The creation of the modern motorcycle chassis
º The modern motorcycle chassis was born during an illegal road-test session on the Isle of Man on a freezing-cold day in January 1950. Legendary Norton team manager and development engineer Joe Craig had arranged a test between the factory’s existing single-cylinder 500cc grand prix bike and a Norton with a revolutionary fully-sprung chassis created by Northern Irish bon Rex Mccandless.
The test took place on open roads around Kate’s Cottage. Riders for the day were Norton’s new signing Geoff Duke and team-mate Artie Bell. For the first run Craig put Duke on the standard Norton, with its bulky frame, constructed by joining tubes via steel lugs, and rudimentary plunger rear suspension, with limited travel.
Bell rode the bike with the Mccandless chassis. There’s no doubt
Duke was the better rider, but each time the pair raced through Kate’s Cottage it was Bell who came out in front. The new chassis steered and handled so much better that Duke announced, ‘this new machine sets a new standard in road-holding’.
By the start of the 1950 grand prix season Norton’s full stable of works machines had been equipped with the Mccandless chassis, nicknamed Featherbed for its smooth, comfy ride. Duke led the 500 championship and would’ve won the title but for two tyre failures. The Mccandless chassis – UK patent number 664,667 – was so good it became the blueprint for motorcycle chassis for the next three decades. So what was so clever about it? Firstly, Mccandless’ fabricators developed their welding skills to the point that they could create robust and reliable joints, so the entire frame could be welded together, rather than using lugs which made the frame heavy and bulky. Bending and welding tubes allowed Mccandless to build a double loop frame, which created a cradle for the engine and a wide base for the swingarm (or swinging fork, in those days). This design positioned the swingarm pivot close to the gearbox sprocket, allowing greater suspension travel and softer springing.
Mccandless was also way ahead in the suspension game, initially building his own hydraulic shocks from Citroën car dampers. In 1950 he patented shock absorbers with remote reservoirs, patent number 699,809.
The final factor was a change in balance. At that time most engineers put the engine and rider as far back as they could to improve rear traction. Mccandless moved them forward to put more load on the front tyre and thereby improve turning. The double-loop tubular-steel frame remained the benchmark for road bikes and race bikes until Spanish engineer Antonio Cobas fabricated the first aluminium beam frame in 1982.