reverse overshot water wheel manufacturer

Frequently used in mines and probably elsewhere (such as agricultural drainage), the reverse overshot water wheel was a Roman innovation to help remove water from the lowest levels of underground workings. It is described by Vitruvius in his work

The Roman author Vitruvius gives explicit instructions on the construction of dewatering devices, and describes three variants of the "tympanum" in Chapter X of

Pliny the Elder is probably referring to such devices in a discussion of silver/lead mines in his silver in his time, many of the silver mines having been started by Hannibal. One of the largest had galleries running for between one and two miles into the mountain, "water-men" (in Latin "aquatini") draining the mine, and they

That they stood suggests that they operated the wheels by standing on the top to turn the cleats, and continuous working would produce a steady stream of water.

Fragments of such machines have been found in mines which were re-opened in the Victorian era in Spain, especially at Rio Tinto, where one example used no less than 16 such wheels working in pairs, each pair of wheels lifting water about 3.5 metres (11 ft), so giving a total lift of 30 metres (98 ft). The system was carefully engineered, and was worked by individuals treading slats at the side of each wheel. It is not an isolated example, because Oliver Davies mentions examples from the Tharsis copper mine and Logroño in Spain, as well as from Dacia. The gold deposits in Dacia, now modern Romania were especially rich, and worked intensively after the successful Roman invasion under Trajan. According to Oliver Davies, one such sequence discovered at Ruda in Hunedoara County in modern Romania was 75 metres (246 ft) deep. If worked like the Rio Tinto example, it would have needed at least 32 wheels.

One such wheel from Spain was rescued and part of it is now on display in the British Museum. Some of the components are numbered, suggesting that it was prefabricated above ground before assembly in the underground passages. In the 1930s, a fragment of a wooden bucket from a drainage wheel was found in deep workings at the Dolaucothi gold mine in west Wales, and is now preserved in the National Museum of Wales in Cardiff. It has been carbon dated to about 90 AD. From the depth of 50 metres (160 ft) below known open workings, it can be inferred that the drainage wheel was part of a sequence just like that found in Spain. The shape of the edge of one of the lifting buckets is almost identical with that from Spain, suggesting that a template was used to make the devices.

They were also used in series, so increasing the lift of water from the workings. However, they must have been more difficult to operate since the user had to stand on a slanting surface to turn the screw. The steeper the incline, the greater the risk of the user slipping from the top of the screw. No doubt the reverse water wheel was easier to use with a horizontal treading surface. On the other hand, the screw could be operated by a crank handle fitted to the central axle, but would be more tiring since the weight of the operator does not bear on the crank, as it does when trod from above.

Like the reverse water wheel, the cochlea was used for many other purposes apart from draining mines. Irrigation of farmland would have been the most popular application, but any activity which involved lifting water would have employed the devices.

Multiple sequences of water wheels were used elsewhere in the Roman Empire, such as the famous example at Barbegal in southern France. This system was also a stack of 16 wheels but worked like a normal overshot wheel, the wheels driving stone mills and used to grind grains. The water mills were worked from a masonry aqueduct supplying the Roman town at Arles, and the remains of the masonry mills are still visible on the ground today, unlike the underground drainage systems of the mines, which were destroyed by later mining operations. Other such sequences of mills existed on the Janiculum in Rome, but have been covered and changed by later buildings built on top of them.

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Water wheel design has evolved over time with some water wheels oriented vertically, some horizontally and some with elaborate pulleys and gears attached, but they are all designed to do the same function and that is too, “convert the linear motion of the moving water into a rotary motion which can be used to drive any piece of machinery connected to it via a rotating shaft”.

Early Waterwheel Design were quite primitive and simple machines consisting of a vertical wooden wheel with wooden blades or buckets fixed equally around their circumference all supported on a horizontal shaft with the force of the water flowing underneath it pushing the wheel in a tangential direction against the blades.

These vertical waterwheels were vastly superior to the earlier horizontal waterwheel design by the ancient Greeks and Egyptians, because they could operate more efficiently translating the hydrokinetic energy of the moving water into mechanical power. Pulleys and gearing was then attached to the waterwheel which allowed a change in direction of a rotating shaft from horizontal to vertical in order to operate millstones, saw wood, crush ore, stamping and cutting etc.

Most Waterwheels also known as Watermills or simply Water Wheels, are vertically mounted wheels rotating about a horizontal axle, and these types of waterwheels are classified by the way in which the water is applied to the wheel, relative to the wheel’s axle. As you may expect, waterwheels are relatively large machines which rotate at low angular speeds, and have a low efficiency, due to losses by friction and the incomplete filling of the buckets, etc.

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 Undershot Water Wheel Design, also known as a “stream wheel” was the most commonly used type of waterwheel designed by the ancient Greeks and Romans as it is the simplest, cheapest and easiest type of wheel to construct.

In this type of waterwheel design, the wheel is simply placed directly into a fast flowing river and supported from above. The motion of the water below creates a pushing action against the submerged paddles on the lower part of the wheel allowing it to rotate in one direction only relative to the direction of the flow of the water.

This type of waterwheel design is generally used in flat areas with no natural slope of the land or where the flow of water is sufficiently fast moving. Compared with the other waterwheel designs, this type of design is very inefficient, with as little as 20% of the waters potential energy being used to actually rotate the wheel. Also the waters energy is used only once to rotate the wheel, after which it flows away with the rest of the water.

Another disadvantage of the undershot water wheel is that it requires large quantities of water moving at speed. Therefore, undershot waterwheels are usually situated on the banks of rivers as smaller streams or brooks do not have enough potential energy in the moving water.

One way of improving the efficiency slightly of an undershot waterwheel is to divert a percentage off the water in the river along a narrow channel or duct so that 100% of the diverted water is used to rotate the wheel. In order to achieve this the undershot wheel has to be narrow and fit very accurately within the channel to prevent the water from escaping around the sides or by increasing either the number or size of the paddles.

