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).
Fuse wire failures in a Lucas switchbox due to heat from the cut-out windings and potential solutions.
| Identifier | ExFiles\Box 61\2\ scan0427 | |
| Date | 4th December 1920 | |
| X.295 EFC2/T4.12.20. To EP{G. Eric Platford - Chief Quality Engineer}/Thn. from EFC. c. to Ey c. to Ey/WER. X.2515 - FUSE WIRE FOR LUCAS SWITCHBOX. X 3749 With reference to your EP{G. Eric Platford - Chief Quality Engineer}/Thn12/F3.12.20, it would appear that the fuse failures we have experienced in service have been assisted to a greater degree than would have been anticipated by the heat generated by the cut-out windings inside the switchbox, this being especially the case as you state that these do not so much occur at first, when the box and dynamo are cold and the field current naturally higher, as later when, although the field current is lower, the box is heated up. Under any reasonable conditions of temperature in the box, the wire with which you are now supplied should undoubtedly be correct, and we would suggest that before you actually change the fuse wire on cars which have been sent out, you leave the matter for say a week to actually see if any failures do occur, which we do not think likely. If they do not we think then it would be quite safe to change the old wire for the wire now provided. In the meanwhile we will order up experimentally some wire of the same material but of one gauge (No.29) larger in case we shall deem it necessary eventually to go to this size. Is there at the moment any sort of ventilation in the switchbox ? We do not think there is, beyond the hole where the wires enter, and it might be quite a good idea to have a hole in the top of the box at the back of the instrument dash-board to allow the escape of the heated air which naturally | ||