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).
Trials of longer duration cams and greater tappet clearance on the 25HP 'CHINA' engine.
| Identifier | WestWitteringFiles\T\March1929-December1929\ Scan262 | |
| Date | 16th November 1929 | |
| HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} Copy to SG{Arthur F. Sidgreaves - MD} [Struck through] Copy to WOR.{Arthur Wormald - General Works Manager} [Struck through] Copy to RV [Struck through] ORIGINAL [Stamp] 25HP. "CHINA" [Circular Stamp: FEB 1929] Long duration cams should be tried at 110°, 112°, or 114°, as well as the 116°. This gives more lap, which, if no disadvantage, would be much better than short cams at 110°. I suggest 112°. It would be a mistake to go on with the short cams I am sure, without a struggle. The engine should also be tested with greater than usual tappet clearance, say .015". Never mind the noise for the time being. I fear that our low power at high speeds has partly been due to our anxiety for silence. Our creation of the long toe take up is bad for low speeds because it leaks, and at high speed the valves are not open enough to be useful, hence I suggest that to be comparable with, say, the Lorraine, we should test our longest cams with a large tappet clearance. We want to get uniform vibration, and .015" tappet clearance seems about the best. It is just in the heavy acceleration. R.{Sir Henry Royce} [Handwritten in left margin]: Tested on small bore 18/5/27. No difference in power [Handwritten top right]: x5770. x5090. | ||