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 S.U. carburettor starting methods and a proposed combined mixture/throttle control linkage.
| Identifier | ExFiles\Box 122\4\ scan0222 | |
| Date | 21th March 1939 guessed | |
| -3- It can be considered in this way. Assume in average customer's hands that 95% of the starts made are under conditions round about normal temperature. The S.U. method, therefore, does cater for normal starts in the main, and under abnormal conditions, one or two more attempts on the starter button will have to be made. Our own method of setting caters in the main for the 5% low temperature conditions, so that for the other 95% there is an over rich warm up mixture, which as previously explained is an incentive to freezing up of the starter carb. Fast Idle. The S.U. Company have recently brought out a linkage which is adapted to the normal hand control mixture lever. This is of interest to us because it enables one control on the steering column to operate as mixture control and hand throttle combined. In effect, if this were applied to our normal hand throttle control on the column, there would be three positions. The control is pushed to the top for starting, pulled half way down for warming up and right to the bottom for normal tick over. In the half way position the mixture is full weak, but the fast idle is in action. There are points against such a scheme, from our point of view. The most important being that it may be necessary to use the full range of our normal hand control to get away on steep gradients, as the hand brake will not hold the car under such conditions, see that the right foot is employed on the foot brake. Actually, of course, this phenomenon is confined to temporary stops on such a gradient because obviously the car could not be parked. Conclusions. The purpose of this report, is to line up the limitations of the S.U. Automatic carburetter against our own special requirements. In the case of the starting device, it is considered that we should have had by this time sufficient experience to decide whether or not this is a practical proposition. | ||