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).
The theory and effectiveness of crankshaft vibration dampers.
| Identifier | ExFiles\Box 25\3\ Scan215 | |
| Date | 15th December 1926 guessed | |
| 2. by coil springs. It would seem therefore that the damping obtained from this device is not dependent upon the dissipation of energy by friction or by the opposition of a frictional force, as may be the case with the so called Lanchester type, and I imagine therefore, 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 normal crankshaft assembly. It is of course clear that slight frictional 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 crankshaft assembly it would seem that in any case the friction which could be effectively employed would be comparatively small and inadequate if its mode of action were the same as in the more usual friction damping fly wheel. I imagine that the effect of attaching such a damper to the crank shaft by a flexible coupling would, providing the inertia and flexibility were correctly proportioned, split the main or "critical" vibration into two others, one at a lower speed and the other at a higher speed, which latter would probably be outside the speed range of the engine. Assuming the main critical vibration without the damper to occur within the speed range of the engine, does this damper effectively eliminate the "Master" vibration, if so, is this replaced by another vibration at a lower speed? Also, if a lower speed vibration is manifest say when coil controlling springs are used, is the internal friction of the laminated springs relied upon and found to be adequate in providing the necessary damping to make this vibration inappreciable in practice. I should be very interested to know if the above reasoning as to the theory of this form of damper action is correct and would very much appreciate your answers to the above questions and your own views as to its method of action. It is a pity you did not stay here a little longer, in fact until today, as there was one thing for which we are renowned which you missed and that is a really good London fog. There is one on today and from the weather forecast it seems likely to last some time. Best wishes, Yours sincerely, | ||