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THNSVYUIOUOVYETTENUUATEAT TET HH D EW two- cycle 8-cyl- inder high speed diesel engine de- veloped by F. B. Stearns. Two crank shafts. Pis- tons opposed and inclined. Advan- tages claimed: Low . fuel con- sumption, sim- plicity, minimum weight and space for power, vibra- tion practically eliminated. De- velops 170 h. p. at: 15600.-7. ps on. UUUVTAATUUTUAAT HLA LUA EMAT POOR PUeT PE New Two-Cycle High Speed Diesel Engine Developed F INTEREST among recent en- gineering developments is the 8-cylinder 2-cycle engine de- signed and built by F. B. Stearns, a pioneer in the automotive industry. The new engine is compact and is built of aluminum alloys with the ex- ception of such parts as the nickel iron cylinder sleeves, chrome nickel crankshafts and fuel camshafts, the connecting rods and the nitrided steel plunger and bushing of the fuel pump. In order to overcome vibration the two-stroke principle is employed and the eight cylinders are arranged in diamond fashion with 16 opposed pis- tons. The upper and lower crank- shafts are connected by double helical gearing at the rear of the engine. As far as known this is the first en- gine with cylinders arranged in the shape of a diamond. The cylinders are smaller than in the vertical op- posed piston type and can be easily scavenged; more even firing also re- sults. Occupies Minimum Space Bore of of the cylinders is 34-inch and the stroke 5 inches for each pis- ton, giving a total of 10-inch piston travel for each charge. The engine weighs 2000 pounds and develops 170 horsepower at 1500 revolutions per minute. The overall dimensions are: length, 68 inches; width, 33 inches; height, 50 inches. Length can be re- duced 10 inches by using rotary blow- er built in. A 750 horsepower unit would not increase the space occu- pied over 10 inches either way. Running range is from 200 to 1500 revolutions per minute. Based on the use of 26 to 28 Baume oil (a range of fuel from 22 to 40 Baume can be used) consumption is 0.4 to 0.42 pound per horsepower hour. Maximum com- bustion pressure is 900 pounds per square inch and compression pressure 450 pounds. Fuel pressure is 9000 pounds per square inch with 26 to 28 Baume oil. Actual tests show a maxi- mum exhaust temperature of 300 de- grees Fahr. In this engine a rotary blower is used for scavenging the cylinders at a pressure of approximately four pounds. As the upper and lower pis- tons recede on the firing stroke the four exhaust ports at the bottom of Vertical section through new Stearns diesel engine. Opposed Pistons in cyl- inders arranged in shape of diamond about center MARINE REvIEw—March, 1932 the cylinder are uncovered, and sub- sequently the four inlet ports at the top. It is obvious that as the air flows in under pressure an excess is pro- vided which results in supercharging. Flow of air in one direction is de- sirable because of the limited time for scavenging and providing a new supply of air. The high speeds, in- cidentally, are made possible by the thorough scavenging and by complete vaporization of the fuel. Nozzles of Special Design Special fuel nozzles are used and the fuel is supplied by a 3-cylinder plung- er pump which maintains constant pressure at each nozzle. The nozzles are of the needle valve type, and are operated positively by a _ tapered sliding cam and tappet. Speed of the engine can be con- trolled with instant response and flexibility within the speed range. Sliding fuel camshafts are mounted at each side, connected by linkage, the one at the left having a control han- dle. The fuel opening is increased by sliding the shaft fore and aft. The largest possible effective bear- ing area is used for piston pins and bushings by cutting away the lower half of each piston bushing. Corre- spondingly the upper half of each con- necting rod and its bushing has been cut away at each side leaving only about %-inch width at the top of the rod. Thus the effective area of the bearing in the thrust direction of the piston is larger in both the piston and connecting rod bushings by approxi- mately one-third that with orthodox design. A feature of the engine is the use of a cast aluminum alloy block, in which are inserted nickel iron alloy dry liners. ‘Tests have shown that the expansion of the sleeves, the cyl- inder block and the aluminum pistons are similar, which permits not only efficient radiation of heat but also pis- ton tolerances. Another unusual feature is that the engine can be arranged to run on gas- oline injected through the fuel noz- zles. The only changes necessary are the insertion of spark plugs and the lowering of the compression ratio by the use of different pistons. Tests on a similar type of engine show that this can be done satisfactorily with a compression ratio of 8 to 1 as against the ordinary ratio of 5% to 1 used in the present type gasoline engine. This engine has a high brake mean effective pressure of approximately 100, and’ a clear exhaust at all speeds and loads. Vibration is so slight that a coin placed on edge on the unit re- mains in a vertical position during the entire speed range. Cutless rubber bearings manufac- tured by the B. F. Goodrich Co.. Akron, are being installed on the 77-inch shaft of the Atlantic Lighter- age Corp. Mapre Lear, replacing the lignum-vitae bearing. 33