A plurality of flat timing belts each has parallel spaced teeth, and opposite end portions of each belt are attached to a carriage by corresponding relatively adjustable clamping blocks and plates. The belts extend around a common drive sprocket on a drive shaft connected to a drive having a reversible electric motor. The belts also extend around corresponding tail sprockets on a tail shaft, and adjacent tail sprockets are free to rotate relative to each other. A clamping block for each belt is adjusted to obtain the same tension in all belts so that each belt may be operated at its full rated capacity. The belt drive system may be used for transferring or shuttling a plurality of tool trays laterally with respect to a working station at a conveyor assembly line and storage stations on opposite sides of the working station.
