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).
Methods to reduce torsional vibrations and booming through engine and body mounting.
| Identifier | ExFiles\Box 12\6\ 06-page023 | |
| Date | 13th March 1931 guessed | |
| (2) fections if we could use it". One knows for certain that it would improve very definitely the vibrations arising from the variation in torsional reactions, but does it make the chassis completely satisfactory compared with the best known of the 6 cyl. big engine type? Naturally we must not expect even this mounting to be entirely perfect for the duty it is intended, but it might prevent much of the energy of these torsional impulses from reaching the frame and the body. It should be realised that the sources of torsional vibrations cannot be reduced by any known means except by increasing the number of cylinders. Bentley and all of us must be alike within very small limits and we can only dull their energy by soft mounting of the engine in the frame, and the body on the frame. Now this brings us to another reason for the variation of booming, which although appreciated may be of more importance than we think - i.e. the body mounting on the frame. (i) We ought to get the same improvement by changing the power unit as we do by changing the entire chassis - i.e. if the engine vary in their smoothness. (ii) It is so extremely well known that very definite difference can be made by altering the tightness of the scuttle insulation (always getting worse as the scuttle is made more solid). This suggests that if the entire body and scuttle could be mounted on soft rubber we might get a definite improvement. We have tried to make this possible without under-frame construction and mounting this on soft rubbers at the front. (iii) I am sorry that I repeat myself so much but it comes about from the fact that the points I repeat have not been satisfactorily cleared up, but the engine mounting that I thought would prove satisfactory is the arm scheme and rear central support with soft rubber (thick) under and above the rear feet. It is still not decided (as far as I know) whether the rear support requires rubber mounting. We think that it does not for torsional vibrations but it may do for lateral ones, which brings us to the next important and oft repeated point. (a) Stiffening and lightening the fly-wheel including its mounting on the crankshaft - i.e. more bolts and stiffer flange as well as back plate which should definitely put up the period if there is one, and is very generally believed by most of us. (b) The crankshaft was to have balance weights - so as to reduce the couples tending to bend the | ||