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).
Continuation page of a table detailing specifications for various starter motors.
| Identifier | ExFiles\Box 61b\3\ scan0198 | |
| Date | 10th November 1927 guessed | |
| -3- Starter Motor Tables - Contd. 40/50 size. Group A.{Mr Adams} | | MOTOR. | X.3247 C.A.V. ZC. | X.3161 Lucas A.S10. | X.1058 Bijur A.21. | X.1248 Bosch S.45. | X.2642 RR.17. (C1C) | X.2642 RR.24. (C1C) | | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | | MAGNETIC CIRCUIT | Air gap (inches) | .031 | .015 | .025 | .017 | .025 | .025 | | COMMUTATOR & BRUSHES. | Commutator dia. | 1.750 | 1.940 | 2.000 | 2.125 | 2.436 | 2.436 | | | Comm. length. | 1.150 | .938 | 1.200 | .875 | 1.250 | 1.250 | | | Grade & hardness of brushes. | CM1. Morganite | CM4 Morganite | Contains Cu, C, Zn Harder than CM1. | Contains Cu, C Softer than RR CM.1. | CM1. Morganite. | CM1. Morganite. | | | No. of brushes. | | | | | | | | | Arrgt. of brushes. | 2 at 90º | 2 at 90º | 4 at 90º | 4 at 90º | 4 at 90º | 4 at 90º | | | Brush contact total area for current. (sq. ") | .15 | .13 | .25 | .065 | .75 | .75 | | | Advance or retard of brushes. | | | | | | | EFC. | ||