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  Sunbeam 350hp V12
 

  Article Image gallery (20) 1 Specifications Video (1)  
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Country of origin:Great Britain
Produced in:1920
Numbers built:1
Author:Wouter Melissen
Last updated:April 10, 2015
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Click here to download printer friendly versionDuring the Great War, Sunbeam and many other automobile manufacturers switched to building massive engines for warplanes and airships. After the armistice, the lessons learned were applied to build some truly spectacular and hugely powerful racing cars and record breakers. One of the most famous of these was the Sunbeam 350hp, which was conceived by engineer and racing team manager Louis Coatalen and first raced at Brooklands in 1920.

Coatalen did not simply create the 350hp Sunbeam by strapping a surplus engine onto a rolling chassis. In fact, the V12 was an enlarged but simplified version of the Manitou type engine developed for Naval seaplanes. In its original guise, the engine featured twin overhead camshafts and four valves per cylinder. It was ready right at the end of the war and was only ever fitted to a single experimental airplane. The V12 produced quite a bit of vibrations and Sunbeam did not have the time and resources to further develop the engine.

In 1919 Coatalen redesigned the engine to make it suitable for use in a frame. Simpler heads were fitted with a single overhead camshaft and a single intake and twin exhaust valves. An enlarged bore of 120 mm increased the displaced to a staggering 18.3 litres. A most unusual feature of Coatalen's design was the use of articulated connecting rods. In this design one of the connecting rods acted indirectly on the crankshaft through a journal on the opposite connecting rod. While this allowed for a shorter crankshaft to be used, it also meant the two banks had different strokes (135 mm and 142 mm), which was a main cause of the vibrations.

The V12 was created by mounting four blocks on a common crankcase at a 60° angle. Breathing through a pair of Claudel-Hobson carburettors, the massive engine produced 355 bhp at 2,300 rpm. The V12 was mated to a four-speed preselector gearbox and mounted in a conventional ladder frame chassis. Suspension was by rigid axles and semi-elliptic leaf springs on all four corners. The foot brake acted directly on the transmission and an additional hand brake operated the drums on the rear axle. The 350hp was clothed in an aluminium single seater body with the radiator cowl and the tail painted British Racing Green.

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  Article Image gallery (20) 1 Specifications Video (1)