overshot weir factory

WATERMAN TILTING WEIR (OVERSHOT) GATESare an overflow-type gate used to control levels in canals, basins and other agricultural, municipal and industrial applications.

Waterman Tilting Weir (Overshot) Gates are an overflow-type gate used to control levels in canals, basins and other agricultural, municipal and industrial applications.

Overshot gates (also known as pivoting weir gates) are used to control upstream water levels. Versatility, efficiency, and safety are the primary reasons the Fresno Overshot Gate is the method of choice for municipal, agricultural, and industrial canal water control.

The overshot wheel is the most common wheel seen in North America. It is a gravity wheel. This means that it harnesses the force of gravity acting vertically on the water as it travels from the top to the bottom of the wheel. Properly designed for a particular site, and correctly timed, an overshot wheel can slow the natural velocity of the falling water to as little as 10% of what it would be if the wheel was not there.

The overshot wheel is most effective when it turns as slowly as possible and can still handle the total flow of water available to it. The optimal rim speed should be only about 3 feet per second. The larger the wheel the slower it will need to turn. The incoming water must be traveling about three times the rim speed of the wheel so that it can fill the buckets effectively. This requires a foot or more of head above the wheel, usually controlled by a gate.

York Civil Pty Ltd engaged AWMA to custom design vertical water control gates, fishway gates and hydraulic actuation systems for SA Water’s Pipeclay and Slaney Weirs.

Five large AWMA Fixed Base Overshot (decant) gateswere developed to simulate overshot flow patterns of the existing stoplogs, whilst Segmented Stopboards were supplied for the new environmental fishways.

The overshot gate leaves were manufactured from marine grade aluminium with grade 316 stainless steel embedded frames and stainless steel dual cylinder actuation systems.

Marine grade aluminium segmented stopboards and AWMA lifting ladders were supplied for the fishway gates. Design features include overshot flows with low velocities for safe fish passage.

As technology advanced, the stream 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 was known as the mid race. The level of water in the millrace could be controlled by a series of sluice gates.

The Tumbling Weir is a circular weir in the town of Ottery St. Mary, Devon, England that allows water from a leat or man-made stream to reach the River Otter.

The existing leat which supplied the old corn mill did not provide a sufficient head of water for the new mill, so the level of the water in the mill basin had to be raised by 2.4 metres. This was achieved by reducing the fall along the leat. Then, as now, the water level was maintained by the circular "tumbling weir", which discharged the overflow into the river through a short tunnel. Water was conveyed from the mill basin to the 5.5 metre water wheel inside the factory (reported to be capable of producing 30 horsepower) by an overhead aqueduct - the factory launder. A second 3.6 metre overshot wheel powered the corn mill.

Today the mill site and the adjoining factory is unoccupied, awaiting re-development. Near the site is the Tumbling Weir Hotel, a converted 17th century thatched house, now a popular hotel and restaurant.

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 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 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.

An undershot wheel 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.

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 the Fall Line of the North American East Coast. Breastshot wheels are the most common type in the United States of America

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 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%,

Overshot wheels require 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 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 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 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 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 a reversible water wheel was by Georgius Agricola and dates to 1556.

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.Vitruvius, including the reverse overshot water-wheel and the Archimedean screw. Many were found during modern mining at 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 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.

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, 418.4–6).Lucretius (ca. 99–55 BC) who likens the rotation of the waterwheel to the motion of the stars on the firmament (V 516).central Gaul.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".

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.

Overshot (and particularly backshot) wheels are the most efficient type; a backshot steel wheel can be more efficient (about 60%) than all but the most advanced and well-constructed turbines. In some situations an overshot wheel is preferable to a turbine.

The power is how fast that energy is delivered which is determined by the flow rate. It has been estimated that the ancient donkey or slave-powered quern of Rome made about one-half of a horsepower, the horizontal waterwheel creating slightly more than one-half of a horsepower, the undershot vertical waterwheel produced about three horsepower, and the medieval overshot waterwheel produced up to forty to sixty horsepower.

A parallel development is the hydraulic wheel/part reaction turbine that also incorporates a weir into the centre of the wheel but uses blades angled to the water flow.

Weir Minerals are specialists in delivering and supporting slurry equipment solutions including pumps, hydrocyclones, valves, screen machines and screen media, rubber and wear resistant linings for global mining and mineral processing, the power sector and general industry. Our products strength lies in the superiority of our hydraulic designs and wear and corrosion and abrasion resistant materials. In slurry pumping, processing and control applications where the cost of ownership often outweighs capital cost as a priority, we help our customers address such issues as longevity, capacity, efficiency of operation, and maintenance. We are there for you and your operation, every step of the way.

The action of the water pushing against the wheels buckets or paddles develops torque on the axle but by directing the water at these paddles and buckets from different positions on the wheel the speed of rotation and its efficiency can be improved. The two most common types of waterwheel design is the “undershot waterwheel” and the “overshot waterwheel”.

The Overshot Water Wheel Design is the most common type of waterwheel design. The overshot waterwheel is more complicated in its construction and design than the previous undershot waterwheel as it uses buckets or small compartments to both catch and hold the water.

