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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 discussing issues and requirements for brake servo lining materials.

Identifier  ExFiles\Box 141\3\  scan0215
Date  28th September 1933
  
X719.

Experimental Dept.

Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}S/KT.

Sept 28th 1933.

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

For the attention of Mr. Field.

Dear Sirs,

We thank you for your letter of the 27th inst. You will realise that what we are trying to find is a servo lining that will give a consistent value of µ. RAD.13 varies between large amounts. FF.239 gives almost no output until it has been roasted, but then unfortunately squeaks when µ has risen to .7 which value, however it maintains. RAD.13 also seems to be affected by the least trace of oil, when being handled by dirty hands.

If your S.3914 is not thus affected and gives a µ of .3 without prolonged running in, we could alter our cam angle and have consistent and efficient brakes. Perhaps you would send us a sample to try.

We enclose a pair of linings of "Cotton A" that were standard on our cars before RAD.13. Our only objection to them was mechanical strength. They frayed at the edges and sometimes disintegrated altogether. They provide, however, a consistent and efficient servo, require no running in, and are not affected by traces of oil.

If you could make us a lining of this type with a suitable edge, it might perhaps be the solution of our troubles.

Yours faithfully,

FOR ROLLS-ROYCE LIMITED.
  
  


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