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53-420: A mill race , millrace or millrun , mill lade (Scotland) or mill leat (Southwest England) is the current of water that turns a water wheel , or the channel ( sluice ) conducting water to or from a water wheel. Compared with the broad waters of a mill pond , the narrow current is swift and powerful. The race leading to the water wheel on a wide stream or mill pond is called the head race (or headrace), and

106-399: A large head compared to other types of wheel which usually means significant investment in constructing the headrace. Sometimes the final approach of the water to the wheel is along a flume or penstock , which can be lengthy. A backshot wheel (also called pitchback ) is a variety of overshot wheel where the water is introduced just before the summit of the wheel. In many situations, it has

159-454: A major change of the river. Their disadvantages are their low efficiency, which means that they generate less power and can only be used where the flow rate is sufficient. A typical flat board undershot wheel uses about 20 percent of the energy in the flow of water striking the wheel as measured by English civil engineer John Smeaton in the 18th century. More modern wheels have higher efficiencies. Stream wheels gain little or no advantage from

212-441: A moderate head . Undershot and stream wheel use large flows at little or no head. There is often an associated millpond , a reservoir for storing water and hence energy until it is needed. Larger heads store more gravitational potential energy for the same amount of water so the reservoirs for overshot and backshot wheels tend to be smaller than for breast shot wheels. Overshot and pitchback water wheels are suitable where there

265-544: A poem by Antipater of Thessalonica , which praises it as a labour-saving device (IX, 418.4–6). The motif is also taken up by Lucretius (ca. 99–55 BC) who likens the rotation of the waterwheel to the motion of the stars on the firmament (V 516). The third horizontal-axled type, the breastshot waterwheel, comes into archaeological evidence by the late 2nd century AD context in central Gaul . Most excavated Roman watermills were equipped with one of these wheels which, although more complex to construct, were much more efficient than

318-449: A reversible water wheel was by Georgius Agricola and dates to 1556. As in all machinery, rotary motion is more efficient in water-raising devices than oscillating motion. In terms of power source, waterwheels can be turned by either human respectively animal force or by the water current itself. Waterwheels come in two basic designs, either equipped with a vertical or a horizontal axle. The latter type can be subdivided, depending on where

371-432: A ship odometer , the earliest of its kind. The first mention of paddle wheels as a means of propulsion comes from the 4th–5th century military treatise De Rebus Bellicis (chapter XVII), where the anonymous Roman author describes an ox-driven paddle-wheel warship. Millpond A mill pond (or millpond ) is a body of water used as a reservoir for a water-powered mill . Mill ponds were often created through

424-484: A water wheel. The mechanical engineer Ma Jun (c. 200–265) from Cao Wei once used a water wheel to power and operate a large mechanical puppet theater for the Emperor Ming of Wei ( r. 226–239). The technological breakthrough occurred in the technologically developed Hellenistic period between the 3rd and 1st century BC. A poem by Antipater of Thessalonica praised the water wheel for freeing women from

477-434: Is a small stream with a height difference of more than 2 metres (6.5 ft), often in association with a small reservoir. Breastshot and undershot wheels can be used on rivers or high volume flows with large reservoirs. A horizontal wheel with a vertical axle. Commonly called a tub wheel , Norse mill or Greek mill , the horizontal wheel is a primitive and inefficient form of the modern turbine. However, if it delivers

530-452: Is a vertically mounted water wheel with a horizontal axle that is rotated by the water from a low weir striking the wheel in the bottom quarter. Most of the energy gain is from the movement of the water and comparatively little from the head. They are similar in operation and design to stream wheels. The term undershot is sometimes used with related but different meanings: This is the oldest type of vertical water wheel. The word breastshot

583-597: Is assumed that the scientists of the Museum of Alexandria , at the time the most active Greek research center, may have been involved in its invention. An episode from the Alexandrian War in 48 BC tells of how Caesar's enemies employed geared waterwheels to pour sea water from elevated places on the position of the trapped Romans. Around 300 AD, the noria was finally introduced when the wooden compartments were replaced with inexpensive ceramic pots that were tied to

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636-420: Is rotated by the water in a water course striking paddles or blades at the bottom of the wheel. This type of water wheel is the oldest type of horizontal axis wheel. They are also known as free surface wheels because the water is not constrained by millraces or wheel pits. Stream wheels are cheaper and simpler to build and have less of an environmental impact than other types of wheels. They do not constitute

689-408: Is the overhead timber structure and a branch to the left supplies water to the wheel. The water exits from under the wheel back into the stream. A special type of overshot/backshot wheel is the reversible water wheel. This has two sets of blades or buckets running in opposite directions so that it can turn in either direction depending on which side the water is directed. Reversible wheels were used in

