PRODUCER-GAS PLANTS-A CORRECTION.
Page 16
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LT.-00.L. D. J. Smith's suction-gas plant is too important, and the possibilities of its useful development are too great for us to allow to pass without comment the assertions as to its cost of operation as included in Major Tulloch's statement which was published in our issue of the 16th inst., on page 435. The calculations to whieh we refer contained, in our opinion, two mistakes : a small one, due, apparently, to some arithmetical error, and the large and important one of building up a case on facts strongly favourable, to the device under discussion. We will dispose of the small matter first. Major Tulloch's calculations have reference to a trial on a lorry the gross weight of which, with load, was 5 tons Eli cwt., or 5. 325tons. He concludes, as a, result of the coal consumption during two trials, that the cost of fuel is 0.08d. per ton-mile. He states in the body of his letter that the petrol consumption of this wagon normally averaged a gallon for five miles of running, and he draws the erroneous conclusion that the cost of fuel, using anthracite at 40s. a ton, is equivalent to petrol costing id. per gallon, on the above hypotheses. Five miles, with a gross load of 5.325 tons is 26.6 ton-miles. At 0.06d. per ton-mile, this is on an equality with petrol at 2.13d. per gallon, and not id., as was stated by Major Tulloch..
The larger error consists in drawing a comparison between, on the one hand, a commercial vehicle running on petrol and giving results considerably below the averages obtained in ordinary commercial usage, and on the other, results obtained from a vehicle run on motion gas which is produced from an apparatus which must, from the circumstances of the case, have been tuned to, the top of its form, and have been carefully nursed throughout the trial.
In estimating the comparative economies from a commercial point of view of competing systems, it is clearly unwise to draw conclusions from occasional examples. This is especially true in regard to the ease under discussion. It would surely be fairer to on compare he exceptionally good ton-mileage performance on a commercial vehicle using petrol, with that obtained with suction gas and set forth in the statement to which we are referring. Such a figure is 70 ton-miles to the gallon of petrol. Calculated on Major Tulloch's basis of 0.06d. per ton-mile, this gives us a far different figure of 5.6d. as being the equivalent price per gallon for petrol to compete with suction gas. A moderate performance, using,petrol, and one generally attained and frequently exceeded in commercial practice is 45 ton-miles to the gallon, .and here the equivalent petrol price would be 3.6d. per gallon. •
It is fundamentally necessary, in making such comparisons as the one we are discussing that average results covering a considerable amount of use under commercial conditions, and at the hands of ordinary' users, be taken as the bases. In the case under discussion we have already ascertained the fuel consumption which can be obtained in ordinary circumstances with petrol, namely, 45 ton-miles per gallon. This 'Should rightly. be compared with results obtained from Col. Smith's device in the hands of the ordinary user running ort-coinmercial service, with supplies of coal obtained and selected without special care as will undoubtedly be the case in ordinary circumstances. Then such a comparison is made, we anticipate that the tendency will be considerably to inci ease the cost per ton-mile, using suction gas, and that a more reasonable estimate for the ,equivalent price per gallon of petrol will be about 5d., which, it will be remembered, was the figure given by Mr. Shra onellSmith at his recent lecture in Manchester. Moreover, even this figure is -sufficiently favourable, and the economy shown is ample enough to .cause the user seriously to consider this alternative fuel for his motor vehicles. There is certainly no need for its promotors to endeavour toexaggerate their achievements. It is very much better slightly to exceed promises of imProvement than to fall short of them.