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).
Limits and accuracy of engine valve timing for the 40/50 chassis.
| Identifier | ExFiles\Box 33\4\ Scan071 | |
| Date | 9th September 1921 | |
| X1770 RR. from BY.{R.W. Bailey - Chief Engineer} WEH. Hs.{Lord Ernest Hives - Chair} BY4-F2.9.21. X1770 40/50 CHASSIS. CAMSHAFTS. X3423 RE LIMITS ON THE TIMING OF THE ENGINE. There appears to be quite a number of points where slight inaccuracies can creep into the timing. I do not think, under our present system, that we can actually hold the works nearer to the actual marking on the flywheel and the .004" clearance between the tappet and the valve than 3½°. In setting the valves we consider that the important points which should be accurate are - Inlet closing and Exhaust closing. The first would probably affect the rate at which the engine filled up - the second would tend to cause overlapping, which at slow speeds is not desirable. Under the above conditions therefore I consider the valve timing possibly with our present accuracy should be - Exhaust Opens 3½° early or late. Inlet Opens 3½° early or late. In checking the matter over, I find that the lift of the valve has been designed in view of a .004" clearance and therefore the engine should be set to this amount. I am going into the question of improving the accuracy of the valve timing and am fixing up a scheme by which this can be attained, when I will again reconsider the question of limits and fix final ones ultimately. I consider a reasonable limit would be a variation of 1½° either way, this, however, cannot be attained with our present limits. I consider the valve timings you have been able to get, as given on EP{G. Eric Platford - Chief Quality Engineer}/Ihn9/H24821, are reasonable for present conditions, and that we cannot reduce these limits at the moment, but hope to do so in the future. BY.{R.W. Bailey - Chief Engineer} | ||