SWEEPING CHANGES IN DESIGN.
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Are They Probable for the Purchasing Period Inaugurated by the Forti;coming Show ?
MOST OF US, if we had been told, at the time of the commercial vehicle exhibition in 1913, that there would not be another such show fpr upwards of seven years, would have jumped to the conclusion that in the interval there would be very big changes, not only in the extended use of motor transport, but in the design and construction of commercial vehicles. One might certainly have reasonably estimated that, if the interval were to include, as it, in fact, has done, a tremendous practical test of motor transport under the most exacting and variable conditions, extensive changes would be forced upon us • by reason of the troubles experienced and the knowledge gained thereby.
In 1913, many people were inclined to accept.as a ,fact the contention that most vehicles built primarily for use on British roads would not stand up under the inferior conditions found in many other countries, or, at any rate, would be at a disadvantage in competition with machines built specifically to work under those conditions. It is, in fact, extraordinarily .satiat,aotory to find that the biggest reliability test of ;the proctuots of a young industry ever organized, or likely to be organized, has left the commercial vehicle in general very much what it wa.s six or seven years ago. In details, improvements have, of course, been ea eoted, but, at nrst sight, there is not much to differentiate the 1920 chassis from• its predecessor of 1918. It seems, then, that the lines on which the industry worked in its early days were very sound ones, and that, if any big alteration in current products is to take place, it must be as the result either of some external circumstance, or to some highly .revolutionary invention.
: Of external circumstances, the most likely to bring .about any considerable change is the problem of fuel :supply. If it could be finally demonstrated that some :fuel alternative to petrol could be made available at a notably lower price and in thoroughly .adequate quantities, and if that fuel demanded the complete re-designing of engines, then we should, undoubtedly, see revolutionary changes. At present, however, we have not reached this point. The price of petrol continues to soar, and it becomes more and more obvious that demand is growing more rapidly than supply.
Meanwhile, we have not, since the beginning of the war, learnt a great. deal about the efficient use of heavier petroleum fuels. Investigation in that direction is discouraged by the fact that the supplies of these petroleums of various grades are all in the same hands. Were we to change from one to another, we should not dispose of the fact that we are, in the main, dependent for our fuel on the importers who control and distribute it. What we want, of course, is a home-produced fuel, but this we have not got, and, unless we use the word "home ". in itswidest Imperial sense, we are not likely to get in adequate quantities.
Even if theclaims of alcohol as a fuel are definitely proved, we shall see, in all probability, only a gradual change in engine design and not a complete or sudden departure from current practice. We shall make the fuel fit the engine, rather than the engine fit the fael. We shall work with = mixtures, gradually increasing the .percentage of alcohol and gradually modifying engine design accordingly.
Going back •aa far as the gearbox, there would seem to be, at any rate, stronger possibilities of a radical change. Though the established type of gears has done well enough, we all recognize that it is really unmechanical. In such matters, the war tended towards stability of design and the discouragement of change, because the easy maintenance of large fleets was greatly dependent on their standardization and the proper understanding of their components by the men responsible for their maintenance. Thus less attention has been devoted to the evolution of electrical transmission than would, in all probability, have otherwise been the ease. What we recognize as the normal type of petrol-electric vehicle seems to have found its level and taken its place among vehicles with so-called mechanical transmission.
esblishing itself firmly, particularly in the sphere of passenger transport, but not sweeping away all competition.
There are, at least, possibilities about electromagnetic transmission. This again, is no novelty, having been used on a foreign car for several years past. It has, however, not yet been thoroughly tried out as a system for commercial and public service vehicles. It would not be surprising to see it, or some other variant of electric transmission, growing immensely in popularity, and assisted in so doing by the fairly common use of some variety of road train.
Hitherto, the development of the road train has been held, back largely by another external circumstance; that is to say, by legal considerations, and it is now far more likely than it ever was before that changes in the law may be effected, enabling changes in design to be developed. It is the business of the law to ensure the reasonable safety of the public and the reasonable protection of the roads, remembering always that the latter are built to be used by traffic and not to be exhibited in glass cases. The roads may be injured by excessive weights, by indulgence in excessive speeds, or by a combination of the two.
Injury due to weight depends mainly on the area over which the weight is well distributed. If we double the area, we can double the weight without doing any more harm. Owing to camber and other inequalities and variations in the road surface we cannot, with good results, increase the width of tyre beyond a certain limit. We can, however, increase the number of tyres in contact with the road. For many years past we have used what is, in fact, a simple form of road train, viz., a tract e and trailer, but, from the point of view of road' damage, this combination has one weak point. The weight upon the driving axle ,must be adequate to secure adhesion sufficient to drag the whole of the loaded train. Lack of adhesion is likely to lead to road damage even more considerable than that due to excessive weight.
Thus, if we drive only one axle, it does not take long to roach the limit of weight desirable in respect of the engine which draws the train or in respect of the useful load carried. Both must be strictly limited. If, on the other hand, we drive two or more axles, the conditions are immediately changed. They are changed also 'if our train is so designed that the adhesion of -the driving axle or axles varies automatically with the useful load carried. The six' wheeled vehicle of the Scarnmell type khows how this can he done to a certain extent, and probably represents the most significant thing that can make any claim to novelty, likely to figure in any exhibition this year. The six-wheeler does not, however, represent the beginning and. end of possibilities in !the way of the haulage of heavier loads at a reasonable speed. The Renard train was a very ingenious attempt to proceed further in the same direction with mechanical transmission. The complexity of its mechanism was the
cause of its failfire. It is evident, however, that, given sufficient incentive,'there would be far greater possibilities about a roa train with electrical transmission to, at least, one axle of every vehicle in the train, and. possibly to both. Such trains have been evolved, but, probably, they could, for the present, be used to greater advantage in this country than in any other, and in thin country they have been restricted to the same_ low speed limit as is permitted to a heavier road locomotive drawing a string of trailers. If once the law were altered, 80 as to encourage the motor road train, we should have a new and strong reason for going further into the problems of electric transmission, and we might, within a. short time, see something nearly,approaching a. revolutionary change, so far as our methods of dealing with really heavy loads are concerned.
As regards vehicles for quite light loads, mechanical transmission does not present serious disadvaaitages in practice and, perhaps, the most likely possibility of a big Change in the introduction of air-cooled engines, about which aero-engine experience has provided much new information, while the availability of improved materials has in part at least overcome the difficulties hitherto resulting from working at exceptionally high temperatures. -Probably, however, the natural caution of -the trading community . will make the air-cooled engine, if it comes at all, a gradual rather than a sudden development. For the rest, while admitting that anything is possible it is difficult to see a reasonable likelihood, of a wholesale change, unless it may be due to the intreduction of pneumatic tyres on heavy vehicles. This would, of course, mean the redesigning of the chassis, without which the advantages of the pneumatic could never be fully realized. The pneumatic-tyred: heavy vehicle may come in rapidly for motor coach work, but, until it has definitely proved itself in that enhere, its employment for the carriage of goods will', pro-. bably, be no more than a very gradual development. But, with the expected rapid growth of road transport, it seems essential that greater efforts must be made in the three cognate matters of load distribution, springing, and shock absorption in order to reduce the wear and tear of the mad surfaces and in the direction of improved springs, or air tyres, and of multi-axles we can confidently look for material advances in the not far-distant future.