The Mechanical Handling and Storing of Material

COAL TIPS OR HOISTS 577 level inclined viaduct, leaving the hoist platform or cradle at a height of about 17 ft. from the ground and gravitating to the siding, the cradle then being lowered to the ground level to receive the on-coming loaded wagon. Hoist No. 1 is fixed on the east quay of the outer basin, and No. - on the nor quay of the inner basin, No. 1 being suitable for lifting to a height of 50 ft. and No. - to a height of 60 ft. Each hoist is capable of raising, tipping, and lowering wagons carrying 20 tons of coal, with a gross weight of 32 tons, as well as those of the ordinary type at present in use holding 6 tons and upwards. . It is always expedient to decide the working speeds of dock appliances in relation to the complete cycle of operations of which they form a part, but this is particularly so in the case of coal hoists, as so many operations are involved in addition to the actua hoisting of the load, that a high speed of hoisting, while causing a considerable increase in the first cost of the machinery and also in the power required for working, does not result in a corresponding high rate of coaling, unless it is possible to deal with the other operations—such as disposal of coal in the ship, getting into position of the loaded wagon, and the running off of the empty wagon—so expeditiously that advantage can be taken of a hieh hoisting speed. . After careful consideration of the cycle of operations necessary to ship the maximum Quantity of coal, under the system of coaling generally in vogue at docks on the Clyde, where end-tipping wagons are used, it was decided to adopt a mean hoisting speed, allowing for acceleration and retardation, of about 100 ft. per minute with fu oa , corresponding to a time of thirty seconds for the full height of 50 ft.; this speed, ».th a full unbalanced load and a combined mechanical and electrical efficiency of i „ per cen being equivalent to about 300 E.H.P. in the motor. . . . Perhaps the most difficult motion of a coal hoist to deal with electrically is the tipping, as this has to be accomplished very expeditiously through a comparatively short distance, usually a maximum of 45’,' and with a degree of accuracy very d.fficult to attain under such varying conditions and loads. It is always necessary to accelerate qu.ckly, and sometimes to stop suddenly and thus give an impetus to the material being shipped, so that it will leave the wagon without sticking. Frequently this motion has to e repeated through small angles of travel several times before the whole of the materia leaves the wagon. To tip the full wagons to a maximum angle of 45 in six to nine seconds requires power almost identical with that for hoisting, so that the motors lor the two motions are duplicates. The design of the structural work and arrangement of shoot, jib cranes, and othe auxiliary apparatus is on the usual lines, the essential difference being that all the gearing is at the top of the structure, which has been designed to carry this additional weight, and not, as at Rotterdam and Emden, in as eparate building by the side of the hoist. As mentioned above, separate motors are employed for the hoisting and tipping motions. The hoisting motor drives, by means of an elastic coupling and also an ordinary jau- coupling, a pinion which engages with a spur wheel upon the countershaft this spur wheel and pinion running in a cast-iron casing. At each end of the counters a t a pin o is fixed which engages with the spur wheels firmly fixed to the hoisting drums, the drums being so arranged that the ropes go directly to the cradle without the intervention of guide pulleys. The whole of the gearing, with the exception of the motors, is erected 1 It has been observed by Mr William H. Patchell that in tipping a full truck of large coal it- coul<^ clone at a comparatively low angle, probably 38°, but in tipping small coal, particular j 1.1 , , washed, there was some difficulty in emptying it out at 45° ; and if for any reason the tipping had interrupted and there was half or quarter of a truck still to tip, it had to be practica j ia ec 37