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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 oil absorption in clutch discs and the performance of servo linings.

Identifier  ExFiles\Box 141\3\  scan0209
Date  1st September 1933
  
X719

Experimental Dept.

Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}2/KT.

Sept. 1st 1933.

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

For the attention of Mr.Field:

Dear Sirs,

We thank you for your FJF/WAC of the 30th ult.

We submitted the oil extracted from the two clutch discs to our chemist, who says the sample contained 65% mineral oil, the rest being, he thinks, Tung oil, probably from the bonding of the material. We are of the opinion that the mineral oil must be present due to the fabrics absorbing oil vapour and should be glad to have your views on this. We have several clutches lined with RAD.13 and have experienced no clutch slip with these. Would you consider the RAD.13 a better material from this point of view, or can you suggest any other material that would not be affected by oil vapour.

We have fitted the FF.239.A servo linings to a chassis and measured the output and input. Until the lining had been raised to a very high temperature, the co-efficient of friction was exceedingly low but rose to about .5 While cooling down a figure of over .7 was obtained. When cold again it was found to be about just over .4 .

Unfortunately during a road test the 3 staples tore out of the fabrics, entirely ruining it. We hope, therefore, you will send a few more discs as soon as possible, to try in a servo we have in which the fabrics are spigotted both inside and outside and no staples are used.

Yours faithfully,

FOR ROLLS ROYCE LIMITED.
  
  


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