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).
Survey on crankshaft torsionals and vibration issues in 6-cylinder and flat-12 engines.
| Identifier | ExFiles\Box 132\2\ scan0183 | |
| Date | 7th December 1940 | |
| 1116 Ev.{Ivan Evernden - coachwork} from Rm.{William Robotham - Chief Engineer} c. Jmr. cWd. c. Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation} c. Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden} Rm.{William Robotham - Chief Engineer}16/ML.7.12.40. Attached is a Memo. from Rm{William Robotham - Chief Engineer}/TAS{T. Allan Swinden}, which is a fairly comprehensive survey on crankshaft torsionals on 6-cylinder and flat-12 cylinder engines on the same bore and stroke. The point that interests us most is emphasized on Sheet 5. That is, that the third order vibration which causes us trouble with broken timing gears etc., at 4,000 r.p.m. and upwards, is due entirely to the inertia of the reciprocating parts and is not affected by the gas torque, which, at 5,000 r.p.m. is out of the running range. The figures given by Rm{William Robotham - Chief Engineer}/TAS{T. Allan Swinden} should be compared with those recorded in Rm{William Robotham - Chief Engineer}/JES.10/JH.13.2.39. in the Crankshaft file. It will be seen that the theoretical and practical results agree reasonably well. The basic fact that we learn from the calculated figures is that if ever we wish to run one of our B.60. engine above 4,000 r.p.m. without a spring drive, we shall have to get the weight of the reciprocated parts down as much as possible. Our pistons have become unnecessarily heavier over the past few years and we can undoubtedly get back to our former standards. On the 75 mm. bore, the problems should be much easier. We hope to have an aluminium camwheel on test before very long. Rm.{William Robotham - Chief Engineer} | ||