A New Smith Carburetter.
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This Well-known Maker of Motor Specialities Introduces a New Four-jet :Type.
The house of Smith, we imagine, first became known to the majority of pleasure and commercial-car users by reason of its speedometers. So successful have these appliances proved in praetice, that the announcement of a new Smith carburetter must be received with a great amount of interest throughout the motor-manufacturing trade, and the vast body of users generally. It has been the intention of the directors of this company not to market the carburetter until they were fully confident that the claims made on its behalf could be carried out, not as an exception, but in all cases and under all conditions.
Ten years of close experimental work have gone to the perfecting of the appliance. Our readers will note with interest that, during the first few days of the carburetter being announced as a corrunercial proposition, in which the maker is in a position to deliver in quantities, many of the leading manufacturers at once placed orders for the appliance. Amongst these we may mention .Humbers, Ltd., Crossley Motors, Ltd., and the Daimler Co., Ltd.
The sectional drawing reproduced herewith gives a good idea of the working and the construction of this device. There are four jets and four separate choke tubes. The first is of larger bore than the others. The details are very accessible ; they can be dismantled in a few seconds, while a complete new set of jets can be fitted in about two minutes. The first jet is used for starting purposes, and it is also useful for slow running, the second, third and fourth jets being consecutively brought into operation automatically. This construction renders it possible to obtain complete control of the mixture throughout the whole range of action. Further regulation may be effected by varying the sizes of the jets, then accessibility makes tuning up a simple matter.
Centrally situated in the main body of the device is the automatic controlling valve. This slides up and down, and as the surface is being constantly washed by the moving mixture, it is kept free from dust and grit under all conditions. The float chamber can be fitted in eight different positions in relation to the throttle valve.
The operation of the appliance is in the following manner : before starting up the engine, the control ling valve is set at its lowest position, and the square ports shown in the illustration are shut, with the exception of the first, which remains half open. The starting of the engine concentrates the suction upon the first jet only, and, consequently, the air drawn in has sufficient velocity only to atomize the fuel sufficiently to obtain an easy start. As the throttle is opened, the suction increases, the sliding controlling valve automatically rises and opens the remaining ports. When the engine is giving its maximum power, therefore, the whole of the four ports are fully open, while the jets are in operation. There are no springs used on the controlling valve, and the maker claims, therefore, that the degree of suction required to raise the valve is always constant, and the velocity of the air in each choke tube when in operation is uniform. The maker further advises users to fit a comparatively large jet for the first tube. The most suitably-sized jets for the remaining choke tubes can then quickly be found by experiment.
A very useful provision made for buyers by 8. Smith and Son, Ltd., is the supply a jets which are calibrated and stamped with the number of cubic centimetres of petrol passed per minute With a suction of 6 in. head of petrol. This is the actual degree of suction automatically maintained on each jet when in operation, at all engine speeds. It will be seen, therefore, that the strength of the mixture can readily be adjusted by changing the jets. This is easily done by the removal of the nut seen at the lower end of the central chamber, which, when removed, enables the whole of the float chamber and the jets to be taken away for examination or alteration. A rotary sleeve valve is operated by a lever, located in any conv.enient position, either on the dash or the steering column. By means of this, the driver can alter the mixture whilst the engine is running in order to suit varying atmospheric conditions. The throttle valve generally used in this appliance has eight ports diametrically opposite to each other. By the use of this construction, eight streams of petrol and air may, enter the centre valve. The force of the impact does a great deal towards ensuring perfect atomization. The float chamber used with this carburetter is of the pattern which is now practically adopted as standard by many leading makers.
There have been many attempts to supply a, carburetter suitable to a big range of engine sizes. Few of these, we imagine, can claim to have so nearly accomplished the object of their existence as the newest Smith appliance. We are informed that the carburetter can be adapted to the induction pipes of every make of motor engine, and where it is found desirable, the outer casting is modified to suit the design of the engine which is to be fitted. This does not imply that the principle of the carburetter is changed in any way. The only alteration made being the changing of the jets according to the sizes required.
Mr. Chas. G. Knight, the inven• tor of the well-known silent Knight engine, has written asglowing account of the excellent results he has obtained from the Smith carburetter on a 25 h.p. Daimler. Many other well-known men have also praised the appliance. Smith and Son, Ltd., tells us that a special effort will be made to cater for the demands for these devices from users of commercial motors.
Results of a Test.
The machines tested were all 3-4 ton chassis by the Daimler Co, Ltd. They each started the trial with 2. gallons of petrol in the tank. The distance covered over a hilly road was 18 miles, and the route lay between the Daimler factory at Radford, to Stonebridge and back. The consumption in m.p.g. on an average for six trips with different vehicles, ranged from 8.5 to 9.6. The heaviest machine, including both chassis and load, weighed 6 tons 7 cwt.., the lightest turned the scale at 5 tons 11 cwt. Smithfield Market is to have a smart addition to its daily motor visitants—Messrs. Harris and Sons, the sausage manufacturers, have purchased Ft Hurtu van.
The implement shedding at the forthcoming Bristol Show is greater in extent than that of any preceding Show of the Society for many years. Doncaster is beaten by 700 sq. ft.
Considerable astonishment will be caused, we feel sure, in manufacturing circles, by our announcement that the War Office has approved the Dennis worm gear under its 1912 subsidy scheme. Ready for ilte Royal.
This issue sufficiently reflects the advanced state of our preparation to deal fully with the Royal Show in our next two issues. This journal enjoys an enviable reputetion and record in regard to " Royal Show " issues, dating back to the year 1905.
A New Registration.
Merchants' Motor Transport Syndicate, Ltd., with an authorized capital of £25,000 in £1 shares, and with its offices at 154-6, Finsbury Pavement House, E.C., to carry on the business of motorbus proprietors, etc. Directors: R. Mortimer and W. Hammond. Battery Vass.
To-day (Thursday) the Incor porated Municipal Electrical Association, in the course of its 18th annual convention, which is now in progress, will hear the case stated for the accumulator-driven van. Messrs. W. H. L. Watson and Raymond J. Mitchell are to present a paper, and to follow this with a demonstration on the road.
As we have been dealing pretty fully with the claims of battery propulsion in recent issues, we may not have occasion to do more than to publish an illustration in our next issue, hereanent. The high price of petrol now gives electricity its chance in towns.