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 viscous-friction and centrifugal dampers for reducing engine vibrations and harmonics.
| Identifier | ExFiles\Box 25\3\ Scan165 | |
| Date | 9th November 1926 guessed | |
| contd :- -5- that the critical amplitude is less than the 20 HP. but the lower vibrations - or harmonics - are correspondingly less severe and on the engine investigated we failed to get a diagram shew-ing any appreciable amplitude at the half critical speed. In a R.A.E. report No.3039 & 3039A - which is a theor-etical investigation of viscous-friction dampers - is concluded that where viscous friction dampers of a finite damping co-effic-ient are rigidly driven, the damper requires to be undesirably heavy to be effective. Also it is shewn that "a much smaller "damper can be made effective by adopting an elastic drive of "suitable rigidity instead of an infinitely rigid drive". This latter arrangement seems to be similar to the original damper employed on the first Goshawk and we therefore think it would be worth while to test this again and carry out further investigation on it. It was suggested by Mr. Royce that a centrifugal damper would be preferable to the constant friction type at present em-ployed. We know that if the damper friction is increased until the damper virtually becomes part of the shaft, the resonant speed falls to a lower value, the range between the speeds depending on the polar inertia of the damper. In the case of the 20 HP. the damper when locked solid reduces the resonant speed from 3200 r.p.m. to 2400 r.p.m. Therefore if the damper became virtually solid, or the friction became very high, after the 2400 RPM. had been exceeded, we should expect to be free from resonance effects at both speeds. We are preparing some notes on the method we employ for estimating the resonant speeds of six cylinder contd :- | ||