Ask a motorcycle historian to name a frame-maker who used triangulation to revolutionise handling and the reply will probably be ‘Lino Tonti,’ but almost 60 years before the Italian designer was positioning tubes around Moto Guzzi’s V7 engine, a student motor engineer from Ledbury had applied the very same principles in his workshop.
Like many innovators, Frank Willoughby Cotton’s design was one born out of necessity, with a touch of ambition thrown in for good measure. A keen trials and hillclimb rider, he could see – and no doubt feel – the limitations of the diamond-shaped bicycle-type frames of early 1900s machines. More importantly, Cotton also recognised where their strength lay; in the triangles that formed the basic design.
Cotton set about designing a stronger and more rigid frame made up entirely of straight tubes and with triangulated structures as its basis. Four straight tubes ran from the top and bottom of the steering head to the rear wheel spindle, while additional tubes connected the steering head to the engine and gearbox to the rear wheel; forming triangles on both the horizontal and vertical planes. The ingenious design kept the tubes under compression and tension, all but eliminating flex, reducing the likelihood of cracking due to fatigue and keeping the wheels perfectly aligned. It provided strength without a weight pay-off, significantly lowered the machine’s centre of gravity and increased stability – the engine could be carried lower and further forward – as well as providing a much-improved riding position, and fuel tank mounting options. It was also cost-effective to produce, as it used only straight tubing.
Extraordinary circumstances
Bill – as he was more commonly known – applied for his patent in July
