Wright R-4090 Cyclone 22

The R-4090 Cyclone 22 was an experimental radial piston engine designed and built in prototype form in the United States during the 1940s.^[1]

Design and development

During the 1940s, Wright Aeronautical Corporation was constantly in competition with Pratt & Whitney for new engine designs required for civil and military aircraft. Utilising the Wright R-3350 as a basis, Wright developed a 22-cylinder engine, using R-3350 cylinders arranged as a two-row radial engine with 11 cylinders per row.^[1]

The air-cooled R-4090 was rated to deliver 3,000 hp (2,200 kW) at 2,800 rpm for take-off, from a total displacement of 4,092 cu in (67.06 l), with a compression ratio of 6.85:1. Improved performance was expected from the R-4090 if it was proceeded with. A two-speed single-stage supercharger helped maintain rated power to higher altitudes.^[1]

The core of the engine was a forged steel crankcase which enclosed the three piece two-throw crankshaft. The cylinders were arranged equally around the crankcase, with each row off-set by 16.3636^.° to ensure cooling airflow. Accessories similar to other Cyclone engines were arranged around the rear face of the crankcase and a 0.333:1 planetary reduction gearbox at the front.^[1]

Although there are no records of failings of the R-4090, the engine was abandoned to allow development of the R-3350 Cyclone 18 series.^[1]

Variants

XR-4090-1

(790C22AA1), drove a single propeller.^[1]

R-4090-3

(792C22AA), drove a contra-rotating propeller shaft and was intended to have a two-speed reduction gearbox to maximise efficiency in cruising flight.^[1]

Specifications (XR-4090-1)

Data from enginehistory.org,^[2] Old Machine Press^[1]

General characteristics

• Type: Air-cooled 22 cylinder two-row radial piston engine
• Bore: 6.125 in (155.6 mm)
• Stroke: 6.3125 in (160.3 mm)
• Displacement: 4,092 cu in (67.06 l)
• Length: 91 in (2,300 mm)
• Diameter: 58 in (1,500 mm)
• Dry weight: 3,230 lb (1,470 kg)

Components

• Valvetrain: One inlet and one Sodium-cooled exhaust over-head valves per cylinder, driven by pushrods and rocker arms.
• Supercharger: 14 in (360 mm) diameter impeller, single-stage two-speed supercharger; gear ratios: of 5 to 1 and 7 to 1.
• Fuel type: Gasoline
• Reduction gear: 0.333:1 planetary reduction gearbox

Performance

• Power output: 3,000 hp (2,200 kW) at 2,800 rpm for take-off
• Compression ratio: 6.85:1

References

Further reading

• White, Graham (1995). Allied aircraft piston engines of World War II : history and development of frontline aircraft piston engines produced by Great Britain and the United States during World War II. Warrendale, PA: Soc. of Automotive Engineers. ISBN 978-1560916550. 
• White, Graham (14 February 2006). R-4360: Pratt & Whitney's Major Miracle. Specialty Press. ISBN 1580071732. 
• USAF US Navy: Engine model designation system (revised 1 January 1950 ed.). Air Material Command. Retrieved 24 September 2015. 
• The Wright Cyclones. Wright Aeronautical Corporation. 1942.