Jacobs R-915

The Jacobs R-915 or Jacobs L-6 is a seven-cylinder, air-cooled, radial engine for aircraft manufactured in the United States, production started in 1936.

Design and development

The R-915 was effectively an enlargement of the R-755 with strengthened stressed parts. With a bore and stroke of 5.5 in × 5.5 in (140 mm × 140 mm), for a displacement of 915 cu in (15 L). Take-off power was around 330 hp (250 kW). The engine features steel cylinders with aluminum-alloy cylinder heads.

Variants

R-915A1

Baseline variant; an enlarged R-755

R-915A3

Similar to the A1 but with Scintilla magnetoes

R-915A4

With a power take-off for autogyros

Applications

Engines on display

A preserved Jacobs R-915 is on display at the Nanton Lancaster Society.
A Jacobs L-6 is on display at the Canadian Museum of Flight

Specifications (R-915A1)

Data from Jane's

General characteristics

Type: 7-cylinder air-cooled radial piston engine
Bore: 5.5 in (140 mm)
Stroke: 5.5 in (140 mm)
Displacement: 915 cu in (15 L)
Length: 40 in (1,030 mm)
Diameter: 45.5 in (1,160 mm)
Dry weight: 555 lb (252 kg)

Components

Valvetrain: 2 valves per cylinder (pushrod-actuated); sodium cooled exhaust valves
Fuel system: Single Stromberg NA-R7A carburetor
Fuel type: 80 octane
Oil system: One pressure pump, two scavenge pumps
Cooling system: Air-cooled
Reduction gear: Direct drive, right hand tractor

Performance

Power output: 330 hp (246 kW) at 2,200 RPM at sea level
Specific power: 0.36 hp/cu-in (16.4 kW/L)
Compression ratio: 6:1
Power-to-weight ratio: 0.6 hp/lb (1 kW/kg)

External links

2015-09-23 at the Wayback Machine, Bomber Command Museum of Canada - Nanton Lancaster Society