A water wheel is a machine for converting the energy of flowing or falling water into more useful forms of power, a process otherwise known as hydropower. In the Middle Ages, waterwheels were used as tools to power factories throughout different

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A water wheel is a machine for converting the
energy of flowing or falling water into more
useful forms of power, a process otherwise known
as hydropower. In the Middle Ages, waterwheels
were used as tools to power factories throughout
different counties. The alternatives were the
windmill and human and animal power. The most
common use of the water wheel was to mill flour
in gristmills, but other uses included foundry
work and machining, and pounding linen for use in
paper. http//en.wikipedia.org/wiki/Water_wheel
http//www.mastergardenproducts.com/waterwheelmill
house2.htm
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A vertically-mounted water wheel that is rotated
by water striking paddles or blades at the bottom
of the wheel is said to be undershot. This is
generally the least efficient, oldest type of
wheel. It has the advantage of being cheaper and
simpler to build, but is less powerful and can
only be used where the flow rate is sufficient to
provide torque. Undershot wheels gain no
advantage from head. They are most suited to
shallow streams in flat country.   The Anderson
Mill is undershot, backshot, and overshot using
two sources of water. This allows the speed of
the wheel to be controlled Undershot wheels are
also well suited to installation on floating
platforms. http//en.wikipedia.org/wiki/FileUnder
shot_water_wheel_schematic.svg
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A vertically-mounted water wheel that is rotated
by falling water striking paddles, blades or
buckets near the top of the wheel is said to be
overshot. A typical overshot wheel has the water
channeled to the wheel at the top and slightly to
one side in the direction of rotation. 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 can use all of the water flow for
power (unless there is a leak) and does not
require rapid flow. Unlike undershot wheels,
overshot wheels gain a double advantage from
gravity. Not only is the force of the flowing
water partially transferred to the wheel, the
weight of the water descending in the wheel's
buckets also imparts additional energy. The
mechanical power derived from an overshot wheel
is determined by the wheel's physical size and
the available head, so they are ideally suited to
hilly or mountainous country. http//nrgfuture.org
/Hydro.html
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The archaeological records shows that as early as
30,000 years ago, Cro-Magnon artists employed the
mortar and pestle to grind and mix the pigments
they used to create their magnificent
"cave-art."Far more efficient than the flat rock
or even the mortar and pestle was the handmill,
quern, or as it is known in the New World, the
mano and matate, which appears to have long
pre-dated the agricultural revolution (see
Figures 1 2). The handmill consists of a flat
rock, often hollowed or concave, on which the
grain, seeds, or other materials is placed, and a
grinding stone, which is rolled across the grain,
thus reducing the grain to flour. Although the
handmill is still, today, in use in many parts of
the world, approximately 2,000 years ago
humankind began to harness water-power to turn
the stones that ground its grain.
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By 200 B.C.E. water-powered grist mills began to
appear in substantial numbers in Egypt and by the
First Century C.E. waterwheels and water-powered
mills were common throughout the Mediterranean
littoral. Of course, waterwheels were employed
to do more than mill grain, by the 10th century
C.E. waterwheels were supplying power for bellows
and trip hammers (See Figure 7) and soon after
were powering wood saws and metal lathes. In the
Late Middle Ages, gristmill complexes often took
on an almost industrial character. In Figure 8 we
see the complexity of such an operation. Note the
two undershot water wheels, with accompanying
spindles and lantern gear, at the center of the
figure. The pack animals haul the grain to
scales. After being weighed and recorded by the
tally-master, the grain was fed to millstones via
the two hoppers. Note also the spare millstone.
http//www.timsmills.info/MillLinks/AncientMills.h
tm
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The miller carefully adjusted the stones so they
were just close enough to grind the grain without
touching stone on stone. The bottom stone, called
the bedstone, did not move. The top stone, called
the runner, turned as many as 125 revolutions per
minute. A pattern was carved into the millstones
so that as the grain was ground, the flour would
follow the furrows in the pattern to the outer
edges of the millstones, and then fall into the
bin surrounding the stones. The millstones wore
down through constant use, so every few weeks the
patterns had to be carved out once again. This
process was called "dressing the stone."
