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).
The operating voltage specifications for a Lucas electrical cutout, comparing cold and hot conditions.
| Identifier | ExFiles\Box 36\4\ scan 179 | |
| Date | 13th December 1920 | |
| Contd. -2- EFC1/T13.12.20. went out with the spring control of the cutout adjustable, but that latterly these have gone out with the adjustment soldered up by the makers. x.3958. We attach for MR. Olley's information a copy of specification of electrical operation of cutout for R.R. car, which specifies the voltage at which the cutout should operate both cold and hot. On the Lucas cutout, however it will be found that if the cold cutting in voltage is adjusted to work between our limit 12.2 and 12.8, the operating voltage when hot will probably be outside the range of 13.2 to 14.2 at the top end. This is because the Lucas cutout gets rather hotter than we like when in operation. It is undesirable to cut in early under any conditions, i.e. as a voltage below that of the battery, because this tends to give the cut-out lever a dithering motion just at the point of cutting-in, due to the reverse serieas current throwing the contact off again. We therefore are of the opinion that if it is possible to make the adjustment, and this be properly carried out, it would be an advantage in some cases to adjust the Lucas cutout to cut in when in the cold condition at 12.2 to 12.4 volt, but not less. The cutting-in speed in the hot condition may then be a little later than given by our limits, but if we were to adjust this so as to bring it within our limits in the hot condition, then the dithering effect spoken of might occur when the cutout is cold. Hence, adjustment, when in the hot condition, to our limits would be undesirable. We have come across Lucas cutouts which cut-in as late as 13.5 in the cold condition and it is possible Contd. R R 236A G(8-16)L.1039 H.S./'H' 11.'19. 2,001. | ||