KNOW YOUR SUNBEAMS
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'FLAT TANK' MODELS : 1912 - 1928
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Introduction John Marston Ltd, manufacturer of Sunbeam tricycles and bicycles from 1887 and motor cars from 1899, commenced motorcycle production relatively late in 1912. This is quite surprising given the company was based in Wolverhampton, one of the early centres for the UK's motorcycle industry. It is reckoned John Marston himself was not taken with the idea following a fatality whilst testing a prototype in the early 1900s. However, by 1912 when John Marston decided to commence production, one of the major technical disincentives to ownership - the lack of a clutch - had been overcome. Sunbeam also missed the era of belt driven transmission. From the start it employed a chain drive enclosed in its famous 'Little Oil Bath' derived from its tried and tested bicycle technology.
PHOTO The early machines, 1912-14 The first Sunbeam motorcycle appeared in 1912. It was a 2¾ horse power (h.p.), two-speed machine of 349cc capacity. John Marston had commissioned Harry Stevens, of AJS Motor Cycles, to design the motorcycle engine. John Greenwood, formerly of Rover and JAP, was taken on by Marston to incorporate Stevens' engine into the first Sunbeam motorcycle. This remained in production for three years until 1914. This was followed in 1913 by a proprietary v-twin machine with a 6 h.p. JAP engine of 770cc capacity. This was undoubtedly a consequence of Greenwood's previous work at JAP and Marston's desire to provide a heavy-weight, sidecar-pulling machine. The 6 h.p. model remained in production into the early part of the First World War in 1915. John Greenwood designed a 3½ h.p. model for the 1914 season, available from late 1913. It had a 499cc engine based on the conventional 'square' dimensions of the time: 85mm bore and 88mm stroke. The first engine designed by Greenwood for Marston, he went on to design all but one of the subsequent Sunbeam engines. As a sporting T.T. model, it scooped the Manufacturers' Award at the 1914 T.T.. 3½ hp Standard, Model 3, 1915-26 With a number of changes, notably a chain-driven magneto, the 3½ h.p. model became a 'General Service' machine for the War Department during the First World War. With further changes and refinements this 499cc model remained in continuous production into the post-war years until 1926. It was designated the 'Model 3' when Marston introduced model numbers in 1924. A sporting version of this model won the first post-war Senior T.T. in 1920. Consequently, Sporting (T.T. model) and Semi-Sporting versions of the 'Standard' were produced in the early 1920s. The V-twins, 1915-23 Marston's original 6 h.p. JAP v-twin model continued into the early years of the First World War until 1915. However, difficulty in sourcing JAP engines led to use of a 6 h.p. AKD engine in 1915-16, and Swiss 8 h.p. MAG engines in 1916. A JAP-engined machine was reintroduced towards the end of the war. This 8 h.p. model had a larger 996cc capacity engine and continued in production until 1923. It was designed as a heavy-weight machine to pull a sidecar. During the war, a medium-weight 5 h.p. v-twin Sunbeam was designed for the Russian Army. Unlike Marston's other v-twins this was not designed to pull a sidecar but for use as a solo machine. It was not brought into general production. 4 h.p. French Military Model, 1916-18 Produced to French Army specification, this is the only Sunbeam to have a belt drive. The gearbox was unique to this machine too, as transmission did not cross from the drive to the timing-side of the machine, a trait common to all other Sunbeams until the late 1930s when a bought-in gearbox was introduced. The engine retained the standard bore of 85mm but had a longer 96mm stroke, giving a capacity of some 550cc. It was based on pre-war development work by George Dance but was not continued post-war. The Longstroke, Model 6, Lion, 1922-39 The 1921 French Grand Prix proved a successful testing ground for Marston's prototype, long-stroked engine of 492cc. It had a 77mm bore by 105.5 mm stroke. The 'Longstroke' model went into production the following year, winning the Senior T.T. It was the last side-valve engined motorcycle to do so. The Sunbeam Longstroke was the fastest production, single cylinder, side-valve motorcycle in its day. The model stayed in production for the life of the company and the subsequent AMC take-over in late 1937. It underwent many stylistic changes; notably from flat tank to saddle tank in 1929. Known as the Model 6 prior to ICI's takeover of the company in 1929, it was marketed as 'the Lion' during the 1930s - the tank emblazoned with ICI's trademark lion emblem. 4½ hp, Model 7, 7A and 600 Lion,1922-40 A combination of the Longstroke's 105.5 mm stroke and the Standard model's 85 mm bore produced a larger engined 596cc motorcycle intended for side car work. From 1924 it was designated the 'Model 7'. This replaced the JAP-engined v-twin in the company's model range. Famously, the Model 7 Sunbeam continued into the early 1930s as a flat tank machine, well after the universal change to saddle tank motorcycle design in the late 1920s. In 1932 it was replaced by the 598cc version of the saddle tank Lion, known as the 'Model 7A', and later simply as the '600cc Lion'. 500cc Light Solo, Model 5, 1923-26 A mid-1920s' sporting machine for the fan of Marston's original 'square-stroke' engine (85 x 88 mm). It was produced by combining the Longstroke's lighter sporting frame, gearbox and cycle parts with the Standard's shorter stroked engine. When production of the square-stroked engine ceased in 1926 the 'Model 5' name was used to denote the touring version of the Model 6 Longstroke from 1927-30. This had lower gearing. Both models were replaced by the Lion in 1931. Models 1 and 2, 1923-30 In 1923 a 350cc (2¾ hp) side-valve machine was reintroduced to the Sunbeam range, this size of machine having been discontinued in 1915. It was available in road-going or sporting trim, with differing gear ratios and equipment to suit. The engine had a narrower bore and longer stroke than Stevens' original 350cc engine, last produced in 1914. In 1929 the models were restyled with saddle tank design. In this guise it was produced for just two years from 1929 to 1930. Thereafter Marston produced only OHV machines in the 350cc class. The 600cc Model 4 Deluxe, 1924-26 A short-lived model, introduced for the 1924 season by combining the 4½ h.p. model's 596cc engine with the cycle parts of the 3½ h.p. Standard model. The over-head valve (OHV) machines and an odd prototype over-head camshaft (OHC) model called the 'crocodile' The web site currently focuses on Sunbeam's side-valve machines, details of the OHV machines will be added at some future date ... ACKNOWLEDGEMENTS In putting this list together, I have relied a great deal on the following:- John Marston Ltd, various Sunbeam Motor Cycle Catalogues, Manuals and Spare Parts Lists Motor Cycling and The Motor Cycle magazines from the period AMC catalogues from their ownership of Sunbeam from 1937. Robert Cordon Champ, 1980, The Sunbeam Motorcycle, Haynes Publishing Robert Cordon Champ, 1989, The Illustrated History of Sunbeam Bicycles and Motorcycles, Haynes Publishing Roy Bacon, 1986, British Motorcycles of the 30's, Osprey Publishing The Wolverhampton History and Heritage Society's web site. Richard Rosenthal's articles in the Classic Motor Cycle magazines of May, June and July 2008. ... my thanks! |
THE 'SADDLE TANK' MODELS : 1929-1940
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