The gears 40, 42, 46, 48, pilot shafts 44, 50, 58, 62, extension 53, plate 56 and ball detents 54 are preferably constructed of a plastic material such as nylon or the like thereby providing a relatively inexpensive but yet dependable release clutch to prevent the plastic gears from stripping when the motor is activated and the scrubber unit 24 cannot rotate.