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).
Technical note detailing carburetter design changes, including the internal section and reversed throttle action.
| Identifier | ExFiles\Box 102\1\ scan0235 | |
| Date | 27th December 1934 | |
| -2- Internal Section. In returning to the square section for this type of carburetter, the effective capacity has been increased. This has been made possible by use of the R.R. type of damped air valve (standard). At the time when this carburetter was being launched into production, the "round" section had already been developed for maximum "velocity", when the damped air valve arrived. Time limit at this stage prevented its relative value from being used to the fullest advantage. Reversed Throttle Action. From the drawing EX.15729 it will be seen that in order to bring about the above, a compromise was struck between moving the throttle edge mechanism forward, and the throttle spindle back, but sufficient clearance was not allowed for the overhang of the cylinder head lip, and a fairly thick packing washer had to be inserted behind the flange. If this flange is moved forward as shown in ink on the attached drawing, the part in question will be clear. The changeover from the throttle edge to the main jet takes place almost as soon as the throttle is opened, and is thus put out of the normal speed range of the engine for ordinary road work. In this way, we are able to maintain better control over the low speed metering, as will be seen from the following. In the present production carburetter, the L.S. choke is set at approx. 750 r.p.m. running light; under the new conditions the L.S. choke is used to control the mixture for slow running, in conjunction with the eccentric adjustment at the throttle edge. We can say therefore that the L.S. choke is doing comparatively more work at the "initial setting speed", and a much finer setting can be obtained. Hs{Lord Ernest Hives - Chair}/C.T.Salt. | ||