Wright R-975
| R-975 Whirlwind | |
|---|---|
 |
|
| A Continental-built R-975 from a Sherman tank | |
| Type | Air-cooled 9-cylinder radial piston engine |
| National origin | United States |
| Manufacturer |
Wright Aeronautical Continental Motors |
| Major applications |
Beechcraft Staggerwing North American BT-9 Vultee BT-15 Valiant M4 Sherman tank Piasecki HUP Retriever |
| Produced | 1929-1950s |
| Number built | over 7,000 by Wright over 53,000 by Continental |
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 tracked armored vehicle in the world until the introduction of the turbine powered M1 Abrams in the 1980s.
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.
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