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 Watford and Lucas magnetos, including ranges, timing, and distributor dimensions.
| Identifier | ExFiles\Box 40\2\ Scan204 | |
| Date | 13th June 1927 | |
| Contd. -3- EFCL/13.6.27. respectively for the Watford and Lucas magnetos. The ranges as set by the makers were found to be :- Watford 50° Lucas 60° N.B. Our General Specification asked for "not less than 58° if possible". R.{Sir Henry Royce} in his note to Mr. North of the 26th April asked for 55°, i.e. 38° on the crankshaft. Taking the same datum, we find the breaks to occur as follows :- Advanced position. Watford 96.5° Lucas 96° Retarded " 147° " 156°. The periods of make are respectively for the Watford 123.5° and for the Lucas 103.5°, corresponding to make ratios of .69 and .575 respectively. (5) The relative distributor dimensions on the two machines, (for both the wipe distributor and jump spark distributor in the case of Lucas) have been compared, and also compared with our suggested relative distributor dimensions derived from first principles. The figures are given for comparison in the table below, and are only relative, taking the distributor pitch as 1.000. The actual diameters of the distributor tracks are :- Watford 2.400" Lucas 2.500" Contd. | ||