to the contact button (B) on which the current collecting brush presses. As one end of the winding is grounded, one brush, and one connecting wire is saved as the current returns to the magneto through the frame of the magneto. As the shuttle revolves between the magnet poles the magnetism is caused to alternate through the iron of the armature, thus causing the current to alternate in direction and fluctuate in value. Since there are only two points at which the maximum cur- rent can be collected during a revolution with the alternating current magneto, it is necessary to drive it positively through gears, or a direct connection to the shaft so that this maximum point of voltage will always occur at the same point in regard to the piston position. If it is driven by belt without regard to the position of the piston, it is likely that there will be many times that the voltage is zero or too low in value when the spark is required in the cylinder. Alternating current magnetos must be positively driven, and the armature must be connected to the engine so that the peak of the wave occurs at, or a little before the end of the compression stroke. With this type of magneto the only point .that is likely to give trouble is the point at which the brush makes contact with the contact button. If the brush should stick or not make con- tact, or if the button is dirty or rusty, the current will not flow; this point should always be given attention. Outside 250 GAS, OIL AND STEAM ENGINES of this the only attention necessary is to keep the bearings oiled Fig. 101 and Fig. 102 show the Sumter low tension magneto as arranged for make and break ignition. The armature and its connections are of exactly the same type as that shown in the previous diagram. The magnets and frame are arranged to tilt back and forth so that the peak of the wave will occur at the advanced and retarded positions of the igniter. This ar- Fig. 101. Sumter Magneto Advanced. Fig. 102. Sumter Magneto Retarded. rangement allows the full voltage of the magneto to be obtained at any point within the range of the ignitor, an important item when starting the engine or running at low speed. When mounted on the engine, as shown by Fig. 103, the magnets are provided with an operating rod that is marked "start" and "run." When the pin on the engine bed is engaged under "start," the magneto is retarded, when the pin is under "run" it is advanced. A number of intermediate points are provided at which the operating arm is held fast by tooth engagements as shown in the slotted handle. As shown in the illustration the magneto is fully advanced. The gears by which the mag- GAS, OIL AND STEAM ENGINES 251 neto is driven are clearly shown in the cut, the ratio between the gear on the crank shaft and that on the magneto shaft be- ing exactly 2 to 1. One lead is carried to the make and break igniter in the cylinder head, the current being returned through the bed of the engine. The same make of magneto is shown mounted on a vertical engine in Fig. 104. In this case the magneto is positively driven from the crank shaft of the engine by a chain. The single conductor running from the magneto to the cylinder heads is clearly shown. To start the engine, the igniter is set in the usual manner and the magneto tilted to starting position, as shown in the illustration. The engine is then started in the usual manner and, when running, the igniter is changed to running position, and the magneto is tilted out- 252 GAS, OIL AND STEAM ENGINES wardly. It is not important which is changed first, the magneto or the igniter. It is easy to remember the "starting" and run- ning "position" of the magneto, the running position always be- ing that in which the magnetos are tilted in the direction opposite to that in which the engine runs. (99) Care of Low Tension Magnetos. (1) Avoid setting a magneto on an iron or steel plate, unless stated otherwise in the manufacturer's directions, as in some makes the magnetism will be short circuit by iron or steel and will reduce the output. (2) Do not jar magnets or magneto unnecessarily, for this tends to weaken the magnets. (3) Never remove the magnets if it can possibly be avoided. If this must be done, mark the magnets and gears so that they may be replaced in exactly the same position. If your mag- neto refuses to generate after reassembling it is probable that they are reversed in position or that the magnetism has been knocked out of them while off of the magneto. (4) As soon as the magnets are removed, or better before, place a plate of iron or steel across both ends of the magnet. Don't leave the magnets without this keeper for any length of time or they will lose their magnetism. The best plan is to leave the magnets alone. (5) Remember that the running clearance between the mag- nets and armature is very small, only a few thousandths of an inch, and that any error in replacing the bearings in their proper position will cause the armature to bind in the tunnel. Handle armature carefully and do not lay it in a dirty place as a bent shaft or grit in the armature tunnel will fix it permanently. (6) Most all magnetos are practically water proof, but don't experiment with the hose. (7) Make all connections firmly and have the wire clean under the binding posts. (8) Only a few drops of oil are needed at long intervals, don't neglect to oil them, but above all do not drown them with oil. (9) Examine the brush occasionally and clean off all oil and dirt. (10) When replacing the magneto on the engine after its removal see that the gears are meshed in the former position. Best to mark the teeth before removal. GAS, OIL AND STEAM ENGINES 253 (100) High Tension Magnetos. The "true" high tension type magneto is complete in itself, requiring no jump spark coil nor timer, the high tension cur- rent being generated directly in the coils carried by the arma- ture. This arrangement reduces the wiring problem to a mini- mum, as the only wires required are those leading directly to the spark plugs, and one low tension wire connecting the cut- out switch used for stopping the engine. The armature of this type of magneto carries two independ- ent windings, one of a few turns of coarse wire called the pri- mary coil, and the other consisting of thousands of turns of extremely fine wire called the secondary coil. It is in the latter Fig. 105. Single Cylinder High Tension Bosch Magneto. coil that the high tension current is generated. The tinier is connected directly to the armature shaft, and is an integral part of the magneto. All primary connections are therefore made within the magneto. Belts or friction drives cannot be used with this type of magneto. As there are no vibrators or independent coils used, the spark occurs exactly at the instant that the timer operates or breaks the primary circuit. It will be noted that the spark is produced with this magneto when the primary circuit is broken by the timer, instead of made as is the case with battery coils, or coils used with low tension magnetos. There is no lag and conse- quently the time of ignition is not affected by variations in the engine speed, which requires an advance and retard of the spark with batteries and vibrator coils. 254 GAS, OIL AND STEAM ENGINES When used with multiple cylinder engines the high tension magneto is provided with a distributor, which connects the high tension current with the different cylinders in their proper firing order. The timer determines the time at which the spark is to occur and the distributor determines the cylinder in which the spark is to take place. The sparks delivered by the high tension magneto are true flames or arcs of intense heat, and exist in the spark gap for an appreciable length of time. It is evident that such flames pos- sess a much greater igniting value than instantaneous static spark delivered by the high tension spark coil used with the bat- Fig. 106. Connecticut High Tension Magneto. tery or operated by the low tension magneto, and are capable of firing much weaker mixtures. Like low tension magnetos, the true high tension type may be of either the inductor or shuttle wound class. All high tension magnetos are positively connected or geared to the engine in such a manner that there is a fixed relation between time of the current impulse produced by the magneto and the firing posi- tion of the engine piston. The current is generated on the same principle as in the low tension shuttle type; that is, by a coil of wire revolving in the magnetic field established by permanent magnets. GAS, OIL AND STEAM ENGINES 255 During each revolution of the armature, two sparks are pro- duced at an angle of 180 from each other. The advance and retard of the spark is obtained by means of the timing lever which shifts the timer housing back and forth which results in the primary current being interrupted earlier or later in the revolution of the armature. The timing lever can turn through an angle of 40 measured Fig. 107. Longitudinal Section Through Bosch High Tension Magneto. on the armature spindle, and the angle of advance for multiple engines is as follows: Advance for 1 cylinder 40 Advance for 2 cylinders 40 Advance for 3 cylinders 50 Advance for 4 cylinders 40 Advance for 6 cylinders 27 A timer is used with the magneto on a "jump spark" system in the same way as with a battery, providing a vibrating coil is used. In one type of magneto the Connecticut, the coil is part -of the magneto, and is fastened to the magneto frame. This type of magneto uses a non-vibrating coil, and produces but a single spark each time the primary circuit is broken by the magneto timer. As the timer on this type is driven by the 256 GAS, OIL AND STEAM ENGINES magneto shaft, it is evident that the magneto must be "timed" with the engine, or must have its armature shaft connected to the shaft of the engine in such a manner that the timer con- tact is broken, and the single spark produced at the instant that ignition is required in the cylinder. Unlike the dynamo, the alternating current magneto can- not be used with a storage battery, the alternating current pro- ducing no chemical change in the electrodes of the battery. The Bosch high tension magneto is a typical high tension magneto having the primary and secondary windings wound directly on the armature shaft, there being no external sec- ondary coil. The end of the primary winding is connected to the plate (1) Fig. 107, which conducts the current to the Four Cylinder "D4" High Tension Bosch Magneto Showing Distributor. platinum screw of the circuit breaker (3). Parts (2) and (3) are insulated from the breaker disc (4), which is in electrical contact with the armature core and frame. When the circuit breaker contacts are together the primary winding is short circuited, and when they are separated the current is broken and the spark oecurs. The breaker contacts are simply two platinum pointed levers that are separated and brought to- gether by the action of a cam as they revolve. A condenser (8) is provided for the circuit breaker to suppress the spark and to increase the rapidity of the "break." The secondary winding of fine wire is. a continuation of the primary winding, and the secondary is wound directly over the primary. The outer end of the secondary connects with the GAS, OIL AND STEAM ENGINES 257 slip ring (9) on which slides the carbon brush (10), which con- ducts the high tension current from the armature. This brush is insulated from the frame by the insulation (11). From (10) the current is led through the bridge (12) through the carbon brush (13) to the distributer brush (15). Metal segments are imbedded in the distributor (16), the number of which corre- sponds to the number of cylinders. As the brush rotates, it makes consecutive contact with each of the segments in turn and therefore leads the current to the cylinders in their firing order. Wires from the cylinders are connected to sockets that in turn connect with the segments. The disc driving the dis- r _ Primary winding Secondary winding - Frame breaker di Fig. 108. Bosch High Tension Circuit. tributor brush (15) is geared from the armature shaft in such a way that the armature turns twice for every revolution of the distributor, when four cylinders are fired, and three times -for the distributors once when six cylinders are fired. The voltage of the current generated in the secondary coil by the rotation of the armature is increased by the interrup- tion of the primary circuit caused by the opening of the contact breaker. At the instant of interruption of the primary circuit the high tension spark is produced at the spark plug. As the spark must occur in the cylinder of the engine at a certain position of the piston, it is necessary that the interrupter act at a point corresponding to a definite position of the piston, consequently this type of magneto must be driven positively 258 GAS, OIL AND STEAM ENGINES from the motor by means of gears, or directly from the shaft. These magnetos run in only one direction. This running direction should be given when magneto is ordered, as being "clockwise" or "counter-clockwise" when looking at the driving end of the magneto. The magneto for the single and double cylinder engines has no distributor, the high tension current being led directly from the armature. The circuit diagram of the Bosch four cylinder magneto is shown by Fig. 108, the winding and plug connections being clearly shown. When connecting the magneto care should be taken to have the distributor and plug connections arranged so that the cylinders will fire in the proper order. (101) Bosch Oscillating High Tension Magneto. The oscillating type of magneto is used on slow speed heavy duty engines that move too slowly for the ordinary type of magneto. In the oscillating type the armature is given a short angular swing by the action of a tripping device operated by the engine which results in an intense spark at the lowest speeds. Magneto type "29" is constructed with two powerful steel magnets, while magneto type "30" is provided with three; an armature of the shuttle type is arranged to oscillate between their poleshoes. The magneto is actuated by a rotating cam or other suitable device, which moves the armature 30 from its normal position whenever ignition is required. To permit this movement, a trip lever is mounted upon the tapered end of the armature shaft, this trip lever being held in a definite position by the tension of the spring or springs 1. The trip lever is only sup- plied when specially ordered, but each magneto is provided with the necessary springs and spring bolts. When the trip lever is moved from its normal position by the operating mechanism, the springs are extended, and when the operating mechanism releases the trip lever, the later re- turns the trip lever and armature to their normal position, this movement resulting in the production of a sparking current in the armature winding. The winding of the armature is composed of two parts, one being the primary winding, which consists of a few turns of heavy wire, and the other the secondary winding, which con- sists of many turns of fine wire. GAS, OIL AND STEAM ENGINES 259 The tension of the current produced by the oscillation of the armature is increased by closing the primary circuit at a certain position in its movement, and then interrupting it by means of the breaker. At the moment of the interruption, an arc-like spark is formed at the spark plug and ignition occurs. On cam shaft (c) two cams are mounted side by side. One of these cams (a) is to be used for starting the motor, or for the retarded spark position, while the second (b) is to be used for operation, or for the full advance position. These cams are mounted on a sleeve, which may be moved longitudinally on the shaft, so that the trip lever may be operated by cam (a) or cam (b) as desired. The sleeve is caused to rotate with the shaft by a key. Between the cam (b) and a fixed collar (f) a spiral spring is arranged, which tends to maintain the sleeves Fig. 109. Elevation of Bosch Oscillating Magneto for Slow Speed - Engines. High Tension Type. in the position when the cam (b) is in operation. A stop collar is also provided to limit the movement of the sleeve beyond this full advance position. Over this collar is fitted a hand wheel, which, in the position illustrated in the diagram, acts together with the collar as a stop. Around the collar is a circular key- way, and a brass bolt is located in the hand wheel to lock into this keyway when the hand wheel is pushed into the position indicated by the dotted lines. This movement of the wheel forces the cam sleeve forward, and brings the retarded cam (a) into the operating position to permit the engine to be started. (102) The Mea High Tension Magneto. The low tension winding of the ordinary type of magneto is short-circuited by a breaker which opens at certain points of 260 GAS, OIL AND STEAM ENGINES each revolution with the result that a high voltage is generated across the high tension winding at the moment of the break, and a spark produced across the spark gap in the cylinder to which it is connected. The quality of this spark, or in other words the heat value, depends among other factors upon the particular position of the armature in relation to the magnetic field at the moment the spark is produced. As the armature in this type of magneto is in a favorable position for obtaining a Fig. 110. Diagram of Oscillating Magneto, Showing Cam and Trigger Arrangement. spark twice every revolution, two sparks can be obtained per revolution. The timing of the spark is accomplished by open- ing the breaker earlier or later, by shifting the breaker housing naturally with the unavoidable result that if the position of the magnetic field remains stationary, the relative position between armature and field at the moment of the break must vary. Since, however, as explained above, the quality of the spark depends upon this relative position, it is apparent that a good spark, GAS, OIL AND STEAM ENGINES 261 can, with a stationary magnetic field, be produced only at one particular timing. The result of these conditions are known to everybody Fig. 111. Side Elevation of "Mea" Magneto, Showing the Magnets, and Cradle in Which the Magneto Swings When Advanced and Retarded. familiar with automobiles. They are the difficulty of cranking a motor on one of the average high tension magnetos, if the spark is fully retarded, and of operating the motor on the mag- 1 7f 1 12 , 4: 18 100 Fig. 112. Longitudinal Section of "Mea" High Tension Magneto. neto at very low speed, particularly when it is overloaded, as for example, in hill climbing. Attempts have therefore been made to obtain the spark, independent of the timing, always at the same favorable position of the armature. 262 GAS, OIL AND STEAM ENGINES The distinct innovation and improvement incorporated in the Mea magneto consists in bell shaped magnets (Fig. Ill) placed horizontally and in the same axis with the armature, instead of the customary horse-shoe magnets placed at right angle to the armature. This at once makes possible and practicable the simultaneous advance and retard of magnets and breaker instead of the ad- vance and retard of the breaker alone as the magnets may be moved to and fro with the breaker housing. It will be seen that as a result of this new departure the relative position of arma- ture and field at the moment of sparking is absolutely main- tained, and the same quality of spark is therefore produced, no matter what the timing may be. Furthermore, the range of timing, which with the horse-shoe type of magneto is limited to 10 or 15 at low speeds (i. e. at speeds at which a retarded spark is of value) becomes limited only by the necessity of supplying a suitable support for the magnets. With the stand- ard types of Mea magnetos described in the following, this range varies from about 45 to 70, but if necessary this range can be increased to any amount desired. The bell-shaped magnets are fixed to the casing which is mounted on a base supplied with the magneto. The timing is altered by turning the casing and magnets together on the base. Fig. 112 shows a longitudinal section of a four cylinder Mea magneto. The armature F with the ball bearings 17-18 rotates in the bell-shaped magnets 100, the poles of the magnets being on a horizontal line opposite the armature 1. The armature is of the ordinary H type iron core wound with a double winding of heavy primary and fine secondary wire. On the armature are mounted the condenser 12, the high tension collector ring 4, and the low tension circuit breaker 26-39. The circuit breaker consists of a disc 27 on which are mounted the short platinum 33, the other contact point 34 is movable and is supported by a spring 30 which is fastened to the in- sulated plate 28 mounted on disc 27. Fiber roller 31 in con- nection with cam disc 40 which is provided with two cams is located inside the breaker. Revolving with the armature the roller. presses against the spring supported part of the breaker whenever it rolls over the two cams which of course is twice per revolution. Inspection of the breaker points is made easy by an opening in the side of the breaker box. The box is closed by a cover 74 supporting at its centre the carbon holder 47 by means of GAS, OIL AND STEAM ENGINES 263 which the carbon 46 is pressed against screw 24. This latter screw connects with one end of the low tension winding while the other end is connected to the core of the armature. It Magneto of Roberts Motor in Advanced Position. will, therefore, be seen that the breaker ordinarily short-circuits the low tension winding and that this short-circuit is bioken only when the breaker opens; it will also be apparent that when 112-a. Advance and Retard Mechanism Used in the Roberts Motors. The Magneto is Driven by a Helical Gear from the Small Pinion. By Shifting the Gfcar Back and Forth on the Pinion, the Armature of the Magneto is Advanced or Retarded in Regard to the Piston Position. The Reason for this Change Will be Seen from the Cuts by Noting the Position of the Lower Helix. the screw 24 is grounded through terminal 50 and the low-ten- sion switch to which it is connected, the low-tension winding 264 GAS, OIL AND STEAM ENGINES remains permanently short-circuited, so that the magneto will not spark. The entire breaker can be removed by loosening screw 24. The high tension current is collected from collector ring 4 by means of brush 77 and brush holder 76, which are supported by a removable cover 91 which also supports the low tension grounding brush 78 provided to relieve the ball