The
story of a waterwheel
by
Peter Morgan
Note from Chris Pirazzi: The official version of Peter's document lives at:
http://aquamor.tripod.com/Wheel.htmhowever as I continue to have trouble accessing his advertising-laden Tripod free hosting site, I have created a mirror of Peter's site here on my website at:
http://lurkertech.com/water/pump/morgan/tripod/You may also be interested in an online copy of Peter Morgan's related March 1984 article in the Blair Research Bulletin, which I have posted here:
http://lurkertech.com/water/pump/morgan/blair/or other information I have collected about water-powered water pumps here:
http://lurkertech.com/water/
Waterwheels have been used since ancient times to
grind corn and also to raise water. The great waterwheels of Hama in Syria have
raised water for over a thousand years. They serve as superb examples of a
technology so elegantly simple that it becomes totally dependable. Flowing
water was used to turn the wheel and water held in buckets on the rim was
lifted to great heights to spill over into channels which irrigated the land
further away. These great wheels where often built to huge proportions, because
water was raised on their rims. Some in the Middle East were 100 ft in
diameter. Water mills were common in Europe and elsewhere as a reliable source
of energy and they were put to many uses. Attempts to use the power of the
wheel to raise water above the level of the rim have often involved the use
valves, pistons and levers, but none of these match the elegant simplicity of
the wheel.
Huge
waterwheel in Syria used to pump water for irrigation
The waterwheels of Mazowe
There is another little story, almost forgotten, that
could be told of a few waterwheels that were built during 1979 in the Mazowe
area, about 30 kms north of Harare, Zimbabwe, then known as Salisbury. These
waterwheels raised water to well above the level of the wheel rim, under
pressure without the use of valves or pistons of any type. The pump consisted
of no more than a coiled pipe open at both ends. Water was raised as if by
magic, under pressure by the development of a series of air locks held in these
spiral tubes attached to the wheel.
This was far from an obvious concept. But the idea
came to me during our testing of a biogas tank fitted beneath a Blair toilet at
the Henderson school (see later). We built our first “spiral tube” waterwheel
pump at Henderson Research Station on 18th May 1979. I attached it
to a small waterwheel fitted over a water channel which supplied the fish ponds
at Henderson Research Station. In this first working prototype 20 metres of
25mm plastic pipe were attached to 2 metre diameter wheel which was rotated by
the flow of water. It delivered about 1.3 litres of water every time the wheel
turned. We used the wheel to pump water up to a tank. The small 2 metre wheel
Henderson operated almost continuously without maintenance for about 2 years
delivering about 7000 litres of water daily to a header tank near the canal
which fed water into a purification system. Very little maintenance was
required.
The
first prototype and operational spiral
tube waterwheel pump at Henderson
Testing
the first waterwheel pump at Henderson – water is coming out of the pipe well
above our heads!
The concept was so successful that later that year in
October, we build a 4 metre diameter wheel which was fitted on the large
irrigation canal at the Mazowe Citrus Estates. It also worked like a treat and
I fitted two spiral tubes, one on each side of the wheel to increase the flow
of water. Readings taken on this wheel
revealed that 4752 litres of water could be delivered to axle level per hour
and 3697 litres of water could be delivered per hour to a height of 8 metres
above the water level. We measured a canal flow rate of 1m/sec., canal width of
1.93metres, wheel diameter of 4 metres, number of wheel paddles was 16. The
paddle size was 600mm X 600mm, number of spiral coils was 2 with 3 spirals on
each side. The diameter of the pipe in the coils was 50mm and made of low
pressure polyethylene pipe. The wheel turned at 4.2 revolutions per minute when
water was delivered at axle level and 3.21 revs/min when water was pumped to
8m.
Assembling
and fitting the 4 metre diameter waterwheel at Mazowe
Parts
of the wheel were first made up in the Blair Laboratories. They were the taken
to the irrigation canal at Mazowe and assembled. The wheel was made up mostly
of plywood and pine beams. The axle was made from 75mm steel pipe, reduced
through reducing sockets to 50mm pipe. The axle was mounted through two sealed
ball bearings mounted on the two brick built supports at the side of the canal.
Wheel
upright and spiral tube fitted. About 35 meters of 50mm polyethylene pipe were
coiled on each side of the pump. The pipes were threaded through holes made in
the paddles. The two water collectors
were made of 150mm PVC pipe, each about one metre long. The ends of the
innermost coils were connected to the axle through polyethylene elbows.
The
waterwheel was impressive – a moment before fitting
Straddling
the canal. The brick mounts for the bearings had already been made.
The
wheel is mounted. Note the two pipes from the coils going into the axle. This
method of linking the pipes to the hollow axle with a galvanised steel cross
was not successful. The threads in the pipe were weak points and could not take
the strain under the weight of the wheel. The axle was replaced with a single
75mm steel pipe and the water was led into it through an entry point nearer the
bearing.
