The practical gas engineer; a manual of practical gas and gasoline knowledge

Front matter

TJ

755 Lit s practical

Gas Engineer t?cn*>r*'ttrcis I flass T^ W55 Book \- T_j_ Copyright N°

Preface

Having many times in the past ten years felt the need of some book that could be placed into the hands of the busy gas and gasoline engineer for the purpose of aiding him quickly to overcome the apparently mysterious troubles that often arise with these engines, the author has for a number of years, during his extensive travels as an expert for one of the oldest and leading gas engine concerns in America, collected such data in reference to CONSTRUCTION, EQUIPMENT and GAS ENGINE TROUBLES as are of special interest to the PROSPECTIVE PURCHASER, the GAS ENGINEER, or any one wishing to post himself thoroughly on the management, care, operation and selection of a gas or gasoline engine.

The data thus gathered and compiled in this book cover practically all the questions that arise from the purchaser's, owner's and engineer's standpoint.

4 PREFACE.

It is the author's intention that it shall be a ready reference most valuable to all persons interested in modern gas and gasoline engines, and especially to the busy gas engineer, in cases of emergency where his engine refuses to operate successfully and the cause of the trouble is difficult to locate.

In handling the various subjects the author has endeavored to studiously avoid the theoretical, and adhere strictly, in as brief a manner as possible, to the practical questions concerning the purchase and handling of gas and gasoline engines.

I have reason to believe that this book will save many a gas engine owner, not only much time and money that without it would be expended on repairs, but that it will also save him much mental worry and make him and his gas or gasoline engine closer friends.

If it does either it will have attained its purpose.

THE AUTHOR.

ERRATA

Page I 5, paragraph 42 should read: I -1200 to 1-300 in., etc.

Part I. Introductory

1. A GAS ENGINE may be defined as a Motor or Prime Mover which derives its power from the Combustion, within its cylinder, of a mixture of gas and air in the proper proportion to form an explosive.

2. The COMBUSTION or burning of this charge of gas and air is occasioned under a close or heavy compression, a result of the inward movement of the piston after the charge is admitted and all valves closed. The result of igniting this mixture under the heavy compression is what is commonly called an explosion, which is nothing more than a quick burning or rapid combustion of the mixture.

3. This explosion causes suddenly a high degree of heat within the cylinder, behind the piston, which heat results in a great EXPANSIVE FORCE, creating an initial pressure against the piston of something near 200 pounds to the square inch. This drives the piston rapidly and forcibly on its outward movement, which, connected to the fly wheels by means of

THE PRACTICAL GAS ENGINEER.

pitman and crank shaft, imparts to them their revolving motion and consequent power= 4 FUEL — A number of combustible products are well adapted to be used as fuel in a gas engine.

5. The most commonly employed are Natural and Artificial Gas, Gasoline, Benzine, Distillate, etc.

6. These products are known as Hydro-Carbons, and may be considered products of Coal, Wood, Water and Crude Mineral Oil.

7. This style of motor is commonly called Gas Engine. Gasoline Engine, Hydro-Carbon Engine, Naphtha Engine, Kerosene Engine and Explosive Engine. It is entirely proper to call an engine that employs gasoline for fuel a Gas engine. A Gasoline engine is practically a Gas engine. All Hydro- Carbon engines are Gas engines.

8. Gasoline atomized or vaporized with the current of air as it enters the cylinder simply forms a gas, and is transformed as such into power. It is gasoline only on the outside, but gas on the inside of the cylinder. So with all the other fluids named. Therefore all the liquid fuels employed in these engines must be by some method first transformed into gas before they are useful.

9. BIRTH OF THE GAS ENGINE — As early as 1680 Huyghens suggested the use of gunpowder in an explosive engine. This suggestion engaged the attention of other minds.

10. M. Beau de Rochas advocated a Four- Cycle idea in 1862. But the reai practical demonstration which proved that the gas engine could be made a success was made by Lenoir in I860, and Hugon, Siemens, Boulton, Crosley and Dr. Otto a few years later designed engines that proved the gas engine a success beyond a doubt.

11. FOUR CYCLE and OTTO CYCLE are used synonymously, meaning that an engine completes a Cycle in Four (4) acts, or that it requires four (4) movements of the piston to complete a Cycle, as follows :

1st — On the outward movement of the piston a charge of gas and air is drawn into the cylinder. In other words, inhaled.

2nd — On the inward movement, the valves being closed, the charge is compressed in the rear end of the cylinder.

3rd — At the beginning of the working stroke Explosion and Expansion of the charge under the heaviest compression pressure causes the next outward movement.

