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).
Adjustments to valve timing and improvements to valve spring design.
| Identifier | ExFiles\Box 33\4\ Scan079 | |
| Date | 1st August 1926 | |
| To RG{Mr Rowledge} & Hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} BY.{R.W. Bailey - Chief Engineer} c. to B.J. X1770 R3/M23. 8. 26. RE. VALVE TIMING. X.3822 X.1770 X.2993 We feel we are getting towards an excessively early exhaust and a late inlet, and that much of the worry over this valve timing has been caused by unsuitable induction systems. The most hopeful thing to test with the present cams available appears to be inlet cam to Sch.796 used as the exhaust, and inlet cam to Sch.797 used as the inlet, these two cams being spaced 108° apart on the camshaft. We think our valve gear is more reliable than the Curtiss because we have rollers instead of rubbers, and are not so depended on the lubrication. Regarding valve springs we think the most hopeful and practical will be the triple valve spring we are sending you. The original springs we think had too big a stress range. We think the springs specified on Sch.801 should give reasonable satisfaction and that the clearances should be quite satisfactory, but we should have worked for a lower stress range in the puter spring. We think that the external dia. should be increased to our original 1.4" and the clearance between the springs should be reduced to .05", and the stress range in the inner spring more than in the outer spring. We cannot see any excuse for wrongly heat treated springs. We are sending you in addition to the cluster spring, which is only intended for experimental research, a striple spring contd :- | ||