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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 to Ferodo Ltd. regarding brake lining test results, squeak prevention, and the characteristics of different lining materials.

Identifier  ExFiles\Box 141\2\  scan0270
Date  15th March 1939
  
1180?

EXPERIMENTAL DEPARTMENT.

Rm{William Robotham - Chief Engineer}/JBD.{John B. Dixon - Fuel Systems}12/JH.

15th. March, 1939.

Messrs. Ferodo Ltd.,
Chapel-en-le-Frith

For the attention of Mr. Chilton.

Dear Sirs,

We thank you for your letter and note with interest your remarks about the test rig.

From the results you have already obtained it appears that the μ speed curve theory still holds, but that we require a lining giving a definite rising characteristic with increase of speed to prove that this will prevent squeaks. We are obtaining another sample of the Thermoid lining and hope this will give the required results.

The writer would be very interested to pay you another visit when the Thermoid samples are prepared.

It would also be interesting to investigate your RU and RL flexible linings both alone and in conjunction with the BZ material which we have used with a certain amount of success as this combination does appear to minimise the tendency to squeak.

Previous investigators have experienced difficulty in obtaining consistent results when repeating tests with different linings on the same test plate as you are aware and you may find it necessary to do quite a lot of running with one sample before anything like true results are obtained more particularly if the plate surface has become scored and tends to hold particles of the previous lining used.

Incidentally we assume your description which refers to a convex curve is one in which the μ falls with speed.

We are despatching the Thermoid lining and if you
  
  


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