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 of specifications for old and new Scintilla dynamos.
| Identifier | ExFiles\Box 50\1\ Scan260 | |
| Date | 11th June 1927 guessed | |
| X42-90 PARTICULARS OF SCINTILLA DYNAMOS. Old. New. Weights (lbs). Complete machine without pulley. 29.1 27.75 Armature complete without pulley. 8.9 11.12 Air Gap. .99 mm. (.039") .46 mm. (.018") Field Circuit. No. of wound poles. 4 4 Arrgt. of coils. All in series. All in series. Resistance of field 4.6 ohms 9.9 ohms Armature Circuit. Type of winding. Retrog.wave. No. of slots. 15 21 Coils per slot. 3 2 No. of coils or comm. bars. 45 41 Virtual conductors. 90 82 Armature resistance. .327 ohm .301 ohm Comm. & Brushes. Comm. dia. 1.93" 2.28" Comm. length. .975" .725" Brush contact area. 2 x .392" x .392" = .308 sq " 4 x .375" x .275" = .413 sq " Grade of brushes. Morganite link 5 - very soft graphitic. Morganite link C.4728 Carcase dia. 5.500" 5.500" " length. 5.050" 5.500" " thickness. .356" .275" Armature dia. 3.189" 3.700" " active length. 3.275" 2.950 Length of overhang. .875" .775" " " commutator. .850" .725" OK " " " total .1.160" .875" 9.9. | ||