Tower Progress

[SparWeb]

I started installing the base of my tower 2 weeks ago.

Here are photos of the progress so far.

A 4' x 4' x 4' hole (dirty kid shown for scale only, he was removed before pouring concrete :^)

Concrete base (25 bags of redi-mix concrete later)

Aligning the first guy wire anchors.

So at this point I have 2 questions: Does anybody trust these screw-in type anchors?  I was surprised how easy it was to screw them into my clay soil.  Is that an indication of the load they can support?

Also, seeing how the west anchor (on the right) is 6" lower than the east anchor, should I dig around the east anchor to get it lower?  Currently it's on the hinge axis, so if it can stay where it is, the guys won't go slack or tight (theoretically).

640 pixels wide is the max pixel size for pictures on this board not 800 please keep pictures under 150k and under 640 x 480 pixels. thank you
Kurt

[harrie]

I guess it depends on how high the tower, and how big the turbine is. How long is the screw in anchor?? Does the ground freeze in the winter, if so they should be put in below frost line. I have used , and am still using some for one of my turbines, and have not had a problem. Now if i lived in the mountians where Danb lives, I would not use them, I have hunted in the Colorado Mountians, and have been in some of their winds, and am not sure if I would even put up a turbine there. Ha. Anyway, I think I would recomend a good concrete base at least for the top guys!!

[Flux]

I tend to agree with Harrie, in decent clay soil the screw anchors should be fine if you can get them in a decent depth. Bergey and others seem to think they are ok in the right soil, they are not effective in sandy soil.

If you don't mind the extra work I somehow have more faith in a good block of concrete for the main anchors but the screw anchors should be fine for the lower levels. The fact that they screw in easy is no reflection on their effectiveness , the area of soil you are trying to pull out is very large and a good block of solid clay will take some shifting.

Flux

[kenputer]

 Great job on the base and mixing cement is a lot of work when doing by hand as I also found out this past weekend.





 mine is also 4' feet deep and about 3' wide,it will be for a 3 legged tower about 35' high.

  The anchors I used are the same ones the power company uses to hold the power poles and are 3/4" galv.rod with 16" x16" dual plate on the bottom and buried 6' into clay soil so i think they will be plenty strong.

Ken

[thefinis]

Also, seeing how the west anchor (on the right) is 6" lower than the east anchor, should I dig around the east anchor to get it lower?  Currently it's on the hinge axis, so if it can stay where it is, the guys won't go slack or tight (theoretically).

Not sure which anchor is in line but I would get 2 side anchors and hinge in line and level if possible. The powerline screw in anchors should be fine if they are rated for your loads for your soil type in your area.

Guy anchors and guy lines need to be sized for the turbine. Duh! How are ya'll figuring the loading? Around here I have been wanting to use 90 mph as top survivable wind speed figuring anything higher and it is in God's hands. Once you get above 50 mph the forces just go crazy so 70 mph may wind up as the top survival rating. Some where you have to draw an economically feasible line.

Is the big deep base really needed? I thought that the base only carried the weight of the tower/turbine and the downward force of guy wire loading. Big heavy bases are needed for free standing towers for stability and counterbalancing but don't guyed towers get most of their stability from the guy anchors.

Finis

[SparWeb]

Ditto on that base, Ken.

Maybe I should get some of those anchors, instead.  The ones I put in have a 5" disc that screws in - much less surface area that what you've used.  Can you suggest a supplier?

Thanks.

[harrie]

Yes, the base anchor is only used for keeping the tower in place, but if you are using a tilt up tower, it has to be deep and large enough to hold the forces of rasing and lowering.

[kenputer]

I stopped and asked a crew that were pitting up some poles and they told me the electricial supplier where they get theirs.

 Another good source is mobile home sales,they have what they call hurricane anchors that hold the homes down in high winds,they have a duckbill plate and 5/8" cable ,just need a steel rod to drive them in the ground.

Ken

[DanB]

In most cases the base of the tower doesn't need to be that significant.  Even when raising or lowering, all the force is pretty much straight down on it.  We've made a few towers that just 'sit' on the ground (so long as the soil isn't soft such theyll sink) with a sort of large base made from steel (pipe usually) - and then we stake it down so it won't slide.  The base I made for my 20' machine is really somewhat overkill I think, and I never intended to put so much concrete there (we just had extra in the truck).

I was sort of amused up on Guemes Island looking at an 80' tower - made from 2.5" pipe with a South West Windpower tower kit.  The whole pivot assembly is stamped out from maybe 1/8" thick steel (maybe thinner) - that supports the whole tower and it pivots on a bolt (maybe 9/16 or 5/8") that passes through that thin steel.  Beneath that they had a ton of concrete.  It all seems to work well, but the concrete in the base was overkill.  I've seen a lot of towers where folks put more work/worry into the tower base than the guy wire anchors - it should be the other way 'round.

