Building a working scale-model of a windmill is a great craft project for school or just for fun. This model is not powerful enough to provide much power, but you can detect the current with a multimeter. If you design the blades well and fit everything together securely, you might be able to power an LED light bulb.
STEP1: Building the Base
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    Prepare the materials.
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    Assemble two T-shapes from PVC pipe. This will form the base of your windmill tower. Use 1″ (2.5 cm) diameter PVC pipe cut to the lengths described below, and attach as follows:

    • Fit three 6″ (15 cm) lengths of pipe into the three holes of a T-junction. Tap the pipes together with a hammer so they fit together tightly.
    • Make an identical shape with three more 6″ (15 cm) segments and a second T-junction.
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    Drill a hole in a new T-junction. This third T-junction needs a new hole so you can snake the wires through that conduct power from your windmill. Follow these steps to drill safely:

    • Secure the T-junction in a vise. Position it so the central branch points downward.
    • Dent the back of the T-junction with a hammer and nail, leading into the central branch.
    • Use the dent as a guide to prevent your drill from slipping. You can use a drill bit designed for wood or metal.
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    Connect the two pieces into an H-shape. Use the third T-junction you just drilled to connect the two central branches of the T-shapes. Fit these into opposite ends of the T-junction, to form one large “H.” Before you make the connection tight, lay the H flat on the floor. Position the T-junction so the empty hole is pointing upward, and the hole you drilled is on the floor.
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    Attach four feet. The “feet” of the windmill are four 90º PVC elbow connectors. Attach one to each of the four ends of the H. The open end of the connector should be flat on the floor, so it supports the H with the central T junction facing straight up.
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    Add the tall central pole. It’s up to you how tall to make your windmill, as long as the blades have room to spin without hitting the base. A 24″ (61 cm) length of pipe should work well. Attach this securely in the central T-junction.

STEP 2: Assembling the Rotor
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    Find a small DC motor or dynamo. This should be as close to 1.1 inches (2.8 cm) in diameter as possible, since it needs to fit snugly inside a PVC coupling. You can buy the motor at an electronics store, or look for a “turbine kit” online. The turbine kit may include a hub, dowels, or other parts you need for this section of the project.

    • The motor should have two attached wires. Before you continue, confirm that the hole you drilled in the T-junction can fit both the wires. If it cannot, expand the hole with a larger drill bit.
    • The driveshaft of this motor will need to fit into a hub (described below). You may want to buy the hub first, then take it to an electronics store to find a motor that fits securely.
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    Fit together a 90º connector, short length of pipe, and coupling. Attach a 3″ (7.5 cm) length of PVC pipe into a 90º elbow connector. Fit a PVC coupling over the other end of the straight pipe. You’ve just made the “nacelle,” or compartment that will house the rotor.

    • As before, make all connections tight by tapping them together with a hammer.
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    Thread the wires through this section. Feed the wires attached to the DC motor through the coupling, and pull them out through the elbow connector.
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    Secure the motor at the opening of the coupling. It’s important to fit the motor snugly into the mouth of the coupling. To ensure this, wrap the motor with duct tape until it fits tight against the wall of the coupling. Position the motor so the driveshaft end protrudes slightly from the opening. Make it as straight as possible, since an off-centered motor will cause your windmill blades to wobble.
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    Mount a hub over the driveshaft. This hub should fit snugly over the driveshaft without pressing against the body of the motor. Most people either use the hub from a “turbine kit,” available online, or a spool from a Tinkertoy set, with one central hole.

    • You can save money (and get an exact fit) by cutting your own hub out of plywood (a circle with angled slits in the edge for attaching the windmill blades). This is fairly difficult at the small size described in this project, at least for novice woodworkers.
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    Extend the motor wires. Get two extra wires long enough to travel down the vertical pole of the windmill and out through the hole you drilled in the base. Attach them to the two wires on the motor using twist-on connectors.

STEP: 3

Finishing the Windmill

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    Thread the wires down through the windmill. Have someone hold the top section (nacelle) while you drop the wires down through the vertical pipe of the windmill. Pick up the wires from the base and pull them through the hole in the base.
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    Fit the two parts together. Fit the elbow connector on the nacelle over the vertical pipe, tapping them together with a hammer. Position it so the hub faces forward, between the two legs of the “H” on the base.
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    Attach rods to the hub. Both the kit and Tinkertoy hubs have holes spaced around the edge of the circle. Insert dowels or Tinkertoy rods into these holes. Each rod will support one blade on the windmill. You can use any number of blades on your windmill, but they must be evenly spaced around the hub. If the blades are unbalanced, the windmill will vibrate as it runs, and parts could break.

    • Make these rods as secure as possible. If they are loose, they may fly out at high speed while the windmill is spinning. The safest option is a dowel slightly too large for the hole, with one end sanded down until it barely fits.
    • Start with two to four rods, so it’s easy to experiment with the design of your blades. You can always add more later if you need more power. Professional wind turbines rarely have more than three blades.
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    Cut out blades from stiff paper or other light materials. Try poster board, or a sturdy paper or Styrofoam plate. If you want stiffer blades (which provide more power), buy thin sheets of balsa wood from a craft or home improvement store. Cut the blades to any shape and size you like, but make sure they are all identical so your windmill is balanced.

    • The blades will work better if the tip is rounded and narrower then the rest.
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    Attach the blades to the dowels. Use strong glue or another strong adhesive. Just make sure the blades are very well attached, or they could fly off when the windmill spins.

    • For best results, tilt the blades 35.5 degrees back from the plane of the hub. Eyeball this as slightly more than ⅓ of a right angle.
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    Hook the wires up to a multimeter. The motor powering this model windmill is very small, and probably can’t power anything significant. Hook it up to the leads of a multimeter set to measure DC voltage instead. Depending on your blade design and wind strength, you will probably see a result of 0.2 to 0.5 volts once the windmill is running.

    • It is possible to get above 1 volt if the blades are made of stiff material, and have the right shape, size, and angle. In this case, you might be able to make an LED flicker. Red LEDs are the easiest to power.
    • Put on safety goggles. Anyone near the windmill should wear safety goggles while the windmill is running. If a piece of the windmill breaks, it could fly off at high speed and injure someone. Reduce the risk by standing behind the windmill or in front of it, not on the side.
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    Test your windmill model. Set up the windmill so the hub is facing the wind directly. If the wind hits the blades at an angle, the force could snap the driveshaft or knock the motor loose from the windmill.

    • If there’s not much wind today, you can test your windmill indoors in front of a strong fan, centered in front of the hub. The air from a fan is more turbulent than wind, so correct this by blowing the air through a “honeycomb” of paper towel tubes, milk cartons, or other open tubes.

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