Glass aquarium stand with support on the corners only?

[BeanAnimal]

Who says I DON'T have a physics and engineering background?

Respectfully, because your posts demonstrate that you don't

What YOU don't have is the knowledge of what these tanks are engineered for.

Umm... Do I really need to point you blatant contradiction in the logic between that sentence and the one that preceded it? I will anyway:

In the first sentence: "Who says I DON'T have a physics and engineering background?" You attempt to discredit my comments by inferring that I can have no way of knowing your background.

In the second sentence: "What YOU don't have is the knowledge of what these tanks are engineered for." You attempt to discredit my comments by inferring that YOU do know MY background.

So (again) within 2 sentences you have contradicted your own logic. Wet noodle debate tactics never work, and to this point, you have not articulated a point. You asked a question and several of us have tried to kindly answer by providing basic information regarding the general design characteristics and performance of a typical off-the-shelf aquarium. If you do not agree with answer, please articulate why instead of playing circular word games.


So to recap, I (we) have articulated why the tank should not be supported at ONLY the four corners.

Pot, meet kettle. Kettle, meet pot.

The only circular or contradictory logic presented here is coming from you... Oddly (or not) it appears to be a pattern with many of your responses. At this point I think you are just arguing for the sake of arguing, and I don't get that. You asked if a tank can be supported at ONLY the 4 corners. I have pointed out why it should not be supported in that manner. I have done so based on my knowledge of physics, materials science, and general design criteria for aquariums.

So what? Can you tell me what the safety factor is for any commercial tank? No, you can't, so your attempt at education is pointless.

Wow... for somebody asking the question, you do not appear to be very receptive to the answers.

In context here, the "safety factor" is a unit less number indicating a scaled margin of safety above the minimum required (enough to hold water) of the "system". The number encompasses the glass thickness, panel dimensions, seam properties, and other physical design components. Plain old engineering (physics) is used to determine the loads on each critical point of the system, with the base assumption being a FULLY SUPPORTED perimeter and a static load (still and full of water).

As critical parts of the system (the aquarium) are strengthened (thicker joints, thicker glass) the safety factor increases due to the stronger components. The net effect is the system moves further away from critical failure due to added strength.

Again, removing support from the panels transfers the static load to other portions of the system. The net effect is the opposite of above and those components move closer to (or past) the minimum required strength for the force acting against them. This is not questionable or debatable. It is (as you said) BASIC physics. If you have bridge supported by 4 piers and you remove 1 of them, the remaining 3 piers take on the load that was held by the 4th. Will the bridge stand? That depends on the safety factor (again a unit less concept with different criteria than a fish tank).

So the question here is NOT the physics (we can certainly start doing math, but there is no point). The question is the "safety factor".

If the tank is built at a 2.5 to 3.5 safety factor, then there is not a lot of wiggle room between ideal conditions and catastrophic failure. You will find that MANY mainstream aquariums are built in that area. The savings are both in materials cost and weight (shipping). If PROPERLY supported, everything goes well. Or in more understandable terms, that safety factor allows for minor defects in support, protection against bumps, vibration and other typical but controlled (predicted) stresses. Many of us would prefer (and some tanks are designed with) a much higher safety factor in the neighborhood of 6 or more.

Note: (again) that even at a safety factor or 6, the assumption is full support. SO point loading the four corners reduces the real world safety factor from that of the designed safety factor... By how much? I have no desire to go about calculating the difference. Which brings us to the next note: Most tank designers do not sit and pour through dozens (hundreds) of calculus integrations to determine the net safety factor. Instead, time tested guidelines based on those actual calculations are used. We know the general strength of glass panels and silicone seams given their dimensions. Taking both into consideration (again fully supported) we can simply do some math and derive a net (general) safety factor for the system (aquarium).

And if this mystery poster wants to tell me the proper way to support his tanks, I'll listen to him.

He already did: "In the final analysis, the tank should sit square, and flat on the stand rim—with no gaps, empty or full. " Note the logic and advice is not just for "HIS" tanks, it (again) is general physics. An aquarium can (easily) be designed to SAFELY handle the stress of being only supported in the 4 corners. The aquariums we are talking about simply aren't.

 

[Khemul]

Because, there is a difference between advocating and admitting feasibility.

For corporations, no, there isn't. And it is a bit naive to think otherwise.

You seem to have made up your mind. It's simple really. It is possible to do it. Will the tank fail? Possibly. Physically, it is entirely feasible. Not many are going to advocate it since there us a chance of failure. No company is going to admit it is feasible since that could imply advocating it. I've seen stores do it with cinder blocks. They were willing to take the risk.

If you do do it, try to set up a webcam pointed at it. It'd be a shame to not film the results.

