Two-fuel Carburetters and. Fittings. XI
Page 4
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The Smith-King Paraffin Carburetter is an Automatic Two4uel Instrument after the First Four Minutes. of the Day.
Undoubtedly the keynote of the Smith-King paraffin-and-petrol carburetter is simplicity.. There are no three-way cocks for the purpose of admitting the proper fuel to the carburetter at the right time. The driver is not troubled to make this change, neither does the decision as to when the change is advisable devolve upon him. Petrol is automatically cut off, and paraffin supplied at the right Moment. The complete apparatus is built up on the wellknown Smith four-jet carburetter, which has been.giving service both on touring cars and commercial vehicles for over three years. It is by taking advantage of the. special design of this component, which was described by us on 19th June, 1913, that the good results obtainable with the Smith-King instrument are Made possible, Each of the four jets is provided with its own choke tube.; number one is the largest, and comes into Liss) immediately on starting the engine ; it remains in Itsa so long as sloW running only is required. On speeding up, however, the inereased suction lifts the cylindrical weight, which may be seen in the photographic section of the carburetter which we reproduce.. ThQ effect of the liftingof this weight, which is, really a sleeve covering the ports loading to the four jets, is to uncover in turn the second, third and fourth jets, with the result that at high speeds all the four are in operation 'supplying petrol at once. As the speed slackens, the Weight 'drops and covers one Or more of these jets, and in consequence: :the mitture is graduated exactly to meet requirements of the engine.
By means of a slight alteration to this carburetter and the addition of a seconcl,float chamber, it has been ingeniously adapted is use paraffin as afiteh The petrol float chamber is connected only to the
number one jet; that for paraffin, which is hot-water jacketed, supplies jets numbers, two, three and four. It will be gathered that even without any alteration in design this carburetter could now usefully be adapted as a paraffin carburetter with the addition of a heated induction pipe. Petrol would be availal.11e for starting, and for ordinary running the fuel would be for the most part para.ffin. However, by means of an ingenious re-arrangement of number one jet, the choke tube for which is continued up the centre of the carburetter so that the rich mixture makes its exit through some small holes a short distance above the 'sliding weight, the petrol feed is entirely cut off and ceases to operate so soon as the second Jet is available for use by the lifting of the same weight.
In consequence of this arrangement, all that is needed is that, shortly before colamencing a journey, on starting up, the taps from both petrol and paraffin tanks should be opened. The engine is started and kept turning Over slowly, so that only the first jet is utilized, for three or four minutes, until all is quite warm. It is then possible. to leave the shed and continue to run all day -without there being any evidence to show that anything but pure petrol is being used throughout. The disadvantage of paraffin for general use, inasmuch as it does not allow of slow running on top gear in traffic, is by these ingenious means overcome, since, when the engine-speed drops below
certain point, the number one jet is again re-opened and petrol supplied.
Mr. King's device is already known to our readers from a deScriptio.n of his paraki attachment as applied to a Zenith carburetter. We venture to assert the fact that he is now associated with such a wellknown company as Snaitbt and Sons (M.A.), Ltd., 179-185, Great Portland St., London, W., will tend further to re-assure users generally concerning this latest paraffin.'carburetter.