Bentley BR2

The Bentley BR.2 was a nine-cylinder British rotary aircraft engine developed during the First World War by W. O. Bentley from his earlier BR.1. The first variant produced 230 horsepower from nine cylinders measuring 5.5 by 7.1 inches, a displacement of about 1,522 cubic inches, and weighed 490 pounds, only 93 pounds more than the BR.1. It was built in small numbers during the war and used mainly by the Royal Air Force in the early 1920s. The Sopwith Snipe, chosen as the standard single-seat fighter of the post-war RAF, was designed around it, as was the ground attack Sopwith Salamander. It was the last type of rotary engine adopted by the RAF, because later air-cooled engines such as the Jupiter and the Jaguar were almost entirely fixed radials. Surviving examples are displayed at museums including the Science Museum in London and the Royal Air Force Museum Cosford.