The Mechanical Handling and Storing of Material

CHAPTER XXXI TRANSPORTERS, BRIDGE OR CANTILEVER CRANES Perhaps one of the most important improvements that has been effected of late years in the mechanical handling of material is in connection with discharging ships to granaries, warehouses, or stock yards erected on or near the quay side. The first step in advance which superseded hand labour was taken when cranes were erected and used for the clearance of cargoes. At this stage it became the practice to fill coal in the ship into skips of cylindrical shape, which were hoisted and then dis- charged through a hinged door into the trucks. This system is still in use to a considerable extent, but it has the disadvantage of calling for an inordinate amount of hand labour, and is therefore economically wasteful. An improvement on this method is the use of grabs which generally require a special kind of crane, and will effect a sensible saving in time. In later years the hoisting crane or tiansporter has been combined with a bridge or gantry which commands the whole length of the quay side, store, or yard. In or on these gantries mechanical means for conveying the material are erected, and every operation incidental to the reception and further handling of the material is effected by machinery. Such installations have been variously called transporters, bridge or cantilever cranes. They can be either steam or electrically driven, and it is claimed that the first of the latter type were erected in 1901 by the Brown Hoisting Machinery Co. for the North- Western Fuel Co.1 They can be divided under two general heads :— ( a) Transporters in which the winding gear is mounted in a movable cabin, and accompanies the load from the ship to the point of delivery. ( ^) Transporters in which the winding gear is situated in a cabin fixed in the structure of the crane, and is connected by cables and chains to the running head which carries the load. TRANSPORTERS WITH MOVABLE WINDING GEARS These transporters are perhaps not so much used as those with stationary winding gears, probably for the reason that the structure has to be erected on a more substantial scale, and is therefore more expensive. It has, however, several advantages, the principal one being that the handling of the material is better under control of the attendant as he accompanies the load in his cabin, which also contains the winding gear and motor. Such transporters are numerous, but as they all bear a great resemblance to each other, it will suffice to give only a few examples. Electrically Driven Grab Transporters at the Coal Yard of the British Admiralty at Devonport.—The British Admiralty have erected four electrically driven grab transporters, forming one installation, part of which is illustrated in Fig. 595. It l Described by Mr G. H. Hutchinson, chief engineer, North-Western Fuel Co., in his paper pre- sented to the American Society of Mechanical Engineers. 421