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).
Technical report on the failure analysis of a 20 HP Dynamo No. 203.
| Identifier | ExFiles\Box 47\4\ Scan224 | |
| Date | 31th December 1925 | |
| 14118 To BY {R.W. Bailey - Chief Engineer} /HM. {Capt. W. Hallam - Head Repairs} from EFC. {E. Fowler Clarke - Electrical Engineer} EFC {E. Fowler Clarke - Electrical Engineer} 3/T31.12.25. 20 HP. DYNAMO No. 203 . GNK-17 - E.G.ELLIOTT, ESQ. We have duly examined this machine and my assistant reports as follows :- "This machine, returned as faulty, is of the old 29 commutator segment type. Solder is thrown from the commutator and melted at the flexible terminals and between the brush box parts. The negative brush flex has become detached from its terminal and it is clear that it cannot have been correctly attached in the first instance. The negative brush itself is badly burnt, although it moves freely in the holder. On the machine as received, the control brush is set 7 to 8° more retarded, i.e. in the direction of higher output, than was initially correct for these machines. It appears from inspection that this control brush has been moved in the direction of increasing the output since first being set by our Production Dept. The insulation of the machine is O.K. There is no badly projecting mica on the commutator. The failure was probably due to very high output combined with faulty negative brush flex which caused the main current to be diverted through the spring." It will be seen from the above report that we ascribe the failure of this machine to a combination of circumstances. (1) The faulty connection of the negative brush flexible - it is very probable that the machine has been run for a considerable time with this connection actually broken. (2) The increased output due to the control brush having been moved from our original position to an extent which, according to our tests, would result in | ||