Will this hold? one time... - The Planted Tank Forum
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post #1 of 35 (permalink) Old 05-01-2013, 10:10 PM Thread Starter
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Will this hold? one time...

Stacked 2 40's on metal frame. Made custom wood piece to put under 40b iwagumi to raise the tank and also be a drawer to put equipment.

The breeder touches on 3 sides (sides and back). Is this safe?

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post #2 of 35 (permalink) Old 05-01-2013, 10:19 PM
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I wouldn't personally. The bottom should be touching on all 4 sides.

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post #3 of 35 (permalink) Old 05-01-2013, 10:19 PM
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If all 4 sides aren't sitting on the wood or metal stand I would be very cautious. A 40B weighs 360lbs filled with water, not including rocks and substrate which could add another 50-100lbs.
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post #4 of 35 (permalink) Old 05-01-2013, 10:34 PM Thread Starter
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What if i put a piece of wood on the center front. That would make 2 shelves.
Would this help?

or

close it off with an entire piece of wood so all 4 are touching
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post #5 of 35 (permalink) Old 05-01-2013, 10:43 PM
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Putting something in the front center would be better than nothing, but I would just give up the shelf to be on the safe side. Better to not have a shelf than a broken 40b.

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post #6 of 35 (permalink) Old 05-01-2013, 10:48 PM Thread Starter
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Quote:
Originally Posted by Clemsons2k View Post
Putting something in the front center would be better than nothing, but I would just give up the shelf to be on the safe side. Better to not have a shelf than a broken 40b.
ugh fine :P

what about 3 sides and bottom on a 20L? is that okay since its alot less weight?
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post #7 of 35 (permalink) Old 05-01-2013, 11:06 PM
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I think the issue with all 4 sides not touching is that it can put stress on the side that isnt supported. And if glass is stressed theres a possibility of it cracking. Its your tank so you must decide, but I wouldn't risk it
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post #8 of 35 (permalink) Old 05-02-2013, 01:50 AM
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Quote:
Originally Posted by Soup12 View Post
Stacked 2 40's on metal frame. Made custom wood piece to put under 40b iwagumi to raise the tank and also be a drawer to put equipment.

The breeder touches on 3 sides (sides and back). Is this safe?
As already pointed out by others here, it is not safe.

However, I do not see a problem if the tank is on a thick compressed board which in turn sits on the wood blocks.

That way, you will still have the drawer.
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post #9 of 35 (permalink) Old 05-02-2013, 01:57 AM
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Only the corners need to be supported. Your stand is perfectly fine as long as all four corners are level and fully supported.

That's coming from a mechanical engineer... but if you don't trust me, here's some pics I found to illustrate the point.



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post #10 of 35 (permalink) Old 05-02-2013, 02:11 AM
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Originally Posted by Indychus View Post
Only the corners need to be supported. Your stand is perfectly fine as long as all four corners are level and fully supported.

That's coming from a mechanical engineer... but if you don't trust me, here's some pics I found to illustrate the point.
Good to know!

Since you are a mechanical engineer, can you explain why it is safe? I am just curious on the principles behind.
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post #11 of 35 (permalink) Old 05-02-2013, 02:14 AM
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physics!
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post #12 of 35 (permalink) Old 05-02-2013, 02:42 AM
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The strength of the tank along the front and back are due to the vertical pieces of glass. In the vertical position, the glass has a high second area moment of inertia, which means it has a high resistance to bending. This is why I-beams are so strong and lightweight. Their strength comes from the center vertical web. Glass (especially tempered glass) is much stronger than most people think, it just has almost no ductility- it's extremely brittle. As long as the front and back panes are completely vertical (i.e. all corners perfectly level), then those panes act much like I-beams would and easily support the weight of the tank. What breaks tanks is any twisting of those panes... Because of it's low ductility, any twisting builds stresses that glass can only relieve by cracking (annealed) or shattering (tempered).

If you look at most store-bought stands, the tank doesn't touch in the centers anyways. Most people attribute this to poor manufacturing standards and throw some foam or something under the tank to "even it up." In reality, the only real concern is that all four corners are perfectly level and no torsional stresses are introduced to the glass.

Of course, the best course of action is to err on the cautious side and support the tank all the way around its perimeter. This can lead to other issues however, since then the entire stand needs to be absolutely level. Any "high spots" along the perimeter will introduce a point stress that is much more detrimental to the structural integrity than a stand that only supports the corners, as the stresses introduced in the corners-only case follow a uniform and predictable distribution and are spread throughout the entire length of the pane.

In short, a fully supported stand that is perfectly level all the way around provides the highest factor of safety. A stand with all four corners supported and completely level will provide a satisfactory factor of safety and you'll never have any issues unless the tank is of odd dimensions (in which you may need to calculate if only supporting the corners is indeed safe). The main concern should always be making sure the corners are level and no point stresses are introduced anywhere.

Last edited by Indychus; 05-02-2013 at 02:48 AM. Reason: edit
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post #13 of 35 (permalink) Old 05-02-2013, 02:47 AM
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Crazy!

that's just crazy, awesome!


Quote:
Originally Posted by Indychus View Post
Only the corners need to be supported. Your stand is perfectly fine as long as all four corners are level and fully supported.

That's coming from a mechanical engineer... but if you don't trust me, here's some pics I found to illustrate the point.



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post #14 of 35 (permalink) Old 05-02-2013, 02:51 AM
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My wife would have a fit if she came home to see all my tanks "balancing" on blocks over the hardwood flooring ha ha !

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post #15 of 35 (permalink) Old 05-02-2013, 02:54 AM
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Yeah, the cinder block stand is probably a terrible idea. But it does illustrate that we oftentimes overestimate how much stand is really needed. I think most busted tanks are due to damaged glass (it only takes a small scratch or chip) or the tank not being entirely level. Any twist in the tank is a death sentence for it, it's just a matter of time.
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