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                              OVERSHOT WATERWHEEL
                           A DESIGN AND CONSTRUCTION
                                 Published by
                       1600 Wilson Boulevard, Suite 500
                         Arlington, Virginia 22209 USA
                     Tel: 703-276-1800 . Fax: 703/243-1865
                              ISBN 0-86619-067-8
                   [C] 1980 Volunteers in Technical Assistance
                             OVERSHOT WATERWHEEL
    Cost Estimate
    Undershot Waterwheel
    Overshot Waterwheel
    Site Selection
    Power Output
    Materials and Tools
    Prepare the Diameter Section
    Prepare the Shrouds
    Prepare the Buckets
    Make the Wood Bearings
    Size of the Bearings
    Attach Metal or Wood Shaft to The Wheel
    Constructing Mountings and Tail Race
    Mounting the Wheel
    Mounting the Wheel--Vehicle Axle (Optional)
    Water Delivery to the Wheel
APPENDIX I. Site Analysis
APPENDIX II. Small Dam Construction
APPENDIX III. Pump Selection
APPENDIX IV. Calculating Bearing and Shaft Sizes
APPENDIX V. Decision Making Worksheet
APPENDIX VI. Record Keeping Worksheet
                            OVERSHOT WATERWHEEL
Improved use of water as a power source has potential for much
of the developing world.  There are few places where water is
not available in quantities sufficient for power generation.
Almost any flowing water--river, brook, or outlet of a lake or
pona--can be put to work and will provide a steady source of
energy.  Fluctuations in the rate of flow usually are not too
large and are spread out over time; water flow is far less
subject to quick changes in energy potential and is available
24 hours a day.
The uses of energy from water are about the same as those for
energy from the wind--electrical generation and mechanical
power.  Water-powered turbines attached to generators are used
to generate electricity; waterwheels are generally used to
power mechanical devices such as saws and machines for grinding
Development of water power can be advantageous in communities
where the cost of fossil fuels is high and access to electric
transmission lines is limited.
The cost of employing water power can be high. As with any
energy project, you must consider carefully all options.  The
potential for power generation of the water source must be
carefully matched with what it will power.   For example, if a
windmill and a waterwheel can be constructed to fill the same
end use, the windmill may well require less time and money.  On
the other hand, it may be less reliable.
Using water power requires: 1) a constant and steady flow of
water, and 2) sufficient "head" to run the waterwheel or turbine,
if such is being used.  "Head" is the distance the water
falls before hitting the machine, be it waterwheel, turbine, or
whatever.  A higher head means more potential energy.
There is a greater amount of potential energy in a larger volume
of water than in a smaller volume of water.   The concepts of
head and flow are important: some applications require a high
head and less flow; some require a low head but a greater flow.
Many water power projects require building a dam to ensure both
constant flow and sufficient head.   It is not necessary to be an
engineer to build a dam. There are many types of dams, some
quite easy to build.  But any dam causes changes in the stream
and its surroundings, so it is best to consult someone having
appropriate expertise in construction technique.
It is important to keep in mind that there can be substantial
variation in the available flow of water, even with a dam to
store the water.  This is especially true in areas with seasonal
rainfall and cyclical dry periods.   Fortunately, in most areas
these patterns are familiar.
Waterwheels have particularly high potential in areas where
fluctuations in water flow are large and speed regulation is
not practical.  In such situations, waterwheels can be used to
drive machinery which can take large fluctuations in rotation
and speed.  Waterwheels operate between 2 and 12 revolutions per
minute and usually require gearing and belting (with related
friction loss) to run most machines. (They are most useful for
slow-speed) applications, e.g., flour   mills, agricultural
machinery, and some pumping  operations.
A waterwheel, because of its rugged design, requires less care
than a water turbine.  It is self-cleaning, and therefore does
not need to be protected from debris (leaves, grass, and
Capital and labor costs can vary greatly with the way the power
is used.  For example, an undershot waterwheel in a small stream
can be fairly easy and inexpensive to build.   On the other hand,
the set-up for generating electricity with a turbine can be
complicated and costly.  However, once a water power device is
built and in operation, maintenance is simple and low in cost:
it consists mainly of lubricating the machinery and keeping the
dam in good condition.  A well built and well situated water
power installation can be expected to last for 20-25 years,
given good maintenance and barring major catastrophes.   This
long life is certainly a factor to be figured into any cost
Applications:   * water pumping.
                * Low-speed machinery applications such as
                  grist mills, oil presses, grinding
                  machines, coffee hullers, threshers, water
                  pumps, sugar cane presses, etc.
Advantages:     * Can work over a range of water flow and
                  head conditions.
                * Very simple to build and operate.
                * Virtually no maintenance required.
Considerations: * Not advisable for electrical generation or
                  high-speed machinery applications.
                * For optimum life expectancy water-resistant
                  paints are needed.
$100 to $300 (US, 1979) including materials and labor.
(*) Cost estimates serve only as a guide and will vary from
country to country.
When determining whether a project is worth the time, effort,
and expense involved, consider social, cultural, and environmental
factors as well as economic ones.   What is the purpose of
the effort? Who will benefit most? What will the consequences
be if the effort is successful? And if it fails?
Having made an informed technology choice, it is important to
keep good records. It is helpful from the beginning to keep
data on needs, site selection, resource availability,
construction progress, labor and materials costs, test
findings, etc. The information may prove an important reference
if existing plans and methods need to be altered.   It can be
helpful in pinpointing "what went wrong?" And, of course, it is
important to share data with other people.
The technologies presented in this and the other manuals in the
energy series have been tested carefully, and are actually used
in many parts of the world.  However, extensive and controlled
field tests have not been conducted for many of them, even some
of the most common ones.  Even though we know that these
technologies work well in some situations, it is important to
gather specific information on why they perform properly in one
place and not in another.
Well documented models of field activities provide important
information for the development worker.   It is obviously
important for a development worker in Colombia to have the
technical design for a machine built and used in Senegal.  But
it is even more important to have a full narrative about the
machine that provides details on materials, labor, design
changes, and so forth.  This model can provide a useful frame of
A reliable bank of such field information is now growing.  It
exists to help spread the word about these and other
technologies, lessening the dependence of the developing world
on expensive and finite energy resources.
A practical record keeping format can be found in Appendix VI.
The two most common types of waterwheels are the undershot and
the overshot versions.
The undershot waterwheel (see Figure 1) should be used with a

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head of 1.5 to 10 ft and flow rates from 10 to 100 cu ft per
second.  Wheel diameter should be three to four times the head
ana is usually between 6 and 20 ft.   Rotational speeds of the
wheel are from 2-12 revolutions per minute; smaller wheels
produce higher speeds.  The wheel dips from 1-3 ft into the
water.  Efficiency is in the range of 60-75 percent.
The overshot waterwheel (see Figure 2) is used with heads of

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10-30 ft and flow rates from 1-30 cu ft per second.   Water is
guided to the wheel through a wood or metal flume.   A gate at
the end of the flume controls the water flow to the wheel.
Wheel width can be fixed depending upon the amount of water
available and the output needed.   In addition, the width of the
waterwheel must exceed the width of the flume by about 15cm
(6") because the water expands as it leaves the flume.  The
efficiency of a well constructed overshot waterwheel can be
60-80 percent.
Overshot wheels are simple to construct, but they are large and
they require a lot of time and material--as well as a sizeable
workspace.  Before beginning construction, it is a good idea to
be sure facilities are or will be available for transporting
the wheel and lifting it into place.
Even though an overshot wheel is simple to construct and does
not require extreme care in cutting and fitting, it must be
strong and sturdy.  Its size alone makes it heavy, and in addition
to its own weight, a wheel must support the weight of the
water.  The high torque delivered by the wheel requires a strong
axle--a wooden beam or (depending on the size of the wheel) a
car or tractor axle.  Attention to these points will help prevent
problems with maintenance.
Large waterwheels may be made much like a wagon wheel--with a
rim attached to spokes.  A smaller wheel may be made of a solid
disc of wood or steel.  Construction of a wheel involves the
assembly of four basic parts: the disc or spokes of the wheel
itself, the shrouds or sides of the buckets that hold the
water, the buckets, and the mounting framework.   Other parts are
determined by the work the wheel is intended to do and may
include a drive for a pump or grinding stone or a system of
gears and pulleys for generating electricity.
Before a wheel is constructed, careful consideration should be
given to the site of the wheel and the amount of water available.
Because overshot wheels work by gravity, a relatively
small flow of water is all that is needed for operation.   Even
so, this small flow must be directed into a flume or chute.
Doing this often requires construction of a small dam.
The overshot waterwheel derives its name from the manner in
which it is activated by the water.   From a flume mounted above
the wheel, water pours into buckets attached to the edge of the
wheel and is discharged at the bottom.   An overshot wheel operates
by gravity: the water-filled buckets on the downward side
of the wheel over-balance the empty buckets on the opposite
side and keep the wheel moving slowly.
In general, overshot waterwheels are relatively efficient
mechanically and are easily maintained.   Their slow speed and
high torque make them a good choice to operate such machinery
as grist mills, coffee hullers, and certain water pumps.  They
may even be used for generating small amounts of electricity.
Electrical generators require a series of speed multiplying
devices that also multiply the problems of cost, construction,
and maintenance.
Such a wheel should be located near, but not in, a stream or
river.  If a site on dry ground is chosen, the foundation may be
constructed dry and the water led to the wheel and a tailrace
excavated (see Figure 3).  Efficiency of the wheel depends on

