Where Electricity, Petrol and Oil Score
Page 55
Page 56
If you've noticed an error in this article please click here to report it so we can fix it.
PARTICULARLY interesting was the subject chosen by Capt. J. B. Walton, chief mechanical transport engineer of Unilever, Ltd., for his paper, '' The Comparative Advantages of Electric, Petrol and Diesel Oil Engine Road Vehicles."
The author points out that it is almost impossible to make adequate comparisons between these types. because they must obviously be governed by the work of the operator. It may be feasible, however, by studying the characteristics of each, to evolve some formula which may be a useful guide.
So far as the goods vehicle is concerned, no more is needed than a box or platform, although this suggestion may raise a storm of criticism. Capt. Walton believes it doubtful whether anyone could attribute increased profits to elaborate .bodywork or painting. In the case of packed goods, all the protection needed is in the pack itself. Other goods, not packed, arc self-protective and need no more than a platform. The ultimate consumer cannot be interested in the various media used to deliver, say, his bacon. The author says he might go even farther and claim that when human freight is carried, it needs no snore than a comfortable seat.
Dealing first with the electric Vehicle, he says the improvement in the actual motor ha's not been great, and the efficiency has not increased to anything like the extent obtained with other prime movers., Research has, however, resulted in an enormous increase in battery efficiency.
Profitable Spheres for the Electric.
In certain directions, the electric must have a profitable application. The simplicity of the whole mechanism has obvious attractions, and the wear factor is so slow as virtually to give an infinite life. Battery manufacture has reached such a high pitch that it is possible to put a definite term to the life, and thus give the operator some indication of What his running expenses will be.
The quantity of energy stored is limited by the powerweight ratio. The vehicle requires, however, a certain amount per gross ton-mile and, from a technical viewpoint, is in practically the same position to-day as it was SO years ago. The balance struck between battery size and weight has resulted in an economic speed of 12-18 m.p.h., and an economic limit of 40 miles per charge. With higher speed or greater range, the battery weight becomes so large as seriously to interfere with the pay-load. There does' not appear to be any prospect of a material reduction in battery u-eight.
A major adyantage is that there is no need for the owner to have his own generating plant. All that he requires is • a charging plant. On certain work, for which this type of vehicle is suitable, the " fuel " cost equals petrol at 3d. per gallon, whilst oil costs are almost eliminated. Little maintenance is required, and the author feels that the electric is not receiving from operators anything Eke the attention that its attractive features deserve.
Within certain limits, the power costs are a quarter of those of the petrol vehicle and half of those of the oiler, whilst the maintenance costs are certainly 75 per cent. lower, Turning to the petrol unit, we must bear in mind that, as a heat engine, it was, and is. an indifferent appaiatue. Thermal-efficiency figures show little improvement, and we can reasonably hope that there is an enormous amount of development work ahead of it.
Many people believe that steam has not had even a fair proportion of development work spent on it. Its possibilities—and they are easy of achievement—appear to be more attractive than those of petrol.
Versatility Explains Petrol Engine's Success.,
The petrol engine has succeeded entirely on account of its versatility. it needs merely to be fed with petrol and oil, and there is no limit to the distance it can travel, or, within reason, its speed, but it uses a fuel which is expensive and difficult to produce. The number of moving parts and its adjuncts are so numerous as to leave one surprised that they can ever continue to function harmoniously for any considerable time.
As an economic unit, it would be hard to find anything worse, and one can enumerate its disadvantages at great length. It would, therefore, be as well to see what are its advantages. • The operator is principally concerned with fuel, repairs and depreciation. The rate of wear is comparatively rapid. It is possible to compute how much wear a given vehicle will withstand and reduce this to terms of cost. Operators are faced with widely diverging problems.
The maker does his best to turn out a vehicle which is a fair compromise. It is left to the operator to use it in the most economical manner.
A careful assessment of work to be done is necessary. A maker may install a 75 b.h.p. engine, but one operator, to meet his requirements, may need not more than 60 b.h.p, at any time, whilst another may want 80 b.h.p. Fortunately, there are ready means at hand to meet these adaptations, and this constitutes one of the advantages of the petrol engine.
Maintenance is not only of major importance, but one of the major costs, and close consideration must be given to this aspect, with a view not only to reducing wear by attention to operating conditions and the careful choice of lubricants and fuels, but to forestalling wear by all available means. Little of an anticipatory nature exists on the maintenance side of a transport business, other than the fetish of an annual overhaul. Quite why time should suddenly impose itself upon miles as a criterion of wear is difficult to understand.
With a given engine, although the valves would go for long periods without attention, when serviced the cost might be out of all proportion to the work involved. Grinding-in and reseating at regular periods of 7,500 miles would stave off major replacements and the time taken would be much less than grinding-in, say, once in 15,000 miles.
A careful study in maintenance in relation to miles run enables one to anticipate wear and arrange a rational sequence of maintenance operations. In spite of increased costs, rather than pass these on to customers, it would be better, in a logical manner, to see how they can be met out of economies in operation.
Referring to the oil-engined vehicle, the author says that the remarks made on the advantages of the petrol unit apply with, if anything. greater force to the former. He does not, therefore, consider its disadvantages.
In making comparisons, however, he refers to the elimination of certain troublesome components, i.e., the whole of the ignition arrangements. There are, of course. fuel pumps, piping, injection valves, etc., but these are of much more robust construction. Operators are faced with the recovery of additional first cost in terms of years or miles, so that it can be translated into depreciation figures. The operator of an oil engine may find himself, at the end of a given period, at a great disadvantage in the matter of costs ; the petrol user, at the end of a comparatively short period, is clear of his liability. An important point in favour of the oil engine, as compared with the petrol unit, is that it is able to travel twice the distance on a given quantity of fuel. If them be a price differential in favour of oil fuel, this is a farther advantage, but a large annual mileage is ptesupposed, thus the versatility of the oil engine is reduced.