The first project was a vertical turbine design called a Lenz Turbine. The first model was made from light but flimsy materials - it wasn't designed for longevity, only as a proof of concept idea. So, some foamcore board, posterboard, and a piece of scrap fiberglass-reinforced plastic sheeting (scrapped at the bus factory where I work) were my construction materials for the first model. Oh yeah, and a ton of packing tape.

The model basically consists of three wings, connected evenly, and spinning together around a rod. This unit (in theory) provides the spinning motion needed to power a generator (which converts spinning motion into electricity, exactly the reverse of an electric motor - so most electric motors can also be generators).

I made up a quick design in a graphic design program called Inkscape, printed it, and started cutting my wing profiles out. This piece would provide the support for the wing shape. Each wing has three of these. The only other thing to the wing is a piece of poster board wrapped around the foamcore supports and then the whole thing gets taped together using lots of packing tape!

After the three wings have been constructed, the next step is just to attach them to something so that they will spin together and are equally spaced away from the center. I cut two identical triangles which would attach at the top and bottom of the wings to hold the whole thing together. I used the plastic sheet for the top because in my design, the weight of the whole unit hung from the top because just beneath the top is where the stopper on the shaft is located, which keeps the the turbine from sliding down the shaft it's spinning around. To save on weight, I just used foamcore for the bottom because it's only real job was to keep the bottoms of the wings from collapsing toward the center of the circle.

With my two triangles in hand, the next step was to fashion a way for them to be able to spin on the shaft I was using (in my case a salvaged 1/4" metal dowel). We have to do this before we attach the wings because it's harder later. So, using some quick math I found the center of the triangles and drilled a hole of about 1/2". To keep the plastic from being torn by the spinning motion against the metal shaft, I just glued a washer with a hole slightly larger than the shaft diameter over the holes, so that the washers would rub on the dowel instead of the plastic/foamcore.

With that accomplished, we're ready to attach the wings to the triangles (or you could use circles, I just used triangles to save material). The webpage at recommended that the wings have an inward tilt of 9 degrees from the angle perpendicular to the circle. So, I used a compass to figure out the angle perpendicular to the line from the center to the triangle tip, and then went 9 degrees inside that. With that line on the triangle tip, I drew a line down the center of the fins, parallel to the long flat side of the wings. Matching those two lines up, I glued and taped the wings to the triangles.

The final step is just to slide the dowel through the hole in the top and bottom triangle, and then fix something on the shaft to prevent the triangles from sliding down it. I accomplished this with another washer butting up against a big wad of tape wound around the shaft. Not elegant (or durable) but good enough to get the job done - time to go test it!

The wind test proved that the design is pretty good at spinning in small amounts of wind. I tied some toilet paper to the dowel because it's hard to guage the wind by looking at the grass, and without knowing what the wind was doing, what does it tell you that the windmill is spinning? Anything will spin in enough wind - we need to shapes that spin in little wind!


Update: I tried to attach a makeshift generator to the assembly to see if I could get electricity out of it even though the project was just to test how well the Lenz design would catch the wind. I found a motor in an old computer tape drive, attached a KNEX pulley to the turbine, and used a rubber band to get the pulley to turn the motor. It didn't work. The rubber band is too stretchy, the tape drive carrier isn't flat so the rubber band hangs on it, and the washer being pulled against the shaft makes the whole thing vibrate since it's spinning off center. I didn't really expect this to work - for good reason apparently. However, I'm not letting this detract from the success of the principal project, testing the Lenz turbine design. Success!

Update #2: The model met with an unfortunate accident when my little brother was spinning it quickly by hand and accidentally pushed the upper triangle over the top of the dowel, making the whole thing come to a spinning crashing stop as it fell off center. Fortunately, we've already moved on to the bigger full scale model!

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