Abstract: A roller drive assembly comprises a frame on which is mounted a rotatable drive roller which has a rotatable outer shell and which can pivot about an axis eccentric to the axis of rotation of the outer shell between a retracted position and a drive position. A drive motor mounted on the frame outside the drive roller is provided to power the drive roller. Located in the drive roller is a planetary gear system which comprises a sun gear, a ring gear, and a planet carrier bearing planet gears, the ring gear being rotational about the planet carrier and defining at least a part of said outer shell. The planet carrier also defines axle stubs offset from the axis of rotation of the outer shell which are located in bearings mounted in the frame to enable the drive roller to pivot with respect to the frame. A gear train is operationally connected to the drive motor to drive the sun gear and a pinion is located at one end of an output shaft of the gear train.