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. First run in 1916, 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.
To extract more power from the Cossack lineage Coatalen designed a W-18 version known as the Sunbeam Viking. This engine used Cossack blocks in a W arrangement with 60° between banks having a capacity of 33.6 l (2,050 cu in) giving 450 hp (336 kW) @ a propeller speed of 900rpm. Orders for 50 engines were received, intended to power the large AD Seaplane Type 1000 aircraft, but most of the nine engines produced were fitted to motor boats, the remaining 41 being cancelled.
The basic production V-12 engine with cast-iron blocks, 110 mm (4 in) bore and single ignition system fed by two magnetos. Rated at 310 hp (231 kW) at 2,000rpm.
An improved Cossack with dual ignition system and hand / compressed air starter. Rated at 320 hp (239 kW) at 2,000rpm.
Built for airship use. Produced 350 hp at 2,000 rpm and weighed 1,200 lb (540 kg) dry.
Number built 1916-1920:
Cossack III 14
AD Seaplane Type 1000
Short Type 310
Porte Baby FB.2
Handley Page Type O/400
Tellier Flying boat
HM Airship R36
HM Airship R37 Airship scrapped when 95% complete
HM Airship R38 (R38 class discontinued)
Type: V-12 water-cooled piston engine
Bore: 110 mm (4 in)
Stroke: 160 mm (6 in)
Displacement: 18.246 l (1,113 cu in)
Length: 1,569 mm (62 in)
Width: 960 mm (38 in)
Height: 988 mm (39 in)
Dry weight: 622.5 kg (1,372 lb) Running
Designer: Louis Coatalen
Valvetrain: Twin overhead camshaft, two exhaust and two inlet valves per cylinder
Fuel system: 4 x Claudel-Hobson CS 42 mm (2 in) bore carburettors, gravity fed
Fuel type: Gasoline
Oil system: Dry sump, pressure fed
Cooling system: Water-cooled by radiator
Reduction gear: 2:1
Power output: 238.6 kW (320 hp) @ 2,000rpm