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MacGyver

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Joined: 12/05/2009
Location: United States
Posts: 1329

Posted: 01:36am 16 Jun 2010

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Problem Solved (I think):

For any of you who are following my lead and building Coroflute plastic windmill blades, I found out why my first test model bit the dust. The blades are basically hollow from the root to the tip, but I closed off the tip to make it look nicer as well as keep a sharp corner from being dangerous in the event it came in contact with flesh while spinning. Originally my test tower stood only about 7 feet off the ground, so 24-inch blades on a 4-inch stand-off brings the tips to within striking distance of anyone standing their gawking (me).

Well . . . today as I was taking apart that first set of blades, to my surprise, one was partially filled with water. That might have been what initially threw off the balance . . . ya think? (MacGyver mutters "duh-yup" under his breath)

My test stand has another problem in that the single bearing I am using to mount the test candidates on is both weak and loose. It will allow the blade tips, especially longer blades' tips, to be forced back against the tower and the rest is a no-brainer; tower strike!

At first look, I thought the wood stand-off spars were at fault and while they obviously aren't strong, at this point, they seem robust enough to hold a "balanced" set of blades. Even a slight imbalance at high-enough speed will cause things to shake apart.

So . . . if you're building these blades, leave the tips open or at least leave a little slit so condensation (rain in my case) can escape or you'll be traveling the same path I waddled down!

I took a few (5) short videos of the new blades (16", square corners, open tip) turning in the breeze and will post them on youtube later on and come back here with a link. The whole reason for today's test was to see if the open blade tips would stop the noise created by the blade tips speeding through the air and so far, it seems to have been a success. I'll test this thing in heavy wind and toss up a video for everyone. Here's hoping the "no-noise" deal is a keeper!

[Quote=MacGyver]I took a few (5) short videos of the new blades (16", square corners, open tip) turning in the breeze and will post them on youtube later on and come back here with a link.

Here are the links:

Minute & a half Coroflute Blade-test Video

Short Blade Tip-noise Test Video

. . . . . MacEdited by MacGyver 2010-06-17

Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas

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