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).
Test report detailing efforts to resolve a 'boom' or vibration issue by modifying engine mountings.
| Identifier | WestWitteringFiles\U\August1930-November1930\ Scan177 | |
| Date | 1st November 1936 | |
| -2- HS{Lord Ernest Hives - Chair}/IALL/STC.11.36 contd. was a definite alteration in the boom. The boom now was almost cleared on the forward up to 70 m.p.h. (2620 r.p.m.) but was present from this to the maximum speed. On the retard it boomed from maximum speed down to 62 m.p.h. (2320 r.p.m). This had moved the boom 4 m.p.h. (150 rpm.) higher on the scale. The boom still being bad. This being the first definite change, we decided to support the engine by a central mounting at the rear. We therefore used the Y bracket at the rear of the gearbox. Diabolo rear engine feet were fitted with soft rubber having no set up. These feet did not take any of the weight of the engine but just the engine torque. This gave us an all round improvement, a very slight boom coming at 70 m.p.h. (2620 R.P.M.) on the forward. The retard being 63 - 59 M.P.H. (2360 - 2210 R.P.M.), this being 50% improved in intensity. We now isolated the Y bracket with rubber, to no advantage. We thought that by accident, in fitting the rubber insulations, a certain amount of load might have been put on the Diabolo engine feet, so we tried it with the bottom rubbers removed. No improvement was noticed. The Y. bracket was now made solid again by replacing the rubber washers by steel ones, bottom rubbers of the Diabolo feet still left out. The car in this condition gave the best result so far obtained. This, however, leaves sufficient noise & be open to criticism. | ||