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minute or to the moving of ore by means of grab buckets that scoop up automatically anywhere from two to ten tons at each operation; and yet, as has been said, less than thirty years has been required to work this amazing transformation.
The conditions governing the movement of iron ore and coal in the United States are peculiar in that several rehandlings are necessary. The major portion of the iron ore is mined in the States of Minnesota, Wisconsin, and Michigan; transported by rail to ports on Lakes Michigan and Superior; and then loaded on vessels which in some instances carry it to blast furnaces located directly on the shores of the inland seas,
iron ore, and are subject to the same rehandlings.
The pioneer inventor who successfully solved the problem of handling coal and iron ore over a considerable range of distances solely or largely by mechanical means, was Mr. Alexander E. Brown, the well-known American engineer, the machines of whose invention are to this day accepted as the standard—and are indeed the sole—means of performing many of the functions in this highly specialized field.
Bridge Tramways At the outset all the operations of transferring iron ore from ships to cars
but which more frequently transport it to or stock piles, as the same might be, and harbors on the south shore of Lake Erie, of both loading and unloading coalwhere there is a transfer from the vessels carrying vessels to and from cars or stock to railroad cars, in which the ore is moved piles, were confined to a single class of to the blast furnaces of that great iron apparatus-hoisting and conveying mamanufacturing section known as the chinery of what is known as the "bridge "Pittsburg District." Here, finally, there tramway” type ; and this form of handis still another rehandling when the ore ling appliance is yet so extensively used which has been placed in stock piles is, in moving both commodities as to merit as occasion requires, conveyed to the fur first attention aside from its claim by naces. The anthracite coal from the reason of priority of invention. Pennsylvania field, and the bituminous A bridge tramway is, in effect, a minifuel from the mines of Ohio, Pennsyl ature elevated railway along which loads vania, and neighboring States, which are are conveyed by the trolley system now shipped to points in the West and North so extensively employed in the industrial west, traverse in the opp te direction field. The skeleton bridge structure-suppractically the same route followed by the ported at both ends by piers—is built of
iron and steel designed to give the maxi the proper lever, and hoists the bucket mum strength with the minimum weight at full speed through the hatch of the of material, and with all members made boat, the bottom block hooking autoof such shapes, and so arranged in the matically into the trolley, and the trolley trusses, as to offer the least possible sur carrying the heavily laden bucket to a face to wind-pressure—an important con point on the bridge or cantilever where sideration owing to the exposed locations its progress is arrested by dumpingin which these machines are generally irons placed at any desired location. used.
These irons automatically trip the latch The bridge tramways proper usually range from 180 to 192 feet span; but, extending from the front pier, is a 34-foot apron reaching from the front of the dock out over the vessel tied up for unloading, while from the rear pier is a cantilever extension stretching back from 80 to 104 feet additional. Thus an area more than 300 feet wide is served by the tramway. The piers are of steel construction, and are high enough to support the bridge on an incline with the front end about 27 feet above the ground and the rear end 52 feet above the level. The piers are mounted on wheels running on tracks, so that the whole structure may be “skewed" or moved sideways back and forth along a dock to suit the hatches of a vessel. Thus a vessel may be u11loaded by having several bridge tramways operating simultaneously over as many different hatchways or openings in the deck; or the cargo may be removed
"CLAM-SHELL" BUCKET FOR AUTOMATIC UNLOADING. by a single tramway adjusted so as to
Showing Operator in Mast. operate in first one division of the hold and then another, by means of the side
of the bucket, allowing it to upset, diswise movement of the apparatus.
charge its load, and automatically right Running along a track suspended from itself. As soon as this is done, the opthe bridge between the girders, is a trol erator releases the lever, and the bucket ley with suspended bottom block and returns by gravity to its starting point hook to which is attached the hoisting in the hold of the vessel. The block or pulling line, and all the motions of unhooks automatically from the trolley, which are under perfect control of the allowing the bucket to be lowered into operator by means of suitable levers. Up
the hold, whereupon the empty bucket is and down this trolley line, at a speed of unhooked and a filled one hooked on. If hundreds of feet per minute, travels an preferred, the operator, instead of allowiron tub or bucket in which the ore or ing the bucket to dump automatically, coal is carried. These buckets are made can lower it to any desired point for disin various sizes; but what might be charge, this being desirable when it is the termed the standard size has a capacity purpose to transfer the coal orore directly of seventeen cubic feet (or a gross ton) to waiting railroad cars.
