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 The Cleveland Graphite Bronze Co. discussing issues with brake servo lining, specifically unit pressure and material fading.
| Identifier | ExFiles\Box 129\4\ scan0190 | |
| Date | 7th April 1938 | |
| Form 2040 10m 7-34 THE CLEVELAND GRAPHITE BRONZE CO. TO: B. F.{Mr Friese} Hopkins FROM: J.{Mr Johnson W.M.} V.{VIENNA} O.{Mr Oldham} Palm DATE: April 7, 1938. SUBJECT: ROLLS ROYCE LTD. BRAKE SERVO LINING With reference to the fourth paragraph in Mr. Robotham's letter to you of February 28th, he states that he does not think that there will be any difficulty due to reduced friction because the end load can be doubled to compensate for the friction loss. He further states that the main trouble so far is that the high unit pressure has caused fading with normal friction materials. Referring now to previous correspondence on this subject, we received information from Mr. Robotham dated February 1st, 1938, giving the maximum unit pressure as 150# per sq. inch, with a maximum speed of 8-1/2 feet per second and a coefficient of friction of 0.37. In my memo to you of February 15th, I pointed out that it would be necessary for us to increase the number of discs in order to compensate for the lower friction, and suggested that we have a drawing showing the entire assembly as well as the thickness of the mating members, in order to suggest the proper change in the thickness of the disc in order to increase the number. It is our opinion that we cannot increase the maximum unit pressure beyond 150# to the square inch, but that rather it should be decreased by using a greater number of discs, as otherwise, instead of reducing the fading, the result would be increased fading with the metallic facings with such high unit pressures. We therefore feel that our suggestion of February 15th, in which we suggested that we have the drawing referred to, is the only one which will make it possible to suggest to Mr. Robotham a satisfactory construction in metallic facings which will overcome the trouble he is now experiencing. JVOP:BC John V.{VIENNA} O.{Mr Oldham} Palm. | ||