Midlands exhibit


The French 130 horsepower Clerget 9B was an important engine for the British Royal Naval Air Service and Royal Flying Corps, being produced under licence in Britain and powering a number of important British aircraft including the Sopwith Camel. However, it was expensive at £907 and prone to overheating. Lieutenant W. O. Bentley was asked to solve its problems. Bentley came up with a modified engine - fitted with aluminium cylinders, cast iron liners, and aluminium pistons. Dual ignition was added to improve reliability, and the stroke increased which allowed power to be increased to 150 horsepower The cost of the engine reduced to £605.

The resulting engine was initially known as the A.R.1 for ‘Admiralty Rotary’, and later the BR.1 ‘Bentley Rotary’. The BR.1 developed into the BR.2, a heavier, more powerful engine.

The BR2 model shown here was photographed at the 2018  Midlands Exhibition. It is quarter scale to the Lew Blackmoor design.

After he had won the Duke of Edinburgh Challenge Trophy with his model of this engine at the 1982 Model Engineer Exhibition Lew Blackmore produced a detailed book 1986. Modelling the BR2 makes a fascinating and challenging project for the more experienced model engineer; it is also a popular one judging by the number of examples seen at exhibitions.

No castings are required. The book contains full drawings, as well as a detailed description of the construction methods used by the author It also includes a full reprint of the 1925 MoD descriptive handbook for the engine. Sadly the book now seems to be out of print, although used copies can be found.

Drawings are available at https://www.sarikhobbies.com/product/bentley-rotary-pe33/