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 analysis of a badly worn brake drum, attributing wear to the increased size of graphite flakes.
| Identifier | ExFiles\Box 13\1\ 01-page64 | |
| Date | 19th October 1934 | |
| COPY To BY.{R.W. Bailey - Chief Engineer} RHC.{R. H. Coverley - Production Engineer} HL1/AG.19.10.34. Laboratory Report No.L3115. Re: Brake Drums. R.H.C. Submitted to us a Brake Drum which was found to have worn badly on a 10,000 miles test. The material was analysed, and the following results obtained:- Combined Carbon ... 0.80% Manganese ... 0.95% Titanium. ... Nil Silicon ... 1.49% Sulphur ... 0.05% Phosphorus ... 0.03% Nickel ... 0.92% We do not think that composition is responsible for wear. Hardness tests were carried out on a piece cut out right across the drum. The Brinell figures obtained varied from 210 in the middle to 223 outside. A figure of 226 was obtained on both the worn and unworn inner surfaces. Microscopical examination showed that the size of the graphite flakes are much larger than in the original Lake and Elliot Brake Drum. See our report L2346 of 1.3.32 and attached photomicrograph Al,156. It is to this increased size of the graphite that we chiefly attribute the wear, and it has probably been produced by too slow a chilling of the cast iron. This is confirmed by an open-grained fracture. We also think that the low hardness figures as compared with 256 on the original material will accentuate the wear. Hl. | ||