The Mechanical Handling and Storing of Material

TRANSPORTERS, BRIDGE OR CANTILEVER CRANES 423 near the quay front should be taken up by the machines, and that cranes could pass between the coal heaps and the transporters. Each machine is provided with a 2-ton grab, and can discharge coal from the collier to the centre of the coal yard at the rate of 100 tons per hour. The length over all of the transporters is nearly 400 ft., and the height of the lower chord of the bridge above rail level is 34 ft. The depth of the bridge is 19 ft. This method of unloading coal costs ^d. per ton, which includes driver, and current consumed. The special advantage of this system is, that when handled by these grabs, the coal can be stored to a greater height than when handled by bucket, and whereas coal is never stacked, in British dockyards, more than 18 to 20 ft. high by buckets, it is often stored to 34 ft. by transporters and grabs. This means an increase in the capacity of the store ground of nearly 100 percent., which often proves to be of very great value indeed where the store ground is restricted. Careful observations show that heating does not take place when this depth of coal has been stacked by these grabs. It is claimed for these transporters that they are more economical in working than the rope-haul system. Other advantages claimed are : that the driver has a perfect view of his work under all conditions; the track is not confined to a straight line; the parts to be kept lubricated are all collected in one cabin ; and all rope sheaves are entirely omitted. The power required to drive is less in this system, as very little is lost between the gear and the grab compared with that lost when ropes have to be led around a large number of pulleys. This installation was erected by Fraser & Chalmers, Ltd., of London and Erith. Coal-Handling Plant at Duluth.1—A coal-handling plant which is said to be the largest plant in the world for handling bituminous coal was completed in 1911 at Duluth, Minn., for the Pittsburg Coal Dock Co., a subsidiary of the Pittsburg Coal Co. The plant is designed for unloading coal from lake boats to the storage yard, and for loading on to cars. An interesting feature of the plant is a mechanical screening apparatus of new design and large capacity. The plant has a storage capacity of 1,000,000 tons, and an unloading capacity, as shown by recent tests, of 900 tons an hour, including the delay in cleaning up the holds of vessels unloaded. While working in free coal it is estimated that the plant will discharge 1,500 tons an hour from a boat to the storage yard. The plant was designed and erected by the Brown Hoisting Machinery Co., Cleveland, Ohio. The coal-handling equipment includes three two-span bridges, shown in Figs. 596 and 597, extending from the unloading dock and two single-span bridges. Each span is of 242 ft. The yard is covered by the bridges, which are operated back and forth on a runway 1,250 ft. long. Each two-span bridge and one of the single-span bridges is equipped with a man trolley, which carries a two-rope Brown grab-bucket, with a capacity of 230 cub. ft. or 5 j tons, and an operator’s cab. The single span bridges are arranged to register with any of the two-span bridges so as to make a three-span bridge or a continuous runway for a trolley over any one of the two-span bridges, and one of the single spans, a total distance of 726 ft. The operating mechanism is arranged so that when a single-span bridge is connected with a two-span bridge the three spans are operated as a unit. The single spans may also be operated as independent bridges. The single span not provided with a trolley is operated by using one of the trolleys from a two- span bridge. The two-span bridges have a cantilever extension of 78 ft. out over the dock From The Iron Age of 7th December 1911.