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Design calculations for no-head, low-head waterwheels | Backwoods Home Magazine


Issue #17 • September/October, 1992

For those of you who are still awake after reading my first installment, I will now continue. This part will deal with the design factors you will need to know to build a low-head waterwheel. It’s somewhat technical, but it is essential to know if you are to build a successful no-head or low-head waterwheel.

The most important thing to determine is “head”, or how far the water falls. If you have a small dam or waterfall, the answer is the difference in height between the free water surface on the “upstream” side, and the free water surface on the “downstream” side, in inches or feet. If you have a swift moving stream, the answer is only a bit harder to figure out.

The answer is in the equation for spouting velocity, which is the equation that describes the speed of any falling mass: “velocity squared divided by two times a gravitational constant”, which is expressed mathematically as <$EV sup 2>/2G. The gravitational constant (G) is 32.2.

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