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This pump uses a rotating pipe coil to pump water. It requires only moving water
to power it.
The pump in the picture pumps 400 gallons per day to a tank 50 ft above the
pump.
Low-impact lifestyler extraordinaire, John Hermans,
devised and built a water wheel for Earth Garden’s
writer and forest campaigner, Jill Redwood. Jill can
now refill her water tank from the Brodribb River
near her farmhouse in Victoria’s East Gippsland.
Her water wheel is silent, pumps about a litre a
minute, goes 24 hours a day, has only one small
moving part, and works on an ancient principle.
Here John describes how to build one.
by John Hermans
Clifton Creek, Victoria.
AS I have no political lobbying or media skills my way of helping the environment campaign is to help
those committed to saving forests. My skills lie in the areas of inventing and building. Jill had a 5 hp fire
fighting pump she used to refill her concrete water tank every fortnight or so. I first devised an
alternative pump using a set of water wheels, which, via chains and cogs that gave a 4:1 step up,
drove a small piston pump.
The petrol pump was temperamental and noisy. This improved model was temperamental and oily. It
did work quite well but was prone to occasional mechanical failure and there was the possibility of it
leaking oil into the pristine Brodribb River. So I got to work on an idea I had seen illustrated as a kids’
toy. As Jill lives on the upper reaches of the Brodribb River, the small flow in the river was not enough
to operate a hydraulic ram pump. The spiral water wheel has the advantage of being environmentally
friendly, almost maintenance free, made of basic cheap materials and is relatively easy to make for
anyone with a welder.
This positive displacement pump is made from a single length of coiled poly pipe and is designed to be
powered by water. The pipe is coiled in a vertical plane and mounted on a horizontal axle. As the
paddles rotate the coil of poly pipe above the water, the lower part is immersed. The open end of the
coil takes a small ‘gulp’ of water every time it rotates. An alternating sequence of air and water is driven along the pipe towards the centre of the spiral. Successive coils of pipe lead to a cumulative
increase in the pump’s pressure output. When a land-fixed pipe is connected to the last and smallest
coil, then water can be shifted to a higher point, such as a dam or a tank. In this case, Jill’s tank is
about 16 metres above the river.
Paddles and coils
The set of undershot paddle wheels (powered from water flowing below, not from water dropping onto
the wheels from above) drives the whole show. This is one of the oldest and simplest forms of motor,
driving one of the oldest and simplest forms of pump. The whole unit consists of only one small
rotating part called a rotating joiner, or in plumber terms, a spinning nipple.
When assembling the coils on the spokes of the frame, I had no idea how many coils and at what
diameter was needed to pump the water to the 16 metre head. The water wheel ended up about two
metres in diameter. As the water wheel and the spiral both needed to dip into the water, the coil has to
be the same diameter as the paddles.
Three quarter inch (19 mm) poly pipe can be coiled down to about 500 mm in diameter before it starts
to kink. If the coils are kept close together, around 40 coils can be made. I decided to make two lots of
coils consisting of 20 coils each, so there were two openings to take a ‘gulp’. In theory this should have
pumped twice the volume of water as a single coil rotating at the same speed. However, this proved to
be too heavy for the flow of the stream to move, so I had to remove one coil of pipe. As Jill’s place is
three hours drive away, there was much guesswork involved in my workshop and redesigning on site.
The final coil design saw 50 metres of three quarter inch (19 mm) poly pipe coiled into 20 loops from 2
metres to half a metre diameter. The pumping rate at this site is about one litre a minute but varies
from season to season.
Figuring it out
My theory then is that to successfully pump water, the coiled pipe needs to be about three times as
long as the height it is being pumped to. That’s a 3:1 ratio. I assumed that the size of the pipe is less
important than the total length. Larger loops are more effective at forcing water up than small loops but
consume more length. Fewer larger loops may be just as effective as many smaller loops.
The water exiting the smallest coil in the centre is piped into the hollow shaft of the water wheel’s axle.
The end of this then joins a stationary water pipe near the bank, in this case connected to a boom arm
(described below). To join the rotating shaft to the fixed poly pipe, a joiner is needed that can spin
constantly. Unless the connection is perfectly in line, these watertight rotating joiners can wear out
quickly.
To avoid flood damage to this water wheel pump, I mounted the axle and bearings onto a three metre
boom of 100 mm RHS that pivots at the end anchored to the bank. Along this boom, a height
adjustable support is set into the bank. A steel cable is attached to the water wheel that is operated by
a winch fixed even higher up the bank (see illustration). Not only does this allow it to be cranked out of
the water if a flood is imminent and hoisted safely above flood height, but it also allows the water wheel
to be lowered or raised to match the high and low flows of the river.
