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).
Vibrations and booming issues in Phantom II and 25 HP models.
| Identifier | ExFiles\Box 137\4\ scan0199 | |
| Date | 9th February 1931 | |
| X634. To R.{Sir Henry Royce} From Hs.{Lord Ernest Hives - Chair} c. to Sg.{Arthur F. Sidgreaves - MD} Wox. c. to E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} c. to EY. Hs.{Lord Ernest Hives - Chair} 3/AJ.9.2.31. PHANTOM 11 & 25 HP. VIBRATIONS & BOOMS. We feel that we have not given a sufficiently clear description of the vibrations and booms which cause customers to complain on Phantom 11 and 25 HP. In the case of Phantom 11 the vibrations which worry us are torque reaction, which may occur from 15 to 22 m.p.h.; and a vibration and boom which occurs from 50 to 65 m.p.h. The feature of the high speed vibration boom isthat it is there irrespective of power. It is there with full throttle, light load, or unretard. In some cases the boom is worse on retard than on the forward drive. It comes on much below the maximum speed at 65 m.p.h. it is approximately 2500 engine revs. Above that speed it tends to quieten down. The fact that it comes on below the maximum speed, raising the gear ratio would not help us but as the weight power ratio would suffer, this would probably add to our complaints. This particular complain of high speed boom is worse on Phantom 11 than on Phantom 1. It is possible to find odd cars which do not confirm this, but on the average Phantom 11 is worse for booms. We feel that Phantom 1 has just as much vibration but does not boom. The reason we suggest why Phantom 11 is worse, is because we consider the engine unit is more resonant than Phantom 1 with the separate gearbox. Another possible cause is that Phantom 11 crankcase is lighter and the ribs are not so heavy. The gear ratios of Phantom 1 and Phantom 11 are practically the same, 14/52 Phantom 1 and 11/41 Phantom 11. Quite a lot of work was done on the question of booming before I took 25-EX. car to U.S.A. One alteration we made to that car was to fit it up with four Diabolo rubber engine feet with soft rubber. The result was disappointing the booms were still there. If there had been any improvement in 25-EX. we should have left them on the car. We were very disappointed with the result of | ||