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 stiffness, discussing modifications to Carter's Formula and referencing test results.
| Identifier | ExFiles\Box 25\3\ Scan314 | |
| Date | 7th February 1928 guessed | |
| contd :- -4- The stiffness used for predicting the torsional period is that of the total shaft in lbs.ft/radian. It will be seen that the two conditions corrections considered above account for over 20% of the total crankshaft deflection, so that they are by no means negligible. (2) Modification to Carter's Formula for a double crank. In the case of a 4-bearing 6-cyl. engine, the crank pins are in pairs between the main bearings and the above formula cannot be directly applied. We have added extra terms, and obtained new expressions for the equivalent lengths, as shewn on Fig.1. attached. The lengths L obtained now are for double-cranks. This form of the formula has not been thoroughly verified by test. We have only had experience of one 4-bearing 6-cyl. crankshaft, in the WHERE TEST AND CALC. FIGURES WERE Lorraine car,^ within 1% of each other. However, as this may have been pure chance, it is thought advisable to make some models to test the formula still further. Other data on crankshaft stiffnesses has been embodied in previous reports, and is not set out here. In the attached print shewing Major Carter's formula and his test results, there are some crankshafts that he has worked out from data supplied by us. They are as follows :- 13C Std. Phantom. 14C 20 HP. 15C Special stiff expl: 20 HP. 16C 1-G-1 17C Lorraine Dietrich. Another print attached fig.2. gives the principal results of our own tests on crankshafts. We have succeeded in contd :- | ||