 

[HippieSmell]

Sounds like your mind was solidly made up before you ever started this thread.

I'll give you what you want;

YES, Go for it! It'll work fine and the tank will last a thousand years, no question

Actually, I had no intention of doing it. I simply wanted to know if it was possible. I figured if it was possible, I wouldn't have to worry about a stand design I'm working on that may have less than ideal span support.

Respectfully, because your posts demonstrate that you don't

I was a semester away from an aerospace degree until I switched majors, but it's been a number of years now. I know enough about safety factors, static load points, moments, material science, physics, math, all that stuff to understand the gist of what's going on here. I don't have the desire (or confidence) anymore to relearn and work it all of it out myself, that's why I asked.

Umm... Do I really need to point you blatant contradiction in the logic between that sentence and the one that preceded it? I will anyway:

In the first sentence: "Who says I DON'T have a physics and engineering background?" You attempt to discredit my comments by inferring that I can have no way of knowing your background.

In the second sentence: "What YOU don't have is the knowledge of what these tanks are engineered for." You attempt to discredit my comments by inferring that YOU do know MY background.

So (again) within 2 sentences you have contradicted your own logic. Wet noodle debate tactics never work, and to this point, you have not articulated a point. You asked a question and several of us have tried to kindly answer by providing basic information regarding the general design characteristics and performance of a typical off-the-shelf aquarium. If you do not agree with answer, please articulate why instead of playing circular word games.

Jeez, relax. I don't care.

If the tank is built at a 2.5 to 3.5 safety factor, then there is not a lot of wiggle room between ideal conditions and catastrophic failure. You will find that MANY mainstream aquariums are built in that area.

Yeah, but how do you know what safety factor commercial tanks are built at?

Note: (again) that even at a safety factor or 6, the assumption is full support.

Assumption, yes. You assume it's full support, but I'm asking if it isn't. Have you seen some of their stands? Just look at the picture above. There's also another stand on the Fosters and Smith site that is basically 4 tubes for legs and an mdf top. It just doesn't seem like what I'm asking is that crazy.

Which brings us to the next note: Most tank designers do not sit and pour through dozens (hundreds) of calculus integrations to determine the net safety factor.

I bet AGA/Perfecto/whoever did. Probably even used a computer.

An aquarium can (easily) be designed to SAFELY handle the stress of being only supported in the 4 corners. The aquariums we are talking about simply aren't.

Ok, but how do you know this? Did you ask? Did you do the calculations?

For corporations, no, there isn't. And it is a bit naive to think otherwise.

Oh, really? Do you ever see car commercials where it says, "Professional driver on a closed course. Do not attempt." on the bottom of the screen? It's feasible that the car can do those things, but they don't advocate it.

If you do do it, try to set up a webcam pointed at it. It'd be a shame to not film the results.

Not cool. I hope you remember this post the next time something bad happens to you.

 

[Khemul]

Oh, really? Do you ever see car commercials where it says, "Professional driver on a closed course. Do not attempt." on the bottom of the screen? It's feasible that the car can do those things, but they don't advocate it.


Not cool. I hope you remember this post the next time something bad happens to you.

The car thing is completely different. The car is designed to safely do those things (well, except get hit with a large meteorite...), it's the user they don't trust to reproduce the results.

You asked a question, didn't like the answer and then started lashing out at everyone. Don't act all offended when you get the appropriate response. If you can't be bothered to accept the advice of others, then at least be curtious enough to film the results so others can learn from it.

 

[jimmyj7090]

http://en.wikipedia.org/wiki/Troll_(Internet)

 

[HippieSmell]

The car thing is completely different. The car is designed to safely do those things (well, except get hit with a large meteorite...), it's the user they don't trust to reproduce the results.

You asked a question, didn't like the answer and then started lashing out at everyone. Don't act all offended when you get the appropriate response. If you can't be bothered to accept the advice of others, then at least be curtious enough to film the results so others can learn from it.

Oh, it's different. Sure.

The only person I may have lashed out at is Bean because he likes to talk down to people. I've seen it for years on this site and other sites. You decided to call me naive, which is insulting, and include snarky comments about filming my tank as is breaks. Very nice of you, now jog on.

The thing is, the answers I've gotten aren't adequate. Everyone says not to do it, but the only person who's tried to put some thought into it is Bean. The problem is that his answers are just educated guesses based on safety factors and other assumptions that he admits he hasn't calculated or gotten from the manufacturer.

Excuse me for not simply rolling over and asking questions.

 

[HippieSmell]

http://en.wikipedia.org/wiki/Troll_(Internet)

I'm not trolling.

