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 and resolution of brake faults on Captain Barnato's car.
| Identifier | ExFiles\Box 90\5\ scan0033 | |
| Date | 13th November 1940 | |
| To Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} 261K BRAKES ON CAPTAIN BARNATO'S CAR. ------------------------------- We feel that this production B.V, having shown most of the faults one could expect, merits a report. When the car arrived, the complaints were servo groans and erratic braking and the failure of the pedal to return as quickly as Capt. Barnato would like. We tried the car, and only by unfair adjustments on the front brakes could we stop slight diving to the right. There was a slight servo groan, but the brakes were consistent in operation on a short run. The servo was taken down and found to have no tape fitted, with the result that oil had entered round the outside of the spring plate and, working in from the outside, had nearly reached the inside diameter of the lining. This explained the erratic brakes. There was no neoprene available, so the tape was soaked in a rubber solution, and the whole re-assembled for suspension tests. A new VG.90 lining was fitted and ironed in 2nd gear with the propeller shaft disconnected. The next step was to increase the clearances on pins and levers throughout the braking system. The pins and plate levers were already chromium plated. The front shoe-equalising links were checked for adjustment to stop diving, and an extra spring was fitted at the near cross-shaft, to allow quicker pedal return. At the same time a specially pressed water shield was fitted to the gearbox underneath the oil seal housing, and also a special spring plate with an extra deep corrugation to act as another water shield concentric with the first. The car was tested through Boyleston Water splash 8 times at 20 M.P.H., without the servo under-shield, and no water entered the servo as was shown by the complete absence of the groan associated with these conditions. There was, however, a suspicion of a judder in the form of a slight pedal ripple, which was entirely removed by a "sponge rod" between the pedal and the servo cams, the spring being effective up to 15 lbs. pedal load. The next fault showed itself after the car had been passed off, and was a squeak, whose pitch was known to be peculiar to the servo spring plate. It was found that the water shield on the gearbox was rubbing on the spring plate, due to the pressing being made with too large a diameter. A new shield was obtained, having the correct dimensions, but the servo squeak still continued. The squeak only occurred at low pedal pressures and was somewhat ellusive as it soon disappeared on warming up. It was of typical spring plate high frequency, although impossible actually to locate by ear, as shown by the fact that, on two occasions, it was confidently maintained | ||