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).
Modifications to valve lift curves for rockers without rollers, specifically regarding timing and rocker radius.
| Identifier | ExFiles\Box 43\3\ Scan135 | |
| Date | 7th March 1927 | |
| To RG.{Mr Rowledge} from E.{Mr Elliott - Chief Engineer} c. to BJ. BY.{R.W. Bailey - Chief Engineer} Hs.{Lord Ernest Hives - Chair} X4003 E5/M7.3.27. RR. F.10. VALVE LIFT CURVES FOR ROCKERS WITHOUT ROLLERS. X.4003 X.3822 We have examined schemes Nos. 881, 888 and 889. Sch. 888 - inlet valve lift curve - appears to be O.K. Regarding the exhaust cam - Sch. 889. - it was intended to make this the same length as the present exhaust cam to suit the present timing which seems, to be satisfactory, and verbal instructions to this effect were given when the sch. was handed over at Derby. The difference however is very small and amounts to the exhaust valve closing at 60° instead of 68° before bottom dead centre. Moreover it is question whether we ought not to try the original timing aimed at by R.{Sir Henry Royce} e.g. 60°. Our recommendations are to push on with these valve lift curves as they are but to put in hand another exhaust valve lift curve to the present timing to have ready in case of any loss in power. If on the other hand you would prefer to stick exactly to the existing timing we should be quite agreeable. We should like Derby to set out cam sch. 889 to check the size of the grinding wheel. With regard to sch. 881. - Valve rocker movement - there is some question of a difference in timing from A.{Mr Adams} block to B. block due to using interchangeable camshafts. When this point was discussed in Derby I thought you were saying it was due to the curvature of the rocker movement being reversed from one block to the other relative to the camshaft rotation. Actually the question of the interchangeability of the camshafts did not arise in the early design work since the pad centres were definitely out of line with each other. Now however the pads very nearly line up all that remains is to alter the rocker radius from 2.225 to 2.200 and the difference will be eliminated for all practical purposes. The cam lift will thereby be reduced slightly and the pads will be a little desaxe. It appears however more important to get the timing identical and we therefore recommend this alteration to be carried out. E.{Mr Elliott - Chief Engineer} | ||