Daimler Engine.— All important gas engine inventors, as Otto and Brayton, modified their engines in order to use liquid fuel. It re mained, however, for Daimler, the pioneer auto mobile engineer and former manager of the Otto Gas Engine Works, to develop the first gasoline engine of the Otto type for automotive work. The main characteristic of the Daimler engine was its high speed. Contemporary gas engines were running at 150 revolutions per minute, while Daimler increased the speed to 800 revolutions per minute. This meant a con siderable reduction in weight at equal power output, yet, on the other hand, a higher strain was set up in the various parts of the engine, necessitating better materials of construction. Thus the Daimler engine incidentally gave also the impetus for the development of high-grade materials without which the present day auto motive engines would be impossible. Daimler's first engine, built in 1884, was of the horizontal one-cylinder type, and differed from the orig inal Otto engine only in speed, weight, fuel and valve gear mechanism. Later he constructed vertical engines of the twin cylinder V-form, and the four cylinder all in line type. The latter has gradually been developed to the stand ard automobile engine of to-day (see Fig. 58), running at a speed of 600 revolutions per minute to 3,000 revolutions per minute. Start ing at the left and upper part, cylinder No. 1 is the outside view. Cylinder No. 2 is cut away at the front, showing the poppet valves, H and controlling inlet and outlet of gases, re spectively; the valve chamber, H. and H.; the valve seats, H. and HT; the spark plug J, ; valve springs, S; the push rods, H. and Hs; the push rod guides, H. and FT.; and the cams, G. and G,. Cylinder No. 3 is cut through its centre, thus showing the piston, B; the wrist pin. B,; the connecting rod, C; the cylinder, A; the waterjacket, K; the combustion chamber, A, and the cylinder head A,. The crankshaft, F. is a high grade steel forging and has three main journals, F., and four crankpins, E. The valve timing or half-speed cam shaft, G, driven through gear, G., by pinion, F4,, on crankshaft, F. has three main bearings, G.. The four in let cams G., and the four outlet cams, G4, are fixed to this shaft. At the lower end of each of the connecting rods, C, is a splasher or oil dipper, C.. The crankcase, M, encloses the base of the engine. Splash troughs, L, are in the bottom of the crankcase beneath each con necting rod, C. The oil reservoir, or sump, Ali, is located beneath the crankcase. The parts requiring lubrication are the crankshaft bear ings, crank-pin bearings, piston pin bearings, cam-shaft bearings, timing gears, cams, valve lifter guides, pistons, piston rings and cylinder walls.
In almost all gasoline. engines the intake of fresh gas to the cylinder and the exhaust of the inert gases from the combustion chamber are governed by clashing ((poppet° valves. These valves are rather noisy. To eliminate this noise in automobile engines, Charles Y. Knight invented valves° also known as the Knight valves, which, besides offering other advantages, have proved to be noiseless. Two cylindrical sliding valves glide silently up and down between the cylinder wall and the piston, one working within the other. Ports or open ings in these sleeves register with each other and with the cylinder ports at proper inter vals, forming large and unobstructed passates for intake and exhaust gases. The operation of the sleeve valves is clearly explained in the accompanying illustration, Fig. 59. Fig. i60 shows a four cylinder fourcycle -gasoline en gine as adapted to airplane requirements. The weight of the engine has been reduced to three and one-half pounds per horse power. At a normal speed of 2,100 revolutions per minute the engine develops 125 horse power with a bore of four and three-quarter inches and a stroke of seven inches. By means of a reduction, the speed of the propeller shaft is reduced to 1,210 revolutions per minute.
Diesel Engine.— Dr. Rudolph Diesel of Munich, Bavaria, published in 1893 a book: "The Theory and Design of a Rational Heat Engine,° in which he described the principles of an ideal internal combustion engine, for the efficient operation of which he formulated the three main requirements. (1) Creation of the highest temperature in the cycle by mere com pression of pure air and not by combustion of the charge. (2) Gradual introduction of
atomized fuel into the highly compressed and consequently highly heated air in such a way that the temperature of the charge remains constant. (3) Proper selection of the air-gas ratio to allow a practical operation of the en gine without using a waterjacket.