bearings of all current which might be injurious. Cover 91 also carries the safety gap 89 which protects the armature from excessive volt- ages in case the magneto becomes disconnected from the spark plugs. The distributor consists of the stationary part 70 and the rotating part 60 which is driven from the armature shaft through steel and bronze gears 7 and 72. The current reaches this dis- tributor from carbon 77 through bridge 84 and carbon 69. It is conducted to brushes 68 placed at right angles to each other and making contact alternately with four contact plates em- bedded in part 70. These plates are connected to contact holes in the top of the distributor, into which the terminals of cables leading to the different cylinders are placed. In the front plate of the magneto is provided a small window, behind which appear numbers engraved on the distributor gear which correspond to the number of the cylinder the magneto is firing. This indicator is of great value as it allows a setting or resetting after taking out, without the necessity of opening up the magneto to find out where the distributor makes contact. The magneto proper is mounted in the base 53 which is bolted to the motor frame and the arrangement is such that the magneto can be removed from its base by removing the top parts 60a and 60b of the two bearings. The variation in timing is affected by turning the magneto proper in the stationary base which is accomplished by the spark lever connections attached to one of the side lugs 88. The spark is advanced by turning the magneto opposite to rotation and is retarded by turning it with rotation. One cylinder magnetos are similar to the four cylinder except that the distributor and gears are omitted. (103) The Wico High Tension Igniter. The Wico igniter produces a spark similar tc that of the conventional high tension magneto exce.pt that the heat of the spark is independent of the engine speed. In other respects it is very different from the types described in the preceding pages for its motion is reciprocating instead of being rotary, and GAS, OIL AND STEAM ENGINES 265 because all of the wire is stationary, the only movement being that of the iron core that passes through the center of the fields. The fact that the spark is of the same intensity at all speeds makes this device particularly desirable in starting the engine at which time the mixture is always of the poorest quality. It is very simple, and is without condensers, contact points Fig. 113. Wico Igniter. High Tension Reciprocating Type. or primary windings, and has no parts that require adjustment. The current is generated by the reciprocating movement of two soft iron armatures shown as a bar across the bottom of the two coils, which move alternately into and out of contact with the ends of the soft iron cores. The movement of these armatures in the upward direction is produced by the motion of the engine and the speed of this movement is, of course, pro- 266 GAS, OIL AND STEAM ENGINES portional to the speed of the engine. The downward move- ment, which produces the spark, is caused by the action of a spring, is much more rapid than the upward movement and entirely independent of the speed of the engine. The magnets are made of tungsten steel, shown as two bars across the top of the coils, hardened and magnetized and are fastened by machine screws to the cast iron pole pieces, which serve to carry the magnetic lines of force from the poles of the magnets to the soft iron cores. The cores, which fit into slots milled in the pole pieces, are laminated or built up of thin sheets of soft iron, each sheet being a continuous piece, the full length of the core. Each core, extends from just below the top armature, down through the pole piece, and coil to just above the bottom armature. Each armature consists of a number of laminations or sheets of soft iron mounted on a spool shaped bushing, which, in turn, is loosely fitted onto the squared end of the armature bar. The armature bar is supported with a sliding fit in a box shaped guide which is fastened in the case. On the outer ends of the armature bar are spiral springs held in place by cup shaped washers and retaining pins, the combina- tion making a self-locking fastening similar to the familiar valve spring fastening used almost universally on gas engines. These springs bear against the armatures and tend to force them against the shoulders of the armature bar. The coils each have a simple high tension winding of many turns, thoroughly insulated and protected against mechanical injury. They are connected together in series by means of a metal strip, thus making one continuous winding. In the single cylinder igniter, one end of the winding is grounded to the case of the igniter, while the other end is connected to the heavily insulated lead wire. This lead wire passes out through a stuf- fing box, packed with wicking and thoroughly water tight, direct to the spark plug in the cylinder. In the two cylinder machine no ground connection is used, but both ends of the winding are connected to lead wires pass- ing out of the case to the spark plugs. The action of the igniter is as follows: As the driving bar, through its connection with the engine, is moved downward to its limit of travel, carrying the latch with it, the shoulder on the side of the latch snaps under the head of the latch block. As the motion reverses the latch carries the latch block and ar- mature bar upward. The lower armature, being in contact with GAS, OIL AND STEAM ENGINES 267 the stationary cores, cannot rise with the armature bar, but the lower armature spring is compressed between its retaining washer and the armature, while the bar rises and carries with it the upper armature, which bears against the upper shoulders on the bar. As the driving bar continues its upward motion the upper end of the latch meets the lower end of the timing wedge and, as the wedge is held stationary by the timing quadrant, a further movement of the latch causes it to be pushed aside until the shoulder on the latch clears the latch block and releases it. As the lower armature spring is at this time exerting a pres- sure between the armature bar and cores through the medium of the lower armature, the instant the latch block is released, the armature bar is quickly pulled downward, carrying the upper armature with it. Just before the motion of the upper armature is stopped by its coming in contact with the cores, the lower shoulders on the armature bar come in contact with the lower armature, and, as the bar has acquired considerable velocity, its momentum carries the lower armature away from the cores against the pressure of the upper armature spring, which thus acts as a buffer to gradually stop the movement of the armature bar. The armature bar finally settles in a central position. The timing of the spark is accomplished by releasing the ar- mature bar earlier or later in the stroke. This is done by shift- ing the position of the eccentric timing quadrant, which in turn varies the position of the wedge so that the latch strikes it earlier or later in the stroke. The timing quadrant is furnished with several notches into one of which the top of the wedge rests, thus holding the quadrant in the desired position. The motion should preferably be taken from an eccentric on the cam shaft of a single cylinder four cycle engine, or the crank shaft of a single cylinder two cycle or a two cylinder four cycle engine. On a two cylinder four cycle engine, it is sometimes more convenient to drive the igniter from the cam shaft, using a two throw cam to produce the required number of sparks. In this case the shape of the cam should be such as to duplicate the motion of the eccentric. That is, it should start the driving bar slowly from its lower position, move it most rapidly at mid stroke and bring it to rest gradually at the upper end of the stroke, exactly as is done by the eccentric motion. When an eccentric is already on the engine the motion may be taken from it to an igniter with a driving bar through a 268 GAS, OIL AND STEAM ENGINES properly proportioned lever that will give the required length of stroke. Where a plunger pump is used on the engine the motion can usually be taken from the pump rod. Where" an eccentric has to be provided especially for the igniter, the driv- ing bar is generally used with its roller running on the eccentric. (104) Starting On Magneto Spark. A four-cylinder engine in good condition will come to rest with the pistons approximately midway on the stroke and bal- anced between the compression of the compressing cylinder and of the power cylinder. When the cylinders of such an engine are charged with a proper mixture, the engine will start by the igni- PLATINUM SCREW NTERRl/PTER SPR!MG PLATINUM SCREW INTERRUPTER LEVER TIMING CONTROL ARM STEEL SEGMENT Fig. 114. Bosch Dual System. tion of the mixture contained in the compressing cylinder, for the pressure produced by the ignited gas will be sufficient to rotate the crankshaft. It is essential, for the ignition system to be so arranged that a spark can be produced at any point in the piston travel, and in this the Bosch dual, duplex and two independent systems are successful. The Bosch dual system, Fig. 114, is part of the equipment of many of the cars and engines marketed, and is composed of two separate and distinct ignition systems, one supplying igni- tion by direct high-tension magneto, and the other by a battery and high-tension coil. These two systems consist in reality of but two main parts; the dual magneto, incorporating a separate battery timer, and the single unit dual coil with its battery. The sparking current from either battery or magneto is brought GAS, OIL AND STEAM ENGINES 269 to the magneto distributor, so that the only parts used in com- mon are the distributor and the spark plugs; the common use of the latter for both magneto and battery systems is cause for the popularity of the dual system for motors having provision for only one set of plugs. In both the magneto and the battery sides the spark is pro- duced on the breaking of the circuit, and the coil is so arranged that by pressing a button when the switch is in the battery position, an intense vibrator spark is produced in the cylinder during that period when the circuit breaker is open, which will be the case during the first three-fourths of the power stroke. The current is transmitted to the distributor and passes through the spark plug of the cylinder that is on the power stroke. BATTERY TIMER INTERRUPTER "ADJUSTMENT SHORT ^-CIRCUITING TERMINAL 8ATTERY \ j CONNECTION \\ \. PLATINUM POINTS Fig. 115. Bosch Duplex Breaker. Should the engine come to a stop in such a position that the battery timer is closed, it will not be possible to produce a vibrator spark by the pressing of the button, but the releasing of the button will produce a single contact spark that will ignite the mixture and thus start the engine. Thus if the engine should stop in some odd position, and the spark is produced when the piston is slightly before top center, for instance, there will be a slight reverse impulse which will bring another cylinder on the power stroke and into the ignition circuit. The engine will thereupon take up its cycle in the proper direction. In the Bosch duplex system the coil is in series with the magneto armature, but the spark is produced under the same condition, that is, on the breaking of the circuit. In conse- quence the Bosch duplex system will permit the production 270 GAS, OIL AND STEAM ENGINES of a spark during the first three-quarters -of the power stroke by the pressing of the push button set. on the switch plate. The Bosch two independent system is composed of a separate Bosch battery system and a separate Bosch magneto. Although the operation of the coil is somewhat similar to that of the The Herz High Tension Magneto in Which the Magnets are Built up of Thin Steel Plates Without Pole Pieces (Four Cylinder Type). dual system, the nature of the battery system is such as to re- quire arrangements for two separate sets of spark plugs. The coil is not unlike that supplied with the dual system in that by pressing a button located on the switch plate a series of in- tense sparks may be produced in the cylinder at all advanta- geous points of the power stroke. CHAPTER IX CARBURETORS (105) Principles of Carburetion. The carburetor is a device for converting volatile liquid fuels, such as gasoline, alcohol, kerosene, etc., into an explosive vapor. Besides vaporizing the liquid, the carburetor also controls the proportion of the fuel to the air required for its combustion. The mixture produced by the carburetor must be a uniform gas and not a simple spray to accomplish the best results for com- plete and instantaneous combustion. Proper combustion can- not be attained with any of the fuel in a liquid state as all of the fuel contained in a liquid particle cannot come into con- tact with the consuming air. It is of the utmost importance to have the air and fuel in correct proportions so that the fuel may be completely consumed without danger of interfering with the ignition by an excess of air. With few exceptions modern gasoline carburetors are of the nozzle type in which the liquid is broken up into an extremely fine subdivided state by the suction of the engine piston. This fine spray is then fully vaporized or gasified by the heat drawn from the surrounding intake air that is drawn through the carburetor and into the cylinder on the suction stroke. Owing to the low grade fuels now on the market and to the constantly varying atmospheric conditions it is seldom possible to obtain a perfect vapor in the correct proportions, and for this reason much heat is lost that would be available were the mixture perfect. Carburetors for automobiles and boats vary in detail from those used on stationary engines due principally to the differ- ence in matters of speed. A stationary engine runs at a con- stant speed which makes adjustment comparatively easy, while automobile engines have a wide range of speeds and loads mak- ing it very difficult to maintain the correct mixture at all points in the range. The difference in the fuel and air adjustments for varying of speeds marks the principal difference between stationary and automobile carburetors. There are many types 271 272 GAS, OIL AND STEAM ENGINES of successful carburetors on the market, so many in fact that we have room for the description of only three or four of the most prominent, but we will say that the well known car- buretors are based on the same principles and differ only in matters of detail. A cross-sectional view of the well known Schebler Type D carburetor is shown by Fig. 116, and is of the type commonly used on automobile motors and boats. (106) Schebler Carburetor. The carburetor is connected to the intake of the engine by MODEL "D" Fig. 116. Cross-Section Through Type "D" Schebler Carburetor. pipe screwed into the opening R, the gas passing from the car- buretor to the engine through this opening. D is the spray nozzle which opens into the float chamber B, the opening of the nozzle being regulated by needle valve E which controls the quantity of gasoline flowing into the mixing chamber C. On the suction stroke of the engine, air is drawn through the upper left hand opening, past the partially open auxiliary air GAS, OIL AND STEAM ENGINES 273 valve A, past the needle valve D, through the mixing chamber C, and into the engine through R. The suction of the engine produces a partial vacuum in the mixing chamber C which causes the gasoline to issue from the nozzle D, in the form of a fine spray which ^is taken up by the air passing through the passage H, and is taken into the engine through R, thoroughly mixed. The amount of mixture entering the engine, and consequently the engine speed is regulated by the throttle valve K, operated by the lever P. In order that the amount of spray given by the nozzle P be constant it is necessary that the level, or height of the gasoline in the nozzle be constant. The level is maintained by means of the float F, which opens, or closes the gasoline supply valve H, opening it and allowing gasoline to enter when the level is low, and closing the valve when the level is high. The carburetor is connected to the gasoline supply tank, by pipe connected to the inlet G, through which the gasoline flows into the float chamber B. The float chamber carries a small amount of gasoline on which the float F rests. The richness of the mixture is controlled by opening or closing the nozzle needle valve E, which passes through the center of the nozzle D. The float F surrounds the nozzle in order to keep the level of the liquid constant when the carburetor is tilted out of the horizontal by^ climbing hills, or by the rocking of the boat when used on a marine engine. A drain cock T is placed at the bottom of the float chamber for the purpose of removing any water, or sediment that may collect in the bottom of the float chamber. At low speeds, the auxiliary air valve A lies tight on its seat, allowing a constant opening for the incoming air through the space shown at the bottom of the valve. When the speed of the engine is much increased, the vacuum is increased in the mixing chamber C, which overcomes the tension of the air valve spring O and allows the valve to open and admit more air to the mixing chamber. The action of the auxiliary air valve keeps the mixture uniform at different en- gine speeds, as it tends to keep the vacuum constant in the mix- ing chamber. When the engine speed increases, the flow of gasoline is greater, and consequently more air will be required to burn it; this additional air is furnished by the automatic action of the valve, and when once adjusted, compensates accurately for the different engine speeds. 274 GAS, OIL AND STEAM ENGINES The gasoline is generally supplied by a tank elevated at least six inches above the level of the fluid in the float chamber; al- though in some cases the gasoline is supplied by air pressure on a tank situated below the level of the carburetor. In some types of Schebler carburetors, the float chamber B is surrounded by a water jacket that is supplied with hot water from the cylinder jackets of the engine. This keeps the gasoline warm so that it evaporates readily under any atmospheric con- ditions. The quantity of air admitted to the carburetor is controlled by an air valve shown in the air intake by the dotted lines. This is adjusted by hand for a particular engine and is seldom touched afterward. When starting the engine it is necessary to have a very rich mixture for the first few revolutions, this mixture being ob- tained by "flooding" the carburetor. On the Schebler carburetor the mixing chamber is flooded by depressing the "tickler" or flushing pin V. (107) Two Cycle Carburetors. Nearly any type of carburetor can be used on a two port, two stroke, cycle engine providing a check valve is placed between the crank case and carburetor to prevent the crank-case com- pression from forcing its contents back through the inlet pas- sages. A great many manufacturers make special carburetors for two stroke motors that have the check valve built into the carburetor itself. With three port two stroke cycle engines a check valve is not necessary as the piston in this type of engine performs this duty. In that class of vaporizers known as mixing valves, the valve that controls the flow of gasoline blocks the air passage in such a way that an additional check valve is not necessary. (108) Kingston Carburetors. The Kingston Carburetor shown by Fig. 117 differs from the Schebler in many details, the principal difference being in the construction of the spray nozzle and the construction of the auxiliary air valve. The throttle valve E controlls the exit of the mixture through the engine connection C which is an ex- tension of the mixing chamber. The spray nozzle J which is surrounded by a hood or tube is controlled by the needle valve A which is threaded into the top of the mixing chamber, this GAS, OIL AND STEAM ENGINES 275 latter adjustment being locked into place by a button head screw and a slot in the casting. Surrounding the nozzle tube or hood is a curved restriction in the air intake passage, is known as a Venturi tube, which insures a constant relation between the air and fuel supplies. As the action of the Venturi tube is rather complicated, it will not be taken up in detail. Air is supplied to the Venturi passage through the intake (D). An annular float (K) sur- rounds the mixing chamber that acts on the gasoline sup- ply valve (I) through a short lever arm. This valve is acces- sible for cleaning on the removal of the cap H that covers the Fig. 117. Cross-Section Through Kingston Carburetor Showing Balls Used for Auxiliary Air Valves. valve chamber. Gasoline enters the float chamber through the fuel pipe G, and enters the spray nozzle through the two ports in the base of the mixing chamber. The auxiliary air valve is a particularly novel feature of this carburetor, as no springs nor disc valves are used in its con- struction. Five balls (M) of different weights and sizes act as air valves, the balls covering the inlet ports (L) under nor- mal operation. As the speed increases, the balls are lifted off their seats in order of their weight or size by the increase in 276 GAS, OIL AND STEAM ENGINES suction. With a slight increase of suction, the lightest ball cov- ering the smallest hole is lifted first, a further increase in suc- tion lifts the next largest ball which still further increases the auxiliary air intake, and so on until at the highest speed all of the balls are off their seats. Access ID the ball valves is had through the valve caps (N). The constant supply inlet is circular and may be set at any desired angle, as can the float chamber and gasoline supply connection. Control and adjust- ment are entirely by the needle valve. (109) The Feps Carburetor. The Feps carburetor has the main needle valve surrounded by a Venturi chamber as in the preceding case, the needle valve adjustment being made through a lever on the left of the mix- ing chamber. An auxiliary nozzle directly under the auxiliary air valve at the right, connects with the float chamber and furnishes an additional mixture of gasoline and air for hill climbing and high speed work when the leather faced auxiliary air valve lifts from its seat. The adjustment for this auxiliary jet is shown at the right of the air valve chamber. For intermediate speeds, the air valve alone is in action. No controlling springs are used on the air valve which insures posi- tive