The Hour Wheel Reference no 250 



The hour hand is
attached to the Hour Wheel (250) arbor. The Minute Wheel pinion
drives the wheel called the Hour Wheel (250), which in turn decelerates
the turning rate of the center wheel to the Hour Wheel by a factor
of 1:12, giving the Hour Wheel the turning rate of one
revolution in 12
hours.




In the figure above it can be seen how the Minute Wheel pinion drives the Hour Wheel. The Hour Wheel is centered by the Cannon Pinion but not fixed to it, see center of the figure. In this way the Cannon Pinion and the hour Wheel can rotate around the same center axis but at different speeds. 