Homebrew surplus tower for 10ft Otherpower(s)?

[StorminN]

My friend wants to install a turbine (or eventually two) at his place. We've been looking at the 10' complete Otherpower machine.

My friend already has a surplus tower that's square (four legs), made of heavy steel (I'll get pics and measurements tomorrow), but I'd guess it's 6"x6" angle iron about 3/8" thick and the tower is about 8-1/2 feet square (footprint) and 25 feet tall. My friend's idea is to weld some more 6" angle iron and crossbraces onto the bottom of the tower and make it about 35 feet tall, then orient the tower so one corner faces west, which is the predominant wind 90% of the time. He'd then like to add two 10' or so poles on top, on opposite corners (north and south) so the poles would be at the same height, but about 12 feet away from each other horizontally... with the idea that he could install one turbine now and another one at a later date, and if the wind comes from the west 90% of the time, one turbine would not block the wind for the other very often.

So I guess my question to the board here is... is this crazy enough to work without guying it? I'm not sure how he's planning to weld the poles to the top of the tower, (webbing, etc.) but he has plenty of steel and a good welder at his disposal. He also has machines (excavators, etc.) and good concrete to pour a big foundation (or four). I really don't know how much force a 10' turbine in a full wind will put on a tower, so I thought I'd see what you folks think... if this would work, how big of a foundation it would need, and if it's a VERY bad idea to fly two turbines on the same big tower...

P.S. Yes, my friend knows that he'd be better off putting a turbine on an 80' or 120' tilt-up, but he'd rather use what he's already got for now.

Thanks,

-N.

[electronbaby]

no comment on the tower idea. It seems your friend knows just enough to get himself in trouble. (we all were there at one point or another).

Just a thought, (not knowing your mean annual wind speed, and terrain) Its quite possible to get much more power out of one ten foot diameter machine installed properly on a 100' tower, than you would ever get from two 10' machines at 35' height.

Plus, you normally would have fewer maintenance issues, because you would be above the turbulent wind. Im sure others will say the same.

All the time and effort (and steel) put into a 35' tower like you describe, could be saved, if you went with a taller tower. You will have less headaches, and more energy capture. (a win-win in my book).

[thefinis]

With more math and planning that tower might work for 1 turbine. It will not work for 2 turbines on 2 poles same tower. Bad idea.

Here is a link to a good thread about towers 4 sided and others.

http://www.fieldlines.com/story/2007/7/16/3450/63291

Not wise to try a very big project like a 10' turbine without at least knowing the forces you are dealing with and what is needed to handle them.

good luck

Finis

[wooferhound]

Stories about 2 wind generators on 1 tower

http://www.fieldlines.com/story/2006/8/29/145422/729

http://www.fieldlines.com/story/2005/10/2/132556/641

http://www.fieldlines.com/story/2005/8/12/222314/250

http://www.fieldlines.com/story/2004/2/6/13167/92129

[scorman]

sounds like you have an exceptional 25 foot pedestal base for tiltover tower, but that  does NOT necessarily mean it has to be guyed (but I prefer to guy).

Dan Lenox has a 17 footer on top of an 80foot tower

In answer to your original question, the force of a 10 footer is probably less than 100lbs lateral force on tower at 25mph WS.

here is one of several threads:

http://www.fieldlines.com/story/2007/7/26/21922/9452

I have posted this pic before:

you are looking at a 65foot tiltover, whose base is two 6inch well pipes sunk 10 feet down and the pivot is at 20 ft.

If you can fabricate/scrounge a 50 foot pipe or lattice tower, it could be perched on top of your base and pivot at 25 feet up

send me your email and I can show you some pics of a square base pedestal

that looks like this:

Stew Corman from sunny Endicott

[thefinis]

Maybe I should expand my reasoning a little. Woofer is right there are some 2 turbine towers out there but not with big turbines and not configured as stated in the opening post.

add two 10' or so poles on top, on opposite corners (north and south) so the poles would be at the same height, but about 12 feet away from each other horizontally.

You have a 25 ft tower that is going to be extended to 35 ft by adding to the base. Next you want to add pipes/poles extending 10 ft up(?) from the main tower top with the top of the pipe ends 12 ft apart. You are going to mount a 10 ft turbine on the end of each pipe. So you have a turbine mounted 45 ft in the air with the mounting out passed the tower base by a couple of ft. The pipe becomes a lever that is 10ft higher than the main tower and 6 ft out from the center of the tower. The turbine blades will actually extend these figures by 5 ft so call it 15 ft above main tower and 11 ft from tower center. Usually the four sided towers are not really designed to withstand a lot of twisting force.

With this configuration furling also becomes a real challenge to engineer. I am not sure if a 5 ft long tail will work at all on a 10 ft turbine and if you are not going to pivot to face the wind or furl then it will have extreme amounts of force working on it.

This should be a good 40-45 ft tower for a single turbine and with proper footings etc can handle a bigger turbine than a 10 footer.

Take care

Finis

[StorminN]

Hi guys,

Thanks for the replies. I finally got over there and took a couple of pictures...

Here is the surplus tower, sitting on its side. My friend has plenty more steel to add length to the legs and add more cross braces.

and here's one of the anemometer, facing the predominant wind. It's currently on a 25ft pole. Hopefully we'll get it on at least a 40 foot pole soon. Those trees in the distance are about 500 feet away. In between is flat farmland.

It's been especially windy the past couple of days, an average of 18mph at 25ft elevation, and gusts to 28mph. From what I've read, the mean wind speed for this area is 5.02m/s, or about 11mph.

Thanks,

-Norm.