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 vibration experiments on a 25 HP engine, focusing on the flywheel, crankcase, and crankshaft.
| Identifier | ExFiles\Box 137\4\ scan0121 | |
| Date | 21th November 1930 guessed | |
| 25 HP. VIBRATIONS. (1) With the car fitted with a bare 2" pin crankshaft, flywheel (no clutch parts) and straight through drive, we found that vibrations started at 2800 R.P.M. getting worse at 3100 R.P.M. then better up to 3500 R.P.M. when a considerable noise began attaining a maximum at 3900 R.P.M. and dying away more or less suddenly at 4500 R.P.M. to give way to a quiet period up to 4800 R.P.M. when a vibration started that could be felt as a high frequency vibration in the steering wheel. (2) To lessen the rigidity of the crankcase we removed the cylinder head and block. All the vibrations in the last experiment were far worse there being no smooth speed after 2800 R.P.M. At 3100 R.P.M. (the flywheel period) the vibration was twice as bad as in the last experiment. (3) We have also done experiments to separate the various deflections of the flywheel and crankcase and crankshaft when loading the flywheel in a vertical plane. We first loaded the flywheel in the plane of the cartridges up to 1000 lbs. giving at the circumference a vertical movement of .015" and a horizontal movement of .021", the deflections being approximately proportional to the load. Afterwards, in order to get couples of the same order of magnitude but with less load on the bearing, we arranged to load the flywheel at 39° from the crankshaft flange. Loads up to 100 lbs. were then sufficient. Experiments were done with No.6 crank at T.D.C. and at 90° after T.D.C. No appreciable difference in deflections were found under these two conditions, never more than 5%. We then found out how much of the horizontal movement of the rim of the flywheel was due to the crankshaft flange bending and how much due to the back of the flywheel. The movement of the flange is multiplied up to the same radius as the flywheel deflection. From the graph it is seen that the bending of the flange contributes considerably to that of the flywheel. While doing these experiments we noticed that No.6 bearing cap was undergoing considerable angular deflection. This deflection is shown by the line (%) on the graph, the readings being taken from an extension of the oil union at the centre of the cap. | ||