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Sunbeam Cossack

Cossack
Type V-12, 60 degree, water-cooled, piston engine
National origin Britain
Manufacturer Sunbeam
Designed by Louis Coatalen
First run 1916
Major applications Short Type 310
Produced 1916-1920
Number built UK 350
France 150
US 1+?
Cossack III 14

The Sunbeam Cossack was a British 12-cylinder aero engine that was first run in 1916. The Cossack spawned a family of engines from Sunbeam.

As the First World War raged through 1914 and 1915, The Admiralty demanded engines with more power for its existing and future aircraft. The problem was exemplified by the Short Type 184 seaplanes of the RNAS, powered by Sunbeam Mohawk engines, which could barely lift the standard air-dropped torpedo with crew reduced to two and minimal fuel. An engine with a base rating of at least 300 hp (224 kW) was demanded by the Admiralty. Responses came from Rolls-Royce with the Rolls-Royce Eagle and Sunbeam with the Sunbeam Cossack.

Louis Coatalen designed the Cossack as a twin overhead camshaft 60° V-12, with four valves per cylinder, bore of 110 mm (4 in) and stroke of 130 mm (5 in). Output from the Cossack was 310 hp (231 kW) @ 2,000rpm, with a running weight of 1,372.5 lb (623 kg), driving a large diameter propeller through a 2:1 reduction gear. Construction of the Cossack was largely of aluminium alloy with cast-iron cylinder blocks and integral heads in groups of three.

Large orders were placed for the Cossack but deliveries were very slow, with only eleven, largely hand-built, engines delivered from March 1916 to September 1916. The end of Sunbeam Gurkha production in October 1916 freed up factory resources to allow up to thirty engines a month to be delivered until Cossack production ended in December 1917 after 350 deliveries.

Development of the basic engine produced the Sunbeam Cossack II with four magnetos, to counter the unreliability of British contemporary magnetos, and a compressed-air or hand driven starter, rated at 320 hp (239 kW).

Late in the First World War Britain’s airship aspirations were boosted by the order for the R36, R37 and R38. All three airships were powered a variety of engines including the Sunbeam Cossack III a derivative of the Cossack with a flywheel, hand or air starter, engine controls and magnetos mounted directly on the engine for access by the engine mechanics. The Cossack 3 was designed with a water-cooled exhaust and speed governor. The overhead camshaft was gear driven from the crankshaft. Only 14 Cossack IIIs were built due to the cancellation of the post-war British airships.


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