Sunbeam Arab

Sunbeam
Company type	Private
Industry	Aero engine manufacturing
Founded	1916
Headquarters	United Kingdom
Products	Aero engines, including the Sunbeam Arab

The Sunbeam Arab was an aero engine developed in Britain during the First World War by Sunbeam.

Design and development

By 1916, the War Office had moved to standardise aero engines around the 200 hp class due to rising demand. The Arab was a water-cooled V-8 configuration, incorporating cast aluminium alloy for its cylinder blocks and heads, along with die-cast aluminium pistons. It featured a bore of , a stroke of , and a total displacement of , delivering a power output of 208 hp at 2,000 rpm.

The engine first ran on a test bench in 1916 and drew inspiration from the Hispano-Suiza V-8 designs, although it presented significant design departures. Following assessment by the Internal Combustion Engine Committee under the Advisory Committee on Aeronautics, Sunbeam secured an initial contract for 1,000 units in March 1917. This procurement aligned with Sir William Weir’s initiative to reduce reliance on skilled labour required for Rolls-Royce Eagle and Falcon engines by utilising cast aluminium blocks to minimise machining complexity. However, the Arab was ordered prior to any flight testing, and persistent vibration problems surfaced during operation that remained unresolved. Despite these issues, orders were increased to 2,000 units by June 1917, alongside an additional 2,160 engines contracted to manufacturers including Austin Motors (1,000), Lanchester Motor Company (300), Napier & Son (300), and Willys Overland (560) in the United States.

Although production was ramped up extensively, the Arab’s ongoing reliability shortcomings restricted its operational deployment. Nearly half of the Bristol Fighter production—then Britain’s foremost two-seat fighter—was placed in storage as plans to equip it with the Arab were abandoned. Ultimately, approximately 2,350 orders were cancelled and outstanding contracts were resolved with the various manufacturers.

The Arab also served as a foundation for multiple derivative engines: the inverted V-8 Sunbeam Bedouin; the straight-six Sunbeam Dyak; the W-12 Sunbeam Kaffir; and the 20-cylinder radial Sunbeam Malay.

Variants

Arab: The primary production model loosely derived from Hispano-Suiza 8 V-8 engines.
Bedouin: An inverted version of the Arab called Sunbeam Bedouin, developed to enhance forward visibility in single-engine aircraft. There is no record of this variant being installed in any aircraft or flown.
Kaffir: A W-12 broad-arrow engine that utilised the Arab’s cylinder blocks, heads, and valve gear, producing . The bore remained at , with a stroke of .
Dyak: A straight-six adaptation of the Arab featuring a stroke of and bore of , equipped with two valves per cylinder rather than three.
Pathan: A diesel-powered evolution of the Dyak designed by Coatalen, delivering at 1,500 rpm. Only prototype models were constructed.
Malay: The Sunbeam Malay was a 20-cylinder radial engine composed of five four-cylinder Arab blocks arranged radially around a central crankshaft. It retained the Arab’s bore and stroke dimensions (), three valves per cylinder, and overhead camshafts. Rated at , this engine did not enter production.

Applications

Information sourced from Brew.

Bibliography

Brew, Alec. Sunbeam Aero-Engines. Shrewsbury: Airlife Publishing, 1998
Ewer, Peter. "William Weir: Architect of Air Power? The First World War Chapter", The International Journal for the History of Engineering & Technology, 2023, pp. 1–19.
Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough: Airlife Publishing, 2003

External links

Sunbeam Overhead Cam Engines: The Arab – Wolverhampton Museum of Industry (archived)
Sunbeam Overhead Cam Engines – Wolverhampton Museum of Industry (archived)