action and sensitive control of the air. A float surrounding the Venturi tube controls the fuel valve through the usual lever arm. A wire gauze strainer placed in the fuel chamber to the left prevents dirt and water from being drawn into the nozzle, and as this strainer easily removed it is a simple matter to clean and prevent the troubles due to dirty fuel. By closing the upper valve in the vertical engine connection the vacuum is increased in the manifold when starting the en- gine. This increase of vacuum draws gasoline from the float chamber and primes the engine making the engine easy to start in cold weather. The tube through which the gasoline is drawn for priming is the small crooked tube bending over the float and terminating above the starting valve. Below this valve is the throttle valve which controls the mixture in the ordinary man- ner. The adjustment for intermediate speeds is made by the center knurled thumb-screw shown over the air valve chamber which controls the travel of auxiliary air valve. In effect this is a double carburetor, one jet for high speed and one for low. GAS, OIL AND STEAM ENGINES 277 (111) Gasoline Strainers. Much trouble is caused in carburetors by dirt, water and sediment, collecting in the small passages and obstructing the flow of the gasoline. The purpose of the gasoline strainer is to prevent any water Fig. 119. The Excelsior Carburetor in Which the Air is Regulated by a Ball which Lies in the Tapering Venturi Tube. An Increase of Suction Lifts the Ball and Allows More Air to Pass. or foreign matter from being carried into the carburetor, and this device should be used on every engine if the owner wishes to be free from carburetor troubles. (112) Installing Gasoline Carburetors. (1) Use brass or copper pipe from the tank to carburetor if possible to avoid trouble from dirt and flakes of rust. (2) When installing a gasoline tank be sure that the bottom of the tank is at least six inches above the carburetor to insure a good flow. 278 GAS, OIL AND STEAM ENGINES (3) The tank should be provided with an air vent hole, or the gasoline will not flow because of the vacuum in the top of the tank* (4) All tanks should be provided with a drain cock at the lowest point so that water and dirt may be easily removed. (5) Clean out the tank thoroughly before rilling with gaso- line to avoid clogged carburetors. (6) Pipes from the tank to carburetor should never be placed near exhaust pipes or hot surfaces for the gasoline vapor may prevent the feeding of gasoline. (7) Clean out pipes before using. (8) If common threaded pipe joints are used on the gasoline piping, use common soap in place of red lead. (113) Installing the Carburetor. The carburetor should be placed as near to the cylinder as possible, the shorter the pipe, the less the amount of vapor condensed in the manifold. With multi-cylinder engines the carburetor should be so situated, that is, an equal distance from each cylinder, so that each cylinder will inhale an equal amount of vapor. The intake opening of the pipe should be placed near one of the cylinders, or draw warm air off the surface of the exhaust pipe in order that gasoline will evaporate readily in cold weather, and form a uniform mixture at varying temperatures. Great care should be taken to prevent any air leaks in the carburetor, or intake manifold connections, as a small leak will greatly reduce the strength of the mixture and cause irregular running. Always use a gasket between the valves of a flanged connection and keep the bolts tight. If a brazed sheet brass manifold is used, look out for cracks in the brazing. Leaks may be detected in the connections by spurting a little water on the joints, and turning the engine over on the suction stroke. If the water is sucked in the leaks should be repaired at once. Make sure when placing gaskets, that the gasket does not obstruct the opening in the pipe, and that it is securely fastened so that it is not drawn in by the suction. Never allow the carburetor to support any weight, as the shell is easily sprung which will result in leaking needle valves. CARBURETOR ADJUSTMENT. When adjusting the car- buretor of multiple cylinder engine, it is advisable to open the muffler cutout in order that the character of the exhaust may be seen or heard. With the muffler open, the color of GAS, OIL AND STEAM ENGINES 279 the exhaust should be noted. With a PURPLE flame you may be sure that the adjustment is nearly correct for that load and speed; a yellow flame indicates too much air; a thin blue flame too much gasoline, and is not the best for power. Before starting for the adjustment test, try the compression, and the spark. If the compression is poor, try the effects of a little oil on the piston, which may be introduced into the cyl- inder through the priming cup. It will be well to dilute the oil to about one-half with kerosene. After all trouble with all the parts are clear, you may start the engine. Turn on the gasoline at the tank, and after standing a moment see whether there is any dripping at the carburetor, if there is, the trouble will probably be due to a leaky float, dirt in the float valve, or to poor float adjustment. Locate the leak and remedy it before proceeding further. Dirt on the seat of the needle valve may sometimes be removed by "flooding" the car- buretor, which is done by holding down the "tickler" lever for a few seconds, causing the gasoline to overflow, and wash out the dirt. If the motor has been standing for a time it would be well to "prime" the motor by admitting a little gasoline into the cyl- inder through the priming cup, or by pushing the tickler a couple of times so as to slightly flood the carburetor. Now turn on the spark and turn over the engine for the start, taking care that the throttle is just a little farther open than its fully closed position. If the engine takes a few explosions and stops, you will find the nozzle, or that some part of the fuel pip- ing is clogged which will stop the engine. If the motor grad- usually slows down, and stops, with BLACK SMOKE issuing from the end of the exhaust pipe, or MISFIRES badly, the mix- ture is TOO RICH, and should be reduced by cutting down the gasoline supply by means of the needle valve adjusting screw. If it stops quickly, with a BACKFIRE, or explosion at the supply of gasoline should be INCREASED by adjusting the mouth of the carburetor, the mixture is TOO LEAN, and the needle vaW, In all cases be sure that the auxiliary valves are closed when the engine is running slowly, with the throttle closed, as in the above test. If they are open at low speed, the mixture will be weakened and the test will be of no avail. After adjusting the needle valve as above until the engine is running (with throttle in the same partially closed position), turn the valve slowly in one direction or the other until the 280 GAS, OIL AND STEAM ENGINES motor seems to be running at its best. During the above tests the spark should be left retarded throughout the adjustment, and the throttle should not be moved. The carburetor should now be tested for high speed adjust- ment, by opening the throttle wide (spark l /4 advanced), and observing the action of the motor. If the engine back-fires through the carburetor at high speed, it indicates that the mix- ture is too weak which may be due to the auxiliary air valve spring tension being too weak and allowing an excess of air to be admitted. Increase the tension of the spring, and if this does not remedy matters, admit a little more fuel to strengthen the mixture by means of the needle valve adjustment. Do not touch the needle valve if you can possibly avoid it, or the high-speed adjustment, as the fuel adjustment will be disturbed for low speed. If the engine misfires, with loud reports at the exhaust, does not run smoothly, or emits clouds of black smoke at high speed, the engine is not receiving enough air in the auxiliary air valve, consequently the tension of the spring should be reduced. Back firing through the carburetor denotes a weak mixture. Trouble in cold weather may be caused either by slow evapo- ration of the gasoline, or by water in the fuel that freezes and ob- structs the piping or nozzle. In cold weather a higher gravity of gasoline should be used than in summer, as it evaporates more readily, and therefore forms a combustible gas the rate at lower temperatures. To increase the rate of evaporation of the gasoline, it should be placed in a bottle and held in hot water for a time before pouring it into the carburetor or tank, or the air inlet warmed with a torch. The cylinder water jacket should always be filled with hot water before trying to start the engine, and will prevent the gas from condensing on the cold walls of the cylinder. Often good results may be had by wrapping a cloth or towel around the carburetor, that has been dipped in hot water. The cylinder of an air-cooled engine may be warmed by gently applying the heat of a torch to the ribs, or by wrapping hot cloths about it. The tank, piping, and carburetor should be drained more frequently in cold weather than in hot, to prevent any accumu- lation of water from freezing, and stopping the fuel supply. A gasoline strainer should always be supplied on the fuel line, and should be regularly drained. The motor may often be made to start in cold weather by GAS, OIL AND STEAM ENGINES 281 cutting out the spark, and cranking the engine two or three revolutions with the throttle wide open. The throttle should now be closed within J/ of its fully closed position, the ignition current turned on, and the engine cranked for starting. This system will very seldom fail of success at the first attempt. Carburetor flooding is shown by the dripping of gasoline from the carburetor, and which results in too much gasoline in the mixture. Flooding may be caused by dirt accumulating under float valve, by a leaking float (Copper Float), by Water Logged Float (Shellac worn off Cork Float), by float adjust- ment causing too high a level of gasoline, by leaking float valve, by cutting out ignition when engine is running full speed, by rust or corrosion sticking float valve lever, by float binding in chamber, by float being out of the horizontal, by float valve binding in guide, by excessive pressure on gasoline, or by tickler lever held against float continuously. Dirt accumulated under float valve may sometimes be flushed out by depressing tickler lever several times; if this does not suffice, the cap over the valve must be removed, and the orifice cleaned by wiping with a cloth. LEAKING FLOAT VALVES should be reground with ground glass or very fine sand; never use emery as the par- ticles will become imbedded in the metal, which will be the cause of worse leaks. Should the shellac be worn off of a cork float allowing the gasoline to penetrate the pores of the cork, a new float should be installed, as it is a doubtful policy for owner to give the float an additional coat of shellac. MISFIRING AT LOW SPEED. If the carburetor cannot be adjusted to run evenly on low speed after making all pos- sible adjustments with the needle valve, the trouble is prob- ably due to air leaks between the carburetor and engine, caused by broken gaskets, cracked brazing in the intake manifold, or by leaks around the valve stem diluting the mixture. INCORRECT VALVE TIMING will cau*e missing, espe- cially on multiple cylinder engines, as the carburetor cannot furnish mixture to several cylinders that have different indi- vidual timing. Look for air leaks around the spark edge open- ings, and be sure that all valves seat gas tight. Always be sure that the auxiliary air valve remains closed at low speeds, as a valve that opens at too low a speed will surely cause mis- firing as it dilutes the mixture. MISSING in one cylinder may be caused by an air leak in that cylinder. 282 GAS, OIL AND STEAM ENGINES WATER in gasoline will cause misfiiing, especially in freez- ing weather, as it obstructs the flow of fuel to the carburetor. The carburetor and tank should be drained at regular inter- vals, and if possible, a strainer should be introduced in the gasoline line. CLOGGED NOZZLE. Particles of loose dirt in the nozzle will occasion an intermittent flow of gasoline that will result in misfiring. The nozzle should be cleaned with a small wire run back and forth throughout the opening. CLOGGED AIR VENT in the float chamber will change the level of the fuel, and will either "starve" the engine, or flood the carburetor. The air in the float chamber is a very small hole, and is likely to clog. HOT FUEL PIPE. If the fuel pipe that connects the tank with the carburetor, becomes hot, due to its proximity to the exhaust pipe of cylinders, vapor will be formed in the pipe that will interfere with the flow of fuel. DIRT UNDER AUXILIARY AIR VALVE will prevent the valve from seating properly, causing the engine to misfire at low speed. CRACKS OR LEAKS in intake pipe or gaskets will cause intermittent leaks of air and spasms of misfiring. Old cracks that have been brazed will sometimes open and close alter- nately causing baffling cases of spasmodic misfiring. DIRT IN AIR INTAKE will change the air ratio, and the increased suction will cause a greater flow of gasoline. Do not place the end of the inlet pipe in a dusty place, nor where oil can be splashed into it by the engine. Clean out periodically. "LOADING UP" of the inlet piping in cold weather on light load is caused by the mixture condensing in the intake pipe. The only remedy is to keep the piping warm, or to heat the inlet air. CLOGGED OVERFLOW PIPE, with engines equipped with pump supply will cause flooding, as the fuel does not return rapidly enough to the tank. (114) Kerosene Vaporizer for Motorcycles. An ingenious vaporizing device has been designed for the use of kerosene as a fuel for motorcycle engines, by the M. G. and G. Motor Patents Syndicate, Ltd., England, is described in Motor Cycling. The device consists of a comminuter, or vapor- izer, which screws into the sparkling-plug hole in the cylinder, the plug being transferred to an aperture in the vaporizer, a GAS, OIL AND STEAM ENGINES 283 feeder for regulating the supply of fuel to the vaporizer, and a throttle and air barrel, or mixing chamber, for the purpose of proportioning the amount of air and gas supplied to the en- gine, and for controlling the speed of the machine as in an ordinary carburetor. The feeder receives the fuel in this case kerosene although any heavy oil can be used with almost equally good results. The feeder answers a purpose similar to the ordinary float chamber of the carburetor, i. e., to regulate the amount of kero- sene it is required to pass through the vaporizer. It consists of a small chamber mounted upon the end of a pipe leading to the vaporizer. Kerosene is fed to this device by a copper pipe from the tank, and enters at the lowest point through a 3/16- inch hole or jet. This is covered by a small valve, operated by engine suctiofl. The lift of this valve can be adjusted by the insertion of washers to suit any particular size of engine, just as one would use various size jets to suit either a large or small engine. One of the greatest advantages of the device lies in the size of this aperture or jet, inasmuch as it cannot possibly choke up with grit, and even water will pass through and not stop the operation of the carburetor. At the top of the feeder is an air hole, which admits just sufficient air to pass the kero- sene through the vaporizer, the reason for this being that the heat of the vaporizer shall only act upon the fuel, the mixture afterwards being balanced by air being admitted through the mixing chamber. After the kerosene leaves the feeder it passes through a pipe to the vaporizer. This consists of a gunmetal body with cool- ing ribs cast on the outside, whilst through the center runs a thin copper tube of ^-inch diameter and only 20 gauge, which would really melt during the heat of combustion were it not for the fact of the fuel passing through it. The heat derived from this formation of vaporizer is approximately 1,000 degrees Fahr. Inside the central tube is a strip-steel spiral, which serves the double purpose of giving a centrifugal motion to the fuel, and at the same time forming a supporter for the tube, prevent- ing it crushing under the force of the explosions. It is, of course, understood that the inside of the feeding tube is en- tirely isolated from the combustion chamber. The sparking plug is screwed into the wall of the vaporizer, which is now really an extension of the combustion chamber. Obviously this slightly reduces the compression of the en- gine, which, however, is a necessary feature when kerosene is 284 GAS, OIL AND STEAM ENGINES used as a fuel. After passing through this device the kerosene is thoroughly vaporized, and the vapor is led through a flexible pipe to the throttle chamber; this taking the place of an ordinary carburetor and being fitted to the induction pipe. There are two slides, operated by Bowden levers from the handle-bar, one being for the main air intake and the other for the gas. Undoubtedly the greatest claim for this vaporizer is the fact that practically no carbon deposit forms upon the inside of the Fig. 121-a. The English Aster Electric Lighting Unit. cylinder or on the piston. What little deposit is formed takes the shape of small, soft flakes, which, instead of adhering to the cylinder walls, break away before they have attained any size and are blown through the exhaust valve. Altogether, this de- vice seems to have finally solved the problem of using kerosene as a fuel on air-cooled engines, especially if the carbon deposit difficulty has been finally overcome. The device was fitted to a Z l / 2 h. p.' Matchless with a White and Poppe engine. In order to start up, a small gasoline tank, holding about one half-pint of gasoline, is fitted under the main tank and communicates with the feeder. Half a minute is all that is necessary running on gasoline, when the kerosene can be turned on. The machine would fire at a walking pace, and could also be accelerated up to 55 m.p.h. CHAPTER X LUBRICATION (116) General Notes on Lubrication. No matter how carefully the surface of a shaft or bearing may be finished, there always remains a slight roughness or burr of metal, which although of microscopic proportions is produc- tive of friction or wear. Each minute projection of metal on a dry shaft acts exactly as a lathe tool, when the shaft revolves in cutting a groove in the stationary bearing. Since there are a multitude of these projections in a journal, the wear would be very rapid, and would in a short time completely destroy either the shaft or bearing, no matter how highly finished in the beginning. When lubricating oil is introduced into a bearing it imme- diately covers the rubbing surface, and as the oil has a con- siderable resistance to being deformed, or is "stiff," it separates the surface of the shaft from that of the bearing for a distance equal to the thickness of the oil film. With ordinary lubricants this distance is more than enough to raise the irregularities of the shaft out of engagement with those of the bearing. This property of "stiffness" in the oil is known as "viscosity." The value of viscosity varies greatly with different grades of oil, and also with the temperature with the result that the allowable pressure on the oil per square inch also varies. With oils of low viscosity a small pressure per square inch on the bearing will squeeze it out, and allow the two metallic surfaces to come against into contact, causing wear and friction, while an oil of greater viscosity will successfully resist the pressure. The life and satisfactory operation of the engine depends al- most entirely upon the lubricant and the devices that apply it to the bearings. Excessive wear and change in the adjust- ments are nearly always the result of defective lubricating de- vices or a poor lubricant. The principal lubricants are: (1) Solid lubricants such as graphite, soapstone, or mica. (2) Semi-solid lubricants such as vaseline, tallow, and soap 285 286 GAS, OIL AND STEAM ENGINES emulsions, or greases compounded of animal fats, vegetable and mineral oils; and (3) Liquid lubricants, such as sperm oil, or one of the prod- ucts of petroleum, the latter medium being the class of lubri- cant ,most suitable for internal combustion engines, owing to its combining the qualities of a high flash-point with a compara- tive freedom from either acidity or causticity. Oils of animal or vegetable origin should never be used with gas engine as the high temperatures encountered will char and render them useless. Tallow and lard oil are especially to be avoided, at least in a pure state. . In the cylinder only the best grade of GAS ENGINE cyl- inder oil should be used, which according to different makers has a flash point ranging from 500 to 700 degrees. Using cheap oil in the cylinder is an expensive luxury. In general, the oils having the highest flash points have also the objectionable ten- dency of causing carbon desposits in the combustion chamber and rings which is productive of preignition and compression leakage. The lower flash oils have a tendency to vaporize and to carry off with the exhaust which will leave the walls insuffi- ciently lubricated unless an excessive amount is fed to the cyl- inder. By starting with samples of well known brands rec- ommended by the builder of the engine it will be an easy mat- ter to find which is the cheapest and gives the best results. In figuring the cost of oil do not take the cost per gallon as a basis, but the cost for so many hours of running, or better yet the number of horse-power hours. Unless you are fond of buy- ing replacements and new parts do not stint on the oil supply. On the other hand, an excess of oil should be avoided as this means not only a waste of oil through the exhaust pipe, but trouble with carbon deposits and ignition troubles as well. Foul igniters, misfiring, and stuck piston rings are the inevitable result of a flood of lubricating oil. When a whitish yellow cloud of smoke appears at the end of the exhaust pipe, cut down the oil feed. The exhaust should be colorless and prac- tically odorless. Too much oil cannot be fed to the main bearings of the crank shaft if the waste oil is caught, filtered and returned to the bearings by a circulating system, for the flood of oil not only insures ample lubrication but removes the heat generated as well. The bearings require a much lighter oil, of a lower fire test than the cylinder oil. It is evident that its viscosity is a most important element, as it determines