Wright Whirlwind J-5
| R-790 Whirlwind | |
|---|---|
 |
|
| Wright R-790 (J-5 Whirlwind) at National Air and Space Museum | |
| Type | Air-cooled 9-cylinder radial piston engine |
| National origin | United States |
| Manufacturer |
Wright Aeronautical Corporation Škoda Works (Czechoslovakia) Avia (Poland) |
| First run | 1923 |
| Major applications |
Spirit of St. Louis Fokker Trimotor Ford Trimotor |
The Wright R-790 Whirlwind was a series of nine-cylinder air-cooled radial aircraft engines built by Wright Aeronautical Corporation, with a total displacement of about 790 cubic inches (12.9 L) and around 200 horsepower (150 kW). These engines were the earliest members of the Wright Whirlwind engine family.
The R-790 Whirlwind began as the Lawrance J-1, a nine-cylinder air-cooled radial developed in 1921 by the Lawrance Aero Engine Company for the U.S. Navy. The Navy was very enthusiastic about air-cooled engines, which it felt were better suited for naval use than liquid-cooled ones. Lawrance was a small company, though, and the Navy doubted it could produce enough engines for their needs. Despite urgings from the Navy, the major U.S. aircraft engine makers, Wright and Curtiss, were satisfied with their liquid-cooled engines and showed no interest in building air-cooled ones. Since the Navy was already a major purchaser of Wright engines, it decided to force the issue by suggesting that Wright purchase Lawrance and build the J-1 itself, while informing the company that the Navy would not buy any more of its existing engines or spare parts. To keep the Navy's business, Wright was thus compelled to buy Lawrance in 1923, and the Lawrance J-1 became the Wright J-1.
By the time Lawrance merged with Wright, it had already developed the J-2, a more powerful version of the J-1 with slightly enlarged bore and displacement. However, Lawrance decided the J-1 was large enough, and the J-2 never went into production; only two examples were built.
Over the next two years, Wright gradually refined the J-1 engine, introducing the J-3, J-4, J-4A, and J-4B. The changes improved the engine's reliability, cooling, and fuel consumption, but the basic design, dimensions, and performance were unaltered.
The J-4 was the first engine to bear the Whirlwind name; previous engines had no name, only a designation.
The J-5 Whirlwind, introduced in 1925, was a complete redesign of the engine which greatly improved its cooling and breathing, further increasing its reliability and reducing its fuel consumption. Among the more visible changes were a much wider separation between the valves, for better cooling airflow, and completely enclosed pushrods and rocker arms, rather than exposed ones as on the earlier engines.
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