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).
High-speed dynamo testing to reduce brush and commutator wear for Peregrine and Bentinck engines.
| Identifier | ExFiles\Box 62\3\ scan0331 | |
| Date | 23th February 1933 | |
| 86142. To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Wst. c. to Eg. Wor.{Arthur Wormald - General Works Manager} c. to S. Da.{Bernard Day - Chassis Design} c. to Ry. Hdy.{William Hardy} Hs{Lord Ernest Hives - Chair}/Est.2/MA.23.2.33. HIGH SPEED RUNNING ON DYNAMO FOR PEREGRINE AND BENTINCK. Owing to the condition of the dynamo off the last 10,000 mile test Peregrine chassis due to its high speed running, we have been carrying out laboratory tests at high speeds in order to determine the brush and commutator wear and to take steps in order to reduce the brush wear to normal. The average wear of dynamo brushes after a 10,000 mile test previously has only been of the order of .010" to .020" per brush, but the Peregrine dynamo brushes had worn down over .100". In order to confirm this result, we ran the identical machine fitted with new brushes for an equivalent run of 6000 miles on the bench at speeds ranging from 7000 to 6000 R.P.M. Towards the end of the run at 5000 R.P.M. the dynamo failed due to the commutator solder having "thrown" occasioned by the bad condition of the brushes and commutator surface. The average wear of the brushes for the duration of this test was found to be .100". Following the results of this test the dynamo to engine speed gear ratio was reduced from 1.5 to 1.2 and a further test was made with the same machine overhauled and fitted with new brushes, running at 5000 R.P.M. for 5000 miles. This time the dynamo did not fail but the commutator was found to be in a poor condition and the brush wear was still excessive, being on the average .120", this being approximately the same as before. We therefore fitted a new set of brushes of a new grade manufactured by The Morgan Crucible Co., called Type ECO. These brushes had a slightly higher current density, lower coefficient of friction and higher contact drop. As these factors were all in favour of improved commutation we anticipated a considerable reduction in wear. | ||