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).
Test report on camshaft Ex.23243, detailing adjustments to tappet clearances to optimize slow running and noise levels.
| Identifier | ExFiles\Box 91\1\ scan0452 | |
| Date | 10th December 1936 | |
| 300 E.{Mr Elliott - Chief Engineer} from Rm{William Robotham - Chief Engineer}/FD.{Frank Dodd - Bodies} c. to Hs.{Lord Ernest Hives - Chair} c. to By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} Rm{William Robotham - Chief Engineer}/FD{Frank Dodd - Bodies}5/R.10.12.36. 33-EX. This engine is fitted with a camshaft to Ex.23243 having inlet cam form Rm.{William Robotham - Chief Engineer}98. exhaust " Rm.{William Robotham - Chief Engineer}42. Timing with .020" tappet clearance. I.O. 1° B.T.D.C. E.O. 40° B.B.D.C. I.C. 48° P.B.D.C. E.C. 6° B.T.D.C. Silent tappets are deleted with this camshaft. We have tested the car for slow running and tappet noise with the inlet valves set to .004", the exhaust tappet clearance being varied from .006" to .010". The slow running with the inlet and exhaust valves set to .004" and .006" respectively is equal to a standard P.III with automatic tappets fitted. We noticed, however, that the distribution was bad at 10 M.P.H. and until the engine settles down to 6 M.P.H. the slow running is very erratic. The tappets are very quiet at this setting, and it would be impossible for a customer to distinguish between the fixed and automatic type. We then tried the exhaust set at .008", leaving the inlet at .004"; the engine seemed to settle down to a steady 5.6 m.p.h. quicker at this setting, but we still had the rough distribution period at 10 m.p.h. No tappet noise could be detected in the car, and only a very slight noise with the ear against the bonnet. The exhaust tappets were then set to .010" still leaving the inlet at .004", the slow running was still very good at 5 m.p.h., but the best results were obtained with the exhaust set at .008". No tappet noise is audible in the car even when set at .010" and when listening outside by the bonnet it is in no way objectionable. There is a slight warming up period, but not comparable with that on the P.III series. The tappets have been left set to - Inlet .004" Exhaust - .010" on this car, with the object of finding any adverse criticism. Rm{William Robotham - Chief Engineer}/F.{Mr Friese} Dodd. | ||