The Mechanical Handling and Storing of Material

248 THE MECHANICAL HANDLING OF MATERIAL Fig. 349. Side Roller for Negotiating Curves. placed over the truck wheels to prevent and just sufficiently high to clear the top of the truck body. Fixed high up and between these runners, and at the off-going end, is a bar with a roller carrying the rope; and as the truck reaches the frame the body is slightly raised until it comes into contact with the runners, when the rope is pulled out of the “jockey” and the truck released auto- matically from the rope. Another arrangement for a disengag- ing frame consists of a double frame carrying two lengths of channel iron set parallel to the rope, and just sufficiently wide apart to allow it to pass freely be- tween them, and up over a similar roller at the off-going end. As the truck reaches the frame, the rope passes up through the slot formed by the channel irons, and as the opening is only wide enough to admit the rope, the latter is pulled out of the “jockey,” and the truck disengaged. A form of haulage very suitable for spoil heaps and tailings dumps, consists in having the “ jockey ” fitted to the side of the truck carriage, instead of on to the body, as is the usual practice. With this arrangement the truck can be tipped without being released from the rope, and conse- quently there is no time or labour lost in disengaging or rehooking. A haulage of this description is very economical, as from the time the truck is filled at the bin, and hooked to the rope, there is no need to handle it until it is returned to the filling bin again, the tipping, righting, and disengaging all being done automatically. With this arrangement trucks negotiate curves of 12 ft. radius by a series of rollers set about 2 ft. 6 in. apart, and just on a level with the “jockey ” on the truck. These curve frames (see Fig. 349) are held in position by ballast- ing them down with sand bags or stones, and can be easily shifted bodily forward as the dump extends. A serviceable truck tipper (see Figs. 350 and 351) consists of a frame carrying a length of rail or pipe set at such a height as-to just catch the top of the truck body; this tipping bar is placed diagonally across the track with the on-coming end, about 1 ft. outside the rails, and the off-going end over the centre line of the track. As the truck reaches the tipping bar, the body runs along it, and is pushed over to one side until it is over- balanced and tipped,1 a check bar being the carriage capsizing also. The same principle is applied to the “ truck lighter ”; a 1 For descriptions of other self-emptying trucks, sometimes employed on such lines, see chapter “ Unloading by means of Specially Constructed Self-emptying Hopper Wagons,” page 494.