Abstract: A cargo drive unit which, as part of an array of several such units, it disposed in the hold of a vehicle to permit cargo to be moved within the hold. The drive unit derives power from an electric motor to first erect a drive a roller into contact with a load and then to move the load. A hysteresis coupling is disposed between the motor and the roller and functions to limit the force of the roller against the load to be driven by adjusting the excitation current thereto. The hysteresis coupling allows the roller to retract when the current to the coupling is removed and limits shock loading to drive gearing and the motor when excessive loads are applied to the roller.