by R.M. Clarke
The engine of the Norton Commando was based on Bert Hopwood's original 497cc design which provided the motive power in the company's first vertical twin.
Hopwood had joined Norton Motors in the late 1940s after serving for many years as Edward Turner's assistant when he was employed by Triumph.
Aware of what he considered to be several weaknesses inherent in the Triumph twin engine, his own design incorporated means by which he believed they could be overcome successfully.
The mechanical balance of a vertical twin engine in which the pistons rise and fall together is similar to that of a single cylinder engine. However, as the power impulses occur once each revolution they are only half that of a single cylinder engine of similar capacity and the engine runs more smoothly.
As Norton Motors would find out, as the capacity of the engine was increased to 600cc, 650cc and then 750cc, vibration became more of a problem. As a result much of the advantage in making a high performance model, such as the 745cc Atlas, is lost and it becomes a less pleasant machine to ride.
The opportunity for a complete rethink occurred after the AMC Group, Norton's owner at the time, collapsed during 1966. The take-over by Manganese Bronze Holdings that followed, resulted in a new Norton development team who utilised the old Atlas engine in a new model. Their approach to overcome the vibration problem was unique. They isolated the engine, gearbox and bearing of the swinging arm rear fork from the frame by mounting the assembly in rubber bushes. Their patented Isolastic suspension really worked too, even if its adjustment was critical.
As a direct result the new Norton Commando made its debut at the 1967 Motor Cycle Show, to win Motor Cycle News Machine of the Year for five successive years and become Britain's first Superbike. The Commando continued in production until late 1977, by which time the engine had been increased in capacity to 828cc and an electric starter fitted.
Hopwood's engine had stood the test of time for almost 30 years. Included are road tests, new model intros, history, technical & performance data plus an engine rebuild & buyers guide.
Brooklands Books Ltd "Road Test" books provide a wide range and collection of road tests, comparison tests, new model introductions, long term tests, and other articles taken from the world's leading motoring magazines. The Ultimate Portfolio series is the most comprehensive, and usually contain 208 - 220 pages with 400 - 450 illustrations.
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