Construction pointers
Here are a few more pointers to help with constructing the coil section. To attach the poly pipe to the
angle iron spokes, use 1 mm stainless steel wire (you can order it from engineering suppliers). The
end of the three quarter inch poly pipe that scoops up the water should be increased in diameter for
the last loop. I used one inch (25 mm) for half a loop and then one and a quarter inch (32 mm) poly
pipe for the last half a loop. This allows for greater volume to be scooped up each rotation.
As both water and air are pumped up the delivery line together, it is best to send the pumped water
directly to the storage tank or dam. If the inlet and outlet line to the tank are the same, a special air
bleed line close to the pump will be needed, as Jill discovered when trying to use the taps on the same
line or have a shower!
A one-way valve will also need to be set in the line to stop water draining back out when the wheel is
not pumping. A filter isn’t a bad idea either. You can also fix a fly wire guard to the inlet end of the coil
that also reduces debris from entering the system.
One modification that had to be made over the last couple of years has been a more
robust and reinforced hollow shaft. The constant flexing and movement of the water
wheel, especially with faster flows, stresses metal and any weak spots are soon
discovered. The water wheel was sited on a slight bend in the river where it was narrow
and the water had a higher velocity.
Variables that allow this design to pump effectively are:
river flow
size of paddles
number of paddles
diameter of the wheel
diameter and number of the coils
submergence of the coils
inlet pipe diameter
height of storage tank/dam.
This spiral pump was a direct replacement of a small standard piston pump and has proved to be just
as efficient at pumping a set volume per day.
Overall, it’s a beautiful piece of alternative technology. And Jill says it also doubles as relaxation
therapy: after a torrid session dealing with planet wreckers, sitting by the river watching it quietly turn
puts some equilibrium back into the soul.
History and Theory of the Spiral Pump
In some instances, records of preindustrial technology can be a source of
concepts which can be updated with modern materials and modified to be
utilized in today's technology transfer efforts. In recent research, Peter Tailer,
curator of the Windfarm Museum on Martha's Vineyard, Massachusetts,
uncovered a two hundred and forty year old invention that has great potential as
a low cost, low technology pump for certain situations. This invention is the
spiral pump created in 1746 by H.A. Wirtz, a pewterer of Zurich, Switzerland.
Wirtz invented the spiral pump to provide water for a dye works just outside of
Zurich. Little is known about the inventor or the circumstances that led him to
create the pump. He probably was aware of the tubular form of the Archimedes
screw and the Persian wheel. Both of these pumps had existed for hundreds of
years. They were low lift rotating pumps which could not raise water higher
than the pump structures themselves. As Wirtz was a pewterer, he would have
possessed the metal working skills necessary to form a tubular spiral. It is most
likely that the dye works were located on the Limmat River, a tributary of the
Rhine, where the pump was powered by either a water wheel or horse whim.
The Wirtz spiral pump was constructed so the end of the outside pipe coil
opened into a scoop. The inner coil led to the center of the wheel where it
joined a rotary fitting at the axis of the machine. Figures 1 & 2 show an
historical reference's representation of the pump. This was taken from A
Descriptive and Historical Account of Hydraulic and Other Machines for
Raising Water by Thomas Ewbank, edition of 1849, New York City.
The Wirtz pump was constructed so that, with each revolution of the spiral, the
scoop collected one half the volume of the outer coil. As water was taken into
the coils, each column of water transmitted the pressure through the air to the
preceding column of water. In this way the water in each coil was displaced to
provide a pressure head. A cumulative head was built up at the inner coils and
was conveyed through the rotary fitting to an ascending delivery pipe.
Ewbank reports these pumps to have been highly successful and states they
were used in Florence as well as Archangelsky in the later part of the 18th
century. In 1784, a machine in Archangelsky is recorded to have raised "a
hogshead of water in a minute to an elevation of seventy-four feet, through a
pipe seven-hundred-sixty feet long." Lead or sheet metal was probably used to
fabricate the coils, which must have made the machine extremely heavy.
Problems encountered with the weight are mentioned as well as the general
unwieldiness of the larger machines. These slow turning, cumbersome pumps
became obsolete with the development of high speed steam engines.
An ideal Wirtz pump would follow Boyle's pressure-volume relationship and
the coil volumes would change with respect to changes in the entrapped air
volumes. Tubing of uniform diameter would not be formed as a spiral or as a
helix. This was understood by Olinthus Gregory in his work entitled Treatise of
Mechanics, edition of 1815. Gregory states on page 230 of Volume I that, "If,
therefore, a pipe of uniform bore be wrapped round a conic frustum...the spirals
will be very nearly such as will answer the purpose. It will not be quite exact[,]
for the intermediate spirals will be rather too large: the concoidal frustum
should in strictness be formed by the revolution of a logarithmic curve. With
such a spiral the full quantity of water which was confined in the first spire will
soon find room in the last, and will be sent into the main at every rotation. This
is a very great advantage, especially when water is to be much raised."
