Motor Road Transport For Commercial Purposes
(Liquid Fuel, Steam, Electricity)

RAPID LOADING AND UNLOADING DEVICES 181 movement is obtained, and stops are provided for controlling the motion. The most interesting point is that, o wing to inclines fitted on the top of the chassis at a certain part, the body is practically in equilibrium just before the end of its horizontal travel is finished. Any further revolutions of the screw, therefore, tend to tip it, and thus to discharge the load. To revert to tlie running position it is only necessary to reverse the engine. Hydraulic Tipping. The hydraulic is perhaps the most used of any automatic system—because it is the most suitable for petrol-driven lorries which form a majority of the commercial motor vehicles in this country—and one or two illustrations of this are given below. In one make of tipping mechanism, a body with about 4 tons load can be raised into position in 20 seconds. Two cylinders are employed, and are fitted to the body about midway, and just in front of the rear axle. The duplicate cylinder method lacks simplicity, but provides a very steady lift. One cylinder types are, of course, somewhat slower in operation, the time taken being, as a rule, about 1^ mins. to tip completely a load of 3| tons, and about % mins. for return to the horizontal position. A good design will possess a very simple control, and afford a nicety of adjustment in such a way that the motion can be arrested, or altered, with rapid response to the handling of the controlling lever. A case of the hydraulic system being applied to a steam driven vehicle is that in which the tipping-gear is operated by a telescopic hydraulic ram—worked from the boiler pump—and by this means an efficient tipping angle is obtained.