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).
Comparison of an experimental starter motor's performance against the standard production motor.
| Identifier | WestWitteringFiles\G\June1921\ Scan56 | |
| Date | 22th June 1921 | |
| Contd. -2- EFC1/T22.6.21. Comparing the curves on the torque base of the experimentally made motor and standard starter motor, it will be seen that the performance of the Experimental motor is slightly better. This motor was specially constructed in the Expl. Dept. and the clearance limits, air gap, etc. would be more exact, resulting in a better job electrically. On the curves on the torque bases the approximate working points on the 40/50 chassis are indicated as being equivalent to a torque of 55 lb-inches on the motor armature (with 100% motor epicyclic efficiency), i.e. 1155 lb-inches on the engine. This is for the moderately cold condition after standing overnight. The remaining quantities can be read off on this line, and are for the production motor, as follows :- Motor volts.................. 9.5 Amperes...................... 120 Elec. H.P.................... 1.53 Motor speed.................. 980 Engine speed................. 42... B.H.P. (on chain wheel).. .88 Efficiency (motor and motor gear)..... .575 A standard volt-ampere battery and lead characteristic for starter motor tests has been decided upon which allows 1 volt drop on the motor terminals (from 12.0 volts) for every 50 amperes of current taken; e.g. at 175 amperes, the motor terminal voltage on this reckoning would be 12.0 - 3.5 = 8.5 volts. It will be seen that the voltage drop actually experienced in these brake tests corresponds very nearly to this standard. Previous brake efficiency tests, e.g. on the Lucas A.510 motor, reported in our EFC6/T18.2.18 on the C.A.V. type ZC starter motor reported in our EFC1/AT2.3.18, and on the old type R.R. starter motor (a) with field coils all in series, and (b) with field coils two in series and two in parallel, were taken under more favourable volt-ampere characteristics than this, namely one in which the voltage at 200 amperes was about 8.8 as against 8.0 as at present. That has given those other motors a slight relative advantage in the tests. In testing further motors, the standard volt ampere characteristic will be adhered to. v.{VIENNA} Contd. | ||