Mechanical

Here are some photos of a small wind turbine using PVC blades.

The two blades are adjusted to right angles after the nuts are partially tightened. This is the wider area of the blade where the cylindrical center is not cut flat. Near the ends, the inside area is cut down to make the upwind side flat from leading edge to trailing edge.

Two locking nuts on the shaft hold a flat washer to the windward blade. Each blade is cut to the same profile, but the back blade has a relief cut to nest the blades closer together. Note the nonflat area left in the middle of the blade. A narrow blade will have less concave curvature.

The sides of the back blade have been relieved to allow the front blade to fit closely. If there is any gap, the front blade will cup forward when the nuts are tighted.

The tip is faired back slightly. The blade is cut from 4 inch DWC sewer pipe. The radius of the blade is 18 inches; the full length is 36 inches. I prefer an even number of blades to allow the material to take the centrifugal force in the hub area instead of a bolted joint.

The front of the windward front blade with a lockwasher. This is all hand-held work with a bench grinder, and it shows. A special router blade would make this a quick, more accurate job.

Another too low photo to be replaced.

Had I held the blade lower in the camera viewfinder, you could have seen the airfoil tip. Still, the outside convex surface is ground and sanded to make a narrow convex leading edge and a knife-like trailing edge. This side is on the back side, while the upwind side is nearly flat.

Side view of the rain shield showing the flap above the drive wire.

A closer view of the cutting of a juice can to form a rainshield. This one is some ten years old. The can was opened with only one punch, and when empty, was opened to half diameter. The flap was bent to shed rain from the entrance.

The bicycle front shaft bearing from the side. The standard pliers show the scale. A small wire yoke couples the downwind shaft to the #12 wire that couples the shaft to the small motor.

This is the windward end of the yaw axis and the shaft bearing. The spoke plates are screwed to the wood blocks. Behind the bearing assembly is the rainshield covering the servomotor (PM generator).

The "T" has been filed out to allow the horizontal pipe to pass through. A screw secures the pipe to the "T". The leads pass through a caulked hole, down through the azimuth or yaw bearing, and then down and out of the fixed pipe.

The yaw axis rotating pipe slips over the Schedule 40, fixed pipe that is bolted to the steel mast. The drop wire is thus accessible outside. The inside pipe is too flexible and should be strengthened with a hollow liner of some type.

A cable clamp holds wire to the mast without a drilled hole. The cable thimbles allow some swiveling without wearing the cheap sisal rope. In a less-protected area, steel guy wire should be used. Since the rotor diameter is small, there is not much stress from the thrust forces.

The twist-off connectors allow disconnection to unwind the 18 gauge zip cord drop wire. A larger system could have a longer drop wire to a junction box near the bottom and #12 underground burial cable to the building.

The tail vane is a painted license plate. Three screws hold it to the PVC. A piece of flagging tape shows the direction of light winds, and also shows how well the turbine is tracking the wind.

This basic turbine is relatively easy to duplicate. Perhaps someday I can make up a parts list and cost budget.

Content of this page created and/or adapted by Frank Leslie
detail/Mechanical/mechanical.html updated 07/26/2001 by Frank R. Leslie