the allowable GAS, OIL AND STEAM ENGINES 287 pressure on the shaft. The viscosity of an oil varies with the temperature and is greatly reduced at cylinder heat. A com- parative test of the viscosity or load bearing qualities of an oil may be made by making bubbles with it by means of a clay pipe; the larger the bubble, the higher the viscosity of the oil. Different sizes of bearings, and bearing pressures, call for oils of different viscosities, and consequently an oil that would be suitable for one engine would not answer for another; heavy bodied oils being used for heavy bearing pressures, and light thin oil for small high speed bearings. The best way to deter- mine the value of an oil for a particular shaft bearing is by experiment, attention being paid to its adaptability for the feeding devices used. The compression attained in a gas engine cylinder depends to a certain extent upon the body of the cylinder oil, for many engines that leak compression past the rings with thin oil will work satisfactorily with a heavy viscuous oil that clings tightly to the surfaces. An engine will often lose compression when an oil of poor quality is used. Air cooled engine cylinders require an oil of heavier body than water cooled because of the higher temperature of the cylinder walls. Gum and sticky residue are usually formed by animal oils or adulterants added to the numeral oil base. Oils containing free acids should be avoided as they not only cor- rode and etch the bearing, but also clog the oil pipes or feeds with the products of the corrosion. Free acid is left from the refining process, and may be deter- mined by means of litmus paper inserted into the oil. If the litmus paper turns red after coming into contact with the oil, acid is present, and the oil should be rejected. The following are the characteristics of an oil suitable for use on an engine: (a) The oil must be viscous enough to properly support the bearings or to prevent leakage past the piston rings. (b) It should be thin enough so that it can be properly handled by the oil pumps, or drip freely in the oil cups. (c) It should not form heavy deposits of oil in the cylinder and cause the formation of "gum." (d) It should contain no free acid. Ordinarily a good grade of fairly heavy machine oil will be suitable for use on the bearings of the average engine, such as the cam-shaft and crank-shaft bearings. Only very light clean oil, or vaseline should be used on ball- 288 GAS, OIL AND STEAM ENGINES bearings, as heavy greases and solid lubricants pack in the races and cause binding or breakages. Flake graphite is much used as lubricant, and too much can- not be said in its favor, as it furnishes a smooth, even coat over the shaft, fills up small scores and depressions, and makes the use of light oil possible under heavy bearing pressures. With graphite, less oil is used, as the graphite is practically perma- nent, and should the oil fail for a time, the graphite coat will provide the necessary lubrication until the feed is resumed without danger of a scoring or cutting. In fact, when graphite is used, the oil simply acts as medium by which- the graphite is carried to the bearings. If graphite is injected into the cylinder in small quantities it greatly improves the compression, as it fills up all small cuts and abrasions in the cylinder walls. A good mixture to use for bearings is about \ l /2 teaspoonsful of graphite, to a pint of light machine oil, thoroughly mixed. Graphite can be placed in the crank chamber of a splash feed engine, by means of an insect powder gun. Trouble with oil cups is always in evidence during cold weather, as the oil congeals, and does not drip properly into the bearings. The fluidity of the oil can be increased in cold weather by the addition of about ten per cent of kerosene to the oil. If too much oil is fed to the cylinders, the piston rings will be clogged with gum, and a loss of compression, or a tight piston will be the result. An excess of oil will short-circuit the igniter or sharp plugs, and will form a thick deposit in the combustion chamber that will eventually result in preignition or back-firing. Deposits and gum formed in the cylinder will cause leaky valves and a loss of compression. Feed enough oil to insure perfect lubrication, but not enough to cause light colored smoke at the exhaust. Lubricating systems may be divided into three principal classes: Sight-feed, splash system, and the force feed system. Sight feeding by means of dripping oil cups is too common to require description, and is used on many stationary engines, both large and small. The splash system is in general use on small high speed engines both stationary, and of the automobile type. The force feed system in which oil is fed under pressure by a pump is by far the most desirable as the amount of oil fed is given in positive quantities proportional to the engine speed, GAS, OIL AND STEAM ENGINES 289 and with sufficient pressure to force it past any ordinary ob- structions that may exist in the oil pipe. Another system that is half splash, and half force feed, is the pump circulated system much used in automobiles. THE SPLASH FEED SYSTEM is the simplest of all, as the bearings are lubricated by the oil spray caused by the con- necting rod end splashing through an oil puddle located in the bottom of the closed crank case. The piston and cylinder are lubricated by the spray, as well as the bearings, as the lower end of the piston projects into the crank chamber at the moment that the connecting rod end strikes the oil puddle. To maintain constant lubrication, it is necessary that the oil in the puddle be kept at a constant height, or as in some cases be varied in such a way that the surface of the puddle is raised and lowered in proportion to the load on the engine. In the average engine the oil level is maintained by overflow pipes or openings that allow any excess of oil over the fixed level to flow back to the pump. In the Knight engine the puddles are formed in movable cups which are connected with the throttle in such a way that the opening of the throttle raises the oil level and supplies more oil to the engine at the greater load, or speed. Oil in splash systems is supplied by a low pressure pump, usually of the rotary type, in the base of the engine. Oil from the pump passes to the bearings, drops into the puddle, over- flows through the overflow opening, and returns to the pump through a filter, the same oil being used over and over again until exhausted. This strainer should be removed occasionally and the dirt removed, for should it be allowed to collect it is likely to obstruct the oil supply. The oil should be replaced before it becomes too black or foul, the crank case and bear- ings thoroughly cleaned with kerosene, and new oil replaced. The supply may be interrupted by the failure of the pump, caused by sheared keys or leakage of air in the suction line due to cracks. It would be well to run the engine for a few min- utes with the kerosene in the crank case, in order that all of the oil may be removed. See that the drain cock is closed at the bottom of the cylinder or all of the oil will be lost. Lock the valve handle carefully so that it cannot jar open. If light colored smoke appears in intermittent puffs with a multiple cylinder engine, it indicates that one cylinder is receiving too much oil. 290 GAS, OIL AND STEAM ENGINES (117) Force Feed Lubricating System. The force feed system is by far the most reliable of all oil- ing systems, as it feeds uniformly and continuously at almost any temperature, and against the pressure of practically any ob- struction in the pipe. The oil is supplied by a small pump driven from the engine, the pump being incased in the oil tank housing. Frequently a hand pump is used in combination with the power pump when starting the engine, or at times when the power pump is out of service. A single pump is used with any number of leads, each lead, of feed, having an independent regulating valve and sight feed, or a pump unit may be provided for each lead, depending on the size of the engine. (118) Bosch Force Feed Oiler. The force feed of the Bosch Oiler is so positive in character, that the flow of oil is not affected by heavy back-pressure due to elbows and the diameter of the conducting pipes. Springs, valves and other devices, which would check the flow of oil, are fundamentally eliminated. The amount of oil fed may be accurately and permanently regulated. Glands and other pack- ings and bushings are eliminated. Connecting rods and all links are eliminated by the direct application of the movements of the oscillating cam disks to the pump plungers and piston valves. Each feed of this oiler is provided with a separate pump ele- ment consisting of a pump body plunger and a piston valve, the suction and feed ducts connecting directly with the pump body of their respective elements. With this construction, pump elements may be replaced or added. The oiler requires no attention other than to be supplied with oil; and the open- ing and closing of the valves, pet cocks, etc., on starting and stopping the machine is rendered unnecessary. The correct and regular operation of the elements may be verified by ob- servation of the reciprocating movements of the regulating screws. Each pump plunger is provided with an adjusting screw through which the feed may be regulated from to 0.2 cubic centimeters for each stroke. The Bosch Oiler (Fig. 121) being positively driven by the machine that it supplies, the oil fed is in all cases proportional to the engine speed; overloads are thus automatically taken care of. GAS, OIL AND STEAM ENGINES 291 The circular arrangement of the elements of the Bosch Oiler permits the device to be driven by a single shaft, and the oil is forced through the feeds from a single reservoir to the required points of application. A pump element consists of a pump body 1, a pump plunger 2 and a piston valve 3, and is supported on the base plate 13. The elements are ar- 20 " 13 Top View of Bosch Force Feed Oiler. ranged concentrically about the drive shaft in such a manner that the pump plungers form a circle around the circle formed by the piston valves. The pump cam disk 20 and the valve cam disk 22 are set on the drive shaft at other than a right angle with its axis, and the rims of the disks are gripped by slots formed in the heads -36 25 Fig. 121. Cross-Section Bosch Oiler. of the pump plungers and piston valves. The relation of these cam disks is such that the valve cam disk is 90 in advance of the plunger cam disk. The valve ca^ri disk is solid on the drive shaft, but the pump cam shaft is Voose and driven through a lug on the valve cam disk. When the drive of the pump is 292 GAS, OIL AND STEAM ENGINES reversed, the lug on the valve cam disk frees itself and again takes up the drive of the pump cam disk, after the drive shaft has made a half revolution. Regulating screws 4 are set in the slotted heads of the pump plunger, and by means of this the back-lash or play of the cam disk may be regulated. The regulating screws are pro- vided with lock nuts, and project through the cover of the oil tank housing, being exposed by the removal of the filler cover 42. The filler opening is provided with a removable strainer to prevent the entrance of foreign particles into the oil tank. Pump shaft 14 is driven through worm gear 23 which meshes with worm 24 on drive shaft 25; drive shaft 25 projects from the oiler housing, and is coupled with the driving shaft of the machine to be lubricated. Base plate 13 is attached to the oiler cover by three stud bolts, thus permitting the removal of the entire oiler mechanism from the housing. The quanitity of oil in the oil tank is shown by gauge glass 44. On the starting of the machine to which the oiler is attached, the pump shaft and the cam disks that it supports are set in motion through worm 24 and worm gear 23. A direct recipro- cating motion is given to the pump plunger and to the piston valve by the rotation of the cam disks which have a move- ment similar to that of the "wobble saw." The relation of the cam disk is such that the piston valve movements are 90 in advance of the movements of the pump plungers. The pump will run in either direction without alteration. To secure this effect a play of 90 is provided between the cam disk. When cam 22 is driven clockwise, cam disk 20 is driven by the lug which meshes with a lug on disk 22. The cams are then in such a relation that the cam valve disk is 90 in advance of the pump cam disk. When reversed, cam 20 re- mains at rest until cam 22 catches the lug and cam 20, when the drive continues as before. The cams are then in the same relation as previously for as the valve disk 22 has traveled through 180 it is evident that it is 90 in advance of the pump disk. (119) Castor Oil for Aero Engines. Castor oil is used almost exclusively in the Gnome and other rotary engines of the same type, but has not been particularly successful on stationary cylinders. Chemically, castor oil differs from all other vegetable or ani- GAS, OIL AND STEAM ENGINES 293 mal oils in containing neither palmitine or olein. It is soluble in absolute alcohol, but practically insoluble in gasoline. On the other hand, the castor oil is capable of dissolving small quantities of mineral oil, the more fluid they are the less it absorbs of them. But the insolubility of castor oil in min- eral oil disappears completely when it is mixed with even a very small quantity of another vegetable or animal oil, such as colza or lard oil. An adulteration may thus result in a serious reversal of the oil's best qualities; in fact, in serious seizures. Castor oil does not attack rubber, but it contains 1 to 2 per cent of acid fats; sometimes more. "In my opinion says a writer in 'Autocar' castor oil can only be used in fixed cylinders with impunity for short distances and then with repeated cleanings between runs, but on rotary engines of the Gnome type cleaning is almost unnecessary. The reason is that one cannot .consistently use castor oil over and over again, for the fact is indisputable that it has a far greater tendency than mineral oils to absorb oxygen, and so gradually to increase in body and finally to gum. When once it com- mences to gum the carbonization becomes more rapid, because the thickened and pitch-like oil acts as an insulating covering on the top of the pistons and of the cylinder, and cannot get away with sufficient rapidity to avoid decomposition and bak- ing to a coke. Therefore if castor oil is to be used on the ordinary stationary cylinder type of engine, it is necessary to wash out the crank chamber and to replace with fresh oil at frequently intervals. On a rotary engine such as the Gnome this cleaning is unnecessary, because there is a continuous stream of fresh castor oil brought into the crank chamber and then thrown by centrifugal force past the pistons and through the cylinder into the exhaust. Thus the stream of oil never has sufficient time to oxidize fully, gum or decompose. This action of centrifugal force accounts for the large consumption of oil on the rotary engine, and also for the fact that the pistons and cylinders keep comparatively clean. "In thus criticizing the use of castor oil I do not wish it to be inferred that it is not an excellent lubricant. What I wish to suggest is that in the case of an internal combustion engine it must be made with discretion. A point in favor of castor oil is the fact that it maintains is viscosity in a remarkable man- ner at high temperatures, and that at those high temperatures it has a peculiar creeping or capillary action which enables it to spread uniformly over the whole of the metallic surfaces. 294 GAS, OIL AND STEAM ENGINES whereas under the same conditions a similarly bodied mineral oil would be unevenly distributed in patches. Another point is that the specific heat of castor oil is considerably higher than that of a pure mineral oil. This is in its favor, insomuch that it shows castor oil to be a better heat remover than a mineral oil. "Motorists and aviators have from time to time informed me that they are using castor oil, but have apparently been under some misapprehension. I find that they have been using a brand of prepared oil under the impression that it is a specially refined castor oil, or that it is a blend of castor oil." Producer Gas Engine Plant at Gottingen, Germany, Consisting of Four 3,500 Horse-Power Units. A simple method for testing the purity of castor oil is at the disposal of all. It is known as the Finkener test. Ten cubic centimeters of castor oil is placed in a graduate. Five times as much alcohol, 90 per cent, is added and stirred in. The solution should remain clear and brilliant at 15 to 20 degrees C. An admixture of foreign oils, even if only 5 per cent, riles the solution at this temperature, though not above it. (120) Force Feed Troubles. The most common trouble with force feed systems is the fail- ure of the operator to remove the dirt collected by the strainer. The oil piping should be cleaned out at least once every year by means of a wire and gasoline, to remove any gum that inay have been deposited. Driving belts should be kept tight GAS, OIL AND STEAM ENGINES 295 to prevent slipping, and belts that are soaked with oil should be cleaned with gasoline and readjusted. Leaking pump valves generally of the ball type are a com- mon cause of failure. They may leak because of wear or by an accumulation of grit and dirt on. their seats, which prevents the valves from seating properly. If the valves leak,* the oil will be forced back into the tank, or will not be drawn into the pump cylinder at all, depending on whether the inlet or discharge valve is the offender. Plunger leakage which is rare will cause oil failure. If the oil pipes that lead to the bearings rub against any mov- ing part, or against a sharp edge, a hole will be worn in the pipe, a leak caused which will prevent the oil from reaching the bearing. A dented or "squashed" pipe will prevent the flow of oil. The set screw or pin holding the pulley to the pump shaft may loosen and cause it to run idly on the shaft without turn- ing the pump. This will of course, prevent the circulation of oil. The worm and worm wheel may wear so that the pump is no longer driven by the pulley shaft, or a poor pipe connection may leak all that the pump delivers. The amount of oil required by each lead- or bearing should be carefully determined by experiment, and kept constantly at the right number of drops per minute. The feed adjustments jar loose, and should be inspected fre- quently. (121) Oil Cup Failure. Oil cups should be cleaned out frequently with gasoline or kerosene, as any gum or lint will interfere seriously with the feed. They should be adjusted and filled frequently to prevent any possible chance of a hot bearing. Oil cups should be as large as possible in order that they may be left for considerable periods without danger of a hot box. Cold weather affects the oil feed to a considerable extent, especially with small oil cups, and they should be kept as warm as possible. When heavy oils are used a cold draft will stop the feed. Oils may be made more fluid in cold weather by the addition of about ten per cent of kerosene. (122) Hot Bearings. A hot bearing is almost a sure sign of insufficient oil, and the trouble should be located and remedied immediately. Oil 296 GAS, OIL AND STEAM ENGINES pumps stopping, clogged oil pipes or holes, frozen oil, or oil leaks are common causes of hot bearings. Never allow an engine to run with a hot bearing for any length of time, as the bearing or piston may seize tight and wreck the engine. Inspect the journals frequently to see if they are above normal temperature. A hot, binding bearing often causes the effect of an overload on the engine, slowing it down, and increasing the governor and fuel feed, this is followed in a short time by the bearing seizing. (123) Cold Weather Lubrication. It is by no means uncommon trouble in cold weather to find excessive fluctuations in pressure as the engine speed and tem- perature of the oil varies. Thus, if the pressure be set correctly with the engine running fast, and when just started up, it will be found, after half-an-hour's running, that, with the engine turn- ing slowly, the pressure is far too low, owing to the oil having become thin. If the pressure be then reset, it may be found on next starting up from cold that the gauge goes hard over, and may very easily be burst if the engine is run fast. The point is one to which many designers of engines pay far too little attention, though the difficulty may be very easily gotten over. The secret lies in having the by-pass outlet of most ample proportions, so that the excess of oil, however thick, can get away quite easily. If there is any throttling of the by-pass, back pressure must result with consequent increase of the pressure at which the by-pass valve comes into opera- tion. In other words, the pressure of the main supply to the bearings will be increased. A writer to "The Motor," London solved this problem in the following manner: "Originally, the by-passage was somewhat small, little larger than the oil delivery pipe to the engine, which was about 3/16 inch bore, and the result was that the pressure when starting with the oil cold rose to about 25 pounds per square inch, and fell to about one pound per square inch with the oil hot and the engine running slow. It was possible, however, to bore out the by-pass passage and fit a larger pipe, about three times the area of the main delivery pipe, with the result that the oil, when cold, never rose above about 15 pounds per square inch, however fast the engine run. When thor- oughly heated, the normal running pressure was about 6 pounds per square inch, falling to 2 pounds per square inch with GAS, OIL AND STEAM ENGINES 297 the engine only just turning over, which brings up the ques- tion of the correct working pressure. This will vary very largely with the design of the engine, but, broadly speak- ing, the higher the pressure the better for the bearings. The limiting figure is determined by the tendency of the engine to throw out oil at the end of crankshaft bearings, and by the amount that gets past the piston rings. Obviously, an engine with new, tight bearings and new piston rings will stand a higher pressure without undue waste of oil or excess deposit in the cylinder head than will an old engine with worn bearings and slack rings. And, again, the question will be affected by Brookes Gasoline-Electric Generating Units for Operating Search Lights. An Independent