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).
Observations on surface cracking and wear of molybdenum alloy drums.
| Identifier | ExFiles\Box 170\2\ img033 | |
| Date | 3rd April 1931 guessed | |
| - 2 - The principal use of the electric furnace is to control the specification with sufficient accuracy. The use of molybdenum as the principal alloy is preferred from experience. (5) Surface cranks are common but not universal. I have seen samples run 30,000 miles which show 1/32 wide cracks, one of which cuts right through the full width of the drum. This was used on brake tests and was removed. Other samples at 8,000 miles show .010" to .020" wide checks 1" to 1 1/2" long all running transversely to the rubbing surface. The cracks appear to have "lips" raised definitely above the rubbing surface, which show bright marking. There may be anything from 3 to 300 on a single drum. In spite of their alarming appearance they do not run through, and there has been no case of a broken drum. It is evidently a heat effect starting at the inner surface. Drums are not now removed for these cracks in view of road experience but the feeling is that the iron is being improved and the effect reduced. There has been some legitimate wear of the drums but no deep scoring and no squeaks. (6) The material is also used for clutch plates. (7) The drums are cast on a basic thickness of 7/16", machined to 1/4" thick with carboloy tools, without cutting fluid. Please give my regards to Mr. Hancock and thank him for his note. Also feel free to call on me for any similar information. We are going to build a bump tester. Would you send me a few useful particulars of drums, cams, speed, etc.? Yours ever, Maurice Olley M.{Mr Moon / Mr Moore} Olley fe | ||