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).
Letter to General Motors Ltd. requesting information on their torsional vibration damper technology.
| Identifier | ExFiles\Box 25\3\ Scan185 | |
| Date | 22th November 1926 | |
| C O P Y. 22.11.26. Letter to General Motors Ltd. :- CRANKSHAFT TORSIONAL VIBRATIONS. We are interested, from a technical point of view, in the torsional vibration damper recently adopted by you on some of your products, particularly so because this device, from what we imagine, operates upon a slightly different principle to the more conventional type of added flywheel such as employed on our own cars and on the Lanchester. Therefore we are taking the liberty of asking if you would be kind enough to enlighten us upon some points of the theory of its operation. It is, of course, understood that any such information you would care to divulge would be treated as strictly confidential. We have seen two types illustrated - one controlled by a laminated spring and another by coil springs. It seems therefore that the damping obtainable from such a device is not dependent upon dissipation of energy by friction as is usual with the added friction flywheel type, and have surmised that it is the case of an added elastic system possessing a free period of its own, the resulting damping being obtained by its opposition to the natural free period of the crankshaft assembly. We agree that slight friction damping could be obtained by the use of the laminated controlling springs but considering the apparent small inertia of the oscillating mass relative to the equivalent inertia of the crank assembly, it would seem that in any case the friction which could be effectively employed would be comparatively small and inadequate if its action were the same as the usual friction dampers. We imagine that the effect of attaching a damper to the crankshaft by a flexible coupling would be - providing the inertia and flexibility were of the correct proportions - to divide the main or 'critical' vibration into two others, the one at a lower speed and the other at a higher speed which would probably be outside the speed range of the engine. contd :- | ||