Hoisting engines are provided with powerful brakes and frequently with reversing gear.
Self-acting tanks are occasionally built underneath the platforms of hoisting cages.
The special difficulties which attend deep mining, in addition to the problems of hoisting ore and raising water from great depths, are the increase of temperature of the rocks and the pressure of the overlying strata.
Of the drum depend on the hoisting speed desired and the depth of shaft or length of rope to be wound.
If, for a twocompartment shaft, a pair of drums (or a single wide drum) be keyed to the engine shaft, with the ropes wound in opposite directions, the hoisting is " in balance," that is, the cages and cars counterbalance each other, so that the engine has to raise only the useful load of mineral, plus the rope.