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).
Test report comparing sample carbon brushes from British Carbons Ltd. against the standard Morganite brushes.
| Identifier | ExFiles\Box 166\1\ img001 | |
| Date | 2nd September 1932 | |
| X6093 To Hy.{Tom Haldenby - Plant Engineer} from Hs{Lord Ernest Hives - Chair}/Wst. c. E.{Mr Elliott - Chief Engineer} c. Hy{Tom Haldenby - Plant Engineer}/RD. c. Roy{Sir Henry Royce}/Ms. Hs{Lord Ernest Hives - Chair}/Wst.5/AM.2.9.32. BRITISH CARBON BRUSHES We have had on test for some considerable time sample brushes submitted to us by British Carbons Ltd. These brushes were submitted to us as an equivalent to the various types we are at present buying from the Morganite Co. and which are considerably more expensive than the prices given us to by British Carbons. We give below the result of our tests :- (1) Starter Motor. One set of brushes was received suitable for the 20/25 HP. starter motor of an equivalent grade to the Morganite C.M.3 brush now used as standard. A set of these British Carbons brushes was run for 15,000 miles on chassis 19-GIV with satisfactory results, no appreciable difference being noted between these brushes and Morganite. (2) Distributor Carbon Brush. One of the small carbon brushes as used in the distributor head of B.C manufacture was also run on 19-GIV without any excessive wear being noted. (3) Dynamo. The dynamo tests being the most important, were carried out on two grades of brushes. The British Carbon Co. submitted their Grade B. - this being a very cheap grade, and their Grade G.{Mr Griffiths - Chief Accountant / Mr Gnapp} this grade being comparable with the EG.2 brush we now use as standard. Dealing first with Grade G.{Mr Griffiths - Chief Accountant / Mr Gnapp} These were in a size suitable for the 20/25 machine and although supposed to be made of the same quality material as the Morganite E.G.2. they were obviously more graphitic. On the bench they were better than our standard brushes with respect to heating while they were as good as regards commutation and if anything a little quieter in running. After the road test, however, during which the brushes ran 12,430 miles, they were found to have worn at the rate of .0045" to .0103" per thousand miles. Commutation appeared to have been very good. This wear is excessive compared with the average figure of .001" we obtain with our standard brush and for this reason we do not recommend these brushes. The second grade supplied by British Carbons, Grade B. were fitted to a 40/50 machine. In appearance they are similar to our standard E.G.2 grade but they are produced of a finer texture than the Morganite brush. | ||