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 thermal expansion and heat transference properties of different brake lining materials.
| Identifier | ExFiles\Box 141\3\ scan0222 | |
| Date | 20th November 1933 | |
| All Communications to be addressed to the Company. FERODO LIMITED FERODO REGD. TRADE MARK BRAKE & CLUTCH LININGS CHAPEL-EN-LE-FRITH, VIA STOCKPORT, ENGLAND. TELEPHONE: 19 CHAPEL-EN-LE-FRITH (4 LINES) TELEGRAMS: FRICTION, PHONE, CHAPEL-EN-LE-FRITH 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. Depots:- LONDON 222, TOTTENHAM COURT RD W. 1. ABERDEEN 26, GUILD STREET. BELFAST 8, 10 & 12, MONTGOMERY ST BIRMINGHAM 202, CORPORATION ST BRIGHTON 84, QUEEN'S ROAD. BRISTOL 19, PARK STREET. CARDIFF 39, CHARLES ST DUBLIN 120, UPPER ABBEY ST GLASGOW 70, WATERLOO ST LEEDS 25, HUNSLET RD LIVERPOOL 1-3, BERRY STREET. MANCHESTER 32, CATHEDRAL ST NEWCASTLE-ON-TYNE WORSWICK CHAMBERS, 10, WORSWICK ST OFF PILGRIM ST Messrs. Rolls Royce Ltd., Derby. For the attention of Mr. G.W. Grylls. Dear Sirs, We thank you for your letter of the 16th instant and have pleasure in submitting the observations following on the subject in question. In the first place, the expansion of Ferodo M.R. by temperature normal to severe brake applications is extremely small - in fact negligible - consequently pedal movement is noticeably increased when the expansion of a drum is the maximum. At the same time, M.R. being relatively a poor conductor of heat (specific heat .304) there would be no appreciable temperature rise at the sole of the shoe unless the drum ran at very high temperature and the braking effort was sustained for a very long time. Ferodo M.Z. on the other hand, expands when heated approximately .012" on 1/4" thickness at 520° F and being a better conductor (specific heat .244) the transference of heat units to the shoe will be increased, that is to say the rate of transference is extremely slow, as indicated by Diagram No. 453 enclosed; hence, during any normal brake application the expansion of the shoe could hardly have any appreciable effect on pedal movement. The present writer has paid very little attention hitherto to the movement of shoes and is under the impression that such movements as occur would seem to tend to straighten the shoe rather than to increase its normal radius, having in mind that any tendency to radial movement would be resisted greatly by the rigidity of the web of the shoe Referring to rivets in contact with the drum, there can be no doubt that this arrangement would increase the temperature of the sole of the shoe, since the rivets would not only transfer heat from the lining and drum but also the heat units generated by the friction of the rivets themselves against the drum. In all probability, the augmented temperature from the last named source would be substantially greater than from the other source. In fact, aluminium rivets might reach a temperature that would seriously | ||