Water Wheel Undershot

An undershot wheel is a vertically mounted water wheel. Its rotation is caused by water striking paddles or blades at the bottom of the wheel. The name undershot comes from this striking at the bottom of the wheel. This type of water wheel, sometimes called stream wheel, is the oldest one. The first description is from Vitruvius, an engineer of the Augustan Age at the beginning of our Era.

Compared with the other types of water wheels this type is less efficient. It should be built only there, where the flow rate is sufficient to provide rotation of the wheel. The faster the water flows the faster the wheel turns. Therefore the system of the wheel is placed over a fast-flowing river. However, an undershot wheel has some advantages. It is easy to build, simple, it could be cheaper than the other types. It also has less of an environmental impact. Historically these water wheels were used to turn-milling stones and other mechanical tasks.