Undershot Water Wheel

This is a nicely done undershot water wheel project that blends in well with its setting.  Much of the project was done with parts recycled from various sources.


Full details on how to construct the wheel (pdf 3.5 MB)


Excel Spreadsheet model to help with design (Excel xls  27 KB)


Thank you Allan for submitting this!!


Update from Allan -- April 18, 2008 ....


Some Follow-up qustions on the water wheel -- 2/15/07 ...

"Water Wheel Engineering",  a paper by Ron Shannon with some good design information on undershoot water wheels.


Some pictures of the water wheel:

Note: A couple of these pictures do not appear in the "Full Details" write up above.


The wheel in operation



View from inflow side of wheel.



















Tape drive motor used as generator, and cable spool ends that form the sides of the wheel.








The wheel buckets cut from PVC pipe.


Shaft, bearings and primary gear.  A larger gear ratio than is shown will probably be required for good performance -- download the pdf file listed above for details.



Generator and gearing.



Looks like its been there for a hundred years.


Some Follow-Up Questions:

These are the answers to some email questions on the water wheel:

1) How does the generator hook up to the power source? Single
battery or multiple?

As several of the photos show, I use an isolation diode (30 Ampere) to prevent the battery bank (Ten 220 AH T-105 batteries wired in series/parallel for 12 volts @ 1100 AH) from back feeding the generator. The hookup is through a 30 ampere Square-D QO breaker right onto the battery buss of my solar system. There is no need to use a controller since the power output from the generator could not overcharge the battery bank.

2) Where can I get a generator as shown? What is the generator
connected to in the picture with the generator mounted in the gearbox?

There is a pretty good discussion of this particular generator/motor at http://www.otherpower.com/otherpower_experiments_tapedrivemotors.html along with possible locations where one could purchase one. Another option would be to use a permanent magnet automotive alternator from http://www.hydrogenappliances.com/powerpmas.html though I've not tested performance with one, it would be my choice with a larger water wheel. As to question 2b, see my answer to question 1.

3) Do you have to regulate/control the charging of the battery
somehow? With what?

See answer to question 1.

4) It seems like the water is entering at midpoint of the wheel.
Would more power be produced if water entered at the top - a true
overshot wheel?

As Ron Shannon's Water Wheel Engineering presentation at http://ipc6.permaculturewest.org/ch08/shannon/index.html indicates, the efficiencies of an overshot and undershot wheel are very similar. The selection criteria I used was a matter of available head at my alternate site. The original site and intent was to incorporate the wheel in an overshot configuration but my wife had other plans. I had taken photos and written a bit of a detailed story as to how the current location was selected after my original location (a four foot waterfall) was firmly rejected just prior to installation for aesthetic reasons... I later opted against submitting it since it offered nothing of value to the design other than an example of its flexibility.

5) Author did not say what he was powering from this wheel/generator. Any idea?

I utilize the power generated from this wheel to subsidize the output from the two 500 Watt solar panel racks as it was available and otherwise a wasted resource. New England has had no scarcity of rainfall these past few years at the expense of diminished sunshine. The composite system powers communications equipment, three freezers, propane furnace/hot water, well pump and all electrical requirements of my barn thereby reducing my utility bill by 50%.

 I'm pleased to report that the waterwheel has performed very well up until the stream froze solid. I'll let you know how it does after the spring thaw and about 2 million gallons per day attempts to get past it during April/May.




Thanks to Allan for providing these answers!



Update from Allan on April 18, 2008:

"I tightened up the tolerances around the sluiceway to give merely a 1/4 inch clearance to the water and this resulted in almost a 30% increase in velocity and torque. I'm researching (in earnest) a more efficient generator to boost the output closer to the theoretical value."






Updated 2/15/07, April 18, 2008