Page 300 - The Lost Ways

All three styles of water wheel require a channel to direct the water. With the horizontal
and overshot vertical waterwheels, the channel directs the water to the vanes of the
wheel. For the undershot water wheel (middle diagram), the paddles of the wheel sit in
the channel.

This can cause problems for the undershot wheel because it is affected by the level of the
water. During the dry season, the water level drops, so less of the paddle sits in the water;
if it is dry enough, the paddles might be totally exposed and out of the water. As this type
of waterwheel works through the force of the water pushing against the blades of the
wheel, the less of the blade that is in the water, the less power that is produced.

This shows the advantage of the overshot water wheel, which we want to focus on. This
style of wheel is not affected by water levels as long as there is water still flowing through
the channel and filling the buckets on the wheel. Clearly, this provides a great
technological advantage in that the water wheel and the mill it powers can be used year-
round. For this reason, the majority of the water wheels we find still in existence from the
colonial and pioneering parts of U.S. history are overshot vertical water wheels.

How the Overshot Wheel Works

I mentioned that the undershot wheel works by the force of the water pushing against
the wheel’s blades. The same can be said for the horizontal water wheel, but the overshot

water wheel doesn’t depend on the force of the water but rather its weight.

This type of water wheel doesn’t have paddles or vanes but instead uses buckets. While
it may look similar, it is quite different. The buckets are filled with water as they pass
under the water sluice. That makes the wheel off-balance, causing it to turn and offer a
new bucket to be filled. As the wheel continues to turn, subsequent buckets are filled,
creating a great imbalance between the two sides of the wheel. This imbalance is

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