The compression pressure of this ideal en gine was 250 atmospheres and the thermal effi ciency 73 per cent. Dr. Diesel expected con siderable trouble due to the high pressures, consequently he proposed another ((approxi matively ideal" cycle with lower compression pressure and efficiency. Patents granted to Diesel enabled him to form a partnership with the Maschinen Fabrik Augsburg and Friedrich Krupp of Essen. After several years of very difficult and tedious experimental work, Diesel found out that his ideal engine could not be realized. The oil engine, however, which developed by him and his associates between 1893 and 1898 showed an over-all efficiency of V per cent, and thus turned out to be by lar the most efficient heat engine yet built.
In Figs. 61 and 62 an early type of Diesel engine working on the four-stroke principle is illustrated. The main parts of the engine can be clearly recognized in the transverse section Fig. 61. They are the crankcase, the frame bearings, the vertical shaft, c, driving the hor izontal camshaft, H, and the governor, M, the air inlet valve, E, and the exhaust valve, A. The air furnished by the air compressor at a pressure of about 1,000 pounds per square inch with waterjacket; cylinder liner and cylinder cover, the piston with the wristpin, connecting rod and crankpin, the two-stage air compressor, L, driven by the connecting rod by means of a walking beam, the camshaft, H, with the cams, must be cooled before it is stored in the air flasks. By means of pipes the compressed air is carried from the flasks to the starting valve, F. and the fuel needle, B. To start the engine the piston must be moved slightly out of dead S, and the fuel pump (not shown), the starting valve, F, hnd the fuel needle, B, operated by the levers D and V, respectively. In the longi tudinal section Fig. 62 there are shown the crankshaft with flywheel and pulley, the three centre and the hand lever, G, laid down in the horizontal position. This throws the needle valve out of action and brings the lever arm D in contact with the starting cam, thusput ting the starting valve in operation and allow ing compressed air to enter the cylinder. The piston begins to move down and the speed of the engine increases. After the latter has made several revolutions the hand-lever G is turned back into the vertical, the operating position, in which the fuel needle is in regular operation and the starting valve at rest In this country the Busch-Sul-er Bros. Diesel Engine Company is the original and was, from 1898 to 1911, the only company manu facturing Diesel engines in America. It owns all United States patents granted to Dr. Ru dolph Diesel, and is closely associated with the old firm of Sulzer Brothers of Winterthdr, Switzerland, with which it is in intimate co operation. After the original United States Diesel patents had expired in 1912, many other engine concerns took up the manufacture of the Diesel engine. Figs. 63 to 65 illustrate some re cently designed Diesel engines of American make.
Bibliography.— Clerk, Dugald, Gas, Petrol, and Oil Engine> (New York 1909); Gfildner, H., 'The Design and Construction of Internal Combustion Engines> (New York 1910) ; Dubbel, H., 'High Power Gas Engine: Theory, Operation and Construction> (New York 1914) ; Carpenter, R. C., and Diederichs, H., (Theory, Construction and Operation of Internal Combustion (New York 1909) ; Heldt, P. M., 'Gasoline Motor: Its Dr sign and Construction> (Nyack, N. Y., 1916); Diesel, R., 'The Development of the Diesel En gine' (Berlin 1913); Supino, G., Diesel: Theory and Construction> (London 1913); Chalkley, A. P., (Diesel Engines for Land and Marine Work> (New York 1912) Holzwarth, H., 'The Gas Turbine: Theory, Construction, and Records of the Results Obtained from Two Actual Machines' (Philadelphia 1912) Supplee, H. H., 'The Gas Turbine> (Philadelphia 1910); Latta, N., 'American Producer Gas Practice> (New York 1905); lunge, F. E., 'Gas Power: A Study of the Evolution of Gas Power> (New York 1908).