The Mechanical Handling and Storing of Material

COAL TIPS OP HOISTS 575 The Electric Tips at the Rothesay Dock on the Clyde.1—These tips are a vast improvement on those of the Continental type previously described. The question was raised as to whether hydraulic. or electric power should be employed by the Clyde Navigation Trustees, and in order to ascertain which of the two was more economical, two cranes were erected side by side in the Princess Dock, one being manipulated by electric and the other by hydraulic power. These were observed closely for a considerable time, and the result obtained was so favourable that no doubt was entertained as to the advant- ages of electricity for dealing with the ordinary class. of machines such as cranes, capstans, etc. Ihe installation of several large coal tips, however, rendered the problem one which had not hitherto been faced in this country. The mechanical difficulties in connection with such hoists had already been solved at Rotterdam and Emden, but the difficulty of dealing electrically with a large amount of horse power required in a very short period, together with the necessity of providing for rapid acceleration and retarda- tion, and absolute control under all conditions, will be readily appreciated. It was at this stage recognised that the problem had developed into one which c'ould not be adequately dealt with by the mechanical engineering department, without expert electrical advice, and Mr Walter Dixon was appointed to collaborate with Mr Baxter, chief mechanical engineer to the Trustees, in the preparation of the scheme to em- body the complete equipment of the dock. The Power Station.—It is generally recognised that where a reliable supply is available it is desirable to take advantage of such supply and thus obviate a considerable capital expenditure. In many cases, however, an objection arises to this course, as the supply available is usually on the three-phase alternating current system, which, while it may be satisfactorily employed, is not so suitable for dock purposes as a direct current; so that if the best results are to be obtained, an appreciable portion of the capital which might otherwise have been saved by dispensing with steam- raising and generating plant, might have to be used for providing, converting, and transforming plant. In spite of such a supply being available at Rothesay Dock, it was deemed best to erect a generating station, as it was hoped Figs. 823 to 825. Section through Cabin, also Plans of Top that the electric supply would be produced at lower cost and Bottom Floors. by a plant specially designed for the purpose. The generating station, comprising boiler, engine, and condenser houses, suitable 1 Abstract from a paper on the “Modern Electrical Dock Equipments,” with special reference to electrically operated coal hoists, read on 20th January 1911 by Messrs Walter Dixon and G. IT. Baxter before the Institution of Mechanical Engineers, with the Author s comments.