Coloured Drawing of Hooper's windmill for grinding corn

Coloured Drawing of Hooper's windmill for grinding corn, 1802

This sectional drawing, dated 1802, shows a four-armed windmill for grinding corn, driving two pairs of millstones, a dressing machine, and a sack hoist. Beneath the mill is a nearly horizontal water-wheel, connected by bevel gear with the main shaft, and probably provided as an alternative source of power. The cap of the mill is carried on friction wheels, and is automatically slewed by a small wind-wheel whose plane is at right angles to that of the large arms. The regulating arrangement of this mill was patented in 1789 by Stephen Hooper, of Margate, and forms an early instance of the application of the centrifugal governor to regulate the mill's speed. Each sail is made up of small elements wound on separate rollers, and when the velocity of the windmill increases, centrifugal action causes these elements to be rolled up against the pull of a weighted spiral drum or fusee within the mill. Hooper also described a conical pendulum governor which was to feed more corn into the stones when the speed increased.