Gregory also described spiral pumps formed as a huge clock-spring-like spiral
sandwiched between two wood disks. This construction would allow the crosssectional
area of the coils to be varied so that a spiral pump could be built with
the correct volume in each successive coil.
The above cited 1849 work by Ewbank stated that he was not sure of the
relative advantages of the spiral or the helical Wirtz pump, the helical pump
having coils of the same diameter. The limits of the helical pump can be
approximated. If the inlet coil takes in half its volume in both air and water,
when maximum pressure is developed by the helical pump, the final cumulative
pressure head in the discharge coil will be substantially equal to the coil
diameter. Coils towards the inlet coil will develop heads of decreasing
pressures as air in the successive coils is compressed to a progressively lesser
extent. After a large number of helical coils, the pressure head in the inlet coil
will approach zero. Water will occupy the bottom half of the inlet coil and
water will be displaced by pressure to the inlet side of the outlet coil. Thus the
cumulative volume change of air trapped in the inlet coil will substantially
approach one half when this air reaches the outlet coil. This cumulative
reduction in volume can only provide an outlet gauge pressure of one
atmosphere, so that a helical Wirtz pump can apparently only pump to a
limiting head of 54 feet.
While this may be a sufficient head for many purposes, Windfarm Museum
built a spiral Wirtz pump to evaluate the potential to reach higher pressures and
pump to high heads.
In considering the idea of building a spiral pump, we theorized that if
cumulative heads build up a pressure of one atmosphere (14.7 psi or 34 feet of
water), the volume of air in that coil will be compressed to one half its initial
volume. However, the water in that coil is incompressible and occupies its
original volume. Thus, in theory, the length of the coil where the pressure
reaches one atmosphere should be 3/4 the length of the first coil if the first coil
takes in half its volume of water and half of air with each revolution. If the
innermost or discharge coil is one half the length of the first coil, a theoretical
evaluation would indicate that it would be completely filled with water.
However, Ewbank stated that, when compressed air and water occupied more
than the volume of an inner coil, the water "will run back over the top of the
succeeding coil, into the right hand side of the next one and push water within
it backwards and raise the other end." This caused a succession of flow back
over the tops of the coils ending with a dumping of the excess and a lessened
intake at the scoop. This can only take place in a spiral pump where the volume
of the coils decreases to the extent that some coils cannot accommodate water
and compressed air passed into them. The Windfarm spiral pump was built
with the diameter of the inner coil about one half that of the outer coil. This
was done so that a spiral of a given outer diameter could accommodate more
tubing of a given diameter to provide greater cumulative heads and pump to the
greatest height possible.
The possibility that Wirtz pumps constructed of modern materials could be
used in specific situations in developing countries motivated the Windfarm
staff to build and test a working model. The model was constructed under the
direction of Jonathan West who also designed the testing procedure.
When built with modern lightweight and inexpensive plastic pipe, the spiral
pump can be mounted on and driven by a paddle wheel. For pumping to low
heads, the spiral pump is quite satisfactory. However, when higher heads are
required, the spiral pump can be used to provide water for a home, a village, a
fish farm, or small scale irrigation. This simple machine can be site built and
maintained by relatively unskilled users.
Since first completing this report, two projects came to our attention. First was
an article in a quarterly publication entitled Waterlines, Intermediate
Technology Publications Ltd., 9 King Street, London WC2E 8HW, UK. In
Volume 4, No. 1, of July, 1985, there was a report on pages 20-25 of a Danish
Guide and Scout Association project on the Nile near Juba in Southern Sudan.
This project used raft-mounted, paddle-wheel-driven, helical Wirtz pumps for
irrigation. Each pump had four sets of 2" ID (52mm) tubing which was wound
on a float-mounted drum which was paddle wheel driven to pump to a head of
13'4" (4 meters). These pumps were reported to be very successful pumping to
this head.
The second Wirtz pump project was brought to our attention by Peter Morgan
of the Blair Research Laboratory, P.O. Box 8105, Causeway, Harare,
Zimbabwe. Peter Morgan was probably the first person to build a Wirtz pump
after it was forgotten and lost for more than a century. His account of its reinvention
follows as it is not only interesting, but helpful in understanding the
device:
The spark of the idea jumped when I was adjusting a pipe carrying a gas from a
biogas digester we had installed beneath a toilet at the Henderson Research
Station near Mazowe. The tank had developed at least one cubic meter of
methane, but I could get no gas out of the end of the pipe which led from the
digester to the stove nearby. I remember being annoyed by this as it was
obvious that a type of airlock had developed in the pipe leading gas from the
tank to the outside.