Unit is Used for Each Light. the design of the pistons. For instance, where the trunk of the piston is bored for lightness, much more oil will get past the rings than in cases where a 'solid' trunk is employed. Roughly speaking, 8 to 15 pounds per square inch is a good figure for a new, high-speed engine. An old and worn engine, particularly if not of a high-speed type, may require no more than 2 to 6 pounds per square inch." "The writer recently encountered a rather curious difficulty in connection with obtaining a free by-pass. The return pipe from the by-pass led into the case carrying the gearwheels of the camshaft and magneto drive, and oil continually flooded out 298 GAS, OIL AND STEAM ENGINES from the end of the camshaft and other bearings. The waste and mess were sufficiently serious to warrant investigation, and the cover plate over the gears was accordingly taken off. It was then noticed that the oil delivered to the gearwheel case had only two small holes by which to drain away to the crank- case. The flow from the by-pass was beyond the proper ca- pacity of these holes, and so the whole gearwheel case became filled with oil under considerable pressure, quite possibly 2 or 3 pounds per square inch, and it was not surprising that oil exuded from the ends of the bearing. A few extra limber-holes, if one may borrow a nautical expression, were drilled through to the crankcase, and no further trouble was experienced." (124) Plug Oil Holes When Painting. When the chassis of the car is repainted it is well to see that all exposed oil holes are stuffed with waste to prevent them from being choked. Failure to observe this precaution may result in the holes being clogged with paint, which if not removed before the car is started, will prevent oil reaching the bearings. (125) Oiling the Magneto. Never oil the circuit breaker or circuit breaker mechanism, unless for a drop of sperm oil that may be applied to the cam roller by means of a toothpick. If oil gets on the circuit breaker contact points, it will cause them to spark badly, resulting in pitting or destruction of the points. If the oil is occasionally applied to the cam roller or should oil accumulate on breaker points, the breaker should be rinsed out with gasoline to re- move the surplus. Pitted or carbonized contact points are capable of causing much trouble, and gummy oil or dirt will develop this trouble quicker than any other cause. Use only the best grade of thin sperm oil on the ball bearings. In the course of time the circuit breaker contact points will wear or burn, causing imperfect contact, and too great a separa- tion between the points. The contacts should be examined from time to time, and if rough or pitted, should be dressed down to a flat even bearing by means of a dead smooth file, and the distance readjusted. The contacts should not bear on a corner or edge, but should bear evenly over their entire sur- face to insure a maximum primary current and spark. CHAPTER XI COOLING SYSTEMS The object of the cooling system is not to keep the cylinder cold, but to prevent the heat of the successive explosions from heating the cylinder walls to a degree that would vaporize the lubricating oil and prevent satisfactory lubrication of the cyl- inder and piston. The hotter the cylinder can be kept without interfering with the lubricating oil, the higher will be the effi- ciency of the engine and the greater the output of power. To obtain the greatest power from an engine, the heat devel- oped by the combustion should be confined to the gas in order that the pressure and expansion be at a maximum, it is evident that the pressure and power will be reduced by over-cooling as the heat of the expanding gas will be taken from the cyl- inder and transferred to the cooling medium. The temperature of the cylinder, and therefore the efficiency of the engine is determined principally by the vaporizing point of the lubricat- ing oil, and consequently the higher the grade of the oil, the higher the allowable temperature of the cylinder. If cold water from a hydrant or well be forced around the water jacket rapidly, the power will be greatly reduced owing to the chilling effect on the expanding gas. There is not much danger in keeping the cylinder of an air cooled engine too cool, in fact the great difficulty with this type of engine is to keep it cool enough to prevent an excessive loss of lubricating oil. The valves, particularly the exhaust valves, should be sur- rounded with sufficient water to keep them cool as they are subjected to more heat than any other part of the engine, and are liable to wrap or pit. The water leaving the jacket of a gasoline engine should not exceed 160 F., as temperatures in excess of this amount cause deposits of lime scale. When possible, a portion of the cooling water should be run into the exhaust pipe immediately after it has completed its flow around the valves and cylinders, as the water cools the gas so suddenly that the exhaust to atmosphere is rendered almost noiseless, and the exhaust pipe is kept much cooler and 299 300 GAS, OIL AND STEAM ENGINES less liable to cause fire by coming into contact with combustible objects. On some engines the exhaust pipe is water jacketed for some distance to prevent dirty rusty pipes in the vicinity of the efigine mechanism and also to prevent injury to the operator should he come into contact with the pipe. Small engines and medium size vertical engines usually have the water jacket cast in one piece with the cylinder casting and others have a separate head that is bolted to the cylinder. In the latter type the water flows from the cylinder to the head thryugh ports or slots cut in the end of the cylinder water jacket that register with similar slots in the jacket of the head. Thus in this construction we have not only to pack the joint to prevent leakage of gas from the cylinder, but also to prevent the leakage of cooling water from the jacket into the cylinder, or outside. Thus there is always a chance of water leaking into the cylinder bore and causing trouble unless the packing is very carefully installed and looked after. In large horizontal engines the gas and water joints are never made at the same point, as it would be practically impossible to prevent leakage into the cylinders of such engines. When the cylinder and cylinder water jackets are cast in one piece without a water joint at the junction of the cylinder and the head, the water connection between the head and the cylinder being made by pipes external to the castings. Small, portable, stationary engines are sometimes "HOPPER COOLED," or cooled by means of the evaporation of the water contained in an open water jacket that surrounds the cylinder. The hopper is merely an extension of the water jacket such as used on all water cooled engines, the only difference being that the top of the hopper is open permitting the free escape of water vapor or steam to the atmosphere. The water level should be carried within two inches from the top of the hopper. Water when converted into vapor or steam absorbs a great quantity of heat, and of course the steam carries the heat of evaporization with it when it escapes to the atmosphere. As the hopper is open to the air, the temperature of the cylinder^cannot exceed 212 F. (temperature of boiling water) as long as there is sufficient water left to cover the cylinder. The hoppers contain sufficient water for runs of several hours' duration, and as the water boils away or evaporates, it may be replenished by simply pouring more water in the top of the GAS, OIL AND STEAM ENGINES 301 hopper. Hopper cooling is used principally for small portable engines where the weight of a water tank or other cooling device would be objectionable and also where there is danger of freezing the pipes and connections of other systems. The loss of water by evaporization is from .3 to .6 of a gallon per horsepower hour; that is, for a 5 hp. engine the loss would be from 1.5 to 3 gals, for every hour that the engine was oper- ated under full load. Thr cylinder and the water jacket are cast in one integral piece, with no joints of any kind in either the combustion cham- ber or in the water jacket. A system of cooling by which the heat of the walls is radiated Fig. 124. Air Cooled "Grey Eagle" Aeronautical Motor. Note the Depth of Cooling Ribs. to the air directly without the medium of water is often used on small high speed engines, and is known as "AIR COOLING." This type of cylinder is surrounded with radiating ribs or spires which increases the radiating surface of the cylinder to the extent that the required amount of heat is lost to allow of economical lubrication. This system is desirable where the weight of radiators and water would be a drawback, where it would be inconvenient to obtain water, or where there would be trouble from freezing. An air cooled motor generally is provided with a fan that increases* the efficiency of the radiat- ing surface by changing the air between the ribs. With aero- nautical- motors such as the Gnome, and Gray Eagle, shown by Fig. 124, the circulation of the air due to the propeller and 302 GAS, OIL AND STEAM ENGINES the rush of the aeroplane is sufficient to thoroughly cool the machine. As a rule, the air cooled motor is made more efficient in fuel consumption than the water cooled type because of the high temperature of the cylinder walls. In fact all engines are air cooled eventually, whether the heat is radiated at a high tem- perature by the fires, .or at a lower temperature through the circulating water and radiator. When the engines are of the portable type, and likely to be used out of convenient reach of water, the hopper or EVAPO- RATOR TANK system is used, the tank system being used for the larger engines. In effect, the tank system is the same as the hopper cooler, the heat being dissipated principally by evaporation, although some heat is radiated from the surface of the tank itself. The difference between the two systems is merely one of size, the tank offering a greater area for the emission of heat than the hopper. A tank-cooled engine has one pipe running from the top of the cylinder to a point near the top of the tank, the bottoms of the cylinder and tank being connected together by another pipe. When the water becomes heated in the cylinder, it expands and becomes lighter than the cold water in the tank and con- sequently rises to the surface of the water in the tank through the upper pipe. As the warm water flows into the tank, it is immediately replaced by the heavier cold water that flows into the cylinder from the bottom of the tank through the lower pipe. This successive discharge of the heated water from the cylinder to the tank sets up a continuous flow of water through the water jacket of the cylinder, which transfers the excess heat of the cylinder to the tank where it is dissipated to the atmosphere by evaporation and radiation. The circulation of the cooling water set up by the action of heat or the expansion of the water is called Natural or Thermo Syphon circulation. Cooling tanks may be used profitably with stationary en- gines if the tank can be located so that vapor and steam pro- duced will not be objectionable. If the tank is used inside of a building, the vapor should be conveyed to the outside air by means of a stack or chimney, or by means of a small ventilating fan driven by the engine. The water consumption of a cooling tank is from .3 to .6 gallons per hour, the exact quantity varying with the atmos- pheric conditions and temperature, GAS, OIL AND STEAM ENGINES 303 For engines of from 10 to 50 horsepower a battery of cooling tanks may be used, the number depending on the size of the engine. To maintain the proper temperature under varying loads, one or more tanks may be cut out of service when the Hall-Scott Aeroplane Motor Mounted in Martin Biplane. Radiator Shown Above Motor and in Front of Top Wing. load is changed. For natural circulation, the tank should be installed so that the bottom of the tank is above the bottom of the cylinder. If placed much lower a pump should be used. 304 GAS, OIL AND STEAM ENGINES If water is used from the city mains from 10 to 15 gallons will be required per horsepower hour, the exact quantity varies with the temperature of the supply. The water from very large stationary engines is cooled by allowing it to trickle down through a cooling tower, which is built somewhat like the screen cooler only on a larger scale, built somewhat like the screen cooler only on a larger scale. The object of the cooling tower is to present the greatest pos- sible surface of water to the air, this is accomplished by screens or baffles that turn the water over and over as it falls. The water, well cooled, finally collects in a cistern at the base of the tower from which it is pumped back to the engine and thus is used over and over again. This is an ideal system when water is expensive and when engines of considerable power are used. (126) Cooling System Troubles. Overheating caused by deposits of scale or lime in the jacket is one of the most common causes of an excessively hot cyl- inder. When hard water containing much lime is heated, the lime is .deposited as a solid on the walls of the vessel forming a hard, dense, non-conducting sheet. When scale is deposited on the outside of the cylinder walls it prevents the transfer of the heat from the cylinder to the cooling water and consequently is the cause of the cylinder overheating. Besides acting as an insulator or heat, the deposit also causes trouble by obstructing the pipes and water passages, diminishing the water supply and aggravating the trouble. Scale interferes with the action of the thermo syphon system more than with a pump, as the pressure tending to circulate the water is much lower. Whatever system is used, the scale should be removed as often as possible, the number of removals de- pending, of course, on the "hardness" of the water. Large horizontal engines are usually provided with hand holes in the jacket, th'rough which access may be had to the interior surfaces on which the scale collects. Under these conditions the scale may be removed by means of a hammer and chisel. The scale may be softened by empt3nng half the water from the jacket and pouring in a quantity of kerosene oil, the inlet and outlet pipes being stopped to prevent the escape of the oil. The engine should now be started and run for a few minutes GAS, OIL AND STEAM ENGINES 305 with the mixture of kerosene and water in the jacket; no fresh water being admitted during this time. After the mixture has become boiling hot, stop the engine and allow it to cool; it will be found that the scale has softened to the consistency of mud, and may easily be washed out of the jacket. The work of removing the scale can be reduced to a minimum by filling the jacket with a solution of 1 part of Sulphuric Acid and 10 parts of water, allowing it to stand over night. The scale will be precipitated to the bottom of the jacket in the form of a fine powder and may be easily washed out in the morning. If the jacket water is kept at a temperature above 185 F. the amount of scale deposited will be nearly doubled over that deposited at 160 F. Wash out sand and dirt occasionally, a strainer located in the pump line will help to keep the jacket clear and free from for- eign matter. If a solution of carbonate of soda, or lye, and water are al- lowed to stand in the cylinder over night, the deposit will be softened and the work with the chisel will be made much easier. If a radiator is used (automobile or aero engine) the deposit can be removed with soda, never use acid, lye, or kerosene in a radiator or. with an engine with a sheet metal water jacket. Obstructions in Water Pipes. Poor water circulation may be caused by sand, particles of scale, etc., clogging the water pipes, or by the deterioration of the inner walls of the rubber hose connections. Sometimes a layer of the rubber, or fabric of the hose may loosen from the rest and the ragged end may obstruct the passage. A sharp bend in a rubber hose may result in a "kink" and en- tirely close the opening. The packing in a joint may swell, or a washer may not have the opening cut large enough, either case will result in a poor circulation. Sediment is particularly liable to collect or form in a pocket, pipe elbow, or in the jacket opposite the pipe opening. Oil should be kept off of rubber hose connections as it will cause them to deteriorate rapidly, this may finally result in water circulation troubles. Rubber pipe joints between the engine and the radiator or tanks are advisable as they do not transmit the vibration of the engine, and hence reduce the strain on the piping. A strainer should be provided in order to reduce the amount of foreign material in the water. Radiators. A clogged radiator will give the same results 306 GAS, OIL AND STEAM ENGINES as a clogged jacket with the exception that steam will issue from the radiator if the circulation is not perfect. If the radiator becomes warm over its entire surface it is evident that the water is circulating, the temperature being a rough index of the freedom of the water, or the interior con- dition of the surfaces. A leaking radiator may be temporarily repaired with a piece of chewing gum. Should the radiator be hot and steaming at the top and remain cold at the bottom for a time, it shows that the water is not circulating and that the jackets on the cylinders are full of steam. Such a condition usually is indicative of clogging be- Natural Gas Plant at Independence, Kansas, Used for Pumping Gas From the Wells to Various Distributing Points. tween the bottom of the radiator and pump, between the pump and bottom of cylinders, or of a defective pump. Thermo-syphon radiators are more susceptible to the effects of sediment and clogging than those circulated by pumps. A radiator may fail to cool an engine because of a slipping or broken belt driving the fan, or on account of a loose pulley or defective belt tension adjuster. Keep the belt tight. The fan may stick on account of defective bearings. Radiator may be AIR BOUND, due to pockets or bends in the piping holding the air. Rotary Pump Defects. A defective circulating pump will cause overheating, as it will supply little if any water to the jackets. GAS, OIL AND STEAM ENGINES 307 Examine the clutch or coupling that drives the pump and see that the key or pin that fastens it to the shaft is in place. Next see that the driving pinion and gear are in mesh and properly keyed to their respective shafts. In some cases the shaft has been twisted off, or the coupling pin sheared through by reason of the shaft rusting to the pump casing. Worn gears or impellers IN THE PUMP reduce the output and cause heating, as will a sheared driving pin in the impeller. Wear and bad impeller fits reduce the capacity of the pump. Scale or sediment collecting in the pump sometimes strips the pins or impeller teeth. Note the condition of the gaskets or whether the pump shaft is receiving the proper amount of grease. Put a strainer in pump intake. See that no leak occurs on pump intake pipe. To avoid the trouble and expense due to cracked water jackets, never neglect to drain the cylinders and piping from all water in freezing weather. Drain cocks should be provided at the lowest points in the water circulating system for this purpose. It would be well to provide an air cock at the highest point in the line in order that all of the water can drain out as soon as the drain cock is opened. With automobile or portable engines it is not always con- venient or possible to drain the engine every time that it is stopped and consequently we must resort to a "non-freezing" mixture or at least a solution that will not solidify under ordi- nary winter temperatures. Such a solution should be chosen with care, as many will cause the corrosion and destruction of the jackets and piping; NEVER USE COMMON SALT and water under any conditions. Wood alcqhol and water in equal parts, is often used for automobiles, but is rather expensive for portable engines hav- ing a comparatively great amount of water in circulation. Unless the circulating system is absolutely air tight, as it is when radiators are used, alcohol will be lost by evaporation and must be replaced frequently. The most practical solution for the average engine used, is made up by dissolving about five pounds of CALCIUM CHLORIDE in one gallon of water. This mixture will stand a temperature of about 15 F below zero, and if diluted to half the strength will not freeze above zero. Use CALCIUM CHLORIDE, not ordinary Salt (Sodium Chloride). CHAPTER XII GOVERNORS AND VALVE GEAR (127} Hit and Miss Governing. When the speed of an engine is held constant for varying loads by missing explosions on the light loads and increasing the number for heavy loads, the governing system is said to be of the "hit and miss type." The mixture remains constant in quantity and quality in this type of engine. A hit and miss governor allows only enough charges to be fired to keep the speed constant. When the load falls off, with a natural 1 tendency on the part of the engine to increase its speed, the governor cuts out the next explosion by holding the exhaust valve open and the inlet closed, thus preventing fresh mixture from being drawn into the cylinder. With an increase in load, the governor allows the valves to follow their regular cycle with the result that a greater or less number are fired in succession. Hit and miss governing is very economical for only full charges of the most perfect mixture are fired, and with short exhaust pipes the scavenging is much better than with other forms of governing. The principal difficulty with this system is that the regulation is not as perfect as with some other types. (128) The Throttling System. Unlike the hit and miss system of governing, the throttling type of governor allows the engine to take an explosion on every working stroke, the speed being held constant by either regulating the quality or quantity of the mixture, or both. Throttle governor permits of close speed regulation as the im- pulses are more frequent and not so violent as with the hit and miss system. The governor acts directly on the throttle valve, and at no time is the operating mechanism disengaged from the driving cam. The throttle governor engine is particularly well adapted 'for driving dynamos, supply electric light, as the uniform speed 308 GAS, OIL AND STEAM ENGINES 309 gives a smooth, steady light without the objectionable flickering so likely with the hit and miss engine. To obtain the best fuel economy