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 specifications for various starter motors for small cars.
| Identifier | ExFiles\Box 61b\3\ scan0191 | |
| Date | 23th May 1927 | |
| X1543 [faint handwritten text top right] X.543. STARTER MOTOR TABLES. (Additional sheet II - Motors for small car). STARTER MOTOR. X.4342V. C.A.V. SC. X.4342S. Smith SS{S. Smith} X.4384. R.R. Goshawk X.4342L. Lucas X.4562. Robert Bosch. X.8620. Sequence CARCASE. Diameter: 4.625 | 4.500 | 4.500 | 4.500 | 4.920 | 5.000 Length: 4.725 | 4.10 | 4.5000 | 4.350 | 5.100 | 5.250 Thickness: .312 | .375 | .250 | .325 | .300 | .3125 ARMATURE. Diameter: 2.746 | 2.500 | 2.850 | 3.003 | 2.750 | 3.100 Active length: 2.900 | 1.650 | 2.500 | 2.600 | 2.800 | 2.750 Length of overhang at driving end: .80 | 1.10 | .925 | .650 | .850 | .975 END CONNECTIONS Length of commutator connections Excluding com. spokes: 1.15 | 1.45 | 1.10 | .700 | 2.05 Extra length to accommodate sliding arm. | .925" Ditto Including com. spokes: 1.35 | 1.6 | 1.30 | .850 | 2.25 | 1.225" RATIO:- ARM:DIA / CARCASE DIA.: .59 | .56 | .63 | .67 | .56 | .62 23.5.27. | ||