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 dimensions and weights for various 20 HP size starter motors.
| Identifier | ExFiles\Box 61b\3\ scan0205 | |
| Date | 10th November 1927 guessed | |
| -1- 6027 X.543. STARTER MOTOR TABLES. 20 H.P. size. GROUP a.{Mr Adams} MOTOR. | X.4342V C.A.V. SC. | X.4342S Smith SS.{S. Smith} | X.4384 R.R. Coshawk. | X.4342L Lucas. DIMENSIONS. Carcase diameter | 4.625 | 4.500 | 4.500 | 4.500 Carcase length. | 4.725 | 4.10 | 4.500 | 4.350 Carcase thickness | .312 | .375 | .250 | .325 Armature diameter | 2.746 | 2.500 | 2.850 | 3.003 Arm. active length. | 2.900 | 1.650 | 2.500 | 2.600 Driving end arm. overhang. | .80 | 1.10 | .925 | .650 Length of comm. conns. excluding comm. spokes. | 1.15 | 1.45 | 1.10 | .700 Ditto, including comm. spokes. | 1.35 | 1.6 | 1.30 | .850 Ratio arm. dia. to carcase dia. | .59 | .56 | .63 | .67 WEIGHTS (lbs). Complete machine but without pinion sprocket or suspension. | 20.0 | 16.4 | 17.1 | 17.5 Arm: without pinion or sprocket | 8.6 | 6.3 with end plate | 8.1 | 8.3 Carcase & pole pieces bare. | - | - | - | - Armature stampings | - | - | - | - Contd. | ||