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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).
Letter from Ferodo Limited discussing the coefficient of friction of their bonded asbestos materials and arranging a demonstration.

Identifier  ExFiles\Box 26\4\  Scan216
Date  5th January 1924
  
From FERODO LIMITED. 5/1/24 Sheet No. - 2 -

Messrs Rolls-Royce Limited.

very infrequent except where the unit pressure is high and the metal of the drums very soft.

In regard to coefficient of friction of, say, Ferodo Bonded Asbestos in our tests we always find that increasing the temperature increases the coefficient of friction. Increase of velocity also increases the coefficient, but the increase may quite as justly be attributed to increase of the temperature of the immediate contacting surface of the lining as the increase of speed, for though the metal of the drum may not be higher than 120° temperature we have frequently observed certain materials glow at the edges - cast iron, for instance, can be made red-hot running against a drum with a temperature not higher than 180° Fahr.

We very much appreciate your suggestion of a visit. We shall be pleased for you to come over any day next week after Tuesday, as the writer will be away on that day. We can demonstrate the coefficient of frictions of our materials as fully as you desire. To make the occasion a little more interesting we should like to have fixed one of your drums on our machine, but even if you send us a drum with shoes and operating cam, we very much doubt if we could get it rigged up in time for next week. However, we could fix up a standard type of pressed steel drum, and can demonstrate that no squeaking can arise with our material. If Wednesday morning next will be convenient to you, it will be equally so to us, and we shall be very pleased at the opportunity which we have long looked for from any member or members of your Technical Staff.

By another post we will send you a chart shewing the coefficient of friction of our material from zero slip to 7000 feet, and we think we can confirm the figures at any time.

Yours faithfully,
FERODO LIMITED

Chief Engineer
  
  


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