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 discussing the results of testing 28 types of brake lining material for squeaking and fading.
| Identifier | ExFiles\Box 141\1\ scan0002 | |
| Date | 3rd January 1935 | |
| -2- Up to the present we have tested about 28 types of lining material. Of these many were immediately turned down for squeaking, juddering, breaking up or some such reason. We enclose prints of all the curves which we have in case they may be of interest to you. Our results cannot, very satisfactorily, be compared with yours, as our temperature range is lower, but there seems to be a tendency for us to obtain fading at lower temperatures. We should mention that the metal rubbing surface is 3% nickel steel. The best results for constancy of coefficient were obtained from Mintex Halo 1119 and Mintex Lamina, but, unfortunately, these materials were quite unsuitable in service owing to violent squeaking. The best material of which we yet know, which is also silent in operation, is Ferodo VM.30 and, as this has a 27% decrease in output at 325°F.{Mr Friese}, there is still considerable room for improvement. We notice from your tests on various drum materials that Nitrided Steel gives the least fade. We hesitate to try this on our servo as we found that Nitrided brake drums were very bad for squeaking. Our experiments seem to indicate that any lining which is reasonably free from fading invariably squeaks when warm. The tendency to squeak which we observed with nitrided brake drums appears to extend this conclusion to the following - that any combination of lining material and drum material which is free from fading is liable to squeaking. This is a very unfortunate state of affairs, and we should be very interested to know whether you have observed the same effects. We should also be very much obliged if you could let us know what lining materials the Nos. 3, 10, 13, 14, 18 and 21 represent in table 4, page 11, of your report. We hope that the above information, which will you please regard as being confidential, will be of interest to you, and that we have not imposed too much upon your time by asking for further particulars of your experimental work. Yours truly, FOR ROLLS-ROYCE LIMITED. | ||