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).
Performance and silencing of the West Wittering 120° camshaft for the P.2 engine.
| Identifier | ExFiles\Box 13\2\ 02-page126 | |
| Date | 5th August 1931 | |
| Y7090. To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}4/AD5.8.31. WEST WITTERINGHenry Royce's home town 120° CAMSHAFT FOR THE P.2. We send you herewith a curve showing a comparison between the standard camshaft, camshaft for the R.{Sir Henry Royce} engine cams and the W.W. camshaft. All three were taken with the normal compression ratio of 4.5 and the twin carburetters with 1.3" dia. chokes. We have sent a separate report to R.{Sir Henry Royce} which indicates the maximum B.H.P. we can get out of this camshaft with higher compression ratio and the Claudel carburetter. We shall naturally struggle to get the best results, and have put in hand a 5¼ head and camshaft with 114° between the cams. We shall also try running the twin carburetters with large balance pipe between the two branches which will increase our top H.P. but lower our low speed M.E.P. We believe that there is some unexplained difference between the P.2 and 25 HP, and we are trying to discover what this is because it should not be necessary to want such a freak valve timing in order to get reasonably good H.P. With regard to silencing the twin carburetters, the long duration camshaft by dropping the low speed M.E.P. seems to reduce the pumping action of these carburetters and so the noise. With the W.W. camshaft on the road we can obtain very fair silence with a cylinder 8.5" long and 6" dia. having two concentric tubes 4.75" long and 3" dia. giving reversals of flow. This just squeezes into the available space and does not drop H.P. appreciably. We think that we shall undoubtedly require something about this size to silence the twin carburetter unless we are prepared to drop H.P. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||