Rolls-Royce Archives
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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Technical discussion on vehicle weight distribution, radius of gyration, and suspension behaviour over uneven surfaces.

Identifier  ExFiles\Box 24\1\  Scan042
Date  12th December 1931 guessed
  
8.

Now my contention is that in a modern car the weight should be so distributed along its length that if A and B are the distances of front and rear axles from centre of gravity and K is the radius of gyration about the centre of gravity that this same relation holds and thus if the car is subjected to force or impact in the plane of one axle whether vertically or horizontally, there will be no corresponding reaction in the plane of the other. A considerable improvement in both comfort and in freedom from skidding on greasy roads must inevitably follow if this principle is adopted as a feature of design.

Consider, for instance, the behaviour of an orthodox car for which the value of AB is not equal to K² but usually to something between 1.5K² and 1.7K². When the front wheels passed over a bump or inequality they were we will say, forced upwards compressing the front springs and rotating the body of the car as a whole about some point much nearer the centre of gravity than the plane of the rear wheels. Thus the part of the frame immediately over the rear wheels swings downwards compressing the rear springs. At the same time the rear wheels have themselves reached this same inequality and the rear wheels are themselves subjected to a similar upwards reaction. It seems clear that the effect is to intensify the action of every inequality of the road surface on the rear wheels. It is as if every time the front wheels meet a bump in the road the rear wheels are pressed down to meet the same bump with still greater intensity while every time the front wheels drop into a hole the rear wheels are lifted so that they will drop into the same hole with still greater force.

Owing to the action of the springs there will of course be a time lag between the effects. The reaction on the front wheels compressing the front springs react on frame and body rotating the latter and in turn compressing the rear springs
  
  


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