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).
Low safety margin of a new open type dynamo armature fuse on the Phantom III and suggesting an increased capacity.
| Identifier | ExFiles\Box 168a\3\ img448 | |
| Date | 19th January 1938 | |
| Br.{T. E. Bellringer - Repair Manager} c to Mr. c to Rm.{William Robotham - Chief Engineer} (Partially obscured) 6142. Hd{Mr Hayward/Mr Huddy}/SB{Mr Bull/Mr Bannister}9/HR.19.1.38. RE Leslie are you seeing EBJ re DYNAMO ARMATURE FUSE. -------------------------- We are about to commence fitting an open type fuse in the armature circuit on all Phantom III cars, as per Depot Sheet No. Hd.{Mr Hayward/Mr Huddy}371. Whilst this will undoubtedly avoid failures due to imperfect contact, we feel that this particular fuse is running too close to its rated capacity, particularly on the Phantom III. We have no trouble with the cartridge fuses on other circuits and this can only be due to the fact that the capacity of these fuses is 400% greater than the normal load, whereas the safety factor on the armature fuse is only 50% under full load conditions. We suggest that the fusing capacity of the wire to be fitted to these open fuses be increased to, say, 40 amps to give a greater margin of safety. We notice, for instance, that Lucas fit a 35 amp fuse in their dynamo circuit on small cars where the load is considerably less than the Phantom III. Hd{Mr Hayward/Mr Huddy}/SB{Mr Bull/Mr Bannister} | ||