Jacobs R-755 (company designation L-4) is a seven-cylinder, air-cooled, radial engine for aircraft manufactured in the United States by the Jacobs Aircraft Engine Company.  Design and development Edit
The R-755 was first run in 1933 and was still in production in the 1970s. With a
bore and stroke of 5.25 in × 5 in (133 mm × 127 mm) the displacement was 757 cu in (12.4 L), power ranged from 200 hp to 350 hp (150 kW - 260 kW). The engine features steel cylinders with aluminum-alloy cylinder heads. An R-755E variant was developed for use in helicopters.
The base-line direct drive production version.
300 hp variant.
Similar to A1 but with Scintilla magnetoes.
De-rated version of the R-755A to drive a fixed pitch airscrew.
De-rated version of the R-755A to drive a variable or controllable pitch airscrew.
Up-rated engine with reduction gearing.
Developed to power the Jacobs Type 104 Gyrodyne.  Applications Edit Engines on display Edit
A preserved Jacobs R-755 is on display at the
Arkansas Air Museum.  A Jacobs R-755 is on public display at the
Aerospace Museum of California A preserved Jacobs R-755 is on display at Super T Aviation Academy in Medicine Hat, Canada.
A restored Jacobs R-755A is on display at the House of Whitley. Specifications (R-755-A1) Edit
Data from Jane's fighting aircraft of World War II, Jane's all the World's Aircraft 1938  
Type: 7-cylinder air-cooled radial piston engine
5.25 in (133 mm) Bore:
5 in (130 mm) Stroke:
757 cu in (12.4 L) Displacement:
Length: 37 in (940 mm) overall
Diameter: 43.5 in (1,100 mm) 505 lb (229 kg) Dry weight:
2 valves per cylinder, pushrod-actuated, sodium-cooled exhaust valves Valvetrain:
Fuel system: Single Stromberg NA-R7A carburetor
Fuel type: 73 octane
Oil system: One pressure pump, two scavenge pumps
Cooling system: Air-cooled Direct drive, right hand tractor Reduction gear:
Performance See also Edit
Gunston, Bill (1989). World encyclopaedia of aero engines (Fully rev. 2nd ed.). Wellingborough: P. Stephens. p. 85. ISBN 1-85260-163-9.
^ a b c d e
Bridgman, Leonard (1955). Jane's all the World's Aircraft 1955-56. London: Jane's all the World's Aircraft Publishing Co. Ltd. p. 305.
^ Arkansas Air Museum - Jacobs R-755 Archived 2010-12-03 at the
Wayback Machine Retrieved: 31 January 2009
Bridgman, Leonard, ed. (1989). Jane's fighting aircraft of World War II (1995 ed.). New York: Military Press. p. 305. ISBN 0-517-67964-7.
Grey, C.G.; Bridgman, Leonard, eds. (1938). Jane's all the World's Aircraft 1938. London: Sampson Low, Marston & company, ltd. pp. 86d–87d. External links Edit
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