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).
Analysis of experiments on solid friction dampers and their effect on engine vibration.
| Identifier | ExFiles\Box 25\3\ Scan233 | |
| Date | 22th February 1927 guessed | |
| contd :- -2- Some experiments were made with a solid friction damper consisting of a small flywheel at the front end of a six throw crankshaft and free to slip torsionally against the friction. A point which was found to differ from Major Carter's observations on radial engines, was that the damper did not lower the critical speed but resulted in a reduction of the amplitude of the 'master' vibration and the growth of another vibration at a lower speed which was previously free from vibration. By further increasing the damper friction the vibration at the original critical speed could be reduced but at the expense of increasing the vibration at the lower speed. With the damper clamped solid the whole vibration was transferred to this lower speed. It was further found that the lower speed vibration in all its stages was much more critical than the higher one requiring only a slight variation of speed to pass through it. The high speed vibration extended over a much greater speed range. These results seem more what would be expected from a flexibly driven damper. I should be interested to know if this result is considered due in some way to the use of a solid friction damper as opposed to the viscous friction type considered in this paper or, being at the end of the six throw crankshaft, it approximated to the case of a flexibly driven damper. With a 6 crank engine not fitted with any form of damper one is often troubled with the effects of the harmonics of the gas torque curve which appear at 1/2, 1/3, 1/4 etc. of the main synchronous speed when these speeds are encountered with large throttle openings. Usually the main synchronous speed is well outside the working range and it is only these lower speed torsional vibrations which are encountered. We have found that a solid friction damper, without being unduly heavy, is very effective in removing these vibrations although the same damper has little effect on the main synchronous vibration which however comes well outside the normal speed range of the engine. ------------------------- | ||