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).
Engine design choices for valve gear, silencers, camshafts, and crankshafts, with comparisons to American models.
| Identifier | ExFiles\Box 6\6\ 06-page010 | |
| Date | 11th November 1934 | |
| (2) valve engine, therefore the La{L. A. Archer} Salle pipe cannot be reproduced exactly. We will try and get particulars of the new small Buick which resembles our design more closely. VALVE GEAR. We have put the Terraplane silencer on the 20/25 but found that this was utterly useless despite the fact that both are six cyl. engines, with approx. the same capacity and the same compression ratio. In fact if anything the 20/25 compression is lower than that of the Terraplane. We think we may ease our silencing problems by opening the exhaust valve later than has been our practice in the past. Whilst we agree that our accelerations on the camshafts are too high, we think that we should avoid going to the other extreme without reviewing our past experience. Working on a large cylinder as on the Phantom is going to give us a distorted view of valve difficulties. For example we think that the 2.7/25 has reasonably silent valve gear and we anticipate that when we get silent tappets fitted to it we shall not find very much fault with it apart from timing gears. We know that the same valve gear will run up to very high speeds, the eight litre engine drive we should not be susceptible to timing gear rattles. The acceln. & deceln. on the 20/25 camshaft are perhaps higher than the Americans are using, but we can afford to use a balanced cam while they cannot. If we reduce our duration and our positives, the valve springs will have a difficult time. CRANKSHAFT. We would recommend 2.25" crank pin diameter because it is the size of General Motors crankshaft for the La{L. A. Archer} Salle. The general American practice is to have a 4-stud cap for the flywheel bearing which from our experience on flywheel flutter seems to be a logical precaution. Unless there is some very | ||