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 casting process for half bearings, discussing issues with hardness, cooling, and proposing alternative die designs.
| Identifier | ExFiles\Box 115\5\ scan0257 | |
| Date | 6th March 1939 guessed | |
| The inside of the half bearing is cast against a mandrel that is fixed in position and therefore at the same temperature as the rest of the die. The difference in hardness between the inside and the outside of the bearing shews that the die form for the inside is too hot, and that cooling does not take place evenly towards the middle of the section of the casting. Sketch III shews the way in which parts of the casting are chilled while other parts remain hot with the resultant effect upon its hardness. In my opinion too much attention is paid to casting to an external die form and insufficient attention to the peculiar eutectic freezing property of this alloy, which results in open grain size and varying hardnesses. I feel that if they wish to produce castings of the same even quality as those produced by this firm, they must use a die for casting a ring without flanges as is our practice, and I supplied the Wellworthy representitives with a print of one of our ring dies. If however they must have castings with a flange incorporated, I suggest that they use a die of the form shewn in Sketch IV. The core of this die could be removed and quenched to 200 C, while the outside form, which should have moveable pieces A and B that could be withdrawn as soon as the metal sets and before major shrinkage begins. As it appears that they wish to cut down their machining to a minimum, the outside form should be slightly oval to allow for sawing the bearing into halves. J M Theale | ||