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.

These buckets fill with water flowing onto the wheel through a penstock design above. The gravitational weight of the water in the full buckets causes the wheel to rotate around its central axis as the empty buckets on the other side of the wheel become lighter.

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.

When the individual buckets are filled with water, the gravitational weight of the water causes the wheel to rotate in the direction of the flow of water. As the angle of rotation gets nearer to the bottom of the wheel, the water inside the bucket empties out into the river or stream below, but the weight of the buckets rotating behind it causes the wheel to continue with its rotational speed.

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 difference this time is that the waste water emptied out of the rotating bucket flows away in the direction of the rotating wheel (as it has nowhere else to go), similar to the undershot waterwheel principal. Thus the main advantage of the pitchback waterwheel is that it uses the energy of the water twice, once from above and once from below to rotate the wheel around its central axis.

The result is that the efficiency of the waterwheel design is greatly increased to over 80% of the waters energy as it is driven by both the gravitaional weight of the incoming water and by the force or pressure of water directed into the buckets from above, as well as the flow of the waste water below pushing against the buckets. The disadvantage though of an pitchback waterwheel is that it needs a slightly more complex water supply arrangement directly above the wheel with chutes and pentroughs.

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.

The disadvantage here is that the gravitational weight of the water is only used for about one quarter of the rotation unlike previously which was for half the rotation. To overcome this low head height, the waterwheels buckets are made wider to extract the required amount of potential energy from the water.

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.

The disadvantage of this type of design is an increase in the width and weight of the water being carried by each bucket. As with the pitchback design, the breastshot wheel uses the energy of the water twice as the waterwheel is designed to sit in the water allowing the waste water to help in the rotation of the wheel as it flows away down stream.

Historically water wheels have been used for milling flour, cereals and other such mechanical tasks. But water wheels can also be used for the generation of electricity, called a Hydro Power system.

By connecting an electrical generator to the waterwheels rotating shaft, either directly or indirectly using drive belts and pulleys, waterwheels can be used to generate power continuously 24 hours a day unlike solar energy. If the waterwheel is designed correctly, a small or “micro” hydroelectric system can produce enough electricity to power lighting and/or electrical appliances in an average home.

Look for Water wheel Generators designed to produce its optimum output at relatively low speeds. For small projects, a small DC motor can be used as a low-speed generator or an automotive alternator but these are designed to work at much higher speeds so some form of gearing may be required. A wind turbine generator makes an ideal waterwheel generator as it is designed for low speed, high output operation.

If there is a fairly fast flowing river or stream near to your home or garden which you can use, then a small scale hydro power system may be a better alternative to other forms of renewable energy sources such as “Wind Energy” or “Solar Energy” as it has a lot less visual impact. Also just like wind and solar energy, with a grid-connected small scale waterwheel designed generating system connected to the local utility grid, any electricity you generate but don’t use can be sold back to the electricity company.

In the next tutorial about Hydro Energy, we will look at the different types of turbines available which we could attach to our waterwheel design for hydro power generation. For more information about Waterwheel Design and how to generate your own electricity using the power of water, or obtain more hydro energy information about the various waterwheel designs available, or to explore the advantages and disadvantages of hydro energy, then Click Here to order your copy from Amazon today about the principles and construction of waterwheels which can be used for generating electricity.

There are many wheel configurations, vane/blade shapes and water-flow patterns.  Undershot wheels and horizontal wheels were the most common choices for tide mills. Since the height of the impoundment area was the height of high tide, the head of water was probably not high enough to power an overshot wheel.

Probably the most important of the early engines which utilized water power was the vertical waterwheel. Its two basic forms are the undershot and the overshot. The undershot vertical wheel rotated in the vertical plane and had a horizontal axis. It normally had flat radial blades attached to its periphery and derived its motion from the impact of water flowing under the wheel and against these blades. While capable of working on any convenient stream without mill races (narrow artificial water channels, it worked most effectively in a race and with a stable volume of water running at a fairly high velocity. [Stronger than a Hundred Men: A History of the Vertical Water Wheel by Terry S. Reynolds Baltimore: The Johns Hopkins University Press, 1983.]

The Undershot Wheel worked in a running stream and could turn in shallow water. It was often built by the first settlers since it was relatively simple to set up … They were common in the early days when a dam could be built to compensate for dry periods … . [Mill: The History and Future of Naturally Powered Buildings by David Larkin. New York, 2000.]

The tub wheel could only work where the water flowed regularly throughout the year, and needed at least an eight-foot fall. The tub wheel was horizontal and was described as acted upon by percussion of water. The shaft is vertical, running the stone of top of it, and serves as a spindle. The water is shot on the upper side of the wheel in the direction of a tangent fitted with blades. It revolves in a sturdy tub, projecting far enough above the wheel to prevent the water from shooting over it, and whirls above it until it strikes the buckets. . [Mill: The History and Future of Naturally Powered Buildings by David Larkin. New York, 2000.]

The overshot vertical wheel was a much more efficient device. Water was fed at the top of the overshot wheel into “buckets” or containers built into the wheel’s circumference, and the weight of the impounded water, rather than its impact, turned the wheel. Each “bucket” discharged its water into the tail race at the lower portion of its revolution and ascended empty to repeat the process. The overshot wheel was usually more expensive than the undershot, since a dam and an elevated head race were normally required to build up a large fall of water and to lead the water to the wheel’s summit. It was suitable mainly to low water volumes and moderately high falls.

It is likely that the [emergence of undershot and overshot wheels] was at least partially influenced by several more primitive devices which tap the power of falling water – the water lever, the noria, and the primitive horizontal watermill. [Stronger than a Hundred Men: A History of the Vertical Water Wheel by Terry S. Reynolds Baltimore: The Johns Hopkins University Press, 1983.]

