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).
Effects of friction torsional vibration dampers on crankshaft critical speed and vibration period.
| Identifier | ExFiles\Box 181\M9\ img076 | |
| Date | 7th November 1931 | |
| To M.{Mr Moon / Mr Moore} from Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} c. to SG.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} c. to Hy.{Tom Haldenby - Plant Engineer} ORIGINAL Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}4/KT.7.11.31. x634. FRICTION TORSIONAL VIBRATION DAMPERS. According to Carter's calculations this type of damper lowers the critical speed of the shaft as the damping is increased until finally when the damping is infinite the critical speed is that of the crankshaft with the slipping inertia rigidly attached to the nose. Tests done by Lov.{Mr Lovesey} on Phantom II and 20 HP. showed that this was not so for the master period. This latter was decreased in amplitude as the damping was increased while at the same time the period due to the inertia being rigidly attached increased in amplitude. Thus the damper on our cars decreases the master period and brings up another period at a lower speed, but if we only use sufficient damping just to eliminate the ½ period, the lower period due to the damper is not detectable on the road. The instrument we have for giving a graphical measurement of torsional vibrations can only be used in the absence of a damper which is replaced. Without a damper the magnitude of the vibrations is only about 1½° so we do not think that we could do accurate measurements with a damper fitted when the vibrations are not noticeable on the road. Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} | ||