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 motors for a small car.
| Identifier | ExFiles\Box 51\5\ Scan036 | |
| Date | 23th May 1927 | |
| X.543. STARTER MOTOR TABLES. (Additional sheet II - Motors for small car). Handwritten top center: X4342 Handwritten top right: SHEUY | STARTER MOTOR. | X.4342V. C.A.V. SC. | X.4342S. Smith SS {S. Smith} | X.4384. R.H. 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 | | **END CONNECTIONS** | | | | | | | | Length of overhang at driving end. | .80 | 1.10 | .925 | .650 | | .850 | .975 | | 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. | ||