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Non-engineer has a question
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Posted by: badpacket

06/10/2005, 02:27:23

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Hi All,

Interesting site! Would anyone care to help with what is probably a basic Mechanical Engineering question?

I am in the process of building an aquarium stand for a 100g tank. Total weight of this will probably be 100g x #8, plus 300-400 for sand and rocks, and maybe 60# for tank. Call it #1600+.

There is a lot of mystery surrounding what is and is not acceptable for this sort of application in the Marine Aquaria hobby space. A lot of people have success supporting mid-size aquariums like this with 3/4" plywood space frames, and others go for overkill with 2x4 construction with vertical supports every 24-36".

I would like to build a safe tank stand out of 2x2 square stock. The recommended guage is 11 (1/8"), with vertical supports every 24".

Supposedly, for simple frame construction like this, the main thing to worry about is beam deflection. I've seen a few of the calculators online for determining this, however its rather over my head. I would like to avoid using a center vertical support for the front of the stand to allow greater access to equipment under the tank. I was hoping moving up to 1/4" for the top horizontal frame assembly would have a low enough beam deflection for my glass tank.
Using the Beam Bending Supported on Both Ends with Uniform Loading calculator, with a 60" span and #1600, and Distance x 30", it shows max deflection at any point to be 0.00016

Uh, that seems like a pretty small number, however not sure what it is using as a default beam. Or is it beam as in beam, and not square tube steel?

Any help would be greatly appreciated.

thanks,

Fred







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Re: Non-engineer has a question
Re: Non-engineer has a question -- badpacket Post Reply Top of thread Forum
Posted by: randykimball
Barney
06/10/2005, 20:53:38

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Fred,
Been there done that...here's how I did it.

I built a frame for my 125 gal out of 1.5" angle iron.
The main thing to do is be sure the corners are supported and that the frame will remain square when it has the weight on it. My frame is still doing fine and has gone through a tough move and is about to take another move. Make sure your bottom ends of the legs have some way to adjust for level. Floors are often not really level. Brace the top corners with something to assure they can not go out of square (more on this in a few lines). As far as supporting the aquariam all the way around.. some modern aquariums are built to be supported by the corners... A properly built aquarium will be a structure unto itself. Be sure it has plenty of glass thickness, this is the most improtant thing to consider, if it does it will not sag, even if it is supported squarely by the ends. If it does not then it will bulge out and break. Meaning, if the aquarium is not solid enough to be a structure to itself then no matter how stout the frame ...it could be sitting on a concrete slab and still buldge and bust. ..SO... after knowing it is a solid aquarium..... be sure the four corners are all equally supported.. I did this by shimming with thin wood and poster board stock.. AND then... I went all the way around (to make me feel better) every few inches and shimmed the aquarium to the top rail of the stand to assure solid contact... then I filled the aquarium about 1/3 full and made sure the shims were to my liking.. this means none of them would slip easy enough to make me think they had no weight on them.. I adjusted accordingly... then 1/2 way full and check... 3/4 full and check... full and check... If mine worked I would think your 2" square tubing will work better or as good... I welded (this is welded construct isn't it??) cross braces about 6 inches from each leg to 6 inches from each top rail (this makes a 6 X 6 triangle gusset) all the way around .. then I welded an additional set of rails all the way around inside about half way down for a shelf support (adds much strength). Then I screwed nice looking 1/4 plywood to the ends and back .... and doors to the front.. finished with nice molding. The plywood adds additional squareness strength and takes the wiggle out of the frame. Fasten the plywood securely. You will want the plywood so the frame won't wiggle, even most bought frames will wiggle. Any wiggle in an aquarium frame is a bad thing. To adjust for level put just a little water in the empty aquarium and level to the water.

.. what ya think? Good luck.. worked for me!!! never a problem.. zero...

Mine is at my son's house and I have wished many times I had kept it.

-randy-




The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

Modified by randykimball at Fri, Jun 10, 2005, 21:26:19

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Re: Non-engineer has a question
Re: Non-engineer has a question -- badpacket Post Reply Top of thread Forum
Posted by: zekeman

06/10/2005, 09:26:50

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What are the dimensions of the front and back of the tank and assuming the frame is 2" square steel tube, what is the structure of the top surface of the support?






