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).
Power increase for the 'CHINA' 25 HP engine, covering timing, valve sizes, materials and pipe dimensions.
| Identifier | ExFiles\Box 113\2\ scan0143 | |
| Date | 4th November 1929 | |
| COPY. SECRET AND URGENT X1725. HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce}& E.{Mr Elliott - Chief Engineer} R.1/M4.11.29. c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} By.{R.W. Bailey - Chief Engineer} X.5770 X.5771 X.1725 re. "CHINA" ENGINE 25 HP. POWER INCREASE. Referring to your report Hs{Lord Ernest Hives - Chair}/ACLL/AD2.11.29., we do not not think there is much wrong with the timing if we follow Phantom ll, which we understand gives the following timing as well as the 116° between the cams mentioned on your chart. PHANTOM ll. MAXIMUM ACCELERATION. see original for sketch This timing is at the moment the heavy acceleration start. Let us talk of nothing but maximum acceleration ever in future, and before taking timings set 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 | ||