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).
Analysis of cut-out specifications and a comparison of C.A.V., Lucas, and Smith lighting dynamos.
| Identifier | WestWitteringFiles\C\August1919\ Scan46 | |
| Date | 13th August 1919 | |
| Contd. -7- EFC1/T13.8.19. CUT-OUT. Volts on shunt coil to cause cut in at 20° C = 12.2 Amperes = .115 resistance 106 ω Volts to allow contacts to drop apart = 9.95 Amperes . = .094 Reverse amps. through series coil to allow contacts to fall apart when 12.2 volts are applied to shunt coil = 1.60 Series coil volts = .029. We attach table of analysis of results of tests of C.A.V., Lucas and Smith lighting dynamos. The Smith dynamo has four brushes as against three (sets) on the Lucas, but is simpler in switching and wiring as it only requires three conductors to be brought away from it as against four for Lucas. For a given out-put at high speeds it has a much better low speed performance than Lucas, with only a slight additional weight (3 lbs). If the field circuit is opened, all is dead on the Smith dynamo. This is not the case with the Lucas, as it excites on the control winding. Complete protection of the dynamo in case of cut- out failure (and charging switch left on) requires one fuse less for the Smith than for the Lucas. Contd. | ||