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).
Bench tests of open type fuses, comparing their disadvantages with those of cartridge type fuses.
| Identifier | ExFiles\Box 166\7\ img079 | |
| Date | 15th September 1937 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/RC.{R. Childs} c. By/RD. c. DE. Rm{William Robotham - Chief Engineer}/RC.{R. Childs}4/MH.{M. Huckerby}15.9.37. 6071. Re Distribution Board Open Type Fuses To R.R.Sch.1082. We have completed bench tests on the above type fuses. In testing these fuses it is realised that there adoption would, in effect, be reverting to an earlier form of fuse. The objections to the open type fuse which led to the introduction of the cartridge type were as follows :- (1) Failure as a result of the cutting of the wire by tightening of the clamping screw. (2) Variation in the fusing current due to the cooling of the fuse by contact throughout its length with the fuse carrier. (3) Variation of the fusing current due to difference in length and tension of the fuse wire. Experience with the cartridge type of fuse has shown that it has the following disadvantages :- (1) Intermittent or permanent failure due to bad workmanship, such as the use of dirty materials resulting in a bad connection between wire and cap. (2) Variation in fusing current, due to the wire sagging, and touching the glass tube, with a resulting cooling effect. (3) Cracking and discolouration of the glass, through the hot wire coming into contact with it. (4) Deterioration of the wire through being stressed, as the result of the cap becoming loose on the glass tube. The frequent occurence of faults of the first kind, on the cartridge type fuse has made the change in design necessary. We personally have pointed out this weakness to the makers, and have repeatedly urged them to improve the fuse: | ||