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efficient and practical design considerations.   The wheel must
use the weight of the water through as much of the head as
possible.  The buckets should not spill or sling water until
very near the tailwater.
The experience of the people at an isolated hospital in rural
Malawi serves to illustrate many of the questions, both technical
and cultural, that go into the development of a water
power unit.
A failed cassava crop in the area led to the substitution of a
new dietary staple--corn (maize). But the nearest mill for
grinding the corn was a 49-kilometer (30-mile) walk away.
Clearly something needed to be done to make milling facilities
more accessible to the people.
A diesel-powered mill was too expensive and too difficult to
maintain in that remote region. The river flowing past the hospital
seemed to hold the promise of a power source, but, again,
commercial water turbines proved too costly. Some kind of
waterwheel seemed to provide an appropriate choice.
Development of the water power site involved the combined
efforts of VITA and five VITA Volunteers, a missionary engineer
in another area of Malawi, and OXFAM, another international
development agency. Some data was also supplied by commercial
milling firms. Much of the labor was volunteered by local
Correspondence between and among the participants involved
choice of type of wheel, determining how to provide enough head
to develop enough power to do the job, construction of the
wheel, and selecting the proper burrs or grindstones.
Both VITA and OXFAM strongly recommended an overshot wheel for
the reasons cited earlier: ease of construction and maintenance,
reliability, and mechanical efficiency. With this comparison
as a guide, the overshot wheel was chosen.
Power to run the grain mill required a head of about 427cm (14
ft, which would accommodate a wheel nearly 361cm (12 ft)
across. The higher head necessary for the overshot wheel made
it necessary to clear away additional boulders from the river
bed, but this original investment in labor was more than
returned by the increased efficiency of the wheel.
Additional correspondence (except for a couple of visits by the
missionary engineer, the entire problem-solving process was
handled by mail!) determined the precise shape, angle, size,
and numbers of the buckets on the wheel. Also necessary was the
design of a system of pulleys to transfer the power of the
wheel to the milling operation.
As the wheel was constructed, attention was given to the grindstones.
Granite found in the area seemed ideal, but proved to
be too difficult for local stone cutters to deal with and yet
not durable enough to be worth the time. Advice was sought from
a millwright in New York and a variety of commercial milling
firms. Ultimately a small commercial mill was chosen, with continued
study going into preparing traditional stones.
In one of the last letters, hospital staff related that the
wheel and mill were in place and operating. And from experience
gained in this project they were already considering the possibility
of constructing turbines to generate electricity.
A careful analysis of the proposed site of the waterwheel is an
important early step before construction begins. Whether it is
a good idea to try to harness a stream depends on the reliability
and quantity of the flow of water, the purpose for which
power is desired, and the costs involved in the effort. It is
necessary to look at all factors carefully. Does the stream
flow all year round--even during dry seasons? How much water is
available at the driest times? What will the power do--grind
grain, generate electricity, pump water? These questions and
others must be asked.
If a stream does not include a natural waterfall of sufficient
height, a dam will have to be built to create the 'head' necessary
to run the wheel. Head is the vertical distance which the
water falls.
The site of the dam and wheel will affect the amount of head
available. Water power can be very economical when a dam can be
built into a small river with a relatively short (less than 100
ft) conduit (penstock for conducting water to the waterwheel).
Development costs can be fairly high when such a dam and
pipeline can provide a head of only 305cm (10 ft) or less.
While a dam is not required if there is enough water to cover
the intake of a pipe or channel at the head of the stream where
the dam would be placed, a dam is often necessary to direct the
water into the channel intake or to get a higher head than the
stream naturally affords. This, of course, increases expense
and time and serves as a very strong factor in determining the
suitability of one site over another.
A thorough site analysis should include collection of the
following data:
*  Minimum flow in cubic feet or cubic meters per second.
*  Maximum flow to be utilized.
*  Available head in feet or meters.
*  Site sketch with elevations, or topographic map with site
   sketched in.
*  Water condition, whether clear, muddy, sandy, etc.
*  Soil condition, the velocity of the water and the size of
   the ditch or channel for carrying it to the works depends on
   soil condition.
Measurements of stream flow should be taken during the season
of lowest flow to guarantee full power at all times. Some
investigation of the stream's history should be made to
determine if there are perhaps regular cycles of drought during
which the stream may dry up to the point of being unusable.
Appendices I and II of this manual contain detailed
instructions for measuring flow, head, etc., and for building
penstocks and dams. Consult these sections carefully for
complete directions.
The amount of water available from the water source can be
determined to assist in making the decision whether to build.
Power may be expressed in terms of horsepower or kilowatts. One
horsepower is equal to 0.7455 kilowatts; one kilowatt is about
one and a third horsepower. The gross power, or full amount
available from the water, is equal to the useful power plus the
losses inherent in any power scheme. It is usually safe to
assume that the net or useful power in small power installations
will only be half of the available gross power due to
water transmission losses and the gearing necessary to operate
*  Gross power is determined by the following formula:
   In English units:
   Gross Power (horsepower) =
     Minimum Water Flow (cu ft/sec) X Gross Head (ft)
   In Metric units:
   Gross Power (metric horsepower) =
   1,000 Flow (cu m/sec) X Head (m)
*  Net power available at the turbine shaft is:
   In English units:
   Net Power =
   Minimum Water Flow X Net Head(*) X Turbine Efficiency
   In Metric Units:
   Net Power =
    Minimum Water Flow X Net Head(*)  X Turbine Efficiency
While water pumping is an obvious use for the waterwheel, other
machinery can be adapted to use the mechanical power output of
the wheel. Almost any stationary machine which is currently
hand-powered could be run by waterwheel power. Only in the case
where the wheel and the machine are separated by long distances
should there be any significant problem.
One problem which can occur when the machine is located some
distance from the wheel is that the drive shaft of the machine
will not easily be aligned with the waterwheel shaft. Alignment
difficulties can be overcome simply and cheaply with old automobile
rear axle assemblies, with the gears welded or jammed to
give constant speed on both sides.
If the water supply to the wheel fluctuates, the speed of the
wheel will vary. These speed variations are small and will
generally not be of any consequence. If the variable speeds
create problems, either a special constant velocity joint (as
from the front wheel drive automobile) or two ordinary U joints
must be used, each to compensate for the different motion of
the other.
(*) The net head is obtained by deducting the energy losses from
the gross head. These losses are discussed in Appendix I. When
it is not known, a good assumption for waterwheel efficiency is
60 percent.
Flexible shafts are commercially available but are of limited
torque-carrying capacity.
Solid shafts can transmit torque over considerable distance but
require bearings for support and are expensive.
Generation of electricity is a possibility which will probably
spring to the minds of most people reading this manual. There
are waterwheel-driven electric generators in operation today,
but the number of failed attempts testifies to the fact that it
is not a simple, inexpensive project.
The need for power should be documented, and the measurements
taken for the site analysis should be recorded. Costs of construction
and operation can be compared to the benefit gained
from the device to determine its real worth. (In making comparisons,
don't forget to include the pond or lake created by the
dam--it can be used to water livestock, raise fish, or irrigate
A simple, relatively economical 112cm (5 ft) wheel for pumping
water can be made out of a disc of heavy plywood to which the
buckets and shrouds are attached. Plywood is chosen because it
is easy to use and relatively accessible; however, it does
require special treatment to avoid deterioration and, in some
places, may be quite expensive. The shaft of the wheel can be
made either from metal or wood: the rear axle from an automobile
may be used but, in most cases, axles are available only
at great expense.
Lumber for shrouds, buckets, and rim reinforcement may be of
almost any type available; hardwood is preferable. Ordinary
wood saws, drills, and hammer are used in construction. Welding
equipment is convenient if an automobile rear axle is being
used. Materials for the dam and mounting structure should be
chosen from whatever is at hand, based on the guidelines in
this manual. While materials for the wheel may vary with what
is available, they should include:
*  2cm thick plywood(*)--at least 112cm square.
*  6mm thick plywood(*)--122cm X 244cm sheet.
*  703cm total length of 3cm X 6cm boards to reinforce the edge
   of the disc.
*  703cm total length of 2cm X 30cm boards for the shrouds.
*  438cm total length of 2cm X 30cm boards for buckets.
*  703cm total length of 6mm X 20cm plywood* to reinforce the
   outside of the shrouds.
*  110cm long 5cm dia solid steel shaft or 9cm sq hardwood
   shaft. (Automobile rear axle is optional.)
*  5cm dia steel hubs (2) for steel shaft.
*  10 liters asphalt patching compound (or tar).
*  Timbers and lumber for support structure as needed, nails,
   tin cans, bolts.
(*) Marine-grade plywood is preferred; waterproofed exterior-grade
can be used.
*  Protractor
*  Wood saw
*  Wood drill/bits
*  Hammer
*  Welding equipment (optional)
*  Make a disc out of the 2cm thick plywood 112cm in dia. This
   is done using the meter stick.
*  Nail one end of the ruler to the center of the plywood
*  Measure 56cm from the nail and attach a pencil to the ruler.
*  Scribe a circle and cut out disc with a wood saw (see Figure 4

