Speed control for gravity operated trolleys

A gravity conveyor comprising downwardly inclined track means, a trolley adapted to support a workpiece and supported on said track means for travel thereon in response to the gravitational force on the trolley, said trolley being supported on said track means by a pair of separate track-engaging wheels, said trolley and track means being designed so that one of said wheels engages the track means when the trolley is empty and the other wheel engages the track means when the trolley is loaded with a workpiece, a first means for applying a retarding torque to said one wheel and separate second means for applying a retarding torque to the second wheel, whereby each of said wheels is prevented from rolling freely on the track means to thereby control the velocity of the trolley when empty and when loaded, the diameters of the two wheels and the two means for applying torque thereto being selected such that one wheel and the torque applying means for said wheel produces a greater retarding torque than the other wheel and the means for applying torque thereto, even when the trolley is subjected to the same loading, the wheel and torque applying means which produces the greater torque being utilized when the trolley is loaded and the wheel and torque applying means which produces the lesser torque being utilized when the trolley is empty.