10 ft; tower @ 60 ft.

[freejuice]

Hi Everyone,

 I need a good idea on how much to anchor this 60 ft down with:

 I have 4 inch diameter sch 40 pipe; 3 sections. At each junction I have a piece of sch 40 3-1/2 ( 2-1/2 feet long) inside of the 4 inch pipe, with 5/8 cross bolts going completlety through each section, above and below each junction.

 While is has a little play between the inside vs. the outside, about .080 thousandths I will also add  some of those Morris type of outside couplings to help keep things rigid.Maybe I might go with a 14 footer max on this tower at a later date.

The guy wires are 1/4 inch cable in the typical north, south , east, west setup. There will be a set of wires about 8 below the towers top, and another set just above the first section. Hopefully using the same anchor point for each set of wires.

I was wondering how much concrete to use at each anchor point? A little while ago I was asking  about ground anchors and Volvo Farmer was having some success with these, appaently his held up so well that even his stator let go in the high winds before the tower did...so that builds my confidence "factor" a little bit more in regardings the ground anchors, which this forum fell oddly silent over )....( a kind way of saying to this newbie..."Uh, I dont think you want to do that" )

However if I go with concrete, at each How much should I pour? Is there a "quick and dirty" calculation that would give me a weight of the concrete to the possible pull strength on the cables

I recently saw a youtube where they were installing a 5kw wind generator...the baldes must have been about 15 feet and the tower was about 50 ft tall ( my best estimates) and they essentially used 5- 55 gallon drums full of concrete, one for the tower base to anchor to and the other four with loops installed for the guy wires to anchor too.

  They simply dug a hole with a backhoe dropped them in upright and then tamped the dirt in around it.

 Any ideas on how much concrtete to use at each point?

 Thanks,

 Gavin

 

[Volvo farmer]

Most plans I have seen recommend a set of guys every 20 feet with this type of tower. You might want to add another set of guys to your plans.

This is my own personal opinion, and might not have any basis in fact, but it seems to me that if a little 6" triangle can be rated at 5000 lbs in hard pan soil at 40" deep, that the earth itself can be used as resistance to pull out, rather than pouring tons of concrete in a hole.

I can't tell you how much concrete to use. However, I wonder if you couldn't use a lot less if you put it really deep and in a shape that used the earth itself to resist pulling out, like maybe in a trench perpendicular to your guy wire.

If you get this tower up and going, please post a story about it as I would also like to make a 60' tilt up tower, and I'd like to hear how you did it, your successes and things you would do differently.

[bzrqmy]

I think the 55 gallon drum for anchros is a bit overkill, but I am sure they will never come out of the ground.  Obvioulsy, it depends on the soil type. I used 3' screw in earth anchors,  I welded several 12" lengths of rebar  to the anchor.  The screw in auger things serves no purpose other than to grip the 160 pounds of concrete I put in each hole.  I added a bit more reinforcement and concrete to the anchor that I use to pull my ginpole.  I have trouble lowering my tower because my anchors are lower than the pivot point on my tower base.  I actually added two new anchors further from my pivot pin, but that did not help.  I then busted up a couple inches of the conctete and cut the loop below ground level.  I didn't even think about doing a destructive load test to see just how strong this type of anchor is.  If I were to do it over, I would have welded another 18 inches of rebar to make my anchor 48", and left enough sticking out fo the ground to be higher than my pivot point.  This would also put me below the frost line.  I am not sure if frost heaving will play a role here or not, could make my guy wires go limp.  I usually do a weekly inspection on all guy connections, which reminds me, better get out there. As for having only two sets of guys for a 60 ft tower, I too would think you will want one set at each coupler. The tower is going to skew a bit at each coupler, you will need to compensate bu adjusting the tension on the guy wires to make it look straight.  I use turnbuckles to adjust the tension.  Not sure what you guys use for turnbuckles, but I bought the heaviest thing I could get at the Tractor Supply, $26 bucks each x 8.  By turnbuckles are by far the weakest link and will fail before my anchor will.  I run an extra length of 1/4" cable through the anchor length, through the turnbuckles to keep it from loosening, through the cable thimble of the guy wire, and back as a safety cable in the event of a turnbuckle failure.  Good luck and let us know how it turns out.

[imsmooth]

See this http://www.mindchallenger.com/wind/wgpage11.html

I took 4' long earch augers with a 6" screw and put a 12" brake rotor at the bottom.  I then poured two bags of 4000psi crack-resistant concrete on them.  The earth and some rocks went on top.  I have had no problems with my 42' tower.

My anchors are 20' away from the tower.  If you move your anchors further out the tension will be even less.  You could also go with deeper anchors (5').  With the earch on top of my 12" plate the shaft will break long before they get pulled out.

You might also want to consider this method for linking your tubing sections:

http://www.mindchallenger.com/wind/axial2.html

[freejuice]

That was a keen Idea to use a 12 inch rotor to help anchor the concrete.

 Now you folks have me wondering and I must admit there needs to be 3 guys for each anchor point...thanks!

 Since I'm now back to leaning heavily towards duckbill or arrowhead anchors....I was wondering about the three guy wires at each anchor point. by using two of these earth type anchors for each of the three cables... I could space them out enough to aviod disturbing each other but the loops from the cables could meet together, thus doubling up for the three guy wires....maybe in a pattern like a " -< " ( The horizontal line being the three guy wires and the "<" being the seperate anchors, with the cables meeting together, to support the three guy wires

 What say ye the jury?

[SparWeb]

That only works in theory.  What actually happens is it becomes nearly impossible to tighten one guy wire without loosening another, and you end up with some cables nearly slack unless you're ready to spend a realllllly long time fiddling with it.

I think it's hard to recommend which way to go, when it comes to anchoring a tower, without some experience with the soil you have.  I just happen to be lucky to have a layer of thick (dry) clay to put screw-in anchors through.  Turns easily enough when I wet the hole and I actually have load tested the anchors to 2000+ pounds (after it dries, of course).  The 6" anchors that I got are rated for up to 6500 pounds in class 5 soil.  Look up Hubbel Chance, if you're interested in them.

Your mileage (or poundage, that is) may vary.  Try talking to people who install them near where you live (just phone a telephone or electric utility, you never know).  Get as much info as you can from the people who supply the "industrial" types of earth anchors.  Don't buy screw-in anchors from farm stores or hardware stores unless they look absolutely gigantic.  

If you have a soil that does not let you safely use screw-in anchors, then you are much better to use concrete.  This way you are in control of the weight and bearing area the anchor can apply to the soil.  For really soft marginal soils, you may need a large augered hole filled all the way up with concrete.

A good example of "how-to" build a tower for a wind turbine can be found on the Southwest Wind power website.  You can download tower plans for various sizes of turbine and different heights.  Just bear in mind that the Whisper 100 is a REALLY small wind turbine.