Sunbeam Arab / Bedouin / Kaffir / Dyak
By 1916 the demand for aero-engines was placing huge demands on the manufacturing industry. To help ease the pressure the War Office standardised on engines of about 200 hp (149 kW), one of these was a 90 degree V-8 water-cooled engine from Sunbeam known as the Arab. Using cast Aluminium alloy cylinder blocks and heads with die-cast Aluminium alloy pistons, the V-8 Arab had a bore of 120 mm (5 in), and stroke of 130 mm (5 in) for a capacity of 11.76 l (718 cu in) litres, developing 208–212 hp (155–158 kW) at 2,000 rpm.
First bench-run in 1916, the Arab was obviously inspired by the Hispano-Suiza V-8 engines but with very little in common when examined in detail. After submission to the Internal Combustion Engine Committee of the National Advisory Committee Sunbeam received an order for 1,000 in March 1917, increased to 2,000 in June 1917 as well as another 2,160 to be built by Austin Motors (1,000), Lanchester Motor Company (300), Napier & Son (300) and Willys Overland (560) in the United States of America. Bench testing revealed defects which required rectification, delaying completion of production drawings. Despite the delays one of the first flight-ready Arab flew in a Martinsyde F.2 two-seat fighter/reconnaissance aircraft in mid 1917.
Service use of the Arab was coloured by poor reliability and persistent vibration problems, causing some 2,350 orders to be cancelled and remaining orders 'settled', compensating manufacturers for costs incurred. 1,311 were built1917–1918.
Developed from the Arab were the inverted V-8 Sunbeam Bedouin, straight six Sunbeam Dyak, W-12 Sunbeam Kaffir and 20 cylinder radial Sunbeam Malay.
The production engine loosely based on the Hispano-Suiza 8 V-8 engines.
In common with many other contemporary engine manufacturers the Arab was re-designed to run inverted and given the name Sunbeam Bedouin. Intended to provide better forward visibility for single-engined aircraft there is no evidence that the Bedouoin was fitted to an aircraft or flew.
A W-12 broad arrow engine using blocks, heads and valve-gear from the Arab, giving 300 hp (224 kW). Bore remained the same at 120 mm (5 in), but with a stroke of 135 mm (5 in).
A straight six extrapolation of the Arab retaining the 120 mm (5 in) stroke and 130 mm (5 in) bore of the Arab, but with only two valves per cylinder as opposed to the three valves on the Arab.
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Type: 8-cylinder, upright, 90 degree Vee engine
Bore: 4.72 in (120 mm)
Stroke: 5.12 in (130 mm)
Displacement: 717.65 cu in (11.76 l)
Length: 43.5 in (1,100 mm)
Width: 31.9 in (810 mm)
Height: 35.5 in (900 mm)
Dry weight: 530 lb (240 kg)
Valvetrain: single overhead camshaft, three poppet valves/cylinder (one inlet, two exhaust)
Fuel system: Single Claudel-Hobson carburettor
Cooling system: Liquid-cooled
Reduction gear: 0.6:1, Left-hand tractor/Right Hand pusher
Power output: 208 hp (155 kW) at 2,000 rpm (takeoff power)
Compression ratio: 5.3:1