A drum was mounted on an eight metre platform high above the canal. Water
and air coming from the coils was led from the axle, through a simple water
seal to the vertical pipe which led to the drum. This photo shows the modified water entry
point into the axle, to one side.
Painted
up the wheel looked very smart.
The
axle, water seal and bearings. On the left
water is led from the two coiled pipes to a tee piece (on the inner side of the
central wheel) through the wooden discs which hold the spokes and then through
a bend into a steel tee piece on the main axle.
The axle is mounted on a bearing surface. Different bearings were
tested. The best were made of sealed ball bearings. A variety of water seals
were also tried. This one (RHS) shows a rubber bearing mounted in a PVC sheath.
A PVC adaptor attached to the axle passes into the centre of the rubber seal.
One side rotates, the other side is static. Bearings always leaked slightly.
The rotation of the wheel was slow.
View
of the wheel from the drum stand. An impressive site. Note the white PVC pipe
Which
is bringing up water from the wheel into the tank above.
The original wheel installed
in 1979 was replaced by a replica made of improved timbers in the early 1980’s.
This new wheel had larger paddles more closely shaped to the angled walls of
the canal. It was generally of a much stronger construction.
Another similar wheel was built on the Mazowe stream
by Ron Evans, the farm manager at Henderson Research at the time, with water
being led through a wear into a series of half drums fixed to the rim of the
wheel. This wheel too was 4 m in diameter. This wheel was made of steel
throughout and not of wood like the first wheel. Eventually the original wheel
on the Mazowe canal began to break up and a stronger unit was built there a few
years later using the original design. It continued to work for many years and
may still exist. A similar 3 metre diameter wheel was built for the Ministry of
Health stand in 1980 and attracted much interest. A smaller wheel was built by
my friend Dr Paul Canter, at the Triangle Sugar Estates It was a smaller
diameter about 1m but had many coils and pumped water to quite a height.
Ron
Evans and I inspect the all steel wheel at Henderson. It was placed in a wear
on the Mazowe stream at Henderson. In this case the water filling the quarter
steel drums fitted on the rim turns the wheel and the pipe is arranged in the
shape of a coil, not a spiral. The same principles hold true.
Fitting
the wheel in the brick built wear at Henderson.
On
the left a 3 meter waterwheel built for the 1980 Ministry of Health Trade Fair
Stand in Bulawayo, which attracted much interest. Few asked what the waterwheel
had to do with health! On the right a smaller waterwheel made by Dr Paul Canter
at Triangle Sugar Estates in the Southern Zimbabwe.
Making the wheel and pumps
The wheels were really intended to work in irrigation
canals in order to pump water from the canal to a header tank above the canal
for domestic use or for irrigation. The waterwheels themselves were made up
from a series of wooden or metal paddles attached through spokes of wood,
aluminium or steel to a central hollow axle mounted on “pillar block” ball
bearings placed on mounts placed either side of the canal. The “spiral tube”
water pump itself consisted of a length of plastic pipe so arranged that it
formed a spiral fixed to the sides of the wheel. In working wheels two spiral
tubes were used and these were horizontally opposed. Water entered each spiral
tube through an enlarged pipe which acts as water collector. The collector
picked up water as it dipped into the water flowing down the canal – like a
scoop. Enough water was picked up to half fill each coil. Thus a core of water
was picked up on each revolution of the wheel followed by a core of air. So an
alternating series of cores of air and water entered the coils, which passed
along the pipe as the coil turned on the wheel. The innermost spiral of the
tube delivered water into the wheel axle and there it is was led through a
simple water seal to a static rising water pipe to the header tank.
Waterwheel
being constructed at the Blair Laboratories, 1979
How does it work ?
The spiral tubes are fixed to the wheel so that the
spiral pipes rotate as the wheel itself rotates. The water collector connected
to the outermost end of the spiral tube gulps in a good quantity of water as it
passes through the canal, and delivers this into the spiral tube as it rises
above the canal. This core of water passes through the spiral followed by a
core of air as the wheel rotates. A new core of water is formed on every revolution,
and a new core of air. Thus a series of cores of water and air are formed
within each spiral pipe as the wheel rotates. Both spiral tubes deliver their
water and air into the axle of the wheel and there it is led off through a
water seal to a static rising pipe, which delivers water to the header tank.
As the wheel revolves a pressure head develops within
each coil of the spiral tube, water in the rising coils being higher than in
the descending coils. These cores of water in the spiral tube compress the air
between them as they travel around the spirals and both water and air are
expelled under pressure into the axle. The flow of water up the static rising
pipe is also accelerated by the compressed air escaping and expanding from the
outlet at the axle of the wheel. This effect also helps to lift water to the
header tank.
Diagram
of the spiral tube waterwheel pump from the side.
