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 the EAC.II starter motor, specifically the turns per pole and pole core cross-sectional area.
| Identifier | ExFiles\Box 64\1\ scan0187 | |
| Date | 15th September 1924 | |
| To BY/RD. from EFC. X7620 EFC5/T15.9.24. X.8620. EAC.II STARTER MOTOR. Answering your BY/RD1/M415.9.24. we hope this week to have one at least of these motors for test and would prefer, before committing ourselves as to the size of the field core D.70327, to carry out a brake test of the motor and compare this with our calculations. It is true that our calculations indicated 4½ turns per pole, nevertheless in our covering note EFC#/T19.6.23. to R.{Sir Henry Royce} we had suggested that probably R.{Sir Henry Royce} would like to put on 6½ turns, which apparently is the case. The 6½ turns are therefore O.K. As regards the cross sectional area of the pole core, we are not quite clear now just what has happened as regards this. Our original calculations dated 19.6.23 were based upon a rectangular section .940" x 2.45 = 2.30 sq." The cross sectional area indicated in D.70327 is :- .950" x 1.800 + π/4 .950² (i.e. .709)= 2.419 sq" Therefore it appears that these pole cores may be larger than necessary. We cannot now be quite clear whether we have done anything with these cores which would have been suggested from progressive production of polar cross sectional area carried out on dynamo pole cores. Perhaps you can remember. The standardised cross sectional area for the dynamo polee core was 2.535 sq." that is, only a little more than what is at present proposed for the motor, which is a considerably smaller machine. It appears we might desire to | ||