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).
Experiments on starter motor power requirements and the specifications of two different armatures.
| Identifier | ExFiles\Box 34\3\ Scan117 | |
| Date | 15th February 1916 guessed | |
| (Contd). -3- E current. This is the back E.M.F. of the motor for the fixed speed and excitation. We found this to be 78.5 volts. Changes of load on the driving motor will produce change in armature volts, and amperes, but the change in amperes, multiplied by the back E.M.F. as found above, gives very nearly indeed the watts corresponding to the increase of load. Hence we can find the power required to drive the starter motor under any conditions. At first the results obtained were unsatisfactory, chiefly due to variable contact resistance of the driving motor brushes, but by altering these to very narrow softer brushes, starting with a clean commutator, and making various other little improvements to the scheme of working, we have been able to obtain some consistent and satisfactory results. The armatures experimented upon were - No. 1. 45 slot, 45 com bars. 45 coils, 90 conductors. 4 pole progressive wave wound armature. Pitch 23 conductors. No. 2. 17 slot, 51 com bars. 51 coils, 102 conductors. 4 pole retrogressive wave wound armature. Pitch 25 conductors. (Contd)+ | ||