The overshot wheel required a dam above it so that the weight of water falling on it would make it turn. After one-third of a revolution, the water was spilled from the wheel. The water first striking the wheel gave it momentum, but the weight of the water in its buckets kept it turning. [Mill: The History and Future of Naturally Powered Buildings by David Larkin. New York, 2000.]

The difference between the pitch-back and the overshot wheels is that the trough stops shorter here and pours the water onto the wheel before the top of the wheel, or ‘on the near side’ as the millwrights used to say. The result therefore is that the wheel revolves in the opposite direction from the overshot, i.e. towards the flume or head-race. The buckets face in the opposite direction and the water therefore falls off at the same side as that on which it was received. [British Water-Mills by Leslie Syson. London, 1965]

The breast wheel, like the undershot wheel, turned in the opposite direction to the overshot wheel and received water above its center shaft at the nearest point of the water supply, and revolved easily because it was less loaded with water. . [Mill: The History and Future of Naturally Powered Buildings by David Larkin. New York, 2000.]

The flutter wheel was used when there was a large supply of water. It was small, low and wide—about three feet in diameter and up to eight feet wide. It got its attractive name from the sound it made. As the wheel went around, the blades cut through the entering water, making a noise like the fluttering wings of a bird. It was used almost entirely to power early sawmills. . [Mill: The History and Future of Naturally Powered Buildings by David Larkin. New York, 2000.]

The turbine with its curved blades, eventually replaced the waterwheel [in the mid-nineteenth century]. … Roy S. Hubbs pointed out that older undershot waterwheels presented a flat blade for the incoming water to impact, allowing half of the velocity to pass through unchecked. The Poncelet design [and the later resulting turbine] presented a curved blade with its lip angled tangentially to the incoming water … Benoit Fourneyron turned the wheel on its side and dropped the water into its center, allowing the water to flow simultaneously out of all the passages between the blades. … Since the turbine used all the openings between its blades simultaneously, it could be made much smaller. It turned much faster than the larger wheels. . [Mill: The History and Future of Naturally Powered Buildings by David Larkin. New York, 2000.]

Operating on the seesaw principle, the water lever utilized the power of falling water, but without the continuous rotary motion of water wheels. One end of a pivoted beam was equipped with a spoon-shaped bucket. On the other end was a hammerlike counterweight used for pounding or crushing. Water was directed into the bucket from a falling stream; the bucket filled, overweighed the hammer, and lifted it. The ascent of the bucket caused the water to spill; the hammer than overbalanced the bucket and fell. The cycle was then repeated to produce a steady pounding action.

The noria used for raising water, was form of undershot water wheel, but it activated no machinery (such as gears or millstones) beyond itself. It was simply a large vertically situated wheel, sometimes as much at 50-80 feet in diameter, equipped with radial blades which rotated the apparatus as they were impacted by the flowing water in which the lower portion of the wheel was immersed. Buckets of wood, bamboo, or pottery were attached to the rim of the wheel. As the device rotated, they were filed with water at the bottom of the wheel; the water was carried upwards in the buckets and emptied near the top of the wheel into a trough. The buckets were the returned empty to the bottom of the wheel to repeat the process.

Based on the surviving evidence, it would appear that the vertical undershot watermill, the horizontal watermill, and the noria appeared almost simultaneously in the Mediterranean world in the first century B.C. and that at approximately the same time some form of water-powered prime mover was developed in China.

By the close of the Middle Ages watermills were in use on streams of every type. They dammed up the rivers of medieval man; they were on the banks of his brooks and creeks, in the middle of his rivers, under his bridges, and along his coastlines. They impeded navigation and created streams (in the form of mill races and power canals) and lakes (in the form of storage reservoirs behind waterpower dams) where none had existed before.

Through all of antiquity and on into the early Middle Ages almost the only work to which the force of falling water was applied was grinding wheat. This was always to be one of its more important functions. But by the tenth century, European technicians had begun to adapt the vertical water wheel to other tasks. By the sixteenth century, in addition to flour mills, there were hydropowered mills for smelting, forging, sharpening , rolling slitting, polishing, grinding, , and shaping metals. Water wheels were available for hoisting materials and for crushing ores. There were mills for making beer, olive oil, poppy oil, mustard, coins, and wire. Water wheels were used in the preparation of pigment, paper, hemp, and tanning bark, and for fulling, sawing wood, boring pipes, and ventilating mines.

[In North America] the resort to water power usually came quickly after settlement [in colonial America]. The first permanent English settlement in North America was at Jamestown, Virginia, in 1607. Early in that settlement’s history the Virginia Company instructed its governor to build watermills on every plantation. By 1694 Virginia had five watermills. Maryland had a watermill in 1634, the very year it was first settled, and Swedish authorities responsible for settlements on the Delaware in the1640s made the erection of watermills one of their first concerns. The colony of Massachusetts, first settled in 1620, had a watermill at Dorchester by 1633, and mills at Roxbury, Lynn, and Watertown by 1635. These were all flour mills. But according to one authority, the Piscataqua River above Portsmouth, N.H., was dammed for a sawmill as early as 1623. In 1646, on the Saugus River, Massachusetts built an iron mill, complete with water-activated trip-hammers, blast furnace, bellows, rollers, and slitters. By 1700 there were few New England villages without a watermill.

The path that the water takes through a turbine and the general layout is often used for classification, like tangential-flow, radial-flow cross-flow and axial-flow. Below are the various categories of ‘water driven prime mover that can be used to convert the ‘potential energy’ in a river or stream into usable ‘mechanical’ or ‘electrical’ energy. This section continues with information on what types of turbine are suitable in various sites and applications.