with a throttling engine, it should be run close to its rated capacity, as the poor and imperfect mixture admitted at light loads considerably increases the fuel consumption. Practically all motors of the variable speed type such as are used on automobiles and motor boats are controlled manually by the throttle; although marine motors are often fitted with Fig. 76-d. De La Vergne Governor. governors to prevent racing when the screw is lifted out of the water in a heavy sea. (129) The Controlling Governor. The governor proper depends upon centrifugal force for its action, and generally consists of two weights which are pivoted at one end to a rotating shaft driven by the engine. When these weights are rotated rapidly the bottoms are thrown out- wardly by the centrifugal force and tend to assume a horizontal position. The faster the weights are rotated, the greater will be the tendency for the bottoms of the weights to come into the horizontal, and the greater will be the pressure exerted by them on the controlling levers connected to the throttle. It is evident that the centrifugal pull on the weights varies' directly 310 GAS, OIL AND STEAM ENGINES Fig. 124-d. Governor and Governor Mechanism of Fairbanks-Morse Type "R E" Engine. The Fly-Balls, Springs, and Control Rods Are Shown on the Governor Staff. The Upper End of the Bell Crank Goes to the Throttle. with the speed of rotation and consequently with the speed of the engine. The exact relation between the travel of the weights and the speed of the engine is controlled by a spring that acts between arms cast on the weights and the spindle. If a heavy spring is used, greater speed must be attained to move the weights a given distance than with a weak spring, as the centri- fugal force must be greater. GAS, OIL AND STEAM ENGINES 311 The throttle valve of the engine is connected by a rod to the governor through a sliding collar in such a way that the move- ment of the governor weights due to an INCREASE of speed partially closes the valve until the speed of the engine is re- duced. Should the speed of the engines DECREASE, owing to a heavy load coming on, the spring will force the balls to occupy a lower position which will increase the valve opening until the engine again reaches the normal speed for which the tension of the spring is adjusted. Thus the speed of the engine is kept practically constant by the action of the governor in opening and closing the throttle, which in turn, varies the QUANTITY of mixture admitted to the cylinder. The QUALITY of the mixture is varied by hand, in the engine by means of cocks in both the air and gas pipes. The GOVERNOR PROPER is of practically the same con- struction in the hit and miss engine, the difference of the two 'types lying in the method of connecting it to the controlling system. In one case (hit and miss) the governor controls the exhaust valve, and in the other (throttling) it controls the quan- tity of gas admitted by the throttle valve. The speed of the engine may be varied within certain limits by a lever connected to the valve controlling rod. (130) Types of Governors. The types of governors used o-n the leading makes of en- gines will be found described and illustrated in Chapter V which treats of each engine in detail. (131) Governor Troubles. Hit and miss governor troubles may be due to the following defects: BINDING GOVERNOR COLLAR, stuck with dirt or gummy oil, will cause the engine to die under load, and overspeed on light load. INLET VALVE LOCK may be worn in such a manner as to prevent the valve from seating during the idle strokes and lose fuel, or cause overspeeding. DETENT LEVER KNIFE EDGE may be worn, or rounded off, so that the exhaust valve is not held open for the idle stroke. This defect will cause overspeeding. SPEED CHANGING LEVER may work loose and cause the speed to vary erratically. GOVERNOR WEIGHTS may be stuck on pins with dirt or gummy oil causing engine to overspeed. 312 GAS, OIL AND STEAM ENGINES LOST MOTION IN GOVERNOR GEAR such as loose pins and bushings, worn rollers, or bearing surfaces will cause the speed to vary continuously. LOST MOTION on portable en- gines will cause the engine to run normally in one position, and overspeed in another. WEAK OR BROKEN SPRINGS ON GOVERNOR will cause engine to lose speed or die down altogether. Springs may be stiffened by pulling out the coils. DRY GOVERNOR BEARINGS or joints will cause binding and cause governor to act sluggishly. Use plenty of lubricant. WORN ROLLERS may cause a speed variation. Keep the governor well oiled, clean, and free from gum. If the knife edges are allowed to slip over one another, much wear is caused on the cams and if allowed to continue, sooner or later the engine will run away. Springs will weaken with age and hard usage. With belt driven governors see that the belt is tight and that the lacing is in good condition for a slack belt may allow the engine to overspeed. I advise that every purchaser of an agricultural motor read his instruction book with care, that is, locate all oil holes and note the action and purpose of every part. If in doubt as to any part of its use write the manufacturer of the motor. (132) Throttling Governor Troubles. STICKING GOVERNOR VALVE will cause the engine to overspeed; remove the gum and dirt. LOOSE PINS OR BUSHINGS, or lost motion in any part of the governor mechanism will cause irregular motion or run- ning; be sure that the bearings and joints are well oiled. STUCK PINS will cause the engine to overspeed on light loads, and fall down on the normal load, or cause racing. WEAK OR BROKEN SPRINGS will cause the engine to lose speed or to lie down altogether even on light loads. STIFF GOVERNOR SPRINGS cause the engine to speed up. SLIDING COLLAR stuck will cause racing or a fluctuation in the speed. Keep the governor well oiled, clean, and free from gum. The governing valve should be removed from its care fre- quently and thoroughly cleaned with kerosene. Deposits of carbon and gummed oil at this point are dangerous because of the likelihood of their causing overspeeding. (133) Valve Gear Arrangement. The valve operating mechanism lay-out depends upon the cyl- GAS, OIL AND STEAM ENGINES 313 inder and valve arrangement, and consequently varies in detail with different engines. Fig. F-14-15 in Chapter V, shows the valve gear of an upright engine having the inlet and the exhaust valves located in pockets placed at one side of the cylinder. The inlet valve is operated by a valve rod that is actuated by the cam. The ex- haust valve stem is raised and lowered, directly, through a cam on the same shaft. The method of driving the valves in this 314 GAS, OIL AND STEAM ENGINES engine is practically standard for all vertical engines having the valves located in pockets. This system is used in a greater proportion of automobile engines. The opposed engine has the cylinders arranged on opposite side of the crank case, and makes an exceedingly well balanced and quiet running engine; as there is no point in the revolution where either the crank throws or connecting rods have an un- equal angularity, or differ in velocity. While this type of two cylinder engine is common in automo- bile practice, it is not often met with in stationary work, the cam-box and the cam being directly in the center of the crank case. The opposed type of engine is particularly well adapted for aeroplane service as a steady, quiet running engine is an absolute necessity because of the frail construction of the aeroplane frame. (134) Cam Shaft Speeds. The valves of the gas engine are opened and closed by means of cams or eccentrics, that are geared to the crankshaft, and which also control the timing. As a four stroke cycle engine performs all of the events, or a complete cycle in two revolutions of the crankshaft, it is evident that the cam must go through the routine in one revolu- tion or must revolve at ONE-HALF OF THE CRANKSHAFT SPEED. Therefore the cam gear ratio must be as one is to two, the smaller gear being placed on the crankshaft, the gears being known as the "half time gears." As a two stroke cycle engine goes through the routine of events in every revolution, the cam-shaft must run at crank- shaft speed so that the cam out-line makes one revolution in the same time as the crank. The cam shaft speeds given here apply to all engines of the corresponding cycle no matter whether the valves are of the poppet, rotary or slide-sleeve types. (135) Valve Gear Troubles. The valve gear mechanism causes trouble principally through the wear of the various parts which results in a change in the valve timing, or in the lift of the valves. Loss of power, MIS- FIRING, and overheating are the result of such derangements. Often trouble is caused in reassembling the valve mechanism GAS, OIL AND STEAM ENGINES 315 after the engine has been torn down for repairs, which trouble may generally be traced to incorrect gear meshing. The following list will give the principal defects due to the wear of the valve mechanism. (a) WORN CAM GEARS change timing because of play, or "back lash" in the teeth, or cause a howling or grinding noise, that will cause the owner to believe that the end of the engine is near. MISFIRING and LOSS of power are probable results of a change in the timing. If any of the teeth are stripped from the gear you may be sure that the timing is changed. Replace- ment with a new gear is the only cure for a worn or broken gear. (b) GEARS NOT IN PROPER MESH due to an error in assembling the gears, will prevent the engine from being started, or cause misfiring and loss of power. The maker of the engine generally marks the teeth that go together, but if no such marks appear, the owner should center punch or scratch them before taking down the engine. (c) A GEAR SLIPPING ON THE SHAFT, due to a mis- sing key in the gear, or to a loose set-screw will cause all of the troubles due to a change in the timing. Examine the key carefully, for dirt often collects in the key-way to such an ex- tent that it is liable to be mistaken for the key. Keys and pins have sheared in two, allowing the shaft to slip in the gear. (d) WORN CAM-SHAFT BEARINGS are the cause of trouble, as they will change both the timing and the lift of the valves. If much play exists in the bearing, it will prevent the valves from lifting at the proper time, and will also reduce the lift by the amount of the play, which sometimes has a con- siderable effect on the free passage of the gases. If the cam- shaft bearings are of the bushing type they should be replaced with new paying attention at the same time to the condition of the shaft. If rough or shouldered the shaft should be machined to a dead smooth surface. If on a large engine and of the ad- justable type, the shims should be removed as required or the wedges adjusted. (e) LOOSE CAMS OR ECCENTRICS will change the tim- ing because of lost or sheared keys. If your cams are not in- tegral with the shaft, look them over occasionally and be sure that the keys are tight. Loose cams will produce thumping and grinding and may often be located by the sound. See that the key-way is not worn when fitting keys. If the cams are fitted with taper pins it would be well to ream 316 GAS, OIL AND STEAM ENGINES the hole before placing new pins, as there is a liability of the hole being worn oval. (f) A TWISTED OR SPRUNG CAM-SHAFT will change the positions of the cams relative to one another, and not only will change the time of all cylinders, but will change their time relatively causing the engine to run out of balance, or produce an unusual vibration. (g) WORN CAMS are causes of a change of timing on all types of engines, and are the most frequent cause of reduced valve lift with its consequent trouble of overheating. If the outline or contour of a cam is changed with wear it should be replaced, if keyed to the shaft, as it will be a constant source of trouble. If the cams and cam-shaft are in one integral piece, it will be necessary to replace the entire shaft. (h) WORN CAM ROLLERS AND ROLLER PINS will reduce the lift of the valves, and in the case of a broken or sheared pin will prevent the valve from lifting at all. Always replace loose pins or loose rattling roller. (i) PUSH ROD DEFECTS. Too much clearance between the push rod and valve stem will reduce the lift of the valves and change the timing. The clearance for small engines should be equal to the thickness of a visiting card, and for large engines is somewhat larger, say 1-16". The increase of clearance is due principally to wear. Too small a clearance should be avoided for the reason that the valve stems expand with the heat and will lift the valves too soon, or even permanently until readjusted. Broken valve springs will cause trouble, or lost keys that retain the valve spring washers. Loose adjusting screws on the push rods or stripped threads will delay the valve opening. (j) TAPPET LEVER DEFECTS are generally caused by wear or poor adjustment. Loose pins or bushings, too much clearance between the tappet and valve stem or broken valve springs, or loose adjusting screws will produce changes in the timing or valve lift (k) BENT VALVE ROD. A bent valve rod will shorten the travel of the valves, and change the timing. (1) CAM LEVER OR PIN will cause timing troubles if the pin or bushing are loose or worn, by reducing the travel of the valves. When occasion arises for the removal of valves, the oppor- tunity should be taken to clean the stems and guides, which may be more or less gummed with ancient oil. Freedom of GAS, OIL AND STEAM ENGINES 317 valve movement is of extreme importance, and for this reason neither the cleaning nor the lubrication of the stems and guides should be neglected. The occasional use of a little kerosene will prevent gummy accumulations, but care should be taken not to allow the kerosene to wash out all of the oil and thereby leave the surfaces dry. A broken valve spring, though not a common occurrence, is not an unknown possibility. If no spare spring is at hand, a plan that can be recommended is to turn the broken spring end for end, thus bringing the finished ends up together; this will prevent the spring from shortening by overlapping, and wind- ing itself together. (136) Valve Timing. The exact time at which the valves of a four stroke cycle engine open and close depends to a great extent upon the speed of the engine, the fuel used, the compression pressure, and the relation of the bore to the stroke. As these items vary in nearly every make of engine there has appeared in the technical press, a great mass of seemingly conflicting data. Engine speed is the principal factor in de- termining the timing. Correct valve timing plays a considerable part in the output and efficiency of an engine, for if the inlet valve, for example, opens too late, the cylinder will not receive a full charge. If it opens too early the hot gases in the cylinder will ignite the gas in the carburetor and cause back-firing. Should the ex- haust open too late, the retention of the hot gas in the cylinder is likely to cause overheating. The timing of the valves is usually expressed in degrees of the circle described by the crank-pin, or the angle formed by the crank with the center line of the cylinder at the time the valve is to open or close. (137) Valve Setting on Stationary Engines. The exhaust should open when the crank lacks 30 of com- pleting the outer end of the power stroke, that is, the crank should make an angle of 30 with the center line of the cylinder when the exhaust valve begins to open, and should be inclined AWAY from the cylinder. Some makers have the exhaust open a little later in the stroke, but little is to be gained with a later opening as the retention of the charge beyond 30 heats the cylinder and does very little towards developing power. The 318 GAS, OIL AND STEAM ENGINES only advantage of the late opening is that the valve opens against a lower pressure and causes slightly less wear on the parts. The exhaust valve should close 5 AFTER the crank has passed the INNER dead center on the exhaust or scavenging stroke, although some makers close the valve exactly on the dead center. The 5 should be given to allow the gas all possible chance of escape. The piston is said to be on the inner dead center when it is in the cylinder as far as it will go, and on the outer dead center when it is on the center nearest the crank- shaft. The INTAKE valve should open about 5 AFTER the exhaust valve closes, or 10 after the crank passes the inner dead center. The inlet valve should NEVER open before the exhaust valve closes on a low speed engine. The above timing is for engines running 150-600 R.P.M. The automatic type of inlet valve, of course, cannot be timed, but attention should be paid to the strength and tension of the spring and the condition of the valve stem guides. The inlet valve should close 10 AFTER the crank passes the outer dead center in order that the cylinder be filled to the full- est possible extent." If the valve closed exactly on the dead center a partial vacuum will exist and the charge retained in the cylinder will be comparatively small, but if the valve re- mains open past this point the air would have time to completely fill the cylinder and develop the capacity of the engine. The longer the inlet pipe, the longer the inlet valve opening. (138) High Speed Engine Valve Timing. The faster a motor turns, all other things being equal, the greater the amount of advance necessary with the valves, as the higher the speed the less the time required to fill or empty the cylinder. In a short stroke high speed motor the exhaust should close and the intake open as early as possible in order to admit the full charge. The exhaust should open early to allow of the full escape of the gases, as the time allowed for expulsion is ex- tremely short when an engine runs 1,000 R.P.M. and the back pressure is liable to be considerable. The inlet valve of high speed engines should remain open for a considerable period after the crank passes the outer dead center on the suction stroke, owing to the inertia of the gases which tends to fill the cylinder. Lengthening the period of opening of the inlet valve in multiple cylinder engines produces GAS, OIL AND STEAM ENGINES 319 better carbureting conditions and reduces the variations of pres- sure in the manifold. EXHAUST VALVES. The exhaust valve should begin to open 40 BEFORE the crank reaches the OUTER dead center on the working stroke, and should close 10 AFTER the crank has passed the inner dead center. INLET VALVES. The inlet valve should open 15 AFTER the crank passes the inner dead center on the suction stroke, and should close 35 after the crank passes the outer dead center. The inlet valve should never open before the exhaust valve closes, although this is done on several types of high speed aeronautical engines. The makers of these engines claim that this practice scavenges the combustion chamber more thor- oughly and makes the mixture more effective owing to the in- ertia of the burnt gases forming a partial vacuum in the com- bustion chamber. The writer has never been able to get satis- factory results with this timing and doubts whether it can be accomplished successfully. In timing an engine great care should be taken to get the crank exactly on the dead center. (139) Timing Offset Cylinders. The only difference in timing engines with offset cylinders and timing those with the center line of the cylinder in direct line with the crank shaft, is in the locating of the dead center. With no offset, the center of the cylinder, the crank pin and the crank shaft are all in one direct line when the engine is on the dead center. With offset cylinders the crank pin lies to one side of the cyl- inder center line when on the dead center, on either the inner, or the outer center. To find the center on an offset engine proceed as follows: Turn the engine over slowly until the crank-pin reaches either the extreme top or bottom point of the crank circle, depending on which center is to be determined, and then turn very slowly until the centers of the piston-pin, crank-pin, and crank-shaft are in line. With the average engine this will be found a dif- ficult and tedious job, and it will be well to mark the dead cen- ter on the flywheel or other convenient point to prevent a rep- etition of the job. The quickest method of accomplishing the feat is to remove the spark plug or relief cock to gain access to the piston, and insert a rod or pointer in the opening thus provided. 