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Clerget 7Z Aero Engine Manual (1916)

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GWYNNES LTD, London, c.1916

A very rare original WW1 edition of the Gwynnes Ltd instruction manual for the Clerget 7Z 80 hp rotary aero engine. Undated, but published c.1915-1916, as the 7Z had been replaced by more powerful Clerget engines by 1917. The manual includes a general description of the 7Z engine, its components and its operation. There are also instructions for assembling and mounting the engine, and making any necessary adjustments to valves, magnetos, oil supply, etc. A comprehensive illustrated list of parts and tools is included, and there are a number of blank notes pages for any amendments that would have been added. The manual is illustrated with detailed scale drawings of the engine, and diagrams of various components.

Clerget 7Z Aero Engine: was a seven-cylinder rotary aircraft engine of the WW1 era designed by Pierre Clerget in 1911. It was nominally rated at 80 horsepower. 347 examples were jointly built in Britain by Gordon Watney & Co Ltd of Weybridge and Gwynnes Limited of Hammersmith. It was fitted to various RFC aircraft, including the Avro 504 and the Sopwith Pup. The Clerget engine was also manufactured in Germany under licence. Known there as the Oberursel engine, it was used in Fokker aircraft. The 7Z produced 85 hp at 1200 rpm. With a 120 mm (4.724") bore, 150 mm (5.905") stroke, 11.875 l (724.6 in³) displacement and 4:1 compression ratio, its fuel consumption was 0.665 lb/hp/hr oil consumption was 0.12 lb/hp/hr. Inlet valves opened at top centre and closed 50° late and exhaust valves opened 68° early and closed 0° – 5° late. Weight was 216 lb, or 2.7 lb/hp. Its diameter was 36.25" and length 32". 

Clerget, Blin and Cie, 37 Rue Cavé, Levallois, Paris built aero engines from c.1911 until manufacturing rights were sold to Renault. They were best known for the air-cooled rotary engines which were built and licensed during WWI, and which powered some of the RFC’s most famous aircraft, including the Sopwith Pup, Sopwith Camel and Avro 504K. Gwynnes Ltd held the British manufacturing rights for Clerget designs during the war. Clerget designed air-cooled rotaries with seven, nine, and eleven cylinders. Their cylinders, machined with integral cooling fins from solid steel billets, were gripped between the two steel crankcase halves. The crankcase nose piece carried the propeller hub.


In very good condition. The boards are is in very good condition, with general signs of wear and use, and some marks. The binding and hinges are very good and secure. The text and illustrations are in very good condition.

Published: c.1916
Red cloth-covered boards with gilt titling
Illustrated with diagrams and line drawings
Dimensions: 155mm x 240mm
Pages: 31 (plus blank notes pages)