742-479: Is used in a variety of ways. Some authors restrict the term to wheels where the water enters at about the 10 o’clock position, others 9 o’clock, and others for a range of heights. In this article it is used for wheels where the water entry is significantly above the bottom and significantly below the top, typically the middle half. They are characterized by: Both kinetic (movement) and potential (height and weight) energy are utilised. The small clearance between

795-481: The Ancient Near East before Alexander's conquest can be deduced from its pronounced absence from the otherwise rich oriental iconography on irrigation practices. Unlike other water-lifting devices and pumps of the period though, the invention of the compartmented wheel cannot be traced to any particular Hellenistic engineer and may have been made in the late 4th century BC in a rural context away from

848-609: The Fall Line of the North American East Coast. Breastshot wheels are the most common type in the United States of America and are said to have powered the industrial revolution. A vertically mounted water wheel that is rotated by water entering buckets just past the top of the wheel is said to be overshot. The term is sometimes, erroneously, applied to backshot wheels, where the water goes down behind

901-544: The copper mines at Rio Tinto in Spain , one system involving 16 such wheels stacked above one another so as to lift water about 80 feet from the mine sump. Part of such a wheel was found at Dolaucothi , a Roman gold mine in south Wales in the 1930s when the mine was briefly re-opened. It was found about 160 feet below the surface, so must have been part of a similar sequence as that discovered at Rio Tinto. It has recently been carbon dated to about 90 AD, and since

954-414: The mining industry in order to power various means of ore conveyance. By changing the direction of the wheel, barrels or baskets of ore could be lifted up or lowered down a shaft or inclined plane. There was usually a cable drum or a chain basket on the axle of the wheel. It is essential that the wheel have braking equipment to be able to stop the wheel (known as a braking wheel). The oldest known drawing of

1007-469: The advantage that the bottom of the wheel is moving in the same direction as the water in the tailrace which makes it more efficient. It also performs better than an overshot wheel in flood conditions when the water level may submerge the bottom of the wheel. It will continue to rotate until the water in the wheel pit rises quite high on the wheel. This makes the technique particularly suitable for streams that experience significant variations in flow and reduces

1060-467: The bottom of a bucketed wheel. In the first meaning of the term, the millrace was the stream; in the sense of the word, there was no separate channel, so no race. The example of Mill Lade in Godmanchester refers to a wide channel leading to moorings where laden vessels unload, similar waterways known by the similar name of Lode exist in neighbouring districts. As technology advanced, the stream

1113-442: The bottom of a water-filled, circular shaft. The water from the mill-race which entered tangentially the pit created a swirling water column that made the fully submerged wheel act like true water turbines , the earliest known to date. Apart from its use in milling and water-raising, ancient engineers applied the paddled waterwheel for automatons and in navigation. Vitruvius (X 9.5–7) describes multi-geared paddle wheels working as

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1166-413: The capability of practical-sized waterwheels. The main difficulty of water wheels is their dependence on flowing water, which limits where they can be located. Modern hydroelectric dams can be viewed as the descendants of the water wheel, as they too take advantage of the movement of water downhill. Water wheels come in two basic designs: The latter can be subdivided according to where the water hits

1219-400: The combination of the separate Greek inventions of the toothed gear and the waterwheel into one effective mechanical system for harnessing water power. Vitruvius' waterwheel is described as being immersed with its lower end in the watercourse so that its paddles could be driven by the velocity of the running water (X, 5.2). About the same time, the overshot wheel appears for the first time in

1272-423: The construction of a mill dam or weir (and mill stream) across a waterway . In many places, the common proper name Mill Pond has remained even though the mill has long since gone. It may be fed by a man-made stream, known by several terms including leat and mill stream. The channel or stream leading from the mill pond is the mill race , which together with weirs, dams, channels and the terrain establishing

1325-738: The energy is gained from the weight of water lowered to the tailrace although a small contribution may be made by the kinetic energy of the water entering the wheel. They are suited to larger heads than the other type of wheel so they are ideally suited to hilly countries. However even the largest water wheel, the Laxey Wheel in the Isle of Man , only utilises a head of around 30 m (100 ft). The world's largest head turbines, Bieudron Hydroelectric Power Station in Switzerland , utilise about 1,869 m (6,132 ft). Overshot wheels require

1378-416: The exhausting labor of milling and grinding. The compartmented water wheel comes in two basic forms, the wheel with compartmented body ( Latin tympanum ) and the wheel with compartmented rim or a rim with separate, attached containers. The wheels could be either turned by men treading on its outside or by animals by means of a sakia gear. While the tympanum had a large discharge capacity, it could lift

1431-421: The head, a difference in water level. Stream wheels mounted on floating platforms are often referred to as hip wheels and the mill as a ship mill . They were sometimes mounted immediately downstream from bridges where the flow restriction of the bridge piers increased the speed of the current. Historically they were very inefficient but major advances were made in the eighteenth century. An undershot wheel

