Any idea on amount of concrete for 50 foot tower?

[360GUY]

I was given a 50 foot homebrew tower that is made out of a steel lamp pole.  It is design to be free standing and has a tilt over base.  I want it to hold up two Air 403's and some wire antennas for my ham radio hobby.  However I'm kind of at a loss as to how big of a hole to dig for it's base.  I've been told as much as 5 cubic yards of concrete and as little as 1 cubic yard.  No real luck on finding any websites that might be of help, so possibly some of you wind guru's might be able to give me some ideas.  

Thank you!

George

[windstuffnow]

  With guy wires its pretty easy to calculate the amount of concrete you need for the footings.  A simple leverage formula will do.  With a free standing tower it's a bit more complicated.   50 ft tall with one air 403 can reach as much as 500 lbs in a 70 mph wind.  With 2 of them up there your looking at close to 1000 lbs of force.  At 1000 lbs there would be around 50,000 ft lbs at the base of the tower.  Chances are that 5 yards wouldn't be enough to hold it, if the pole itself is strong enough to withstand that load.  Since the air 403 don't actually furl the towers have to be fairly strong to hold them.  5 yards of concrete would be about 18,000 lbs but would depend alot on the depth it went down.  I don't have the formula handy for free standing poles but I'll see if I can dig it up... You may want to reconsider using both air 403's on one pole.

Windstuff Ed

[wdyasq]

George,

That is a question with a lot of variables.  Soil conditions, depth to bedrock, design of the hole and a half dozen or more to start with.  The wind conditions, the size of the antennas and a few more questions could change the first few.

Ron

[monte350c]

Hi Guys,

For the basic idea on free standing poles try this:

http://www.asme.org/education/precollege/esp/act5sr1.htm

Just substitute in your own numbers...

Ted.

[Chuck]

See page 80 of Michael Hackleman's "The homebuilt wind-generated electricity handbook". It gives the basic concepts pretty well. In fact, buy the book if you can find it. Great info on towers and the old 20th century wind generators.

Chuck

[DanB]

Hi Ed - perhaps im wrong, but I thought manufacturers guidelines suggested figuring for a maximum thrust (on the pole) to be about 80 pounds for an Air 403.

If 500 pounds (or even close) of thrust from a 403 was possible, I can tell you - every single 403 installation I've seen up here would be bent over!