Will this hold? one time... - Page 2 - The Planted Tank Forum
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post #16 of 35 (permalink) Old 05-02-2013, 03:57 AM
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Originally Posted by Indychus View Post
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.
Wow! Thank you for the explanation. Much appreciated!
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post #17 of 35 (permalink) Old 05-02-2013, 04:13 AM
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Wow! Thank you for the explanation. Much appreciated!
Not a problem! I'm a huge math/physics nerd so I could talk about this kind of stuff all day haha.
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post #18 of 35 (permalink) Old 05-02-2013, 04:20 AM Thread Starter
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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.



WORD. Mechanical engineers are useful.

changing back to this again:
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post #19 of 35 (permalink) Old 05-02-2013, 04:25 AM
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post #20 of 35 (permalink) Old 05-02-2013, 06:30 AM
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Originally Posted by Indychus View Post
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.
Thanks for that through explanation. It may take me some time to trust a stand built the way you say but as long as you got better than a "c" in your engineer class I think I can trust you LMAO.
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post #21 of 35 (permalink) Old 05-02-2013, 06:34 AM Thread Starter
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Thanks for that through explanation. It may take me some time to trust a stand built the way you say but as long as you got better than a "c" in your engineer class I think I can trust you LMAO.
A C is average. Thats solid lol.
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post #22 of 35 (permalink) Old 05-02-2013, 06:44 AM
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Haha if you had a brain surgen work on you, would you want him to have a "C" or an "A" LOL
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post #23 of 35 (permalink) Old 05-02-2013, 06:46 AM
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Haha if you had a brain surgen work on you, would you want him to have a "C" or an "A" LOL
C's are A's in engineering school.
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post #24 of 35 (permalink) Old 05-02-2013, 06:47 AM
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Haha if you had a brain surgen work on you, would you want him to have a "C" or an "A" LOL
I personally have never asked any of my doctors their grades in school =<

You know what you call someone who has graduated med school with a D-?
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post #25 of 35 (permalink) Old 05-02-2013, 07:18 AM
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C's are A's in engineering school.
LOL

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I personally have never asked any of my doctors their grades in school =<

You know what you call someone who has graduated med school with a D-?
DETERMINED!!

Haha, sorry Off topic
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post #26 of 35 (permalink) Old 05-02-2013, 12:48 PM
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Re: Will this hold? one time...

Indychus, question just so no one gets any bad ideas lol. That form of support does not work for tanks that have the glass inside the vertical panes, like an ADA tank correct?

I would think it really only implies to tanks that have a "trim" around the bottom?

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post #27 of 35 (permalink) Old 05-02-2013, 03:51 PM
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Ha ha an Ada tank on cinder blocks ! Now that would be funny , I wonder if Amano does that lol

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post #28 of 35 (permalink) Old 05-02-2013, 04:32 PM
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Originally Posted by NWA-Planted View Post
Indychus, question just so no one gets any bad ideas lol. That form of support does not work for tanks that have the glass inside the vertical panes, like an ADA tank correct?

I would think it really only implies to tanks that have a "trim" around the bottom?

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It *should* still be ok, but I have never owned an ADA tank or done any calculations on what kind of support they would need. If you can afford an ADA, it's best to just buy a proper stand.
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post #29 of 35 (permalink) Old 05-02-2013, 04:37 PM
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After I read this last night I checked my two tank stands before going into work today. Sure enough only the corners are supported by the stand. Never noticed it before but they've been like that for a long while and haven't broken.

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post #30 of 35 (permalink) Old 05-02-2013, 04:42 PM
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Re: Will this hold? one time...

Quote:
Originally Posted by Indychus View Post
It *should* still be ok, but I have never owned an ADA tank or done any calculations on what kind of support they would need. If you can afford an ADA, it's best to just buy a proper stand.
Granted lol. But I would say on the safe side until you get back to us only use this method to support tanks with that plastic trim

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