A Cheap Form of Friction Drive.
Page 15
If you've noticed an error in this article please click here to report it so we can fix it.
By Henry Sturmey.
Motorcars are usually expensive productions. They are, also, not entirely simple. The combination of these factors results in a serious restriction to their use, especially in country areas, in the Colonies, and in places where the roads are rough. Practically speaking, the average motorcar of to-day is a "good road" machine, and is at a real disadvantage where exceptionally-bad roads predominate. Moreover, in out-of-the-way parts of the world where engineering shops are few and far between, their users, unless themselves mechanically inclined, are at a marked disadvantage. Undoubtedly, for use in such parts of the world, the utmost simplicity is to be desired, and this must be attained before such use becomes general. I have always had a feeling in favour of friction drive, not that I fail to recognize the drawbacks—theoretical, at any rate—to the system ; but I cannot fail to recognize its extreme simplicity. Everything in this world is more or less of a compromise, and, when all is mid and done, the question as to whether a friction, or any other form of transmission, be, or be not worth adopting, is one of striking a balance between the pros and the cons. There is no doubt that the making of an efficient friction gear, which shall not be an absorber of undue power, or unduly prone to wear, is not an easy task. The triumph of mind over matter, must, I feel sure, eventually result in placing the balance of advantages on the right side. That striking departures are possible, I had brought home to me a few days since, by a drive I was able to enjoy upon an extremely-novel machine of extraordinary simplicity. It is true it was not a commercial vehicle, but I do not see at all any reason why the principle should not be adopted for commercial purposes. especially where light loads are under consideration. The vehicle was one of a type which has made much headway recently in America, where simple design and low prices are points of value in the "back blocks," or country districts, far removed from towns. This little car was, to all intents and purposes. nothing more or less than a light buggy, fitted with a steering gear and provided with an engine. Without going very deeply into details, I may explain that the transmission of the power from the engine to the wheels was effected by the simple expedient of prolonging the transverse crankshaft from each aide of the engine, fitting it with grooved hard-steel rollers, and then swinging the engine into such a position that these rollers were brought into contact with cast-iron grooved rings attached to the spokes of the wheels. An extremely crude idea on the face of it, but perfectly effective in operation. The little rig weighed, probably, with its load of three passengers and baggage, some 14 or 15 cwt., and it readily surmounted grades of 1 in 9 (or thereabouts) without any tendency whatever to slip on the transmission. Here, we have simplicity in the extreme. Of course, the objection which will be at once raised is that it absorbs power : but, when all is said and done. I question very much whether it absorbs more power than does the transmission through various sets of gearwheels, round the right-angled corners of a bevel gear, and through the differential: the differential was abolished in the little car I mention.
Then, as to the question of wear. Somebody will say that unprotected rollers driving in this fashion must encounter much dust and grit, and that the wear will be excessive. I do not think they will. The inventor says that the grit only increases the grip, and, even if there be wear, what we have to consider is, firstly, how long the simple arrangement of rollers which I have described will wear, and, secondly, how much it will cost to renew the worn parts. In the first place, I gather that a good many thousand miles are required to wear out a pair of rollers, and the replacing of these is but a matter of a few shillings in purchase cost, whilst the fitting of them into place can be done with a spanner, as there are no intricate gear parts to be removed from the chassis, or to be reached with difficulty. Replacements could, in-. deed, be made upon the road. Hence, it seems to me, that under such a system we are getting very near to a practical solution of the friction-drive problem ; it must not be forgotten that our railway engines haul their loads by frictional contact with the rails, and that 99 per cent. of the machinery in our mills and factories is driven by friction, i.e., belt transmission. We therefore have very good engineering precedents before us. When we come to consider the general design of ears for Colonial and rough-country use, I think we must admit that, constructed as the conventional motorcar of to-day is, it must be exceptionally strong to stand up against the shocks it encounters. When I was in Warsaw recently I was extremely struck by the simple, cheap and elastic construction of the horsed vehicles used there to convey heavy loads. They resemble our timber wagons more nearly than anything else, are made up of rough logs or poles, and are so strung together that both frame and wheels yield in all directions to the inequalities of the road. There is no attempt whatever in the design to secure a resistance to road shocks, but rather a yielding to them, and the thought occurred to me that, as it would, of course, be utterly impossible in such a design to embody the motorcar features of an engine in front with transmitted power to the back wheels, some very simple form of friction transmission might easily be applied to the front wheels, and the whole of the back or carrying part of the vehicle he constructed in the simplest and most elastic manner, after the fashion of these Russian wagons. This idea is admittedly crude, and, before such a vehicle could be put into practical shape as a commercial article, much money, time. inventive ingenuity and skin would have to be devoted to its development. The idea is there none the less, and it is one which takes its direction in diametrical antagonism to the lines of thought which are to-day being pursued by our designers and engineers. It is possible, in the future, we may see an advance therealong. and, if we do and success be attained, there will he about as complete a revolution of our ideas of design as it is possible to imagine. It is worth thinking about.