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).
Technical memo comparing the use of aluminium and iron brake drums on various car models.
| Identifier | ExFiles\Box 120\1\ scan0247 | |
| Date | 19th November 1937 | |
| [Handwritten] 1028 also 1260 To Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} 19.11.37. ALUMINIUM BRAKE DRUMS. On the grounds of cost we thinkwe should give up all idea of using aluminium drums on any car at all. It will also save us a lot of trouble. We consider that the alloy drum on Wraith is satisfactory in every way:- (1) Squeaks we attribute entirely to linings and 27.G.VI., for example, never squeaks with alloy drums and without tipping shoes. (2) Crackles do not occur on Wraith. (3) The failure of the drum in France (which was not a dangerous failure) was due to incorrect setting of the brakes, too high a proportion of front brakes, and an attempt to cheapen the drum, and need never occur again, even on an alpine pass. On Bentley, from a sports driver's point of view, the aluminium drums are worth having because - (1) We get infinitely more consistent braking. (2) The crackles which still occur slightly on the front drums we have very greatly reduced and are not blatent. (3) We still do not attribute squeaks to alloy drums, they are just as bad on a standard Bentley, if not worse, We can save so much weight on brake system linkages that the increased weight of iron drums is counterbalanced, compared to present standards. From a brake point of view we are quite happy with iron drums, when we make them heavy. The losers will be the suspension and steering sections. To get a comfortable ride one wants as little damping as possible. If there were a 40% reduction of the brake weight on Ph.III. the shock, damper poundage could be halved, we think. This was shown on a recent test on the Bump rig. With the drums off we had to remove the shock dampers completely to get the car to tramp. With two equally satisfactory brake systems, the alloy drum system will always be lighter. Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} | ||