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).
Results of recent work on crankshaft torsional vibrations and stiffness.
Identifier | ExFiles\Box 25\3\ Scan319 | |
Date | 29th April 1928 | |
2 Hs{Lord Ernest Hives - Chair}/Tsu/T29.4.28. CRANKSHAFT TORSIONAL VIBRATIONS. We give below the results of recent work on the above subject. Fig.1 shows the results of tests on the torsional stiffness of crankshafts. Figs. 2 & 3 show torsion tests of a shaft in various stages of machining from the forging to the finished shaft. Fig.4 shows the dimensions etc. of the shafts shown in Fig.1, and Fig.5 shows the crankshaft for the Stutz straight-8 car. These are some conclusions we have drawn from the above tests. Referring to Fig.2, it is seen that although your formula for stiffness is never more than a few per cent out for the whole crankshaft, it is often nearly 100% out in predicting the effect of some small alteration to the dimensions. In this table, results for some of the earlier operations show that the formula under-estimates the stiffness. We attribute this to the fact that the dimensions used in the formula do not include fillets, radii, and "flash", which are then quite large on a partly machined shaft. The later results show a reverse effect, i.e. the formula over-estimates the stiffness. We attribute this to the fact that the shaft was twisted in only two out of the seven bearings all the time. On the finished shaft we have found this to make a difference of 7%. Contd. | ||