Bentley BR2

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Bentley BR2 Rotary engine.jpg
Preserved Bentley B.R.2
Type Rotary engine
Manufacturer Humber Limited
First run 1916
Major applications Sopwith Snipe
Number built 2,567
Developed from Bentley BR.1

The Bentley B.R.2 was a British rotary aircraft engine developed during the First World War by the motor car engine designer W. O. Bentley from his earlier Bentley BR.1. Coming as it did near the end of the war, the BR.2 was built in smaller numbers than the earlier BR.1 – its main use being by the Royal Air Force in the early 1920s.[1]

Design and development[edit]

The initial variant of the BR.2 developed 230 horsepower (170 kW), with nine cylinders measuring 5.5 by 7.1 inches (140 mm × 180 mm) for a total displacement of 1,522 cubic inches (24.9 L). It weighed 490 pounds (220 kg), only 93 pounds (42 kg) more than the Bentley B.R.1 (A.R.1).

The Sopwith Snipe, selected as the standard single-seat fighter of the post-war RAF was designed around the BR.2 – it was also used by the ground attack version of the Snipe, the Sopwith TF-2 Salamander.

This was the last type of rotary engine to be used by the RAF – later air-cooled aircraft engines being almost entirely of the fixed radial type. The BR.2 represented the peak of rotary engine development.[2]


BR.2 230
1918, 230 hp.
BR.2 245
1918, 245 hp.


Gloster Nightjar during evaluation at Farnborough in 1922

Engines on display[edit]

A Bentley BR.2 is on public display in the Science Museum (London), another forms part of the aero engine collection at the Royal Air Force Museum Cosford.

A ¼ scale working replica of the Bentley BR.2 World War I rotary aero engine built by Lewis Kinleside Blackmore is currently on display at the Bentley Memorial Building in Oxfordshire, UK. This was the first model built of this engine and is the subject also of a book by L K Blackmore.

The Canada Aviation and Space Museum in Ottawa, Ontario, Canada has a BR.2 installed in their Sopwith 7F.1 Snipe.

Specifications (BR.2)[edit]

Manufacturer's plate (dated November 1917) and valve operating gear of the BR.2 engine on display at the Royal Air Force Museum Cosford

Data from Jane's [3]

General characteristics

  • Type: 9-cylinder rotary
  • Bore: 5.51 in (140 mm)
  • Stroke: 7.09 in (180 mm)
  • Displacement: 1521.8 in (24.94 L)
  • Dry weight: 490 lb (220 kg)


  • Valvetrain: Overhead valve
  • Cooling system: Air-cooled


  • Power output: 250 hp
  • Fuel consumption: 20 gallons per hour
  • Oil consumption: 16 pints per hour
  • Power-to-weight ratio: 0.5 hp/lb

See also[edit]

Related development
Comparable engines
Related lists



  1. ^ Lumsden 2003, p.88.
  2. ^ Gunston 1989, p.22.
  3. ^ Jane's 1993, p.274.


  • Gunston, Bill (1986). World Encyclopedia of Aero Engines. Wellingborough: Patrick Stephens. pp. 25–26. 
  • 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 I. London. Studio Editions Ltd, 1993. ISBN 1-85170-347-0
  • Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.

External links[edit]