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).
Page of calculations for motor speed, resistance, and armature specifications.
| Identifier | ExFiles\Box 62\1\ scan0140 | |
| Date | 2nd June 1933 guessed | |
| -2- = 65 x 2 x 10^8 ------------------------------------- 1.41 x 4 x 199 x 10^3 x 156 = 74 Suggests trying a 37 slot armature with 37 coils one turn per coil. Motor speed 720 R.P.M. Back E.M.F. = 199 x 10^3 x 74 x 720 x 4 --------------------------- 60 x 10^8 x 2 = 3.53 volts. Therefore ohmic E.M.F. = 8.80 - 3.53 = 5.27 volts Motor resistance R = 5.27 ---- = .0338 ohms. 156 Assume field resistance to be .0060 ohms. Then armature resistance plus brush resistance = .0278 ohms. Assume a brush resistance of .0070 ohms Then armature resistance = .0208 ohms. Resistance of one armature turn = .0208 x 4 ---------- = .00225 ohms 37 Length of one armature turn - 12" approx. Resistance per 1000' - 2.25 ohms. ohms of copper per 1000' at 20°C. = .00815 cross sectional area = .00362 sq.in. | ||