320 GAS, OIL AND STEAM ENGINES Draw the piston back a short distance from the end of the stroke with the pointer resting on the head of the piston, and mark this position of the piston both on the pointer, and on the flywheel, using some stationary part of the engine as a reference point. Now turn the crank over the center line until the piston is moving in the opposite direction, and is the same distance from the end of the stroke as shown by the mark on the pointer. Mark this position on the flywheel using the same reference mark as before. We now have two marks on the flywheel, and will bisect the distance between them, using the dividing mark to obtain the center. Place the bisection mark even with the reference point used for obtaining the two previous marks on the flywheel, and the engine will be on the true dead center, as the flywheel is now midway between two points of equal stroke. (140) Auxiliary Exhaust Ports. To decrease the amount of hot gas and flame passing over the exhaust valve some makers provide their engines with auxiliary exhaust ports, which are similar to the exhaust ports used on two stroke cycle engines. The auxiliary exhaust consists of a series of holes drilled or cored through a rib on the cylinder wall, the holes freing so situated that they are covered by the piston until it is at the extreme end of its outward stroke. The holes are not un- covered until the burning charge has been expanded and cooled to the greatest extent possible in the cylinder. As soon as the piston uncovers the ports the greater portion of the dead gas escapes instantly to the atmosphere, carrying with them the greater percentage of the heat and flame. The small amount of residual gas that remains is forced out through the exhaust valve in the usual manner, thus no flame ever reaches the exhaust valve. The use of auxiliary exhaust ports produces a cooler cylinder as the gas passes over the cylinder wall only once, and conse- quently is in contact with the walls only one-half of the time usual with the ordinary system. The cool cylinder lessens the liability of PREIGNITION and decreases the consumption of cooling water and lubricating oil. Auxiliary exhaust ports are particularly desirable on air cooled engines. GAS, OIL AND STEAM ENGINES 321 (141) Valves and Compression Leaks Misfiring. Owing to the intense* heat in the cylinder, and the action of the gases on the valves the seating surfaces become ROUGH and PITTED which causes leakage and loss of compression. Exhaust valves cause the most trouble in this respect as they are surrounded by the hot gases during the exhaust stroke and are much hotter than the inlet valves. To determine the value of the compression, turn the engine over slowly by hand. Leaking inlet valves usually are productive of BACK FIR- ING or EXPLOSIONS IN THE CARBURETOR intake pas- sages, or in the mixing valves, as flame from the cylinder leaks through the valve and fires the fresh gas in the intake. MISFIRING OR LOUD EXPLOSIONS at the end of the EXHAUST PIPE are indicative of leaky exhaust valves, if the mixture is correct and the ignition system above suspicion. Misfiring caused by leaky exhaust valves is due to combustible mixture escaping from the cylinder to the exhaust pipe and being ignited by the succeeding exhaust of the engine. If the engine has more than one cylinder, test one cylinder at a time, opening the relief valves on the other cylinders. Now take a wrench and ROTATE the inlet valve on its seat, for it may be that some particles of carbon or dirt have been deposited on surface of the valve seat which prevents the valve from closing properly. Rotating the valve will usually dislodge the deposit. Try the compression again; if there is no improvement, rotate the exhaust valve on its seat in the same manner, and repeat the test for compression. ROTATING THE VALVES IN THIS MANNER WILL OFTEN MAKE THE REMOVAL OF THE VALVES UNNECESSARY. When the valves are closed the end of the valve stem should NOT be in contact with the PUSH ROD, or cam lever. Suitable CLEARANCE should be allowed between the end of the valve stem and the operat- ing mechanism when the valve is closed; this clearance varies from the thickness of a visiting card on small engines to % of an inch on the large. If the valve stem is continually in con- tact with the push rod it cannot seat properly and consequently will leak. Wear on the valve seats and regrinding reduces this clearance, wear on the ends of valve stems and push rods from continuous thumping increases it. Keep the clearance constant and equal to that when the engine was new. On many engines 322 GAS, OIL AND STEAM ENGINES this clearance is adjustable to allow for wear by lock nuts on the ends of the valve stems or push rods. If the above attempts have proved unsuccessful remove the exhaust valve from the cylinder, if the valve is in a cage, remove the entire cage; this may easily be done on most types of en-' gines. Always remove the exhaust valve first as the inlet valve rarely requires attention. With small engines, and engines having the valves mounted directly in the cylinder head it will be necessary to remove the cylinder head to gain access to the valves. In such a case use care when opening the packed joint between the cylinder and head, to avoid damaging the gasket. The exhaust valves should be lubricated with Gas Engine Cyl- inder Oil, never with common machine oil on account of gum- ming and sticking, or with gas engine cylinder oil thickened with FLAKE GRAPHITE. Powdered graphite may be used with success without the addition of oil, but oil makes the application of the graphite much easier. A cracked valve seat, due to expansion strains or to the hammering of the valve, is a common cause of compression leakage, and is rather difficult to locate as the leakage only occurs under comparatively high pressure. Leakage may also occur between the valve cage and the cylinder casting unless pains are taken to thoroughly clean the cage and the bore be- fore fastening into place. Warped valves are caused by overheating, the head of pallet of the valve becoming out of square with the stem, or by twist- ing on the valve seat. If warped valves are suspected the high point of the seat may be determined by means of the following test and should be carefully filed down until it is close to a bearing after which it may be ground down as described under pitted valves. If the stems are now in good condition examine the seating surfaces of the valve pallets and cage or rings. The seats should be bright and free from pits, depressions, or streaky blue discolorations. If the seats are deeply grooved from long continued leaks it is best to discard them and replace with new. Pitted valves, and those slightly grooved or streaked should be reground by the use of a little emery flour and tripoli which operation is performed as follows: Lift the valve from its seat and apply lubricating oil to the seating surface, then sprinkle a little flour or emery on the oiled GAS, OIL AND STEAM ENGINES 323 surface and drop the valve back on the seat. Do not use coarse emery nor too much of the abrasive, a pinch is enough and will grind as rapidly as a pound. Take care to drop the emery only where required, do not sprinkle it over the engine or working parts as it will cause cutting and the destruction of the bearings. Now turn the valve around in 'one direction for about a half dozen turns and then in the other direction for the same length of time, alternately, at the same time applying a moderate pres- sure on the valve. Small valves may be rotated with a large screw driver entered in the slot found on the valve plate, but the handiest method is with a carpenter's brace in which is in- serted a screw-driver bit. Never turn the valve around and around in one direction continuously as this movement is liable to cause grooving, alter- nate the direction of rotation frequently with occasional back and forth movements made in a semi-circle. Do not press heavily on the valve, use only enough pressure to insure contact between the two seating surfaces. The valve should be lifted occasionally from the seat to pre- vent grooving, and to redistribute the abrasive, and then dropped back, after which the grinding should proceed as before. Re- move the valve after it turns without friction, wipe it clean, apply fresh oil and emery and grind once more. When the grinding has removed all pits and ridges, and presents a smooth even surface, the grinding is complete. To test for accuracy of grinding place a little Prussian Blue on the seat, if the valve is ground to a perfect surface the blue will show uniformly spread over the seat, if the grinding is incomplete bare places showing high spots will be seen. It is a good plan to finish the grinding by using a little Tripoli with oil after the emery has removed the pits and high spots, as Tripoli is finer than emery and will smooth down scratches made by the emery. After the grinding has been performed to your satisfaction, wash the valve, valve stem, and guides thoroughly with gaso- line and kerosene to remove the smaller traces of emery, to prevent wear and cutting. When the valves are ground in place on the engine stuff up all openings or parts of the cylinder to prevent the emery from gaining access to the bore. After grinding is complete wipe off surfaces thoroughly and remove waste used for stuffing. CHAPTER XHI GAS ENGINE GLOSSARY Report of the Nomenclature Division of the Data Com- mittee of the National Gas Engine Association Accelerator. A type of throttle control. Usually a foot throttle on an automobile. Accessory. A subsidiary part of an engine, such as the parts required for ignition, carburetion, lubrication and starting. Advance. Spark. The distance usually measured in degrees of arc, that the spark occurs in advance of the dead center. Air-cooled motor. See engine air-cooled. Air starter. A device for starting an engine with com- pressed air. Ammeter (Ampere-meter). An instrument for measuring the amount of electric current flowing in a conductor. Assembly. The act of combining the various parts of the machine into a finished whole. A, drawing. The general draw- ing of the machine as a whole. Assembler. A mechanic who has charge of the assembling of a machine. Automatic valve (Also called suction valve). An inlet valve held to its seat by a light spring and opened by atmospheric pressure due to the suction of the piston; in a carbureter a valve opened by the vacuum in the carbureter. Auxiliary port. In a four-cycle engine, an exhaust port, uncovered by the piston at the end of the stroke; in a two- cycle engine, an intake port leading to the crankcase. Axis. A line passing through the center as the center line of a crankshaft or the center line of a cylinder. Back fire. An explosion in the intake passages of an engine. See base explosion. Baffle, baffle plate. An obstruction in the path of a fluid for the purpose of either changing its direction or retarding its velocity. See deflecting plate. 324 GLOSSARY 325 Balance, running. Any part of a machine is in running bal- ance when the arrangement of particles in the rotating part is such that there is no tendency for it to be deflected from its prescribed path by unbalanced centrifugal forces. static b. A part such as a flywheel is in a static balance when, being free to roll, it will remain in any position on a level surface. b weight. A weight either a part of or attached to the crankshaft to counter-balance the effect of the reciprocating parts and the crank pin and the crank arms. b, wheel. Frequently, but erro- neously, used for flywheel. Base. That part of an engine containing the crankshaft. A term usually employed for engines in which the crankshaft is enclosed. Compare frame. Base explosion. An explosion in the crankcase or base. Usually employed in reference to a two-cycle engine. Battery, electric. A combination of two or more electric cells. Bed, engine. See frame. Benzene. A liquid hydro-carbon, with a formula (C 6 H 6 ). Formerly derived exclusively from coal tar, but now obtainable from petroleum. Compare benzine. b, group. Hydrocarbons of the formula (C2H 2 n 6 ). Benzine. A distillate of petroleum between gasoline and the petroleum ethers. Benzol. Crude benzene. Chiefly a mixture of benzene and its homologues. Benzoline. Benzene. Blast furnace gas. See Gas. Bore, of cylinders. Inside diameter. Boss. A projection, usually cylindrical, of a machine part. Box. See bearing. Strictly speaking, box is the frame con- taining the anti-friction part of a bearing. Sometimes called bearing shell. b, coil. A spark coil, usually of the high tension type, enclosed in a wooden box. b, piston. A hollow piston closed at both ends. Brake horsepower. The horsepower delivered by an en- gine or motor at the point of power delivery. So-called because the power is usually determined in a test by means of a prony brake or other form of absorption dynamometer. "Delivered" horsepower is preferred. Brass, or brasses, bearing. The bronze shells of a bear- ing which are in contact with the rotating shaft. They may or may not be faced with babbitt. 326 GLOSSARY Breech. The closed end of a piston or a cylinder. Built-up flywheel. A flywheel comprised of two or more pieces. Bulb, hot. In certain forms of oil engine an unwater-jacketed cup or pocket employed for the purpose of ignition. Butterfly throttle. A thin disk similar to the damper in a stove pipe rotated on a spindle passing at right angles through the axis of the inlet pipe. By-pass. See transfer port. Cable, ignition. An insulated electric conductor, or a com- bination of several insulated conductors. Cam. A rotating part of a machine having a projection designed to give variable motion to another part bearing against it. Camshaft. A shaft carrying one or more cams. Cap bolt, cap screw. A bolt used without a nut to screw into one of the parts which it is used to hold together. Cap stone. A flat stone sometimes employed for the top of a foundation. Carbureter. A device by means of which the air entering a liquid fuel engine is caused to pick up and atomize a small quantity of the liquid fuel. Cell, electric. An electric couple comprised of two dis- similar metals or a metal and a metalloid surrounded by a salt of an acid solution which will produce a difference of potential between the solid elements. The liquid is known as the electrolyte. dry c, An electric cell in which the electro- lyte is contained in some absorbent material. storage c, An electric cell in which electrical energy is transformed into chemical energy and stored until some future time when it may again be obtained in the form of electrical energy. Charge. In a gas engine, that quantity of mixture taken into a cylinder at one suction stroke. Clerk-cycle. A form of two stroke cycle invented by Dugald Clerk and having a separate charging cylinder. Clutch. An engaging device for connecting a driven machine with the driver. Cock, drain. An ordinary pet cock used for letting surplus oil out of the base or water out of the water jacket. relief c, A valve or pet cock connected to the cylinder, usually to the compression space, to relieve the compression. priming c, or cup. A small pet cock of special form with the cup on the outer end which is screwed into the cylinder and is employed for the GLOSSARY 327 purpose of admitting a small quantity of gasoline to the cylinder for starting. Co-efficient of unsteadiness. The allowable variation of the speed from the normal speed of the engine, used in flywheel design. Coil. See spark coil and jump spark coil. Compensating valve. In a carbureter, a valve whose function is to retain the proper proportions of the mixture at all speeds. Compression, compression pressure. The pressure in pounds gage secured by the inward movement of the piston. c, space. .The space in the cylinder back of the piston when the piston is at the end of its inward stroke. c, stroke. The second stroke of the four-stroke cycle in which the charge, already drawn in is compressed before ignition. Connecting rod. A mechanical link connecting the piston to the crankshaft. Consumption, fuel. See fuel consumption. Contact points. In a make-and-break igniter the two small pieces of metal at the point of contact between the insulated and the grounded electrode, and between which the spark is made. Frequently made of a nickel alloy. Cooling tank. A tank of comparatively large capacity con- nected to the water jacket of an engine. Counter balance. See balance weight. Counter bore. An enlargement of the diameter of the cyl- inder in the compression space. Counter weight. See balance weight. Crank case or chamber. See base, c, arm, That part of the crank-shaft connecting the crank pin to the main shaft, c, pin. That part of the crankshaft to which the outer end of the connecting rod is attached. Sometimes but erroneously called wrist pin. c, pit, Practically synonymous with crank case, but usually referred to the lower part of the base. c, shaft, An axle or shaft carrying a cylindrical portion offset from the main shaft and connected thereto by means of arms for transposing the reciprocating motion of the piston into rotating motion. starting c, A bent lever with a handle for turning an engine when starting. c, web, See crank arm. Crosshead. A guiding member, usually employed in a double-acting engine, located at the connection of the piston rod and the connecting rod. Crude oil. Unrefined oil as it comes from the well. The 328 GLOSSARY term is frequently, but erroneously, applied to the residuums of the refinery. Curve, compression. The line on the indicator diagram de- noting the rise of pressure during the compression stroke. expansion c, A curve on the indicator diagram showing the drop of pressure during the expansion stroke. Cup, grease. A device for supplying lubricating grease to a bearing oil, c. A device for supplying oil to a bearing or similar surface. priming c, See priming cock. Cut-off (Valve closure). A term usually applied in a steam engine to the closing point of the admission valve. Sometimes used in the internal combustion engine to indicate the time of closure of the inlet valve. Cycle. The complete series of operations required for the functioning of a heat engine. four c, Properly four-stroke cycle. A cycle requiring four strokes or two revolutions of the engine for its completion as follows: Suction stroke, outward; com- pression, stroke inward; expansion stroke, outward; exhaust stroke inward. six c, Properly six-stroke cycle. A cycle re- quiring six strokes of the engine for its completion. The strokes are as follows: Suction, compression, explosion, ex- haust, suction of a charge of air, or scavenging charge, and ex- pulsion of scavenging charge. two c, Properly two-stroke cycle. A cycle requiring two strokes of the piston for its completion. The suction stroke and the exhaust stroke of the four-cycle are eliminated, the outward stroke is always the expansion stroke. About 1/5 of the expansion stroke is used for exhaust and ap- proximately 1/10 of the same stroke for receipt of a fresh charge from a special source of supply, as the crank case or a charging pump outside of the cylinder. The inward stroke is always the compression stroke. Cylinder. The hollow cylindrical portion of an engine in which the functions of the cycle take place. c, head. The closed end of the cylinder. c, jacket. An annular space about the cylinder containing the cooling medium. c, bore. The inner diameter of the cylinder. c, studs. Studs for holding the cylinder to the base or frame. c, bolts. Bolts to hold the cylin- der to the base or frame. Dead center. The extreme end of the stroke both inward and outward. So-called because the piston comes to a "dead" stop for a small fraction of time before it starts in the opposite direction. Deflecting plate, deflector. In a two-cycle engine a projec- GLOSSARY 329 tion on the piston to direct the incoming charge towards the cylinder head. Delivered horsepower. The horsepower delivered to the driving shaft or to the belt or other driving means exterior to the engine itself. Diagram, indicator. The trace drawn by the pencil or stylus of the indicator. Diameter of cylinder. See bore. Die-cast bearing. Bearing cast in metal dies. Diesel cycle. A high pressure cycle of either the two-cycle or the four-cycle type in which pure air only is compressed, and the fuel is injected, usually by air-, at or near the end of the compression stroke. The term is usually applied to engines de- pending entirely upon the heat of the compression to ignite the fuel without the aid of any other ignition means. Differential piston. A piston having two or more portions of different diameters. Discharge, water. Water outlet. Distillate. A liquid petroleum derivative with a specific gravity between gasoline and kerosene The term is usually applied to a product of Pacific coast petroleum. Distributor. Virtually a commutator for the high tension spark in jump spark ignition. Usually made to operate syn- chronously with the circuit breaker. Double-acting. Applied to either an engine or a pump in which functions of the cycle are performed on both sides of the piston. Drop, in two-cycle ports. The distance measured along the axis of the cylinder between the opening of the exhaust and the opening of the inlet from the transfer port. Dual, ignition. An arrangement whereby a magneto may be used for battery ignition, usually temporarily for starting. Duplex engine. Occasionally applied to a two-cylinder en- gine with the cylinders parallel. Duplex ignition. A system of ignition whereby two spark plugs may be used simultaneously. Dynamometer. A device for measuring the horsepower of an engine or motor. absorption d, A dynamometer in which the power is absorbed in the dynamometer itself. transmission d, One in which the power is measured during its transmission to power driven apparatus. Economy, fuel. The amount of fuel required per horse- power hour. See fuel consumption. 