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).
Conclusions on damping engine vibration periods and inertia torque.
| Identifier | ExFiles\Box 179\3\ img141 | |
| Date | 14th April 1931 | |
| -2- in spite of the greater inertia torque exciting the higher period. Both periods were sharply defined. Between them and above the higher one the engine was remarkably smooth even at 4000 R.P.M. (78 M.P.H. in 3rd gear.) The conclusions we have come to are :- (1) We cannot damp out the master period of a large 6 cylinder engine by a large damping load because of the wide fringe of roughness below the period. (2) That the addition of a small harmonic damper causes a period at a lower speed which would still be unpleasant on the overrun, but would prevent the crankshaft being broken by driving on the top period. (3) We must give up all idea of trying to damp the top period and must therefore put it well above the speed range of the engine. We require therefore a damper of fixed friction setting to eliminate the half period and separate damping of the crankshaft pinion. No gear rattles will then arise due to using sufficient damping on the flywheels. The autofriction damper meets these requirements if we remove the centrifugal loading. We prefer the torsional shaft to the springs of the low inertia spring drive as a stiffer drive can be employed without overstressing any parts. The fixed part or hub is of low inertia. We are therefore fitting to this damper a similar slipping flywheel to the old high inertia type and will then have a damper to meet all our requirements. (1) Independent damping of the pinion. (2) Low inertia hub. (3) Adequate damping for the half period. (4) No roughness below the top period. HA/H.Grylls. | ||