water wheel

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Waterwheel

A waterwheel, also called a water wheel or noria, is a device that uses falling or flowing water to produce power (what is called hydropower). It consists of a large vertical wheel, usually made of wood, attached to a horizontal axle. The wheel has a number of blades or buckets attached on the outside of the wheel used to catch the water. The two general types of waterwheels are the undershot and the overshot.

The waterwheel is considered the first rotor mechanism in which an outside force creates power to spin a shaft. The ancient Greeks are said to have first developed the waterwheel, using it to raise water from rivers. Polls or pots were attached around the circumference of a large wheel; then oxen would walk in a circle round a vertical shaft connected through a simple gear to the horizontal shaft of the waterwheel. When possible, the current of a fast-flowing river would do the work of the oxen. By Roman times, ancient engineers realized that the spinning shaft could be used as a power source to turn millstones. However, few were built for this purpose due to the abundance of slaves to grind grain into flour.

After the fall of the Roman Empire, waterwheels spread throughout Medieval Europe largely through the efforts of monks who introduced the technology to landowners, many of whom had lost workers to disease and war. In the eighteenth century, waterwheels were developed in England by such inventors as engineer James Brindley (17161772) and civil engineer John Smeaton (17241792).

The first factoriestextile millswere powered by water. Other early uses of waterwheels included sawmills for sawing lumber and gristmills for grinding grain. Many large cities owe their existence to power drawn from nearby rivers, but this power source was not very dependable due to floods and droughts that changed the amount of water flowing in the river.

Several types of waterwheels evolved over the centuries. The two most used were the overshot wheel, which involved water falling on the paddles from above, and the undershot wheel, which was placed directly in the water and worked especially well in swift streams. A more unusual and less frequently used type was the reaction wheel in which water was dropped into a hollow tube from a great height. The tube had hollow spouts attached to it, and the water would spray out the spouts, causing the tube to rotate much like todays lawn sprinklers. The tidal wheel required an enclosed pond with a gate. As the tide rose, water flowed into the pond until the gate was closed, effectively trapping the water. Later, the gate was opened, allowing water to flow out and turn a wheel for power.

By the late eighteenth century, more efficient and powerful steam engines began to replace waterwheels as Europes primary source of power. However, the principle of the waterwheel lives on in todays water turbines such as those found in hydro-electric dams, which use the movement of downward flowing water.

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Waterwheel

The waterwheel is considered the first rotor mechanism in which an outside force creates power to spin a shaft. The Greeks are said to have first developed the waterwheel, using it to raise water from rivers . Polls or pots were attached around the circumference of a large wheel; then oxen would walk in a circle round a vertical shaft connected through a simple gear to the horizontal shaft of the waterwheel. When possible, the current of a fast-flowing river would do the work of the oxen. By Roman times, ancient engineers realized that the spinning shaft could be used as a power source to turn millstones. However, few were built for this purpose due to the abundance of slaves to grind grain into flour.

After the fall of the Roman Empire, waterwheels spread throughout Medieval Europe largely through the efforts of monks who introduced the technology to
landowners, many of whom had lost workers to disease and war. The first factories—textile mills—were powered by water. Other early uses of waterwheels included sawmills for sawing lumber and gristmills for grinding grain. Many large cities owe their existence to power drawn from nearby rivers, but this power source was not very dependable due to floods and droughts that changed the amount of water flowing in the river.

Several types of waterwheels evolved over the centuries. The two most used were the overshot wheel, which involved water falling on the paddles from above, and the undershot wheel, which was placed directly in the water and worked especially well in swift streams. A more unusual and less frequently used type was the reaction wheel in which water was dropped into a hollow tube from a great height. The tube had hollow spouts attached to it, and the water would spray out the spouts, causing the tube to rotate much like today's lawn sprinklers. The tidal wheel required an enclosed pond with a gate. As the tide rose, water flowed into the pond until the gate was closed, effectively trapping the water. Later, the gate was opened, allowing water to flow out and turn a wheel for power.

By the late eighteenth century, more efficient and powerful steam engines began to replace waterwheels as Europe's primary source of power. However, the principle of the waterwheel lives on in today's water turbines.

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water wheel, device for utilizing the power of flowing or falling water. The Norse wheel is the oldest type known. Despite its name it probably originated in the Middle East, where the swift stream required by this type of wheel is common. The Norse wheel has a vertical shaft directly connected at the top to a millstone; the lower end of the shaft, with vanes or paddles attached, dips into the flowing stream. In the 1st cent. BC a horizontal shaft came into use; the wheel attached to it had radial vanes around its edge. Among the early forms of this wheel are the overshot wheel, used where water falls from a height, striking the vanes from above; the breast wheel, employed where the height of the water is less than the height of the wheel so that the water strikes the wheel about midway; and the undershot wheel, usable where the water flows more or less on a level but with a swift current and strikes the vanes on the under part of the wheel. One of the first uses of the steam engine was to drive a pump that raised water into a millpond whose spillway drove a water wheel. Today the water wheel has been largely replaced by the turbine. See hydraulic machine.

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wa·ter·wheel / ˈwôtərˌ(h)wēl; ˈwä-/ • n. a large wheel driven by flowing water, used to work machinery or to raise water to a higher level. water wheel.eps"/>

waterwheel

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water-wheel. Wheel driven by water, either falling from above, or passing underneath.