One of the difficulties met in skip hoist design is that commonly the hoisting rope must run over a sheave located at the upper end of the skipway and come back over the top of the skip in order to be out of the way of the stock when the skip dumps. This brings the rope above the skipway while the hoisting engine is generally most conveniently located underneath the skipway.

Various arrangements have been used to overcome this difficulty. In one design a truck is used which carries the skip at its upper end and practically pushes it up the incline, the skip being pivoted to the truck and having an auxiliary pair of wheels in the front. In this case the sheave is put below the skipway and is far enough below the skip when it dumps to be out of the way. This puts the rope under the skipway where it is most desirable to have it.

In a number of cases the ropes have been carried clear over the top of the furnace, and the hoisting engine placed on the opposite side in order to overcome this difficulty, while in one well known type of top two guide sheaves are used on each skip rope, in addition to the main hoisting sheave, in order to get the rope out of the way at the top and pass it back underneath the skipway.

In the Brown design of skip hoist the difficulty is solved by the use of the single skip, and by putting the hoisting sheave in a plane parallel with the skipway as shown in Fig. 16 so that the hoisting rope can be returned over one side of the skipway to the engine house beneath it.

Probably other solutions of this apparently trivial problem have been attempted or made, but these are the ones best known and most used.

Dumping The Skip

The method for turning the skip over to dump is universally the same. The main rails of the skipway bend down from the incline and run in level when they reach the top of the hopper, but there are two additional rails set to a somewhat wider gauge which continue on in the main line of the skipway. These are set far enough apart so that the front wheels can pass through them without touching, all the wheels being outside the skip. The rear wheels have a supplementary tread outside the regular one, which comes onto these supplementary rails just where the main rails bend down from their straight line. This carries the rear wheels on up while the front ones go forward on a level line, and in something less than twice the length of the skip it is turned up to an angle of forty-five degrees or more and so emptied completely.