One of the buckets such as have been The plan of operation is practically the described, will make a round trip from same in all cases. If coal or iron ore is the hold of a vessel to the end of a bridge being unloaded from a vessel, the oper tramway trolley line, and return—a disator, upon receiving from the hold of the tance of 600 feet—in one minute; and vessel a signal that a tub is filled, throws in actual work a rate of forty-five seconds
per round trip has been averaged for
Grab Buckets hours at a time. If the filling, handling, During the early history of the bridge and hooking-on of buckets be done with tramway plants, there was universal emreasonable dispatch, a single machine will ployment of tubs or buckets which, alreadily transfer 400 gross tons of ore per though self-dumping, had to be filled by day of ten hours. The cost of handling hand. As an improvement upon these, coal and ore by this means varies from there have been introduced various types seven-tenths of a cent to two cents per of self-filling and automatic dumping gross ton.
buckets which will handle from twoThe first bridge tramway plants were thirds to four-fifths of a cargo or conerected on the iron ore unloading docks signment of the bulk material without at Cleveland, Ohio, about twenty-five hand-shoveling. The most primitive years ago, and the new machines were forms of these self-filling buckets were for a time confined in their sphere of use “shovel" buckets of five tons' capacity, fulness to the empire of the Great Lakes. which scooped up their load through Gradually, however, they secured general being dragged against the slope of the
adoption, particularly for coal handling; coal or ore pile. Then came the "grab” and they are now to be found, not only buckets, descending with open jaws, on the Atlantic and Pacific coasts, but which, closing, took from the ore or coal in Germany, Austria, Russia, Sweden, pile a "bite" of one ton or more and held Egypt, and other foreign countries. the material securely until released at any Perhaps the best exemplification of the desired point of discharge. This class possibilities of this Yankee invention for of buckets were introduced, not only in coal handling, is afforded at the coaling connection with the familiar bridge tramstations of the United States Navy at ways, but also in conjunction with wireKey West, Dry Tortugas, Mare Island, rope cableways. The latter have been Cal.. and New London, Conn., where, utilized to some extent for coal and ore by means of bridge tramways such as handling, in locations where the span have been described, fuel is transferred necessitated was greater than could be directly from storage buildings (having successfully covered by a suspension a capacity of 10,000 tons each) to the structure of the weight of a bridge tramholds of United States war vessels.
by means of a clam-shell attachment--an The most recent advances in ore-hand- enlarged edition of the grab bucket—will ling machinery have been along the de take ten tons of ore from a ship's hold velopment of appliances possessing the at each operation, and by means of which
basic principle involved in the grab it is possible to remove every ounce of bucket above mentioned. The supreme ore from a cargo-hold, thus dispensing triumph in this field is found in the lately entirely with hand shoveling, and elimidevised automatic ore unloader, which, nating the last utilization of manual labor
a height of 55 feet. It consists the bucket has been closed by hydraulic primarily of a foundation trestle, which power, it is lifted from the boat and run is mounted upon wheels and which can back over the dock, where its contents be moved along the dock, the rails carry can, if desired, be discharged directly ing the forward end of the trestle being into the railroad cars which are to convey directly on the brink of the dock, as in the ore to the blast furnaces. Only three the case of the bridge tramways. Mov men are required in order to operate one ing backward and forward on this foun of these machines, which has a capacity dation span, at right angles to the dock, of 250 tons per hour. is a heavy walking beam, attached to the The world's record for the rapid handouter end of which is the depending leg ling of an ore cargo was made a short or mast that carries the clam-shell bucket time ago at the port of Conneaut, Ohio, used in dipping out the ore. The parallel when four of these machines, in a total motion keeps the leg always in a vertical working time of 4 hours 43 minutes, reposition; and the weight of the end of the moved from the steamer James H. Hoyt walking beam from which the bucket is a cargo of 5,300 tons of ore. All the suspended is counterbalanced by means argo was taken out by the machines, of a hydraulic accumulator located at the no cleaning up whatever by hand labor opposite end.