Water Wheel

WATER WHEEL

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.

Waterwheels have been used since ancient times to grind corn and also to raise water. The great waterwheels of Hama in Syria have raised water for over a thousand years. They serve as superb examples of a technology so elegantly simple that it becomes totally dependable. Flowing water was used to turn the wheel and water held in buckets on the rim was lifted to great heights to spill over into channels which irrigated the land further away. These great wheels where often built to huge proportions, because water was raised on their rims. Some in the Middle East were 100 ft in diameter. Water mills were common in Europe and elsewhere as a reliable source of energy and they were put to many uses. Attempts to use the power of the wheel to raise water above the level of the rim have often involved the use valves, pistons and levers, but none of these match the elegant simplicity of the wheel.