4th — The second inward movement, with the exhaust valve open, exhausts the burnt gases.

12. Therefore two revolutions of the fly wheels are necessary to complete one cycle, consisting of an Inhalation, Compression, Expansion and Exhaust.

13. All Gas Engines are not built on the Four-Cycle plan. There are many Two-Cycle engines now on the market. But the Four- Cycle engine up to the present has been a great favorite over the Two-Cycle with both the manufacturer and user.

14. This is so partly because there are fewer obstructions to be overcome in manufacturing a successful four-cycle, in consequence of which the manufacturers have given more attention to perfecting and simplifying that cycle, and inasmuch as they are meeting the requirements of power users, and are favored with a ready market, they do not care to leave it for the two-cycle problem.

15. A TWO-CYCLE engine, of course, must be differently constructed from a four-cycle. There must be two compression chambers, either in the shape of two cylinders or one cylinder with both ends closed, or the crank chamber may be tightly encased and used as a compression chamber. THE TWO COMPRESSION CHAMBERS are necessary because in a two-cycle engine a charge of gas and air must be received by the engine somewhere at the same time the previous charge is being compressed ready for explosion.

16. As before stated, two cylinders, placed side by side, with their pistons moving in opposite directions at the same time, and with their compression chambers connected with an admission port and \ alve, will cover the requirements of a two-cycle. The more simple arrangement of making one cylinder and piston serve the same purpose is most desirable.

17. To make its operation clear, I will take for an illustration the single cylinder two-cycle engine, using the air-tight crank case or chamber for a receiving, mixing and compression chamber.

18. The casting is so made that when the engine is completed the pitman and crank are completely enclosed and work in this air-tight chamber. You can easily understand that if it were not for the piston this chamber and the cylinder would be one continuous, irregular, enclosed space. The piston , however, working in the cylinder divides the space into two chambers, the cylinder proper and the crank chamber.

19. To the crank chamber there must be an admission port and valve to receive the charges. From the crank chamber to the cylinder there must be a side passage to carry the charge from the crank space into the cylinder. From the cylinder to the outside there must be an exhaust port or valve.

20. NOW NOTICE THE ACTION OP THIS ARRANGEMENT. When the piston moves back into the cylinder it acts as a suction pump to the crank chamber, and if the admission valve were closed it would create a partial vacuum in the crank space. But the admission valve is opened on this inward stroke of the piston and admits a properly mixed charge of gas and air. As the piston moves out toward the crank space it compresses this charge to the end of its stroke, where a valve or port is opened and the compression pressure, in the crank chamber, forces the charge through the side passage, into the cylinder behind the piston. Now when the piston moves on its inward stroke it compresses the charge behind it, and at the same time draws another into the crank chamber.

21. The compressed charge in the cylinder is exploded just as the piston starts again on its outward stroke. The expansive force of the explosion drives the piston with a rapid movement to the end of its outward stroke when the exhaust port is opened, and the burnt gases are let out into the open air. Just after the exhaust port opens and the exploded charge is leaving the cylinder the compressed charge from the crank chamber comes rushing in from the other side.

22. Therefore the exploding cylinder is always receiving a fresh charge at the same time it is exhausting the exploded one. In other words, emptying out the old on one side through the exhaust port and filling up at the same instant on the other side from the crank chamber. 23. A Two-Cycle engine on each inward movement compresses a fresh charge in the cylinder behind the piston and receives another into the crank chamber. It also explodes a charge and receives an impulse at every revolution.

Part II. Construction

24. Parts necessary to the proper construction of a Gas Engine are Cylinder, Base or Bed Plate, Piston and Piston Rings, Connecting Rod or Pitman, Crank Shaft, Fly-wheels and Belt Pulley, Receiving and Exhaust Vavles, Igniting Device and Governor.

25. A cylinder head and water jacket might be included, although the cylinder head in some engines is continuous with the walls of the cylinder, and consequently a part of it. The cooling, for which purpose the water jacket serves, may be done otherwise, as with spinous projections cast into the cylinder wall.

26. CYLINDER.— In writing on construction the Four- Cycle engine only will be considered.

27. A Cylinder is made of gray iron castings, with either one or both ends open. If both ends are open a cylinder head is fitted onto one end so as to close it. The cylinder is usually cast with water jacket, although the water jacket may be cast separate and fit onto the cylinder. Exhaust and receiving valve ports are cast into the head or onto the sides of one end of the cylinder.

28. So far as the success or failure of a valve is concerned, location of its port has very little to do with it so long as it opens into the compression chamber. That location is usually selected where it is believed to be most convenient to operate the movements of the valve.

