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).
Potential cutout armature jam due to temperature rise and providing diagnostic instructions.
| Identifier | ExFiles\Box 70\3\ scan0244 | |
| Date | 18th June 1925 | |
| To Hm{Capt. W. Hallam - Head Repairs}/NRC.{N. R. Chandler} from EFC. EFC5/T18.6.25. With reference to the attached, the remarks we have to make are as follows :- As far as can be judged from Mr. Bennion's description of this trouble it would appear that one explanation is that rise of temperature is in some way causing the armature of the cutout to jam and be prevented in its inward motion towards the core, which causes the cutout contacts to close. If this alone is the case, running the engine above a moderate speed would provide possibility of damage to the dynamo. Though the gap of .030" is perhaps slightly higher than the average, it would not be considered excessive. We do not specify this gap but it follows as a result of the back adjustment which sets the cutout to go in at a given voltage figure. Mr. Bennion might - (1) Firstly, observe if the cutout contacts are electrically clean. (2) Secondly, observe the cutout while the speed of the engine is gradually increased from below what would normally be cutting-in point. It should then be observed that the cutout armature will draw in, and at the moment of making contact, the ammeter needle should indicate a slight disturbance only. If the moment of contact is delayed by stiction, then at the moment of drawing in, a big change or jump to a big charging current may take place on the ammeter. If it completely fails to draw in, the speed of | ||