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).
Laboratory report on the examination of A.C.7 bearings and proposals for improving the casting process.
| Identifier | ExFiles\Box 115\3\ scan0141 | |
| Date | 9th December 1937 | |
| To. By.{R.W. Bailey - Chief Engineer} c. to Rm.{William Robotham - Chief Engineer} c. to RMC. c. to Hs{Lord Ernest Hives - Chair}/J.W.W. 1020 Laboratory. H1.2/RS.{Sir Henry Royce's Secretary}9.12.37. Re: A.C.7 Bearings. On examination of bearings and the pots from which they are machined, it appears that the best parts are turned away. As can be seen in the photographs M.1500/1 and 2 there is a relatively porous region coincident with that part of the pot actually used for the finished bearing. This suggests the desirability of either using a die cast ring or centri-cast pot as near as possible to the finished size of the bearing or re-designing the die now in use. It appears from the examination of solid bars, that the porous region is then confined to the centre and that the external part is relatively fine and free from porosity and coarse crystal structure. Thus, it appears that bearings of finer and more uniform structure could be obtained by replacing the present holed pot or billet by one without a hole, but of approximately the same length and weight, the outside diameter being reduced by about 1/2" which I believe would still give sufficient machining allowance for the Bentley and 25-30 H.P. bearings now in production.) This change would enable the billets to be cast at a slightly higher temperature say, 700 to 720°C., in a somewhat cooler die without any chance of cracking. This form of casting has been found to result in less liability to oxide trapping, porosity and the development of coarse eutectic structure with which it is often associated. (See photographs M.1500/3 and 4.) Photograph M.1500/5 shows the structure close to the running surface of a big-end bearing which gave a satisfactory result on 10,000 mile test. Our present bearings often give a similar structure but it is to be noted that when the rough machined or finished bearing gives a considerable variation in hardness, it is found to be coarse. | ||