Guy anchor weight?

[fabricator]

Is there any formula or way to make an educated guess on guy anchor weight? It'll be for a 17' mill on an 80' tilt up tower, a cubic yard of concrete weighs in the neighborhood of 4000 lbs.

[cardamon]

You will need the thrust generated by the wind mill, and I don't know how to approximate that, but I am sure others do (Manufactured wind mills usually have a thrust spec but if you build your own you are out of luck for that route).  Once you have that figure, the force on the anchor would theoretically be: horizontal turbine thrust/cos(x) where x is the angle of the top guy wire from horizontal.  Of course you want some fudge room in there, and the frictions and resistance of the surrounding dirt will help with that.....

[cardamon]

....re-read and though probably obvious, felt the need to clarify, what I said only takes into account forces from turbine thrust - thought that was what you were asking for some reason.  Of course you will want to take into account guy wire tension, some tower weight, force from wind hitting tower, severe weather events.  80 foot, 5 inch pipe towers for that size turbine that I have seen usually use about a yard of concrete at each anchor. Hope that helps some.

[fabricator]

It does, I was leaning toward 1.5 yards per anchor.

[TomW]

fabricator'

Bergey has a great installation quide in PDF for their tilt up towers of all sizes. Includes guy cable sizing and anchor information. I think I have a copy in my files. Let me go see. Ahh, found it:

http://www.otherpower.com/images/scimages/4/XL1.Tilt.IM.4.pdf  

It is 526K file but well worth a read.

Hope that helps.

Tom

[fabricator]

There is a lot of good info there.

[fabricator]

I just found a really useful document from southwest wind power on an 80 foot tilt up tower, pretty much all the info I need.http://www.windenergy.com/documents/manuals/0033_REV_E_w100-200_80_foot_tower_manual.pdf

[SparWeb]

A great manual, but I wouldn't use a "duckbill" anchor, especially not for a 17' mill.  The SWWP whisper turbines are tiny compared to the machine you're building.    

A screw-in anchor can be un-screwed if you need to re-position it and has a much bigger bearing area on the soil.  Phone a company that supplies utility contractors with pole-anchors and get the specs for their 8" anchors.  They can give you load ratings for different soil types.

[fabricator]

Oh no, no screw ins or duckbills, it will be strictly concrete, and right now it looks like one yard/4000lbs per anchor should be enough with some safety factor