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*  Divide the circle in half and then into quarters using a
   pencil and straight edge.
*  Divide each quarter into thirds (30[degrees] intervals on protractor).
   The finished disc should look like Figure 5. The

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   twelve reference lines will be used to guide the positioning
   of the buckets.
*  Take 25-40cm lengths of 2cm X 3cm X 6cm lumber and nail them
   around the outside diameter of the wood disc on both sides
   so that the outer edge projects slightly beyond the rim of
   the disc (see Figure 6).

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*  Cut the 6mm thick X 122cm X 244cm plywood sheets into six
   strips 40.6cm wide X 122cm long.
*  Bend and nail three of the strips around the disc so that
   they overhang equally on both sides.
*  Bend and nail a second layer over the first, staggering the
   joints so as to give added strength and tightness (see
   Figure 7). These layers form what is called the sole plate

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   or backside of the buckets which will be attached later.
*  Cut the shrouds, or sides, of the buckets from 2cm X 30cm
   wide boards. Nail one end of the meter stick to a piece of
   lumber. Measure 57.2cm from this nail. Drill 6mm hole and
   attach a pencil.
*  Measure 20.5cm from this
   pencil, drill 6mm hole and
   attach another pencil. This
   becomes a compass for making
   the shrouds (see Figure 8).

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*  Take 2cm X 30cm boards and
   scribe the outline of the
   shroud on, the wood. Cut out
   enough of the shrouds to fit
   around both sides of the disc.
   Shroud edges will have to be
   planed to fit.
*  Nail the shroud pieces flush to the edge of the sole plate
   from the back side of the sole plate.
*  Use the "compass" trace and cut out a second set of shrouds,
   or shroud covers, from 6mm thick plywood.
*  Nail the plywood shroud covers on the outside of the first
   shrouds, with the joints overlapped (see Figure 9). Be sure

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   that the bottom edge of this second set of shrouds is flush
   with the bottom edge of the first layer of the sole plate.
*  Fill in any cracks and seams
   with the asphalt patching
   compound or waterproof sealer.
   The finished wheel will look
   something like a cable spool
   (see Figure 10).

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*  Make the front sides of the twelve (12) buckets from
   hardwood boards 2cm X 30cm. The width of the front board
   will be 36.5cm.
*  Make the bottom sections of the buckets from hardwood boards
   2cm X 8cm. The length of each board will be 36.5cm.
*  Cut the bottom of each 30cm section at a 24[degrees] angle from the
   horizontal and the top edge at a 45[degrees] angle from the horizontal
   as shown in Figure 11 before putting the two sections

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*  Nail the buckets together (see Figure 12). Each bucket

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   should have an inside angle of 114[degrees].
Place each bucket between the shrouds. Using the reference
lines scribed on the disc earlier, match one bucket to each
line as shown in Figure 13. The buckets can then be nailed

owd13x27.gif (600x600)

in place.
  * Fill in all cracks with the asphalt patching compound.
Bearings, for attaching the shaft to the wheel, will last
longer if they are made from the hardest wood available locally.
Generally, hardwoods are heavy and difficult to work. A
local wood-craftsman should be able to provide information on
the hardest woods. If there is doubt concerning the hardness or
the self-lubricating quality of the wood that is going to be
used in the bearings, thoroughly soaking the wood with oil will
give longer life to the bearings.
Some advantages in using oil-soaked bearings are that they:
*  Can be made from locally available materials.
*  Can be made by local people with wood-working skills.
*  Are easily assembled.
*  Do not require further lubrication or maintenance in most
*  Are easily inspected and adjusted for wear.
*  Can be repaired or replaced.
*  Can provide a temporary solution to the repair of a more
   sophisticated production bearing.
The oiliness of the wood is important if the bearing is not
going to be lubricated. Woods having good self-lubricating properties
often are those which:
*  Are easily polished.
*  Do not react with acids (e.g., teak).
*  Are difficult to impregnate with preservatives.
*  Cannot be glued easily.
Usually the hardest wood is found in the main trunk just below
the first branch. Wood freshly cut should be allowed to dry for
two to three months to reduce moisture content. High moisture
content will result in a reduction in hardness and will cause
greater wear.
The length of the wood bearings should be at least twice the
shaft diameter. For example, for the 5cm dia axle or shaft of
the waterwheel presented here, the bearing should be at least
10cm long. The thickness of the bearing material at any point
should be at least the shaft diameter (i.e., for a 5cm dia
shaft a block of wood 15cm X 15cm X 10cm long should be used).
Split block bearings (see Figure 14) should be used for the

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waterwheel because it is a heavy piece of equipment and can
cause a great deal of wear. These bearings are simple to make
and replace.
The following steps outline the construction of a split-block
*  Saw timber into an oblong block slightly larger than the
   finished bearing to allow for shrinkage.
*  Bore a hole through the wood block the size of the axle/
   shaft diameter.
*  Cut block in half and clamp firmly together for drilling.
*  Drill four 13mm or larger holes for attaching bearing to
   bearing foundation. After drilling, the two halves should be
   tied together to keep them in pairs.
*  Impregnate the blocks with oil.
*  Use an old 20-liter (5-gal) drum filled two-thirds full with
   used engine oil or vegetable oil.
*  Place wood blocks in oil and keep them submerged by placing
   a brick on top (see Figure 15).

owd15x30.gif (486x486)

*  Heat the oil until the moisture
   in the wood is turned
   into steam--this will give
   the oil an appearance of
   boiling rapidly.
*  Maintain the heat until
   there are only single
   streams of small pin-sized
   bubbles rising to the oil's
   surface (see Figure 16).