Gravity devices are those where any kinetic energy present at the entry of the device is either minimal or lost in turbulence and does nor contribute measurably to the output of the device. Such devices include most waterwheel types, Archimedes screws (where the outer case rotates with the flutes); Hydrodynamic screws (as used for sewage pumping and now being used in reverse as low-head prime-movers); Norias (more commonly used for raising water) and consist of a string of buckets like an overshot waterwheel attached to form a chain, and positive displacement devices or hydraulic engines.

Impulse turbines are those where the potential energy in a ‘head of water’ is largely converted into kinetic energy at a nozzle or spout. The simplest of such devices is the Gharat or Norse Wheel (where the conversion to kinetic energy takes place in an open flume). The more conventional devices harness the potential energy in a pipeline or penstock that terminates in a nozzle. The flow path through the turbine is usually used to describe the specific device, namely, tangential-flow, radial-flow, cross-flow, axial-flow or mixed-flow. Specific turbine designers have been associated with most of these devices, though confusion can result because they often designed several different types of device (The Pelton Waterwheel Company also made cased reaction turbines, Herschel pre dates Jonval’s patent that was the precursor of the Turgo Impulse wheel, a single nozzle version developed by Gilkes. Donat Banki, a Hungarian was also making cross-flow turbines many years before Mitchell and Ossburger came on the scene.

Reaction turbines are those where the turbine runner is usually completely flooded and the transfer of energy from the water to the turbine runner is achieved by a combination of reaction and/or lift. Some designs of cross-flow turbine in common use a combination of impulse and reaction. Reaction turbines have had a more complex development, with many designers and factories adding features such as movable ‘wicket gates’ that resulted in Francis’s name becoming the tag by which this group of turbines are now known. The Kaplan turbine developed in the 1930s is a sophisticated variable geometry version of the ‘propeller turbine’ that as its name suggests is similar to a ship’s propeller in a housing. Halfway between these types is the single regulated propeller turbine, where either the runner blades or the ‘guide vanes’ (wicket gates) are adjustable.

Free-stream devices encompass large slow running wheels and turbines, some of which are being tried out for marine energy applications. Like wind turbines, the power delivered increases as a cube of the velocity, such that a doubling of the velocity gives an eight fold increase in power output. The devices themselves are very large and slow running and only have very specialised applications for extracting small amounts of power from bank-side locations on very large rivers.

High head sites with over 20 metres of fall, where the water is conveyed directly to the turbine in a pipe (penstock) or via an open canal followed by a piped section, generally use impulse turbines. The reason is that high head sites are usually subject to significant changes in water flow and reaction turbines like the Francis are not able to cope with such variations. Silt in the water can also cause a lot of damage to Francis turbines that is expensive to repair.

One of the most successful high head turbines was developed in California during the gold rush from a device referred to as a ‘hurdy gurdy’ that was basically a cartwheel with buckets around the periphery. A carpenter by the name of Lester Pelton came up with the now familiar double bucket shape and went on to found ‘The Pelton Watewheel Company’ of San Francisco. The bucket design was later improved by Doble who joined the company as an engineer in 1899. Doble’s improvement is the central cut-out in the bucket that prevents the water jet from first striking the back of the bucket and wasting energy. www.oldpelton.net. Today, similar machines are operating from over 1000 metres of fall and generating up to 100MW of power.

A simple weir is all that is required to divert the stream into the penstock (pipeline) via a de-silting chamber to remove any sand. Water storage may be included if the terrain allows and if it is advantageous to generate more power for short periods or where it is necessary to store water for generation when flows are very low. A low-pressure pipe or open canal may also be used to reduce to overall cost if it allows a short steep decent to the powerhouse using less high-pressure pipe.

Pelton turbines are efficient over a very wide range of flows but at lower heads the speed is too low for belt drives, so we reduce the pitch circle and modify the bucket shape to increase the specific speed. The jets may have plain nozzles or adjustable spear valves to adjust the water consumption to the available stream flow. It is usual with larger machines to have ‘deflectors’ that divert the water away from the runner for controlling the speed without altering the water flow. They can also be used for emergency shutdown.

For thousands of years waterpower has been harnessed for milling and pumping water. In the Developing World many are still in daily use, but in Western Countries they have usually fallen into disrepair as a result of competition from diesel and electric power. In the U.K. there were over 70,000 working mills at the end of the 18th century and now there are a few hundred. These mills fall into a number of categories that will determine their suitability for redevelopment.

The waterwheels that were used on these sites in the U.K. are usually of the Roman or horizontal shaft type, though the vertical shaft type is much more common in Mediterranean and Asian countries. Depending on the fall of water available, the horizontal wheels are classified into ‘Overshot’, ‘Breast-shot’, ‘Back-shot’ and ‘Under-shot’. With the exception of projects to restore a mill to its original design, or where the visual appearance is important to maintain, only the overshot wheel is suitable for a new power generation projects.

Overshot waterwheels are the most fish-friendly and able to handle leaves and sticks. A similar device is the Noria or chain wheel, which has the disadvantage of potential more maintenance, but it runs faster, is more efficient and easier to install than an overshot waterwheel.

The power available is a function of the head and flow so building a large wheel will only increase the cost and reduce the shaft speed but not increase the power. Major components in the cost are the primary gearbox and the material required in the construction of the wheel itself. We are happy to build any type of waterwheel, but the cost is likely to be significantly greater than that of an equivalent turbine, when you take the gearing and installation costs into consideration. There are no short cuts with waterwheels and the engineering has to be good, on account of the high torque in the low speed drive.

Mills with ponds are seldom suitable for redevelopment for anything other than a few kilowatts because the water flow is obviously too little to sustain the mill on a continuous basis, and it is much too expensive to install a wheel or turbine that can only be operated for a few hours a day. In some cases the ponds were only used in the summer months when the water was low, but today we are looking to the higher winter flow for the bulk of the power that can be used for heating. There is always a loss of head into and out of the pond, but this may be recoverable with a turbine installation.

