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 a servo squeak and groan, with proposed remedies.
| Identifier | ExFiles\Box 121\1\ scan0384 | |
| Date | 13th November 1940 | |
| Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby}2/ET.13.11.40. - 2 - that it was first in the N.S.R. drum, the linings of which were renewed with no effect, and later, the O.S.F., which decision led to the removal of the front drums and hubs. After this the car was taken out with the front brakes disconnected and the servo squeak was still present. The handbrake would produce no squeak, so it was proved to be in the servo. The original standard spring plate now had a ring sweated on to take the place of the special spring plate, which was now suspected of the squeak. However, examination of the lining showed that some of the rubber solution had found its way on to the lining during the ironing process. This was cleaned off and the servo re-assembled with the same spring plate. The squeak had now gone and the car was passed off. Later, however, being dissatisfied with our previous decision on account of a slight groan on coming off, and after easing the brake pedal by raising it one notch, which made matters worse, we exchanged the servo with that on 8.B.V., as a desperate measure, to return the car to the owner. This was effective in that the groan ceased, but the sponge rod was still required to stop the pedal ripple, and the car was finally passed out. The servo now fitted has neoprene tape, but no special spring plate for water exclusion. The servo was examined and it was observed that the pressure plate was quite badly scored due to the ironings which have accompanied the several new linings. The lining was only bedding properly for the inner third of its width, and so the servo was reassembled and fitted to 8.B.V. without any change. There was no groan at all. If this is confirmed by Hm{Capt. W. Hallam - Head Repairs}, we shall attempt to reproduce the conditions on B.16.AW, by certain alterations which should be made to 8.B.V. before sufficient mileage has been covered greatly to affect the bedding of the servo lining, all in an effort to get a groan, which can then be traced. These are as follows: 1. Increase all clearances, and chromium plate the pins and plate levers, the latter being made to give exactly similar clearances. 2. Ensure that the pedal is quite free of the floorboard and that it has approximately the same return spring pull. 3. Replace the present rear cross-shaft lever GB.3628 by the production type GB.4244. 4. At the same time it is proposed to replace the present engine "idler" lever being a modified GB.3183 by GB.4918. If there is still no groan, we shall have to go more closely into the differences between the two cars. Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} | ||