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   This may take 30 minutes to
   2 hours, or longer, depending
   on the moisture content
   of the wood.
   Soon after heating the bearing
   blocks in oil, many surface
   bubbles one-inch in
   diameter, made from a multitude
   of smaller bubbles, will
   appear on the surface.
   As the moisture content of
   blocks is reduced, the surface
   bubbles will become
   smaller in size.
   When the surface bubbles are
   formed from single streams of
   pin-sized bubbles, stop
*  Remove the heat source and leave the blocks in the oil to
   cool overnight. During this time the wood will absorb the
*  Remove wood blocks from the oil, reclamp and rebore the
    holes as necessary to compensate for shrinkage that may have
   taken place. The bearings are now ready to be used.
(Calculations for shaft and bearing sizes for larger waterwheels
are provided in Appendix IV.)
Metal Shaft
*  Drill or cut out a 5cm dia round hole in the center of the
*  Attach 5cm dia steel hubs as shown in Figure 17 using four

owd17x32.gif (486x486)

   20mm X 15cm long bolts.
*  Insert 110cm long metal shaft through the wheel center so
   that the shaft extends 30cm from one edge of the shroud and
   38.2cm from the other edge (see Figure 18).

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*  Weld the shaft to the hub
   assembly on both sides as
   shown in Figure 19.

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Wood Shaft
*  Drill and carefully cut out a 9cm square hole in the center
   of the wheel.
*  Measure 49cm from one end of the 110-cm long wood shaft and
   mark with a pencil. Measure 59cm from other end of the shaft
   and do the same. Turn the shaft over and repeat the procedure.
   There should be 2cm between the two marks.
*  Cut grooves 3cm wide X 1cm deep on both sides of the shaft
   as shown below in Figure 20.

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*  Cut the 9cm shaft to 5cm dia only at the bearing (see Figure 21).

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   This step will take some time. A tin can 5cm in
   diam or the bearing itself can be used to gauge the cutting
   process. The finished shaft must be sanded and made as round
   and smooth as possible to prevent excessive or premature
   wear on the bearing.
*  Insert wood shaft through wheel center so that the grooves
   show on either side of the wheel disc.
*  Fit 3cm X 6cm X 15cm boards into the grooves so that they
   fit tightly. Tack each board to disc using nails to ensure
   a tight fit in the groove.
*  Drill two 20mm dia holes through each 3cm X 6cm boards and
   disc. Insert 20mm dia X 10cm long bolts with washer through
   the disc and attach with washer and nut (see Figure 22 and Figure 23).

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   Remove nails.
*  The wheel is now ready to be mounted.
Stone or concrete pillars make the best mounting for the
waterwheel. Heavy wood pilings or timber also have been used
successfully. The primary determinant is, of course, local
availability. Foundations should rest on a solid base--firm
gravel or bedrock if possible to avoid settling. Large area
footings will also help, and will prevent damage from stream
erosion. If one end of the shaft is supported at the power
plant building, this support should be as solid as the outer
Provision should be made for periodic adjustment in the alignment
of the bearings in case one of the supports should settle
or slide. Wood blocks can be used to mount the bearings, and
these can be changed to adjust for any differences in elevation
or placement. It is important that bearings and wheel shift be
kept in perfect alignment at all times.
If the discharge or tailwater is not immediately removed from
the vicinity of the wheel, the water will tend to back up on
the wheel causing a serious loss of power. However, the drop
necessary to remove this water should be kept at a minimum in
order to lose as little as possible of the total available
The distance between the bottom of the wheel and the tailrace
should be 20-30cm (4-6"). The tailrace or discharge channel
should be smooth and evenly shaped down the stream bed below
the wheel (see Figure 24).

owd24x35.gif (486x600)

Attach the bearings to the shaft and lift the wheel onto
mounting pillars. Align the wheel vertically and horizontally
through the use of wood blocks under the bearings. Once
alignment has been done, drill through four holes in the
bearing into the wood shim and mounting pillar.
Attach the bearings to the pillars using lag/anchor bolts in
the case of concrete pillars or lag/anchor screws 13mm dia X
20cm long if wood pilings are used.
In mounting the shaft in the bearings, carefully avoid damage
to the bearings and shaft. The shaft and bearings must be
accurately aligned and solidly secured in place before the
chute is assembled and located.
The wheel must be balanced in order to run smoothly, without
uneven wear, or excess strain on the supports. When the wheel
is secured on the mountings, it should turn easily and come to
a smooth, even stop. If it is unbalanced, it will swing back
and forth for a time before stopping. If this should occur, add
a small weight (i.e., several nails or a bolt), at the top of
the wheel when it is stopped. With care, enough weight can be
added to balance the wheel perfectly.
Take a rear axle from a full-sized car and fix the differential
gears so the two axles turn as one unit. You can jam these
gears by welding so they don't operate. Cut off one axle and
the axle housing to get rid of the brake assembly if you wish.
The other axle should be cleaned of brake parts to expose the
hub and flange. You may have to knock the bolts out and get rid
of the brake drum. The wooden disc of the waterwheel needs to
have a hole made in its center to fit the car wheel hub
closely. Also it should be drilled to match the old bolt holes
and bolts installed with washers under the nuts.
Before mounting the wheel in place, have a base plate welded to
the axle housing (see Figure 25). It should be on what is to be

owd25x37.gif (600x600)

the underside, with two holes for 13mm lag screws. Make some
kind of anchor to hold the opposite housing in place.
For highest efficiency, water must be delivered to the wheel
from a chute placed as close to the wheel as possible, and
arranged so that the water falls into the buckets just after
they reach upper dead center (see Figure 26). The relative

owd26x38.gif (600x600)

speed of the buckets and the water are very important.
The speed of the wheel will be reduced as the load it is
driving increases. When large   changes take place in the load,
it is necessary to change the amount of water or the velocity
of its approach to the wheel. This is done by a control gate
located near the wheel, which can be raised or lowered easily
and fixed at any position to give moderately accurate
The delivery chute should run directly from the control gate to
the waterwheel, and be as short as construction will permit
(30cm-91cm long is best). A little slope is necessary to
maintain the water velocity (1% or 30cm in every 3000cm will be
Flat-bottomed chutes are preferable. Even when water is
delivered through a pipe, this should terminate in a control
box and delivery made to the wheel through an open,
flat-bottomed chute (see Figure 27). The tip of the chute

owd27x39.gif (540x540)

should be perfectly straight and level, and lined with sheet
metal to prevent wear.
The chute should not be as wide as the waterwheel. This allows
air to escape at the ends of the wheel as water enters the
buckets. The width of the chute is usually 10-15cm (4-6")
narrower than the width of the wheel. (In this case where the
bucket width is 36.5cm the chute width will be 22-26cm.)
All plywood parts must be waterproofed to keep them from
deteriorating. Other wood parts may be painted or varnished for
a protective coating. This helps extend the life of the wheel.
wheel. Periodic repainting may be needed. Except for the
plywood portions, the decision to paint can be made on purely
economic grounds. If a very durable wood has been used
initially, painting is a luxury. If a somewhat less durable
species is used, painting is probably cheaper and easier than
early replacement or repair of the wheel.
The only major maintenance problem is in bearing wear. Generous
allowances have been made in bearing size but the bearings will
still wear. When worn, the two halves can be interchanged;
after further wear, the life of the bearing can be extended by
planing off a small amount of wood from the matching faces.
This will drop the wheel from its original position. Inserting
wood or shimming under the bearing block with metal plates will
compensate for this. Bearing replacement, when the block is
completely worn through, is a simple matter.
Generally speaking, the bearing should be lubricated as
needed. Oils/grease/vegetable oils applied periodically in
small amounts will slow the wear rate.
CATASTROPHE--A great and sudden disaster of calamity.
CYCLICAL DRY PERIODS--A periodically repeated sequence of
        environmental conditions where there is a lack of
        rainfall or water supply.
DIA (DIAMETER)--A straight line passing through the center of a
        circle and meeting at each end of the circumference.
EMBED--To fix firmly in a surrounding mass.
Head--Measurement of the difference in depth of a liquid at two
        given points (see Appendix I).
FLUME--A channel or chute for directing the flow of water.
FLUCTUATIONS--Irregular variations or instability of a regular
GRAVITY--The force of attraction that causes terrestial bodies
        to tend to fall toward the center of the earth.
RACK AND PINION--A device to

