American Commercial Vehicle Design.
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By Henry Sturmey.
The points raised by a correspondent in "Tiis CON111ERCIAL MOTOR " of January 28th are interesting, and his explanation of the reason for the difTerenc4.! between commercial vehicle design in the States and in this country is equally interesting, but, at the same time, I think, largely erroneous. When I say erroneous, I refer to his conclusion, that the absence of competition in the home market, .has, in America, produced " some of the most uncanny commercial-vehicle freaks imaginable." It is true that, protected from the competition of European manufacturers, the American builder has been freer to follow the bent of his own inclination, but the fact that he has, in his designs, eschewed the pleasure-car models of Europe, does not netesarily imply that his design is incorrect. Some people are so imbued with the idea that the now almost universal design of the touring car is the only thing possible—bocause they see very little else, that every departure from it, is, without further consideration, dubbed " a -freak." In the States, however, the designers have struck out lines for themsches, with due consideration for the requirements of their own country, and although they were much late:in the field of the commercial vehicle than we—the commercial problem, except so far as the use of electric trucks are coneerned, having only been seriously tackled within the last two years—they are, in some respects, superior to imything we have on this side. In the majority of cases, however, it must be admitted that the commereial vehicles oI America fall behind our own. That situation is due more largely to lack of experience than to faults in design, for, when we come to examine the design, we shall find a practical reason for every departure which has been made from European pleasure-car practice. These departures are not quite so far removed from our -own as anyone reading the letter in question might at first sight suppose.
Simplicity the Keynota.
In considering this question broadly, it must be remembered that American engineers—indeed, the American people—have great dislike of complication. They aim at simplicity of design in all things, with the object of reducing cost and simplifying manufacture. At times, they may carry this principle too far, and may lose something in efficiency. Successful design, in anything, after all, is very largely a compromise. Your typical American argues, broadly : " Why should I pay a dollar for anything, when I can get something like it, for 50 cents, which will do my work? " And your American engineer, following the same principle, argues : " Why should I use two parts when one can be made to do? " If we will only recognise this, we can readily see the trend of thought which has led to American departures in design. In the end, I have no doubt, they will succeed in working out a series of very practical vehicles : they may, quite possibly, develop some features, which are, because of imperfections, at present ignored on this side, to a point which will make them practical and preferable to our own. This point, I admit, has not been reached now, but • it is admitted, by all having knowledge of American motor matters, that, in the matter of quietude. American cars, both for commercial and pleasure purposes, have for many years contrasted most favourably with European designs. This is due to the fart that, from the first, America objected to noise. At a time when Europe was experimenting with the early Benz and Daimler cars, and was quite content to accept them as they were, America would have none of the " noisy, jumpy things." Electricity was the power of the future, and she adopted it—only to find the vehicles too expensive to run. Steam followed, because of its quietude and simplicity, but in this the American designers o f that period over-did the matter of simplicity,
and the cars were made too light and flimsy, with the result that, before they had had time to perfect their models, the European petrol car had asserted itself. When, therefore, the American designers, in their earlier petrol days, had to compete against the steam and electric vehicles, a not unnatural result was that the noise of the petrol cars of the period made sales impossible, and they simply had to quieten their constructions.
Engine Under Driver's Seat.
Let us look, now, at the special mechanical features which characterise American commercial vehicles to-day. We find that they are not so far removed from common sense as might be imagined. In the first place, we have the engine " anywhere but under the bonnet "—as " E.A.M.T." puts it. ln this respect, however, the American designer is not by any means alone. With the exception of those pleasure-car firms who are endeavouring to cater for the commercial-vehicle market in the lighter forms of car with adapted pleasure-car chassis, the principle of putting the engine under the driver's seat, or under the foot boards, is quite as common on this side of the Atlantic, both in this country and on the Continent, as is the more conventional pleasure-car design in which it is placed under a bonnet. The American manufacturer has more universally adopted this system than we have, it is true, but it is rapidly being recognised over here as correct, and nioet new firms entering the business are falling into, line. It is a design which saves space on the road and in the garage, which avoids over-hang of load, and which devotes the major portion of the chassis length within the wheel hase to the conveyance of the load, instead of merely to the accommodation of driver and engine.
Air Cooling.
