A moving crank mechanism that is particularly adapted for use in a conveyor system. A moving crank remains in a substantially parallel position with respect to a fixed reference plane as the crank member is driven by its offset opposed ends along an endless loop. The closed loop vertical lift unit is adapted for use in an automated high-speed storage system. The vertical lift unit is adapted to be used as a primary storage location or as a lift for carrying objects in transit between levels in a storage system. The vertical lift unit includes a plurality of crank members with generally rigidly mounted shelves that are adapted to carry objects continuously and indefinitely as the shelves travel through a vertically oriented closed path. While traveling along the vertically oriented closed path the shelves remain parallel to a fixed horizontal plane so objects can be carried on the shelves while the shelves transition between the up and down reaches of the vertical lift mechanism. The opposed ends of the crank member are journaled in carriage members that are mounted to carry the respective ends of the crank member around the closed loop. The respective ends are carried around the closed loop at about the same rate. The closed loops are offset from one another by the amount of the crank offset. Shelf stabilizing mechanisms can also be employed.