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).
Suggestions for camshaft and valve spring design to improve performance and reduce stress.
| Identifier | ExFiles\Box 43\3\ Scan219 | |
| Date | 29th December 1928 | |
| To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rsn. 44003 Hs{Lord Ernest Hives - Chair}/Tsn1/LG29.12.28. CAMSHAFTS. 48090 In reply to E3/M20.12.28 about harmonic cams, it appears that to see whether we can gain anything useful from this, a lot of rather laborious trial calculations will have to be made. I would suggest that we try and suit this new type of cam (particularly for inlet valves) to use a valve spring having about 50% less force valve closed and 20%/30% less valve open. The actual stress range would probably not be increased. The resulting cam would be between cases 2 and 3 in my original examples. It would be possible to get slightly higher lift, which our air flow experiments on SS.{S. Smith} head seem to indicate as desirable. I think if possible we should avoid reducing the actual spring ratings (in lbs/inch) since it will reduce their surging frequency and will increase severity of surging owing to resonance with lower harmonic of valve displacement. With an increased lift the rating of the above spring would be the same or higher than existing ones. I suggest also, for what it is worth, that we modify to sine form the initial acceleration period, so as to reduce the suddenness of application of the acceleration. At high speeds a large acceleration suddenly applied means a large force suddenly applied and this might lead to elastic effects and high speed clatter in push rod valve gear. contd :- | ||