The Mechanical Handling and Storing of Material

COAL TIPS OR HOISTS 581 also the power necessary for the working of all auxiliary apparatus on the hoist, including the jib crane, adjusting of shoot, and shoot point, etc., the current consumed over the whole period only averaged one unit per 6’94 tons of coal shipped. As emphasising tie adverse conditions under which the hoists are at present working, it will be noted that 70,604 wagons were handled in shipping 556,419 tons of coal, or an average of only / <-< tons of coal per wagon. Referring again to the coaling of 10th February 1909, a note was taken of the speed of working under ordinary conditions, when thirty wagons were shipped into the vessel in thirty-one minutes thirty-seven seconds, which is at the rate of fifty-seven wagons pei hour, the height lifted being 27 ft. 10 in., and the total weight of coal shipped 2o2 tons 14 cwt. Had the wagons been as large as the hoists are constructed for, the total quantity of coal shipped would have been at the rate of 1,140 tons per hour. As mentioned above, these results are tabulated in Table 3, and, in order to enable a comparison to be made with the results obtained at Newport, these results are adjusted in Table 4 to an assumed height of lift of 46 ft. From this table it will be noted that, while the average quantity of coal per lift given by Mr Macaulay was 11 tons 2 cwt., 01 Rothesay Dock it was only 8 tons 8 cwt. 1’9 qr., so that electric hoists with wagons containing a similar quantity of coal to those at Newport could have loaded an additional 117 tons, making a total of 477 tons 6 cwt. per hour. Referring to Table 4, it will be seen that the consumption of energy for coaling by electric hoiste, including distribution losses, is 0-131 unit per ton of coal shipped when working to a height of 46 ft. This at Id. per unit is equivalent to 10s. lid. per 1,WU tons of coal shipped. „ . f For coalins? by hydraulic hoists the consumption is shown to be -5,—0 gals, o water, which at' 9d. per 1,000 gals, is equivalent to 18s. lid. per 1,000 tons of coa shipped, showing, a saving of 8s. per 1,000 tons in favour of electricity. With reference to the comparative cost of generating hydraulic and electiic powei, it may be here mentioned that the above figure of 9d. per 1,000 gals, has been assumed as a fair average of the varying figures obtainable. Respecting the question of economic working, experience has shown that even wi i the additional load due to the added power requirements at the dock—rendered necessary by the installation of two additional hoists—the actual costs as regards current, cost o maintenance, and upkeep of plant, are well within the figures originally estimated. Attention might be drawn to the fact that the most economical speed at which to run tips for shipping coal is 100 to 120 ft. per minute ; many tips run faster, 150 to it., but in consequence they have to wait for something, either trucks getting on or off, or for