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       convert rotary motion to
       linear motion.
SHROUD--A device that covers, conceals, or protects something.
SLUICE--A man-made water channel with a valve or gate to
        regulate the flow.
SPROCKETS--Any of various toothlike projections arranged on a
        wheel rim to engage the links of a chain.
TELESCOPIC--Capable of being made longer or shorter by the
        sliding of overlapping tubular sections.
TOPOGRAPHIC MAP--A map showing the configuration of a place or
        region, usually by the use of contour lines.
Cloudburst Press Ltd. Cloudburst manual, 1973. Cloudburst Press
        Ltd., Mayne Island, British Columbia, VON 2JO Canada.
        This manual, written by "homesteaders" in the Pacific
        Norethwest, has about 30 pages dealing with various
        aspects of water power.  It covers measuring potential
        power, dams, and designs and construction of waterwheels.
        Highly readable and eminently practical, it is
        written by and for "do-it-yourselfers" working with
        limited resources.  Also has excellent illustrations.
Hamm, Hans W. Low Cost Develoment of Small Water Power Sites,
        1967. VITA, 3706 Rhode Island Avenue, Mount Rainier,
        Maryland 20822 USA. Written expressly to be used in
        developing areas, this manual contains basic information
        on measuring water power potential, building small
        dams, different types of turbines and waterwheels, and
        several necessary matehmatical tables.  Also has some
        information on manufactured turbines available.  A very
        useful book.
Monson, O.W., and Hill, Armin J. Overshot and Current Water
        Wheels, January 1942. Bulletin 398, Montana State
        College Agricultural and Experimental Station, Bozeman,
        Montana, USA.  Written for the use of farmers and ranchers,
        this bulletin tells how to build "homemade" waterwheels
        from wood and scrap metal, as the emphasis is on
        simplicity and low cost.  A good guide for building and
        installing overshot and undershot waterwheels, it is
        profusely illustrated and contains many practical hints
        for consideration.
Ovens, William G. A Design Manual for Waterwheels, 1975. VITA,
        3706 Rhode Island Avenue, Mount Rainier, Maryland 20822
        USA.   The basic manual for waterwheel design and
        construction.  Includes both theoretical and practical
        considerations, and is written to be used by people
        with a limited technical understanding.  Also has a
        section on waterwheel applications as well as 16 highly
        useful tables and several schematic diagrams.
1 Mile                 = 1760 Yards                  = 5280 Feet
1 Kilometer            = 1000 Meters                 = 0.6214 Mile
1 Mile                 = 1.607 Kilometers
1 Foot                 = 0.3048 Meter
1 Meter                = 3.2808 Feet                 = 39.37 Inches
I Inch                 = 2.54 Centimeters
1 Centimeter           = 0.3937 Inches
1 Square Mile          = 640 Acres                   = 2.5899 Square Kilometers
1 Square Kilometer     = 1,000,000 Square Meters     = 0.3861 Square Mile
1 Acre                 = 43,560 Square Feet
1 Square Foot          = 144 Square Inches           = 0.0929 Square Meter
1 Square Inch          = 6.452 Square Centimeters
1 Square Meter         = 10.764 Square Feet
1 Square Centimeter    = 0.155 Square Inch
1.0 Cubic Foot         = 1728 Cubic Inches           = 7.48 US Gallons
1.0 British Imperial
     Gallon             = 1.2 US Gallons
1.0 Cubic Meter        = 35.314 Cubic Feet           = 264.2 US Gallons
1.0 Liter              = 1000 Cubic Centimeters      = 0.2642 US Gallons
1.0 Metric Ton         = 1000 Kilograms              = 2204.6 Pounds
1.0 Kilogram           = 1000 Grams                  = 2.2046 Pounds
1.0 Short Ton          = 2000 Pounds
1.0 Pound per square inch               = 144 Pound per square foot
1.0 Pound per square inch               = 27.7 Inches of water*
1.0 Pound per square inch               = 2.31 Feet of water*
1.0 Pound per square inch               = 2.042 Inches of mercury*
1.0 Atmosphere                          = 14.7 Pounds per square inch (PSI)
1.0 Atmosphere                          = 33.95 Feet of water*
1.0 Foot of water = 0.433 PSI           = 62.355 Pounds per square foot
1.0 Kilogram per square centimeter      = 14.223 Pounds per square inch
1.0 Pound per square inch               = 0.0703 Kilogram per square
1.0 Horsepower (English)                = 746 Watt = 0.746 Kilowatt (KW)
1.0 Horsepower (English)                = 550 Foot pounds per second
1.0 Horsepower (English)                = 33,000 Foot pounds per minute
1.0 Kilowatt (KW) = 1000 Watt           = 1.34 Horsepoer (HP) English
1.0 Horsepower (English)                = 1.0139 Metric horsepower
1.0 Metric horsepower                   = 75 Meter X Kilogram/Second
1.0 Metric horsepower                   = 0.736 Kilowatt  = 736 Watt
(*) At 62 degrees Fahrenheit (16.6 degrees Celsius).
                                  APPENDIX I
                                 SITE ANALYSIS
This Appendix provides a guide to making the necessary calculations
for a detailed site analysis.
                                  Data Sheet
                             Measuring Gross Head
                                Measuring Flow
                            Measuring Head Losses
                                  DATA SHEET
1.  Minimum flow of water available in cubic feet
    per second (or cubic meters per second).               -----
2.  Maximum flow of water available in cubic feet
    per second (or cubic meters per second).               -----
3.  Head or fall of water in feet (or meters).             -----
4.  Length of pipe line in feet (or meters) needed
    to get the required head.                              -----
5.  Describe water condition (clear, muddy, sandy,
    acid).                                                  -----
6.  Describe soil condition (see Table 2).                 -----
7.  Minimum tailwater elevation in feet (or meters).       -----
8.  Approximate area of pond above dam in acres (or
    square kilometers).                                    -----
9.  Approximate depth of the pond in feet (or
    meters).                                                -----
10. Distance from power plant to where electricity
    will be used in feet (or meters).                      -----
11. Approximate distance from dam to power plant.           -----
12. Minimum air temperature.                                -----
13. Maximum air temperature.                                -----  
14. Estimate power to be used.                              -----
The following questions cover information which, although not
necessary in starting to plan a water power site, will usually
be needed later.  If it can possibly be given early in the project,
this will save time later.
  1. Give the type, power and speed of the machinery to be
     driven and indicate whether direct, belt, or gear drive is
     desired or acceptable.
  2. For electric current, indicate whether direct current is
     acceptable or alternating current is required.  Give the
     desired voltage, number of phases and frequency.
  3. Say whether manual flow regulation can be used (with DC
     and very small AC plants) or if regulation by an automatic
     governor is needed.
                             MEASURING GROSS HEAD
Method No. 1
1. Equipment <see figure 1>

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   a. Surveyor's leveling instrument--consists of a spirit
      level fastened parallel to a telescopic sight.
   b. Scale--use wooden board approximately 12 ft in length.
2. Procedure <see figure 2>

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   a. Surveyor's level on a tripod is placed downstream from
      the power reservoir dam on which the headwater level is
   b. After taking a reading, the level is turned 180[degrees] in a
      horizontal circle.  The scale is placed downstream from it
      at a suitable distance and a second reading is taken.
      This process is repeated until the tailwater level is
Method No. 2
This method is fully reliable, but is more tedious than Method
No. 1 and need only be used when a surveyor's level is not
1. Equipment <see figure 3>

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   a. Scale
   b. Board and wooden plug
   c. Ordinary carpenter's level
2. Procedure <see figure 4>

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   a. Place board horizontally at headwater level and place
      level on top of it for accurate leveling. At the downstream
      end of the horizontal board, the distance to a
      wooden peg set into the ground is measured with a scale.
   b. The process is repeated step by step until the tailwater
      level is reached.
                                MEASURING FLOW
Flow measurements should take place at the season of lowest
flow in order to guarantee full power at all times. Investigate
the stream's flow history to determine the level of flow at
both maximum and minimum. Often planners overlook the fact that
the flow in one stream may be reduced below the minimum level
required. Other streams or sources of power would then offer a
better solution.
Method No. 1
For streams with a capacity of less than one cubic foot per
second, build a temporary dam in the stream, or use a "swimming
hole" created by a natural dam. Channel the water into a pipe
and catch it in a bucket of known capacity. Determine the
stream flow by measuring the time it takes to fill the bucket.
   Stream flow (cubic ft/sec) = Volume of bucket (cubic ft)
                                   Filling time (seconds)
Method No. 2
For streams with a capacity of more than 1 cu ft per second,
the weir method can be used. The weir is made from boards,
logs, or scrap lumber. Cut a rectangular opening in the
center. Seal the seams of the boards and the sides built into
the banks with clay or sod to prevent leakage. Saw the edges of
the opening on a slant to produce sharp edges ont he upstream
side. A small pond is formed upstream from the weir. When there
is no leakage and all water is flowing through the weir
opening, (1) place a board across the stream and (2) place
another narrow board at right angles to the first, as shown below.