We looked down the toilet hole and I noticed that the pipe had become coiled
several times. This was possible because we had allowed quite a lot of pipe to
be used to accommodate the up and down movement of the digester gas tank.
In earnest I pulled hard on the pipe whilst looking straight at the end of it. The
pulling of the pipe released the airlock and I got a facefull of very bad smelling
mess and gas. Pulling the pipe had released the airlock and gas now flowed
freely outward.
From that moment I wondered what could have been going on down there. It
was obvious that fluid produced by the digester had built up at the base of the
coils to produce airlocks. These had, in effect, held back the gas produced by
the digester. I wondered whether the reverse might be true. Could one coil a
pipe up, which contained a number of deliberately made airlocks, and develop
pressure?
On a later visit to Henderson with my good friend, Peter Gaddle, Blair's Chief
Field Officer at the time, we came across a length of clear plastic pipe laying on
the ground. Recalling the experience with the digester, I picked up the pipe and
coiled it vertically in my hands with the innermost coil turned to the horizontal
and then turned upward to form a vertical segment.
I asked Peter to carefully pour water down the vertical pipe. Water passed over
each spiral of the tube into the next spiral and then into the next. A series of
airlocks had been formed in the pipe. As more coils had water and airlocks
form in them, the level of the water standing in the vertical segment became
higher. I rotated the whole spiral tube in my hand and, to my joy, water shot out
of the top of the vertical pipe segment above the spiral! This was a most
memorable and thrilling experience for Peter and me.
I couldn't wait to get home and make a bigger version of the model in my
kitchen. This too worked well and I found that by adding water to one end of
the spiral and rotating it, I could drive water up the vertical pipe segment some
distance.
The day following Peter and I built a two meter diameter model at Henderson
and fitted it to a waterwheel with paddles attached. The paddle wheel was
mounted in a small water channel. The wheel turned and on each turn I
arranged for the outer coil to pick up water from the channel. On each turn a
core of water followed by a core of air passed into the spiral next to it until
finally arriving at the innermost coil. It was the led to a rising pipe through a
simple water seal. The effect was thrilling as the system worked so well. Water
was fed into a tank and the machine worked for years afterward.
I then developed a horizontally opposed spiral pump with two water inlets and
two coils feeding to a single outlet. This doubled the volume of water
produced. From this we then built a much bigger 4 meter diameter wheel on the
Mazowe Citrus Estates canal. This pumped an impressive 3697 liters of water
per hour to a height of 8 meters above the canal. After two or three years, only
the wheel was rebuilt of stronger materials where it remains today as reliable as
when first built. Several other wheels have since been built in Zimbabwe.
Peter Morgan's work with the Wirtz or spiral pump has been published in a
local Zimbabwe science magazine, "Science News", in the United-States-based
VITA (Volunteers in Technical Assistance) News of January, 1983, and in a
Blair Bulletin of 1984.
Construction
Wheel and Spiral
When considering the building of a spiral pump, we assumed that the pressure
produced would be directly related to the wheel diameter and the number of
coils. After some deliberation, a six foot wheel was built. It was felt that a
smaller wheel with proportionately smaller coils might not provide high enough
pressures for a realistic evaluation of working sized machines.
Two different pipe sizes were used to form coils on the wheel to provide a
broader range for the tests. The first series of tests were performed on the wheel
with the coils formed from 160 feet of 1-1/4 inch ID flexible polyethylene pipe
(rated 100 psi at 73°F). This configuration is shown in Figure 3:
The outside coil was formed on the circumference of the six foot wheel. Each
successive coil was wound closely within the outer coil to maintain the largest
possible diameter for all the coils. This provided thirteen coils with the radius
of the outer coil being 36 inches and the radius of the innermost coil being 17
inches. Another series of tests was performed on the wheel with coils formed
from 280 feet of 3/4 inch ID flexible polyethylene pipe (rated 100 psi at 73°F),
A photograph of this wheel is shown on the cover. This was wound with the
outer coil 36 inches in radius and the innermost coil 16 inches in radius to
provide a total of twenty-one coils.
The wheel itself was built in a six spoke fashion with a double thickness of 1 x
8 planking. A 1-1/2 inch hole was drilled in the center of the wheel to allow
passage of a pipe leading from the innermost coil to the rotary fitting.