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 assumptions for calculating the bending of a Peregrine crankshaft.
| Identifier | ExFiles\Box 115\2\ scan0379 | |
| Date | 10th January 1939 guessed | |
| APPENDIX. APPROXIMATE TREATMENT OF BENDING OF PEREGRINE CRANKSHAFT. Assumptions. For a first approximation, with criticism of the limitations imposed. (1) That the shaft is simply supported at the journals. This appears to be true except that the support is not point contact. (2) That the adjacent throws do not exert any constraint on the throws under consideration. This is obviously not true, but the effect of this constraint would be to reduce the bending and so the case considered may be regarded as an extreme. (3) The crankcase is rigid compared with the shaft and diflection of the case and bending of the bearing panels can be ignored. This again is untrue but the amount of the effect is impossible to calculate and so this is a normal assumption widely used. (4) For load and bending calculations the load on the pin is taken to act at the centre and the combined loads due to the webs and pin to act at the centre of the throw. This is accurate for load values but for bending the effect is greater than would be the case with distributed loads which occur in practice. The bearing loads on Nos.1,7 and 4 main bearings calculated on the above assumptions from a theoretical indicator diagram derived from the power output and an assumed maximum pressure are shown for various crank angles on the accompanying blueprints Nos.1 and 2 and the load on the crankpin on No.3. (5) For the calculation of bending effects the shaft can be treated as a uniform rectangular bar. The principal values of EI for the bending moment equation being obtained from the results of a test made by HPS{Horace Percy Smith - Experimental Factory Mgr}/W.Bell. BL.2260. (6) The crank throw is supported on the edge of the bearing when under load. (A) Simple loading without balance weights. | ||