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).
Assistant's report on the investigation of a faulty chassis dynamo.
| Identifier | ExFiles\Box 70\3\ scan0307 | |
| Date | 1st September 1927 | |
| To EY. from EFC. c. Mr. Brock. X878320 EFC1/T1.9.27. 40/50 CHASSIS DYNAMO NO.OR.75 EX 99-MC. The following is my assistant's report on the above machine which is now being handed to EY. "The above machine was sent to us with a complaint of solder having run. This is the second time that this machine has been sent to us on account of it having thrown the solder from the commutator connections. On the previous occasion (See EFC2/T4.1.27.) when the machine was returned to us Ex chassis 103-MC) there was evidence to show that the failure was due to bad contact at the cutout points. Amongst other things, it was found the, that the machine had the early control brush setting of 120°. As the result of an investigation this time, we find that the machine still has the early C angle of 120°, and we can only conclude that melting of the solder was brought about by overheating, as the result of excessive output, due to this control brush position. It appears that, at the moment of the solder being thrown, a break occurred in the armature winding, due to an end connection becoming loose, causing severe flashing at the commutator. Severe flashing is throught to have taken place, as the commutator connections were found to be covered with black, and bluish grey deposits. The armature otherwise appeared to be alright. Both positive brushes had been removed at some time, and an attempt made to re-bed them. The bedding of these was very bad. The control and negative brushes were somewhat blackened and pitted, while the commutator had the appearance of having been partially cleaned. The field coils seem to have been overheated. Carbon dust had bridged the insulation of the positive brush holder, causing a breakdown. Some of the rivets securing the insulating band inside the end cover were found to be loose." EFC. | ||