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).
Comparative table of specifications for various starter motor models.
| Identifier | ExFiles\Box 61b\3\ scan0200 | |
| Date | 10th November 1927 guessed | |
| -2- Starter Motor tables - Contd. MOTOR. X.2642. RR.45a. clc. X.3082. RR.45a. clc. X.1058 Bijur I.A.D. X.4007 U.S.A. Bosch. X.1086 Westinghouse. X.4341. C.A.V. S.B. FIELD CIRCUIT. No. of wound poles. 4 4 4 4 4 4 Size of conductor. .370 x .056 .250 x .116 .250 x .116 - - - No. of turns per coil. 13.5 8.75 - - - - Arrgt. of coils. 4 in S. 4 in S. All in P. All in S. 2 S. 2 P. 2 S. 2 P. Resis. of field circuit (ohms at 18º C). .0204 .0085 .0023 .0044 .0061 .0019 ARMATURE CIRCUIT. Type of winding. Ret. wave. 2 circ. Prog. wave. 2 circ. Ret. wave. Ret. wave. Ret. wave. Prog. wave. No. of slots. 45 45 33 27 25 15 No. of conductors. 90 90 66 108 50 60 Conductors per slot. 2 2 2 4 2 4 Coils per slot. 1 1 1 1 1 1 No. of coils or comm. bars. 45 45 33 27 25 15 Turns per coil. 1 1 1 2 1 2 Virtual conductors. 90 90 66 54 50 30 Winding pitch in virtual conductors. 21 & 23 23 15 & 17 13 11 & 13 7 & 9 Step or winding pitch in slots. 11 11 coil 12 com 8 7 coil 6 com 6 4 Size of conductor (sq. inches). .0089 .0089 - - - - Resis. of arm. circuit between appropriate comm. bars (ohms at 18º C). .0114 .0116 .0028 .0162 .0038 .0060 Ratio of field resis. to arm. resis. 1.79 .732 .822 .272 1.60 .317 | ||