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 Limited detailing the poor performance, excessive wear, and squealing of trial servo motor linings.
| Identifier | ExFiles\Box 141\3\ scan0291 | |
| Date | 30th July 1934 | |
| X719 Exptl. Dept. Hs{Lord Ernest Hives - Chair}/FJH.{Fred J. Hardy - Chief Dev. Engineer}20/KW. 30th July, 1934. Your Ref: FJF/MD. Messrs. Ferodo Limited, Chapel-en-le-Frith. For the attention of F.J.Field Esq. Dear Sirs, We thank you for your letter of the 23rd July and the servo motor linings ref. S4418. We have given these linings a good trial and the results are as follow :- (1) The rate of wear is excessive. We estimate that they would last 200 miles only on a car. (2) The coefficient of friction when absolutely new is about 0.200, but after a little running it rises to between 0.50 and 0.60 and increases slightly with increase of temperature. (3) The linings squeal very badly. We think that they very high value of the coefficient - i.e. 0.6 - is connected with the abnormal rate of wear. The dust worn off the friction material appears to adhere to the steel rubbing surface so that instead of rubbing against a smooth polished surface the friction material rubs against a rough surface. The squealing of the linings does not worry us very greatly at present as we think we may be able to eliminate or reduce this by modifying the design of the servo motor. | ||