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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).
Translated article from 'L'Auto' discussing progress and techniques in automobile braking.

Identifier  ExFiles\Box 146\2\  scan0082
Date  25th January 1937
  
1029
TRANSLATION
from
L'Auto January 25, 1937.

For Better Braking.

The use of lead for linings constitutes considerable Progress in Braking Technique.

Some ill-natured folk have unfortunately misrepresented the article by Charles Faroux, which we recently published. The subject discussed is sufficiently important for us to reprint it.

The question of brakes has always interested us. It is in fact, of the greatest importance.

How many times during the past twenty years have we not had to admit that the braking technique of the automobile has not kept pace with the development of, say, the engine--- or the pneumatic tyre.

Henri Perrot, an industrious and intelligent man, and one who is, in France, the ultimate authority on all questions relating to brakes, said one day to Henri Petit: "Your last criticism, if harsh, has, at any rate, startled us. Nevertheless you are definitely right when you tell us our four rules. We brake specialists have to thank you. You force us to work and produce still better results."

So these specialists have contrived to work and work well.

At the end of 1934, balanced cam action, them quite recently, automatic compensation, have improved brakes to an extraordinary degree. We have proved it at leisure.

Now a further and no less important development has come to light. I have known, for two or three years past, that the subject was being studied. The most serious foreign patents were made the subjects of protracted discussions, and finally, were conceded. To-day this development is in production. Already it is being sold.

Quite simply, this development is the introduction of Lead into the texture of the asbestos linings by whose friction on the drum-roms automobile braking efficiency is achieved.

Linings themselves have made great strides. The laboratories of the various great firms have produced astonishing results. To appreciate fully the numerous difficulties and problems which have raised their heads and have, each in turn, been overcome, one ought really to have been present in the laboratories and watched the testing machines doing their job.

One of the most important problems has not yet been solved: the liaison between the oily yet nevertheless powerful metal-asbestos lining and the steel drum, whatever the speed variations of the latter may be

This requires explanation: Let us suppose that we operate the brake with a constant effort. A certain amount of effort is necessary to put the brake itself into action. This effort provides a coefficient of friction at starting: the coefficient of Static friction.

The relative movement of the drum and shoes continuing one proceeds to make use of the coefficient of friction between
  
  


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