This type of water wheel uses gravity to improve output as well as the water itself, thus overshot waterwheels are much more efficient than undershot designs as almost all of the water and its weight is being used to produce output power. However as before, the waters energy is used only once to rotate the wheel, after which it flows away with the rest of the water.

Overshot waterwheels are suspended above a river or stream and are generally built on the sides of hills providing a water supply from above with a low head (the vertical distance between the water at the top and the river or stream below) of between 5-to-20 metres. A small dam or weir can be constructed and used to both channel and increase the speed of the water to the top of the wheel giving it more energy but it is the volume of water rather than its speed which helps rotate the wheel.

Generally, overshot waterwheels are built as large as possible to give the greatest possible head distance for the gravitational weight of the water to rotate the wheel. However, large diameter waterwheels are more complicated and expensive to construct due to the weight of the wheel and water.

Once the bucket is empty of water it continues around the rotating wheel until it gets back up to the top again ready to be filled with more water and the cycle repeats. One of the disadvantages of an overshot waterwheel design is that the water is only used once as it flows over the wheel.

The Pitchback Water Wheel Design is a variation on the previous overshot waterwheel as it also uses the gravitational weight of the water to help rotate the wheel, but it also uses the flow of the waste water below it to give an extra push. This type of waterwheel design uses a low head infeed system which provides the water near to the top of the wheel from a pentrough above.

Unlike the overshot waterwheel which channelled the water directly over the wheel causing it to rotate in the direction of the flow of the water, the pitchback waterwheel feeds the water vertically downwards through a funnel and into the bucket below causing the wheel to rotate in the opposite direction to the flow of the water above.

Just like the previous overshot waterwheel, the gravitational weight of the water in the buckets causes the wheel to rotate but in an anti-clockwise direction. As the angle of rotation nears the bottom of the wheel, the water trapped inside the buckets empties out below. As the empty bucket is attached to the wheel, it continues rotating with the wheel as before until it gets back up to the top again ready to be filled with more water and the cycle repeats.

The Breastshot Water Wheel Design is another vertically-mounted waterwheel design where the water enters the buckets about half way up at axle height, or just above it, and then flows out at the bottom in the direction of the wheels rotation. Generally, the breastshot waterwheel is used in situations were the head of water is insufficient to power an overshot or pitchback waterwheel design from above.

Breastshot waterwheels use about the same gravitational weight of the water to rotate the wheel but as the head height of the water is around half that of a typical overshot waterwheel, the buckets are a lot wider than previous waterwheel designs to increase the volume of the water caught in the buckets.

Weirs have played a key role in the history of Marple and Mellor, providing a reliable source of power to the early mills and a steady flow of of water for washing to the mills engaged in bleaching and printing. We have already looked at the more modern weir built in Brabyns Park by the Environment Agency

It is perhaps useful to examine the typical layout of a weir and the associated channels alongside a river which would provide power to a mill. A head of water is stored in a pond on the river, known as the dam, and this is created by the damming of the river by a weir. Water was usually intended to flow over the weir but there were often arrangements for the overflow of excess water, controlled by sluices or shuttles. From the dam (usually from one end of the weir) water was led into a leat, the head goit (aWeirlso controlled by shuttles), which carried it parallel to the river towards the mill; here the water would enter a small reservoir, the fore-bay, before being carried in an iron or wooden pentrough to the waterwheel itself. The most efficient design of wheel fed water at the top - an overshot wheel. However, the topography might necessitate water being introduced at a lower level, either half way (breast shot) or at the base (undershot). If these designs are used there is only a slight reduction in efficiency. After turning the wheel, the water would enter the tail goit to be returned to the river downstream of the mill.

Once the Goyt has passed through the Torrs in New Mills it creates a wide valley with extensive flood plains - eminently suitable for spreading out long lengths of cloth as required by bleach and dye works. All these works needed clean water so they had large settling ponds alongside the works, fed by water from weirs on the river. Three separate factories, all operating as printworks, were established within a short stretch of the river.

Waterside Weir SJ 98255 85239 -The first of these was Waterside Mill, established in 1804. It had a difficult time from the first and by 1828 it was converted into a cotton spinning mill and eventually into a paper mill. Despite its rather varied history and changing ownership it is one of the few mills still working today, as Northwood Tissues. The weir no longer serves any purpose.

Woodend Weir SJ 97853 85708 -A decade before Waterside Mill, land was leased from Peter Legh of Lyme at Woodend and the Woodend Printworks established. This too had a succession of owners until it came under the control of Strines Printworks in the 1870s and was used as an extension of the main factory but eventually demolished so only the settling ponds remain.

Strawberry Hill SJ 96827 87622 -This (above) was the key weir for Mellor Mill, diverting the water flow into the mill ponds, or Roman Lakes as they are now known. The weir is still in relatively good condition after 230 years, a tribute to the quality of the original workmanship. For modern purposes there is good access to the site but only the weir can be used to provide a head for hydro. Nevertheless there is a head of 2.7 m in moderate flow.