Next, as regards air cooling. Here, we have an attempt to meet American conditions—conditions which do not obtain on our side. This may be considered as a point in design dictated by local circumstances, for the American manufacturer of to-day is, of course, catering mainly for his home market. In the States, and the Northern States in particular, the winters are very much more severe than they are with us, and for several months together the country is almost continuously under heavy frost. Hence, the water-cooling problem presents a difficulty, which is entirely met by air cooling, and, further than this, ton, air cooling appeals to the American designer by reason of its greater simplicity and cheapness of manufacture : he has recognised, from the first, that, if not now, at any rate ultimately, price must be a ruling factor in commercial success, and, by the adoption of air cooling, he saves both the cost and complication of radiators and pump.
Epicyclic and Friction Gears.
The two-speed epicyclic gear is " not to be sneezed at." It is unconventional, it is true, so far as Europe is concerned, because epicyclic gear is but imperfectly understood with us. I have no hesitation, however, in saving that ii is, in its two-speed form at any rate, absolutely the most satisfactory form of gear extant, considered as a gearing, from the points of view of efficiency, simplicity, and durability. A third speed, on a touring car, might possibly be desirable; but, if a car is constructed with its power and gearing in relation to load, considered and proportioned with a view to its use as a two-speeded vehicle, it will do its work satisfactorily, and we must not forget that, in the commercial vehicle, we are not con sidering whether the driver would " " to have a izoh.p. engine, 14 speeds, and a ion-mile-an-hour road speed, because the driver is only a part of our machinery of business. If the vehicle will do the work of our business satisfactorily, it is the driver's business to drive it.
The double-opposed horizontal engine is, it is true, more popular than it is here, but it must he admitted that it lends itself extremely well to commercial design, because it can be so conveniently stowed away under the platform without intruding with the effective load-space of the vehicle. Friction drive is another point which is being experimented with seriously in the States. There can be no doubt about its simplicity, nor about its flexibility, provided it can be made to work satisfactorily without absorbing too much power in the drive. The arrangement of two simple discs running against each other, varying their position of contact from centre to periphery of the circle, gives a gradual gear variation which is decidedly attractive. Hitherto, but little experiment has been made in Europe with this form of drive, but engineers in America have devoted considerable attention to it, and by suitable choice of materials have succeeded in getting results which are unknown here; it is now largely used in factory equipment there. Rapid wear of the friction plates and a heavy absorption of power have been the causes which have largely prevented this principle from corning into favour with us, but the use of ball-thrust bearings has greatly minimised the power absorption, and the selection of more suitable materials has reduced the wear. There are, I think, no two opinions but that, if it be proved that such a system of transmission can be made in such a way that it will not unduly absorb power, and that it will have a reasonable life, it possesses many and important advantages, especially to the commercial-vehicle user, with whom both first cost and maintenance charges are important. It is, without a doubt, the cheapest form of transmission.
Two-stroke Motors.
The marvellous simplicity of the two-stroke three-port motor appeals to your American engineer : he is "out " to construct the simplest vehicle which will do the work, and he chooses the simplest form of engine available to his uses. It is true that we have largely " turned it down '' on this side, at least for car work, though this is mainly due to its want of flexibility as generally constructed here. With a combination of a two-stroke motor and a friction drive, the American designer gets in the drive what he lacks in the motor, and gets, at the same time, the saving of quite a large number of parts. The two-stroke motor is quite successful with us as a boat motor, where wide ranges of engine speed are not required, and, although in touring cars it is not used by many makers in America, one firm at any rate—the Elmore—has made a success of it, and I ant given to understand, although I have never seen one, that this firm has a car which will compare favourably with any four-stroke motor vehicle on the road, except the Knight, in this matter of.engine flexibility. So far as I can see, this is the only point against it, if we overlook a slight falling off in fuel efficiency. We must not, therefore, judge the two-stroke motor, as used in America, by the two-stroke motor as we know it here, and we can only admit that, all other things being equal, the two-stroke motor, for commercial use, would have no rival. The future of this construction depends on how nearly equal nil thase " other things " can be brought.
British Independence Desirable.
I am not one of those who consider the conventional Continental touring-car design of to-day perfection. It is not. It falls short of perfection, mechanically considered, in many important particulars. In the pleasurecar side of the business, British manufacturers have had their hands forced by their being late in the field, and by the free competition of foreign firms. But for this, I believe, we should have evolved a distinctly British type of car, which would have had superior mechanical features over the Continental models, and which would have very materially assisted us in securing the Colonial markets. In so far as the commercial vehicle is concerned, however, the British manufacturer is easily first. While Continental makers were giving their entire attention to the touring car, many in this country were seriously attacking the commercial-vehicle problem, so that we are not as likely to be influenced by foreign designs so much, and we already have a more practical vehicle, which we have got largely by following the bent of our own inclinations, as American designers are doing to-day.