First the power is generated by the turbine. This turbine
sits within a turbine chamber which is approximately 18 feet deep. This
chamber is fed with water through a gate in the dam.
The smaller shaft you see connected to the turbine is the
control rod. The angle of the vanes in the turbine is adjusted by this
control rod. As these vanes open they allow water to enter the turbine,
and this is what controls the power output of the turbine.
This diagram shows the lower stationary millstones and the main line
shaft located directly underneath those stones. Power is transmitted
to this shaft by the belt to the pulley shown in the lower right hand
corner. As the shaft rotates power is transmitted to the stone shafts
through gears. The upper stone sits on top of the stone shaft that
travels up through the bottom stone.
The pulley shown on the left of the shaft transmits power by belt up to
the top floor where it turns the bucket belts.
The lower millstone
This picture shows the three millstones set up and ready for grinding.
So how do the millstones actually
First the surface of the millstones have a rough texture, but
the texture plays only one small part of how they make cornmeal.
The upper millstone has the same pattern of "grooves"
or furrows as the lower stone (or bedstone) shown in the picture
to the left. However, the upper millstone pattern is the reverse
of the lower millstone.
The furrows are not just grooves cut straight into the stone,
they are slightly angled on one side. This angle along with the
reverse pattern on the upper stone creates a scissor like cutting
action as the upper stone rotates.
The furrows are cut deeper in the center of the stone and are
more shallow at the outer edge. As corn enters the millstones
it is caught in the deep furrows at the center. As the kernels
of corn begin the grinding process they move towards the outer
edge of the stone, each time encountering more and more furrows.
Along the center of the stone there are only 13 furrows, compared
to 42 furrows at the outer perimeter. When the corn reaches the
outer perimeter of the stone it falls out and is trapped between
the rotating upper stone and the inside edge of the millstone
cover (also known as a vat). The meal continues to rotate until
it reaches the trough and exits the vat.