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THe Marine ReEvIEw bt a ye fee FIG. 2-- DETAILS OF CONSTRUCTION OF UNLOADERS, PHOTOGRAPH TAKEN JUNE, 1907. shell and the two supporting concrete walls is. a filling -of).rock.. As com- pleted, this construction looks like a solid concrete trough, whereas it is. really made up of considerable rock filling. The track for the rear leg of the un- loaders, which is on top of the trough wall on the water side, is made up of two 85-pound rails 3 feet 6 inches centers, spiked to ties which are laid on top of the concrete wall and drift bolted to it. The legs of the unloaders are 32 feet center to center and span two standard gage tracks 12-foot centers. The main frame consists of a stiff structural frame work, supporting a double cantilever, the front end of which is hinged so that it can be raised or lowerd to a horizontal posi- tion. The peculiarity of this boom is the extension at its extreme outer end, which can be raised out.of the way when working in a narrow boat so as not to block the river channel, or which can be lowered to extend the boom in case a particularly wide- beamed boat is being unloaded. Traveling on a double rail horizontal track supported on the frame work above is a man trolley operating a six- ton Hoover & Mason grab bucket sus- pended by four operating ropes, two for opening and two for closing the bucket. The trolley track extends back over 40 feet from the rear leg over the V trough on the land side, supported 'on a cantilever extension to the main frame, while the boom allows the trolley to travel far enough out so that the bucket can reach the farthest side of a boat of 65 feet beam. These unloaders are the first Hoover & Mason machines to be built with horizontal booms and trolley tracks. Two 36-inch drums, each geared to a 125-horsepower motor mounted in the trolley frame are used to operate the bucket, one for closing and one for opening. The four bucket ropes are reeved over sheaves in the trol- ley, those from which the bucket is suspended being mounted on a rotat- ing frame operated by a 7'%4-horse- power motor. This latter arrange- ment allows the operator to swing the bucket either lengthwise of the hatch to enter it, or crosswise of the hatch so as to reach the ore between the hatches. * The trolley is equalized wheels, four of them being motor-driven. The operator is sta- tioned in a cab hung from the trolley frame and he controls all the motions the mounted on eight 17 of the bucket and the trolley as well from his cab. In addition to this, he controls the movement of the unload- er along the dock when moving from hatch to hatch, by means of foot lev- ers and controllers conveniently 1o- cated on the floor of the cab within his easy reach. The trolley track is provided with stops and electric safe- ty devices to prevent over-travel of the trolley in either direction, and a safety stop is provided on the front end of the main frame to prevent the trolley from traveling out over the water when the boom is up. The longitudinal movement of the unload- ers is accomplished by means of mo- tor-driven drums mounted on the front and rear truck beams, one on each leg. On. each drum 'is - wound several turns of l-inch cable, the two ends of the cable being carried to opposite ends of the unloader runway where they are securely anchored. By rotating these drums, one set of ca- bles is wound in while the other set is unwound. Both drums are con- -nected by shafting and gearing to two 35-horsepower motors mounted on the main frame beside the weighing hop- pers. This arrangement for longitudinal travel provides for two ropes leading in opposite directions from a drum on each leg of the six machines, conse- quently there are six ropes running to the anchor at the end of the runway from the front legs and six to each anchor from the rear legs. The drums are so placed that these ropes do not interfere with each other and each ma- chine can be moved independently of the others. A brake is provided on horizontal connecting shaft on the frame, which is powerful enough to hold the machine from skidding on the track. The boom is raised and lowered By means of cables, which are so reeved that the boom itself can be lowered until its weight is carried on the boom rods--that it, until it is hori- zontal--without disturbing the boom extension. Then by slacking still further on these same cables, the boom extension is lowered into a horizontal position. When raising the boom the extension is automatically folded up at right angles first before the boom proper begins to lift. The boom hoisting drum is located. just behind the connection of the mast brace, with the main tower on top of the frame, and is driven by a 50- horsepower motor, operated by levers and controllers on the main frame within easy reach of the .man in the