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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).
Development challenges with an automatic starting device, including 'freezing up' and performance issues.

Identifier  ExFiles\Box 122\4\  scan0220
Date  21th March 1939
  
1036

COPY FOR FILES.

To Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation}        Typed 21.3.39.

AUTOMATIC CARBURATION.

Automatic Starting.

For the past few months a considerable amount of work has been done in this direction. Most of our B.V. development cars have been, and still are, running about with the device fitted, but the B.V. will not go into production with Automatic Starting for the following reasons.

(a) The "freezing up" trouble has not been overcome.

(b) The automatic range of the device has been criticised as being inadequate.

with reference to (a); this problem is well in hand by Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}

With reference to (b), there are certain points which must be settled before much more progress can be made. The most important point being whether the capabilities of the device are such as to fully cover our demands with regard to automatic carburation, and it may be opportune, therefore, to weigh the pros and cons in the light of our accumulated experience with the device.

In the first place let us consider the limitations of the S.U. device.

Its primary function is a starting device, as its name implies, and not a "warmer up".

In actual fact, it gives a richer mixture for starting purposes by means of an auxiliary carburetter. The method is similar in every way to our own starting carburetter, going back a number of years to the Phantom I, because as soon as the engine has started the mixture is weakened slightly. Also, for snap acceleration the richer mixture is available as and when required. The auxiliary carburetter is then automatically cut off at a predetermined temperature leaving the main carburetter to perform its normal duties.

We see, therefore, that with this arrangement we get three stages of mixture which is a compromise, because what is really required is a change in mixture as gradual as the engine temperature, or more correctly, the induction system.
  
  


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