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).
Armature winding specifications for a Rotax AT.12 dynamo.
| Identifier | WestWitteringFiles\G\July1921\ Scan3 | |
| Date | 12th July 1921 | |
| To R.{Sir Henry Royce} from EFC. c. to CJ. c. to E.{Mr Elliott - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} ORIGINAL [Stamp] X.1005 - ROTAX AT.12 DYNAMO. We now send you photostat diagram of armature winding of the Rotax AT.12 dynamo, showing exactly the way in which the extra coil (dotted) (over and above those necessary for a simple two circuit wave winding with two coils per slot) is connected lapwise into the armature circuit, so as to enable it to be used instead of thrown away as a dummy, resulting in the use of 28 commutator segments instead of 27. The particulars of the winding are, therefore, as follows :- Type of winding - 4-pole, two circuit retrogressive wave, two coils per slot. No. of slots 14 No. of conductors 672 No. of coils or comm: bars 28. No. of conductors per slot 48. No. of turns per coil 12 Step of coil - 3 slots (1 to 4). Armature resistance, measured between two commutator segments at 90º - .418 ohm at 18ºC. Gauge of winding wire 19 S.W.G. (.041"). Perhaps at the next opportunity you will return this dynamo by car, as now that we know the exact winding, we might carry out some flux investigations upon this machine as suggested by you for the Bosch machine, whose winding [Upside down text at bottom] R.R. 235A (100 T) (S.H. 798. 10-12-20) G 2947 | ||