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).
Continued analysis of crankshaft stiffness, comparing calculated and tested values and the reinforcing effect of bearings.
| Identifier | ExFiles\Box 6\1\ 01-page097 | |
| Date | 9th December 1927 guessed | |
| contd :- -2- This explains to some extent the apparent large over-estimation of the stiffness (15%) when approaching the finished condition. The large discrepancies in the opposite direction between the test and calculated values in the early machining stages are due to the difficulty of estimating the dimensions of a forging for use in the formula, due to the large radii, and to the 'flash' on the webs etc. A very noticeable feature of the results is the unsuitability of the formula for predicting the effect of small alterations to the dimensions. Although this formula has proved itself to be nearly always within 10% of the stiffness of the finished shaft in bearings, it is in some cases 30% out in predicting the actual drop in stiffness due to a single operation. It appears therefore that these tests as recorded in this table are more valuable for estimating the increase in stiffness attainable by small modifications to an existing shaft than the process of recalculating its stiffness by Carter's formula. For large modifications this may not apply. Reinforcing effect of bearings. In graph.B. we include, in addition to the 20 HP. results again for comparison, the effects of removing some of the bearings on several crankshafts. The standard Phantom, the recent sports Phantom (Lec.2462 now superseded by Lec.2488) and the 20 HP. are shown with all 7 bearings, and with brgs. 1, 4, and 7. The reductions in stiffness are as follows :- contd :- | ||