A NEW AMERICAN TRACTOR NOTION.
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The Latest Improvements in the Knox Tractor Truck.
By Henry Sturmey.
Some three years ago, shortly after the outbreak of war, I described in the pages of THE COMMERCIAL Moron the _Knox tractor truck. A number of demonstrations were given in the neighbourhood of London by the agents, who were .then importing the equipment. Since thennothing has been heard of it on this side.
The Knox Motor Associates have now developed the principle in a form Which makes it more readily attainable and more generally useful where a very large amount of haulage is not required to be done. It also enables any existing car chassis .to be brought into service for the purpose of acting as the tractor unit for trailer wagons carrying either two, three, or five tons.
The same general principle of the K i
nox tractor truck s employed, the difference being that in this NOW traction unit only the rear wheels, axle and spring system are special, and these replace the existing rear axle, wheels and springing.of the car which is to be used in conjunction with them.
The oonatruction will be seen by the annexed illustrations, from which it will be seen that a regular truck axle is employed, of the,internal-gear drive type; that (is, & solid, deadweight supporting axlesis used,.-in ;:conjunction with a differential shaft parallel with it, carrying driving pinions in engagement with the internals gear rings „ attacheth to the Wheels: This supports; on stout semiellipt'cal springs, an oblong or nearly square platform turn-table, supported in such a way that the entire platform has a certain amount of longitudinal rocking movement, an arrangement which virtu
ally hinges the combined construction over what then becomes the central pair of wheels, thus allowing for variations in road contour.
The turn-table is arranged to go beneath the forward end of the trailer
wagon, which may be auy horse-drawn wagon, with the front wheels, shafts and axle removed. Thus it will be seen that the traction unit, which has become the sear wheels of the car, likewise becomes the front wheels of the trailer, .taking its share of the carried load.
The method of attachment to the car which, it will be seen, really becomes only a portable power plant, is as follows :—Rear wheels, axle, and springs of the car—which may be of any make or size, so ..long asrit is. of ...the shaft-driven type—are removed and•the..rear end of the frame is supported oil a cross-bar of channel iron, which, is carried on the top of a pair of cantilever springs mounted on the unit. These springs are independent of the weight-supporting springs of the unit, and their sole purpose is the support of the rear end of the car chassis. The channel cross member referred to unites the bases of the two cantilever springs which carry the weight of the chassis and driver. The free ends of these springs are slidably mounted in chairs, which are fastened to the solid or dead axle, and a pair of torque arms are bolted_ to the underside of the trailer platform spring seats. These serve to keep the axle parallel to the cross channel frame bar at all times, without interfering with the action of the cantilever springs. The body of the car; with the exception of the front seats is, of course, removed for this purpose, and the drilling of two holes in the cross member frames enables it to be clamped and bolted into position. 1i. little fitting will be required now to alter the location of the bolt holes in the rear universal joint flange of the drive shaft to accord with those on a special flange furnished with the traction unit. These two holes drilled, the two flanges are bolted together and the driving shaft is then in conneotion with the driving, mechanism of the traction unit. .All that is needful then is to conmet up the brake rod attachments of the car with the brake system of the unit. The tractor is then backed under the carrier, which has been jacked up to permit this operation, the load carrier is lowered on to the trailer platform, the locking bar fixed into place, and the outfit is ready for service. Adaptations of this kind are not very popular in this country, the most favoured way of adding speed to the vehicle originally constructed to be horsedrawn and to increase the load hauled by the motor being to couple a van to a motor lorry.