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).
Various forms of automatic chokes for carburetters, including Stromberg models and electrically operated thermostats.
| Identifier | ExFiles\Box 126\4\ scan0108 | |
| Date | 4th June 1938 | |
| -3- Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation}4/MH.{M. Huckerby}4.6.38. too thin it cut through the bellows. This is supposed to be O.K. now, but we shall, of course, check up on the instruments supplied. Considering (c) the Stromberg Carburetter. There are various forms of automatic choke. The most general pattern is the D.B.42, which is a modified version of the carburetters standard on our 25/30 and production Wraith. We cannot very well use this type of automatic device on Wraith as it depends for its action by mechanical connection with an exhaust heated bi-metal strip. On Wraith, the exhaust manifold is on the other side of the engine to the carburetter. Another similar model, more suitable to our requirements incorporates an electrically controlled thermostat, in place of the exhaust-heat control. This type, however, does not provide the fully progressive action of the D.B.42. The last mentioned and the S.U. carburetter with Smith's thermostat are similar in action in as much as they both provide fully automatic carburation in the true sense of the word. Coming back to the electrically operated thermostat. This works purely on a time element. As soon as the engine is switched on, the electrical heater begins its work, and so the choke gradually opens. During this operation a compensating device is provided for cold get-away; but the time element is still there. For instance, suppose the engine was switched on, but the starter button not pressed straight away; the electrical heater still does its work. In fact, going to the extreme, if the starter button is not pressed for a period of some minutes (dependent on initial setting) the choke would be wide open on a cold engine and it would be very difficult (if possible) to start the engine. It can be said, therefore, that although this type of starting is not fool-proof, one can provide a setting which is a fair compromise. When available, a Wraith car will be tried with this scheme, and so the necessary information will be available. Attached to this report is the correspondence which has taken place to date, with descriptive data. In the April issue of The Automobile Engineer appears an article which deals more fully with some of the devices mentioned. Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation} | ||