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 responding to an enquiry about brake squeak, discussing methods for obtaining friction-speed curves and the apparatus used for testing.
| Identifier | ExFiles\Box 141\2\ scan0249 | |
| Date | 24th January 1939 | |
| 1029 1181 Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale}6/MH.{M. Huckerby} 24th. January, 1939. Institute of Automobile Engineers, Great West Road, Brentford, MIDDX. Your Ref: CGW/BT.{Capt. J. S. Burt - Engineer} Dear Sirs, Brake Squeak. We regret delay in replying to your letter, but the writer has also been abroad. We are very interested to read of your method of obtaining friction-speed curves. For our part we have never been able to obtain curves satisfactorily at steady speeds, but by using the highest possible accelerations and recording apparatus we have obtained more satisfactory results. We apologise for the error on our graph in which we plotted speeds of 50, 100 and 150 ft/min: this should have read 500, 1,000 and 1,500 ft/min. and we have corrected our graph accordingly. The readings were taken off a 12" dia. brake drum fixed to a 30" dia. tyre and wheel, the tyre perimeter reached 44 feet/sec. (or sometimes rather more). Answering the penultimate paragraph of your letter:- (1) The apparatus is driven by pressing the tyre against another tyre rotating fast, thus obtaining a high acceleration. (2) We have been troubled with variations of friction round the drum, the recorded line is always a double wave, one, of low frequency, being the one we are interested in, the other being a high frequency wave superimposed on it. If the drum is concentric to within .001" the latter is not very marked and we can smooth it out in plotting. We would prefer to use a disc to a drum, as it is easier to grind true. | ||