42 ft pipe tower question

[Volvo farmer]

I'm beginning the process of building a tower like you see here

Otherpower tower page

So.. a question to anyone who has built this type of tower: How to you tell if the pivot is square to the tower? I used a 8" carpenters square but it seems to me things could get quite off at the end of 42' with only a small error in squareness. Am I worrying about this too much? I suppose I could always shim the base some if things looked wrong once up. Right now, things look pretty square but I wanted to ask before welding it up.

[nekit]

You could use a digital level.  Measure the tower and the pivot and make sure they are at 90 degrees.

[imsmooth]

You can draw a straight line on the pivot using the square angle and use the line to line-up several feet of string over and parallel to it.  Next, run  50' of string perpendicular to this one, and running through the center of the pivot, using the square angle.  You can line up the 42' pipe with this and you should be dead on.

There will probably be a bit of play when you raise it and you can adjust your guy wires to make finer adjustments.

[bzrqmy]

I built mine 42' tower with 3" schedule 40.  I was amazed at how much flexability there was in the pipe.  I assume you will be using two sets of guy wires.  I used a torpedo level to square up the first 20 feet of the tower with the lower guy turnbuckles, then adjusted the top guy wiares by eye from a distance, and from standing at the base of the tower looking up.

[Volvo farmer]

Thanks everyone for the responses. I'm in brand new territory here. It was especially helpful to read that guy wires are used to plumb sloppy towers. Having never erected one before, I never even thought of that.

I'll likely post back as I get further along here. This is daunting, but kinda fun, especially with the help of this forum. Thanks again!

[tecker]

Stand it up and use a plumb bob .

[ruddycrazy]

Hiya Volvo,

          Here a suggestion out of the box.... grab a tube that will fit thru the stub section with a neat fit the simply use the 3-4-5 rule. You'll need a 6 metre pipe, measure the centre accurately then measure 4 metres on the tower, the hypotenuse should be 5 metres each side if everything is square.  

Cheers Bryan

[SparWeb]

Hi Volvo Farmer (have your 850's sprouted yet?)

I built a tower based on Otherpower's guidelines 2 years ago. It's in my files and I posted some diary entries about it, too.  http://www.fieldlines.com/story/2007/6/28/54520/9777

Feel free to learn from my mistakes!  :^)

Squareness at the base isn't crucial, because as you say, it can be shimmed later.  Your tools are fine.

I chose to bolt some parts together because it allows me to disassemble it.  

...Which was handy when I smashed it to the ground this spring!

It's back together now.

[freejuice]

Hi Steve,

 That looks Like a good design....how long was your jin pole?

 Thanks,

 Gavin

[SparWeb]

The gin pole is 21 feet.  The whole tower is 45 feet tall, so it's just short of the 50% rule.  It just fits inside the guy wire diamond, so I don't have to take the gin pipe off to get the guy wire attached.  The gin pole just stays in place until I need it next.

I have a winch installed now (surely I'll make a diary entry about that soon) but I haven't yet put it through its paces.

[SparWeb]

Hey VF,

Did you ever get any bites on your contest?

http://www.fieldlines.com/story/2007/10/10/52711/090

I always wondered if anyone would get over the "sarcasm" and attract a real bidder.

[Volvo farmer]

Thanks. That's very helpful. I'm planning on welding everything, including guy attachments. My jin pole will be about 20 ft so I imagine we will have similar experiences raising and lowering towers.

I read something in here a month or so ago about attaching the gin pole at slightly less than 90 degrees so that it stays off the ground when the tower is raised, then attaching it to the anchor. Did you contribute to that conversation? I will be attaching my gin pole to the pivot next.

[dlenox]

Volvo Farmer,

It should not be that critical, but get as close as you can.

From what I understand it is much more important that the pipe you are referring to should have an ID that is at least 1/2" greater than the pipe that it rotates over. This will allow it to compensate for any mis-alignment when you go to raise/lower the tower.

Dan Lenox

[SparWeb]

I have a photo that would illustrate perfectly, but it's on my computer at home and I'm at work (lunch break - not goofing off!)

It is true, having a gin pole at about 85 degrees is better than 90 degrees.  There are a couple of reasons.  First, the gin pole won't hit the ground when the tower is nearly all the way up, it will stay a foot or two up.  Now you can take it off at your convenience, not during the raising process while 1000 other things are going on at the same time.

Second reason is a little esoteric, but I believe it's got someone in trouble before, so I'll try my best to explain it:

A gin pole is NOT a lever.  A gin pole is a "column" under compression.

Anyone who thinks a gin pole is a lever may argue that when it fails, it bends.  Yes it can bend, but that is due to compressive buckling, not a bending load.  Or because the cables aren't attached properly.  You need to have some respect for that compression load pressing down on the pivot joint.  If the gin pole is attached in the wrong place, it can actually press DOWN on the base of the tower, preventing it from raising as you pull.  I think this happened to "behoof" a while ago, but I wan't sure.  It doesn't matter because he made many changes and then found an engineer to look it over in person.

If you want the gin pole attached to the tower, either you want the gin pole to NOT interfere with the tower's pivot at all, or they share the same pivot but must not flex relative to each other.  Another way is to mount the gin pole on a pivot just in front of the tower's.  I wish I had done something like that, as a matter of fact.

Another thing to think about is that once you start pulling on the cable, the wires stretch.  The angle between the gin pole and the tower opens up a little.  Not much, though.  It usually doesn't matter, but in Behoof's case, I think it made his situation worse.

(Sorry Behoof, for making an example of you, but I think we can learn from your experience, so thank you for posting about your troubles)

It's coming a bit late, but here's some reading material you might appreciate:

http://www.sparweb.ca/4_Tower/Monopole.html

http://www.windenergy.com/documents/manuals/0028_REV_E_50FootWhisperTowerManual.pdf

SWWP seems to have re-vamped their website, so I'm off trolling for new information.  Bye!

[Volvo farmer]

This is probably the most helpful thing I have read since beginning this project. It makes total sense that the gin pole is not a lever to me now. I wonder why on the Otherpower page, they use a gusset between the gin pole and the tower if the only loads on the gin pole are compressive? Thanks a lot for that SWWP link, It helped me clear up my mind a lot. I have been fretting about anchors a lot lately. I have some 6" "duck bill" type anchors but was almost afraid to use them until I read that. Now, I'm ready to jackhammer them into my clay and call it good.

Your comments have helped me a lot Steven, I really appreciate it.

 

[SparWeb]

You're welcome!  

The one thing the "gusset" does on the gin pole is to resist the buckling that could come from the compression, which isn't a bad thing.  I decided to put one on mine after seeing how things sway about as I raise it.  It helps a little with the "bounciness", when everything is hanging from the trapeze!

Please report your experiences with the duck-bills, after everything's put together.  Some people like them more than others, but I have never used them personally.