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).
The design and operating characteristics of fuses for the Phantom II model.
| Identifier | ExFiles\Box 166\7\ img003 | |
| Date | 4th February 1930 | |
| X2515 W/S. To FN. from EFC. c. H.{Arthur M. Hanbury - Head Complaints} EFC1/ADL4.2.30. X.2515. PHANTOM II FUSES. Yours ref. PN{Mr Northey}5/WT11.2.30 and PN{Mr Northey}2/WT12.2.30. The feature referred to in your PN{Mr Northey}5/WT11.2.30 is agreed to be undesirable. It was arranged by West WitteringHenry Royce's home town in the first instance and the question of fuse sizes was taken up with them. Arising out of this, and partly as a result of your own notes, recommendations contained in our EFC2/T22.4.29 (copy to you) were made and the arrangement proposed is now coming on production. This will get over the difficulty referred to by yourself of supplying the accessory distribution board through one of the fuses on the main distribution board. In the circumstances as they are at present, it is agreed to be less objectionable to put a double fuse in 6. than to have this go in normal operation especially as the risk of short circuits on the circuit supplied is relatively very small. In regard to your query as to what we understand by the fusing current of tinned copper fuse wire, the answer in any case is that there is some value of current which may be called the immediate fusing current, i.e. the sudden passage of a current of that magnitude will just cause the fuse to go immediately; then there is also the ultimate fusing current which is of such value that the intermittent passage of this current will ultimately cause the fuse to go. This second current is of considerably smaller magnitude from the first, and the reason of the difference lies in the fact that every time the fuse attains a certain temperature more oxidation of the material takes place and the effect being of cumulative nature the fuse ultimately will not stand the current. The values of these two currents in the case of a single strand of 30 SWG. wire as mounted in the distribution board are 39 amperes and 24 amperes respectively. For your convenience we send you a blue print copy of R.R. Phantom II electrical system which is | ||