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Wind turbine: test
Aug. 27th, 2009 23:25I went out to Pittsburg tonight to test the turbine.
I assembled it half by feel, in the dark, until Greg came up with one of the head-lamps that illuminates where I look (better than him having to hold the floodlight on it). I screwed the pipe to a board, clamped the board to a fence, assembled the apparatus and put it up -- first time without even any chains, just the freespinning rotor, to see how it did.
Result: Abject failure.
Granted, the wind direction was erratic; it kept flipping up to thirty degrees back and forth, which meant the blades had trouble maintaining their momentum (change the course of a spinning bicycle wheel and see how much speed it loses). But even when I gave it a hefty starting spin, either direction, in a couple of minutes it had reverted to shifting uncertainly this way and that way, not actually spinning at all.
I put the blades on backward, so the concave side faced outward, and it seemed to do very slightly better (though that may have been my imagination).
My only thought is that I need to check the pitch of the blades, to make sure the leading edge is in the same plane as the face (in airplane terms, make sure it's not trying to "lift off" off the face of the rotor or tilted to "descend" into it). From what I remember from balancing them, though, they're basically planar. So.... maybe it needs a steeper pitch to "bite" into the wind? I really don't know. Everything I know about airfoils said that these blades should have spun at some speed in 15-20 mph winds, and they failed utterly.
The scenarios I expected were: success (thus it goes to the Burn) or failure in that the blades are too small (thus it stays home for a year). I found scenario three: failure so total and inexplicable that I take it to the Burn... because there are lots of wind-power experts there who might be able to help.
It's been an interesting project. For now, I'll focus on getting the bikes ready, packing, and cooking.
I assembled it half by feel, in the dark, until Greg came up with one of the head-lamps that illuminates where I look (better than him having to hold the floodlight on it). I screwed the pipe to a board, clamped the board to a fence, assembled the apparatus and put it up -- first time without even any chains, just the freespinning rotor, to see how it did.
Result: Abject failure.
Granted, the wind direction was erratic; it kept flipping up to thirty degrees back and forth, which meant the blades had trouble maintaining their momentum (change the course of a spinning bicycle wheel and see how much speed it loses). But even when I gave it a hefty starting spin, either direction, in a couple of minutes it had reverted to shifting uncertainly this way and that way, not actually spinning at all.
I put the blades on backward, so the concave side faced outward, and it seemed to do very slightly better (though that may have been my imagination).
My only thought is that I need to check the pitch of the blades, to make sure the leading edge is in the same plane as the face (in airplane terms, make sure it's not trying to "lift off" off the face of the rotor or tilted to "descend" into it). From what I remember from balancing them, though, they're basically planar. So.... maybe it needs a steeper pitch to "bite" into the wind? I really don't know. Everything I know about airfoils said that these blades should have spun at some speed in 15-20 mph winds, and they failed utterly.
The scenarios I expected were: success (thus it goes to the Burn) or failure in that the blades are too small (thus it stays home for a year). I found scenario three: failure so total and inexplicable that I take it to the Burn... because there are lots of wind-power experts there who might be able to help.
It's been an interesting project. For now, I'll focus on getting the bikes ready, packing, and cooking.
