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).
Secret memorandum discussing alternatives for valve springs to reduce stress and breakage.
| Identifier | ExFiles\Box 72\1\ scan0182 | |
| Date | 25th January 1924 | |
| X. 9060 To E.{Mr Elliott - Chief Engineer} HS.{Lord Ernest Hives - Chair} } FROM R.{Sir Henry Royce} RG.{Mr Rowledge} DA.{Bernard Day - Chassis Design} } SECRET. R2/M25.1.24. c. to CJ. BJ. Wor.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} E.{Mr Elliott - Chief Engineer} A.{Mr Adams} C. VALVE SPRINGS. X.9060. I think it would be wise to at once permanently reduce the stress range in the main valve spring, preferably by reducing the lift. If this reduces the power at useful speeds greatly, several alternatives present themselves :- (1) To test 30º seats for inlets only (2) or both valves (3) or use double springs, (or longer springs as E.{Mr Elliott - Chief Engineer} suggests.) Naturally one would prefer to risk the breakage in the tappet spring, but it seems no advantage to do so, so we may as well keep it as it is. If possible it looks as though the valve spring should be made for a stress range of not more than 20,000 and a maximum of not more than 70,000. Some time ago it was thought that valve springs broke by running the engine over speed and allowing the valves to leave the cams. Is this still thought so, and has the EAC. been running over speed and so started the break in the springs? Anyway I still think we should play a safer game. Sometimes we have thought of using a different valve steel for inlet valves, and if the face was 30º we could do so at any time without much risk of putting in the wrong steel, or we could continue using the same steel, making the possibility of such a practice passably easy at any time. 30º would not be any disadvantage for inlets. I recommend comparison to be made on test contd:- | ||