The Mechanical Handling and Storing of Material

582 THE MECHANICAL HANDLING OF MATERIAL the trimming work on the vessel. With the moderate speed of 100 to 120 ft. one truck per minute can be shipped with a tip of any height. The higher speeds entail heavier power plant, higher wages, more damage to wagons, and more wear and tear all round. In comparing the merits of electric and hydraulic tips, Mr G. H. Baxter also states that for varying loads the electrical power adjusts itself quite economically to the load, a condition impossible to obtain in hydraulic tips, although considerable improvement has been obtained by the employment of multiple rams. This, however, 'can only be considered as a partial solution of the problem, as it depends on the discretion of the man in charge as to what number of rams he will use. As a matter of fact, when manipulating tips with trucks of varying loads, as is the case on the Clyde and other docks, it is practically impossible to make the necessary adjustments at every position for the most economical working, whereas electricity adjusts itself quite automatically to the varying conditions. Mr Aspinall has collected some interesting information concerning the time wasted during the twenty-four hours in the use of coal tips, as well as of ordinary coaling cranes. This information was given by him when presiding at the Institution of Mechanical Engineers during the reading of the paper by Messrs Dixon and Baxter. Mr Aspinall does not mention the docks at which these figures were taken, but he mentions that 1,000,000 tons of coal are handled per annum. Test of Three Months’ Work, showing Percentage of Time Occupied in Each Kind of Operation Two Hoists Combined. Two Cranes Combined. Tipping and handling - Waiting ships- - - - Waiting coal1 ------ Adjustment of shoot _ . - - - Swinging and changing ----- Trimming in holds ------ Meal hours ------- Other causes ------- Per Cent. 53’49 8-24 114 3-07 4-89 12-25 15-75 1 17 Per Cent. 64-19 5 04 1-38 3'88 8 "24 15-28 1 -99 100 00 | 100-00 This leaves the time actually occupied in tipping, handling, and packing the coal on to the boat 53'49 per cent, in the case of a hoist, and 64’19 per cent, in the case of a crane, being a clear gain of 11 per cent, in favour of the crane. M'Myler Coal Tips.—The tips built by the M‘Myler Manufacturing Co., of Cleveland, Ohio, are for the purpose of discharging cars which need neither be hopper- bottomed nor have hinged end doors for unloading. The trucks are tipped by rolling them over laterally when they have reached the required level in the tip. Such a tip is illustrated in Figs. 826 and 827, and consists essentially of a steel tower, similar to the Armstrong type of tip, which forms the guide for the cradle ; the latter is provided with a rigid side towards the vessel to be loaded. Wire ropes are attached to the top of this side, passing upwards over the guide pulleys to a counterweight running in a groove at the rear of the tower. The hoist ropes are attached to a lower point on the same side 1 This refers to the time occupied in getting the trucks on to the tip or on to the crane.