Jacobs R-755 Explained

The 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.^[1]

Design and development

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

R-755A1:The base-line direct drive production version.^[2]

R-755A2:300 hp variant.

R-755A3:Similar to A1 but with Scintilla magnetoes.

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

• Anahuac Tauro
• Beechcraft Model 17 Staggerwing (B17L, C17L, E17L)
• Boeing-Stearman PT-18 Kaydet
• Cessna AT-17 Bobcat
• Cessna 195
• Funk F-23
• Grumman G-164 Ag Cat
• Kellett KD-1
• Lascurain Aura
• Morane-Saulnier MS.505 Criquet
• Waco F series (YMF, YPF)
• Waco Custom Cabin series (YOC, YQC)
• Waco Standard Cabin series (YKC, YKC-S, YKS-6)
• Waco PG-3 (twin-engined powered version of Waco CG-15 glider, prototype only)

Engines on display

• A preserved Jacobs R-755 is on display at the Arkansas Air Museum.^[3]
• 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.

External links

• The Jacobs Engine - Nanton Lancaster Society
• FAA Type Data Certificate Sheet - R-755
• Jacobs Engine Powered Plymouth Truck

Notes and References

1. Book: Gunston. Bill. World encyclopaedia of aero engines. 1989. P. Stephens. Wellingborough. 1-85260-163-9. 85. Fully rev. 2nd.
2. Book: Bridgman, Leonard. Jane's all the World's Aircraft 1955-56. 1955. Jane's all the World's Aircraft Publishing Co. Ltd.. London. 305.
3. http://www.arkairmuseum.org/engines/engine-jacobs755.php Arkansas Air Museum - Jacobs R-755