Differential pulley load, and an endless rope looped around the pulleys. To avoid slippage, the rope is usually replaced by a chain, and the connected pulleys by sprockets. The two sections of chain carrying the single pulley exert opposing and unequal torques on the connected pulleys, such that only the "difference" of these torques has to be compensated manually by pulling the loose part of the chain. This leads to a mechanical advantage: the force needed to lift a load is only a fraction of the load's weight. At the same time, the distance the load is lifted is smaller than the
Wire rope spooling technology One is a fleet angle compensator, which is driven automatically by the rope tension. The other is a level winder that is mechanically driven. Both offer a solution to guide the cable along the drum between flanges, but each has its advantages and disadvantages. The fleet angle compensator (FAC) is driven by the movement of the wire rope as it goes through the crossover sections of the drum. As the rope winds or unwinds, the FAC shaft automatically oscillates slowly, allowing its sheave to slide back and forth across the shaft to maintain an optimum fleet angle and guide the