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).
Appendix comparing the 'orthodox' and 'Bower' methods for calculating loading on crankshaft bearings.
| Identifier | ExFiles\Box 115\2\ scan0509 | |
| Date | 16th November 1939 | |
| -4- Appendix. The foregoing polar diagrams were obtained by the orthodox method of dividing the forces at each cylinder equally between each adjacent bearing. Since this is essentially an approximate method, Bower attempts to give the correct answer by considering the crankshaft as a continuous beam. This means that each bearing is now receiving loading on a percentage basis from every cylinder. In order to see what effect this method would have on a loading diagram, the end journals were treated in this way and the result appears on Sheet 2. Thisis for direct comparison with Sheet 3 giving a diagram for the same journals calculated in the orthodox way. To obtain an even more direct comparison the diagrams were replotted for magnitude only on Sheet 1. As would be expected the Bower diagram shows a kink at 60° indicating the firing point of a cylinder next but one to the journal. This effect is not repeated at 260° when the cylinder in the other bank fires, owing to coincidence with inertia forces at three other cylinders. The most interesting feature is that except at one point the orthodox diagram gives everywhere a higher loading figure than the Bower diagram. It is for this journal about 15% higher at the point of maximum loading. Thus although the Bower diagram is academically correct, the orthodox method is far simpler to persue, and gives a result which provides a factor of safety for the designer. Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden} | ||