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Use a carpenter's level to be sure the second board is
Measure the depth of the water above the bottom edge of the
weir with the help of a stick on which a scale has been
marked. <see figure 5> Determine the flow from Table 1 on page 56.

owdd6x55.gif (393x393)

                                   Table I
                        FLOW VALUE (Cubic Feet/Second)
                                           Weir Width
Overflow Height   3 feet   4 feet    5 feet   6 feet    7 feet   8 feet   9 feet
   1.0   inch       0.24     0.32      0.40     0.48     0.56      0.64     0.72
   2.0   inches     0.67     0.89      1.06     1.34     1.56      1.80     2.00
   4.0   inches     1.90     2.50      3.20     3.80     4.50      5.00     5.70
   6.0   inches     3.50     4.70      5.90     7.00     8.20      9.40    10.50
   8.0   inches     5.40     7.30      9.00    10.80    12.40     14.60    16.20
  10.0   inches     7.60    10.00     12.70    15.20    17.70     20.00    22.80
  12.0   inches    10.00    13.30     16.70    20.00    23.30     26.60    30.00
Method No. 3
The float method is used for larger streams. <see figure 6> Although it is not

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as accurate as the previous two methods, it is adequate for
practical purposes. Choose a point in the stream where the bed
is smooth and the cross section is fairly uniform for a length
of at least 30 ft. Measure water velocity by throwing pieces of
wood into the water and measuring the time of travel between
two fixed points, 30 ft or more apart. Erect posts on each bank
at these points. Connect the two upstream posts by a level wire
rope (use a carpenter's level). Follow the same procedure with
the downstream posts. Divide the stream into equal sections
along the wires and measure the water depth for each section.
In this way, the cross-sectional area of the stream is determined.
use the following formula to calculate the flow:
  Stream Flow (cu ft/sec) = Average cross-sectional flow area
                            (sq ft) X velocity (ft/sec)
                             MEASURING HEAD LOSSES
"Net Power" is a function of the "Net Head." The "Net Head" is
the "Gross Head" less the "Head Losses." The illustration below
shows a typical small water power installation. The head losses
are the open-channel losses plus the friction loss from flow
through the penstock. <see figure 7>

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           1.    River
           2.    Dam with Spillway
           3.    Intake to Headrace
           4.    Headrace
           5.    Intake to Turbine Penstock
           6.    Trashrack
           7.    Overflow of Headrace
           8.    Penstock
           9.    Turbine Inlet Valve
           10.   Water Turbine
           11.   Electric Generator
           12.   Tailrace
Open Channel Bead Losses
The headrace and the tailrace in the illustration above are
open channels for transporting water at low velocities. The
walls of channels made of timber, masonry, concrete, or rock,
should be perpendicular. Design them so that the water level
height is one-half of the width. Earth walls should be built at
a 45[degrees] angle. Design them so that the water level height is
one-half of the channel width at the bottom. At the water level
the width is twice that of the bottom. <see figure 8>

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The head loss in open channels is given in the nomograph. The
friction effect of the material of construction is called "N".
Various values of "N" and the maximum water velocity, below
which the walls of a channel will not erode are given.
                                   TABLE II
                              Maximum Allowable
                              Water Velocity
Material of Channel Wall       (feet/second)             Value of "n"
Fine grained sand                    0.6                     0.030
Course sand                          1.2                     0.030
Small stones                         2.4                     0.030
Coarse stones                        4.0                    0.030
Rock                                 25.0      (Smooth)      0.033  (Jagged) 0.045
Concrete with sandy water            10.0                   0.016
Concrete with clean water            20.0                   0.016
Sandy loam, 40% clay                  1.8                    0.030
Loamy soil, 65% clay                  3.0                    0.030
Clay loam, 85% clay                   4.8                    0.030
Soil loam, 95% clay                   6.2                    0.030
100% clay                             7.3                    0.030
Wood                                                        0.015
Earth bottom with rubble sides                              0.033
The hydraulic radius is equal to a quarter of the channel
width, except for earth-walled channels where it is 0.31 times
the width at the bottom.
To use the nomograph, a straight line is drawn from the value
of "n" through the flow velocity to the reference line. The
point on the reference line is connected to the hydraulic
radius and this line is extended to the head-loss scale which
also determines the required slope of the channel.
Using a Nomograph
After carefully determining the water power site capabilities
in terms of water flow and head, the nomograph is used to

ngraph1.gif (600x600)

*  The width/depth of the channel needed to bring the water to
   the spot/location of the water turbine.
*  The amount of head lost in doing this.
To use the graph, draw a straight line from the value of "n"
through the flow velocity through the reference line tending to
the hydraulic radius scale. The hydraulic radius is one-quarter
(0.25) or (0.31) the width of the channel that needs to be
built. In the case where "n" is 0.030, for example, and water
flow is 1.5 cubic feet/second, the hydraulic radius is 0.5 feet
or 6 inches. If you are building a timber, concrete, masonry,
or rock channel, the total width of the channel would be 6
inches times 0.25, or 2 feet with a depth of at least 1 foot.
If the channel is made of earth, the bottom width of the channel
would be 6 times 0.31, or 19.5 inches, with a depth of at
least 9.75 inches and top width of 39 inches.
Suppose, however, that water flow is 4 cubic feet/second. Using
the graph, <see graph> the optimum hydraulic radius would be approximately

ngraph2.gif (600x600)

2 feet--or for a wood channel, a width of 8 feet. Building a
wood channel of this dimension would be prohibitively
However, a smaller channel can be built by sacrificing some
water head. For example, you could build a channel with a
hydraulic radius of 0.5 feet or 6 inches. To determine the
amount of head that will be lost, draw a straight line from the
value of "n" through the flow velocity of 4 [feet.sup.3]/second to the
reference line. Now draw a straight line from the hydraulic
radius scale of 0.5 feet through the point on the reference
line extending this to the head-loss scale which will determine
the slope of the channel. In this case about 10 feet of head
will be lost per thousand feet of channel. If the channel is
100 feet long, the loss would only be 1.0 feet--if 50 feet
long, 0.5 feet, and so forth.
Pipe Bead Loss and Penstock Intake
The trashrack consists of a number of vertical bars welded to
an angle iron at the top and a bar at the bottom (see Figure below).

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The vertical bars must be spaced so that the teeth of a
rake can penetrate the rack for removing leaves, grass, and
trash which might clog up the intake. Such a trashrack can easily
be manufactured in the field or in a small welding shop.
Downstream from the trashrack, a slot is provided in the concrete
into which a timber gate can be inserted for shutting off
the flow of water to the turbine.
The penstock can be constructed from commercial pipe. The pipe
must be large enough to keep the head loss small. The required
pipe size is determined from the nomograph. A straight line

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drawn through the water velocity and flow rate scales gives the
required pipe size and pipe head loss. Head loss is given for a
100-foot pipe length. For longer or shorter penstocks, the
actual head loss is the head loss from the chart multiplied by
the actual length divided by 100. If commercial pipe is too
expensive, it is possible to make pipe from native material;
for example, concrete and ceramic pipe, or hollowed logs. The
choice of pipe material and the method of making the pipe
depend on the cost and availability of labor and the availability
of material.
                                 APPENDIX II
                            SMALL DAM CONSTRUCTION
This appendix is not designed to be exhaustive; it is meant to
provide background and perspective for thinking about and
planning dam efforts. While dam construction projects can range
from the simple to the complex, it is always best to consult an
expert, or even several; for example, engineers for their construction
savvy and an environmentalist or concerned agriculturalist
for a view of the impact of damming.
                               Introduction to:
                                  Earth Dams

