| 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 1:4½. Overall,
the gearing makes the stones rotate 13½ 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.
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