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).
Noisy camshafts, comparing them with Vauxhall and Chevrolet designs, and discussing tappet issues.
| Identifier | ExFiles\Box 10\3\ 03-page025 | |
| Date | 16th June 1937 | |
| -2- (5) The camshaft we are running on the test bed is very noisy. A certain amount of this noise is undoubtedly due to inaccuracies in manufacture because some of the tappets are very much quieter than others. We attach comparisons of the ramps as measured on this camshaft, and those measured on the 25 Vauxhall, which is particularly quiet, also the Chevrolet. Taub says that on this type of shaft the noise does not usually come from the ramp unless this is ridiculously short. He states that they ran into the same trouble on the Chevrolet, and found that it was due to the contour of the cam near the toe of the camform. He explained that they overcame the trouble by stoning the cams until they got a quiet gear, and then altering the master cam accordingly. This sounds crude, but actually the 25 Vauxhall is as quiet as any push rod valve gear we have ever heard, and on this car they have used the Chevrolet profile exactly. We attach to E's copy of this memo drawings of the Chevrolet and Vauxhall camforms which Taub kindly gave us. We think it is imperative that we have camshafts made up to these drawings, in order to get a basis of comparison for power and silence with our own. We may lose power, and we may be able to go back to our high acceleration with more expensive materials, but we believe it will be well worth the cost to re-produce the results that General Motors have obtained. (6) We showed Taub out bottom tappet, and he said that holding the push rod on the tappet is liable to cause the tappet to cock over, and so prevent it rotating. If the tappet did not rotate, it scuffed. Taub pointed out that the Chevrolet tappet was the result of an enormous amount of development work, and they did not know of anything simpler or more effective. We attach a drawing of the Chevrolet type of tappet. (7) They found it was imperative to get the maximum quantity of oil on the tappet faces under running conditions. We have tried this, but up to date have not derived much benefit therefrom. Rm.{William Robotham - Chief Engineer} | ||