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).
Crankshaft torsional vibrations in B.60 and flat 12-cylinder engines.
| Identifier | ExFiles\Box 124\2\ scan0296 | |
| Date | 17th February 1941 | |
| To Wa{Mr Wallis}/GSB. from Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden} 1044 Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}4/ST.17.2.41. CRANKSHAFT TORSIONAL VIBRATIONS IN B.60 AND FLAT 12-CYLINDER ENGINES. --------------------------------------- Some time ago we received from you a memo (Wa{Mr Wallis}/GSB.11/RS.{Sir Henry Royce's Secretary} 16.12.40) commenting upon and criticizing our own memo on the above subject (Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}1/ST.9.12.40). Although our answers - in one case our excuses - were formulated on the day we received your memo, we deferred our reply, firstly owing to pressure of other important work, and secondly because from your conversation we gathered that you held no brief for Ker Wilson. If we still quote Ker Wilson it is after studying Tuplin, Timoshenko, Shannon and Den Hartog. At all events we have salved our own conscience, and probably become a little wiser in the process. In case you are still interested in the subject, now almost ancient history, we attach a copy of your memo with the subjects lettered in the order in which we have dealt with them. A.{Mr Adams} The amplitude (αs) referred to on page 2 is the actual amplitude at resonance at the free end of the shaft and not the equilibrium amplitude which we will call α₀. It is therefore a function of the magnification factor at resonance, which we maintain it is impossible to evaluate without practical experimental assistance. Tuplin (Torsional Vibration p.199) declares that it is impossible to arrive at a figure by assuming dissipation of vibration energy by crankshaft hysteresis alone and quotes losses due to displacement of the oil film and crossbinding in the bearings. In these circumstances the damping factor in Shannon's damping coefficient would become an unknown quantity, and quite obviously the magnification factor 1 / (1 - p²/n²) where n = frequency constant for natural vibration and p = frequency constant for applied torque, used by Tuplin and Ker Wilson does not operate. | ||