The Mechanical Handling and Storing of Material

474 THE MECHANICAL HANDLING OF MATERIAL The barge upon which the elevator is built is 65 ft. long by 26 ft. 6 in. over all, and has a depth of about 10 ft. 6 in. The power is generated on board by means of a high speed direct coupled generating set, the engine being built by Messrs E. S. Hindley & Sons, Bourton, Dorset, and the electrical machinery by Messrs Cromptons, <5f Chelmsford. The engine is supplied by suction gas from a plant using anthracite coal. The engine runs at 600 revs, per minute, and transmits continuous current at 110 volts, this voltage having been found most satisfactory for grain work. The current is supplied by means of a concentric connection under the elevator to a driver’s cabin attached to the side which contains all the various controllers. The motor for driving the conveyor is placed at the back end of the jib. Those for raising the jib and the telescopic leg are placed at the bottom of the post whilst the slewing motor is placed upon the turntable. They are each of 4 B.H.P. The deck elevator is driven by a direct coupled motor placed at the head of the elevator, of 9 B.H.P. The engines have a maximum output of 50 B.H.P., but the average used when working at maximum capacity does not generally exceed 30 B.H.P., of which about 14 is taken by the main elevator, and the balance by lights and auxiliary machinery. The whole of the operations for placing the elevator into the ship and controlling it are carried out by one man from the driver’s cabin, the time taken to get into the ship or out being about seven minutes. No use whatever is made of the ship’s gear except for the purpose of trimming the grain to the elevator leg. (In some of the earlier types the ship’s tackle had to be used to get the elevator leg into the hold.) A similar, but smaller plant, with a capacity of 100 tons per hour, was built by the New Conveyor Co. for the London Grain Elevator Co. Here the buckets are 10J in. apart and 320 buckets pass per minute. Two similar elevators, but constructed to run along the quay instead of being placed upon barges, have been constructed for the Co-operative Wholesale Society, Dunston- on-Tyne, as already mentioned. Floating elevator or marine legs may be preferable to the pneumatic system of unloading cargoes if the grain is stored in a convenient and accessible position, such as if a large hold without obstructions is to be emptied, as the driving power required per ton is only about 1 to 1£ H.P. or approximately half that consumed by a pneumatic plant. Unfortunately, however, such conditions do not often present themselves, in fact Mr Mowat states that at the Millwall Docks not more than 10 per cent, of the cargo is so stored that it can be handled by the bucket elevator. Cargo steamers, particularly from the Black Sea, contain sometimes many parcels of wheat which have to be kept separate, so that only hand labour or a pneumatic plant can do the work. A case may be mentioned of a ship which contained forty-seven parcels, which meant different handling for each parcel of grain. Each one had to be taken out care- fully by the pneumatic apparatus and cleared before the mats which separate the parcels could be removed to give access to the next parcel. It would be impossible to do this with elevator legs. In some cases the thickness of grain between the separation mats is not more than 2 ft. The only alternative to the pneumatic elevator in such cases is, as already mentioned, the old hand method of bushelling into sacks and making use of the ship’s winches and gear to hoist the grain on deck and tip it into barges alongside. Other difficult cases in which the marine leg is no good are those of cargo steamers EH