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).
Camshaft design, valve lift curves, and practical considerations for improving performance.
| Identifier | ExFiles\Box 13\2\ 02-page031 | |
| Date | 20th December 1928 | |
| To Hs{Lord Ernest Hives - Chair}/Tsn. from E.{Mr Elliott - Chief Engineer} 47090 E3/M20.12.28. CAMSHAFTS. 7090 8090 X.5090 Thank you for your Hs{Lord Ernest Hives - Chair}/Tsnl/LG12.12.28., and accompanying papers. I have not had much time to think about your suggestions yet, but there is undoubtedly something of practical value in it. We have always recognised there were possibilities in varying the acceleration to the spring force, but you have carried the matter further than we have done hitherto. There are three main practical considerations in this matter: (1) Valve lift must be kept as low as possible for the sake of the valve springs. (2) Floating speed is required to be as high as possible. (3) The shape of the valve lift curve must be as near the ideal as possible for admission of gas. This last consideration favours short blunt lift curves rather than tall thin ones. Replotting your curves to a common valve lift they would appear to come roughly as in diagram, the tendency being to lose on the area of the valve lift curve, but to gain considerably in floating speed. [DIAGRAM with three curves, labelled ① STANDARD, ②, and ③] We could however expand the curves (2) and (3) in length to regain the lost area, or it suggests also using a flat topped cam. I am unable to deal with this matter further at the moment but will return to it in the New Year. E.{Mr Elliott - Chief Engineer} | ||