Construction and Tires.
Page 4
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By Henry Sturmey.
The letter in a recent issue of THE COMMERCIAL MOTOR (23rd ult.), signed " Wholesale Baker," and
appearing under the heading of "Bakers and Motor vans," raises a point of great importance to the motorvan user and more particularly to the user of the small-load machine, which class of user is, as a whole, new to the motor question, and is not so well acquainted with the requirements for commercial work as are the users of the heavier-class machine. "Wholesale Baker " says—as a result, be it noted, of his experience—that he finds the class of vehicle he has purchased, whilst well suited for the requirements of his business " expensive in tire upkeep, if pneumatics are used." This is an accepted fact, to-day, so far as regards the larger vehicle, but the buyer of the small van has not yet studied this
question, and he is easily persuaded by the nian who has something to sell that pneumatic tires are the right thing. He sees touring cars used universally with pneumatic tires, and there is not much difficulty in getting him to believe that they are a necessity ; indeed, in the majority of cases where these light pneumatic-tired vehicles are offered, I doubt if the question is ever raised. It is taken as a matter of course. The result is inevitable, as " Wholesale Baker " has found to his cost. His explanation, as to the reason of his acceptance of them, is further illuminative, as illustrating and proving what I have before now said in this journal on the same subject. He says " I was informed "—presumably by the agent who sold him the machine—" that the ordinary solid tire would damage the machinery of the vehicle, and therefore I decided "—presumably, by inference, after having found to his cost the pneumatics expensive in regard to upkeep—" to fit a wellknown make of resilient wheel and tire." Here we have the situation in a nutshell. The whole case is really a serious one for the trading community, and, by its reflex action, for the light commercial-van movement, as such. Numbers of firms in the pleasure-car trade, noting the rising demand for light delivery vans, are en(leavouring to enter the field with van bodies built upon cab or. touring-car chassis. If the manufacturers themselves are not doing this, there are agents all over the country who are anxious to snatch any order that is going, and to get a finger in the commercial-vehicle pie, and who will not think twice about offering one of the touring-car chassis for which they happen to be agents, or a second-hand one which they happen to have for sale, as "just the thing for light-load work." Most of them recognize the fact that these chassis will not stand up on solid tires, because, in touring-car work, the solid tire has long since disappeared -by reason of the numerous breakages which resulted from its use ; so the agent has at least sufficient " horse sense " in his composition to see that it would be disastrous to attempt to fit solids to the chassis. When a customer who, perhops, has heard some hint that solid tires are the right thing for commercial work raises the point, he is informed that solid tires would " damage the machinery of the vehicle.'
It must be remembered that the work which a touring car is called upon to do is totally different to that of a vehicle in commercial service. In the first place, the loads are lighter. Few ordinary touring cars are constructed to carry more than four passengers in addition to the driver, and a great many are not designed to carry more than three. This means that the load does not exceed about 51 cwt. at most, whilst the body, in comparison with that of a van, is of light construction. And this load is a "live "
one. The human body is, if I may so use the term, elastic. At any rate, it yields under shock, and consequently a great deal of the force of the road shocks which gets past the tires and springs is absorbed in the bodies of the passengers. With the commercial vehicle, however, the load is a "dead " one. It is solid, hard and unyielding. It does not " give " in the slightest degree to the shocks, with the result that the chassis beneath it has, in itself, to absorb them all. Hence, the class of chassis, suitable for touring-car work requires the fitment of pneumatic tires to enable it to hold together at all, but, as pneumatic tires are cheaper in first cost than solid ones, and as, moreover, these chassis, being turned out in considerable quantity and being generally of light construction, without the metal in them, are cheaper to produce, such light vans can be offered at a price which is, at first sight, attractive. As, however, as " Wholesale Baker " related, the rapid wearing out of pneumatic tires under " dead " loads brings the cost of tire upkeep to a prohibitive figure for ordinary work, it is a necessity either to employ some form of resilient wheel, as he has done, or to employ a chassis specially designed and constructed for use upon solid tires. Those few manufacturers who have for some years studied this question, and have specialized upon the construction of light-load vans designed to stand up under heavy use on solid tires, whilst unable to compete in price with the touring-car chassis, are able to provide a satisfactory vehicle, which does not require pneumatic tires to hold it together. Of course, whilst the pneumatic tire will " save the machinery" of a light van which requires it, it will also "save the machinery of a stronger construction, and I have not the slightest doubt but that, if the use of pneumatic tires for commercial work were a practical commercial proposition, the makers of commercial vehicles would universally adopt them.
Upon one point and one point only is the situation in any way altered, and that is where high speed is required. The average commercial vehicle has no need to travel beyond 15 or 20 miles an hour, and is built for such speeds. The effect of road shocks increases as at lowest the square of the speed, and, when speed rates beyond 20 miles an hour are desired, it is advisable, in the interest of the machine, that pneumatic tires or resilient wheels should be fitted— even upon specially-constructed commercial vehicles. Hence, the reason that newspaper vans are fitted with pneumatics. In this business, competition requires speed of delivery, and the cost of obtaining it is a comparatively-secondary matter. The newspaper proprietors know that pneumatics are expensive in use, but they also want the speed, and they are prepared to put up with one in order to obtain the other. Other trade users will have to do the same. Broadly speaking, however, it may be taken as an axiom that, for the general commercial work of the country, a speed of 20 miles per hour is not desired to be exceeded, and a specially-constructed vehicle for commercial work is a necessity, for the simple reason that pneumatic tires are not a commercial proposition for other than the lightest ranges of " dead " load, and the ordinary touring-car chassis will simply not stand up on anything else (unless it he on resilient wheels). I think that users, or intending users, can accept it as an axiom that, if a manufacturer or a dealer puts forward a pneumatictired machine for more than six-hundredweight loads, the fact of pneumatic tires being fitted will in itsfilf, condemn the machine as being, self-disclosed, unsuitable for commercial work.