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).
Laboratory report on a failed 20/25 HP valve spring, attributing the failure to overstressing.
| Identifier | ExFiles\Box 106\5\ scan0051 | |
| Date | 3rd July 1931 | |
| HS{Lord Ernest Hives - Chair}/GRY.{Shadwell Grylls} 85060. BY/EM3/J.3.7.31. 20/25 H.P. Valve Springs. We are now in receipt of a report from the Laboratory with regard to the valve spring which you handed to us which had failed on test. The Laboratory report that the spring was quite normal in every respect and that there is no evidence of any flaw which would account for the failure. We understand that this spring had been produced by pulling out a standard spring and we are of the opinion that the cause of the failure was due to overstressing since our experience has been that the chock stress of valve springs should not exceed 80,000 to 85,000 lbs. per square inch if the springs are to be reliable in service. We suggest that the remaining springs on this engine should be examined to see whether they are still of their original free length or whether they have taken a permanent set. BY/EM. | ||