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 development, issues, and manufacturing process of light alloy brake drums.
| Identifier | ExFiles\Box 120\1\ scan0352 | |
| Date | 9th February 1944 | |
| (Handwritten in top left corner): Car. (Handwritten in top right corner): 1028. To Rm.{William Robotham - Chief Engineer} from FJH{Fred J. Hardy - Chief Dev. Engineer}/GB. FJH{Fred J. Hardy - Chief Dev. Engineer}/GB. 1/VS.{J. Vickers}9.2.44. Light Alloy Brake Drums. The light alloy brake drums RC.{R. Childs}2261 run on 4.B.50 weighed 13lb. 12oz. each. The iron drums GB.4799 weigh 20lb. each. The weight saved per car is 25lb. Four alloy drums which have run on 12.B.V. and 4.B.50. have covered a total mileage of between 10,000 and 11,000 miles each. The one which we have examined is fit for further mileage. The earlier R.R. aluminium drums had the liners shrunk in. The liners made a crackling noise when cooling and they sometimes came out of the drums. It was found that whatever the initial interference, the most that could be maintained was .026" on a 12" drum, when cold. The area of cross section of the aluminium round the liner must have a minimum of 5 or 6 times that of the iron liner. The open end of the drum must be adequately ribbed. Failure to comply with either of these requirements will result in burst drums. The use of steel liners instead of iron will also produce this calamity unless the thickness of the liner is reduced in the ratio of the moduli of the two materials. When the liners are shrunk in, both the liner and the drum must be machined accurately. This adds to the cost. In order to avoid this cost it was decided to try casting in the liners. The method finally adopted for this was as follows:- (Specification 2L2A) liners were turned to RC.{R. Childs}2260, (Handwritten note over text: Added to the liner casting the Add. 127/MR.6/ET. 10.11.41.) liners were more nearly circular. The liners were zinc plated. The object of this was to prevent oxidation of the iron liner during the casting operation and so secure a good heat union between liner and drum. For casting, the iron liner is supported on the core and the core and liner are heated to 230°C. For this operation the core is placed at the bottom of the oven so that the binder condensate rises clear of the liner. When binder condensate settles on the liner a bond with the aluminium is impossible. Chilling by the liner will also prevent a bond being obtained. - continued - | ||