Type C.
Page 20
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As the two exhibits which come under this heading differ in respect of the boiler—one has a loco-type, and the other a vertical—we will deal with this essential part of each vehicle in our separate notices below.
The engine, in each case, is a horizontal compound one, and is mounted, with its cylinders parallel to, and below the level of, the main members of the frame. The transmission on this type of vehicle is by means of gearing throughout, and, in the case of the two vehicles exhibited, is completely enclosed, thus ensuring protection from dust, and more perfect lubrication. Two speeds are here provided, as in types A and B. The changes of gear ratio are easily effected by means of a single lever. Our diagram illustrating this type of steam wagon must, of course, only be taken as indicating the general principle of a gear drive, and not as the arrangement of any particular maker. The notation of parts is the same on this diagram as that followed in types A and B, with the exception that F represents a spur of double-helical gear pinion meshing with the gear-ring or wheel G, mounted on the differential-gear spider, on the back live-axle. This form of drive necessitates a special disposition of the spring mounting, in order to ensure that there shall be no sliding motion taking place between the teeth of the reducing gear, due to the distance between the centres of countershaft and back-axle varying with the changes in the spring deflection. The gear drive offers advantages which, for heavy loads, are not offered by any other form of drive. The machine-cut gearing, running in oil, is very silent, and greater strength can be secured, with less weight, than is the case with chains. The leading features of the two exhibits, which come under this head, have so few points in common, beyond the fact of their being geardriven, that we propose to deal more fully with them below. In the case of the vehicle fitted with loco-type boiler, the steering gear is of the turntable type; but, when a vertical boiler is fitted, the Akerrnann type of steering gear is employed.