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                                  Crib Dams

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                           Concrete and Masonry Dams
                                  EARTH DAMS
An earth dam may be desirable where concrete is expensive and
timber scarce. It must be provided with a separate spillway of
sufficient size to carry off excess water because water can
never be allowed to flow ovewr the crest of an earth dam. Still
water is held satisfactorily by earth but moving water is not.
The earth will be worn away and the dam destroyed.
The spillway must be lined with boards or concrete to prevent
seepage and erosion. The crest of the dam may be just wide
enough for a footpath or may be wide enough for a roadway, with
a bridge placed across the spillway.
The big problem in earth-dam construction is in places where
the dam rests on solid rock. It is hard to keep the water from
seeping between the dam and the earth and finally undermining
the dam.
One way of preventing seepage is to blast and clean out a
series of ditches, or keys, in the rock, with each ditch about
a foot deep and two feet wide extending under the length of the
dam. Each ditch should be filled with three or four inches of
wet clay compacted by stamping it. More layers of wet clay can
then be added and the compacting process repeated each time
until the clay is several inches higher than bedrock.
The upstream half of the dam should be of clay or heavy clay
soil, which compacts well and is impervious to water. The
downstream side should consist of lighter and more porous soil
which drains quickly and thus makes the dam more stable than if
it were made entirely of clay.
                                  CRIB DAMS
The crib dam is very economical where lumber is easily
available:  it requires only rough tree trunks, cut planking,
and stones.  Four- to six-inch tree trunks are placed 2-3 feet
apart and spiked to others placed across them at right angles.
Stones fill the spaces between timbers.   The upstream side
(face) of the dam, and sometimes the downstream side, is
covered with planks.  The face is sealed with clay to prevent
leakage.  Downstream planks are used as an apron to guide the
water which overflows the dam back into the stream bed.   The dam
itself serves as a spillway in this case.   The water coming over
the apron falls rapidly.  Prevent erosion by lining the bed
below with stones.  The apron consists of a series of steps for
slowing the water gradually.
Crib dams must be embedded well into the embankments and packed
with impervious material such as clay or heavy earth and stones
in order to anchor them and to prevent leakage.   At the heel, as
well as at the toe of crib dams, longitudinal rows of planks
are driven into the stream bed.   These are priming planks which
prevent water from seeping under the dam, and they also anchor
If the dam rests on rock, priming planks cannot and need not be
driven; but where the dam does not rest on rock they make it
more stable and watertight.  These priming planks should be
driven as deep as possible and then spiked to the timber of the
crib dam.
The lower ends of the priming planks are pointed as shown in
the Figure on page 69 and must be placed one after the other as

figx69.gif (600x600)

shown.  Thus each successive plank is forced, by the act of
driving it closer against the preceding plank, resulting in a
solid wall.  Any rough lumber may be used.  Chestnut and oak are
considered to be the best material.   The lumber must be free
from sap, and its size should be approximately 2" X 6".
In order to drive the priming planks, considerable force may be
required.  A simple pile driver will serve the purpose.  The
Figure below shows an excellent example of a pile driver.
                          CONCRETE AND MASONRY DAMS
Concrete and masonry dams more than 12 feet high should not be
built without the advice of an engineer with experience in this
field.  Dams require knowledge of the soil condition and bearing
capacity as well as of the structure itself.
A stone dam can also serve as a spillway.   It can be up to 10

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feet in height.  It is made of rough stones.  The layers should
be bound by concrete.  The dam must be built down to a solid and
permanent footing to prevent leakage and shifting.   The base of
the dam should have the same dimensions as its height to give
it stability.
Small concrete dams should have a base with a thickness 50

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percent greater than height.   The apron is designed to turn the
flow slightly upwards to dissipate the energy of the water and
protect the downstream bed from erosion.
                                 APPENDIX III
                                PUMP SELECTION
                            Design for a Simple Pump
                                PUMP SELECTION
One choice for a water-powered pump is a positive displacement
pump.  Such pumps are called by various names:  bucket pump, lift
pump, piston pump, windmill pump, and occasionally even simply
by brand name, such as "Rocket" pump.   Numerous models are
available commercially and vary in cost from a few dollars for
small capacity pumps to several hundred for high capacity, high
head, durable, well manufactured units.   However, pumps can be
manufactured at low cost in the simplest of workshops.
One single acting pump attached to the wheel will cause speed
surges on the wheel because actual pumping takes place only
half the time, while the other half is spent filling the
cylinder.  During the filling stage, considerably less wheel
torque is required than when pumping is being done.   The speed
surge can be partially overcome by using:
*  Two single-acting pumps 180[degrees] out of phase so that one of the

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   pumps is always doing useful work.
*  A double-acting pump which

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   has the same effect as the
   one above but is built in
   one unit; or
*  best of all, two double-acting

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   pumps 90[degrees] out of phase.
Use of multiple simple pumps improves the overall efficiency of
the system.  (In general, one unit can be attached easily to a
crank at each end of the wheel shaft.)
Table 1.  Quantities of Water Pumped Per Stroke for
          Single-Acting Pumps of Various Bore and Stroke Sizes
          (Imperial Gallons)
                                             Stroke (in.)
Bore (in.)        2-1/4         4          6          8        10        12
1-1/4             .009        .016       .023       .032      .040      .049
1-1/2             .013        .023       .035       .045      .057      .069
2                 .023        .040       .062       .082      .102      .122
2-1/2             .035        .064       .095       .127      .159      .191
3                 .052        .092      .139      .184       .230     .278
3-1/2             .070        .125       .187       .248      .312      .276
4                 .092        .163       .245       .227      .410      .489
5                 .143        .255       .382       .510      .638      .765
An Easily Constructed Piston Pump
This pump <see figure> was designed by P. Brown

owd20x78.gif (600x600)

(of the Mechanical Engineering
Workshop at the Papua New Guinea
University of Technology) with a
view to manufacture in Papua New
Guinea.  Consequently the pump can
be built using a minimum of workshop
equipment--most parts are
standard pipe fittings available
from any plumbing supplier.
A PVC pipe can be used in place of
copper pipe.  This eliminates the
need for a pipe reducer.  The PVC
pipe can have a uniform diameter
To avoid having to bore and hone a
pump cylinder, a length of copper
or PVC pipe is used.  If care is
taken to select an undamaged
length of pipe and to see that the
pipe is not damaged during construction,
this system has proved
quite satisfactory.
As can be seen from the cross-sectional
diagram, the ends of the
pump body consist of copper pipe
reducers silver-soldered onto the
pump cylinder.  This does make disassembly
of the pump difficult,
but avoids the use of a lathe.
If a lathe is available, a screwed end could be silver-soldered
to the upper end of the pump to allow for simple disassembly.
The piston of the pump consists of a 1/2" thick PVC flange with
holes drilled through it (see diagram on page 78).   A leather
bucket is attached above the piston and together with the holes
serves as a non-return valve.   In this type of pump the bucket
must be made of fairly soft leather, a commercial leather
bucket is not suitable.  Bright steel bar is used as the drive
rod.  Threads must be cut into the ends of the rod with a die.
A galvanized nipple is silver-soldered to the top copper
reducer of the pump to allow the discharge pipe to be attached.
An `O' ring seal of the type used to join PVC pipe is used as a
seal for the foot valve.  This seal does not require any fixing
since it push fits into the lower copper pipe reducer.   A 1/2"
screwed flange with a plug in its center forms the plate for
the foot valve.  This plate is prevented from rising up the bore
of the pump by three brass pegs fitted in through the sidewall
of the pump above the valve plate.   Silver-solder the pegs to
prevent leakage or movement.
Parts and tools for a 4" bore X 9" stroke pump include the
1  12" X 4" dia copper tube
2  4" to 1/2" copper tube reducers
1  1-1/2" galvanized nipple
1  1/2" screwed flange
1  1/2" plug
1  1/2" PVC flange
1  rubber `O' ring, 4" dia
1  4-1/2" dia piece of leather
1  15" X 1/2" dia bright steel bar
1  1/8" dia brazing rod
Handi gas kit
Silver solder
Hand drill
1/2" Whitworth die
1/2" Whitworth tap
                                 APPENDIX IV
                           CALCULATING BEARING SIZE
Because it is very likely that people using this material will
want to change the size of the waterwheel they construct, the
following information is provided to serve as a basis for
determining the size of the bearings which must be used.
                  Approximate Weight Carried by Each Bearing
                  Excluding Loads Due to Attached Machinery
                    (per Meter of Width of the Wheel) (kg)
Annulus                                Outside Diameter (cm)
Width (cm)         91.5     122      183     244     305      427     610
    5                11       14.5    23
    7.5              16       21.5    32        43      54.5
   10                20       27.3    40.5      57      73
   15                        39       64       84     107      152     214
   20                                82       109     139     200      307
   25                                        132     168      241     348
   30                                        150     202      289     418
   40                                                        373      552
   50                                                        464      682
   60                                                                800
Bearing diameters required to support the various loads are
given in the table on the following page calculated on the
basis of 100 psi (i.e., a hardwood such as oak) in parallel
usage and 200 psi for end grain usage. Values are given to
90.90 kgs to allow for the largest reasonable bearing loads.
(*) Outside wheel diameter minus inside wheel diameter divided by
                   Minimum Bearing Inside Diameter Required
                          For Various Loadings (cm)
                                  Load (kg)
            45.5     91     227     454     908    2272   4545    9090
 Usage        2.5    3.8   5.75     8.25   10.88  17.75    25.5   35.5
End Grain
 Usage        1.5    2.5   4.5      5.75    8.25  12.5     17.75  25.5
These bearings are assumed to be steel on wood. It is likely

