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).
Performance and standardization of 25 HP valve springs.
| Identifier | ExFiles\Box 106\5\ scan0058 | |
| Date | 28th November 1931 | |
| To BY.{R.W. Bailey - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} c. to E.{Mr Elliott - Chief Engineer} 85060 Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}1/MJ.28.11.31. 25 HP. VALVE SPRINGS. Replying to By/SS.{S. Smith}4/N24.11.31. we wish to point out that the standard 25 HP. valve spring is pulled out to 2.000 to give the required poundage. The rating is therefore less than 78 lbs. per inch. Evidence at other loads gives a rating of about 70. A deflection of 1.2" on Hs.{Lord Ernest Hives - Chair}451 gives a load therefore of 86 lbs., instead of 97. We consider therefore that the stress is also reduced in this proportion. Springs to Hs.{Lord Ernest Hives - Chair}410 of free length 2.400 were run successfully on 19-G4 for 15,000 miles. Prior to that all our engine had a spring of 2.950 free length working therefore at a calculated maximum stress of .44000, from which we conclude that the normal method of stress calculation is wrong, as they did not take a permanent set. We are, however, investigating the possibility of using a spring to give the required loads at a lower stress. Should the springs (Hs.{Lord Ernest Hives - Chair}451) at present running on 18-G4, in France, which we consider stressed to 86000, prove satisfactory we see no reason why they should not be standardised. Hs{Lord Ernest Hives - Chair}/H.Grylls. | ||