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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).
Page discussing the distribution of weight and the physics of a rigid body, focusing on the centre of percussion and rotation.

Identifier  ExFiles\Box 24\1\  Scan041
Date  12th December 1931 guessed
  
7.

of the centre of gravity from the point of view of minimum deviation is about one third of the length of the wheelbase in front of the rear wheels.

The third condition in which I believe modification of existing ideas is desirable relates to the distribution of weight along the length of the car.

If any free rigid body is subjected to a transverse force at some point along its length near one end, then as every engineer knows, there will be some other point towards the other end of the body at which, if the body is held there, there will be no reaction on the support. If the latter point is called the centre of rotation the first will be the corresponding centre of percussion. Further the two points are conjugate, that is if the body is held at the first point then the second becomes the corresponding centre of percussion.

Mathematically, if the body is subjected to a force acting at the first two points two effects occur simultaneously. The body moves as a whole as if the force acted at the centre of gravity and secondly the whole body has an angular rotation about the centre of gravity under the action of the moment of the force about the centre of gravity. At the second point the lateral movement of the body is exactly equal and opposite to that due to rotation and thus this particular point remains stationary in space. This if the body is acted upon by a force at the first point it rotates as a whole about the second point and if hinged at the latter there will be no reaction at the hinge.

If A and B are the distances of centre of percussion and centre of rotation respectively from the centre of gravity and K the radius of gyration of the body then A and B are connected by the relation AB/K^2=1.
  
  


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