Mills with leats, lades or channels take their water from a water course along the side of a valley at a gradient that is usually less than one in five hundred. At a suitable point when enough fall can be achieved in one place, the mill is built. The only limitations to future development are the actual head and flow available. Since there was a mill there anyway there should be enough power for domestic purposes. Improvements to the leat and head are usually possible but are very site specific. Modern mini excavators make leat widening and maintenance much easier than when the mills were first built.

Mills on weirs or with short wide diversion channels present the most difficult challenge for the developer. The available head may only be a metre or so and the flow required to generate useful amounts of power will be several cubic metres of water per second. The undershot waterwheels that were originally used at these sites are totally redundant on account of their high cost and low efficiency. The exact layout of the site becomes increasingly important with the lower falls, because access for excavators and to install the large items of equipment is more difficult.

Open flume installations are the most usual for the very low head sites, and employ fixed geometry propeller turbines on account of their simple construction and high ‘specific speed’. The more complex variable ‘Kaplan’ type turbines are not economic for these small schemes and it is easier to achieve ‘flow control’ by installing more than one machine or by running until the water has fallen by say 100mm and then switching off automatically until it has come up again. This latter system can be used for heating

Tubular turbines of the propeller type can be used for mill sites with a higher head, typically those that originally employed ‘Overshot’ waterwheels. Many different arrangements are possible to suite existing civil works but the main compromise arises from their inflexible performance. If the mill is only extracting a small percentage of the available water from the main river, then there is no problem. If however the water flow reduces below that which is required to supply the turbine, either water storage, another smaller turbine or a change in turbine speed will be required.

Archimedes Screws have come into the news in recent years because of their reported fish friendliness, but firstly the units being described are NOT Archimedes screws but Screw pumps running in reverse (hydrodynamic screws) and secondly the hydrodynamic screws are not as friendly as they might first appear. The difference in respect to fish friendliness is potentially significant since the true Archimedes screw has its outer casing rotating with the screw flights so that no fish, eel or lampray can be killed or injured by getting caught in the gap or abraded against the concave that will undoubtedly become rough with time and damage.

Low cost open impulse turbineshave been developed by us, primarily for projects in the Developing World. Installed outside the mill house like a waterwheel, it is an economic alternative for smaller domestic sites here in the U.K. They cannot be used with a draft tube since the runner is open to the atmosphere but the installation and maintenance is much simpler. The valve control shaft is extended through the mill house wall to an operating lever on the ,inside or a simple open shoot conveys the water directly to the runner in the manner of the old ‘flutter wheels’ used in the USA in the 19c. Installation work is usually kept to a minimum and may be in an old waterwheel pit or even behind an existing wheel under the launder. A vertical shaft version like the Indian Gharat can produce considerably more power by increasing the entry area, whilst maintaining its self-cleaning characteristics.

Portable turbines are highly adaptable and be assembled on site in a few hours. Applications include ‘Rural Development’, camping and field hospitals. Typical outputs range from 200 watts to 50 kW. The inlet works are prefabricated and the pipeline is either flexible polyethylene or ‘lay-flat’ coiled pipe. The whole unit can be built into a trailer or air-portable unit for rapid deployment in the field. The buckets that are divided along their centre line by a splitter ridge, turn the jet of water that is directed at them, through 1800 so that the energy is transferred efficiently to the shaft.

Turbines that are suitable for a particular type of site and turbines that are suitable for particular type of application are referred to as ‘groups’. Hence you can have a group of ‘Hillstream’ turbines for upland sites, or a group of ‘Agricultural’ turbines for agricultural applications. The site may be defined topographically as an upland or ‘Hillstream’ site, or as a lowland or ‘Millstream’ site. Each of these groups I then divided into two sub-groups depending on the actual site layout and general features. The ‘Hillstream’ group is comprised of vertical and horizontal shaft impulse turbines that may be either direct drive, belt drive or overhung from the generator. The application for the plant may be to generate electricity, mechanically power machinery or pump water for irrigation or for a drinking water supply. The application will also have a bearing on the materials, the sophistication, the governing system and the general build.

Water has been used to power simple and complex mills since antiquity. In colonial America, mills were powered by wooden waterwheels, but as technologies and manufacturing changed during the 19th century, water turbines began to be used more and more. In the period of 1850-1880 dozens of American manufacturers made cast iron turbines of nearly every conceivable configuration. Turbines could be readily ordered in different sizes that were suited for the specific water flow, shafting, and gearing needed for a particular mill. Turbines aren’t as susceptible to reduced flow when the water levels in the turbine pit are high or flooded. Perhaps best of all, turbines were iron and therefore did not require constant repair of a wooden waterwheel that began to rot from intermittent soaking even before installation was complete.

To explain the mechanism for this surface ferroportin-independent Fe exit, we explored the possibility of GAPDH-mediated apotransferrin trafficking into cells for sequestration and evacuation of intracellular Fe. This could involve a process akin to receptor-mediated trafficking of holotransferrin into cells for intracellular Fe delivery, followed by recycling of the residual apotransferrin along with receptor back to the cell surface, but instead operating in reverse. Such a form of retroendocytosis has previously been described for high-density lipoprotein (HDL) and apolipoprotein A-I endocytosis (followed by recycling and secretion) in diverse cell types (including macrophages), and has been linked to lipid intake and cholesterol efflux (Azuma et al., 2009; Pagler et al., 2006; Röhrl and Stangl, 2013). Fe-loaded J774, THP1 and CHO-TRVb cells all demonstrated a significant increase in internalization of radiolabeled apotransferrin, whereas GAPDH-knockdown THP1 and CHO-TRVb cells failed to increase apotransferrin uptake (Fig. 2A). Confocal microscopy analysis demonstrated the colocalization of GAPDH (that was initially resident on the cell surface) with apotransferrin within Fe-loaded cells (Fig. 2B; Fig. S2A). Immunoelectron microscopy analysis also revealed the presence of both proteins in endosomes of CHO-TRVb cells (Fig. 2Di,Dii). Co-immunoprecipitation of biotinylated apotransferrin with GAPDH from Fe-loaded CHO-TRVb and J774 cell endosomes (Fig. 2E), and an acceptor-photobleaching-based Förster resonance energy transfer (FRET) assay (Fig. 2F) confirmed the interaction between the two internalized proteins. The FRET efficiency measured was 27.79%±6.2 (mean±s.d.) (Fig. 2G).

