The Wright R-1300 Cyclone 7 is a 7-cylinder radial engine produced by Curtiss-Wright in the USA. It was developed from the larger twin-row Wright R-2600. Design work was started in 1942 but the first flight of an R-1300 did not take place until 1949. The engine was produced under license at Kaiser-Frazer and, later, at Lycoming.
The engine was used in the North American T-28A Trojan and the Sikorsky S-55A helicopter. For use in the S-55A helicopter the power of the R-1300 was reduced to 700 hp to improve reliability. Sikorsky engineers inclined the engine at a 45-degree angle so that the drive shaft would not run through the main cabin, though this created a partition between the cockpit and main cabin. However, the addition of clamshell doors to the nose of the aircraft made maintenance access to the engine far simpler than it had ever been before.
The Museum's example is shown with the complete S-55 helicopter installation. The engine mount inclines the engine to align with the transmission to the rotor blades. A cooling fan assists in keeping the engine temperatures in a satisfactory range while the helicopter is stationary.