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).
Solutions for body booming and vibration, focusing on chassis construction and engine mounting designs.
| Identifier | ExFiles\Box 12\6\ 06-page017 | |
| Date | 28th February 1931 | |
| HS.{Lord Ernest Hives - Chair} E.{Mr Elliott - Chief Engineer} ) FROM R.{Sir Henry Royce} BY.{R.W. Bailey - Chief Engineer} DA{Bernard Day - Chassis Design}/EV{Ivan Evernden - coachwork}) (At Le CanadelHenry Royce's French residence.) RL/M28.2.31. C. to SG.{Arthur F. Sidgreaves - MD} MOR. X.634. C. to PN.{Mr Northey} EP.{G. Eric Platford - Chief Quality Engineer} P. 2. BOOMING OF BODIES. X.7830. The accumulation of evidence from the many trials the Expl. Dept. have made strongly points to the impossibility of getting a booming body silent, and though naturally something can be done with the chassis by removing unnecessary causes of vibrations and insulation, MUCH MORE can be done by making bodies with all the main features - i.e. roof, floor, etc - of low period well damped construction. All other construction should be condemned. Some standard means of testing should be found, such as that I suggested of a shunt wound motor supplied with variable voltage to its armature circuit. It could then be run at known revs. taken from the S.M.M.T. at the brushes, and given out-of-balance. I am sure that no-one on earth, however experienced with motor cars, would expect better results than we get with this 18-EX. I have never experienced anything better with a 6 or even 8 cyl. engine anywhere near this power and size. That it is perfect I do not claim but it is exactly what we must expect, with the one exception of the 65/75 MPH. vibration, which, although not noticeable in the back, is unmistakeable in the front. Since this has been found I have always thought we could render it harmless. Now you will see exactly why I wanted long ago 12 cyls. because most of our known causes of vibrations do not exist, and moreover I hope that we can use an engine mounting sufficiently hard so that the engine crankchamber can help the torsional stiffness in the frame, which seems impossible to get by any othermeans, as it seems hopeless to do so further back in the chassis as we attempted with the cross in the frame. Some long time ago I though our scheme of central front support and rear arms was the wrong way round, and I hoped that the rear (gearbox) support and front arms would be considerably better, and hence we gave four arms that we thought would allow of this or any other scheme that was reasonable. I still think that we ought to get a good, if not the very best mounting by this scheme, with perhaps fairly hard rubber in the front and very flexible in the rear feet, with no metal in contact. Should this require lateral stiffening the metal plates could be tried in various ways, but results suggest that no good (1) | ||