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).
Carburettor issues related to slow running plugs, throttles, and jet levels.
| Identifier | ExFiles\Box 42\3\ Scan093 | |
| Date | 2nd January 1941 | |
| .BB Contd :- -2- A tapped boss for this already exists on the carb. and there remains but to provide the front drain pipe. Further to the above the following points arose in discussion with Hs.{Lord Ernest Hives - Chair} and Mr. Lovesey the following morning :- (a) SLOW RUNNING PLUG. It has not been found possible up to the moment to produce the RR. fixed type of plug to give a sufficiently close degree of uniformity of running on all carbs. We notice in Strombergs manual that the fixed plug with adjustment of the air bleed is said to affect the whole speed range about equally from the lowest idling to about 800 r.p.m., whereas with the later or moveable plug type the adjustment is strongest at very low speeds, and disappear entirely at 600 or 700 r.p.m. (b) THROTTLES. The earlier Stromberg's were fitted with duralumin throttle spindles and spring loaded end collars to provide some extra friction. The latest Stromberg's have what is apparently monel metal spindles, and glands filled with some sort of packing like Lion packing where the spindle has to come through for a drive. Otherwise the bearings made blind. These packings set up a fair amount of friction. It would appear that there is the possibility of flutter and wear at this point, eventually leading to slow running troubles. Hs.{Lord Ernest Hives - Chair} thinks we may require some friction on the throttle spindles. (c) JET LEVELS. The Claudel Hobson gets its acceleration by breaking into the column of solid fuel with a plentiful supply of emulsion air, and then counteracting the subsequent weakness produced at full throttle by means of the power jet. The Stromberg gets its accelerations by having the petrol level as near to the top of jet as possible, and we notice that the air bleed is carried high up behind the choke tube so that the emulsion discharge holes shall be the first point to spill. As we do not wish to use the power jet we must keep our level as near to the top of the emulsion discharge holes as possible, but with our present construction we lose about .3" owing to the guard tube being the first point to spill. This suggests an alternative construction in which the air stream is lead up through drillings to an air chamber in the top of the jet and then down again, thus in effect raising the guard tube above the emulsion discharge holes. This increases the overall dia. of the jet by about .187". contd :- | ||