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).
Improvements for gear tooth design (barrel shape, bedding) and exploring auto-adjustment mechanisms for tappets.
| Identifier | ExFiles\Box 178\3\ img108 | |
| Date | 17th September 1929 | |
| (2) REASON. (6) There is no reason why J.{Mr Johnson W.M.} 3. should be worse than J.l., but there are many reasons why it should be better. There is some satisfaction that we cannot get the wheels right even with changing - i.e. they are all bad, so we may find how to make them all good. BARREL SHAPE. (7) Suppose it is the picking up (engaging) of the new tooth or the parting with the end of the old tooth, would it be possible to make them full in the centre so that taking on a new tooth was gradual (very slightly.) BEDDING. (8) Naturally we should never have them tight under any circumstances of temperature etc, and one would have most faith if they showed the same bedding right across the tooth, preferably on the pitch line or all over. (9) It will be understood that the feature of convenience has kept us away from putting the wheels at the rear end for many years, but we had hoped that more accurate machine work and scientific grinding of gears would make the undesirable practice of changing wheels quite unnecessary: in fact we thought it could be tolerated no longer on account of cost. (10) TAPPETS. We expected clearance to vary and we have two schemes to meet it. The first - and roughly practical - is the long toeto the cam with rat trap spring on rocker to make it follow and keep with tappet. I am rather inclined to think we shall not get much satisfaction out of this. The Cadillac auto-adjustment of the same principle as the original English scheme does not seem quite right to me, because I cannot see how it retraces its adjustment, if and when it becomes too tight. Will someone contradict and explain this, or agree that it is necessary to make it not only take up but pay out the adjustment. Auto-adjustment is the right thing: we have given designs but so far as I understand have not succeeded, and the scheme has been shelved for other work. I shall expect a report from Mr. Elliott on this, and if it is possible to apply. You will remember that we fathered the idea of only making the auto-adjustment quite small to cover changes due to expansion, and say a 10,000 mile wear, so that if it fails the engine still goes well, and only a small click of the tappet is apparent - i.e. maximum clearance say .020". R.{Sir Henry Royce} | ||