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).
Examination and test report for Dynamo No.69 from chassis 40-G-2, Pirie.
| Identifier | ExFiles\Box 47\4\ Scan182 | |
| Date | 9th May 1924 | |
| To EY/HM.{Capt. W. Hallam - Head Repairs} from EFC. X.4383 EFC2/T9.5.24. X.4383 - DYNAMO No.69 EX CHASSIS 40-G-2. PIRIE. We have now completed the examination and test of this dynamo. This is quite an early machine and it is difficult to diagnose the original fault exactly, but judging from the fact that we found a certain amount of mica projecting between the commutator segments, we are of the opinion that the trouble has arisen initially due to the old and inefficient method of undercutting. It did not appear that the control brush was in such a position that the output would be excessive with normally correct bedding. In order to attempt to demonstrate that the throwing of the solder was due to heating which itself was due to bad commutation, and not to broken battery circuit, we in the first instance had the commutator connections re-soldered, without otherwise doing anything to the commutator. Whilst, however, the connections were temporarily removed, the commutator (on test) showed bad leakage from segment to segment. In order to show that the machine might throw the solder from the commutator connections, it has been run on a somewhat exaggerated terminal volt-ampere characteristic in comparison with the same thing done on a normally correct machine, and it was found that the temperatures attained in the two cases under similar conditions, were 74°C in this case and 71.5°C in the standard case. (N.B. A few degrees difference on the carcase may mean a considerable number of degrees difference at the commutator). In these circumstances it was a fact that the standard machine threw no solder at all, whereas there was evidence of the solder just having reached the plastic state on two of the connections on the customer's dynamo. This rather confirms our opinion that the trouble is at the commutator. There is no real evidence that the failure of the machine has been due to a broken battery connection, and in the circumstances it does not seem that we can do otherwise but rectify this under an A.T.D. No. in Test condition We return the machine, to EY. herewith, together with the original correspondence. EFC. | ||