330 GLOSSARY Effective port area. That area which gives the required speed of the gases as computed on the assumption that the valve or port is fully open when open at all. Efficiency. The ratio between actual performance and theo- retical perfection. thermal e, The ratio of the delivered to the indicated horsepower. thermal e, The ratio between the amount of heat transformed into work and the heat value of the fuel required to perform that work. volumetric e, The ratio of the actual volume of the charge, measured at atmospheric pressure, to the piston displacement of the engine. Electric ignition. Any form of ignition depending upon elec- tric current for its functioning. Electrode, of the spark plug. The terminal wire of the plug inside the cylinder through which the spark passes. Generally the terminals of conductors performing any function. movable e, In a make-and-break igniter the rocking contact arm. sta- tionary'e, In a make-and-break* igniter the insulated contact rod. Electric dynamometer. A form of dynamometer of which an electric generator forms the principal part. Electric starter. An electric motor for turning an internal combustion engine to start it. Entropy. A function of heat change. It is the quotient of the heat change divided by the absolute temperature at the instant of change. Engine, air-cooled. An engine with cylinders cooled by di- rect contact with air. Diesel e, Any engine using the Diesel cycle (which see). gas e, An internal combustion engine using gas for fuel. oil e, An internal combustion engine using oil for fuel. hot bulb e, An internal combustion engine using a hot bulb or unjacketed pocket for ignition. internal combustion e, An engine wherein the fuel is entirely consumed inside the working cylinder. two-cycle e, See cycle. four-cycle e, See cycle. portable e, An engine mounted on a wheel truck. semi-Diesel e, A popular term for a hot bulb engine. six-cycle e, See cycle. Exhaust n. Gases discharged from the cylinder, usually the products of combustion. Exhaust, water. Water discharged from the water jacket. e, manifold. That part of the exhaust passages immediately connected to the cylinder. e, pipe. A pipe connected to the exhaust manifold or to the muffler for carrying the exhaust gases to the point of discharge into the atmosphere. e, port. An opening in the cylinder wall for the discharge of the exhaust GLOSSARY 331 gases. e, stroke. The fourth stroke of a four-stroke cycle, during which the exhaust gases are discharged from the cylinder. e, timing. Points measured in circular degrees at which the exhaust valve or exhaust port opens and closes. e, valve. The valve closing the opening into the cylinder through which the exhaust is discharged. Exhaust (verb). The act of discharging material, such as waste gases from the cylinder or water from the water jacket. Expansion. Increase in volume. e, curve. The line on the indicator diagram indicating the pressures in the cylinder in re- lation to the various points in the stroke. e, stroke. The third stroke of a four-stroke cycle during which the gases expand and perform work upon the piston. Explosion. A sudden increase in pressure or volume usually caused by combustion. e, line. The line of the indicator dia- gram showing the increase in pressure after ignition. premature e, An explosion caused by too early ignition during the com- pression stroke. Explosive mixture. A mixture of combustible fuel and air in such proportions that explosion will result on ignition. Flame ignition. Ignition by exposure of the charge to a naked flame. f, propagation. The advance of combustion throughout the charge following ignition. Float. A part of the carbureter lighter than the fuel and employed to regulate the height of fuel in the nozzle. f, chamber. That part of the carbureter containing the float. Flooding. Excess of liquid fuel in the intake passages or in the cylinder. Flywheel. A heavy wheel attached to the crankshaft of the engine to prevent excessive fluctuation in speed. Foundation. A mass of concrete, stone, brick or other ma- terial on which the engine is mounted. Four-cycle. See cycle. Four-port motor. A two-cycle motor using crankcase com- pression, provided with both a suction valve and a piston con- trolled crankcase port. Forward stroke. See stroke, outward. Frame. That part of the engine attached to the foundation and carrying the crankshaft bearings, etc. sub f, In engines of large size the frame is made in two parts, the frame proper, carrying the crankshaft bearings, and the sub frame being un- derneath the frame proper between it and the foundation. Fuel consumption. The amount of fuel required per horse- 332 GLOSSARY power hour to operate an engine, usually measured in pounds for liquid fuel and cubic feet for gaseous fuels. Gap, spark. In jump-spark ignition the distance between the points of the spark plug or between any two separate parts of the high tension circuit; a device usually mounted exterior to the engine containing an opening in the high tension circuit. Gas. Aeriform elastic fluid. For example, air, oxygen, hy- drogen, etc., are all gases. air g, Term generally used for air charged with gasoline vapor. artificial g, Any manufactured gas, usually confined to gas manufactured by the distillation of coal for domestic use. Blast furnace g, Gas made in the blast furnace during the reduction of iron ore. coal g, Gas made by the distillation of coal. illuminating g, Gas manufactured for illuminating purposes. oil g, Gas made from oil. producer g, Gas manufactured by the incomplete combustion of either a solid or a liquid fuel, principally carbon monoxide. water g, Gas usually manufactured from coal by the partial combustion of the fuel combined with the disassociation of water. Gas engine. An internal combustion engine, strictly, one using gas as fuel. Gasoline. Usually a fuel with a distillation range of 100 to 400 F. Gasoline engine. An internal combustion engine using gaso- line as a fuel. Gas producer. A device for the manufacture of producer gas. Gas tractor. A farm or road locomotive powered with an internal combustion engine. Governor. Any device for regulating the speed of an engine so as to maintain it between certain limits. centrifugal g, A governor depending uf>on the change in centrifugal force due to change of speed. electric g, A governor regulating by the change in voltage of a generator. Hit-or-miss g, A method of governing by omitting, entirely, one or more explosions. throt- tling g, A method of governing by choking the inlet passages. g, valve A valve for controlling the amount of mixture passing through the inlet passages. Head, cylinder. See cylinder head. h, end. The end of an engine opposite that carrying the crankshaft, piston h, the piston proper in a double-acting engine, valve in h, engine. An engine having the valve in the cylinder head. Heat, analysis. A test to determine the distribution of heat in the operation of a heat engine. h, balance. The result ob'- GLOSSARY 333 tained by heat analysis. h, of combustion. The heat given off when burning a unit quantity of fuel. The unit generally being one pound. h, engine. Any prime mover deriving its power from the expenditure of heat. h, unit. A measure of heat. English unit, the amount of heat required to raise a pound of water 16 Fahrenheit; known as the British Thermal Unit or B. T. U. Metric unit, the amount of heat required to raise a grain of water 1 centigrade; known as a calorie. h, value, high. The heat of combustion of a fuel including the latent heat of steam for the hydrogen content. h, value, low. The heat of combustion less the latent heat of steam for the hydrogen content. High-tension ignition. See ignition, high tension. Hit-or-miss governor. See governor, hit-or-miss. Hopper. A form of water jacket enlarged or extended at the top to form a reservoir. , cooled. An engine having an open jacket. Horizontal engine. One in which the axis of the cylinder is normally parallel to the earth's surface. Horsepower, (Note this word should be written without a hyphen). The expenditure of 3,300 foot pounds in one minute. brake, h.p. The power derived by a brake test. delivered h.p., The power delivered to the belt or other means of transmission. draw bar h.p., The power based on the pull at the drawbar of a locomotive or tractor. electric h.p., 745.941 watts. indi- cated h.p., The horsepower based on the mean effective pressure as shown on the indicator diagram. metric h.p., 4,500 kilo- gram-meters per minute. h.p., nominal. The rated or catalog horsepower of an engine. h.p., of water. Indian government standard, 15 cubic feet falling 1 ft. in one second. Hot bulb engine. An engine in which the charge is ignited with a hot bulb. Hot bulb ignition. See ignition, hot bulb. Hot plate ignition. See ignition, hot plate. Hot tube ignition. See ignition, hot tube. Housing. A term of varying significance frequently em- ployed to denote the frame or crankcase of an engine. Hydrocarbon. A substance formed chiefly of hydrogen and carbon in chemical combination. Ignite. To set fire to. Igniter. A device which ignites. Ignition. The act of igniting. battery i, Electrical ignition having as its primary source of electrical pressure, an electric 334 GLOSSARY battery. catalytic i, Contact ignition, said of ignition pro- duced by the rise of temperature caused by . the gas or mixture coming , in contact with some material like spongy platinum. flame i, See flame ignition. high frequency i, Elec- tric ignition by means of a high frequency alternating current. Usually that form of current produced by a condenser discharge. high tension i, Ignition caused by a current of sufficiently high voltage to make the spark leap an open gap jump spark i. hot bulb i, Ignition by means of an unwater-cooled pocket in the engine cylinder. hot plate i, Ignition by means of an unwater-cooled plate attached either to the inside of the cylinder hear or to the end of the piston and heated by the combustion of the cylinder. hot tube i, Ignition by means of a tube heated by a flame exterior to the tube. jump spark i, See high tension ignition. magneto i, Electrical ignition hav- ing as its primary source of electrical pressure, a magneto. premature i, Ignition taking place before the proper time in the cycle. -i, system. The method and apparatus used in any form of ignition. Illuminating Gas. See gas, illuminating. Indicated horsepower. See horsepower, indicated. Indicator. An instrument for registering the pressures at different points in the cycle. i, card. A sheet of paper on which the indicator diagram is recorded. i, diagram. The trace of the indicator pencil or stylus on the indicator card. gas engine i, A special form of indicator, usually with a Y$ in. area piston for indicating a gas engine. Inertia governor. A governor utilizing the properties of inertia for the regulation of an engine. Usually employed in a hit-or-miss governor only. Inflammation, period of. The time elapsing between the instant of ignition, and the instant at which the ^ntire charge has been ignited. Inlet manifold. That part of the engine containing the passages from the carbureter to the cylinder. i, port. The open- ing in the cylinder wall through which the charge is drawn in. i, stroke. The first stroke in a four-stroke cycle during which the charge is drawn into the cylinder. i, valve. The valve con- trolling the opening from the inlet manifold to the cylinder. Intake. Synonymous with inlet. Internal combustion engine. See engine, internal-combus- tion. GLOSSARY 335 Inward stroke. The stroke during which the piston is ap- proaching the cylinder head. Isothermal. Without change of temperature! Isopiestic. Without change of pressure. Jacket. In a gas engine, a hollow space surrounding some portion of the engine, such as the water jacket around the cyl- inder. water j. A jacket containing water, as the water jacket around the cylinder heater j. A jacket surrounding the inlet passages for the reception of either hot water or hot exhaust gas, or a jacket connected with the inlet passages and surround- ing the exhaust pipe. manifold j. A jacket surrounding either the intake or the exhaust manifold. Journal. See bearing. Junk Ring. A ring, usually forming a part of the piston, separating the piston rings, derived from the ring used to clamp the hemp or similar packing (junk) .used in the early steam engines. Jump-spark ignition. See high-tension ignition. Kerosene. A product of the fractional distillation of petro- leum having a gravity of 40 to 46 Baume and with other characteristics usually fixed by State or National Law. Lamp oil. Lag of magnet. The time required for an electro-magnet to reach its full strength after closing the circuit, magnetic inertia. Lag of spark. The time elapsing between the operation of the timing device and the production of the spark. Lag of valve. The distance measured in the direction of the piston travel or in degrees on the crank circle that a valve remains open after the piston has passed the dead center. Latent heat, of steam. The amount of heat required to trans- form water from a liquid form into steam at boiling temperature; of melting ice, the heat required to transform ice into water at the melting temperature. Lay shaft (obsolete). See cam shaft. Lead, of valves. The time measured along the travel of the piston or in degrees on the crank circle that the valve opens in advance of the dead center. Lean mixture. A mixture of fuel and air in which there is much more air than required for complete combustion. Lift of valves. The amount, measured in the direction of travel, that a valve is raised from its seat. Locomotive, gasoline. A locomotive which is driven by a gasoline engine through gearing. gasoline-electric 1. A loco- 336 GLOSSARY motive driven by a gasoline engine through an electrical trans- mission. Load, brake. The load on the end of the arm of a prony brake. Occasionally used to denote brake horsepower. Low-tension ignition. Ignition produced by breaking a cir- cuit of low voltage. Load, rated. See horsepower, nominal. Low-tension magneto. A magneto designed for low ten- sion ignition delivering current at about eight volts. Lubricant. Anything which lubricates. Lubricate. To reduce friction by means of an oil, grease or equal material. Otherwise to apply a lubricant. Lubrication. The act of lubricating. Magnetic igniter. A low-tension igniter in which the circuit is broken by an electro-magnet. Magneto. An electric generator having permanent mag- nets for the field. high tension, low tension, dual, duplex, inde- pendent m. See ignition. Main bearing. See bearing, main. Make-and-break igniter. A low-tension igniter in which the igniter points are brought together and separated mechanically in the combustion space, (hammer-break igniter.) Sometimes used, instead of make-and-break igniter. The term is, however, not sufficiently inclusive. Maker, contact In an ignition apparatus a device for closing the circuit mechanically at the moment of ignition. Manifold. See inlet manifold, exhaust manifold. Manograph. A form of gas-engine indicator in which the diagram is produced by means of a ray of light reflected from a mirror attached to a diaphragm, the latter being acted upon by the pressure within the cylinder. Marine-type connecting rod. A type of connecting-rod in which the bearings are held in place by a bolted cap. Marine engine. An engine designed to propel a boat or a ship. Master vibrator. In a group of jump-spark coils a vibrator which functions each of the coils in turn. Mean effective pressure (M.E.P.). The average net pres- sure developed during a cycle, as shown by the indicator dia- gram. Mechanical efficiency (M.E.). The ratio of the brake or de- livered horsepower to the indicated horsepower. GLOSSARY 337 Mixer. A term frequently employed to designate a simple form of carbureting device or mixing valve. See mixing valve. Mixing valve. A check valve form of carbureting device in which the lift of the check valve opens the passage into the gasoline supply. Mica plug. A spark plug in which the insulation is made of mica. Misfire. Failure to explode. Mixture. The combination of fuel and air drawn into the cylinder during the suction stroke. Compare charge. Motor. See engine. (Note engine is rapidly gaining in favor among engineers in general.) Motor, automobile. An engine designed to drive an automo- bile. Airplane m, An engine designed to drive an airplane. Diesel m. See engine Diesel. marine m. See marine engine. semi-Diesel m. A term employed for the hot bulb engine, but now gradually increasing in disfavor. super-Diesel m. A term employed by some manufacturers to designate a motor employ- ing the Brons cycle. Motor car. An automobile. Motor Boat. A boat driven by an internal combustion engine. Motor fire apparatus. A fire engine or other apparatus propelled by a gasoline engine. Muffler. A device for quieting the sound of the exhaust. Multi-cylinder (adjective). Having two or more cylinders. Mushroom valve. A poppet valve. Naptha. A hydrocarbon of rather uncertain constitution. The term is frequently employed as a synonym to gasoline. Scientifically a term applied to the lighter shale oils with a specific gravity of about .765. Napthalene. A solid hydrocarbon having the formula (C 10 H 8 ). Napthene. A group of hydrocarbons having the general formula (CnH 2 n). Napthol. An alcohol with the chemical formula (C 10 H 7 OH.) Natural gas. Gas obtained from underground. Needle valve. A sharply pointed valve in a carbureter whose function is to regulate the admission of fuel into the air stream. Nozzle. The end of the stand-pipe in a carbureter through which the liquid fuel is admitted to the air stream. Oil (as a fuel). A term usually applied to any combustible liquid having a dry point above 400 F. The term applies not 338 GLOSSARY only to petroleum products but to combustible liquids of other derivation. Oil. A term usually applied to a large variety of liquids of a more or less unctuous nature and insoluble in water. Oil groove. A groove in a bearing for the guidance of lubricating oil. Oil Ring. A ring resting on the top of a horizontal shaft in a bearing and dipping into the oil in an oil pocket. The rota- tion of the shaft rotates the ring by friction and helps it to drag the oil to the top of the shaft. Oiler. See lubricator. Oil, lubricating. Any oil used for lubrication. Oil engine or motor. An internal combustion engine em- ploying any of the fuel oils. Otto cycle. The usual four stroke cycle. Generally con- sidered to have been originated by Beau de Rochas, but ac- tually put into operation by Doctor N. A. Otto in 1876. Outlet See exhaust. Outlet manifold. See exhaust manifold. Packing ring. See ring piston. Paraffin oil. An English term for kerosene. Paraffin wax. One of the lower hydrocarbons, usually of the Methane group and solid at ordinary temperatures. It is usu- ally white or bluish white, and devoid of either taste or smell. It contains various hydrocarbons, and it has about 15 per cent of hydrogen and 85 per cent carbon. Passage, inlet An opening leading from the carbureter to the inlet valve. exhaust p. The passage leading from the ex- haust valve to the exhaust pipe and usually considered as the exhaust passage in the exhaust manifold. Pendulum governor. A form of governor employed on a hit-or-miss engine, depending for its regulation upon the inertia of a pendulum. Period of inflammation. See inflammation, period of. Petroleum. A natural oily liquid obtained from underground, mineral oil. Pin. See crank pin, piston pin. Pipe, exhaust. Pipe for carrying off the exhaust gases. inlet p. Usually the inlet manifold or a pipe connected to the inlet manifold. water p. A pipe for carrying water to or from the water jacket of an engine. Piston. A sliding cylindrical part fitting into the cylinder of an engine and through which power is transferred through GLOSSARY 339 the connecting rod to the crankshaft. differential p. See dif- ferential piston. p, head. See head, piston. p, valve. A valve in piston form regulating the intake or the exhaust or both by covering and uncovering ports in the walls of a cylindrical valve chamber. p, pin. A cylindrical journal for connecting the piston to the end of the connecting rod. trunk p. A piston closed at one end only. p, rod. A cylindrical rod for connect- ing the piston to the crosshead. p, speed. Twice the stroke in feet multiplied by the r.p.m. Pit, exhaust. A form of large muffler hollowed out of the ground. Plate, handhole. A plate or cover for closing a handhole. Plug, spark. See spark plug. Plunger, pump. - The pump piston. Poppet valve. A disk or head attached to a cylindrical stem of comparatively small diameter for closing an opening by forc- ing it tight against a seat adapted to fit the disk-shaped head. Port. An opening for the admission or the discharge of fluid. p, area. The area of a cross section of a port. exhaust p. See exhaust port. inlet p. See inlet port. Power. See horsepower. Pre-ignition. See ignition, premature. Premature explosion. Explosion caused by premature igni- tion. Primary coil. An induction coil with a single winding, usually employed in primary or low-tension ignition. Primer. A device for inserting a combustible, as gasoline, into a cylinder. Priming cup. See primer. Projected area, of bearings. The length of the bearing multi- plied by the diameter. Puppet valve. See poppet valve. Push rod. In a valve mechanism, a block, usually of cylin- drical form, intermediate between the cam and the valve or the valve operating mechanism. Push rod, roller type. A push rod containing a roller bearing against the cam. Push rod, mushroom type. A push rod having an enlarged end bearing against the cam. Radiator. As applied to an engine, a device of cellular or tubular structure for cooling the jacket water. Range, spark. The angular distance from full retard to full advance in a timer. Rated horsepower. See horsepower, nominal, 340 GLOSSARY Reciprocating parts. Parts such as the piston, piston rod, crosshead and connecting rod, that move back and forth, usually in the direction of the axis of the cylinder. Reverse gear. A device, usually applied to marine engines, by means of which the propeller shaft is caused to run in the direction opposite to that of the engine crankshaft. Reversible engine. An engine which may be reversed in di- rection independently of a reverse gear. Ring, piston. A ring of metal, usually cast iron, cut through in one or more places and so constructed that its periphery is forced into contact with the cylinder walls. Rod, connecting. See connecting rod. Rod, piston. See piston rod. Roller push rod. See push rod, roller type. Scavenging. The act of clearing the cylinder of the residual burned gas or that gas remaining after the completion of the ordinary exhaust stroke. Scavenging is secured either by driv- ing air through the combustion space or by mechanical means, such as a special piston. Shaft, crank. See crankshaft. Single acting engine. An engine in which the impulse is given at one end of the piston only, Spark plug. A device for providing the spark gap in the cylinder for jump spark ignition. Speed, piston. See piston speed. Starter. A device for setting the engine in motion so it will take up its cycle. See air, electric starter, etc. Stationary engine. An engine for driving fixed machinery. Stroke, of piston. The complete movement of the piston in the direction of the axis of the cylinder. inward s. The move- ment of the piston toward the head of the cylinder, and away from the crankshaft. outward s. The movement of the piston toward the crankshaft. Suction gas. Producer gas secured by the suction of the en- gine drawing air through a bed of incandescent fuel. Suction-gas engine. An engine operating on suction gas. s, valve. See automatic valve. Tandem engine. An engine having two pistons on the same axis and connected by a piston rod. Thermal efficiency. See efficiency, thermal. Thermal unit. See heat unit. Thermal unit, Britsh. See heat unit. Thermo-siphon circulation. Circulation of the cooling water caused by the heat in the water jacket. GLOSSARY 341 Three-port motor. A form of two-cycle motor in which the passage to the crankcase is through a piston-controlled port. Throttle. A valve for choking the intake passage between the carbureter and the inlet valve. Timer. A rotating switch for closing the ignition circuit at the proper time in the cycle. Two-cycle engine. An engine employing the two-stroke cycle. Tractor. See gas tractor. Transfer port. The passage from the base to cylinder of a two-cycle engine. Trunk, piston. See piston, trunk. Twin engine. Same as duplex engine. Valve. A device for closing an opening in any part of the engine. See definitions under various heads, as automatic, ex- haust, flat, inlet, etc. Vaporizer. A term of uncertain significance sometimes ap- plied to a carbureter and sometimes to a mixing valve. Seldom used. Vertical engine. One in which the axis of the cylinder is normally vertical. Vibrator. The magnetic circuit breaker of a jump spark coil. Volumetric efficiency. See efficiency, volumetric. Water carbureter. A simple carbureter for supplying water to the intake of a kerosene engine. a, gas. See gas, water. jacket w. See jacket, water. Wrist pin. The piston pin. The crank pin is sometimes, but erroneously, termed the wrist pin. 24165 886775 7 library UNIVERSITY OF CALIFORNIA LIBRARY