The Mechanical Handling and Storing of Material

284 THE MECHANICAL HANDLING OF MATERIAL Fig. 414. Men Returning from Work. # These ropes terminate at the upper end at a massive wooden trestle carrying tension bars fitted with thimbles suitably supported in brackets on its summit, to the outer thimbles of which the above-named fixed ropes are attached, the strain being transmitted through the tension bars to tie-backs which are attached in the rear, transmitting the strain to the anchorage further in the rear. Thus the fixed ropes, at the point where the strain is most severe, are not subjected to any bending action. At the lower terminal it is necessary to transmit their strain to an anchorage in the rear of the staging, since the staging itself is not constructed to safely take any side strain. The lower ends of the fixed ropes are, therefore, attached to double screw tightening gears, which in their turn form the end of the back tie-bars. These are made of steel bars connected by pins, terminating in anchor bars which are buried in the chalk at the bottom of the sea some distance in the rear of the staging, concrete being filled up round them and placed over them in such a quantity as to resist the pull. The tightening is accomplished by an arrange- ment of two screws, combined so that when the tightening is effected by one screw, the other acts as a fulcrum and reduces by one half the strain necessary to apply on the screw for tightening. This tightening gear, with a drift of about 8 ft., is carried on a strong wooden frame placed on the staging above referred to, and advantage is also taken of this frame to carry suitable lead-on pulleys and a wheel, round which the return hauling rope passes. The stones, the heaviest loads, always descend on the 6-in. rope, while on the parallel rope a balance load is run, which the stones descending draw up, thus considerably reducing the necessary brake power. This system of working is necessary only in the transport of the stones and very heavy loads. Each rope is used indiscriminately for the transport of lighter loads. It is estimated that the working strain on the 6-in. rope is about 30 to 34 tons, and that on the lighter rope 25 to 27 tons, carrier. That for carrying stone is fitted with an On each fixed rope is placed one eye, to which the Lewis bolts in the stone are shackled; that for the balance load is fitted with a receptacle capable of containing 2 tons of ballast or chalk, and, in addition, is fitted with a wooden shield with doors. The lower portion, which holds the ballast, is arranged to tip without disturbing the upper portion or shield, which, when the receptacle is empty, is employed for the carriage of about a dozen workmen. A similar receptacle and shield can be attached to the carrier provided for carrying stone on the 6-in. rope when the carriage of workmen or of ballast, cement, etc., is required. Attached to the two carriers is a running head, which has four steel wheels, which run on the fixed rope. These wheels are articulated in pairs, so that each has an equal pressure on the rope. Attached to each of these carriers is a hauling rope, which, on arriving at the upper terminal, passes over a pair of 6-ft. pulleys, and thence is led to a