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The Wright R-975 Whirlwind was a series of nine-cylinder air-cooled radial aircraft engines built by the Wright Aeronautical division of Curtiss-Wright. These engines had a displacement of about 975 in³ (16.0 L) and power ratings of 300-450 hp (225-335 kW). They were the largest members of the Wright Whirlwind engine family to be produced commercially, and they were also the most numerous. During World War II, Continental Motors built the R-975 under license as a powerplant for Allied tanks and other armored vehicles. Tens of thousands of engines were built for this purpose, dwarfing the R-975's usage in aircraft. After the war, Continental continued to produce its own versions of the R-975 into the 1950s; some of these produced as much as 550 hp (410 kW). The R-975 is most famous for being used as the power plant for the M18 Hellcat tank destroyer, the fastest and most efficient American tank killer of World War II. The R-975 powered M18 remained the fastest armored vehicle in the world until the introduction of the turbine powered M1 Abrams in the 1980s.〔Patton's Vanguard: The United States Army Fourth Armored Division, By Don M. Fox. P.25〕 ==Design and development== Wright introduced the J-6 Whirlwind family in 1928 to replace the nine-cylinder R-790 series. The J-6 family included varieties with five, seven, and nine cylinders. The nine-cylinder version was originally known as the J-6 Whirlwind Nine, or J-6-9 for short. The U.S. government designated it as the R-975; Wright later adopted this and dropped the J-6 nomenclature. Like all the members of the J-6 Whirlwind family, the R-975 had larger cylinders than the R-790. The piston stroke of 5.5 in (14.0 cm) was unchanged, but the cylinder bore was expanded to 5.0 in (12.7 cm) from the R-790's bore of 4.5 in (11.4 cm). While the R-790 was naturally aspirated, the R-975, like the other J-6 engines, had a gear-driven supercharger to boost its power output. Wright gradually developed the R-975, at first using suffix letters to indicate successive versions. The original R-975 (or J-6-9) was rated for 300 hp (224 kW),〔Curtiss-Wright (1940), p. 11〕 while the R-975E of 1931 could do 330 hp (246 kW) thanks to an improved cylinder head design.〔Curtiss-Wright (1983), p. 2〕〔Curtiss-Wright (1940), p. 13〕〔FAA Type Certificate Data Sheet ATC 21〕 Wright later added numeric suffixes to show different power levels. The R-975E-1, introduced the same year as the R-975E, was rated at 365 hp (272 kW) thanks to higher-compression pistons and a slightly greater RPM limit.〔〔Curtiss-Wright (1940), p. 14〕〔FAA Type Certificate Data Sheet TC 87〕 An even more powerful version, the R-975E-3, was also introduced that year, with greater supercharging and a still higher RPM limit, and was progressively refined until the final model of 1935 could reach 450 hp (336 kW) for takeoff.〔〔Curtiss-Wright (1940), pp. 14, 16, 18〕〔FAA Type Certificate Data Sheet TC 125〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Wright R-975」の詳細全文を読む スポンサード リンク
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