How Sarehole
Mill Works.
There are two water
wheels at the mill. The working
wheel is at the north end of the
mill and this can be operated for
school parties.
The south wheel is made of iron
and is smaller than the north wheel.
The north water wheel is made
of elm and cast iron. When
water is let out through the
bottom of the sluice gate,
it fills the buckets on the
wheel and the weight of the
water turns it around backwards.
This type of wheel is called
an overshot wheel, as the water
comes out of the sluice above
the middle of the wheel. It is
sometimes called a back shot
wheel as it turns backwards.
Water wheels were invented
2000 years ago by the Greeks
although their wheels were
set horizontally rather than
vertically as at Sarehole.
The water wheel is connected
to the mill stones by gears.
As a water wheel turns about
4 times a minute and the stones
need to turn at 120 times a
minute, two sets of gears are
used to achieve this high speed.
The wooden gears with removable
teeth are true cog wheels.
The cast iron gears are true
gears. The iron gears speed
up the motion 5 times and the
wooden gears speed up the motion
6 times, giving an increase
in speed of 30 times in all.
The gears turn the stones
from beneath by means of a
shaft which passes through
the lower stone to engage with
the runner stone above it.
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