Power increase modifications for the 25 HP 'China' engine, focusing on timing, valve sizes, and materials for the Phantom II.
| Identifier | ExFiles\Box 5a\5\ 05-page220 | |
| Date | 4th November 1929 | |
| COPY. SECRET AND URGENT. X5771 HS. {Lord Ernest Hives - Chair} FROM R & E. {Mr Elliott - Chief Engineer} R.1/M.4.11.29. c. to SG. {Arthur F. Sidgreaves - MD} WOP. BY. {R.W. Bailey - Chief Engineer} X.5770 X.5771 X.1725 re. 'CHINA(Experimental Engine)' ENGINE 25 HP. POWER INCREASE. Referring to your report Hs {Lord Ernest Hives - Chair} /ACL1/AD2.11.29., we do not think there is much wrong with the timing if we follow Phantom II, which we understand gives the following timing as well as the 116° between the cams mentioned on your chart. [handwritten] see original for sketch. PHANTOM II. MAXIMUM ACCELERATION. This timing is at the moment the heavy acceleration start. Let us talk of nothing but maximum acceleration ever i future, and before taking timings get the tappet clearance to a standard of .015" instead of .013" or less. Regarding valve sizes the exhaust valve can be a little smaller - 1.3" (because this valve is naturally heavier) especially as the engine will nearly always be running with the silencer. The exhaust should also have a thicker head, and will be in Austenitic steel, while the inlet will be in Silchrome. The valve springs will be modernised - i.e. open ended, rapid rating and taper. Agreed that the induction pipe should be 1.5" bore throughout, and the passage between the cylinder bores 1.2", tapering to 1.5" at ends. Fortunately the venturi is the right way round in this latter. Agreed that the exhaust pipe down pipes should be 1.75" dia. I should like the gas passages in the cylinder | ||
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).