The Williamson Motor Co. Ltd., 26 Moor Street, Coventry.
Williamson were motorcycles produced from 1912 to 1920 by William "Billy" Williamson after he left the board of
Rex, aided by his brother Harry.
1912 The first machine made its debut and offered power with silence, and no vibration, courtesy of its 8hp 946cc flat-twin water-cooled engine, made for them by Douglas of Bristol with whom they had an arrangement. As with their their stationary engine range, on which it was based, it had a starting crank handle like that of a car. It was a typical Douglas HO twin engine with side valves, gear-driven magneto and was positioned low in a long frame to drive a two-speed Douglas gearbox with all-chain drive.
Horizontally Opposed Twin
Examples include BMW, Zundapp and Douglas HO Twins have conrods running on a common crank, with one on the exhaust stroke and the other on inlet.
1913 An air-cooled version of the horizontally opposed longitudinal twin was added, but it did not sell as well as the quieter machine and had a tendency to over-heat. It did, however, continue to be offered as an option. Most models sold were water-cooled and used for sidecars.
1916 Production continued until that year, and then stopped until after the War.
1919 Late in the year they returned with the air-cooled flat-twin and a new model with the 771cc sv JAP V-twin engine and three-speed Sturmey-Archer gearbox with all chain drive.
1920 Only the V-twin remained, this being sold with the sidecar as a complete combination. It was their final year of production.
The company also built automobiles from 1913.
Notes. 1. One source says that the 946cc Douglas engines were made "exclusively" for Williamson. Another says they were part of the industrial stationary engine range.
It is also mentioned that their was a family connection between Williamson and Douglas.