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 valve clearances, tappet roller alignment, and the complexities of valve spring performance analysis.
| Identifier | ExFiles\Box 66a\2\ scan0098 | |
| Date | 25th May 1929 guessed | |
| contd :- -2- in the guide and the valve seating is cut exactly square with the guide, the valves set up a click when they go on to their seat if the tappet clearance is much greater than .004. We think that inlet valves could be run with .0015" clearance and exhaust valves with .0025" provided the bore of the valve guide is well polished. Our practice is to finish off the bore by forcing a hardened steel ball down it. If we get the valves correctly seated we find that trouble (1) is of minor importance. (3) Tappet rollers out of square with the cam and consequently roller clicking against side of its guide. We believe you are quite familiar with this complaint and with the precautions which have to be taken to overcome it. While we much appreciate the work done by various people in analysing the surging of valve springs we have formed the opinion that it is such a complex subject that the results obtained are often so divergent from expectations when using the design of a commercial spring that now if we get an unsatisfactory spring we merely try a number of others until we get one which has the best all round performance. We have done some work on the analysis of spring life and the practical results of certain ratios of max. stress to stress range I will look up and send them on when I have time. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||