The Bentley B.R.2 was a nine-cylinder 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. The BR.2 was built in small numbers during the war, its main use being by the Royal Air Force in the early 1920s.[1]
The initial variant of the BR.2 developed 230hp, with nine cylinders measuring 5.5inchesx7.1inchesin (xin) for a total displacement of 1,522 cubic inches (24.9 L). It weighed 490lb, only 93lb more than the Bentley BR.1.
This was the last type of rotary engine to be adopted by the RAF – later air-cooled aircraft engines such as the Cosmos Jupiter and Armstrong Siddeley Jaguar being almost entirely of the fixed radial type. With the BR.2, the rotary engine had reached a point beyond which this type of engine could not be further developed, due to its inherent limitations.[2]
The type selected as the standard single-seat fighter of the post-war RAF, the Sopwith Snipe, had been designed around the BR.2, as had its ground attack version, the Sopwith TF.2 Salamander. A number of other experimental and minor production types were either designed for, or otherwise fitted with this power plant during the late "war" years and into the early 1920s.
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. Another one (serial number 40543, manufactured by Gwynnes) is in the National Military Museum, Romania.
The sole operational BR.2 is mounted in Fantasy of Flight's replica of the Sopwith Snipe.[3]
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.