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Re: Non-engineer has a question
Re: Re: Non-engineer has a question -- zekeman Post Reply Top of thread Forum
Posted by: badpacket

06/10/2005, 16:00:18

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Hi Zekeman,

The tank stand will be 61"L x 19"D x 30"H

A bit smaller than this pic where someone is using 1.5" @1/8" for a 180g tank
: http://reefcentral.com/forums/showthread.php?s=&threadid=573092

Since I am using a glass tank, the entire load sits on the frame edge of the tank, which should be directly on the steel tubing. I buess this is called uniform loading?
Will have a 1/2" plywood top on it though.
Primarily I am trying to avoid a vertical support for the front center of the stand as I need to get a large sump inside there.

A lot of folks thre are saying the 1/8" is strong enough for sure for vertical support. However its figuring out how far one can span with minimal deflection. I could put extra verticals in the front about 1' from each leg to give me only a 36" unsupported span if I have to. But could I span the 60" if I went with something thicker for the top frame assembly like 1/4", or with 2x3 for the top?

Appreciaet your time

"What are the dimensions of the front and back of the tank and assuming the frame is 2" square steel tube, what is the structure of the top surface of the support?"







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Re: Non-engineer has a question
Re: Re: Non-engineer has a question -- badpacket Post Reply Top of thread Forum
Posted by: zekeman

06/12/2005, 23:46:46

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Even with an unsupported span of 36", I calculated a maximum deflection of 0.01" which is not small. I would weld or bolt two tubes (verticaly) on the front and add the gusset you suggest. This will stiffen the front beam by a factor of 5 an the max deflection will correspondingly be 0.002" which is very good.






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Re: Non-engineer has a question Disagree
Re: Re: Non-engineer has a question -- zekeman Post Reply Top of thread Forum
Posted by: Yew Meng

06/14/2005, 14:32:00

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??????????





Modified by Yew Meng at Tue, Jun 14, 2005, 14:33:43

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Re: Non-engineer has a question
Re: Re: Non-engineer has a question -- zekeman Post Reply Top of thread Forum
Posted by: Randykimball
Barney
06/13/2005, 19:23:49

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However, a modern properly constructed aquarium does not induce beam deflection along the length or breath of the base. It uses glass of enough strength and glued construction of enough strength to be a unit until itself to hold the weight of the contained water and its own mass if it is properly supported at the ends and corners. Otherwise the glass would blow out at the sides of the base...
-randy-



The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

Modified by Randykimball at Tue, Jun 14, 2005, 18:24:12

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Re: Non-engineer has a question
Re: Re: Non-engineer has a question -- Randykimball Post Reply Top of thread Forum
Posted by: zekeman

06/14/2005, 07:55:17

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I disagree. No matter how strong you make the tank, ultimately the load has to be carried by the beams, which obviously cause deflection in same.






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Re: Non-engineer has a question
Re: Re: Non-engineer has a question -- zekeman Post Reply Top of thread Forum
Posted by: swearingen

06/14/2005, 15:02:31

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Gotta disagree with you zekeman and agree with Randy. It's not a question of strength, but stiffness. The E of glass may be much smaller than for steel, but the I of a vertical glass wall a few feet high is much, much greater than the I of the relatively small depth beams beneath it. The glass gets the load to the corners...






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Re: Non-engineer has a question
Re: Re: Non-engineer has a question -- swearingen Post Reply Top of thread Forum
Posted by: badpacket

06/18/2005, 14:38:14

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Hi All,

Well, thanks I guess. You're losing me a bit..
I wasn't aware of the strength of the actual aquarium/frame itself, interesting.

Looks like I can get 3/16 angle iron for extremely reasonable. Would a 36" span of 3/16' angle iron work? Someone told me that with glass aquariums, you can have up to 1/2 their thickness in deflection before they break. My glass is 3/8's, however I don't really want to test the theory.
I'm thinking this has to be more than sufficient, plus there will be plywood and foam between tank and top of stand.

Thanks again.







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Re: Non-engineer has a question
Re: Re: Non-engineer has a question -- badpacket Post Reply Top of thread Forum
Posted by: badpacket

08/04/2005, 20:28:25

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Just wanted to thank Randy and everyone again for their information, and their time. Will post a pic or link shortly in the event anyone is interested.





Modified by badpacket at Thu, Aug 04, 2005, 20:29:56

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Re: Non-engineer has a question
Re: Re: Non-engineer has a question -- badpacket Post Reply Top of thread Forum
Posted by: randykimball
Barney
08/04/2005, 23:28:38

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I'm sure I speak for all when I say, "You are very welcome".

It is a treat to have a few that come back and say thank you, and I'm sure a link to a picture of the results would be enjoyed by many.

for all, -randykimball- moderator




The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.


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