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Wright Cyclone was the name given to a family of air-cooled radial piston engines designed by the Wright Aeronautical Corporation and used in numerous American aircraft in the 1930s and 1940s.
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Background
The Wright Aeronautical Corporation was formed in 1919, initially to develop liquid-cooled Hispano-Suiza V8 engines under licence. The Corporation’s first original design, the R1, was also the first successful high-powered radial in the USA. Funded by contracts from the US Navy for new air-cooled radials, Wright started a new design (initially called the P2) in 1924. The resignation of Frederick B. Rentschler to form the Pratt & Whitney Aircraft Company, along with several key engineering personnel, seriously affected the development of the P2 and it did not go into production.
R-1750 Cyclone 9
A new design was launched in 1926, known as the R-1750 Cyclone. This was a nine-cylinder radial with a displacement of 1750 cu in and internally cooled exhaust valves. It was type-tested at 500 hp in 1927.
R-1820 Cyclone 9
In 1932, the R-1750 was developed to a capacity of 1823 cu in. This was the F model Cyclone, designated R-1820. This engine introduced a forged aluminium crankcase and was developed through the 1930s to reach 890 hp. It used a General Electric supercharger, and Wright concluded that this feature limited the potential power output of the engine. For the next development, the G-Series of 1937, Wright developed its own single-speed supercharger. The G-series was developed to deliver 1200 hp at 2500 rpm and made up the bulk of R-1820 Cyclone production during World War 2. It was installed in the Boeing B-17 Flying Fortress. The final phase of development of the single-row radial design was the H-Series at 1350 hp. A licensed variant was developed as the Shvetsov M-25.
R-2600 Cyclone 14 (Twin Cyclone)
Wright went on to develop two-row engines with 14 cylinders in two rows of seven, called the Cyclone 14, R-2600. This was installed in the Boeing 314, Grumman TBM/TBF Avenger, North American B-25 Mitchell, and some models of the Douglas A-20 Havoc (RAF Boston).
R-3350 Cyclone 18 (Duplex Cyclone)
The penultimate Cyclone development was the 18-cylinder engine R-3350, named the Duplex Cyclone or Cyclone 18. Among other applications, it was installed in the Boeing B-29 Superfortress, Douglas A-1 Skyraider, Lockheed P-2 Neptune, and Lockheed C-121 Constellation. In commercial applications it stayed in production until 1957.
R-4090 Cyclone 22
An experimental 22-cylinder two-row radial intended to compete with the large Pratt & Whitney radial engines. Three prototypes are known to have been built, but development was abandoned to allow resources to be used for the R-3350 development programme.