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that with metal shafts used in the larger sizes of waterwheels,
the bearing will be considerably larger than the required shaft
size. A "built-up and banded" bearing may be used. This is
accomplished by attaching a wooden cylinder to the wheel shaft
at the bearing location to bring the cylinder's outside diameter
to the necessary size. Then steel bands are bent and
fastened to the cylinder.
                            Calculating Shaft Size
Waterwheel shafts may be made of wood or steel. The diameter of
the shaft depends on the material used and the dimensions of
the wheel. The tables below give minimum shaft diameters for
bearing loads up to 45.45 kgs.
                 Minimum Standard Pipe Sizes for Use as Acles
                     With Bearings at 30cm From Wheel Edge
                                 Metal Shafts)
Bearing Load (kg)     45.5   91      227      454   908     2270   4540
Pipe Diameter  cm)
Solid Metal Shaft      2.5  3.75    6.25      7.5     10       15     20
               Minimum Standard Hardwood Sizes for Use as Axles
                     With Bearings at 30cm From Wheel Edge
                               (Wooden Shafts)
Bearing Load (kg)     45.5   91      227     454    908    2270    4540
Wood Shaft
Diameter (cm)         3.75   6.25      9       18    33     86.5    173
When comparing these figures with the bearing diameters, it can
be seen that for pipe or a solid steel shaft, a wooden bearing
will need to be built up. With wooden shafts, the required
shaft diameter will usually exceed the required bearing diameter
giving one the choice of reducing the shaft diameter at the
bearing location (but only there) or of using larger bearings.
In either case, the shaft must be banded with steel, sleeved
with a piece of pipe, or given some similar protection against
wear in the bearing.
                                  APPENDIX V
                           DECISION MAKING WORKSHEET
If you are using this as a guideline for using the Waterwheel
in a development effort, collect as much information as
possible and if you need assistance with the project, write
VITA. A report on your experiences and the uses of this manual
will help VITA both improve the book and aid other similar
                       1600 Wilson Boulevard, Suite 500
                        Arlington, Virginia 22209, USA
*  Describe current agricultural and domestic practices which
   rely on water at some point.
*  What water power sources are available? Include rivers,
   streams, lakes, ponds. Note whether sources are small but
   fast-flowing, large but slow-flowing, etc.
*  What is water used for traditionally?
*  Is water currently being used to provide power for any
   purpose? If so, what and with what positive or negative
*  Are there dams already built in the area? If so, what have
   been the effects of the damming? Note particularly any
   evidence having to do with the amount of sediment carried by
   the water--too much sediment can create a swamp.
*  If water resources are not now harnessed, what seem to be
   the limiting factors? Does the cost of the effort seem
   prohibitive? Does the lack of knowledge of water potential
   limit its use?
*  Based on current agricultural and domestic practices, what
   seem to be the areas of greatest need? Is power needed to
   run currently hand-powered machines such as grinders, saws,
*  What are the characteristics of the problems? Is the local
   population aware of the problem/need? How do you know?
*  Has any local person, particularly someone in a position of
   authority, expressed the need or expressed any interest in
   this technology/ If so, can someone be found to help the
   technology introduction process?
*  Are there local officials who could be involved and tapped
   as resources?
*  How can you help the community decide which technology is
   appropriate for them?
*  Given water power sources available which water resources
   seem to be available and most useful? For example, one
   stream which runs quickly year around and is located near to
   the center of agricultural activity may be the only feasible
   source to tap for power.
*  Define water power sites in terms of their inherent
   potential for power generation. In other words, one water
   source may be a power resource only if harnessed by an
   expensive turbine.
*  Are any materials for constructing water power technologies
   available locally? Are local skills sufficient? Some water
   power applications demand a rather high degree of
   construction skill. Is surveying equipment available? Do you
   need to train people?
*  Can you meet the following needs?
   *   Some aspects of the waterwheel project require someone
      with experience in woodworking and surveying.
   *   Estimated labor time for full-time workers is:
      *   4 hours skilled labor
      *  40 hours unskilled labor.
   *   If this is a part-time project, adjust the times
*  Do a cost estimate of the labor, parts, and materials
*  Does the technology require outside funding? Are local
   funding sources available?
*  What is your schedule? Are you aware of holidays and
   planting or harvesting seasons which may affect timing?
*  How will you spread information on, and promote use of, the
*  Is more than one water power technology applicable? Weigh
   the costs of various technologies relative to each other--fully
   in terms of labor, skill required, materials,
   installation and operation costs. Remember to look at all
   the costs.
*  Are there choices to be made between say a waterwheel and a
   windmill to provide power for grinding grain? Again weigh
   all the costs: feasibility, economics of tools and labor,
   operation and maintenance, social and cultural dilemmas.
*  Are there local skilled resources to guide technology
   introduction in the water power area?
*  Where the need is sufficiently large-scale and resources are
   available, consider a manufactured turbine and a group
   effort to build the dam and otherwise install the turbine.
*  Could a technology such as the hydraulic ram be usefully
   manufactured and distributed locally? Is there a possibility
   of providing a basis for a small business enterprise?
*  How was the final decision reached to go ahead--or not go
   ahead--with this technology?
                                  APPENDIX VI
                           RECORD KEEPING WORKSHEET
Photographs of the construction process, as well as the
finished result, are helpful. They add interest and detail that
might be overlooked in the narrative.
A report on the construction process should include much very
specific information. This kind of detail can often be monitored
most easily in charts (such as the one below). <see report 1>

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Some other things to record include:
*  Specification of materials used in construction.
*  Adaptations or changes made in design to fit local
*  Equipment costs.
*  Time spent in construction--include volunteer time as well
   as paid labor; full- or part-time.
*  Problems--labor shortage, work stoppage, training difficulties,
   materials shortage, terrain, transport.
Keep log of operations for at least the first six weeks, then
periodically for several days every few months. This log will
vary with the technology, but should include full requirements,
outputs, duration of operation, training of operators, etc.
Include special problems that may come up--a damper that won't
close, gear that won't catch, procedures that don't seem to
make sense to workers, etc.
Maintenance records enable keeping track of where breakdowns
occur most frequently and may suggest areas for improvement or
strengthening weakness in the design. Furthermore, these
records will give a good idea of how well the project is
working out by accurately recording how much of the time it is
working and how often it breaks down. Routine maintenance
records should be kept for a minimum of six months to one year
after the project goes into operation. <see report 2>

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This category includes damage caused by weather, natural disasters,
vandalism, etc. Pattern the records after the routine
maintenance records. Describe for each separate incident:
*  Cause and extent of damage.
*  Labor costs of repair (like maintenance account).
*  Material costs of repair (like maintenance account).
*  Measures taken to prevent recurrence.