Working model of an overshot water wheel, includes a long driven axe that can be used for workloads and an ajustable mill race so you can descover how moving it's position effects the wheel.

How do water wheels work?

Water wheels consist of large wooden or metal wheels which have paddles or buckets arranged around the outside rim. The force or the weight of the water on the paddles or buckets turns the wheel.

The axle of the wheel also turns, and this is used to drive the machine by way of belts or gears. The flowing channel of water is called a ‘mill race’. The race that brings the water from the ‘mill pond’ to the wheel is called the ‘head race’ and the channel that carries the water away is the ‘tail race’.

Overshot water wheels

In an overshot water wheel the mill race brings the water to the top of the wheel, where it strikes the paddles or buckets and turns the wheel. This is more efficient because as well as the force of the flowing water, the weight of the falling water also helps to turn the wheel. This design sometimes had buckets mounted only on one rim of the wheel, so that these filled with water, making that side of the wheel heavier.

Because it uses the potential energy of the falling water, an overshot water wheel will still work even when the flow of water is not very fast. The larger the diameter of the wheel, the greater ‘leverage’ and so the greater turning effect on the axle that drives the machine.