Wright J-6

Whirlwind series
Partially sectioned Wright J-4B at Canada Aviation Museum
Type	Air-cooled radial piston engine
National origin	United States
Manufacturer	Wright Aeronautical

The Wright Whirlwind was a family of air-cooled radial aircraft engines built by Wright Aeronautical (originally an independent company, later a division of Curtiss-Wright). The family began with nine-cylinder engines, and later expanded to include five-cylinder and seven-cylinder varieties. Fourteen-cylinder twin-row versions were also developed, but these were not commercially produced.

The Whirlwind was a direct descendant of the Lawrance J-1, a nine-cylinder air-cooled radial built by the Lawrance Aero Engine Company for the U.S. Navy. Because the Navy was very enthusiastic about air-cooled radials, but was concerned that Lawrance could not produce enough engines for its needs, it forced Wright to purchase the Lawrance company in 1923 and build the J-1 itself. Wright's J-1 was the first engine in its nine-cylinder R-790 Whirlwind series and was quickly followed by the J-3, J-4, J-4A, J-4B, and finally the popular and successful J-5 of 1925.

In 1928, Wright replaced the R-790 series with the J-6 Whirlwind family, in which a supercharger was added to boost engine power and the cylinders were enlarged by expanding the bore. This family included three members: the nine-cylinder R-975, the seven-cylinder R-760, and the five-cylinder R-540, providing a range of different power levels using the same basic design. Of these, the R-975 proved the most popular, especially because of its use in armored fighting vehicles during World War II.

During the mid-1930s, Wright also developed two fourteen-cylinder double-row versions of the Whirlwind, the R-1510 of 600 hp (450 kW), and the R-1670 of 800 hp (600 kW). These were used in a number of military aircraft prototypes, but neither engine reached the production stage.

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Wikipedia