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).
Failure of chrome vanadium valve springs, especially under extreme cold conditions.
| Identifier | ExFiles\Box 96\2\ scan0143 | |
| Date | 17th September 1936 | |
| Sg.{Arthur F. Sidgreaves - MD} c. Wor.{Arthur Wormald - General Works Manager} c. Hs.{Lord Ernest Hives - Chair} o.{Mr Oldham} D.{John DeLooze - Company Secretary} x354 BY.1/G.17.9.36. Grey - what is the truth about these stresses Rm{William Robotham - Chief Engineer} RE: VALVE SPRINGS. ---------- Referring to Sg.{Arthur F. Sidgreaves - MD}5/E.14.9.36. I certainly do not subscribe to the opinion outlined in your last paragraph. The facts of the case are all against such a conclusion, obviously so because we can run indefinitely on chrome vanadium springs produced by our specified control of the material from the ingot onwards, and we cannot run for a period of 10 hours without failure on the D.T.D.5.A. material supplied after a full discussion of the matter with Dr. Goodacre of Bruntons. This, I think, is conclusive evidence that the material is unquestionably a salient factor. With reference to the further point raised in the last paragraph, which appears to infer that there has been no trouble from breaking springs in the motor car business generally, this idea must be based upon wrong premises as practically every racing car today is being fitted with chrome vanadium springs produced by Messrs. Terrys from our wire and to our heat treatment instructions, and furthermore this remark can be extended to include certain racing motor cycles. It is, therefore, evident that trouble is fairly commonly met with in regard to valve springs, otherwise there would be no demand for these as produced from our wire by Messrs. Terrys. In making the above statements I am not ignoring Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}'s experience in America. This I believe is explicable from en entirely different point of view viz. that we have not had experience in regard to the use of valve springs at temperatures 20° and 30° below zero, such as were common at the time when Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} broke two sets of our springs, and as the springs were supplied from production at the time when we had no failures whatsoever against us for the same chassis, it is certain that it was the extreme conditions of temperature which were responsible for the peculiar experience referred to, and were it possible to get running tests in this country under those conditions my impression is that we should find a solution based upon some modification of the treatment. There is considerable evidence to show that certain materials under extreme cold altered their structure quite appreciably in the direction of becoming more martensitic, and this is what I believe happened to the sets of chrome vanadium springs which failed on the Bentley in U.S.A. The further fact that the springs bought in America were run satisfactorily demonstrates in my opinion that it is | ||