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Forum Index : Windmills : How to determine tower size?

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434josh
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Joined: 13/06/2012
Location: United States
Posts: 10

Posted: 01:11pm 13 Jun 2012

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I am building a wind turbine and am trying to figure how strong my tower will need to be.
So far I have blades. 3.3 meter 3 blade. Tower top weight will be about 100 lbs. Height will be 35 to 40 ft.
My avg ground level wind is 12mph with 20 to 23 MPH days common.

Any advice or suggestions?
I am looking at 4.5 inch x .25 inch wall pipe.

windtinker
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Joined: 16/01/2012
Location: New Zealand
Posts: 38

Posted: 02:28pm 13 Jun 2012

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Hi 434josh
The force in the wind is F=mv2. If the surface area is 1m2 and the volicty is 7m/s, thats 49N or 4.9kg. The tensile strength of mild steel is 365kg/mm. at 19m/s a pipe 1mm thick will shear in half.

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 08:10pm 13 Jun 2012

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There's a old post about wind loading. http://www.thebackshed.com/forum/forum_posts.asp?TID=252&PN= 15

You could expect half a ton of force acting against the turbine/tower in storm winds, if it not furling.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

434josh
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Joined: 13/06/2012
Location: United States
Posts: 10

Posted: 05:35am 14 Jun 2012

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Thanks. I plan to use furling, electrical braking as well as the ability yo tilt the tower down during severe weather.
My main concern is if I use round pipe what size should be used at the height and tower top weight. It will be a single pole with Guy wires.
Is a stepped pole better? Start at 6 inch dia and step down every 8 to 10 ft to a smaller size to keep the pole weight down?

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 02:47pm 16 Jun 2012

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I guess a stepped pole would be better, but its surprising how much compressive force a piece of steel pipe can take. For example, I have a set of car chassis stands that are made from 50mm diameter 3mm wall ( approx ) pipe, and they will support a couple of tons easily. So long as the steel pipe is straight, it can take a lot of weight. But as soon as it bends a tiny bit, kaboom! It collapses. Thats where the guy wires come in, to stop the pipe bending.

But I'm no structual engineer, which is one reason I've never posted plans for a windmill tower, I just dont have the know how.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

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