What amazes me is that someone actually posted a picture of a commercial stand that supports my question, and everyone ignores it.

 

[HippieSmell]

I think we should look at the problem this way:

If we had a traditional stand with support all around the perimeter, then created a one inch gap in the center of each span, would the tank fail? No, I don't think it would be in any danger whatsoever (assuming all remaining support stayed square and level). This would, technically, be corner support. The question is how far can it be pushed? I'm not suggesting that a tank is able to withstand resting on points the size of dimes, but there must be a middle ground.

 

[jimmyj7090]

I posted the link because this sure looks like trolling or something similar. You posted a question, then proceeded to argue with everyone who took the time to share thoughtful and relevant responses.

If you're serious, well, take a step back. All that talk about safety factors is exactly what you're asking about. The less supported the tank, the lower safety factor will be and the greater the likelyhood of failure. Having a tank that's at a safety factor of 2 does not assure that it will fail, it simply tells us that failure is a lot more likely than if the safety factor were higher. Knowledgeable people have shared their input on this and you have disregarded them. What else do you want? Take a tank that's built to be supported all around and set it up with support only on the ends - it's more likely to fail. What else do you want to know? It's all about odds and risk....

 

[HippieSmell]

Of course it's more likely to fail, but so is anything less than placing a tank on a solid slab of marble. Silicone is more likely to fail than acrylic. Why doesn't everyone buy two inch thick acrylic tanks on marble blocks?

What's wrong with demanding a definitive answer? I may not get the answer I'm looking for, but it's not rude to challenge incomplete answers. My mistake was asking this question on a public board and not going directly to the source.

 

[jimmyj7090]

You're just going in circles. There is no definitive answer, just increased risk. What are you expecting, or should I just post the trolling link again

 

[HippieSmell]

There IS a definitive answer, I'm just not going to get it from anyone here. All that's been said in this thread is that corner loading is not as safe as something that's safer. No kidding.

And you can post all the links you want, smart guy.

 

[jimmyj7090]

"physics wise" any point of contact carries the load. With the entire perimeter supported, the load is distributed evenly along that perimeter and transferred to the stand. As you remove support, the stress at the remaining contact points increases, as does the point load at those areas on the stand.

Can a fish tank be supported by all 4 corners? Sure... if it is built to do so, along with the stand being built accordingly. Loading ONLY the corners changes much of the way the panels behave, not only do they have forces trying to push them apart, but also forces trying to bow them downward. Because of the geometry those forces will tend to warp the panels instead of bowing them in their strong direction. This "bowing" could be In the same direction as the forces pushing them apart (the water pressure) or counter to the water pressure. Furthermore, those added forces create significantly more force acting on the silicone joints....

The end result, regardless of how you do the math, a tank (designed for it or not) will be in much greater stress if supported only by the corners. In reality, this means an off-the-shelf aquarium is in grave danger of failure if supported in such a manner. Put simply, if it does not break when filled, the entire safety margin in the design is compromised and it will take very little to cause catastrophic failure.

^ There is your answer.

And no, I guess I don't need to feed you anymore links.

 

[Khemul]

The thing is, the answers I've gotten aren't adequate. Everyone says not to do it, but the only person who's tried to put some thought into it is Bean. The problem is that his answers are just educated guesses based on safety factors and other assumptions that he admits he hasn't calculated or gotten from the manufacturer.

Excuse me for not simply rolling over and asking questions.

Err..

You have to use a little common sense with this. The manufacturer will say the tank requires direct vertical support (bottom of the tank to the floor) at all four corners.

This requirement is to "prevent" folks from floating a tank in the middle of a sheet of plywood, with no direct vertical support under the corners. This is the often brought up "stand larger than the tank footprint" scenario, that we attempt to shoot down every time it comes up. The way it is put is: "The tank reqiures direct vertical support under the four corners of the tank." They do.

Common sense is not common, so it is easy to see why someone would think that you only need support under the four corners. The assumption is semantical in nature, but is an accident looking for a place to happen.

The bombproof stand design, is a 6 sided 3/4" hardwood ply box. Bombproof, provided there is direct vertical support under the four corners of the tank. No lumber required. However, with this design, the span is not "unsupported." Doors are cutouts in a single sheet (not pieced together) and this leaves a 4" - 6" "header" to support the span of the tank. More than a 3' span, you should have an additional direct vertical support under the span. Some would argue for more than a 2' span.

The bottom line is the tank needs to sit on top of the top rim of the stand, not out in the middle somewhere, whether 6" in, or 1/2" in. Using the tank as a suspension bridge is not what is being dicussed when saying "the tank requires direct vertical support under the four corners."

I'm not trolling.

What amazes me is that someone actually posted a picture of a commercial stand that supports my question, and everyone ignores it.