1484-613: The late Warring States period (476-221 BC). It says that the waterwheel was invented by Zigong, a disciple of Confucius in the 5th century BC. By at least the 1st century AD, the Chinese of the Eastern Han Dynasty were using water wheels to crush grain in mills and to power the piston- bellows in forging iron ore into cast iron . In the text known as the Xin Lun written by Huan Tan about 20 AD (during

1537-475: The metropolis of Alexandria. The earliest depiction of a compartmented wheel is from a tomb painting in Ptolemaic Egypt which dates to the 2nd century BC. It shows a pair of yoked oxen driving the wheel via a sakia gear, which is here for the first time attested, too. The Greek sakia gear system is already shown fully developed to the point that "modern Egyptian devices are virtually identical". It

1590-519: The mid- to late 18th century John Smeaton 's scientific investigation of the water wheel led to significant increases in efficiency, supplying much-needed power for the Industrial Revolution . Water wheels began being displaced by the smaller, less expensive and more efficient turbine , developed by Benoît Fourneyron , beginning with his first model in 1827. Turbines are capable of handling high heads , or elevations , that exceed

1643-408: The mill pond, delivers water to the mill wheel to convert potential and/or kinetic energy of the water to mechanical energy by rotating the mill wheel. The production of mechanical power is the purpose of this civil engineering hydraulic system. The term mill pond is often used colloquially and in literature to refer to a very flat body of water. Witnesses of the loss of RMS Titanic reported that

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1696-554: The one carrying water after it has left the wheel is commonly referred to as a tailrace . Waterwheels were used for various purposes from things such as agriculture to metallurgy in ancient civilizations spanning the Hellenistic Greek world , Rome , China and India . Waterwheels saw continued use in the post-classical age , like in medieval Europe and the Islamic Golden Age , but also elsewhere. In

1749-493: The outside of an open-framed wheel. The Romans used waterwheels extensively in mining projects, with enormous Roman-era waterwheels found in places like modern-day Spain . They were reverse overshot water-wheels designed for dewatering deep underground mines. Several such devices are described by Vitruvius , including the reverse overshot water-wheel and the Archimedean screw . Many were found during modern mining at

1802-475: The palace of the Pontian king Mithradates VI Eupator , but its exact construction cannot be gleaned from the text (XII, 3, 30 C 556). The first clear description of a geared watermill offers the late 1st century BC Roman architect Vitruvius who tells of the sakia gearing system as being applied to a watermill. Vitruvius's account is particularly valuable in that it shows how the watermill came about, namely by

1855-418: The pestle and mortar, which is so useful, and later on it was cleverly improved in such a way that the whole weight of the body could be used for treading on the tilt-hammer ( tui ), thus increasing the efficiency ten times. Afterwards the power of animals—donkeys, mules, oxen, and horses—was applied by means of machinery, and water-power too used for pounding, so that the benefit was increased a hundredfold. In

1908-413: The race leading away from the wheel is called the tail race (or tailrace). A mill race has many geographically specific names, such as leat , lade, flume, goit, penstock . These words all have more precise definitions and meanings will differ elsewhere. The original undershot waterwheel, described by Vitruvius , was a 'run of the river wheel' placed so a fast flowing stream would press against and turn

1961-415: The required power then the efficiency is of secondary importance. It is usually mounted inside a mill building below the working floor. A jet of water is directed on to the paddles of the water wheel, causing them to turn. This is a simple system usually without gearing so that the vertical axle of the water wheel becomes the drive spindle of the mill. A stream wheel is a vertically mounted water wheel that

2014-497: The rushing of the water ( chi shui ) to operate it ... Thus the people got great benefit for little labor. They found the 'water(-powered) bellows' convenient and adopted it widely. Water wheels in China found practical uses such as this, as well as extraordinary use. The Chinese inventor Zhang Heng (78–139) was the first in history to apply motive power in rotating the astronomical instrument of an armillary sphere , by use of

2067-478: The size, complexity, and hence cost of the tailrace. The direction of rotation of a backshot wheel is the same as that of a breastshot wheel but in other respects, it is very similar to the overshot wheel. See below. Some wheels are overshot at the top and backshot at the bottom thereby potentially combining the best features of both types. The photograph shows an example at Finch Foundry in Devon, UK. The head race

2120-457: The use of such wheels for submerging siege mines as a defensive measure against enemy sapping. Compartmented wheels appear to have been the means of choice for draining dry docks in Alexandria under the reign of Ptolemy IV (221−205 BC). Several Greek papyri of the 3rd to 2nd century BC mention the use of these wheels, but do not give further details. The non-existence of the device in

