I'm reading the fascinating autobiography of Alex Moulton. If you have even a passing interest in engineering it's worth a read, but what grabbed my attention was his description of modifying his own Vincent Comet with Mouton-designed 'shear' suspension. The device was favourably appraised in 'Motorcycling' dated 20th November 1947 and is described thus:
"The original Vincent HRD spring frame has been replaced by a single massive u-shaped tubular rear fork member of 1 3/4" OD by 14 swg. This accommodates the wheel spindle at its open end and has, welded to the forward portions of the loop, gusseted plates. Each of these plates is secured by six Allen screws to a central tubular bearing, joining them both and acting as a pivotal point for sprung rear wheel movement. The appearance of the Spencer Moulton prototype 'heel' suggests undue weightiness; in practice, however, the Spencer Moulton rear assembly is some 6lb lighter than that of the standard 'Comet', and it is estimated that still further saving can be affected on production jobs. Just as the elasticity of rubber is considerable on being stretched or compressed lightly, so this torsional shear of Mr Moulton's prototype reacts to finger pressure on the 'Comet' saddle; perceptible up and down movement even in sympathy with engine tick-over vibration is noticeable. With the rider mounted the deflection is 2 1/2 inches, leaving another 1 1/2 inches movement for absorption of main road shocks before the rear fork member abuts against a special rubber stop beneath the saddle. This stop, by its spongy action, allows another 1 inch movement for absorbing really severe impact. A total rear wheel arc-swing of 5 inches is provided for in this way and gives a perfectly soft ride at speeds up to 75mph."
The article is accompanied by a patent drawing.
Doubtless this topic has been covered in the pages of MPH but although I'd vaguely heard of it I never knew the details. Moulton was a brilliant designer most famous for his Mini suspension and his bicycles, and yet he did much more. He was an active motorcyclist too often dashing off to the South of France on his BMW - and we know that at leat in 1947 he was a Vincent owner.
"The original Vincent HRD spring frame has been replaced by a single massive u-shaped tubular rear fork member of 1 3/4" OD by 14 swg. This accommodates the wheel spindle at its open end and has, welded to the forward portions of the loop, gusseted plates. Each of these plates is secured by six Allen screws to a central tubular bearing, joining them both and acting as a pivotal point for sprung rear wheel movement. The appearance of the Spencer Moulton prototype 'heel' suggests undue weightiness; in practice, however, the Spencer Moulton rear assembly is some 6lb lighter than that of the standard 'Comet', and it is estimated that still further saving can be affected on production jobs. Just as the elasticity of rubber is considerable on being stretched or compressed lightly, so this torsional shear of Mr Moulton's prototype reacts to finger pressure on the 'Comet' saddle; perceptible up and down movement even in sympathy with engine tick-over vibration is noticeable. With the rider mounted the deflection is 2 1/2 inches, leaving another 1 1/2 inches movement for absorption of main road shocks before the rear fork member abuts against a special rubber stop beneath the saddle. This stop, by its spongy action, allows another 1 inch movement for absorbing really severe impact. A total rear wheel arc-swing of 5 inches is provided for in this way and gives a perfectly soft ride at speeds up to 75mph."
The article is accompanied by a patent drawing.
Doubtless this topic has been covered in the pages of MPH but although I'd vaguely heard of it I never knew the details. Moulton was a brilliant designer most famous for his Mini suspension and his bicycles, and yet he did much more. He was an active motorcyclist too often dashing off to the South of France on his BMW - and we know that at leat in 1947 he was a Vincent owner.
