An endless loop conveyor system is disclosed wherein a plurality of carriers are moved to one or more work stations and one or more buffer stations so that a product may be assembled on each carrier at the work stations. Power is extracted from a continuously moving belt by holding the belt against a power wheel with an L-shaped member. A variable ratio transmission having a pair of power transmitting wheels, one contacting the power wheel, the other contacting a drive wheel, uses the extracted power to accelerate or decelerate each carrier depending on the locations of contact. A non-contacting position is provided for rest at a work station.
