History of aicraft piston engines

T he first production e ngine was delivered to the

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Unformatted text preview: inary layouts were approved by t he WPB and some extra help was called in. Complete layouts were approved 4 June, all drafting was completed by 15 June, the first 8-cylinder e ngine was delivered to the Bureau of Standards for test 3 July, and the first 12-cylinder e ngine completed the official 50-hr test 25 August 1917. T he first " production" e ngine was delivered to the Army Air Service in D ayton on Thanksgiving Day 1917, j ust 6 months after Vincent and Hall h ad started their layout. I believe this record has never been equaled, before or since, except perhaps by the first Pratt & Whitney Wasp, described later. 9 T he design was based on the welded-cylinder construction pioneered by Mercedes. It had no radical features, but was an excellent synthesis of the state of t he a rt of its t ime. I ts principal weaknesses were cracking of the cylinder-head water jackets, burning of exhaust valves, and breaking of accessory gears. These faults were gradually reduced as time went on, a nd it c ame to be considered a reliable engine. Early production engines h ad a 50-percent chance of passing the government 50-hr endurance test. I n later modification a bar was welded between the ports to reduce cylinder 30 F igure 2 6.—Liberty V -12 engine, 1 9 1 8 ; 4 2 0 hp at 1700 r p m , 8 5 6 lb. I t has Mercedes-type cylinder c onstruction (see also f i g . 34b). (Photo A-691) F igure 2 7.—Liberty 1 2A, V-12 engine, t ransverse section viewed f r o m rear, 1 918. ( From Aerosphere 1939, p. 467) F igure 2 8.—Wright A eronautical Corp. H ispano-Suiza Model E V-8 engine, m agneto end, 1 9 2 0 ; 180 hp at 1700 r pm, 4 7 0 l b. The French-built model w as rated at 150 hp (see also f i g . 34c). (P/?ofoA-5i0iJ) F igure 2 9.—Hispano-Suiza V -8 engine, t ransverse section, viewed f r o m r ear. (From The French Hispano-Suiza Aero Engine, Instruction Book, p. 25) d istortion and jacket cracking, and heavier teeth were used in the gears. T he only major weakness remaining was in the exhaust valves, which served well most of the time. L arge quantities of the L iberty-12 e ngine were produced by the automobile companies, including Packard, Ford, Lincoln, and some General M otors divisions. It was used by the British in military airplanes as well as by the United States Army Air Service and Naval Flying Corps. Liberty e ngine production was far ahead of airplane production in this country, a nd at the end of the war many thousands of these engines were on hand. M any were sold at low prices to "rum runners" and were very successfully used in running liquor through the Coast Guard blockade along the Atlantic a nd Pacific coasts during the Prohibition Era. During these years the Coast G uard had no "requirements" for a light and powerful marine engine, and t heir motor boats were far outclassed by the Liberty-equipped bootleggers' craft. T he Liberty engine remained important in United States Army and N avy aviation well into the 1930s. T...
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