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).
Investigations into reducing tyre noise on the Phantom III model.
| Identifier | ExFiles\Box 157\1\ scan0270 | |
| Date | 6th January 1936 | |
| X1332 To E.{Mr Elliott - Chief Engineer} c. to WGP. c. to By.{R.W. Bailey - Chief Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} c. to Ey. Hs{Lord Ernest Hives - Chair}/sym.1/EW.6.1.36. Phantom III Tyre Noise. In continuation of our report Hs{Lord Ernest Hives - Chair}/sym.23/EW.30.10.35, we can now give some further information on the question of tyre noise. We continued our investigations on the cast iron drums by first of all removing the 6 rear body mounting packing pieces (3 on each side of the frame) and replacing same with large slabs of rubber. This experiment shewed no material improvement. We next disconnected the rear ends of the road springs from the frame and inserted large slabs of rubber between the rear spring eye and the frame, and considered we had effected a slight improvement. The front end of the road springs were then treated in like manner, the axle being held in its correct position on the drums and under the body by means of chains and staples in the ground. This gave us a condition where the whole of the rear axle and rear springs were completely isolated from the frame by means of rubber slabs and the result was a considerable improvement over anything we had tried before in respect to tyre noise heard and felt in the body. Our next move was to fit the rubber isolation in a practical manner and rubber bushes were made and fitted to the spring shackles. These did not give us the result hoped for when first tried, but examination of the spring eyes and shackles shewed that the eyes were making metallic contact with the shackles due to the compression of the rubber under varying torque loadings. This of course necessitated the manufacture of modified shackles and rather held up the job. However, we eventually got them fitted and our tests both on the drums and the road shew a definite improvement in tyre noise. We also tried a set of special Dunlop tyres of the '90' type with the outside edges of the tread chamfered away into the well of the tyre. These tyres are an improvement upon standard '90' type and when used in conjunction with the rubber shackles give a 90% cure for the tyre groan. The fitting of rubber shackles, however, does definitely interfere with the stability of the car on the road, and we are still experimenting with a view to improving same. | ||