29. Both end and side port valves are used very successfully. A number of successful engines have their valve ports on the top and bottom of the cylinder.

30. Many small engines have the base and cylinder cast in one piece. Other cylinders have lugs, brackets or rests cast on them, which are fitted to a similar casting' on the base by means of stud bolts and nuts, and are therefore bolted on. 81. On small engines where combined cylinder and castings are used and easily handled there can be no reasonable excuse offered against the plan.

32. It is argued by some builders that in case of a break to either cylinder or bed only one need be supplied to repair the break, but the increased amount of machine work and time spent in detaching the old piece and putting on the new about offsets their argument. In cost of repairs there is very little difference.

33. The metal in the walls of the cylinder should be of uniform thickness in its entire circumference and from one end to the other, so as to allow equal expansion and contraction throughout.

34. The bore of the cylinder should be as nearly perfect as machinery, handled by a careful and skilled mechanic, can make it. The igniting end of the interior of the cylinder should be smooth and free from projections or sharp corners. The valve ports should be of ample capacity to allow easy admission and free exhaust. Cylinder walls should be from f inch thickness in a 5 -inch cylinder to £ or 1 inch in a 12-inch cylinder. The metal in the walls should be free from sand holes, so as to prevent water leaking into the cylinder.

35. The base or bedplate, as its name implies, is the support of all the working parts of the engine, and should be so designed as to be sufficiently strong at all points where a special strain is liable to be exerted. The base is the support for the cylinder and fly wheels, and should be so arranged as to carry these in the most simple, convenient, efficient and compact manner.

36. In small engines it is desirable to have the base of sufficient height to clear the fly wheels, so that when the engine is placed on the floor the fly wheels may turn clear by an inch or two.

37. In larger engines, where it is desirable to keep down the weight, for convenience in handling, a sub-base may be substituted,

38. The least carelessness in the construction of the crank or journal boxes determines a partial or complete failure of the engine.

39. The edges, or rather the inner edges of the boxes should be so dressed as to just admit the crank without practically any end play, and in a position to bring the center of the crank pin exactly in line with the center of the cylinder.

40. The brass or babbit bearing should be so put in as to insure the center of the CRANK PIN in its entire stroke to be in exact LINE with the center of the cylinder. In other words, the boxes must hold the crank shaft at perfect right angles to the cylinder centers.

41. The brass or babbit bearings should always be strictly of the best material obtainable for the purpose. The least variation from perfect alignment is faulty construction.

42. THE PISTON should be from 1-200 in. to 1-32 in. smaller in diameter than the cylinder, according to diameter of the cylinder. It should be a close gray iron casting, free from sand holes. It should be of the drum-shaped variety, closed at one end and open at the other to receive the crosshead end of the pitman or connecting rod.

43. The crosshead lugs which carry the pin to which the pitman is connected should be located near the center of the piston length. If anything, a little nearer the open than the closed end. It is bad practice to carry the weight necessary to construct a proper crosshead with the weight of the pin and part of the pitman too near the rear end of the piston.

44. There is no rule governing the length and weight of a piston. Each manufacturer constructs a piston of length and weight after his own ideas. The tendency is to make them extremely ]ong, which neccessarily makes them too heavy to be of the best service.

45. The longer and heavier a piston the more friction in the cylinder, and consequently the more power is required to move it, and the more work will be thrown on the crank boxes and shaft in reversing it, whichimparts an end motion to the entire engine that is difficult to balance.

46. I favor a piston of medium length, not too long nor extremely short. An upright engine admits of a shorter piston than a horizontal, because a horizontal engine carries the weight of its piston on the cylinder walls; and the longer the piston the less damaging is the wear to the cylinder. The weight is distributed over more surface.

47. An upright engine carries its piston weight principally on the crank shaft, and therefore should be as light and short as the force with which it has to deal will allow.

48. The Rings on the Piston serve to prevent the escape of the expansive force past the piston, which is necessarily somewhat smaller, so as to allow its free and easy movement in the cylinder.

4P. The packing rings are made larger than the cylinder. A piece from £ to 1 inch in length is cut out, so that when the end of the rings are pressed together it reduces the diameter of the ring to that of the cylinder, but leaves an outward sr^ng to the ring,

60. After cutting a piece out of a perfect ring and pressing the ends together it will make an oblong instead of a perfect ring, and consequently it can not fit a perfect cylinder. After the ring is cut the ends should be pressed together and again turned to a perfect ring, on the outside at least. It is to be regretted that all manufacturers do not follow this rule in making their rings.

