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Forum Index : Solar : Solar Array I Beam- Reinforcing
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| floodrod Regular Member  Joined: 08/07/2009 Location: Posts: 70 |
Hi all, So I messed up and need advice. I'm building a solar tracker on a pole mount. Pretty large, 20' x 12' on a 11' high mast. So I went to the scrapyard to find a pipe and ended up bringing home an I-Beam. It's 16' length.. I poured 3 1/4 yards of concrete (13,000 lbs) and mounted the pole 5' deep so now it's sticking up 11 ft. I placed the array frame on the mount and now the I beam is not firm enough. Torsion and opposite web action will definitely buckle this beam when weight + wind are applied.. So I cut 8 angle irons and welded lateral bracing evenly spaced. This helped substantially, but I do not think it is sturdy enough yet. My next idea is to get Sonotubes and 15 bags of concrete and encase the whole beam. Will a 12" diameter concrete column with an I-beam encased be strong enough to hold about 750 pounds of panels and framing? Thanks! |
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| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
That is a huge area.. 20x12 feet,. How many panels will you attach? Mine is 4 inch pipe, around 4 feet out of the ground with 2x 3x3 angle beams back to back as a back brace.. She's as solid as a rock , but my 4 x 220watt panels still wobble a litle in a storm.. So your,s will rock like crazy ,you'll have to do what you are doing and STILL provide a very solid back brace or even 2 ??. 20X12 feet, my,what an area to keep rock solid ,best of luck . Bruce Bushboy |
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| floodrod Regular Member Joined: 08/07/2009 Location: Posts: 70 |
hi bruce.. I want to mount 20 panels. each panel is 120 watts. they are 58" x 27" each. So I would have 5 rows of 4. Total weight of the panels is about 500 pounds. I built the main frame 10' by 52". I plan on using superstrut, which will extend 5 foot off the frame on each end. Then 4 pairs of cross strut for the panel mounting. Panels= 500 pounds Frame= 160 pounds Strut= about 100 pounds But now with the issues, I may have to rethink the plan... |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
OK, here's a pic of my array, She's small compared to what you are doing . I'm having trouble posting pic's,again. But, I'll give it a try ,again. Bruce all I get is image upload ---ISP.NET -never got this before. I get to drag the image from the desktop to the posting window , but can't get further to post it here.. Bushboy |
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| floodrod Regular Member Joined: 08/07/2009 Location: Posts: 70 |
Click the image with the blue arrow. Choose file, and let it upload. here is my home-made crane mounting the frame on the beam.. Now the beam has lateral supports |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Bruce there is no drag and drop function on the forum. The only way to include a image is to upload it using the  icon and follow the prompts, or link to a image on another site using the  icon.
See http://www.thebackshed.com/forum/help.asp#FAQ19 Floodrod what about bracing the tower. Pouring 3 or 4 concrete pads about 10 foot out form the base and use some 3 inch pipe to act as braces? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| floodrod Regular Member Joined: 08/07/2009 Location: Posts: 70 |
Hi Glen, I tried Guy Wires and it did like nothing. The I beam still twisted easily from torsion. Not sure if pipes would be any better. I picked poorly. An I Beam is known to be poor with torsion and force opposite the web direction. I should have researched and just bought a round pipe. But now it's too late. From reading about i beams, seems encasing in concrete may be the way to go |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Pipes wont compress, where guy wires do. Using 3 pipes bolted to the top of the I beam and bolted to 3 concrete pads will basically create a 3 big A frames on each side of the tower, lots of triangles, very rigid. Actually when you think about it there are many more than just 3 triangles here. Use 3 or 4 inch pipe, and the thing would be hurricane proof, at least to the top of the I beam Never been a fan of single post stand alone towers. All that force is concentrated at the base. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| floodrod Regular Member Joined: 08/07/2009 Location: Posts: 70 |
Hi Glen, Sounds like it would work, but that's $400+ in pipe (4x what I paid for the beam), and getting my backhoe up the mountain side to dig the holes would be near impossible without shelving off half my front yard. Hmmm  |
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| M Del Senior Member  Joined: 09/04/2012 Location: AustraliaPosts: 155 |
Hi floodrod It may seem like a lot of work and effort to put the pipes in for bracing, but nowhere near as much work as rebuilding after the first mild storm sends it 200 meters down the hill and busts up most of the panels. Better to make it so strong that you think it is overkill (then strengthen some more)than to watch it take off or come crashing down. Mark |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Hi again , will try after resizing.. 95 kb No, won't work ,takes me to some thing I've never seen before -- says try hsb- upload or something -- have spent an hour trying ,,so ,I dunno. anyhow floodrod, look up my pic album in fieldlines --it's all in there Bruce Bushboy |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Bruce there is nothing wrong with the forums image upload function. Nothing has changed, its the same process its been for years. There is no drag and drop function, you must use the button.
