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).
Engine vibration, resonance, and noise issues in Phantom I and Phantom II models, and the influence of coachwork.
| Identifier | ExFiles\Box 117\1\ scan0012 | |
| Date | 14th October 1930 | |
| To R.{Sir Henry Royce} from Ss.{S. Smith} We are constantly being reminded by car owners that our P.I model was much smoother and quieter running than is P.II. We know ourselves that is generally the case, and how all our difficulties of this description became more intensive synchronously with the alteration of design in respect of frame and engine mounting whereby the latter was supported on four points, and we, in consequence, had to drop any benefit which the torque-reaction-dampers of P.I might have given. Exhaust noises and booms with P.II have to be taken account of in a way which was not experienced with previous models. Some months ago we obtained one of the latest six-cylinder Bentleys which was tested by many of the Company's officials on the arterial roads, when it was agreed that the engine appeared to be practically free from any noticeable vibration or roughness at any point within its range of useful speed, certainly up to 80 m.p.h. What an immense advantage this must be in the avoidance of resonance sounds and booms in coachwork. In our P.II chassis we have to strain every technical nerve to enable our engine to tide over the 15 to 25 m.p.h. speed on direct drive in such a way that the more meticulous owners do not complain of every variety of vibration and "booming"; also again at the high speeds approximately 60 m.p.h. we are again faced with this difficulty and menace to our reputation. To be content to take the view that all this trouble is due to the body fitted, or would not be there in its absence, is, I feel, a dangerous policy, for doubtless although there is an immense amount which the coachbuilders can and must do in so constructing every part of the coachwork that resonance is avoided as far as possible, at the same time we know that the engine vibrations on a chassis are generally worse when carrying a loose test-rig only, and may become considerably reduced when damped down by a properly made and fixed body, whilst sundry important cases of complaint have lately been remedied by a simple modification to the method of attaching our scuttle to the body, thereby tending to damp out the vibration set up by our mechanism. I have written at length on this subject because I feel that it is one of great importance and was rather | ||