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 manufacturing specifications for two types of experimental Bentley rear composite brake drums.
| Identifier | ExFiles\Box 84\2\ scan0363 | |
| Date | 21th October 1935 | |
| To RHC.{R. H. Coverley - Production Engineer} x206 HS{Lord Ernest Hives - Chair}/AFM.{Anthony F. Martindale}20/KW.21.10.35. Bentley Rear Composite Drum. We are wanting to try a number of composite drums, made in various ways. The chief differences will be in materials used for liners, and the method of fixing the latter. We attach a sketch of a composite brake drum. We would like you to make six alum. castings to this drawing in RR-53, heat treat them to ensure maximum strength, and leave enough material on the inside (where the liners are fitted) to enable us to try various interference fits. The greatest interference fit we anticipate using is .020" on the diameter. We may want to try a forged drum at a later date, but we understand that unless we go to the expense of making dies the forging will be defective in strength due to bad flow lines. (1) The first drum should have the outside of the liner heavily copper-plated. We suggest .004" for the plating thickness. Presumably the liner will be turned accurately on the outside before plating, and in this case it should be rotated in the electrolyte to ensure an even deposition of the copper. When the plating is finished, the outside diameter should be measured and the aluminium drum turned to give an interference fit of .006" (minimum) on the diameter. The liner should be secured by N.M.C. rivets. When the drum is completed we would like it putting in a lathe and a small ball race fixing to the end of a suitable tool, and pressed really hard on to the rubbing surface while the drum is rotated. We are informed that N.M.C. steel work hardens very considerably, and would like to find out if we can produce this hardness in this manner. (2) The second drum should not have the liner plated. It should be shrunk in with an interference fit of .008". The liner should not be work hardened. It should be secured with N.M.C. rivets. | ||