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).
Tests to diagnose and resolve a 'boom' or vibration issue on Phantom I and Phantom II models.
| Identifier | Morton\M19\ img134 | |
| Date | 11th March 1931 | |
| -2- E.S.3/H.T.11.3.31.Cont'd.{John DeLooze - Company Secretary} and towed the bare crankshaft with balance weights. This made no difference, the boom was still there slightly at the same speed. From other tests we have done it can be said definitely that balance weights do not help us as regards this particular complaint. Although we think it is dangerous to use 25 HP. tests for information on Phantom ll we think it is interesting to know that we have run a 25 HP. unit fitted with a cast iron crankcase, lightened and stiffened flywheel, and balance weights, and although this engine possesses virtues for high speed smoothness there is no difference in the amount of boom. The one result which still stands out as a 100% cure with regard to booms is the Diamond mounting. We have confirmed this several times. We are going more and more to the view that the difference between Phantom l and Phantom ll is not any fundamental difference but is due to some peculiar resonance on Phantom ll round about the dashboard. The results which lead us to believe this are on some cars we have made a remarkable improvement by disconnecting the rear engine feet, on one car we have made a big improvement by disconnecting the steering column. Another car has been improved by disconnecting the dashboard. Also the complaint on Phantom ll is that the noise complained of is that which can be heard in the front seats, in the rear seats it is not nearly so objectionable. In our tests we are confining ourselves to the fault which customers and Sg.{Arthur F. Sidgreaves - MD} complain of. That is, when we say lighter and stiffer flywheel and balance weights do not help us it is only intended to apply to this complaint. We have carried out some work with an electric motor having an out of balance disc fitted to it and we think we should be able to get some results, but it is too early to say. We think it is a piece of apparatus which it might pay us to develope so that we can check up different bodies for booming characteristics. He. | ||