Just For Fun

4Savonius Rotor

wind mill

Dave poses with windmill made of soda bottles and tubing.

Rotor blades are two-liter soda bottles with trapezoidal holes scissored out of their sides. Bottle caps are held to opposite ends of a 1 and 1/4-inch diameter, 1 foot-long dowel with two small wood screws apiece.  Horizontal dowel passes  through a 1-inch PVC plumbing T which tops a vertical length of pipe.  Rotor is supported on a vertical 1 inch dowel.  Between upper end of vertical dowel and horizontal dowel is a 1 inch hand-rolled Sculpey Clay ball bearing baked at three hundred F. for 30 minutes on an aluminum foil cushion.  This eases turning friction a lot.  In top of the T a 1 and 1/2-inch screw holds horizontal dowel in place and serves as a set-screw so rotor blades can be moved back and forth to balance, preventing excessive vibration.

This is an easy-to-build example of a Savonius rotor which turns because of force differential between concave and convex surfaces and is independent of wind direction.

(Important;  in assembling rotor, hold T in front of you cross upward, making sure the bottle screwed in so the right side is dished toward you and the one on the left dished away.  This assures the rotor will turn preferentially in a positive or counterclockwise direction.  If your rotor has a  negative spin, everybody in the know will think you’re inept or at least cynical!)

 

 

 

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