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).
Analysis of engine and flywheel vibrations, diagnosing the cause as crankcase vibration.
| Identifier | ExFiles\Box 137\4\ scan0109 | |
| Date | 5th November 1930 | |
| -2- finished at 3500 R.P.M. At 4200 R.P.M. a very considerable noise was experienced which shook the engine mountings. We therefore consider that the crankshaft is the cause of our "flywheel vibrations", the flywheel acting as a magnifier. We then towed the car fitted with a plain parallel shaft instead of crankshaft and no flywheel. The rubber drive was used as coupling to the gear box. Under these conditions the engine was absolutely smooth up to 5300 R.P.M. To the plain parallel shaft we then fitted a standard flywheel and clutch. Throughout the whole range the engine was slightly rough in comparison with the last experiment. At 4500 a vibration started which was not finished at 5200, but was diminishing. This vibration is about 20 to 30% of that due to the bare crankshaft with no flywheel. We shall now try the W.W. flywheel and counter weights originally designed for S.S. but scaled down to suit the 2" crankshaft in 12-G1V. We have just accidentally discovered that a 2.2" bore engine running on the bed with a 1 1/4" pin lightened type crankshaft and flywheel, has a flywheel period at 3100 R.P.M. The only thing in common between this engine and present 25 HP. engines is the crankcase. The only suggestion we have at the moment is that the flywheel vibrations are due to a crankcase vibration. | ||