51. An oblong ring will wear the walls of the cylidder at two opposite points only, which will soon wear the cylinder oblong in shape.

52. Such rings also fail to serve their purpose by allowing the expansive force to pass the piston. It is as important to a purchaser to know how the packing rings are made as to know that the journal boxes are in exact line from every point with the cylinder.

53. He should always ask an agent or manufacturer who is trying to sell him an engine this question: How are piston rings made? And if they do not make a plain answer, or if they seem to evade the question, it is just as well for the purchaser to give that engine no further consideration. Because if a manufacturer is careless with his cylinder rings and journal boxes he is liable to be careless with every part of his engine.

54. The cylinder rings and journal boxes are not the only safe guides to a purchaser. As we go along with these points on construction you will see that the purchaser will find many things to open his eyes. It is intended to make this little book the purchaser's friend as well as the men who have charge of an engine. If the purchaser were more exacting in his requirements the manufacturer would build him a better engine, and a portion of the gas engine trouble would cease.

55. A purchaser's suspicion may be aroused that a ring is not properly made if there is a coughing noise and smoke coming out of the open end of the cylinder at each explosion of a charge. If by drawing out the piston he finds the rings are bearing and worn ouly at the cut and at a point opposite he can rest assured that the rings were not turned after cutting.

56. PITMAN OR CONNECTING ROD. — Very few gas engine builders use the slides or crosshead guides as used in the steam engines. The pitman is generally connected one end to the crank shaft, the other direct to the piston. It is made of steel casting or steel forging. The latter is less liable to defects, and therefore more desirable.

57. It should be centered, turned and made as light as possible, with ample strength to carry the power transmit-

THE PKacTICAL GAS ENGINEER. 19

ted through it. The center lines of the crossheads and wrist boxes, which are usually made of brass, should be at exact right angles to the center line of the connecting rod.

58. The plan of attaching the wristboxes to the connecting rod, by means of two steel bolts, is probably the most convenient and satisfactory method of attaching these boxes.

59. Owing to the slight motion required at the crosshead many v builders consider a simple bushing amply sufficient, although some are using bearings such as the strap and key variety or one similar to the wrist boxes.

60. . CRANK SHAFT. — The question of crank shaft construction is a very important one. The center line of the wrist pin should be exactly parallel with the center line of the crank shaft. The least variance from this necessarily makes a bad running engine.

61. I have found wrist pins in boxes, that were constantly running hot, not only out of line with their shaft, but also of different diameter at the ends, one end of the pin being considerably larger in diameter than the other. One or the other of the defects here mentioned is usually the cause of a constantly HOT RUNNING wrist box.

62. Improper lining of the crank with the cylinder or the wrist boxes fastened on the pitman out of line are faults that should not be overlooked.

63. The arms of the crank shaft should be of exactly the same thickness, so as to bring the wrist pin in such a position that thb center line of the cylinder will divide it into two exact halves in every part of the entire length of its stroke.

64. LENGTH AND DIAMETER OP WRIST PIN.— The best rule to follow is to make the working area of the crank pin so that there is no more than 400 pounds average pressure to the square inch. Whether you secure this area by a long slim pin or a short thick pin does not matter much, provided extremes are avoided and journal boxes are of suitable length. Builders generally agree that the diameter of the pin should be from 1 to 1£ times that of the shaft.

65. The length of the journal boxes should be not less than 2% times the diameter of the shaft.

66. CRANK SHAFT DIAMETERS.— No uniform rule is followed. But gas engine crank shaft diameters in America compare very favorably with a rule based upon cylinder diameter and maximum pressure within the cylinder. The average diameters run a little "shy" of the rule.

67. WEIGHT AND DIAMETER OP FLY WHEELS.— Very much depends on the speed of the engine as to weight that should be carried. At a medium speed, which may be based on about 225 revolutions for 25 h. p. to 375 for a 2 h. p., one hundred pounds to the horse power will not be very far out of the way. The diameter may range from 28 in. on the small engine to 60 in. on the larger size. The weight above referred to, of course, is divided between the two wheels. 68. BALANCING AN ENGINE.— This is a subject that is not so easily disposed of as it might appear. The majority of manufacturers simply use a weight in the rim of the fly wheels directly opposite the arms and wrist pin on the crank shaft, or, what is practically the same thing, they core out the rim at a point directly opposite from that where the weight should otherwise be.

70. Some builders think the crank shaft is the proper place to attach the balance weights.

71. If carefully done the weight in the rim is equally as good if not a better method than the other, But it is still better to balance the pitman and crank at the rim of the fly wheel, and the piston movement by a sliding counter weight operated from an eccentric on crank shaft.

