Waterwheels

A waterwheel is a machine that converts the energy of flowing or falling water into rotational mechanical power. It typically consists of a wheel with paddles or buckets around its rim, mounted on a horizontal or vertical axle, and driven by water delivered through a headrace or chute to the wheel.

Waterwheels operate in several basic configurations. In the undershot type, water strikes the wheel at the bottom, using the kinetic energy of the flowing water. In the overshot type, water is fed above the wheel into buckets, using gravitational potential energy to create torque. Breastshot wheels are fed roughly at the wheel’s midpoint, combining elements of both. The choice of form affects efficiency, suitability for flow conditions, and the load it can drive.

Historically, waterwheels are among the oldest power-producing devices. They appear in ancient China and the Near East and became widespread in medieval Europe for grinding grain, sawing timber, and textile processing. They remained a dominant source of mechanical power until the development of steam engines and, later, electric motors, though they continued in some regions for specialized tasks and in heritage contexts.

Construction and components commonly include the wheel itself, an axle with bearings, a water inlet and tailrace, and gearing or belts to transmit motion to millstones or other machinery. Early wheels were wood with iron fittings; later examples used metal construction and reinforced components.

Today, small waterwheels are still used in traditional mills, heritage sites, and some micro-hydro installations where simplicity and low maintenance are advantageous, though modern turbines outpace them in efficiency and controllability.