True vertical lift is when the hook of the hoist (lower block) moves in a true vertical path between the lower limit of travel and the upper limit of travel. This happens when the rope(s), anchored at each end of the drum, winds from the center of the drum outward (inward when raising the hook); enabling the hook and load to be centered below the middle of the drum. This design prevents the hook from wandering from one end of the drum to the other in the highest and lowest hook position.
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