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).
Valve spring design, hardening, and safety margins for Condor and other engines.
| Identifier | ExFiles\Box 56\2\ Scan046 | |
| Date | 17th January 1928 | |
| 4290 Hs. {Lord Ernest Hives - Chair} RG. {Mr Rowledge} E. {Mr Elliott - Chief Engineer} BY. {R.W. Bailey - Chief Engineer} from R. {Sir Henry Royce} C. R5/M17.1.28. RE. VALVE SPRINGS. X.3616 CONDOR AND ALL OTHER ENGINES. X.2993 X.290 I am very pleased to hear of the good results obtained with - (1) The newer practice in the stresses of the spring. (2) The newer practice in cam design. (3) The open ended type. (4) The improvement in hardening - double quenched lower brinell. I agree to these, but from the figures given and the whole results, and considering that we cannot rely on all springs being the same brinell, I should recommend aiming at something below 440, because it is too near the danger zone, whereas you have only feebly proved that the 406 is too low. I would rather be too soft than too hard. The characteristic on this side of the best possible appears to have a slower slope. I therefore suggest aiming for not more than 420, and would prefer to agree to 410. Fortunately the way the springs break is not disastrous. We should in practice have a greater margin of safety because of the slower speed and greater periods of rest. The Condor spring, owing chiefly to the increase of speed, is I believe the spring with the lowest figure of merit, so that our practice on all our engines should be safe, and valve spring troubles a thing of the past, (providing we get old stock scrapped and generally take advantage of our knowledge). R. {Sir Henry Royce} | ||