It sounds like there is some third party software installed on your PC thats trying to butt in and make things easier, but breaking the process instead. Can you tell us exactly what you see when it doesn't work? Error messages, etc, word for word. Are you sure its a JPG or GIF file, the forum wont accept anything else. Other than that all I can suggest is you try it on another computer. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| floodrod Regular Member Joined: 08/07/2009 Location: Posts: 70 |
M Del, Yes, it will definitely get reinforced.. It has to.. I am considering drilling 6 or 8 holes in the concrete base and epoxying rebar. Running rebar the entire height in a circular cage. Then encase the whole I beam + rebar cage in 16" concrete round column form. At the top, I will have to reinforce the exposed top portion of the beam and run the supports right down deep into the concrete column. The triangle pipe support is still an option, but I already got loads of rebar and epoxy. So if the concrete column is sufficient, it can be completed for about $150 and look better, as opposed to $500+ and shelfing my front yard. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Sounds like a plan. What about the base foundations, will you go down and out a few feet? I've seen a few poles blown over in strong winds after a few days rain, the concrete footing was too small to support the pole in muddy ground. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Reading your first post, it sounds like you got a fair bit of concrete there already. And you did the right thing and have about 1/3 of the mast under ground. I remember been taught the 1/3 rule by my grandfather. For every 2 meters above ground, you need 1 meter below ground. I had a argument with a fella I was working for a few years ago, a sign writer. He put up a sign on a pole, the pole was about 4 meters above ground, but he dug the hole to 0.6 meters deep, and concreted it in. A few weeks later, it fell over after some rain. His fix was to pour in more concrete. I said he needed to make the hole at least 2 meters deep. His reply was he didn't have the equipment to dig that far, he could only go to 0.6m, so that would have to do! My thinking was if you cant dig the hole to 2m, then you dont put up a 4 meter sign! Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| floodrod Regular Member Joined: 08/07/2009 Location: Posts: 70 |
Hi Glen, The foundation is 52" x 50" x 60" deep with 7/8" rebar cage. The I beam goes to the bottom of the footer. It took 3.25 yards con 3000 psi concrete. So that's roughly 12,000 pounds of concrete. My ground retains no water. I dug an 11 foot hole for another project, and even after massive rains, no standing water in the hole. The ground is like all bone shale and my property is on the side of a mountain. I would hope this footer is enough, but if I need to, I can expand it. This footer used almost as much concrete as my 80 foot Windmill Gin Tower. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Yes Glenn, nothing wrong your end ,just that I put this laptop in for a upgrade/service and it's been unable to post my photo's. So, back it goes. I'll try and tell you what happens.. I click on the upward pointing arrow,like allways. 1 Image upload window appears and it ask's me to browse. 2 upload_images.asp?MSG=BSC 3 after this ,I'm stumped,lol. Thanks Bruce Bushboy |
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| floodrod Regular Member Joined: 08/07/2009 Location: Posts: 70 |
Edit: Did some calculations and verified with local engineers. 240 sq ft panels 11 foot high at 20 psf (overkill for my area) gives me a total force of 52,800'#'s. So if I epoxy in six #5 rebars and install four 5/8 wedge anchors to the base of the beam (rated at 4,400+ lbs shear strength each), I am over 50,000# safe loading zone mark. Add in the strength of the I beam and the base connection far surpasses 90 MPH wind load. I have some 1" rebar I may even throw in for extra measure. I will try to post some pics when it happens |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Is there a particular reason why you want to put 'all your eggs into one basket' as the saying goes. If this was my plan I'd go for several smaller solar trackers. FYI, I have 3 solar trackers on my shed roof, each tracks just 400W (2 panels). The reason they are up there is I get sunrise to 1 hour before sunset exposure, on the ground I'd get nowhere near that. Besides, on my small suburban lot a ground mounted tracker gets in the way. The same # of panels on the hose roof would face E/W - as it is I also have 400W facing E and 400W facing W up on the house roof. My trackers have seen very strong winds up on the shed roof. The roof has massive I beams, which I needed to build my sailboat in there, and the tracker frames are way overbuilt IMO, compared to a similar size ground level tracker. Klaus |
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| floodrod Regular Member Joined: 08/07/2009 Location: Posts: 70 |
Hi Tinker- I originally planned 2 trackers, but can't plot them out avoiding shading from the 1st tracker. And ordering 2 sets of actuators / controllers starts adding up. I am making sure all my calculations are correct. I just finished figuring out the weight limit on superstrut as a cantilever in my wind zone. Can you share a pic of your trackers? |
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