Jacobs R-755

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R-755 / L-4
Blue Stearman PT-18 engine.JPG
Jacobs R-755 installed in a Boeing-Stearman Model 75
Type Radial engine
Manufacturer Jacobs Aircraft Engine Company
First run 1933

The Jacobs R-755 (company designation L-4) was a seven-cylinder, air-cooled, radial engine for aircraft manufactured in the United States by the Jacobs Aircraft Engine Company.[1]

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.

Variants[edit]

R-755A1
The base-line direct drive production version.[2]
R-755A2
300hp variant.
R-755B1
De-rated version of the R-755A to drive a fixed pitch airscrew.[2]
R-755B2
De-rated version of the R-755A to drive a variable or controllable pitch airscrew.[2]
R-755E
Up-rated engine with reduction gearing.[2]
R-755EH
Developed to power the Jacobs Type 104 Gyrodyne.[2]

Applications[edit]

Engines on display[edit]

Specifications (R-755-A1)[edit]

Data from Jane's[4]

General characteristics

  • Type: 7-cylinder air-cooled radial piston engine
  • Bore: 5.25 in (133 mm)
  • Stroke: 5.0 in (127 mm)
  • Displacement: 757 cu in (12.4 L)
  • Length: 27.25 in (692 mm)
  • Diameter: 44 in (1,188 mm)
  • Dry weight: 505 lb (229 kg)

Components

  • Valvetrain: 2 valves per cylinder, pushrod-actuated, Sodium cooled exhaust valves
  • Fuel system: Single Stromberg NA-R7A carburetor
  • Fuel type: 73 octane
  • Oil system: One pressure pump, two scavenge pumps
  • Cooling system: Air-cooled
  • Reduction gear: Direct drive, right hand tractor

Performance

See also[edit]

Comparable engines
Related lists

References[edit]

Notes[edit]

  1. ^ Gunston 1989, p.85.
  2. ^ 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. 
  3. ^ Arkansas Air Museum - Jacobs R-755 Retrieved: 31 January 2009
  4. ^ Janes 1989, p.305.

Bibliography[edit]

  • Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
  • Jane's Fighting Aircraft of World War II. London. Studio Editions Ltd, 1989. ISBN 0-517-67964-7

External links[edit]