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 a brake lining supplier hypothesizing that brake squeak is caused by surface glazing and requesting a solution.
| Identifier | ExFiles\Box 140\4\ scan0059 | |
| Date | 4th October 1937 | |
| 1181 Rm{William Robotham - Chief Engineer}/AFM{Anthony F. Martindale}5/R.{Sir Henry Royce} 4th October, 1937. British Belting & Asbestos Ltd., Scandinavia Mills, CLECKHEATON. For the attention of Mr. Sisman. Dear Sirs, As we once remarked to Mr. Dalmaine, we are inclined to attribute squeak in brakes to the variation of the value of the coefficient of friction with speed variation: the particular characteristic that is detrimental is to be expected of the glazed surface of a Halo brake lining. This is pure hypothesis, but as extensive users of cars we have noticed repeatedly that a squeaking brake has a glazed surface on the lining, a silent one a dusty surface. Confirmation of these observations was obtained to-day in a striking manner on a 25 H.P. R.R. car fitted with Halo 3L. One front brake of this car occasionally squeaked, the other three were silent. On examination it was seen that the squeaking brake had developed a glazed surface, whilst the pair to it had a matt surface. In neither case were we getting the effect of a high lead lining as the lead had melted out of the surface, especially between the rivet holes in the planes parallel to the carrier plate, and had formed globules. It had not oxydised. In the brake running slightly hotter some dust had been formed on the surface. This is why we want some agent in the lining to help break down the lead on the surface to a soft dust before it melts: small loose pellets of lead in the brake are no use. Yours faithfully, For ROLLS-ROYCE LTD. | ||