Why DIY Stands Fail

[Kenta]

I believe my stand is up to par. Please point out any problems that i missed. Its got plenty of support, not going anywhere.
4X4 legs notched, everything else is 2X4s except the horizontal piece at the top which is a 2X6. Plywood at the ends to reduce tipping. Screws and construction glue to keep it in place.

 

[shoefreak03]

Water weighs 8.333 lb per gallon. Jiggling 750 gallons of water one degree is given by the following equation:
(750 x 8.333) sin (1.0) = 109.03 lb of lateral force (for every degree of displacement) is generated and must be counter braced.

For five degrees that the tank is jiggled, 522.93 pounds of force must be counter braced. This does not take into consideration the inertial forces generated by the sloshing of the water.

For 45 degrees of displacement, 4417.65 pounds of bracing is required. If the inertial effects are at a maximum at the time of maximum displacement, 10665.10 pounds of lateral force will have to be countered with bracing to make your stand earthquake proof.

Stamped sheet metal corner braces tear at the inside corners at a fraction of this force. Lag bolts will also pull out before you see a hint of this type of force.

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If you live in an area that has large swings of humidity from summer to winter, your fasteners will lose their grip in the wood (the holes will enlarge). After a number of years, someone is bound to lean against your tank, setting in motion a very ugly numerical and gravitational sequence.

Your best buddy leans against the tank with a force of 50 lb, causing a displacement of half of a degree. This displacement with the weight of the water adds another 50 lb of lateral force. Added to your buddy's leaning force, there is now just over 100 lb of lateral force which pulls the tank almost an additional half degree. Each time there is an addition of displacement, there is an addition of force...and every time there is an addition of force, there is an addition of displacement. This sequence is continued until the displacement is felt by your buddy who stops leaning on the tank ~ do this experiment - lean against the wall with your shoulder or back and then stop leaning...without pushing off!!!

Bad quickly gets worse, until all of a sudden, you are looking for a new best friend.

Do your friend a favor and add diagonal beams to properly brace your tank.

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Engineers do not learn how to design pretty things. They learn how and why things fail.

damn, i wish i stayed awake in my maths class in college.

 

[rkc772]

I believe my stand is up to par. Please point out any problems that i missed. Its got plenty of support, not going anywhere.
4X4 legs notched, everything else is 2X4s except the horizontal piece at the top which is a 2X6. Plywood at the ends to reduce tipping. Screws and construction glue to keep it in place.

from what i see, you're stand is tought to take the beating on it. i have a 180 gal 6x2x2 and i used 4 of 4x4's and 2x4's on horizontal. i cut the 4x4s like the one you have on the corner. i do not see anything more to it. my floor is not a 100% balance but it sure it balance for me since my water level is balance. i also placed a styrofoam under the tank to even out and fine tune my tank. having 2x6s wow! that's tough to beat!

 

[CHOMPERS]

I believe my stand is up to par. Please point out any problems that i missed....

Nice work! Don't leave the back bare. Screw and glue plywood back there and you will have a stand to die for. You can cut any holes in the back that you need without worrying about affecting the structural integrity. The rule of thumb is one screw every three inches.

...Screws and construction glue to keep it in place.

If those are drywall screws, I would double up on them where you still can. They have good tensile strength, but their sheer strength was not intended for high loads. They will not likely see high sheer loading on your stand but it is always better to be safe than sorry. Your screws should be coarse thread when used in soft wood and fine thread when used in hard wood (predrilled). It is all about pull-out, in fish tank stands that is a bad thing.

 

[CHOMPERS]

...i have a 180 gal 6x2x2 and i used 4 of 4x4's and 2x4's on horizontal. ... wow! that's tough to beat!

How's things shakin' out there in Cali? Did your tank ride out any good earthquakes yet? If anyone is a prime candidate for a truly overbuilt tank stand it is you guys in the jiggly part of the country.

 

[CHOMPERS]

... and did my best to try to knock it over...

Guinness, you worked on that thing way too hard and for way too long to test it that way. The big question should be if you generated wave motion at the surface. That will tell you if it is rock solid or if you just didn't feel it move. A two dollar 2x4 screwed in diagonally now will keep it rock solid years later. If "overbuilt is the only way to go", then don't you owe your fish that two dollar 2x4?

 

[dodgefreak8]

I sure would like to know where you are getting these $2 2x4's

 

[CHOMPERS]

I sure would like to know where you are getting these $2 2x4's

Home Depot, ten years ago

 

[Guinness]

Guinness, you worked on that thing way too hard and for way too long to test it that way. The big question should be if you generated wave motion at the surface. That will tell you if it is rock solid or if you just didn't feel it move. A two dollar 2x4 screwed in diagonally now will keep it rock solid years later. If "overbuilt is the only way to go", then don't you owe your fish that two dollar 2x4?

The waves generated were less than 1/8". I knew it wouldn't come down, and if it would fail, I would rather do it when know one else could get hurt(ie friend leaning, someone getting crushed). Also, there are 2x4's screwed in diagonally. There is one on each side. Do you think I need more? There is also 3/4"ply across the inside beams going the length of the tank. I had help with it from a professional carpenter.

Guinness

 

[Kenta]

rkc772,

Sounds like our stands are very similar. Notching the 4X4 legs is something many people don't do, but it exponentially adds to stability and strength.

Chompers,

I left the back bare, i thought the horizontal 2X6 would take care of any tipping to the left and right. I used 3" wood screws, not drywall screws. The stand has been in use for a year and a half now with no problems.