OPINIONS FROM OTHERS.
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The Editor Invites correspondence on all subjects connected with the use of commercial motors. Letters should be on one side of the paper only and, preferably, typewritten. The right of abbreviation is reserved, and no responsibility for views expressed is accepted.
PETROL-ELECTRIC VEHICLES IN AMERICA.
The Editor, THE COMMERCIAL MOTOR.
[2678] Sir,—In the article in The Commercial Motor for April 24th on America's growing interest in the petrol-electric vehicle you quote a statement to the effect that, during tests, a petrol-electric vehicle made by the White Co. has developed from 30 to 40 per cent. more electrical energy than any type of petrolelectric equipment now in operation.
May we point out that this increased power is due mainly to the larger engines employed and has no greater significance than might be attached to a statement that such and such a company is DOW employing an engine giving 30 to 10 per cent, more brake horsepower than any other manufacturer.
It is, perhaps, unfair to comment on an abridged version of the technical paper read by Mr. Attwell, but •his claim that the loss of efficiency was never more than 50 per cent. and, under favourable conditions, was as low as 26 per cent., would indicate either that conditions in America are not so favourable as in this country or that the system has not yet reached the same state of development as on this side, as the efficiency under favourable conditions of the TillingStevens petrol-electric drive has reached 82 per cent., representing a loss of 18 per cent. against 26 per cent. Presumably the statement that the loss of efficiency Is never more than 50 per cent. was qualified, as this would depend on the road gradient, which, if too steep, would cause the vehicle to stall when the efficiency fell to zero.
The claims in respect of electric braking and its employment are also curious in view a the movement among manufacturers of gear-driven cars to introduce free-wheeling, which has been a feature of the petrolelectric system for some 20 years. The objection to the use of electric braking as an additional feature, on this side, is confined to the increased Weight and cost, as otherwise it is perfectly feasible.
It may interest your readers to know that, according to information given us by our American licensees, the adoption of full automatic control is due to their inability to obtain the same class of driver as is available on this side. We find that it is impossible to cover the whole range of conditions automatically, and a. certain amount of control is left to the driver.
It is interesting to note that the weight of the fourwheeled American vehicle deseribed in your article is greater than that of the six-wheeled vehicle of a similar overall length produced by us and would weigh with a full complement of passengers, as a double-decker. well over 1 ton more than is permitted by the Ministry of Transport's new regulations and would be well over the limit as regards width.—Yours faithfully, FOR TILLING-STEVENS MOTORS, LTD., W. R. SHEPHARD, Managing Director.
Maidstone, Kent.
[Our remark about the horse-power of the engine employed was actually a comment upon the practice of makers of petrol-electric vehicles in equipping them in the past with engines of too low a horse-power. Now that more powerful engines are being employed in this country far better results are being obtained and users, we find, are now much more inclined to -discuss and consider the petrol-electric vehicle for their work.—En. C.M.I