There is something mesmerizing about a waterwheel at work. They are fascinating pieces of machinery that date back to at least the 1st century B.C. These wheels were probably the first method of creating mechanical energy that replaced humans and animals. Waterwheels were used for crop irrigation, grinding grains, and supplying drinking water to villages and later to drive various kinds of mills. (A waterwheel and mill combination is called a watermill.)  Now they are sometimes used to generate electricity.

Waterwheels today are a kind of preservation of the past. The love of these old mills has sparked many mill renovation and reconstruction projects as well as the creation of organizations dedicated to promoting interest in the mills. These organizations, such as the Society for the Preservation of Old Mills, provide matching grants to mill preservation projects, publish periodicals, sponsor meetings, and provide libraries for study of their history, uses, types, and construction. (Check out http://www.spoom.org/)

A water wheel is a relatively simple machine. It consists of a large wooden or metal wheel, with a number of blades or buckets arranged on the outside rim forming the driving surface. For most types of water wheels, a channel is created for the water to follow while flowing to or from the wheel. In the operation of a waterwheel, the force of the water's movement moves the blades of the wheel which turns an axle that drives the mill's other machinery. In the United States, most waterwheels are one of three kinds: undershot, overshot and breastshot.

The undershot is a large vertical waterwheel placed in a stream and turned by the river's motion. The undershot wheel is tremendously inefficient because the wheel itself, entering the water behind the main thrust of the flow driving the wheel, followed by the lift of the wheel out of the water ahead of the main thrust, actually impedes its own operation. The overshot wheel solves this problem by directing the flow of the water to the top of the wheel.

In the overshot or pitchback waterwheel, water flows down from a channel above and the gravity of the water turns the wheel. The water fills buckets built into the wheel. As the buckets fill, the weight of the water starts to turn the wheel. The water spills out of the bucket on the down side into a spillway leading back to river. Since the wheel itself is set above the spillway, the water never slows down the speed of the wheel. Overshot wheels require the construction of a dam (mill pond) on the river above the mill.

With the breastshot waterwheel, the water flows onto the wheel from about half way up and flows out with the rotation of the wheel. An apron, or breast, fitted tightly to these wheels helps prevent water from leaving the buckets too soon, increasing the effect of gravity upon the wheel. Since water flows from the upstream side of the wheel near the middle (not above like the overshot), much greater wheel diameters can be used which provide more power.

Today, water wheels are becoming popular in landscaping – in either natural or manmade water settings. The sound and the motion of the wheel churning in a stream or garden pond can often relax even the most jangled nerves. And they are also very aesthetically appealing – casting an ambiance of times long ago.

Middle Tennessee, with its plentiful supply of creeks and streams, is a great place to find that choice spot to set a water wheel in motion.