Anchoring a windmill on rock

[mtblah]

When we lived in Temple we had a fence builder come in and drill fence line holes , He had a special sized drill so a 2" fence post could be tapped in and boy were they solid . twenty years ago the holes were $10 each , well worth the minimal cost .
or rent a hammer drill & buy a bit , stand bottom section of the tower & drill exact holes .

[CTXmiller]

I think I’ve posted this before at some point, but my brother in law installed a B602 on a 27’ near Hamilton, TX a year or so ago. Hamilton is mostly rock as well with some top soil on the rock, but not enough soil to dig in. He used concrete anchors and hinged stainless plate. The stainless plate was 1/4” and he bolted it to rock that was underneath it. I wasn’t there on the install/erection of it, but for some reason he then put a yard or two of concrete under it, covering the anchor plates…a hair overkill.

[Wayne]

Better safe than sorry. They say 40-45 MPH winds are headed our way in the morning. So there are going to be some windmills humming in Texas tomorrow.

[JBarker]

Josh,

Great question!!! I'm not claiming to be an expert, but this is what I have learned by trial and error in the last four and half years installing windmills all over Texas for clients. TEXAS IS ROCKY and WINDY!!!!

We just installed this 8-27 windmill in Burnet, TX. Attached are some recent photos how we do windmill installations in the Texas Hill Country. My advice would be to not shortcut digging holes the correct depth. The Aermotor Co. recommends you dig your footing holes over 4ft in depth for a reason. We rent two mini-excavators, one with a 12-inch rock digging bucket and the other with a 500lbs rock breaking hammer. The reason we use a 12-inch bucket is it allows you to reach the bottom of your hole. As you dig in the limestone rock, the hole will narrow, and you will need a smaller bucket to scoop out the rock or you will have to get in the hole and scoop it out by hand. I run two mini excavators at the same time because its quicker then switching between implements. Trust me, it's worth the extra cost to have two running at the same time. One person can be breaking rock and the other scooping it out. It took my windmill crew 6 hours last Saturday to dig four footing holes 4.5ft deep. Do it correct and you and your client will sleep better knowing you followed the factories instructions. It's a lot more work, but I don't have to worry the windmill will fall down in the next Texas storm. Another idea, look for a local foundation contractor that works in your area of the state, a lot of times they will have someone they use that will bring out heavier backhoes (excavators) that will chew thru the limestone faster than a mini excavator. I have a local guy in Fredericksburg, TX I use to dig my holes, he is faster and cheaper than me, plus he is used to digging rock in that area.

We use the factory anchor post w/feet. We overkill and use 14 bags (50lbs) of fast setting concrete per hole. This gives me 2,800lbs of concrete holding the windmill in the ground plus all the rock and dirt goes back in on top. I know this sounds like overkill, but it makes me sleep better and I haven't received any phone calls about windmills falling over yet. Hope this helps. Enjoy the pics below.

Jerry Barker

[JBarker]

Some more pics... Jerry

[JBarker]

Josh,

Here are some recent pics of Texas windmills that fallen over from lack of proper anchoring. Thanks.

[mtblah]

Jerry , right on , those photos explain why we overkill , yah the wind does blow ocassionaly .
I used 4 bags per hole , 5 ft down & rock on to of concrete + foot of dirt to grow the grass
27 ft tower

[JoshL85]

Good idea, I have a skid steer but no rock but, I’ll ask around, thank you again!

[JoshL85]

Holy crap, yeah I wouldn’t want it to fall being that close to the house, I’m gonna see about a rental, thank you guys a lot!

[JoshL85]

This has been so much help! The pics explained a lot, Thank you!!

Josh,

Here are some recent pics of Texas windmills that fallen over from lack of proper anchoring. Thanks.