The word breastshot is used in a variety of ways. Both kinetic movement and potential height and weight energy are utilised. The small clearance between 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. Breastshot wheels are the most common type in the United States of America [ citation needed ] and are said to have powered the industrial revolution.
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 the advantage that the bottom of the wheel is moving in the same direction as the water in the tail race 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 the size, complexity and hence cost of the tail race.
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. 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 the wheel. A typical overshot wheel has the water channelled 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. Nearly all of the energy is gained from the weight of water lowered to the tail race 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 country. Overshot wheels require a large head compared to other types of wheel which usually means significant investment in constructing the head race.
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Sometimes the final approach of the water to the wheel is along a flume or penstock , which can be lengthy. Some wheels are overshot at the top and backshot at the bottom thereby potentially combining the best features of both types. The head race 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. 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 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 German: Kettenkorb 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 a reversible water wheel was by Georgius Agricola and dates to Two early improvements were suspension wheels and rim gearing.
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Suspension wheels are constructed in the same manner as a bicycle wheel, the rim being supported under tension from the hub- this led to larger lighter wheels than the former design where the heavy spokes were under compression. Rim-gearing entailed adding a notched wheel to the rim or shroud of the wheel.
A stub gear engaged the rim-gear and took the power into the mill using an independent line shaft. This removed the rotative stress from the axle which could thus be lighter, and also allowed more flexibility in the location of the power train. The shaft rotation was geared up from that of the wheel which led to less power loss. An example of this design pioneered by Thomas Hewes and refined by William Fairburn can be seen at the restored wheel at the Portland Basin Canal Warehouse. The two main functions of water wheels were historically water-lifting for irrigation purposes and as a power source.
When used for water-lifting power can be supplied by either human or animal force or by the water current itself. It is not clear from the available historic texts and archaeology whether the watermill originates in Egypt, India, Greece, or regions in-between; usage within just a few decades of each other's cultures in the 4th to 3rd centuries B. Paddle-driven water-lifting wheels had appeared in ancient Egypt by the 4th century BCE.
The invention of the compartmentalized water wheel occurred in ancient Egypt around the 4th century BCE, in a rural context, away from the metropolis of Hellenistic Alexandria , and then spread to other parts of North Africa. According to John Peter Oleson , both the compartmented wheel and the hydraulic Noria appeared in Egypt by the 4th century BCE, with the Sakia being invented there a century later.
This is supported by archeological finds at Faiyum , where the oldest archeological evidence of a water-wheel has been found, in the form of a Sakia dating back to the 3rd century BCE. A papyrus dating to the 2nd century BCE also found in Faiyum mentions a water wheel used for irrigation, a 2nd-century BC fresco found at Alexandria depicts a compartmented Sakia, and the writings of Callixenus of Rhodes mention the use of a Sakia in Ptolemaic Egypt during the reign of Ptolemy IV in the late 3rd century BC.
Mediterranean engineers of the Hellenistic and Roman periods used the water wheel for both irrigation and as a power source. The Romans used water wheels extensively in mining projects. Several such devices were described by Vitruvius. Part of a similar wheel dated to about 90 CE, was found in the s, at Dolaucothi , a Roman gold mine in south Wales.
Taking indirect evidence into account from the work of the Greek technician Apollonius of Perge , the British historian of technology M. Lewis dates the appearance of the vertical-axle watermill to the early 3rd century BC, and the horizontal-axle watermill to around BC, with Byzantium and Alexandria as the assigned places of invention. The first clear description of a geared watermill is from the 1st-century BC Roman architect Vitruvius , who tells of the sakia gearing system as being applied to a watermill.
About the same time, the overshot wheel appears for the first time in a poem by Antipater of Thessalonica , which praises it as a labour-saving device IX, In Roman North Africa , several installations from around AD were found where vertical-axle water wheels fitted with angled blades were installed at the bottom of a water-filled, circular shaft. The water from the mill-race which entered the pit tangentially 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 water wheel for automatons and in navigation. 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. Chinese water wheels almost certainly have a separate origin, as early ones there were invariably horizontal water wheels.
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 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 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. He 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 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— was the first in history to apply motive power in rotating the astronomical instrument of an armillary sphere , by use of a water wheel.
The early history of the watermill in India is obscure. Ancient Indian texts dating back to the 4th century BC refer to the term cakkavattaka turning wheel , which commentaries explain as arahatta-ghati-yanta machine with wheel-pots attached. On this basis, Joseph Needham suggested that the machine was a noria.
Reynolds, however, argues that the "term used in Indian texts is ambiguous and does not clearly indicate a water-powered device".
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According to Greek historical tradition, India received water-mills from the Roman Empire in the early 4th century AD when a certain Metrodoros introduced "water-mills and baths, unknown among them [the Brahmans] till then". This kind of water raising device was used in ancient India , predating, according to Pacey, its use in the later Roman Empire or China, [42] even though the first literary, archaeological and pictorial evidence of the water wheel appeared in the Hellenistic world.
During medieval times, the diffusion of Indian and Persian irrigation technologies gave rise to an advanced irrigation system which brought about economic growth and also helped in the growth of material culture. Arab engineers took over the water technology of the hydraulic societies of the ancient Near East; they adopted the Greek water wheel as early as the 7th century, excavation of a canal in the Basra region discovered remains of a water wheel dating from this period.
