TAR OIL AS A MOTOR FUEL.
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1TH THE GROWING demand for petrol to be devoted to air craft service and also with the development of the desire in this country,to give preference to the use of home-produced fuels for the propulsion of motor vehicles, considerable attention is being paid to tar oil as a likely fuel. We have made reference occasionally ..to the apparatus designed by Mr, F. W.
Wilkinson, M.I.E.E., of Hatfield, Herts., which is virtually an attachment that can be applied to any existing carburetter enabling the motor to which it is fitted not only to run on such heavy fuels as paraffin and tar oil, but also to start up without the need of using a light spirit for that purpose.
The apparatus consists of a pot (inclicated at A in the accompanying sketch), which is mounted alongside the carburetter, the bottom, of the pot being connected to the bottom of the float chamber by a pipe so that the fuel in the pot is at the same level as the _fuel in the float chamber. Inside the pot is a coil of electrical resistance wire which is connected up to the lighting battery 'of the car through a switch and an indicator lamp. When the current is turned on, this wire becomes practically red-hot and, in a space of about two or three mithites, the fuel in, the pot; is virtually boiling and giving off-an inflammable gas. Above the pot is a cock (G) connected byl a pipe to a T-piece (B), the Manch. of this Tpiece connecting with the induction pipe, as it rises from the carburetter. Beyond the T-piece -is another cock (D) and a small pipe communicating with the exhaust pipe. When it is desired to start the eneine the.' current is turned on, the cock (C) leading to the Tspiece is imolai and the click (D) leading from the exhaust pipe is clesed. At the end of two or three minutes (not more) the engine will start an vapourfrom the pot, and, after running for a few revolutions; the cock (D) is -opened and the cock (C)is . closed, and the fuel is now drawn through the carburetter from the float chamber. It is vaporized in the induction pipe by the hot gases which are drawn through the cock (I)) from the exhaust pine. The current, of course, is switched off aS son as the engine is running on the feel froth the carburetter. The amount of current used is..exttemely sniall: Controls are taken froth thetwo cocks (0) and (D) to buttons on the dashboard.
We. had an opportunity recently of making a test run on a 20 h.p. Overland vehicle with an eleotric self-starter which
Mr. Wilkinson has fitted up with this appliance. The oil which was being supplied to the engine was a product from the gasworks of .950 specific gravity and costing 9d. per gallon. Its calorific value would be about 9000 calories or 16,000 B.T.U.s, but Mr. Wilkinson now tells us that he is in touch with a supply of tar Oil which ranges from 1.032 to 1.080 sTiecific gravity and costing 47,d, per gallon. With a full load, the ear won/d.
normally cover about 19 miles to the gallon of petrol, and on paraffin or tar oil it covers about 17 miles to the gallon. In the course of our test, the current was switched on to the resistance coil in the pot, and within three minutes the engine was started by the electric starter at
about the first revolution. The engine was not qnite cold as, only a few minutes before, it had made a journey to the station, but Mr. 'Wilkinson's experience of this vaporizer, extending over two winters, shows that it has never yet-failed to start the engine almost immediately, even in cold weather.
The moment the engine was running, the cock from the heated pot to the induction pipe was closed, the cock leading the exhaust gases into the branch pipe was opened, and the engine continued to develop power without the slightest change being noticeable. After that, Iona mile or so, the extra air valve was gradually opened so as to give more air. The car was driven up the long climb to the top of Digswell Hill, out of Hatfield, and it made an excellent showing, as it pulled up the whole way on top gear without a trace of a knock in the engine. We had fully anticipated that the engine would knock on the steepest portion of the hill, and the absence of this noise was a pleasing feature of the test. The latter, by the way, was only of short duration, but it included a number of attempts to stall the engine in simulated traffic checks—there was too little traffio on the road for us to carry out real traffic checks ! There was no ob. jectionable smell about the exhaust, or about the vehicle, and there was 'certainly nothing beyond the wait of two minutes when starting up, to indicate that the fuel on which the vehicle was running was anything other than petrol; on the other hand, the way in which the engine pulled up the hill without showing the slightest sign of distress showed that the fuel offered certain advantages in running over petrol, quite apart from the fact that the cost was considerably lower and that the fuel is a home product; both extremely important factors in themselves.
Mr. Wilkinson is connected with certain gas ,companies, and he says that there should be ample, tar oilat a very reasonable price entirely suited for use on motor vehicles.
The cost of the apparatus, which includes the fuel heater, the switch, cable, indicated lamp and holder; the fittings to the exhaust pipe, the extra valve and controls and the two cocks on the fitting, is £6 99. 6d. Mr. Wilkinson's car is equipped to run on gas, and he has a small reservoir for gas at the rear of the vehicle which he uses as in alternative fuel.
We have only rough figures of fuel cost. Taking the weight of the vehicle at 25 cwt. (a conservative'testimatc) and the mileage obtainable per gallon of fuel at 17 we get 21.25 ton miles per gallon. The cost of the .950 specific gravity .tar oil wah 9d. per gallon bought in small quantities. This gives Ahl. per ton mile. If the heavier fuel will give equal mileage and ,the' cost is LIN. Per gallon. we shall get the figure of .22d. per ton mile, as against petrol costing from one Denny to twopence per ton mile accorde ing to load and circumstances. The excise authorities ha ve .informed Mr. Wilkinson that the oil is not dutiable when used on a meter vehicle.