FLAT TWINS
It is a common misconception that Douglas were the only company to use the fore and aft flat twin engine layout. Douglas were by far the biggest user of this engine layout, building them from 1907 until the outbreak of WW2, but they were not alone.
William and Edwin Douglas got into the motorcycle business by accident, when a company they supplied castings too, Light Motors, went into receivership. Light Motors were probably the pioneers of fore and aft flat twins. The Douglas brothers spotted an opportunity in carrying on production of these smooth, nimble, sturdy, low vibration machines, which performed well, and seemed to sell. Their appeal was enhanced with success on the Isle of Man, European race tracks, dirt tracks, and as Dispatch Rider mounts in WW1. So it is not surprising that a number of other makes tried fore and aft flat twin configuration: Brough (not Superior), D-Rad, Victoria, Wilkinson, Indian (model O) and Harley Davidson (model W & XA) to name a few. Perhaps the most esoteric of them all was the Quirk’s Mona, the first truly indigenous Australian machine.
Within this article we’ll examine one of the more obscure fore and aft flat twins to be produced, the 1916 ABC, its better known sibling the Sopwith ABC, and the unique Australian machine the Quirk’s Mona.
1916 ABC
The 1916 ABC was designed and produced by Granville Bradshaw, a talented engineer and a keen motorcyclist. Granville came into contact with the motorcycle racing community when working on aircraft at Brooklands before WW1. He became friends with an Australian flyer, and Douglas works rider, Les Bailey. In November 1912 Granville extensively modified one of Les’ machines, adding steel cylinders, overhead valves and a three throw crankshaft. The outer throws of the crankshaft drove one piston whilst the middle throw moved the other piston (designed to reduce vibration and keep the cylinders on a common axis). The modified machine set the 350cc flying kilometre record at 72.63mph at Brooklands.
In 1913, based on his experience with Les Bailey’s record-breaking Douglas, Granville designed the ABC motorcycle. He produced three versions of the machine; a standard model and two racing models, the TT model and a Brooklands model. The standard machine had a 2 throw crank and exhaust over inlet valves gear, while the racers had 3 throw cranks and overhead valves. Excellent results in a number of 1914 race meetings, and the first 500cc motorcycle to exceed 80mph at Brooklands, had orders flowing in but production was overtaken by the growing demands for munitions and specialist equipment, for British forces in WW1.
A large batch of standard machines with sidecar was produced for the British Army in Egypt but finished up at the bottom of the Mediterranean after their ship was torpedoed. The engine continued to be used throughout WW1, powering small generators, trench pumps and an observation balloon inflator, all designed by the fertile mind of Bradshaw. The engine was also used by Brough and Zenith motorcycles. The motorcycle is very different to ►