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).
Inspection and testing procedure for a main switch unit, detailing contact gap measurements and coil current checks.
| Identifier | ExFiles\Box 70\4\ scan0150 | |
| Date | 1st March 1926 | |
| Contd. -2- EFC/T9.3.26. (5) The porcelain resistance carrier should be examined for presence of cracks. II. MAIN SWITCH UNIT. (1) Assuming that the main copper contacts have been duly corrected, if necessary, it should now be ascertained that with the switch in the "off" position the mean gap of the copper contacts is .065+5/-5. (2) Now adjust the relation of the copper and carbon contact arms until with the carbons held just in contact the mean gap of the copper contacts is .020+10/-5. (3) The various gaps should then all be according to the following table :- Position of switch. | Core to armature stop. | Copper gap. | Carbon gap. --- | --- | --- | --- Off. | .057+5/-5 | .065+5/-5 | .062+10 . Carbons just in contact. | .032+5/-5 | .020+10/-5 | 0 Coppers just in contact. | .020 | 0 | 0 (4) The coil of the main switch shall be connected to the terminals of a six-volt battery, through an ammeter, and the amperes taken by the coils (with non-inductive resistance in parallel) at 6 volts at atmospheric temperature, shall lie within the limit 2.20 and 2.40 amperes. Contd. | ||