THE FLAT TANKS 1913-1928
 

Introduction

John Marston Ltd,  manufacturer of  Sunbeam tricycles and bicycles from 1887 and motor cars from 1899, commenced motor cycle production relatively late in 1912. That's quite surprising. It's reckoned John Marston himself was not taken with the idea following a fatality whilst testing an early prototype.

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 Little Oil Bath Chain Case' of the SUN*BEAM bicycle (Black Country Living Museum)

The early machines, 1912-14

Harry Stevens, of AJS motor cycles, designed the first 2¾ horse power (hp) engine for John Marston for the 1912 season. John Greenwood, formerly of Rover and JAP incorporated this into the first Sunbeam motor cycle.

This was followed in 1913 by a 3½ hp model designed by John Greenwood who went on to design all but one of the subsequent Sunbeam engines.

A proprietary v-twin machine with a 6 hp JAP engine was also produced in 1913. JAP engined machines were built until the early 1920s, with the exception of the use of AKD engines in 1915, and MAG engines in 1916. The v-twin Sunbeams with their 'bought in' engines have an outlandish reputation with 'Beamers, being somewhat of a rarity.

The 3½ hp Standard, 1915-26

As a sporting TT model, this machine scooped the 1914 TT Manufacturer's Award. It became the standard machine for War Department (WD) production and continued into the post-war years of the 1920s.

The 500c Longstroke, 1922-39

The 1921 French Grand Prix proved the testing ground for the prototype long-stroked engine. The model stayed in production for the life of the company and the subsequent AMC take-over, undergoing many stylistic changes; notably from flat tank to saddle tank in 1930. Known as the Model 6, prior to ICI's takeover of the company in 1929, it became 'the Lion' during the 1930s - the tank emblazoned with ICI's trademark lion emblem.

Model 7, 1922-40

A combination of the Longstroke's 105.5mm stroke and the short-stroke's 85mm bore produced a larger engined 600cc engine intended for side car work. It continued into the early 1930s as a flat tank model, to be replaced by the 600cc version of the saddle tank Lion in 1932.

Model 5 'short-stroke', 1923-26

A sporting machine for the fan of the 'short-stroke' engine was produced by taking the Longstroke's frame and using the Standard's shorter stroke engine. When production of the short-stroke engine ceased in 1926, from 1927-30 the 'Model 5' name was used for the touring version of the Model 6 Longstroke.

Models 1 and 2, 1923-30

In 1923 a 350cc (2¾ hp) side-valve machine was reintroduced. It had a narrower bore and longer stroke than Stevens's original 350cc engine, last produced in 1914. In 1929 it was restyled as a saddle tanked model in which guise it was produced for just two years, 1929-30.

The overhead valve machines and an odd prototype overhead cam 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 excellent articles in the Classic Motor Cycle magazines of May, June and July 2008.

... my thanks!

THE SADDLE TANKS 1929-1940