This machine was built by a neighbor of ours in about 2 hours, 6 years ago. It's been in constant operation since, except when the creek is frozen. He chose a natural dam, which was created when a tree blew across the creek. The tree is approx. 20" diameter.
A slot was cut in the tree to channel the water into the turbine. The turbine was made from a junk squirrel cage fan. The fan housing was bolted to the tree, so that the water poured into the "output" of the fan, and came out a hole which was cut in the bottom of the fan housing, making for an "undershot" waterwheel. He used the pulley which was already on the fan, and belted it to a surplus computer tape drive motor (the kind they used to use in large computer tape drives, check our Products page for availability). The gear ratio is 1:3-- the generator turning 3 times faster than the water wheel. They make excellent low rpm generators. This system charges 2 amps into a 12 volt battery, 24 hours per day! His only power needs were 2 lights, and a small car stereo, the water wheel provided more than enough. It doesn't work after the creek freezes(4-5 months of the year), and he simply lets it freeze over each year, without any apparent damage.
It's easy power, cost next to nothing to build, and is low maintenance. The front bearing has failed twice (once every 3 years), but no effort was made to keep water out of the bearing--doing so might fix this problem. 2 amps may not seem like much, but consider the cost of solar panels required to produce 576 watt hours per day! Simple improvements could certainly be made to make a machine like this much more efficient. It uses a normal V belt, which introduces a lot of friction and loss. I don't know for sure, by my guess is the V belt may suck more than half the available power here. Gears, or a smaller belt would be interesting. I don't believe he ever took the time to try different pulley combinations either, it's possible there is room for improvement. Since we have been experimenting with them, it seems like a homebuilt wooden alternator or induction motor converted to an alternator (see our experiments page for more information) would work more efficiently by charging at lower rpm. Considering all the room for improvements, it's reasonable to think a unit like this could provide twice or three times the power. 50 watts, 24 hours per day would be an incredible amount of power considering the cost, low maintenance, and only about 20" of head on a small creek.
Other simple undershot waterwheels have been made using 55 gallon metal or plastic drums with attached vanes, suspended above a river. Please let us know about your experiences with home built hydro power!
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