Fig. 16
Fig. 17
If the material comes to the slope as shown in [Fig. 17], it is necessary to let down a bridge a, on which the car runs, in order to reach the skip. After the car is dumped, the bridge is lifted out of the way into the dotted position, so as to leave the slope unobstructed.
19. Method of Dumping Skips. To dump a skip at the surface, the tracks are extended above the slope mouth, as shown in Figs. [18] and [19], and are arranged so that the material may be dumped directly into a bin or into cars as desired.
In the arrangement shown in [Fig. 18], the front wheel of the skip strikes a stop a and, since the bail of the skip is pivoted far down toward the lower end, as the rope continues to pull, the rear of the skip is raised and the material is dumped. The objection to this method is that if the rope is slightly overwound the skip is pulled off the track and does not then right itself on the track when the rope is released.
Fig. 18
In the Lake Superior iron and copper region, many of the dumps are built as shown in [Fig. 19]. In this dump, the rails of the main track a are curved as shown at b; a short distance back of the beginning of this curve, another track c begins outside the track a and runs in a straight line parallel to the inclination of the hoist. The track c is of a wider gauge than a, and the rear wheels of the skip have a wider tread than the front, so that they will run on c while the front wheels take the curved track until they strike the stop d. The rear of the skip will thus be raised and the material dumped. There are but two tracks in the main part of the slope.