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).
Engine vibrations and the theoretical effectiveness of different damper types.
| Identifier | WestWitteringFiles\P\October1926-November1926\ Scan101 | |
| Date | 9th November 1926 guessed | |
| contd :- -5- In the case of the Phantom not only do we find 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 shewing any appreciable amplitude at the half critical speed. In a R.A.E. report No. 3039 & 3039A - which is a theoretical investigation of viscous-friction dampers - is concluded that where viscous friction dampers of a finite damp-ing co-efficient 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 employed. 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 contd:- | ||