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 Messrs. Humber Ltd. discussing the use of Chrome-Vanadium for valve springs and design considerations.
| Identifier | ExFiles\Box 126\2\ scan0049 | |
| Date | 4th August 1936 | |
| X1069 Hs{Lord Ernest Hives - Chair}/Smth.24/MA. 4th August, 1936. B.B.Winter, Esq., Messrs.Humber, Ltd., COVENTRY. Dear Sir, Mr.Robotham has asked the writer to reply to your letter of June 30th regarding valve springs, for which we thank you. It is our practice to use Chrome-Vanadium for valve springs rather than piano wire, on account of its freedom from surface decarburisation effects and also its slightly greater safe stress range. We find it impossible to design a spring which is free from surge at all points in its speed range, and so keep the total coil clearance with the valve open down to .125" in order to reduce the stress range whilst surging. We have been reading a paper on "Permissible Stress Range for Smal Helical Springs" by F.P.Zimmerli of the Barnes-Gibson-Raymond, Co., of America. It gives an account of extensive experiments on the subject and the results generally confirm our experience. We enclose a curve which summarises the conclusions. We trust this information will be of interest to you. Yours faithfully, FOR ROLLS-ROYCE LIMITED. | ||