Tower Anchors

[Bigwheel]

Hi again everyone,  I've been pondering this since last fall and thought I'd better start looking back into this.  I got the idea from a neighbor of mine who has a 100' rohn 45G tower with a early 80's 1500 series Enertech on top of it.  His tower has been up since the early 80's and still standing.  Anyhow, the tower is resting in a couple yards of concrete and the anchors are those Utility Grade Screw in anchors in "SANDY SOIL".  Like the one's sticking out of the ground near utility poles. I like the option of spending money on something and being able to take it with me if I were to move.  From what I've seen the norm here is using reinforced concrete anchors.  I would like to get a little input on what you might happen to think or personal experience.  I, like most here are looking for ways to keep the costs down.  Now, not everyone will have sutiable soils to work with an option such as this but it's another possiblity.  From what I've been able to dig up, and it's not much, I'd be looking at an auger with a 10" diameter helix with a shaft of 1 1/4"'s.  Oh, the lenght is an overall of 96".  With those specs. I'd be tempted to make my own.  At least try one to see if I could get one down that far.  As far as my tower goes, it's a custom tilt up that I'm in the process of fabing up when time allows.  Height is 80', gin is the standard 40' with my guy wires anchored on a 40' radius in four directions. Thanks again for your input and look forward to talking about this one.  Chad    

[Volvo farmer]

I bought enough of these a while back to do my eventual 40'tower. I haven't installed them yet and have no idea how the're going to work out. I'm personally afraid of hitting stones with mine but with sandy soil, this might not be an issue for you. Oh.. and you ain't taking them with you when you go either.

http://www.americanea.com/category/10/Military_Anchors.htm

[Bigwheel]

Hi Volvo,  Great looking product didn't know those where avaible.  There simular to the duckbill style I've seen out there.  I figured you'll never get them out of the ground either.  Here's a link to the one's I was talking about.  Thanks for the like and the info.  Chad           http://www.allmetalssupply.com/earth_anchors.htm#EARTH%20ANCHOR

[Chagrin]

A 4" diameter earth auger has a pull out force over 2000 lbs. If the cable will be set 40' from the pole and (estimate) 70' up it (hypotenuse 80') that gives you a lateral force about 1000 pounds?

Never realized how rusty my trigonometry was.

[SparWeb]

My tower seems to have the same proportions as yours, but it's 40' tall.

I have a 8 foot diameter mill on it that picks up about 300 watts, prop load is roughly 7-800 watts when that happens.  It's seen some 70-80 kph wind gusts so far.  Absolutely no problem with the utility screw-in anchors I used.

Get the ones with the "knuckles" on the eyes to keep your shackles in place, if you decide to go that way.

There is a certain point where a screw-in anchor won't be appropriate for this project.  If your mill is greater than 12', then you had better work out the numbers carefully.

[suitep123]

Howdy:

So, if as stated above, you are 40 feet out and 70 feet up, the hypotenuse is approx 80 feet.  Next step, how do you calculate, or what is the equation to figure the lateral force?

We're building a 30 foot tilt up, going 15 feet out - calculating the hypotenuse is the easy part - still need the lateral force figures.  We're trying to figure out anchors now.

If you could shed some light on this I'd really appreciate it!

Pauline and Bob

[TomW]

P&B;

Be nice if one of our math & computer whizzes would slap together a force calculator for this part of the subject.

Way beyond me but I know a couple guys who might pull it off.

I did learn this in college physics but thats been long ago and I wasn't interested much beyond a passing grade. So here I sit [as predicted] 30 years later wishing I had been interested then.

The clarity of hindsight is amazing.

If I remember, I will see if I can get someone to volunteer to knock together a chart or spreadsheet or something for the basics.

I do know it takes more to lift it pulling on a line over a gin pole than it takes to simply lift it at the attachment point. How much more requires cosines and / or sines of angles and some multiplication or so it seems.

Good luck with it.

Tom