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).
Analysis of valve gear performance, push rod deflection, and spring surge at various engine speeds using an oscilloscope.
| Identifier | ExFiles\Box 17\6\ Scan325 | |
| Date | 29th November 1934 | |
| -2- Hs{Lord Ernest Hives - Chair}/Smth.12/KW.29.11.34. Figs. 2 & 3 are full size tracings of some of the results obtained in this manner. The full lines are the low speed reference diagrams. Fig. 2 refers to standard valve gear run at engine speeds of 1500, 2000, 2500 & 3500 r.p.m. With this gear valve bounce causes power drop in an engine at 3,000 r.p.m. The effects of push rod deflection may be seen at the higher speeds on the lower (heavy acceleration) portions of the lift. It will be seen that the gear rides away from the theoretical curve at speeds lower than the usually accepted bouncing speed. Our experience with silent tappets confirms this. The riding commences at the 1st change-over point. Figs. 3 (a), (b) & (c) show the effect of progressively reducing the stiffness of the push rod and Fig. 3 (d) refers to the case where the stronger valve spring, which has been developed for use with silent tappets, was used. The valve lift diagrams were confirmed in one or two instances by observations with an Elverson Oscilloscope. It was further noticed by means of this instrument that both the E.81550 and the E.85666 springs surged at every speed down to about 2000 r.p.m. (engine speed). It is suggested that a photographic valve motion indicator of the type described should provide a valuable aid in the development of cams and valve gear for a push rod engine. Hs{Lord Ernest Hives - Chair}/F.Ll.Smith. | ||