REVOLUTIONARY DEVIC]
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r CROSS-COUNTRY WORK ONLY one axle and no external anchorage of the track are necessary in a new self-laying track mechanism for use with tractors having two or more wheels and all types of wheeled commercial vehicle,
self-propelled or otherwise. It is named the Lagos Rotaped and will shortly be produced and marketed by Geo. Monro, Ltd., Ingos Works, . Waltham Cross, Herts, well-known maker 'of small-powered tractors.
Existing tracklaying machines a r e equipped with tracks, which run around a wheel at each end and, in the . majority of cases, have a series of in termediate rollers to transmit the weight of the machine to the track. For use with one wheel, the nearest approach, to the track-laying principle that has been achieved in the °past is the socalled non skid chain.
The Rotaped . .
device, as built for four-wheeled tractors or lorries, is applisd to the single driving wheel on each side,' having no other point of . attachment, and is a selflaying track in the fullest sense. There is, however, an extremely important difference between the wellknown types of track and the Rotaped. Whilst the formeris subjected to tension for a part of its length through driving forces, and for the whole of its length through weight-supposting forces, the latter has to withstand loads only in the section, or sections, that are in contact with the ground, and the link joints are not subjected to such stresses as result from tension.
These, incidentally, may be of considerable magnitude in the case of the ordinary track-laying tractor, notably, %then the machine is passing over a small bump, which concentrates the pressure at a point between two rollers. As a result, the life of all parts of the Rotaped, which, for resistance to wear, are deeply case-hardened, is claimed to be exceptionally long.
The apparatus is not confined to use on a single wheel; it can also be made in a form suitable for running on two wheels, in which case there are eight instead of six links, Chief interest, however, attaches to the single-wheel type, which has been developed in several forms. Some of these are experimental, and we understand that only a small number will be standardized. There will be tractor models, designed to replace pneumatictyred or steel wheels, lorry models, built to be fitted on pneumatic-tyred wheels, and models for farm carts, to fit on or fully to replaceany commonly used type of wheel.
To give an idea of the saving the device represents, as compared with the outlay involved' in the purchase of a complete track-laying tractor, we can state that the price of a pair of track assemblies, including the two sprocket wheels, for a standard Fordson tractor, is 2150, whilst a set for a horsed cart is 225.
Some of the different mechanisms to which we referred are seen in our .pictures. They all function as means for controlling the movement of the six links, of which the tracks of all single-wheel types are composed. In the case of the Fordson tractors depicted with the device on only one of the driving wheels, there is a system of chains and pulleys. The lorry track and that on the other two tractors, illustrated have mechanisms incorporating link assemblies operating on the lazy-tongs principlt.
The cart has an arrangement of links and levers, functioning in a different manner, but achieving, virtually, the same end. In this case, of course, there is no propulsive effort, otherwise -the action is similar in all.
Let us trace the movement of one section of track as it completes its orbit and performs its cycle of operations. We will take the section that is seen in the drawing nearly vertical in front of the wheel. This section, as the tractor advances, is lowered to the ground. When it is horizontal, the wheel passes over it and on to the next. The section is then lifted at its rear end to 'a vertical position. Next, is raised bodily and, at the same time, is svnirig "around to the upper horizontal position on top of the wheel. Thence it advances farther forwards, tips downwards and re-assumes a vertical position, ready to swing down again on to the ground in front of the -.wheel.
It is of note that this last-named movement is controlled in such a manner that the angular velocity of the link about the joint pin at its leading end diminishes during the operation from a maximum to zero, with the result that, wflen it makes contact with the ground surface, there is no irop'act, but it conies down gently and noiseleisly.
Another outstaiding point is that, while two sections are horizontally on the ground, they are held up at their common joint as the wheel passes over, so that a bridge is formed. This effect can be discerned in the reproduction of. one of the photographs of the Fordson with chain-type Rotaped, which we took during an actual demonstration of the apparatus.
It will be observed that two chains co-operate with the links, each forming a triangle, which changes in shape as the figure described by the track -sections varies. These chains are secured at opposite corners and run over pulleys at the others. In each is incorporated a right and left-handed length adjuster. One or other of the chains takes the weight when the bridge effect referred to is operating
The teeth of the sprooket engage with pins in the narrower channel on the inside of the link :plates, but they do not bottom on these pins, the rim shoulders on each side of the teeth riding on the channel edges. These parts of the mechanism, in nature and in function, are just like those of a mountain rack railway.
Mr.r0. Singer, the inventor of the Ingos Rotaped, told us that he had worked out the action of the mechanism mathematically, but, to the ordinary mind, its geometry is definitely baffling. That it function A satisfactorily, however, is not in the least doubt. There is plenty of evidence to prove the efficacy of the apparatus, and we have ourselves seen it perform under fairly exacting conditions.
We are informed that, in January of this year, when the weather was Most unpropitious for ploughing, a certain Fordson tractor, by the addition of this apparatus was rendered capable of ploughing 7 ins. deep with an International three-furrow implement, in second gear, Up a I-in-5 slope on heavy soil. Mr. Singer also
A26 told us of tests on clay land conducted last May with
Ransomes four-furrow plough, when a good performance was obtained under conditions which prevented a wheeled tractor from moving the plough at all with either steel or pneumatic equipment.
That part of the track in the standard model for agrimotors which makes contact with the ground is Virtually smoofh;. only slightly raised faces, of which there are three on each link, serve to •break the surface and assist traction. Accordingly, practically no damage is done to roads—even less, the inventor claims, than by the pneumatic tyre, the large, clean-cut tread ribs of which certainly do mark soft tarmacadam.
In cases where the smooth track fails to grip, spuds can be fitted, but there is only one pet link. Each is secured to the inside of the track , by a single screw (with-a same sized head as the.hub ,screws) and can be fixed in its guide in a variety of positions, dowels registering with corresponding holes, as• shown in the adjacent drawing. In one position, it is out of action, whilst in the others it protrudes different distances.
Substituting t he Rotaped assembly for a steel or ?nenraatic wheel is a Short and simple process, involving only jacking up the tractor, removing the hub screws and the wheel, and replacing the last-named by the sprocket on which is the track and gear.
To apply the apparatus to a lorry, one joint is undone and the vehicle driven on to the track, as with "a snow chain. So easy is the operation that in circumstances where lorries, for example, are collecting produce from a field Ara which they have to travel a pair of tracks may be kept at the field, fitted to the ,lorry on its arrival, removed when the lorry has been laden and is about to set off again by road to its destination, and then fitted to the next lorry that arrives.
A comparable method which could be adopted with an articulated vehicle incorporating a quickly detachable semi-trailer would 'be to station a tractive unit equipped with tracks at the field site, using it with a number of semi-trailers, whilst other tractive units were running on the road.
It is of interest that, at the time of writing, we learn that such a scheme has just been proposed, the specific operator—a big user of mechanical-home outfits—being 'concerned with transport in connection with work involving travelling over a large area of soft land.
Besides agriculture, the apparatus has obviously numerous other. applications. Amongst these may be named work, under snowy conditions, in districts, notably abroad, which have not been opened up and • where no roads or railways run, and in connection with quarries, mines, etc. ; also, many public-works appliances could well be equipped with the Rotaped.