Brabyns Park SJ 96419 90046 -Locally known as Wright’s Folly, this weir was completed to a very high standard by Nathaniel Wright, the owner of the Brabyns estate, in 1804. The local story is that Wright built the weir in order to power a factory he intended to build on the estate. However, once he had built it, he realised that it would be necessary to flood the estate in order to power a mill from it. It is a nice story but that is all it is - the real reason is much more interesting.

He set his sights on the burgeoning cotton industry and built the weir on the Goyt in anticipation of powering a mill. He agreed to sell this weir to Jesse Howard, a prominent Stockport mill owner, together with the right to return the water to the river further downstream, giving a fall of 23 feet. A total of three agreements were signed in 1809 and 1810 changing the price from an annual rental of £330 to a purchase price of £6600 (£530,000 in current value.)

Compstall SJ 97342 91280 -This is a very substantial weir, rivalling the Brinnington weir in overall size. It dams the Etherow, a tributary of the Goyt, in order to feed the mill ponds and power Compstall Mill. It was built in 1826 by George Andrew and served its purpose for well over a century. Somewhat surprisingly Stockport MBC have not looked at the possibility of using this for generating hydro power; perhaps because of ownership issues.

This weir was built to provide a supply of water to the Chadkirk dye works. It was badly breached during floods a generation ago but the offtake can still be seen slightly upstream on the Romiley bank. It was built by the Siddalls for their works as they leased the land from Lady MacDougal who owned much of the immediate area. The weir is now largely destroyed and it wasn’t helped when the Sustrans Bridge was erected on almost exactly the same site. Close by, and about 100 metres downstream of the weir, is the ford which was a popular route between Romiley and Marple.

Otterspool SJ 93648 89433 -Just like Brabyns, this weir was built but never used. Once again the Stockport mill owner, Jesse Howard was involved. In the early nineteenth century he was engaged in fierce competition with Peter Marsland, another mill owner. They both had mills in the lower reaches of the Goyt and both abstracted water to power their mills. On two occasions, each erected a mill upstream of their rival, thus depriving them of the power they had planned for. In 1825 Howard bought a considerable portion of the Arderne estates in Bredbury and on this land planned to build a great mill race which would bypass Peter Marsland’s latest factory.

Woodbank SJ 91666 90400 -In the late eighteenth and early nineteenth century, water power was the source of fierce competition Adjacent to Woodbank Park, this was Nab weir, which fed water into a tunnel system supplying Peter Marsland’s mills. Built in 1810 it acted as an additional supply to an existing system.

Stringers SJ 90837 90633 -This was a very early weir supplying a factory complex along New Bridge Lane owned by the Howard family. It was named after the factory manager. In the summer months the tunnel from this weir “drew every drop of water” from the Goyt. Even though the water was returned below New Bridge Lane it must have caused considerable opprobrium from other mill owners. In the current era it offers good potential for hydro generation as the weir has a height of 1.8m.

St Mary’s Way SJ 90382 90711 -This weir, just upstream from where St Mary’s Way crosses the Goyt, was built to provide water power directly to the New Bridge Lane factories.

Asda SJ 89877 90611 -This next weir, just upstream of Asda, fed directly into the Portwood reservoir which was built in 1808 by Peter Marsland on meadowland he had bought. This was linked, via a tunnel system, to mills on the other side of the river.

City Centre SJ 89700 90838 -Stockport MBC describes this weir as ‘City Centre’ but this description is a little premature, to say the least. Stockport does not have a cathedral and so far, Her Majesty has not deigned to award it a charter. It is also completely inaccessible and therefore unsuitable for hydro use.

Castle Hill SJ 93070 92950 -Located on the Tame which is the border between Stockport and Tameside, this is a large capacity weir which used to provide a head of water for a mill a long way down stream. In total, measuring the weir and the goit, there is a head of 6.2m but the goit, which is 700m in length, is in a dilapidated state. By itself, the weir provides a head of water of 2.4m.

Brinnington SJ 90621 91861 -This is the largest weir in the borough an is a spectacular structure. Initially developed in 1796 for a mill near the Tesco superstore. The goit that it originally fed has disappeared. Access is better on the south bank but a hydro station on the north bank would be a cheaper site to develop. The head is 4.7 m in moderate flow. Apparently the Tame has lower water quality than the Goyt so the latter river is given priority for fish migration investment within the Mersey basin, along with the Bollin.

Confluence SJ 89692 90854 -This isn’t a weir but a confluence - where the Tame meets the Goyt. From hereon the combined river is officially the Mersey though until the eighteenth century the Mersey began at the confluence of the Goyt and the Etherow. The Mersey was the traditional boundary between Mercia and Northumbria.

Mersey Square SJ 89224 90300 -To the west of the town centre, by the 1790s there were five new water-powered mills along the Mersey as far as Brinksway. Next to these factories their owners built weirs across the river, to build up a sufficient head of water to turn their water wheels.

Brinksway SJ 88375 89972 -Near the Co-op pyramid. The origin not known but it is thought to supply dye works rather than power application. In general terms weirs need to be at least one metre high in order to work efficiently. The height of this weir is estimated as 50 cms so it is probably not viable for hydro.