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Water wheel

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A water wheel is a machine designed to convert kinetic energy into useful power. Kinetic energy is the energy of motion. This machine captures the energy from flowing or falling water.

Waterwheel that used to crush grain into flour
Waterwheel that used to crush grain into flour

Most wheels are large structures made of wood or metal. They feature many blades or buckets attached to an outer rim. This rim acts as a drive mechanism to create rotation. For centuries, these wheels powered essential industries. They were used in gristmills to grind flour for food. They also helped in papermaking by grinding wood into pulp. Other industries used them to hammer wrought iron or crush ore.

Agricola1
Agricola1

The movement of the wheel depends on how water is delivered. Many systems use a mill pond to store water. This pond acts as a reservoir to hold energy for later use. A channel called a headrace carries water from the pond to the wheel. After the water passes the wheel, it flows into a tailrace.

Undershot waterwheel simple
Undershot waterwheel simple

The height difference between the water source and the wheel is called the head. A larger head means more gravitational potential energy is available. This energy can be used to turn the wheel more effectively. The design of the wheel must match the available water flow and head.

There are two primary designs for water wheels. The first is a horizontal wheel with a vertical axle. These are often called tub wheels, Norse mills, or Greek mills.

Vertical waterwheel simple
Vertical waterwheel simple

In this design, a jet of water strikes paddles on the axle. This simple system often lacks gearing. The vertical axle becomes the drive spindle for the mill. The second design is a vertical wheel with a horizontal axle. This is a much more common design for industrial use. These wheels can be subdivided into several specific types based on where the water hits them.

Vertical wheels with horizontal axles vary by their water entry point. An undershot wheel is hit by water at the bottom quarter.

Stream waterwheel simple
Stream waterwheel simple

These wheels rely mostly on the kinetic energy of the moving water. A stream wheel is a similar, older type of vertical wheel. It is also known as a free surface wheel because the water is not constrained by millraces. A breastshot wheel receives water near its center, usually between the one-quarter and three-quarter height marks.

Breastshot waterwheel simple
Breastshot waterwheel simple

These wheels use both kinetic and potential energy. They are very common in the United States and helped power the Industrial Revolution. They are ideal for steady, high-volume flows.

Overshot and backshot wheels are the most efficient vertical designs. An overshot wheel receives water in buckets near the top.

Overshot waterwheel simple
Overshot waterwheel simple

The weight of the water in the buckets turns the wheel as it rotates. This design can reach an efficiency of 80% to 90%. It is best suited for hilly areas with a large head. A backshot wheel, or pitchback wheel, is similar to the overshot design. However, the water hits the wheel just before the summit. This causes the wheel to turn back toward the headrace. This design can perform better during floods when water levels rise.

Backshot waterwheel simple
Backshot waterwheel simple

Humanity has used water wheels since ancient times. They were used in the Near East, China, and the Roman Empire. They also played roles in the Islamic Golden Age and medieval Europe. In the mid-to-late 18th century, John Smeaton conducted scientific investigations into these machines. His work significantly increased the efficiency of water wheels. This was vital for providing power during the Industrial Revolution. However, water wheels have limitations. They depend entirely on flowing water, which restricts where they can be placed. In 1827, Benoît Fourneyron developed the turbine.

HeadMeasurement
HeadMeasurement

Turbines are smaller and more efficient than wheels. They can also handle much higher heads than practical-sized water wheels.

Even though water wheels are less common today, their legacy continues. Modern hydroelectric dams are the direct descendants of the water wheel. Both systems take advantage of water moving downhill to generate power. While a traditional overshot wheel might use a head of only a few meters, modern turbines are much more powerful. For example, the Bieudron Hydroelectric Power Station in Switzerland uses a head of about 300 meters.

Laxey Wheel 08676u
Laxey Wheel 08676u

The transition from simple wooden wheels to massive hydroelectric systems shows the evolution of energy capture. We have moved from simple mechanical rotation to sophisticated electrical generation. Yet, the fundamental principle remains the same: using the movement of water to do work.

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🖼️ Images & Media (25)
Brucker Wasserrad 01.webm
File:Agricola1.jpg
Agricola1.jpg
Otley waterwheel, Manchester Museum of...
File:Waterwheel that used to crush grain into flour.jpg
Waterwheel that used to crush grain into flour.jpg
File:Vertical waterwheel simple.svg
Vertical waterwheel simple.svg
File:Stream waterwheel simple.svg
Stream waterwheel simple.svg
File:Undershot waterwheel simple.svg
Undershot waterwheel simple.svg
File:Breastshot waterwheel simple.svg
Breastshot waterwheel simple.svg
File:Overshot waterwheel simple.svg
Overshot waterwheel simple.svg
File:Backshot waterwheel simple.svg
Backshot waterwheel simple.svg
File:Finch Foundary Water Wheel, Devon, UK - Diliff.jpg
Finch Foundary Water Wheel, Devon, UK - Diliff.jpg
File:AndersonMill.jpg
AndersonMill.jpg

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