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 3000NaN0 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 1100NaN0 and stroke of 1300NaN0. Output from the Cossack was 3100NaN0 at 2,000rpm, with a running weight of 1372.50NaN0, 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 3200NaN0.
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.[1] Only 14 Cossack IIIs were built due to the cancellation of the post-war British airships.
In similar fashion to other engine families designed by Coatalen the Cossack spawned a straight-six derivative in the Amazon, in effect half a Cossack, retaining the 110 x 160mm bore/stroke, overhead camshaft, four poppet valves per cylinder and cast-iron cylinder blocks in groups of three. An output of 1600NaN0 from 9.20NaN0 for a running weight of 7470NaN0 led to a high power to weight ratio. Despite the high output the Amazon was little used in Britain, with only possible use aboard Coastal airships and some supplied to the Imperial Russian Air Service. Amazon production totalled 77 out of an order for 100, 23 of which were cancelled. A non-aviation use version of the Amazon was produced as the Sunbeam Amazon II, fitted with hand and/or compressed-air starters and single magneto ignition system.
Development paths favoured by Coatalen included increasing the bore and Aluminium alloy cylinder blocks. Aluminium alloy cylinder blocks and the bore increased to 1220NaN0, the capacity increased to 11.230NaN0 to produce the Sunbeam Saracen straight-six. Delivering 2000NaN0 at 2,000 rpm, driving a propeller through a 2:1 reduction gear. When submitted to the Internal Combustion Engine Committee of the National Advisory Committee for Aeronautics the Saracen faced stiff competition from the Beardmore 160 hp and Hispano-Suiza 8 and did not attract any orders. Only prototypes of the Saracen were built.
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 33.60NaN0 giving 4500NaN0 at a propeller speed of 900 rpm. 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 final fling of the Cossack family was the Sunbeam Matabele, retaining the Aluminium alloy blocks and 1220NaN0 bore of the Saracen the V-12 Matabele delivered 4200NaN0 at 2,000rpm through a 1.63:1 reduction gear from 9.20NaN0. Developed in two versions, the Sunbeam Matabele I, for aviation use, was fitted with four magnetos to provide redundancy for the dual ignition system, whilst the Sunbeam Matabele II was only fitted with two magnetos supplying a single ignition system for non-aviation use. Used mainly in Airco DH.4 bombers, the Matabele also found favour as a power-boat and speed-record car engine. No Matabeles were built during the First World War, but prototypes and at least eight production engines were built after the war for various applications.
The Matabele engine is best known today for powering the Sunbeam 1000 hp land speed record car, the first car to exceed 200 mph.
After taking the land speed record at 152.330NaN0 with the Sunbeam Tiger, Segrave realised that his small, lightweight racing car would be inadequate to hold the record against the aero-engined leviathans now appearing in the contest. The S.T.D. Motors team was short of funds and so little new development was possible.
A pair of Matabele engines were found in the Sunbeam works at Wolverhampton, previously from the ill-fated Maple Leaf VII powerboat. As the Sunbeam 1000 HP is reported as having 4 magnetos per engine,[2] these would appear to be Matabele I, rather than Matabele II engines.[3]
On 29 March 1927, the Sunbeam became the first car to exceed 200 mph. Although loudly trumpeted as the "1000 HP" Sunbeam, the actual power was somewhere around 900 bhp.
The installation of these engines was somewhat unorthodox, necessitated by the limited funds for new work. The rear engine was started first by compressed air starting, then the front engine was started through a mechanical friction clutch. Once synchronised, they were locked together with a dog clutch for the record attempt. The car's last run was a demonstration circuit at Brooklands, running at slow speed on only one engine, with this dog clutch disconnected.