[jmk]

  I would think it would be a good idea to make a base footing that gets below the frost line if your in wet soil. A base footing that heaves 2" could put a lot of guy forces on the tower and anchors. Other than that I would agree with ever thing that Dan said.  

[Mary B]

Use the square footage of the blades as a solid disc and look at the tower company catalogs. Rohn used to have an excellent one online that would specify which tower and guy wire combo was needed. And the tower windload was already calculated into it so you don't have to figure that out.

[harrie]

Yes JMK, I agree with you 100 percent, the ground where I am heaves up and down from 4 to 5 inches, depending on the snow cover. Anyway, why not over do it a little, better safe than sorry.

[jmk]

 I wouldn't dig that guy anchor down. The one that is six inches lower will have to have some slack in it when tilted down. It will tighten up on the way up. Raise it with nothing on top and adjust the wires to hold the tower plumb. Then when it lowers one side will get a little bit of slack. You will have to figure tower as if it's six inches taller on that one when you figure out the length for the guy wires. That is if you use trig to figure them out. It's better to have the one side so it has just a little slack instead of more. You could unscrew the one side six inches and ad concrete. Then you will be best off.

[DanB]

Yes, probably not a big deal (I expect the goofy tower for my 17' machine has about 6' of difference in elevation between the side guy wires).

It is important in my opinion that the guy wires get a bit slack on the way down.

I notice from the picture that your side guys are lined up exactly with the pivot.  Better in my opinion would be to move them a few inches forward of the pivot (forward in the direction that the tower tips down) - that assures that they'll loosen on the way down and tighten on the way up.  First time you raise the tower leave the guys a bit slack - then adjust them after you get it up for the first time.  After that it should work well and you shouldn't need to make any adjustments when you raise or lower it.

[SparWeb]

Thanks for the info everybody.

I've ordered sturdier anchors from a supplier of utility pole hardware.

And when I put them in, I'll bear in mind what you said, Dan, about letting the guys go slack when it is down, and just tighten up when it is raised.  I can see that will save a LOT of adjustment, which could cause errors when this tower is raised/lowered numerous times.  I will do some "practice runs" with just the jin-pole on (gotta raise it somehow, might as well get the bugs worked out on that, instead of the real tower!)

Very appreciated.

[thefinis]

A couple of inches offset makes so much sense I don't know why it isn't mentioned in the tiltup tower sites. They all seem to recommend inline side anchors and base. Experience is often more practical than book learning but both are needed. Thanks Dan.

Finis

[thefinis]

rohn.net seems to be gone and I have downloaded the 2004 Rohn catalog but not finding the page you mentioned. Windstuff Ed had always recommended using the solid surface to allow for tower overloads when figuring. I was wondering what and if anyone was using for wind speed when figuring the wind loads etc for a tower.

Did run across this paper which is pretty good if you like to do the math.

http://www.kkn.net/dayton2005/KE1IH-Dayton-2005.pdf

I like Alton Moore's pages and loved his comments on towers.

http://www.alton-moore.net/index.html

Thanks MaryAlana hope you turbine is progressing well.

Finis

[GenCurious]

Here's a quick and easy anchor that I've used: Pick up a bag of concrete and a "t-post" from you local hardware store. Dig a hole to leave just the top of the t-post a few inches above ground level. With the t post in the hole, stab the bag of concrete over the post and let it drop. Add a little water and cover with dirt. Wait a few days to cure then make your attachment. You may drop the bag upright or horizontal. The objective is to make a "deadman" retainer that relies on the anchor and all the dirt above it to resist being pulled out. Other tips: roll the bag a few times before dropping to remix the concrete if it has settled during transport. One might even put a short piece of rebar in the bag of concrete to catch on the anchor plate of the t-post.

I'm new to this windpower interest and was actually hoping to first post on a discussion of waveform shapes - but I need to do more "homework" beforehand. So no, I haven't used this anchor on a tower. It was developed for a friend who's husky (as in sled not size!) dog kept getting loose (not to mention the chain kept rounding the square edges of the house). FWIW, the anchor was positioned further from the house, a small mound of concrete (formed with a disposable plant pot) left just a few inches of the t post exposed. A galvanized chain link tension band (connected to the plastic coated steel cable dog lead), was slipped on the t-post. A bolt and nuts fastened through a hole drilled in the t-post kept this tension band swivel retained. A little mix and match at the home depo, a little inventiveness and who needs those specialized do-dads?

a t-post:

http://www.mytscstore.com/detail.asp?pcID=8&paID=1043&sonID=350&page=1&productID=249
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