The Mechanical Handling and Storing of Material

208 THE MECHANICAL HANDLING OF MATERIAL depressing the rope. In this case the loads on arriving at the tightening and discharging terminal are lifted by hand off the carrier; but a simple automatic arrangement can be provided, by means of which a projecting bar is allowed to strike the carriers, whereupon the bags are delivered automatically. The Double Ropeway.—In the double ropeway, which is the most generally diffused type in these days, the load is carried on a fixed rope, which serves much the same function as a railway, except, of course, that the railway rests on sleepers, while the rope is carried through the air. This rope is fixed and taut, whilst the load is drawn by the second rope, which is called the hauler. The return is similar on a parallel fixed rope. This kind of ropeway is applicable in cases where the loads to be transported exceed 400 tons per day; where individual loads exceed 6 cwt.; where the incline exceeds 1 in 3, and where long spans are necessary. The lock-coil rope which has been largely substituted for the old type of spiral rope is here illustrated (see Figs. 388, 389, and 390). It is undoubtedly possessed of great strength, and has been installed under conditions involving heavy work and great strain on the ropeway. A ropeway of this type is erected somewhat as follows :— Two fixed ropes are stretched parallel to one another, about 7 ft. apart, and supported by posts, fitted with saddles, at a distance of about 300 ft. from one another. The ropes- are anchored at one of the terminals and tightened at the other by suitable gear. The carriers run on the fixed ropes as on a rail, and are fitted with running heads carrying, steel grooved wheels. The hanger from which the load is suspended is pivoted from the carrier, and the load is conveyed at a speed of 4 to 6 miles per hour by an endless hauling rope, operated by driving gear at one end, and controlled by tightening gear at the other. The hauling rope is attached to the carrier by an automatic clip which will release itself by touching a bar on arriving at the terminal station, but will hold sufficiently tight to enable the hauling rope to drag the carrier up inclines. The grip of the hauling rope on the load may be supplemented by knots or sleeves on the former, or by means of a suitable casting inside the rope at certain points, so as to make an enlargement at the point where the clip engages. With slight inclines the pressure of two pulleys or plane surfaces on each side of the hauling rope is sufficient, but in the case of sharp inclines, where the pressure on the hauling rope is severe, the clip attached by means of wedges may be used. With lines erected on this system, shunt rails and driving and tightening gears are used, just as in the single rope lines. At each of the supports rollers- have to be provided on which the hauling rope rests when it sags between the carriers. These rollers are provided with guide bars to increase the range of support, and guide the hauling rope into the above-named pulleys, should it be deflected from the vertical.