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).
The testing of various camshafts and induction systems, analysing their effect on engine noise and performance.
| Identifier | ExFiles\Box 108\2\ scan0198 | |
| Date | 16th January 1939 | |
| -2- which enables a standard of silence to be maintained which is comparable with the standard Wraith engine. In the case of this experimental shaft, the figure is .010 which represents the 'running' clearance. At .012 setting the tappet noise becomes objectionable. Another important factor with these shafts, is their relative effect on tick-over. To give a representative figure for this, we shall give the lowest r.p.m. maintaining even slow running (no miss) at that tappet clearance which just gives the standard degree of silence as mentioned above. In this case the figure is 300 r.p.m. The second camshaft to be tested is the experimental shaft EX.31550, giving a slightly longer duration to the exhaust, but keeping the same inlet cam. Graph S.65 shows that the power is about the same as the normal Bentley shaft. Max. tappet clearance retaining standard degree of silence = .015". At .017" the tappet noise becomes objectionable. Slow running :- Lowest even r.p.m. = 300. Graph S.68 compares the two induction systems when applied to this shaft. The third camshaft tested is the standard Wraith shaft EX.1416 and Graph S.66 shows the power comparison against the normal Bentley V.{VIENNA} shaft. Slow running :- Lowest even r.p.m. = 230. Graph S.69 compares the two induction systems when applied to this shaft. Finally Graph S.67 compares the two induction systems when applied to the normal Bentley shaft EX.3466. It is interesting to note, when considering Graphs S.67 and S.69 that the combined power difference of camshaft and induction system, constitute the main power difference between the Wraith III and the present Bentley V engine. The other slight differences are of course pistons | ||