New Tower

[dloefffler]

Tubing question.

Schedule 40 pipe, 2.5" has tensile of approximately 60K and yield of 35K. What is the reasoning on using tubing?

Would you be wiling to post a picture of the fixture?

I am sure you thought of it and given the amount of work, I can see an obvious reason to avoid it, but did you consider tubing notched rather than angle iron?

Thanks as always. I am in the middle of building a frame for my solar panels with 3" pipe off a stamped drawing. More work than it looks from the pictures.

Your generosity in sharing experiences is very much appreciated. I hope you have more rain than us, beans are holding their own, corn in some areas is fading fast or gone. Tough year for the crops.


Dennis

[fabricator]

The crop insurance people are gonna be hurtin around here, unless you are irrigating it's a total crop failure, most of the corn didn't even make an ear so it's not even worth chopping and bagging.

[ChrisOlson]

Schedule 40 pipe, 2.5" has tensile of approximately 60K and yield of 35K. What is the reasoning on using tubing?

DOM tubing is stress relieved and annealed.  It has much better fatigue resistance than schedule pipe and will easily handle millions more cycles.  Unlike pipe, mechanical tubing is measured on the OD and has a precise ID with no welded seam, allowing slip fit of the columns to join sections together without using bolted flanges, aka Rohn SSV.
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Chris

[spottrouble]

Thanks Chris, excellent work! Went back and looked at pics, guess my eyes were fooling me. A pic of that jig would be nice, I'd have to kick all the race cars outta my shop to build something like that.  Got to ask, how hard was it to get an engineer to sign off on that design? Did you do all the calculations and they just double checked your work, or did engineer say this is how it needs to be built?

Sparweb
I'd be interested in the calculations you did to determine if that tower was suitable. I've built a lot of stuff over the years, when in doubt build heavier has worked for me (no failures that I know of ), yet I know thats not really the best answer for all applications.

Kristi

[Mary B]

5w refers to the top of a Rohn tower.

[ChrisOlson]

Got to ask, how hard was it to get an engineer to sign off on that design? Did you do all the calculations and they just double checked your work, or did engineer say this is how it needs to be built?

When I build the next tower in early September I'll take some photos of it being built on the jig.  I'm getting back to full-time fishing for the rest of this summer   

I did all the calculations, design, drawings, and prepared stamped specs for turbine loading.  I used TEP to verify and certify the tower, and it cost roughly $5,200.  The certification on the tower is only good for my 350 turbine.  If any other turbine is put on it, then the whole process has to be repeated.

For the average "joe" it would be pretty much impossible unless you want to spend $15-20K.  You're going to need a mechanical engineer to provide certified loading data on your turbine before you can get a certification on a tower from a structural engineer.  Just going by size of the turbine doesn't work because you have to provide specs, signed by a licensed engineer, on everything from mass centroid to overturning moment under maximum emergency braking.
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Chris

[fabricator]

Got to ask, how hard was it to get an engineer to sign off on that design? Did you do all the calculations and they just double checked your work, or did engineer say this is how it needs to be built?

When I build the next tower in early September I'll take some photos of it being built on the jig.  I'm getting back to full-time fishing for the rest of this summer   

I did all the calculations, design, drawings, and prepared stamped specs for turbine loading.  I used TEP to verify and certify the tower, and it cost roughly $5,200.  The certification on the tower is only good for my 350 turbine.  If any other turbine is put on it, then the whole process has to be repeated.

For the average "joe" it would be pretty much impossible unless you want to spend $15-20K.  You're going to need a mechanical engineer to provide certified loading data on your turbine before you can get a certification on a tower from a structural engineer.  Just going by size of the turbine doesn't work because you have to provide specs, signed by a licensed engineer, on everything from mass centroid to overturning moment under maximum emergency braking.
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Chris

All the engineers I talked to around here stipulated all welding would have to be done by a certified structural welder and they would have to be given copies of up to date certifications. Two of them even said they would require samples of weld coupons that had been used in testing.
That was close to the quotes I got on certifying my geared machine, between $13K and $17K. And that is just for certification of the turbine.
Add the tower and pretty soon you are pushing $50K for a turbine that meets the ordinance requirements in a growing number of units of government, the ROI in that situation for someone who has the grid available is about three generations.

[ChrisOlson]

Add the tower and pretty soon you are pushing $50K for a turbine that meets the ordinance requirements in a growing number of units of government

Your ordinance is worse because they got the monopole requirement.  Not that a monopole is that bad, but a 80 footer is pretty expensive.  You can get 50 foot monopoles up fairly reasonable.  But once you get to 80 feet the foundation costs more than the tower.
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Chris

[fabricator]

Yeah like $10K worth of concrete and $2K worth of rebar and around $2-3k worth of anchor bolts, not to mention $5-6K worth of excavation work. So, right around $20K just for the foundation, for a turbine that cost me about $500 bux to build. Right now language is going through my head that would get me banned for life from 99 percent of internet forums.

[SparWeb]

You two shouldn't take up building airplanes, then.

[keithturtle]

Building airplanes?   If you musy fly, here is an alternative to the FAA examiner with his rules and regs

http://en.wikipedia.org/wiki/Cluster_ballooning

Control is a bit iffy, though

Turtle

[ChrisOlson]

Yeah like $10K worth of concrete and $2K worth of rebar and around $2-3k worth of anchor bolts, not to mention $5-6K worth of excavation work

This turbine is 9 miles west of us.





I watched them pour the foundation for it.  The anchor bolts go down 20 feet in concrete and while the pier that sticks out of the ground is only about 6 feet in diameter, the hole around the pier was 6 feet deep and 30 feet in diameter.  The center where the anchor bolts go was about 8 feet in diameter and drilled 20 feet deep.

They unloaded 14 front-unload redi-mix trucks into that hole over a period of two days.

The turbine is an Endurance G-3120 rated at 35 kW.  The tower is 30.5 meters and the rotor diameter is 19.2 meters.  It is privately owned by Infiniti Retail Services and provides power for their office buildings and warehouse.
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Chris

[kitestrings]

I'm popin' in late on this one, but really nice work Chris.  You make the stuff look easier than it really is - lot's of work in those pictures.

I had one question back a ways.  I was curious if you had to tilt the prop at all to get clearance to the tower at the end of the blades?

Thanks for sharing.

~kitestrings

[ChrisOlson]

Yes, the rotor has 8° tilt and the blade tips clear the tower by 16".
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Chris

[just-doug]

 i found it interesting that you even calculated the forces that braking the turbin placed on the tower.because braking the turbin happens over a short period of time,the braking forces could be several times greater than the generating forces.
the faster the brakes are applied,the greater the tower stresses.brakes and there tower stresses become a design nightmare.eliminating the turbin brakes could increase a given towers saftiey margin.so how bad -high are the braking forces as compared to the genrating forces?is there a rayshow,1/3 possible?

[ChrisOlson]

The overturning moment depends on rotor mass and rpm.  But is is huge - approaching 8.5x normal forces at 90 mph wind speed with the turbine running at full power and sudden braking applied for emergency shutdown.
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Chris