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).
Letter discussing the safety and performance of series versus parallel armature circuits for longitudinal crane cross drives.
| Identifier | Morton\M6\ img002 | |
| Date | 6th December 1929 | |
| REG. TELEGRAPHIC ADDRESS: "ROYCE, WEST WITTERINGHenry Royce's home town." {TWO WORDS ONLY. TELEPHONE: CHICHESTER 210. STATION - PASSENGER & GOODS: CHICHESTER - 7 MILES. SOUTHERN RLY. "ELMSTEADHenry Royce's home in West Wittering," WEST WITTERINGHenry Royce's home town, Nr. CHICHESTER. 6th. Dec. 1929. Mr. J.C. Bentley. ROYCE LTD. MANCHESTER. Dear Mr. Bentley, LONGITUDINAL CRANE CROSS DRIVES. I am not sure that I am right when I conclude that you put the fields in series and use this total current through the 2 armatures in parallel, and naturally one concludes this would be the best way because whichever armature revolved the faster would get the less current, and there would be a certain amount of stabilising effect between the two armatures. On looking deeper into the matter one concludes that there is considerable danger in the case of one armature circuit being interrupted, as might easily occur with a blackened commutator, or something wrong with the brushes, a broken wire on the armature, or anything wrong with the connections. It suggests therefore that the 2 armatures in series might be safer. There would however be in this case an equal push at each end of the crane regardless of the resistance, and the end which started first might run on the more quickly. A suggestion that would give some safety is when you fit a brake at each side, and parallel armatures to arrange that the current for the magnetic release of the brake would pass through the armature of the motor on the opposite side - i.e. the motor that got all the current (in the event of failure of one armature circuit) would have its brake on. (1) | ||