The Mechanical Handling and Storing of Material

578 THE MECHANICAL HANDLING OF MATERIAL upon a cast-iron bed-plate to obviate errors in erection, and both motors are mounted upon one base-plate, which is bolted to the gearing base-plate. For the purpose of taking up the slack of the tipping rope during the raising of the platform, a third drum, of barrel shape towards one end, is connected to one of the hoisting drums. The tipping motor is a duplicate of that for hoisting, and the gearing generally is similar, excepting that only one drum is employed. In view of the heavy loads to be dealt with, and the precision with which the cage and tipping cradle have to be brought to a stop at any predetermined position, the brake gear is of great importance. The brakes for both hoisting and tipping are of the friction clinch type, the brake bands being kept tight during the hoisting, and the clinches revolving freely in the hoisting direction. By this means the load is held in suspension immediately power is disconnected from the motor. In lowering, the brake bands are released by electro-magnets in the usual way. Due to the fact that the hoisting and tipping motors are duplicates of each other, it has been possible to provide a simple arrangement by means of which one motor can work both motions in case of breakdown to either motor, thus enabling coaling to be proceeded with and avoiding any serious delay in the departure of a vessel. There is only one control lever, which works in a quadrant or frame, and by moving this lever in the various positions the attendant has control of the hoisting, tipping, and jib crane, the only other controller being a small one for controlling the slewing of the jib crane. Gearing is arranged in connection with this control-lever frame, which automatically renders it impossible for any of the motions to exceed their predetermined efforts, and it is also impossible for the attendant at starting to move the lever at such a rate as to accelerate at too great a speed and consequently throw an undue load upon the generating station. In fact, at all points of possible danger, the automatic adjustments come into operation, and prevent any damage from error of omission or commission on the part of the attendant. In actual working it has been found that the control is so perfect that the cradle can be brought to rest quite smoothly at any desired position, and in a similar manner the tipping platform can be quite smoothly stopped at any desired position. I he wagons while on the hoist and when being run off are thus protected from the rough usage to which they are frequently subjected during coaling operations. In Table 1 the specified cycle of operations is tabulated, from details obtained at the official trials. Comparing these with the results tabulated in lable 2, which were obtained in February 1909, after two years’ working, it will be seen that the time required for coaling through the cycle of operations is considerably shorter. Since the first two coal hoists were erected and set to work, two additional hoists have been installed, practically duplicates of the first two j for the result of some years working did not suggest any modification or improvement for the further hoists, the only practical difference being that the two later hoists were for a higher lift. Efficiency.—At the official trials in May 1907, which were taken when the hoists had done practically no coaling under actual working conditions, the following readings were taken upon hoist No. 2 :—- Total unbalanced load - - - 32 tons 0 cwt. 1 qr. Height lifted - - - - 60 ft. Time hoisting - - - - 36 seconds. Speed of hoisting - - - - 100 ft. per minute. H.P. due to load - 217’3 load H.P. Current - 500 amperes. Voltage ----- 450 volts. Electrical H.P. - 301'6.