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).
The prediction of periods for crankshaft torsional vibrations.
| Identifier | ExFiles\Box 25\3\ Scan311 | |
| Date | 7th February 1928 | |
| CRANKSHAFT TORSIONAL VIBRATIONS. PREDICTION OF PERIODS. We give hereafter the principle results of recent work on crankshafts done in the Expl: Dept: It has nearly all been embodied in previous reports, but is here collected together to give a resume of the subject. In order to predict or explain the existance of a crankshaft period at any particular speed, it is necessary to know the torsional stiffness of the crankshaft and the moments of inertia of the various parts of the crank system. (1) Crankshaft torsional stiffness - calculation and measurement. With the aid of the formula evolved by Major B. C. Carter of the Air Ministry, this can be calculated with remarkable accuracy. A print shewing this formula together with Carter's test results are attached. This formula gives the equivalent length, in terms of the main bearing journal, of one complete crank. To obtain the stiffness of the whole crankshaft, this equivalent length must be multiplied by the number of cranks; also, any extra amount of main bearing not included originally, in the simple crank must be added. In the case of some car crankshafts there is also a long flexible extension on the nose, which has to be taken into account both in comparing measured and calculated stiffnesses, and in predicting torsional periods. The dimensions used in the Carter formula are only simplified ones, i.e. mean values when sections are varying. contd :- | ||