In
this view, the canal water is moving from left to right and the wheel is
turning in an anti clockwise direction. On each revolution the larger water collector
pipe dips into the canal water and lifts up sufficient water to half fill each
coil of the spiral pipe. Once the water
has been emptied into the outer spiral, air enters the pipe. Cores of water
followed by air enter the spiral pipe each time the wheel turns. These cores of
water and air make their way from the outer spiral to the inner spiral and then
into the axle of the wheel. Water in the ascending spiral pipe is always higher
than in the descending pipe. Thus the
weight of water held in the pipes on the “leading edge” of the waterwheel is
greater than the weight of water held in the “trailing edge” of the waterwheel.
The energy in the water falling on the paddles must be sufficient to overcome
this weight difference between leading and trailing edges of the wheel.
Tests carried
out showed that the highest point to which water could be pumped appeared to
depend on the number of spirals in the pipe and the diameter of the spiral. A 2
m diameter spiral tube wheel was able to pump water up to at least 8m with 6
complete coils, the same tube being able to pump water 6m with 4 complete coils
and 4m with 2 complete coils. The volume pumped depended on the amount of water
picked up and retained by the pipe during each revolution. Several spiral tubes
could be fitted to the same wheel, the ideal number being two. With a single
spiral, air and water are expelled alternately at the outlet, the pressure
heads in each coil developing to their own maximum as the water pressure head
in the rising main is at its highest. With two horizontally opposed spirals
tubes fitted to a single wheel, air and water rise through the pipe in more
regular bursts.
Considerable pumping heads can be achieved if
necessary by using an appropriate number of coils on a suitable sized wheel of
placed over a canal or river system charged with adequate water power. The
power delivered to the paddles must be sufficient to overcome the weight of
water held in the rising segments of the spiral and obviously this is a
limiting factor. If the weight of water held in the rising coils is much larger
than the weight held in the descending coils, the wheel may stop turning if the
power delivered to the paddles is insufficient. A balance must be struck between
the power delivered by the water on the paddles, the wheel diameter, the pipe
size, number of coils, and required head of water delivery. If the number of
coils in the spiral is not sufficient to pump water to the desired height,
water flows over from one coil to the next. Efficiency is lost. In these wheels
constructed, these various factors were worked out before the wheel were
constructed.
The great advantage of the system, was that once it
was worked out, the mechanics was very simple and reliable. The spiral tube
pumps made perfect partners for the wheel and both harmonised with the natural
world.
Other work with the spiral tube pump.
When these wheels were designed and built, we had
little access to such specific international literature. I searched through
volumes at the University to try to find some similar device, but failed to
find anything other than the Archimedes screw. A few years later I was in
correspondence with Peter Tailer who worked at the Windfarm Museum, Vineyard
Haven, Massachusetts, USA. He must have come across the paper I wrote about the
spiral tube pump and waterwheels in the Zimbabwe Rhodesia Science
News (Volume 13, No. 8. August 1997). He told me that the first
spiral pump had been created by a pewterer in Zurich in the year 1746 and an
account of it had been published by Thomas Ewbank in 1849 in America. Ewbank
reported that pumps of this type had been highly successful and were used in
Florence as well as Archanglesky in the latter part of the 18th
century. Peter Tailer wrote a manual on spiral pumps of this type in 1986. In
this manual he describes not only the complex mathematics of how and why the
pump works but also that a certain Peter Morgan of the Blair Research
Laboratory, was probably the first person to built a “Wirtz Pump” after it was
forgotten and lost for more than a century. In his manual he has written down a
part a letter I wrote to him at the time, describing the events which led to my
own discovery of the concept. It reads:
………“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 metre 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
has 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 face
full 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 Gaddie, 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 the pipe up and coiled it vertically in my hands with the
innermost coil turning 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 formed in them, the level of the water standing in the
vertical segment became higher. I rotated the whole spiral tune in my hands
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 then 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 tube
pump with two water inlets and two coils feeding 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 litres of water per hour to a height of 8 metres above the canal. After
two or three years, 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 VITA News of January, 1983, (Volunteers in Technical assistance) in the United
States, and in a Blair Bulletin of 1984.
In the Journal of Hydraulic Research, Vol 22, 1984,
G.H. Mortimer and R. Annable, both from Loughborough University, U.K. describe
the coil pump – theory and practice. A complex mathematic model is described
which I do not understand, but they do refer to my work and paper in Zimbabwe.
In this account reference is also made to Mr A Wirtz and his invention of 1746,
and also a description by Abraham Rees (1819) in his book “Cyclopaedia of
Science and Arts.” These authors state that the origins of the pump may lie
much earlier times in China, and also that … though the idea of the coil pump
has been gathering dust on some forgotten shelf for centuries, it is worthy of
further investigation and development.
My own independent discovery of this ingenious concept
was a fulfilling and very satisfying personal experience. Perhaps it is the
invention of which I am most proud. But ironically so few waterwheels of this
type were every built. In reality it has perhaps a very limited application.
But at any scale these spiral tube waterwheel pumps, were both simple and
effective and a great joy to watch in action. The story is well worth the
telling, for it forms part of an era of personal discovery long ago in that
valley of Mazowe.
Peter Morgan
Harare.
2003.