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How the Lurgashall Mill Works
The waterwheel (2) drives the horizontal wooden watershaft (3) on which is mounted the pit wheel (4). This is a cast-iron bevel gear that meshes with a smaller cast-iron gear, called the wallower (5), mounted on the vertical wooden mainshaft (6). The gearing ratio between the watershaft and the mainshaft is about 1:3.

Above the wallower is mounted a larger wheel, the great spur wheel (7), which is made entirely of wood. This meshes with the cast-iron stone nuts (8) (small pinions) that drive the grindstones through vertical shafts (spindles (9)), the gearing ratio being 1:4. Overall, the gearing makes the stones rotate 13 times for each rotation of the waterwheel, the average speed of the stones being 80 r.p.m..

The spindle rotates the upper stone, the runner (11), above the fixed bedstone (10). Grain is fed from the hopper into the shoe (15), which is vibrated by the damsel (13), shaking grain into the centre of the runner stone. The grinding action moves the grain outwards to the edge of the stones, and the finished product falls into the meal bins on the ground floor.

At the top of the mainshaft is a further wheel, the crown wheel (17), which runs two ancillary drives (18). One of these powers a sack hoist (21) in the top floor of the mill, a slack belt operating as a primitive clutch. The other drives a flour (19) dresser that separates the whole meal into bran and unbleached white flour.

1 Penstock 6 Mainshaft 11 Runner stone 16 Grain hopper 21 Sack flaps
2 Waterwheel 7 Great spur wheel 12 Tun 17 Crown wheel 22 Meal bin
3 Watershaft 8 Stone nut 13 Damsel 18 Ancillary drives  
4 Pit wheel 9 Spindle 14 Horse 19 Flour dresser  
5 Wallower 10 Bedstone 15 Shoe 20 Hoist