In summary, our current findings suggest that GAPDH mediates the internalization of apotransferrin to facilitate Fe export through treadmilling of this Fe carrier in and out of cells in a manner reminiscent of the reverse overshot water-wheel, which has been in use since antiquity to pump out water from flooded mines. To date, the movement of transition metal ions out of cells has been considered to be only through transmembrane ion channels, and our current results reveal a totally new dimension to cellular metal ion export and also highlight the higher-order multifunctional nature of GAPDH in the maintenance of cellular Fe homeostasis. A schematic representation of this process is presented in Fig. 6.

(For good background information for this article, the reader should read “Waterpower for personal use” in Issue No. 16 and “Design calculations for overshot waterwheels” in Issue No. 17. — Editor)

This is the type most familiar to people where the water is introduced to the top of the wheel by a chute, known as a flume. In spite of the public impression that these machines are low technology, they were actually quite extensively studied by academicians. The first to study them was a Roman named Vetruvius, who wrote what is considered to be the earliest known engineering treatise. The work on waterwheels by Lazare Carnot’ in the early 1700s not only advanced fluid dynamics, but his study was the groundwork for the study of thermodynamics.

As we discussed in previous articles (Issues No. 16 and 17), the most important thing to determine when utilizing a waterwheel is “head”, or how far the water falls. This is important because it has a lot to do with the diameter of the wheel. Ideally, the wheel diameter should should be 90% of the “head”. For convenience we choose some even number, in feet, that is nearly 90%. Unless the wheel is unusually large, we choose a diameter equal to the “head” minus two feet. This two-foot difference will be the depth of our flume.

We will now return to the concept of “spouting velocity.” The water in the flume will flow to the end where it will fall two feet. We must determine how fast it is moving horizontally “and” vertically. You see, once it reaches the end of the flume, it begins to fall again, and gravity causes its downward speed to increase.

If our water falls 2 feet the feet, the equation tells us the velocity will be 11.35 feet per second. At the same time, gravity is pulling the water down as it is moving horizontally.

If we plot several points on a graph (see Figure 1) showing how the water travels horizontally as it leaves the flume, then vertically as gravity pulls on the water, we will get an arcing line. This line is very important. It will be the curvature of our buckets. By curving the buckets this way, the water enters smoothly and without splashing. It is then possible to make use of the velocity energy. Figure 1 is a graph of points for water leaving a two-foot flume.

But how fast will it turn? The most efficient energy transfer occurs when the wheel speed is at 93% of the water speed. For our example, the spouting velocity is 11.35 feet per second. So 93% of that is around 10 feet per second, which is the same as 600 feet-per-minute. You divide this by the working circumference per revolution. This gives you an answer of 19 revolutions per minute. That is your best rotative speed.

The power you will get depends on the width. For our example, let’s assume you have a design flow of 50 cfs (cubic feet per second). When you divide this by the design speed of 10 feet per second, you see you need a bucket area of 5 square feet. If our buckets are 1 foot deep, the wheel should be 5 feet wide, “plus” one foot extra on each side to ventilate the buckets. As the water comes in, the air “must” get out.

One important detail: Put a one-inch diameter hole near the bottom of each bucket. This is to prevent them from sucking air when they are submerged. That can use up half of your power, while only a negligible amount of water leaks out. As I said last issue, power is equal to “flow” times “head” divided by 11.8. Therefore, we have a “flow” of 50 cfs “times” a “head” of 12′ divided by 11.8. 50 X 12 = 600. 600/11.8 = 50.8 kilowatts. To state it another way, 50.8 kilowatts/.746 gives you 68 horsepower. We should assume an efficiency of 90%, so our hypothetical wheel will produce 61 horsepower or 45 kilowatts.

These calculations apply to “any” overshot waterwheel. The only thing that changes among the various designs is the speed or dimensions. Materials should always be a good grade of steel. A36 or B36 works very well. 20 gauge or thicker is good. We always use 1/8″ and ours have withstood direct hits by ice flows of more than a ton. If you use “corten”, a weathering steel, it will not need painting and will acquire a reddish color that resembles wood.

Staticly balance the wheel before installation. No matter how tempting, never use wood. It rots and holds water unevenly. This unbalances the wheel and makes it unsuitable for any use except grinding grain. Be very accurate in all your measurements, especially those concerning “flow” and “head”. If they are wrong, everything is wrong.

I recommend oil-impregnated wood bearing. They can be obtained from the POBCO Bearing Company of Worcester, MA. Waterwheels turn too slowly for ball or sleeve bearings. They cannot maintain a uniform lubricant field. This tends to ruin the bearing quickly. The wood bearings have a “wick” action that maintains uniform lubricant.

Please Note: I have not reproduced all of the photos mentionedon the pages in these sections. I have repoduced some photos in the "images"section, and some in section called "Water Wheel Albums," seeFitz Water Wheel pages. For a complete text and all the photos, please ordera reprint copy from the Mill Bookstore of the

The Fitz I-X-L Steel Overshoot Water Wheel is the product of three generationsof unbroken experience in the design and manufacture of water wheels. Ithigh efficiency is due to its correct mechanical principles and to its carefuldesign and construction.