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A skilled miller could judge the quality of the
flour and know if the machinery needed adjustment
just by rubbing the flour between his fingers and
thumb. The ability was so well-known it led to
the folk saying "rule of thumb." After the flour
fed out from between the stones, another conveyor
belt took it back up into the attic and into a
machine called a "hopper-boy," which cooled and
dried the meal so it wouldnt stick to the
bolting screens. Next, the flour was "bolted," or
passed through a series of fine silk screens that
separated the meal into three gradesflour,
middlings (sometimes called shorts), and bran,
according to how finely it was ground.
http//www.eternal-links.net/Family_History/ngf/1
1/2/mill/Mills.html
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Roman water wheel 5 December 2002 Solving a 2,00
year old puzzle The reconstruction of the Roman
water-lifting machinery. Yet by comparing
evidence from the surviving remains with known
examples of ancient engineering - and supporting
these theories with modern engineering principles
these experts were able to reconstruct a unique
machine, which in its original form would have
been capable of raising an astonishing 72,000
litres (15,000 gallons) per 10-hour day. The
project has taken 6 months on the drawing board,
one month testing prototypes and 6 weeks under
construction. How was the drive wheel powered,
and how much water would it have lifted? The
completed machinery consists of an 8-sided oak
drive wheel with water buckets that empty into a
trough as they near the top of the chain. The 18
oak buckets are made from planks with a recessed
base to allow room for the articulated movement
of the iron chain.
http//www.museumoflondon.org.uk/English/AboutUs/N
ewsroom/Archived02/RomanWaterWheel.htm
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Ancient Water Power Designs Water Power Ancient
Roman Gravity Aqueducts (Images via ATPM,
KMKZ and IWAR) The Romans are well known for
their many colossal and ingenious works of
architecture and engineering but perhaps most of
all for their gravity-driven water-distributing
and waste-evacuating aqueducts - some of which
are still in use today. More than a marvel of
ancient plumbing, these aqueducts are also an
early example of renewable water power for mines,
forges, mills and baths.
History of Invention, Williams, 2000. Little,
Brown Book Group, UK
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History of Invention, Williams, 2000. Little,
Brown Book Group, UK
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Illustration 3. Metallurgical bellows, powered by
a horizontal waterwheel, from the Chinese work of
1313 AD.
Ancient China Waterpower was important source of
energy in ancient China civilization. One of the
most intriguing applications was for iron casting
(see illustration 3). According to an ancient
text, in 31 AD the engineer Tu Shih "invented a
water-powered reciprocator for the casting of
iron agricultural implements." Smelters and
casters were "instructed to use the rushing of
water to operate their billows." Waterpower was
also applied at an early date to grinding grain.
Large rotary mill appeared in China about the
same time as in Europe (2nd century BC). But
while for centuries Europe relied heavily on
slave- and donkey-powered mills, in China the
waterwheel was a critical power supply. Chinese
waterwheels were typically horizontal. The
vertical wheel, however, was known. It was used
to operate trip hammers for hulling rice and
crushing ore (see illustration 4). The
edge-runner mill was another commonly used
crushing device. With the latter a circular stone
on edge running around a lower millstone was used
to pulverize. The edge runner appeared in China
in the 5th century AD. Both the trip hammer and
edge runner were not used in Europe until eight
centuries later. Throughout the first 13
centuries AD, technological innovations filtered
slowly but steadily from the advanced East to the
somewhat more backward West. Carried at first
through central Asia over the 4,000-mile Silk
Route and later by sea, some innovations were
exported swiftly, while others (like waterwheel
paraphernalia) took centuries.
http//www.waterhistory.org/histories/waterwheels/
waterwheelill3.png
Illustration 4. Transformation of rotary motion
into linear motion can be achieved by having a
cam on the axle of the wheel (drawing from
Scientific American)