Norton Isolastic frame

A Norton Commando

In September 1967^[1] the legendary Featherbed frame was replaced by an Isolastic frame Norton Motorcycles for use in the Norton Commando.

In an attempt to reduce the problem of engine vibration being transmitted through the frame, as the capacity of the motorcycle engines increased to 750cc with the Norton Atlas, Norton decided to look at changes to the Featherbed frame and the 1969 Norton Commando was the result. The innovative isolastic frame derived from the Featherbed made it much smoother through the use of rubber bushings to isolate the engine and swingarm from the frame, forks, and rider. As the rubber bushings wore, however, the bike became prone to fishtailing in high-speed turns.^[2] Earlier models therefore required careful adjustment of the clearance between frame and mounts using shims.

The later Mark III Commandos had a threaded adjuster that made this easier. The swinging arm was also mounted to the cradle to prevent lateral twisting causing misalignment of the drive sprockets leading to rapid chain wear and stress. It was a rushed design but despite steering head fractures on 1968 and 1969 models the Commando was a success.^[3]

References

1. ^ Norton By Mick Woollett. 2004.
2. ^ Bacon, Roy (1990). Norton Commando. Niton Publishing. ISBN 1-85648-310-X. 
3. ^ "Norton Commando — Isolastic Mounting System". http://ensanian.com/AE/NortonIsolastic.htm. Retrieved 2009-01-09.