The manufacture of Overshoot Water Wheels was begun by Samuel Fitz, in Hanover,Pennsylvania., U. S. A., in the year 1840. The industry has been carriedon continuously since that time on the same site under the management ofthe son and grandson of the original founder.

The earlier Fitz Wheels were, of course built of wood. A number of ordersare still being received for iron parts for wooden water wheels, as describedlater in this booklet, but by far the greater part of the business donetoday is the manufacture of the all-steel Overshoot Water Wheels, in whichthe company specializes.

The real credit for the invention of the modern Steel Overshoot Water Wheeland for its development into its present highly efficient form must be givento the late John Fitz. [John Fitz, Inventor and Manufacturer. Born April15, 1847 - Died, April 12, 1914. "He originated the modern Steel OvershootWater Wheel, and rescued from oblivion one of the most useful principlesof Hydraulics."] Very early in his business career he realized thegreat possibilities of this type of water wheel and he devoted the greaterpart of his life to the study of its principles and the improvement of itsefficiency. How well he succeeded is shown by the high regard in which theSteel Overshoot is held today. In spite of this, we have not relaxed outefforts for further improvements, but are constantly striving for stillbetter results in every detail of construction.

The knowledge and experience accumulated by out organization during itslong career in the water wheel business forms an ever greater asset thanout well equipped modern factory. Most of out employees have grown up withus, and our millwrights and mechanics have been trained in this line fromearly youth. In reckoning with your water power problems, therefore, wehave a vast fund of practical experience to draw from and we are glad toplace this freely at the service of out customers.

The Overshoot Water Wheel derives its power directly from the force ofgravity. The illustration shows the principle upon which it works. The weightof the water which is admitted to the buckets, loads one side of the wheel,causing it to revolve.

The water should be applied to the top of the wheel at a point about teninches back of the vertical center line, so that the buckets will fill upjust as they pass over the topmost point of the wheel.

The diameter of an overshoot wheel should be from 2 1/2 to 3 feet less thanthe total fall available. By total fall, we mean the vertical distance fromthe surface of the water in the fore bay or "tank" above the topof the wheel, down to the surface of the water in the tail race or dischargecanal, below the bottom of the water wheel.

Wheels of all types were formerly built of wood. Many picturesque examplesof this method of construction are still to be found in rural districts.The overshoot wheel possessed so many advantages that it soon displacedthe other early types of water wheels. Even with all its crude design andill-suited material, the wood overshoot still persists as a strong competitorof the modern small turbine.

The field of the Overshoot Wheel lies in the development of small powers.It is not suitable for use in very large developments on account of theincrease in size and weight of the wheel as the head and discharge are increasedbeyond certain limits. It can be built in any diameter needed up to 60 feetand in any width desired up to a capacity of 3,000 cubic feet per minutein single units.

The power of an overshoot wheel depends upon both the diameter of the wheeland the width of the wheel. The larger the diameter of an overshoot wheel,the more power it will develop with the same amount of water. The widerthe wheel is made, the more water it will accommodate. The relative powerof two wheels of the same diameter is of course in direct proportion tothe amount of water each wheel is capable of using, if other conditionsare equal. The question of determining the proper size wheel to use forany particular location is one which should usually be left to the judgmentof the builder of the wheel. We do not publish any list of sizes of wheelsin this booklet for the reason that we prefer to have our customer giveus the data, so that we, ourselves, can select the size of wheel he oughtto have.

For any location within the range of its capacity, the overshoot type ofwheel possesses certain decided advantages, over all other types of waterwheels, viz.:

The extent to which any overshoot wheel makes use of these advantages dependslargely upon design of the wheel, its accuracy of construction and the materialof which it is made. The Fitz Steel Overshoot Water Wheel makes use of thesame basic principles as the old wood overshoot, but its superior designenables the Fitz Wheel to develop more than 90% efficiency as compared withthe 60% to 70% efficiency of the wood wheel. The reasons for this are setforth in detail later on in this booklet under the heading "Comparisonwith wood wheels." The efficiency of the Fitz Wheel is not a matterof opinion or guess work. Our wheels are rated according to the resultsshown by rigid test on Hydraulic Testing Flumes.

Developing an efficiency of 90% or more, the Fitz Steel Overshoot is vastlymore efficient than any other type of water wheel known. In the smallerinstallations especially, where the overshoot most frequently competes witha turbine, it is doubtful whether the turbines ever operates with an efficiencyhigher than 70%. It is true that many turbine builders claim high efficienciesfor their wheels, but every experienced turbine user has good reason toknow how far the turbines themselves fall short of their makers" claimswhen confronted with actual running conditions. In every case, where theamount of fall and quantity of flow is suitable for our type of wheel, aFitz Overshoot will develop at least one-third more power than any turbineworking under similar conditions, or 25% more than the best new wood wheelthat can be built.

The above statements are made without prejudice to the turbine type of waterwheel, for we build a turbine wheel ourselves that ranks fully equal tothe best on the market. We are just as glad to sell a turbine wheel as weare to sell an overshoot where the conditions are suitable for a wheel ofthat type, but we will not furnish either kind for a location where we knowthat out customers" interests require the other.

The development of the overshoot water wheel into its present state ofunrivalled efficiency has been the results of many years of thought andeffort. Founded in its present location nearly ninety years ago, this firmhas been building water wheels continuously during all that time, but ithas never ceased to improve and modernize its product.

Up until the advent of the modern Fitz Steel Overshoot Water Wheel an efficiencyof 60% to 70% was considered remarkably good for small water power plant.Today, practically every recent text-book on hydraulics concedes an efficiencyof 90% or more to the "modern steel overshoot water wheel when properlyconstructed." Proper construction means "Fitz Construction,"for no other make of water wheel has approached this high efficiency. FitzWater Wheels form part of the equipment of some of the greatest engineeringcolleges and universities of the world. They have been adopted by many railroadsand by many of the leading engineering firms in this country for use whereverhigh efficiency and perfect reliability are the essential requirements ina small water power development.

