Geograph - photograph every grid square

This is the mechanism for operating the patent sails - see TL9773 : Stanton post mill - the patent sails. The striking rod is seen entering stage right and carries the spider operating the shutters on the sail. The rack is moved by (or moves) the pinion that is connected to a weight via its shaft and a wheel. The weight holds the shutters closed against the wind until the wind is strong enough to lift the weight and the shutters open to spill the wind. This gear is at the top rear of the buck and the striking rod passes through the windshaft.