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).
Technical memo discussing the effects of a long duration camshaft on engine performance.
| Identifier | ExFiles\Box 13\2\ 02-page116 | |
| Date | 21th July 1931 | |
| X7090 HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} E.{Mr Elliott - Chief Engineer}} FROM R.{Sir Henry Royce} R1/M21.7.31. C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} RG.{Mr Rowledge} P. 2. LONG DURATION CAMSHAFT X.7090. X.7230. This confirms previous experience that our standard is good for ordinary use, but as it is would bear a very definite increase in compression ratio which would restore the low speed power and give some very definite increase in high speeds. Some modification to the induction system and carburetter might shew differently with different camshafts - i.e. the twin would ask for late closing inlet. As it suggests we have overdone the duration we might try the same cams with increased overlap until it shews poor slow running. Our double exhaust valve ports are not as bad as valves only overlap very slightly - i.e. only open very slightly together in the two outer ports, and not at all with ordinary camshafts, and you have had good results with these same ports on 'China' and 'Japan'. The low power is due to low compression ratio, and carburetter requiring a large depression to get enough air to fill up well. Apparently the only advantage of longer duration than standard is that it may permit of higher compression ratio, which increases pumping vigour and makes better use of what gets into the cylinders. An indicator diagram would be useful, and one thinks it may show exhaust opening too early for maximum low speed power, and also bad for exhaust valves: now we are timing with more clearance 45º or 50º is early enough for the exhaust. Higher compression ratio may be better for exhaust valves - P. 2. is very low at 4.6 - I do not think masked valves are practical, but slight masking may be tried. R.{Sir Henry Royce} | ||