Inexpensive tower material

[makenzie71]

I'm certain I had already made a thread talking about this stuff but can't find it :/

Since I started posting videos of this stuff I’ve had a couple people ask me about what i’m using for tower material, and it’s something i asked about quite a lot prior to setting the things up.  Didn’t get a lot of feedback...which is reasonable since it seems not many people have tried it...I did get one fellow go so far as to tell me if I did it I might kill my neighbors' children.  Which was neat.  I did it anyway.

This stuff is usually about $20-30 USD for 30-32ft stick in my area, usually has couplers and is threaded, and is plenty strong. My taller one is at 25ft to the hub. I’m going t9 do the next one at 32ft and, if that one does well, i’m going to do the next at 40ft.

https://youtu.be/W9efli270H8

I honestly feel this stuff (3 1/2") would work great at about 60ft with guys.  I talked to a few field workers and they've told me they can sometimes when they pull the stuff up they have to stand it up two or three sticks at a time and it supports the weight (until they can get them laid over and cut apart)...but I would be concerned about putting much weight on top of even two stuck together.  If I can get them to hold up to 40ft it's still going to be braced about halfway up.

[wbuffetjr1]

I was thinking about this exact thing. The pipe I have has really heavy duty bells on the end for the threaded joints. We have built a gate/fence from it as well as a big carport. I love the stuff.  I think it would make an easy tower. I would like to go three sticks high. I know it would have to be guyed.

[makenzie71]

I think so long as the turbine isn't extremely heavy...100lbs or so...three sticks would be doable.  My biggest concern would be getting it up without the pipe buckling.

[MattM]

It is much heavier tubes than the popular radio towers made from aluminum.

[makenzie71]

When I asked on Reddit I was advised to look at masts made for antennas and such...but it was teh same group of people that told me using oilfield pipe was going to maybe kill my neighbors' kids.  This stuff is very heavy and rigid...I think it's going to serve my projects very well.

[SparWeb]

Hi
I watched your video (the ice formations are funny ) ) but there's something important that I couldn't see.
It all sounds like schedule 40 sizes, and in fact I used schedule 40 pipe in my tower, too.  One thing to beware of is the grade of steel in the pipe.  You want it to be a structural grade, like ASTM A53 or A106.  If you're getting pipe and you can't read a specification printed on it, you don't have structural pipe.  Without that spec, the pipe can be so bad that you can fracture it by striking it with a hammer.  That kind may be OK for plumbing water, but no good for your tower.
If the pipe you buy has these specs, then you can work safely with them and get good results doing things like machining/drilling/welding parts.

As for raising towers, all I can say is don't work beyond your knowledge and confidence.  Because I've been on the Fieldlines site for many years, I've seen towers that have collapsed and been dropped during raising or during storms.  If you're not willing to learn everything you need to know to do it safely then you shouldn't be doing it.  Now, I don't know if you're the chief engineer at Rohn Towers Inc. or not, so I hope you can appreciate that the only reason I'd take a firm line on this is because this is where your safety is at stake.  If you're doing the work it takes, then the public safety announcements can stop.

[makenzie71]

It's not really structural tubing...it's bought off oilfields and sold as structural tubing.  The grading is different.  They don't have the grading stamped on them like you would get with structural or machine grade stuff from a supplier...but all the outfits here use G105 or better so it's a pretty safe bet that it's G105.  The crummiest stuff you can generally find is E75, and even that is fairly robust (75k psi yield).  Yield on A106, just as an example, is about 30k psi.

Wall thickness is also heavier than sch40, but sch40 is probably about as close as you'd get.  Sch40 with an OD of 3.5" would have .2" walls.  Wall thickness on this stuff is .265"

Using this stuff is a bit on the side of new territory...it's been made into plenty a shop and flagpole but not a lot of turbines are sitting on top of vertical sections of the stuff.  I'm trying my best to be as safe as possible, and I think I'm taking an excess of the necessary precautions, but that's why I'm trying to go into real heights in small increments.

I appreciate the concern

[bigrockcandymountain]

That is great stuff.  We call it 3 and a half inch tubing. The smaller 2 7/8 tubing is more common. It is hung down deep oil wells with pumps etc mounted on it.  It is seamless and much better steel than regular mild steel. 

You are on the right track working your way up in height.  My tower is also oilfield scrap.  It is 7" piling cutoffs from a compressor station and the stub at the top is a 4" od spent perforating gun.  All the explosives are gone.  It has about 1/2 wall thickness and a nice machined top for the bearing to sit on.

It is good to use what is cheap and available.  Thanks for your work on those chinese turbines.  It is fantastic information you are providing. 

[SparWeb]

All the explosives are gone.

Whew!

Mak,
This sounds much better than it did at first.
Since it's buckling that usually limits what a tower can do (and the cause of most collapses I've ever seen) then this sounds like good stuff if you treat it right.  If you can put beefy guy wires on it at 20foot intervals then you're in good shape.

[Adriaan Kragten]

The advantage of a free standing tower with no guy wires is that it has a low natural frequency. The rotor of a wind turbine always has some imbalance and if the rotor is spinning with a rotational speed in rev/sec which is equal to the natural frequency of the tower in Hz, the tower will start to resonate in its natural frequency. If the natural frequency is low, this will happen at a low wind speed for which there is only little energy in the vibration. At higher rotational speeds, the vibration will stop automatically. Adding guy wires, results in a strong increase of the natural frequency and now the resonance may happen at a wind speed for which there is much more energy in the wind and so the vibration can be disastrous.

In my public report KD 582, I give the strength calculation for a free standing tubular tower and also the calculation of the natural frequency. The natural frequency depends on the length, the stiffness and the mass of the tower but also on the mass of the head and rotor placed on top of it. The natural frequency can be measured easily by connecting a rope to the tower top and by pulling pulsating at this rope.

The bending moment and so the bending stress is maximal at the tower foot. So at this place there should be no welds. The tower as described in KD 582 is clamped in between two blocks. The lower block can hinge in between the foundation strips and therefore the tower can be lowered easily.