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 S.S. Starter Motor, detailing gear ratio, motor windings and the armature taper for engagement.
| Identifier | WestWitteringFiles\T\November1928\ Scan034 | |
| Date | 16th November 1928 | |
| To R.{Sir Henry Royce} from EFC. c. PJ. E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} c. Wor.{Arthur Wormald - General Works Manager} Ex. EFC4/T16.11.28. ORIGINAL S.S. STARTER MOTOR. X7625/5513 The gear ratio on EAC.7 is the previous 13 : 1 ratio. MOTOR. We have taken great care to get in all the copper possible in both field and armature windings. We note your agreement to 3/4" longer core and are preparing a set of calculations based thereon. We will also cut down the air gap to the minimum mechanically possible (.010") in the full working position. This appears more possible with the taper armature. We are sending you some torque and flux curves under cover of a separate note. ENGAGEMENT. The armature taper on EAC.7. was 3.100" to 3.000" and on present motor 3.100" to 2.900". We are returning to first taper on new motors in hand (one made). We think that with this taper (3.100" to 3.000") the main armature spring can be satisfactorily chosen in relation to longitudinal pull to avoid thump on engagement without the necessity of a buffer. We anticipate being able to reduce the teazer current and ampere turns with this apparently more correct taper, by using a finer gauge of teazer wire of the same number of turns, thus giving more room for main winding. The thump on engagement referred to took place on teazer current only, i.e. main current not allowed to make. Contd | ||