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 table of starter motor dimensions and weights for 40/50 HP size models.
| Identifier | ExFiles\Box 61b\3\ scan0202 | |
| Date | 10th November 1927 guessed | |
| -1- 86027 X.543. STARTER MOTOR TABLES. 40/50 H.P. size. GROUP C. MOTOR. X.4562. Robert Bosch. X.8620 R.R. E.A.C. DIMENSIONS. Carcase dia. | 4.920 | 5.000 Carcase length | 5.100 | 5.250 Carcase thickness | .300 | .3125 Armature dia. | 2.750 | 3.100 Armature active length | 2.800 | 2.750 Driving end arm. overhang. (") | .850 | .975 Length of comm. conns. excluding comm. spokes. (") | 2.05 | .925 Ditto, including comm. spokes. (") | 2.25 | 1.225 Ratio arm. dia. to carcase dia. | .56 | .62 WEIGHTS (lbs) Complete machine but without pinion sprocket or suspension | 26.0 | 30.9 Arm. without pinion or sprocket | 7.75 | 8.8 Carcase & pole pieces bare. | - | - Armature stampings. | - | - contd. | ||