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).
Investigation into gearbox noise amplification on the Phantom III and proposed experiments to solve it.
| Identifier | ExFiles\Box 94\1\ scan0202 | |
| Date | 2nd October 1935 | |
| +328 GRY.{Shadwell Grylls} We ought to follow up these parts Rm{William Robotham - Chief Engineer} Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} C. Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} Hx. Pa.{Mr Paterson} Rdy. E.5/HP.2.10.35. Phantom 3 Gearbox Silence. There is still a problem to be solved in connection with the apparent effect of gearbox noise amplification on Phantom 3. Evidence up to date indicates that a gearbox which may attain a good standard of silence on the Vulture chassis mounted on two crossmembers in a conventional frame becomes noisy when transferred to SpectreCodename for Phantom III. It is found that the mounting has a considerable influence on this, and the best results have been achieved with the most flexible mounting that can be used. It is suggested that the boxed side members of the frame may be behaving as sound amplifiers like the sound box on a stringed instrument, and that the noise issues from the holes in the inner web as from the louvres or vents in the sounding box. It is also not unreasonable that the cruciform member and tail bearing member may act as bridges for transmitting the vibrations. A number of experiments for investigating the source of the trouble are in train as follows:- (1) A temporary modified mounting with the torque control of the box removed entirely from the cruciform member. This is purely of an experimental nature, with a view to making a radical alteration. The scheme is shown on N.Sch.4614 issued 3.9.35, and is arranged (a) to carry the front end of the box from a single point on the cruciform member (b) to carry the front end of the box entirely independent of the cruciform member. The pieces required for this experiment can be made up with very little trouble. (2) double damped rear crossmember made up by rivetting two of the present crossmembers back to back with a layer | ||