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).
Calculations for armature and field coil specifications including resistance, turns, and wire gauge.
| Identifier | WestWitteringFiles\J\November1922\ Scan119 | |
| Date | 11th November 1922 guessed | |
| -2- Contd. Total number of armature turns = 232 Armature resistance is that of 58 turns in series. Length of mean armature turn (approx) = 13.5" Total length for armature resistance = 58 x 13.5 = 65 ft. 12 Armature temperature considered to be 100°C under continuous working conditions. Resistance per 1000' for 18 S.W.G. at 100°C = 5.9 ohms. Armature resistance (hot) = .065 x 5.9 = .384 ohm. Allow .016 ohm for brushes and contacts giving .40 ohm as taken (Here see table Page 3) Ampere turns required per pole = 478 Resistance of mean turn of field coil = volts per coil ampere turns per coil = 3.4 478 = .00711 Length of mean turn of field coil = 12.25 Ohms per 1000' at 80°C (say) = 12000 x .00711 = 6.92 12.25 18 S.W.G. is 5.58 19 S.W.G. is 8.01 Owing to the relatively low armature resistance it is considered that 18 S.W.G. is the more suitable wire to use. Contd. | ||