WATER WHEEL. A wheel for utilizing the weight of falling water to perform mechanical work. (See WATER POWER.) The term water wheel is properly applied to all hydraulic motors; that rotate, but it has come to be re stricted to wheels which act mainly by the weight of water that they reccirc un their• cir cumferential parts only. which turn on horizon tal shafts, and which move with a low velocity and a velocity that has no relation to the head of water under which the wheel works. In all these respects water wheels as the term is used here differ from turbines (q.v.). Water wheels are designated as overshot or breast wheels ac cording as they receive the water at or near the top. below the centre, or below the top and above the centre.
The orcrshol wheel has a series of buckets arranged on its 1.ircumfervnee so that. as the wheel rotates forward, in the direction of the hands of a clock, the buckets on the descending side have their top upward. The water is led to the wheel by a trough o• flume which dis charges at the top of the wheel just forward of a vertical through its axis. This water fills the buckets and its weight causes the wheel to ro tate forward. Each bucket is filled as it comes under the discharge from the flume, and each is emptied as the rotation brings it near the bot tom. The object of this is to have the weight of each bucketful of water act throughout the en tire vertical distance of the fall. The earlier forms of overshot water «•heels were built of wood and were enormously massive and clumsy looking structures. At a later period iron was substituted for wood, with material gain in lightness and appearance. Overshot wheels were often of enormous size, one of the largest being • feet in diameter, located at Saxey, on the Isle of Man.
An vadcrshot wheel has instead of buckets a series of vanes or paddles on its circumference, and the water, so to speak, flows under the wheel and pushes the paddles forward so as to cause rotation in a direction opposite to the move ment of the hands of a watch- In the simplest form of undershot wheel the paddles are radial and the wheel is set so that they dip just their full depth into the current of a flowing stream. In the more approved form of undershot wheel the water passes under the wheel in a rectangu lar sluice concentric with the wheel. in which the paddles revolve with as little clearance as is con sistent with movement. The breast wheel, like industry, which is constantly calling for in creased rates of speed.
Recently a form of water wheel known as the impulse wheel has come into extensive use. It consists of a series of cup-shaped vanes attached to the periphery of a wheel and acted on by a jet of water. The water is delivered through a pipe having a nozzle to form a jet which im pinges against one bucket after another, as the wheel revolves. A notable feature of this wheel the shape of the buckets, which is such that they clear themselves of water without ob structing in any way the propelling jet. Seme times two or three nozzles are employed instead of one, the jet from each striking the wheel at a different point.
Notable among the impulse wheels are those of the Pelton type, some of which have been con the overshot wheel. has a series of buckets on its eireumferenee, hut they are so arranged that the wheel revolves backward, or in a direction oppo site to the movement of the hands of a watch.
In the overshot wheel, still using the dial of a watch as an illustration. the water enters the Locket at about the point where number I on the dial is located and leaves it about the point where number V is located; in the breast wheel the water enter: the bucket at about X and leaves it at about VII; in the undershot wheel the water hits the paddle at about VIII and leaves it at about VI.
The numerous disadvantages of the water wheels which have been described have caused them to be almost entirely superseded by the turbine. (See Tuertfxr.) They occupy much more room than turbines of the same power, and must be inclosed in buildings to prevent obstruc tion by ice in winter. Ilnek-water affects them injuriously, not only by diminishing the head, lint by drowning them and causing them to ex pend their power in 'wallowing,' a source of loss from which turbines are wholly Tree. The necessarily low velocity with which they move nev t umbrons and expensive gearing to raise the _l 'eel to the requirements of structed as large as IS feet 13 inches in diameter and have been employed to work air compressors in mines. A wheel of this size weighs 10.000 pounds. and runs at 110 revolutions per minute at a 730-foot head of water and develops over 300 horse power. The wheel is made of iron plates riveted together, which are held concen tric with the shaft by radial spokes, and a truss consisting of four pairs of two-inch rods. There is a variable nozzle operated by an automatic hydraulic regulator through which the water is applied to the wheel and causes it to run at uniform speed with loads.
Binuat_tn otev. Besides varying books mentioned under WATER POWER and TURBINE, the reader will find much valuable data relating to water wheels in Weisleteh. Hydraulics and Hydraulic Motors (Eng. trans. by Du Bois, New York, 1877), and Bjorling, Water or Hydraulic llotors (London. IS94). The best description of wheels of the impulse type will be found in various articles in the engineering papers during the last ten years. See WATER POWER: TURBINE.
Any of various birds quip]; at diving, as a grebe, bnfflebead duel:, or dipper.
The various structures and devices used to provide water for domestic and industrial uses, fire protection. and other public services, The term is here restrieted to plants for the supply of monicipolitie:. Works limited to the needs of a single establishment generally differ little in principle from municipal works, lent are smaller and simpler. The main points to he discussed in this artiele are the quality and quantity of water to be provided; the source awl mode of supply, the latter in volving a choke between gravity and pumping; the size and character of pumping works, reser \ Mrs, tanks, and standpipes; the distribution and various details of public policy.