A range of four hundred per cent in variation of the amount of water suppliedto this water wheel showed a difference of only 5% in the efficiency ofthe wheel. We quote as follows from an article in the "EngineeringNews" of January 2, 1913, by Prof. Carl R. Weidner, Instructor in HydraulicEngineering at the university of Wisconsin:

"To engineers familiar with the variation in efficiency of the turbineat part gate, a glance at the curves obtained from the Wisconsin experimentswill be convincing as to the superiority of the overshoot wheel in respectto its adaptability to varying discharge."

"The result of the experiments show high efficiencies under a widerange of operating conditions. Reliable test of turbines have been reportedyielding as high as 89% efficiency but it is rarely that this figure isobtained in an actual installation. In the smaller plants, especially, wherean overshoot wheel would be capable of competing with a turbine, it is doubtfulwhether the turbines operate with an average efficiency higher than 70%."

"Laboratory test of a machine, when properly interpreted, undoubtedlyhave great value, but it must be borne in mind, that any test so made representsresults under the exact conditions of the test. The conditions under whichthe Wisconsin experiments were performed approached practical conditionsvery closely. The wheel tested was of a standard pattern taken from thestock of the manufacturers. The structure features are simple, and noneof these features, of the wheel itself, were changed during the tests. Theresults should, therefore, be readily duplicated in actual service, if thewheel is set properly."

The published test reports of the university of Wisconsin show the ten footdiameter Fitz Wheel above illustrated, mounted on out bronze lined bearings,yielded an efficiency of 89%, on the water wheel shaft.

Later tests of this same wheel, made under the same supervision but withthe mounting changed to our self-aligning ball bearings, showed an efficiencyof 92%. [Note this was the only water wheel efficiency testing done andreport published in this century]

A good water power is a valuable possession and the steadily increasingcost of fuel and labor are tending to make it more valuable every day. Itcosts at least seventy dollars per annum to produce one horse-power by steamby the most efficient methods. The average cost is much higher; about onehundred dollars usually for a small plant. A gasoline engine is even moreexpensive for continuous service.

This being the case, a water power developing ten horsepower is worth ninehundred to one thousand dollars a year; or the interest on an investmentof nine to ten thousand dollars.

The power developed at any water power installation depends on three factors,viz.: The volume of water in the stream, the amount of fall and the kindof water wheel used. The first two factors are usually determined by thenatural conditions and are nearly always developed to the greatest practicableextent. They fix the potential or theoretical power. The water wheel isthe medium by which the potential or possible power is converted into actualprofit-earning power.

There is a great difference in water wheels. Failure to realize this facthas caused many water power projects to result in disappointment. Afterspending perhaps, thousands of dollars on the dam, race-way, flume, excavating,etc., to develop a power, it is a very poor policy to sacrifice a largepart of the returns by putting in a wasteful, inefficient water wheel. Awater wheel of low efficiency may only develop half, or less than half,the possible power of the location. That means a sacrifice of one-half theearnings capacity of the plant. And that is just what nineteenths of theturbines and wood wheels in existence are doing for their owners. The remainingtenth are doing better than this but not one of them is giving anythinglike the actual power it should give.

A man with a valuable water power cannot afford to take an inefficient wheelas a gift. His water power is valuable just in proportion to its earningcapacity, and its earning capacity is regulated by the amount of power developed.A wasteful water wheel cuts down the value of the whole plant in proportionto the amount.

A water power plant usually represents not only the investment of a considerablesum of money in the dam, race-way, flume, tail race, etc., but also in thevalue of the factory which it operates, since that can earn but little withoutthe power. The cost of the best water wheel on earth is but a fraction ofthe value of the entire plant which depends on it. Too much care cannotbe used in the selection of a water wheel. Only the best and most efficienton the market should be considered. That is the only wise and economicalpolicy.

By repeated tests the Fitz Overshoot Water Wheel has shown that it willdevelop at least 33 1/3 more power than the best turbine made using thesame amount of water. We are well aware that some turbine builders claimfrom 80% to 85% efficiency for their wheels and pretend that this is provenby their records in the testing flume. Such claims are absurd. It is truethat a few turbines have given a little over 80% efficiency in the laboratorywhen tested at full gate, but it must be remembered that these were largewheels built regardless of expense and working under the most favorableconditions known. Even in the case of the large turbines, the practicalvalue of these tests may be seen from the fact that no two wheels of thesame size and same make would give the same efficiency, and often the samewheel, when tested at different times, would vary considerably. Small turbines,such as out wheel competes with, have never shown good results even in laboratorytest.

It is well known that conditions are much less favorable to turbines inactual use that to those in the testing flume, and that when you buy a turbinefrom any builder you don"t get near as good a wheel as the one he buildsespecially to be tested. We know it to be a fact that there is no turbinebuilt today that will develop over 65% to 70% efficiency in actual use,and the great majority fall much below this. See the extracts on the followingpages from some leading reference works in regard to this.

But it is not enough to merely consider the efficiency of a wheel with afull head of water. It is just as important to know how a wheel will actwith a diminished head or scanty supply of water. No stream of water isof the same size at all seasons and a wheel that is not adaptable to varyingconditions is useless a large part of the year. This is the point whereall turbines, despite the claims of their makers, fail absolutely, for unlessthey are run a full gate, or nearly so, they will do very little work. Thesteel overshoot is a model wheel in this regard, as in every other respect,for it will run just as economical at one-fourth gate as at full gate, whilewhen water is plentiful, it can be crowded far beyond its normal capacity.

The Fitz Wheel depends only to a small extent upon pressure for its power.It can adapt itself to a wide range of heads. This feature is especiallyvaluable where water is scarce and a large pond is used to