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).
Advantages and disadvantages of an electrically operated automatic choke for a Stromberg carburetter.
| Identifier | ExFiles\Box 123\1\ scan0003 | |
| Date | 23th August 1939 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden} c.c. De. c.c. De/Jnr.{Charles L. Jenner} c.c. Rm{William Robotham - Chief Engineer}/FD.{Frank Dodd - Bodies} c.c. Rm{William Robotham - Chief Engineer}/IMW.{Ivan M. Waller - Head of Chateauroux} STROMBERG CARBURRETER - ELECTRICALLY OPERATED CHOKE CONTROL. To electrically operated automatic chokes generally there are the following outstanding disadvantages:- (1) Since the unit is wired into the ignition circuit the choke begins to open when the ignition is turned on whether or not the engine has been started. This is a snag but does not lead to an impasse, since an engine fitted with a Stromberg carburetter may always be started cold by operating the throttle (accelerator pump). The unit fitted to 11.B.V. receives 6.7 volts approx. which is well within the 4-8 volts specified. With the ignition turned on and the engine not started the choke is fully open in about 7 minutes. Were the engine started up in something under this time, however, the choke would probably open fully since it is mounted offset. (2) When the engine stands after a run it has been thought that the choke unit would cool down much faster than the engine itself, thus closing the choke and making hot starting difficult. On 11.B.V., however, the time taken for the choke to close completely after an ordinary run with moderate underbonnet temperature was just 30 minutes, and even after this time the car started up immediately. (3) The bi-metal unit exercises a very light control. This is almost certain to lead to sticking chokes in service unless great care is taken. Against these disadvantages stand the good points - (1) that the unit is a standard production applicable to any type of carburetter, and | ||