The Mechanical Handling and Storing of Material

564 THE MECHANICAL HANDLING OF MATERIAL want of a simple and efficient coal tip. The traffic in coal for export as well as for navigation purposes had grown enormously. The annual tonnage, which did not amount to 50,000 tons in 1890, had in 1900 grown to nearly half a million tons. The tip—which was the first to be erected on the Continent and which is illustrated in Figs. 788 and 789—was built more or less on the lines of the tips in use at English ports, and its construction was entrusted to Sir W. G. Armstrong, Whitworth, & Co., Ltd. It was erected in 1887 and did most satisfactory work. It was driven from the existing hydraulic mains at the harbour, which are under a working pressure of 900 lb. to the square inch, and was for trucks holding 10 tons of coal, and designed for a lift of 33 ft. Shortly after the starting to work of this tip the increased traffic rendered it necessary to double the capacity, and a second tip was ordered from the same firm, this time for trucks holding 15 tons and for a rise of 40 ft., the latter to be accomplished in thirty-six seconds. Fig. 790 is an illustration of this tip. The first hydraulic tip at the port of Rotterdam is suitable for all four-wheeled trucks used on lines that terminate at or have connections with Rotterdam. The framework is principally constructed of rolled girders, but wood is also used, p represents the cradle or stage for the reception of the trucks to be discharged. It is suspended from four chains at c and d, and is actuated by the hydraulic rams x, x, the former of which has a larger diameter, with four sheaves h and Z, and works downward, whilst the latter, x, is smaller, works upward, and is fitted with only two sheaves g. The chains which are connected to the stage p, at c, are guided over the sheaves e,fg, h to the hydraulic cylinder, and are attached at point E. Other chains lead from d to f over the sheaves z, k, I. When the stage is in its lowest position, and the hydraulic ram x is forced down,