Again...

At some point in time, the tank will match the profile of the stand. What happens then, is unpredicitable, and there are many variables. It is less critical with a rimmed tank, than with a rimless tank. A rimless tank, at this point would be facing certain doom.

One of two causes for this condition: 1) The stand rim was not flat to begin with, or 2) the span of the stand rim is deflecting down, due to inadequate support. Perhaps a combination of both. There is no cure for the condition, other than planing the top rim, and/or adding a center vertical support. (whichever the culpret is.) Shimming it will point load it.

In the final analysis, the tank should sit square, and flat on the stand rim—with no gaps, empty or full.

There IS a definitive answer, I'm just not going to get it from anyone here. All that's been said in this thread is that corner loading is not as safe as something that's safer. No kidding.

What more do you want? This is what is making no sense here. You keep responding with hostility to or completely ignoring those actually answering the question. Do you want an exact timeline on when the tank will fail or something? There isn't any more that can be said beyond what people have already said, and from what you've claimed about your education you should full well know this.


Guess we'll have to wait till you get a definitive answer from the customer service rep at Marineland. I doubt they'll be minimum wage employees fed pre-prepared responses.

 

[HippieSmell]

^ There is your answer.

And no, I guess I don't need to feed you anymore links.

That's not good enough. All he said is that there is more stress on the tank when supported on the corners. That's not a revelation. I want to know if commercial tanks are actually designed to withstand corner support. He does not address that question.

If you're so worried about me being a troll, you sure seem to be falling for it over and over.

 

[HippieSmell]

What more do you want? This is what is making no sense here. You keep responding with hostility to or completely ignoring those actually answering the question. Do you want an exact timeline on when the tank will fail or something? There isn't any more that can be said beyond what people have already said, and from what you've claimed about your education you should full well know this.


Guess we'll have to wait till you get a definitive answer from the customer service rep at Marineland. I doubt they'll be minimum wage employees fed pre-prepared responses.

I think Uncleof6 is assuming that the stand is defective. I don't think it's safe to assume that because it may be designed that way. It looks like the tank is sitting flush with the top.

There is plenty that can still be said. But, it has to come from someone with more information, not from a couple people who will accept an explanation because they may not even understand the question.

You're right though, my response from Marineland may not be the greatest. Maybe I'll call and see if I can get someone who knows.

 

[BeanAnimal]

That's not good enough.

For a person who claims to have been mere credits away from a degree in aerospace, a quantitative answer should be no more than a few strokes of the calculator away. In fact, static load and failure analysis training would have been intensive and early in the aerospace engineering track, as everything else builds upon it. So degree or not, that fact that you posed the question in the first is puzzling at best.

At face value, such education (even for one who failed most of the coursework) would allow one to speak in technical terms about the topic at hand and allow them to draw reasonable and logical conclusions regarding that subject. You are not drawing such conclusions in a logical manner and many of your responses have been rather contradictory to themselves. No problem, but you either understand the application of physics here and can draw a reasonable and supported conclusion, or you don't. You insist you do, but are demanding that somebody else do the math for you.

To that end, the entire base question is more than a little ambiguous. The effects of removing portions of the support would differ from tank to tank. An 8 foot long tank will incur significantly more stress over a full span than a 4 foot long tank of the same height, depth and width. Again, basic physics.

A few of us here likely have the skillset to dig out the text, find the proper formulae and integrations and do the math, but none of us will. The work has already been done by other pinheads and we can simply use that work to quickly estimate the safety factor of a given design based on the materials and dimensions of that design, safe in the understanding that we are calculating safety factor based on reasonable best case support of the system.

If you were here to participate in a discussion, ask questions, and learn from those providing factual answers, then I am sure somebody would be happy to take a stab at doing the math. As it stands, and with each passing post, it becomes clear that your only desire is to create friction and post soft insults while presenting an ever moving target of half-logical tangents and fallacy. Sadly, looking at many other threads you "debate" in, they follow the same pattern. I hope marineland provides you with what you are looking for...

 

[Khemul]

There is plenty that can still be said. But, it has to come from someone with more information, not from a couple people who will accept an explanation because they may not even understand the question.

And there in lies a big part of the problem. You didn't give any more information for anyone to work on. Where is this "someone with more information" supposed to come from? :facepalm:

 

[reefer91]

Why don't you do the math yourself? It's not exactly rocket surgery. Seems like a pointless thread even though I understand why you are responding the way you are.

 

[jimmyj7090]

If you're so worried about me being a troll, you sure seem to be falling for it over and over.

Well, here I go again..... http://www.mcdonalds.com/us/en/promotions/quarter_pounder.html