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 concerning the performance of 40/50 HP chassis brake liners.
| Identifier | ExFiles\Box 26\4\ Scan144 | |
| Date | 26th October 1921 | |
| COPY OF LETTER RECEIVED FROM:- FERODO LIMITED, SOVEREIGN MILLS, CHAPEL-EN-LE-FRITH. SALES DEPT. Ref: FJF/DHL. Your Ref: Wd{Mr Wood/Mr Whitehead}3/NJ.181021. 26th October 1921. (Wednesday) Messrs Rolls Royce Ltd., Nightingale Road, DERBY. Dear Sirs, re:- 40/50 HP. CHASSIS BRAKE LINERS. In further reply to your letter of the 18th inst., on above subject and reference, we would like you to know that we appreciate the opportunity of reading a copy of your Mr. Bailey's reply to ours of the 13th inst., We quite accept, as established by your goodselves, that more pressure is required to produce a given stopping effect with a new car than with the same machine after a fair amount of running, but we are at loss in giving a definite reason, and can not subscribe to your suggestions that the polish, either of the linings or brake drum surface, contributes to the falling off in efficiency to any material extent - but to be consistent, we must say that within a very short period of use no difference in the surface condition of the lining should make any material difference in the retarding effect of the brake when pressures are equal. When friction linings make good contact over their whole surface, the effect of rubbing rapidly produces a polished condition, and parts that are not polished are not doing any work. It may arise that more resistance is actually obtained from lining that is not engaging over its entire surface, than from one that presents a larger area of contact. The actual position of the points in contact in relation to the brake fulcrum must also make for differences, but we can hardly imagine anything so variable as to require twice the amount of pressure more at one period of use than another. Certainly the area of contact may be one of the contributing causes to the effect you have described, but when the whole area of the lining is brought down to a smooth level surface, i.e. thoroughly bedded down, our opinion is, that in this condition the braking effort from the lining itself is constant for any given pressure, and that the matter of the degree of polish on the metal parts does not effect its frictional value to any appreciable extent. (CONT'D) R.R. 199 (10M) (SD676 19-7-17) MP18086 | ||