2173-444: The usurpation of Wang Mang ), it states that the legendary mythological king known as Fu Xi was the one responsible for the pestle and mortar, which evolved into the tilt-hammer and then trip hammer device (see trip hammer ). Although the author speaks of the mythological Fu Xi, a passage of his writing gives hint that the water wheel was in widespread use by the 1st century AD in China ( Wade-Giles spelling): Fu Hsi invented

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2226-448: The vertical-axle waterwheel. In the 2nd century AD Barbegal watermill complex a series of sixteen overshot wheels was fed by an artificial aqueduct, a proto-industrial grain factory which has been referred to as "the greatest known concentration of mechanical power in the ancient world". In Roman North Africa , several installations from around 300 AD were found where vertical-axle waterwheels fitted with angled blades were installed at

2279-416: The water hits the wheel paddles, into overshot, breastshot and undershot wheels. The two main functions of waterwheels were historically water-lifting for irrigation purposes and milling, particularly of grain. In case of horizontal-axle mills, a system of gears is required for power transmission, which vertical-axle mills do not need. The earliest waterwheel working like a lever was described by Zhuangzi in

2332-560: The water only to less than the height of its own radius and required a large torque for rotating. These constructional deficiencies were overcome by the wheel with a compartmented rim which was a less heavy design with a higher lift. The earliest literary reference to a water-driven, compartmented wheel appears in the technical treatise Pneumatica (chap. 61) of the Greek engineer Philo of Byzantium ( c.  280  – c.  220 BC ). In his Parasceuastica (91.43−44), Philo advises

2385-488: The wheel and the masonry requires that a breastshot wheel has a good trash rack ('screen' in British English) to prevent debris from jamming between the wheel and the apron and potentially causing serious damage. Breastshot wheels are less efficient than overshot and backshot wheels but they can handle high flow rates and consequently high power. They are preferred for steady, high-volume flows such as are found on

2438-423: The wheel into backshot (pitch-back ), overshot, breastshot, undershot, and stream-wheels. The term undershot can refer to any wheel where the water passes under the wheel but it usually implies that the water entry is low on the wheel. Overshot and backshot water wheels are typically used where the available height difference is more than a couple of meters. Breastshot wheels are more suited to large flows with

2491-457: The wheel. A typical overshot wheel has the water channeled to the wheel at the top and slightly beyond the axle. The water collects in the buckets on that side of the wheel, making it heavier than the other "empty" side. The weight turns the wheel, and the water flows out into the tail-water when the wheel rotates enough to invert the buckets. The overshot design is very efficient, it can achieve 90%, and does not require rapid flow. Nearly all of

2544-449: The wood from which it was made is much older than the deep mine, it is likely that the deep workings were in operation perhaps 30–50 years after. It is clear from these examples of drainage wheels found in sealed underground galleries in widely separated locations that building water wheels was well within their capabilities, and such verticals water wheels commonly used for industrial purposes. Taking indirect evidence into account from

2597-510: The work of the Greek technician Apollonius of Perge , the British historian of technology M.J.T. Lewis dates the appearance of the vertical-axle watermill to the early 3rd century BC, and the horizontal-axle watermill to around 240 BC, with Byzantium and Alexandria as the assigned places of invention. A watermill is reported by the Greek geographer Strabon ( c.  64 BC  – c.  AD 24 ) to have existed sometime before 71 BC in

2650-589: The year 31 AD, the engineer and Prefect of Nanyang , Du Shi (d. 38), applied a complex use of the water wheel and machinery to power the bellows of the blast furnace to create cast iron . Du Shi is mentioned briefly in the Book of Later Han ( Hou Han Shu ) as follows (in Wade-Giles spelling): In the seventh year of the Chien-Wu reign period (31 AD) Tu Shih was posted to be Prefect of Nanyang. He

2703-425: Was a generous man and his policies were peaceful; he destroyed evil-doers and established the dignity (of his office). Good at planning, he loved the common people and wished to save their labor. He invented a water-power reciprocator ( shui phai ) for the casting of (iron) agricultural implements. Those who smelted and cast already had the push-bellows to blow up their charcoal fires, and now they were instructed to use

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2756-404: Was dammed by a weir . This increased the head of water. Behind the weir was the millpond , or lodge. The water was channelled to the waterwheel by a sluice or millrace- this was the head race . From the waterwheel, the water was channelled back to the course of the stream by a sluice known as the tail race . When the tail race from one mill led to another mill where it acted as the head race this

2809-401: Was known as the mid race . The level of water in the millrace could be controlled by a series of sluice gates. Water wheel Some water wheels are fed by water from a mill pond, which is formed when a flowing stream is dammed . A channel for the water flowing to or from a water wheel is called a mill race . The race bringing water from the mill pond to the water wheel is a headrace ;

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