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).
Investigation report into a faulty dynamo from chassis 32-RC.
| Identifier | ExFiles\Box 70\3\ scan0282 | |
| Date | 14th March 1927 | |
| EFC. P.C.128. Mar. 14th 1927. FAULTY DYNAMO VE.75 OFF CHASSIS 32-RC.{R. Childs} The above dynamo was sent to us with the complaint that the solder had run. From an investigation the following points were noted :- (1) The insulation, tested on the A.C. mains, was broken down at the control brush-holder, due to carbon dust. (2) The negative brushes were found to be reversed in the holders. (3) Both positive and negative brushes were found to be well bedded and polished, but rather worn. (4) The control brushes were blackened and well worn. These were found to have the early setting of 120º from main positive brush. (5) The solder had been melted from the commutator connections, which were covered with a blue-grey deposit suggestive of excessive sparking. (6) Overheating of the armature appeared to have been local, at the commutator only, but the field winding also had been overheated. This machine probably had a high output, as a result of its control brush setting, which may have caused melting of the solder, but most of the evidence points to the trouble having been caused by the negative brushes being taken out and replace the wrong way round. The bedding of the negative brushes in such a case would be bad, and consequently the output excessive. Brush chattering would also have occurred, which would result in intermittent open circuit conditions, accompanied by very bad sparking at the negative and control brushes. We return the machine herewith. EFC. | ||