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Old 09/17/2019, 07:59 AM   #1
ej797
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Please help me plan my stand using 80/20 Aluminium

So, I am building a 225 (72 x 30 x 24) in wall tank and I am considering building it with aluminium from 80/20. I have a tendency to over engineer and use the strongest material I can find. I have no problem spending the money to get a strong stand but I don't want to be wasteful either.

I would like to have the stand consist of 4 legs at the corner only so the top has to be plenty strong.

What size aluminum tubing would you use for the legs? How about the top and bottom?

As always, I appreciate your help.


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Current Tank Info: Planning and Building out 225 Gallon in Wall Reef
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Old 09/17/2019, 09:37 AM   #2
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Just a suggestion...You can greatly reduce the need for larger horizontal beams by simply adding additional verticals after sump installation.

You can use the deflection calculator to come up with an answer on your own for the horizontals.. The verticals can be then chosen based on the selected series..
https://8020.net/deflection-calculator
I would shoot for no more than 2mm of deflection at the center (smaller the better)

I would also suggest gussets at each horizontal to vertical transition to help with racking protection if you aren't going to skin the frame suitably..


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Old 09/17/2019, 12:51 PM   #3
ej797
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Definitely going to use gussets. Thank you so much for that link. I hadn't seen that yet. Iwas not familiar with the difference between the fixed and supported ends in the calculator but I found this:

https://www.quora.com/What-is-the-di...d-support-beam

It seems that choosing between fixed and supported for our use will depend on the connections. Any idea whether they offer connections that would allow us to create a fixed connection or should we just treat the beams as if they are supported for calculation purposes?

I appreciate the advice regarding the addition of verticals. I am not ruling it out yet. I'm new to this material but not to building in general. At this point I'm trying to wrap my head around the options available with this stuff. It seems like a great option for a stand though.


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Old 09/17/2019, 01:58 PM   #4
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You would use "supported" for the calculation as your legs are "supports" and those legs are not "Fixed" to something else.

And just a tip.. Search around for other "aluminum extrusion" you might find cheaper prices at Misumi USA or other companies that sell similar product..


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Old 09/17/2019, 04:03 PM   #5
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In filling out the calculator should I use half the weight of the tank? because there are two horizontal beams?


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Old 09/17/2019, 06:38 PM   #6
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Yes


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Old 09/17/2019, 07:49 PM   #7
ej797
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So, I took a stab at designing the stand using 3060 (3" x 6") 8020, Inc. Aluminum. Here are the results:







The parts list does not include any machining or hardware to actually put the stand together. It seems this stand would easily be over $2,000 and just seems to be overkill. That being said I'd still love to have any feedback on whether the stand would be structurally sound as designed or if I am missing something.


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Last edited by ej797; 09/17/2019 at 08:01 PM.
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Old 09/17/2019, 08:20 PM   #8
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As said above, it seems with a center vertical I can dramatically reduce the cost of the stand by using 1530 (1.5" by 3") Aluminum. I knew I would pay a premium for no center vertical but, if I'm right, the scale of difference in price is shocking.

I'm a bit unsure of how to use the calculator. If I use a center brace do I cut the span in half? Do I cut the weight down to a quarter of the tank weight? It seems the 36" span only seems to be supporting a quarter of the weight now. Even if I leave half the weight of the tank (1100 pounds) it still seems I can use the 1530, if in fact I should reduce the span to 36" because of the center brace.

Any help here is greatly appreciated.




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Old 09/17/2019, 08:48 PM   #9
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The weight would be 1/4 of the total distributed load. The nice thing about using the extrusions is the sides are wide open if you have the room you can slide the sump from the side. The bottom braces can be significantly smaller they only serve to keep the legs from spreading out they are not supporting the weight of the tank. Definitely go with 3 vertical supports front and back.

I would take the calculated weight of the tank + water + rock + sand then multiply it by 2 or 2.5 factor of safety. That covers corrosion, defects in the materials and other unknowns.

Mike


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Old 09/18/2019, 10:11 AM   #10
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Yep.. Center brace calculations would be 1/4th the load at 1/2 the span..

And you most certainly do not need the same 3060 for the bottom horizontals.. 3030 would be more than enough..same for the front/back bridging.. save a couple hundred there..


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