Hama in Syria still preserves some of its large wheels , on the river Orontes , although they are no longer in use. Another wheel that is still in operation is found at Murcia in Spain , La Nora, and although the original wheel has been replaced by a steel one, the Moorish system during al-Andalus is otherwise virtually unchanged. The industrial uses of watermills in the Islamic world date back to the 7th century, while horizontal-wheeled and vertical-wheeled water mills were both in widespread use by the 9th century.
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A variety of industrial watermills were used in the Islamic world, including gristmills , hullers , sawmills , shipmills, stamp mills , steel mills , sugar mills , and tide mills. By the 11th century, every province throughout the Islamic world had these industrial watermills in operation, from al-Andalus and North Africa to the Middle East and Central Asia. Industrial water mills were also employed in large factory complexes built in al-Andalus between the 11th and 13th centuries.
The engineers of the Islamic world developed several solutions to achieve the maximum output from a water wheel. One solution was to mount them to piers of bridges to take advantage of the increased flow. Another solution was the shipmill, a type of water mill powered by water wheels mounted on the sides of ships moored in midstream. This technique was employed along the Tigris and Euphrates rivers in 10th-century Iraq , where large shipmills made of teak and iron could produce 10 tons of flour from corn every day for the granary in Baghdad. They also employed water wheels to power a variety of devices, including various water clocks and automata.
Ancient water-wheel technology continued unabated in the early medieval period where the appearance of new documentary genres such as legal codes , monastic charters , but also hagiography was accompanied with a sharp increase in references to watermills and wheels. The earliest vertical-wheel in a tide mill is from 6th-century Killoteran near Waterford , Ireland , [54] while the first known horizontal-wheel in such a type of mill is from the Irish Little Island c.
The earliest excavated water wheel driven by tidal power was the Nendrum Monastery mill in Northern Ireland which has been dated to , although a possible earlier mill dates to Tide mills became common in estuaries with a good tidal range in both Europe and America generally using undershot wheels. Cistercian monasteries , in particular, made extensive use of water wheels to power watermills of many kinds. An early example of a very large water wheel is the still extant wheel at the early 13th century Real Monasterio de Nuestra Senora de Rueda , a Cistercian monastery in the Aragon region of Spain.
Grist mills for corn were undoubtedly the most common, but there were also sawmills, fulling mills and mills to fulfil many other labour-intensive tasks. The water wheel remained competitive with the steam engine well into the Industrial Revolution. At around the 8th to 10th century, a number of irrigation technologies were brought into Spain and thus introduced to Europe.
One of those technologies is the Noria, which is basically a wheel fitted with buckets on the peripherals for lifting water. It is similar to the undershot water wheel mentioned later in this article. It allowed peasants to power watermills more efficiently. It has been used for centuries before the technology was brought into Spain by Arabs who had adopted it from the Romans. Thus the distribution of the Noria in the Iberian peninsula "conforms to the area of stabilized Islamic settlement".
The Noria is relatively cheap to build. Thus it allowed peasants to cultivate land more efficiently in Europe. The assembly convened by William of Normandy , commonly referred to as the " Domesday " or Doomsday survey, took an inventory of all potentially taxable property in England, which included over six thousand mills spread across three thousand different locations.
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The type of water wheel selected was dependent upon the location. Generally if only small volumes of water and high waterfalls were available a millwright would choose to use an overshot wheel. The decision was influenced by the fact that the buckets could catch and use even a small volume of water. So long as these water supplies were abundant the question of efficiency remained irrelevant. By the 18th century, with increased demand for power coupled with limited water locales, an emphasis was made on efficiency scheme.
By the 11th century there were parts of Europe where the exploitation of water was commonplace. Europe began to transit from human and animal muscle labor towards mechanical labor with the advent of the water wheel. Medievalist Lynn White Jr. Harnessing water-power enabled gains in agricultural productivity, food surpluses and the large scale urbanization starting in the 11th century. The usefulness of water power motivated European experiments with other power sources, such as wind and tidal mills. The techniques that developed during this early period such as stream jamming and the building of canals , put Europe on a hydraulically focused path, for instance water supply and irrigation technology was combined to modify supply power of the wheel.
The water mill was used for grinding grain, producing flour for bread, malt for beer, or coarse meal for porridge. One type was fulling mill , which was used for cloth making. The trip hammer was also used for making wrought iron and for working iron into useful shapes, an activity that was otherwise labour-intensive.
The water wheel was also used in papermaking , beating material to a pulp. In the 13th century water mills used for hammering throughout Europe improved the productivity of early steel manufacturing. Along with the mastery of gunpowder, waterpower provided European countries worldwide military leadership from the 15th century.
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Millwrights distinguished between the two forces, impulse and weight, at work in water wheels long before 18th-century Europe. Fitzherbert, a 16th-century agricultural writer, wrote "druieth the wheel as well as with the weight of the water as with strengthe [impulse]". Evangelista Torricelli 's work on water wheels used an analysis of Galileo's work on falling bodies, that the velocity of a water sprouting from an orifice under its head was exactly equivalent to the velocity a drop of water acquired in falling freely from the same height. Log in to get trip updates and message other travelers.
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