Two.fuel Carburetters and Fittings, XIV.
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The Bi4uel Carburetter (Hamilton's Patent) in Use on Heavy Vehicles for Some Years is Now Likely to be Made in Increased Quantities.
The Bi-fuel carburetter is not new. It has been used by various commercial-vehicle owners for some years, and is also fitted by the Leyland Co. -to many of their machines, particularly to those -which are intended to be exported to localities where petrol is not readily obtainable. Bi-fuel Carburetters, Ltd., of Euston Buildings, George Street, London, N.W., has beep, so to speak, jogging along, turning a small number of these-carburetters out, not perhaps enough to keep a large establishment going with this one business alone, but sufficient to meet the pre-war demand for two-fuel fittings. The company has, however, during the meantime, gathered much valuable experience as to the vagaries of paraffin and Other fuels as used on internal-combustion engines. The present crisis, therefore, finds it ready to come forwaed with a carburetter brought to a very fair stage of practical usefulness.
.The name of the device—Ei-fuel—expresses Ito a, considerable degree the utility of this carburetter. It is, as a matter of fact, expressly designed toodrait two fuels, each mixed with the requisite quantity of air, and the two resulting gases afterceards mingled together in suitable proportions which can be§regulated while running to suit atmospheric or other conditions, to the engine. In brief, it may be said to consist of two carburetters, each complete with float chamber, jet. and air-regulating device, both being coupled up to the mixing chamber, which also serves as the cylindrical throttle chamber.
As regards the float chambers there is nothing oul of the ordinary. They are placed immediately below the mixing chambers, and the jet is concentric with the floati in each .case.: Each mixing chamber .contains an automatic weighted valve, which is piston shaped, and slides in a cylinder serving as a dashpot, preventing its too rapid motion and oscillation under the uneven suction of the engine pistons. Each valve
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carries a .fuel needle, which is taper in fOrm and 'serves to' regulate the size of the orifice from the jet. The removable rings which are shown on the sectional illustration take the place -of what would in any other carburetter be termed the choke tube. The standard size is such as to give a constant ratio of weight and air to weight of fuel of 15 to 1. Larger and smaller sizes to give a certain percentage increase or decrease of fuel can be supplied if -desired. One important feature of this carburetter is the throttle. This consists of a cylindrical casing, having openings communicating with the two mixing chambers, and an outlet leading to the vaporizer and thence to the engine induction pipe. Within this casing is mounted a cylindrical sleeve, capable of movement in -either or both of two directions. It may slide longitudinally, and in this way regulate the -relative openings to the mixing chamber, or it may rotate, and thus control the double opening frora both, and it thus acts in the -throttle valve proper. A study of .the drawing will enable the. reader to grasp that, as it is shown there, the Port opening into the petrol chamber is fully. open, whereas that to paraffin is closed.This might be termed the starting position. So soon as the engine is warm the cylindrical throttle should be moveeto the right, when a proportion of paraffin commences to be used. By pulling itas far as' it -will go to the right hand, the paraffin port. is fully. opened, and that for petrel almost, but not quite, closed„ Admitting 20 per cent. of petrol and, 80 per cent. of. 'paraffin. Any intermediate position may be found between, these extremes to give any desired ratio of mixture. If desired,' the travel of the sleeve may be altered, so that petrol is entirely cut out