The correct fuse wire sizes for the electrical installation on the 40/50 car.
| Identifier | ExFiles\Box 61\2\ scan0477 | |
| Date | 12th September 1922 | |
| W/N. X2515 EFC {E. Fowler Clarke - Electrical Engineer} 2/T12.9.22. X.2515 - FUSES FOR R.R.ELECTRICAL INSTALLATION In answer to your M1/H11.9.22, the correct size of fuse wire for the Lucas junction box fuses on the 40/50 car is No.30 SWG. (.0124" dia) copper wire, which fuses in position at about 30 amperes. For the field fuse in the switchbox, the correct size of fuse wire is No.40 SWG. tinned copper wire, which fuses in position at about 5 amperes. These copper wires are now preferred to the tin wires originally standard, except in the case of the fuse wire for the field fuse in the Lucas switchbox of the old type, where the fuse wire clips have to grip the wire, in which case No.40 wire is considered too fine to be clipped nicely, and No.29 SWG wire of pure tin is preferred, which fuses in position at about the same current, namely, 5 amperes. For your convenience samples of these three wires are attached. EFC. {E. Fowler Clarke - Electrical Engineer} | ||
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).