The Mechanical Handling and Storing of Material

566 THE MECHANICAL HANDLING OF MATERIAL from the large shoot, as already mentioned, for preventing breakage of the coal. The chain is manipulated by the hydraulic cylinders _y, and the sheaves u and v. It is further guided over pulleys q, v, s, t. For the side movement of the crane an additional hydraulic cylinder z is provided. The hydraulic pressure which works the tip is 750 lb. to the square inch, which is sufficient for ordinary trucks, but when trucks of 15 tons’ capacity have to be tipped, the pressure can be increased to 900 lb. per square inch. The two tips sufficed to cope with the traffic until about 1898, when they were working almost day and night, and it was decided to erect a third tip. As the hydraulic power supply of the harbour authorities was taxed to its utmost limits after the erection of the second tip, and as some trouble had been experienced caused by the frost, and breaking of the mains through sinkage of the ground, it was decided to drive the third coal tip by electricity. The Electrically Driven Tip at the Harbour of Rotterdam1 is the design of Mr H. A. van Ysselsteijn, engineer to the city authorities. Messrs Nagel & Kaemp, of Hamburg, constructed the tip, while the electrical plant was the work of Messrs Siemens & Halske, of Berlin. The order for the third tip was passed to the contractors in 1897, but owing to some unforeseen delay it was not started to work until the beginning of 1901. This electric coal tip is illustrated in Figs. 791, 792, and 793. The general dimensions are similar to those of the tip illustrated in Fig. 778, which was built by Sir W. G. Armstrong, Whitworth, & Co., Ltd., but the framework was made stronger. The special novelty in the design is this, that the driving gears controlling the different motions have been placed in a separate engine-house erected close to the tip, each movement having its own electro-motor. Another feature peculiar to this third Rotterdam tip is that the delivery shoot is so constructed that it can be extended if coal has to be shipped into vessels of extra wide beam. It is thus equally suitable for loading coal into ocean-going steamers or into vessels for river and canal traffic. The wagons are drawn to the tip by an electric capstan, and are pushed upon the cradle; after discharging, they are returned on another line of rails. The framework is, as has already been stated, similar to that of the Armstrong tips, but there are four uprights on each side of the cradle, the two centre ones of which also act as lateral guides for the up and down motion of the cradle. The four uprights on each side are stiffened by trussed girders, which are secured to a substantial foundation. The main uprights are girders of I section, and are composed of and riveted together with angle irons. The struts are made of channel section. The bases of the uprights are secured to cast iron footplates, which in their turn are secured to the foundation. The arrangement of the winding gears for the different movements of the tip in a common engine-room has been adopted because it is held that the gears are thus under better control, and can be kept under the super- vision of one man, whereas, if they were situated at the different points where their action was required, each individual winding gear would require its own compartment to protect it from the weather. It would also, under such conditions, be altogether impossible for one man to manipulate all these gears. The slewing gear for the anti-breakage crane has been erected in the cabin of the operator, as may be seen in the illustration. This is the only part of the machinery for operating any portion of the coal tip which is not situated in the engine-room. Although the winding gears have been erected in the engine- house, they are all under the complete control of the operator, who can stop or start any of them from his cabin at the top of the tip. The connection between the operator’s cabin and the engine-house by means of levers would have been exceedingly complicated. All connections, therefore, are electrical, even the brakes on the winding machinery being 1 Illustrations reprinted from Zeitschrift des Vereines dentscher Ingenieure.