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).
The investigation into abnormal wear of rear brake linings and the effect of cooling systems on various car models.
| Identifier | ExFiles\Box 141\2\ scan0333 | |
| Date | 10th September 1940 | |
| To Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby}1/ET.10.9.40. ABNORMAL WEAR OF REAR BRAKE LININGS. --------------------------------- This fault made itself felt in the first place particularly on the COMET, which, having considerably higher acceleration than any other of our cars, requires very frequent use of the brakes. EFFICIENCY CURVES OF RATIONALISED SYSTEM. -------------------------------------- An apparatus was made to take efficiency hysteresis curves for wedge pressures against pedal loads, and a preliminary test was made on the RIPPLE, as it was thought that the unequal wear was a peculiarity of the rationalised braking system with hydraulic fronts and mechanical rears. The curves obtained increased our suspicions, so that the COMET was taken over and efficiency curves taken; but although the fronts do come on very slightly after the rears, the curves were otherwise perfectly normal. Although these results were quite convincing, an attempt to check them by temporary measurement on the road was later made on the CRESTA, after the COMET had gone to Canada. EFFECT OF COOLING OF WHEEL COWLS AND AIR DEFLECTORS. ------------------------------------------------- First, however, we obtained cooling curves of the drums under a variety of conditions, it being fairly clear that the cooling of the rear drums was at fault, since these are the same as the front drums, but have considerably less air circulating round them. The cooling curves on the COMET showed that the fronts cooled twice as fast as the rears, the wheel cowls having considerable effect. A great improvement in cooling was obtained by means of an air deflector fitted to the carrier plate. At this point tests were transferred to the CRESTA. Cooling curves again showed that the fronts cooled twice as fast as the rears and the effect of the wheel cowls was confirmed, but the same deflectors were of very little use on this car. It does not follow, however, that a single deflector cannot be made to work on any car, as this was only the simplest possible type. The adjustments were always checked before runs, as the size of the air gaps between linings and drums has considerable effect on the results. The CRESTA was then driven hard, with and without wheel cowls and air deflectors, and with and without adjustments slackened off; but although the cooling rate in the latter case was twice as fast as the original rate, the ratio of front/rear temperature was never greatly affected, always approaching unity. | ||