72. This would necessitate considerable additional mechanism, and therefore is objectionable unless made to serve the purpose of pump, piston or air compressor.

73. A pump or an air compressor in connection with a gas engine is an excellent combination. Unfortunately not every one who has use for a gas engine has need of a pump or compressor. But you can ' 'whack the nail squarely on the head" by making a double cylinder engine with one cylinder on each end of the engine base and a double crank shaft in the center, so that both pistons move away from and towards each other at the same time.

74. This would make a balanced engine without weights and a better power in every w r ay, but more expensive to build and less economical in fuel consumption.

75. VALVES. —The ordinary four-cycle engine usually has three valves, the exhaust valve, the receiving valve and the fuel valve. The exhaust and receiving valves are generally placed at a point on the cylinder head so that their ports lead directly into the igniting or exploding chamber. These valves are usually of the mushroom type, and are operated by means of suitable levers in connection with the cams on a revolving side rod, or by a punch rod from a cog gear driven by the crank shaft.

76. As to the manner of operating these valves, I think the advantages are in favor of the side rod on the engines of the horizontal type and with the gear and punching mechanism on the vertical type of engines.

77. The principal reason for this distinction is that it is more desirable to have the valve stem work in a vertical or upright than in a horizontal position. If a valve stem works in a vertical position the weight of the valve brings it squarely into its seat, and the wear on the seat, value and stem are likely to be uniform at all points. But if the valve is so placed as to move in a horizontal position the weight of the valve pallet has a tendency to wear the stem and seat on their under side only,

%nd therefore liable to soon cause trouble.

78. The valve chambers can be bolted to a horizontal cylinder in a vertical position and operated by suitable levers acted on by cams on the side rod. While on the vertical type of engine the valves are adjusted to the cylinder in a vertical manner directly over the crank shaft or gear, which operates them with a direct acting mechanism.

79. You will notice I say the valve chambers should be bolted or adjusted to the cylinder. They should not be cast on. My advice to any one purchasing is to shun an engine where valve chambers, or at least valve seats, can not be replaced by new ones. Valve seats are liable to wear out and crack by the continual wear and high heat to which they are subjected. The valve pallet and its seat should also be in such a position as to be easy of access. They need to be examined and cleaned occasionally.

80. The exhaust valve on large engines should be watered, otherwise its seat is soon liable to give way under the excessive heat. The cold charges entering at the receiving valve serve as a cooler for it.

81. A valve mechanism may be so designed as to use alternately either gas or gasoline as fuel, but not both a* the same time. A valve or set of valves may be arranged so as to shut off one and turn on the other, thus changing fuels without stopping the engine.

82. The conditions requiring such an immediate change are so rarely met with that I doubt the propriety of fitting an engine with such a complex arrangement. Where a change is really necessary there is always sufficient warning and ample time to prepare for it. The two fuels are of a different chemical composition, and the blending of their elements with a volume of air so as to make a ready explosive would be extremely difficult, and therefore impractical to attempt their combination or use in conjunction or at the same time.

83. To go into the details of describing the various fuel valve mechanisms now used would require more space than could be allowed in this little work. Each builder claims some superior point of merit in his method of feeding the fuel, but it should not be forgotten that other reliable builders mayhave other points as good. It may be sufficient to say that the gas valves, and their operating mechanism, are generally so arranged as to open the valves when the outward movement of the piston is drawing a current of air into the cylinder, and partly by the force of the gas pressure and partly by the suction produced by the piston the gas is admitted to the current of air and mixes with it as it enters the cylinder.

84. Gasoline valves and their methods of handling fuel are a little more complicated, but in most cases it is the current of air, also, by its suction power, that draws sufficient gasoline from a needle point or valve to charge the air current. In some instances the gasoline is forced into the air current by means of a small pump. Some kerosene engines take a charge of air only, and after compressing it, the kerosene is sprayed into the compression space and immediately fired.

85. A purchaser needs to familiarize himself with the function of the gas or gasoline valve on his engine and its method of feeding the fuel. It requires only a little close attention and common sense to ]earn in half an hour all that is necessary to know about the feeding and regulating the fuel to the engine.

86. The fuel may be properly fed and regulated and yet the engine refuse to go. Therefore the fellow who uses common sense enough to learn the proper feeding of gasoline or fuel will get into trouble if he concludes that he has learned it all. This is just the position in which I have found many a fellow. And this brings us to that mechanical part of the engine which probably is more often the source of trouble than all others combined, and that is the IGNITING MECHANISM.