The wooden toothed gear is driven by the horizontal wheel on the vertical shaft. The belt transports the energy upwards to the winch with rope. You see that the vertical shaft can be disconnected from the lower shaft by removing the 4 large pins. This was done when the miller used the old engine below in case there was no wind. Disconnecting made that the upper parts did not have to move because the engine had not to much pwer for doing so.
5 previous images show more of this special sack hoist system