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).
The testing of a Japan III starter motor, detailing issues with windings and proposing modifications to the armature.
| Identifier | ExFiles\Box 179\3\ img138 | |
| Date | 1st April 1932 | |
| SECRET. ORIGINAL E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Wst. c. to By c. to By/Rd. c. to Wor.{Arthur Wormald - General Works Manager} Hs{Lord Ernest Hives - Chair}/Wst.3/MA.1. 4. 32. X6091 JAPAN III STARTER MOTOR. We have now tested this motor and with the heaviest gauge main field winding the motor is inefficient and the stalling torque low. Also the teazer winding excitation is insufficient to draw the motor into full engagement on normal voltage. In order to get the teazer working satisfactorily the gauge wire should in the first instance be altered to 18.SWG keeping the same number of turns if possible. With regard to the main field we think the 4½ turns of copper bar to D.53222 satisfactory to begin with if they can be accomodated with the coarser gauge teazer winding. The first winding to D.53139 was very unsatisfactory as expected. Coming now to the armature we find this to have 37 slots whereas our calculations specified 35. In order to keep up the slot magnetic permeance which with these motors seems to have a greater significance than armature copper losses etc, it is necessary to arrange the number of armature slots at an absolute minimum consistent with torque-speed calculations. We consider an armature of 33 slots but with conductors having the same cross-section of copper as the present armature would give us a better speed-torque characteristic. Furthermore if we could increase the speed of this motor for a given torque we should also get a much better characteristic and efficiency. We consider the J.{Mr Johnson W.M.} 3 gear ratio is too high and would suggest for consideration a gear ratio more like the 40/30. We should be glad therefore if By.{R.W. Bailey - Chief Engineer} will arrange for another armature to be instructed for experimental trial. | ||