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 theory of brake lining friction, μ speed curves, and brake squeal.
| Identifier | ExFiles\Box 140\4\ scan0150 | |
| Date | 24th January 1938 | |
| All Communications to be addressed to the Company. FERODO LIMITED TELEPHONE: 250 CHAPEL-EN-LE-FRITH (6 LINES) TELEGRAMS: FRICTION, PHONE, CHAPEL-EN-LE-FRITH. FERODO BRAKE & CLUTCH LININGS REGO. TRADE MARK. CHAPEL-EN-LE-FRITH, STOCKPORT, ENGLAND. CODES: WESTERN UNION FIVE LETTER EDITION, BENTLEY'S COMPLETE & 2ND PHRASE, MARCONI INTERNATIONAL, LIEBER'S CODE, LIEBER'S LATEST CODE, A.B.C. 5TH & 6TH EDITIONS. 1180 File 24th January, 1938 YOUR REF. OUR REF. JNL/KM Depots- LONDON 222, TOTTENHAM COURT RD W. 1. ABERDEEN 26, GUILD STREET. BELFAST 8, 10 & 12, MONTGOMERY ST BIRMINGHAM 198, CORPORATION ST BRISTOL 118, VICTORIA STREET. CARDIFF 60, CHARLES ST DUBLIN 120, UPPER ABBEY ST GLASGOW 70, WATERLOO ST LEEDS 25, HUNSLET RD LIVERPOOL 1-3, BERRY STREET. MANCHESTER 6, JACKSON'S ROW, DEANSGATE. NEWCASTLE-ON-TYNE 24, ELDON PLACE, BARRAS BRIDGE. A.{Mr Adams} F.{Mr Friese} Martindale Esq., Messrs. Rolls Royce Ltd., Derby. Dear Mr. Martindale, I thank you very much indeed for your letter of January 20th, which I have passed on to Mr. Shilton and Mr. Harrap who are also giving it their earnest consideration. The theory you propound is most interesting and at last I am beginning to see exactly your trend of thought when referring to "μ speed curves". In fact, I may say that this is the first attempt I have seen on anybody's part to formulate an exact analysis of squeal. It has been a little difficult to connect any "μ speed curves" that we could devise, with μ changes arising from the speed changes of relative movement between lining and drum. As I see it, and as we have to attack the problem at this end, it will be necessary for us to produce a lining having two outstanding friction characteristics;- I A static coefficient of friction no higher than it is kinetic and II A lining which in the cold (this being the critical state) will have a coefficient of friction which does not increase with falling speed but preferably decreases with falling speed, no matter to what high temperature it has previously been submitted. The first thing to enable us to do this is to equip ourselves with means of estimating μ in a simple non-servo brake as tests on a servo brake are misleading when attempting to define coefficient of friction. This I am quite satisfied we can do and I propose to commence along these lines within the next few days. In the meantime Mr. Shilton will be writing to you separately on this subject and we shall doubtless in collaboration arrive at a solution. - continued - | ||