Stand for 480gal

[rnelson]

I am about to start building my stand for my 480gal tank. The dimensions of the tank are 8' long, 2' high, and 4' front-to-back. Here are a couple of diagrams:

View from top:

View from front:

Is it better to use nails or screws, or does it matter?

The stand will be 36" tall. I will have a 3/4" sheet of plywood on the bottom and on the top.

I figure about 4500 lbs of weight on it.....about 450 gallons of water, 400 lbs of rock, 300 lbs of sand.

Any interior cross-bracing that I need to do?

Thanks for any suggestions....

 

[RocketEngineer]

Mechanically, screws are the only way to go. Get coated screws for decks that won't rust. Nice long screws into pre-drilled holes will hold up much better then any nail. Oh, and you may want to consider either wood glue or liquid nails at the joints.

While I think the general concept is sound, I feel you need to change a few things. First off, the 2X4s on top would probubly be better running front to back. Just like floor joists the shorter the run the better they will transfer loads down. Also, I would make the top 2X4s either 2X6 or even 2X8. Following the same idea of a wooden floor, instead of 24" centers, what about the front-to-back pieces being 16" centers? Or better yet 12" centers?

The bottom ones can stay 2X4, they only serve to keep the legs from spreading out.

Next, I would place top boards on top of the 4X4 posts.

As to cross bracing, it depends on where the tank will go. If its in the middle of the room, you may want access from all sides to the equipment under the tank. In that case using the metal plates common in deck framing is a good idea. Small corner braces between the top frame and the uprights should stiffen the structure (a piece of 4X4 or 2X4 with 45s cut on each end would work just fine). If one side were against a wall, I would include braces running corner to corner along the wall side of the stand.

I hope you have a good foundation for this monster because I would guess the system to weight closer to 6000 pounds with all the glass, wood, water, rock, and sand.

Hope this helps.

 

[rnelson]

Thanks for the reply...

So you are saying do it like this:

View from top, top framing:

View from top, bottom framing:

Are you saying to put boards flat onto the tops of the 4X4's, then put the 3/4" top plywood on top of that?

The back of the tank will be against a wall....there will be about a foot of space on either side of the tank.

This is sitting on a concrete slab. I figure it will be about 5000 lbs:
450gal water @ 8.25lbs per gallon = 3712.50
Rock = 400
Wood = 200
Sand = 300
Tank (acrylic) = 400


Thanks again...

 

[azrednex]

I would definately go steel stand, because the amount of wood that would have to go into that stand for me to be comfortable with it would be outrageous. BTW that is going to be like parking a ups truck in 8' of space on a pad that was designed for foot traffic only. You need about a 12" beep footing for that weight.

 

[rnelson]

azrednex,

I don't know how to weld, so it would be hard for me to do the steel stand...a good idea though.

Are you saying that you don't think a slab floor will hold this weight?

 

[RocketEngineer]

azrednex,

the tank will have about the same floor pressure as a 110X. 1100/6=183.3 psf. vs 6000/32=187.5 psf

rnelson, do you know how thick the pad is under the house? was there reinforcement grid / re-bar put in? (probably).

Back to the stand design, putting the top frame on top of the 4X4 posts means that the load path (enginnering speak, forgive me) will directly from the frame, down the posts, to the bottom frame, and into the floor. If you were to try to attach the frame to the sides of the posts, the load would have to go through the screws and you risk having them tear out of the wood (think bad things)

I like the changes in the design but I think azrednex is right in that beefing things up is a good idea. Metal deck brackets under the "joists", and screws from the outside into the ends should provide additional support. Also putting them on 12" centers or you may even think about making beams by sandwiching 1/2" plywood between two 2X joists. These can be bonded and screwed together. The plywood would make the beams as wide as the 4X4 and that way they would be directly supported. A picture would help and will be posted shortly.

Ultimately it is your decision.

 

[RocketEngineer]

Ok, lets see if I can post a pic of the plan

The green between the joists is the 1/2" plywood I meantioned earlier. The ends of the beams sit on half of the posts and are screwed into the face plate that also sits on the posts.

Hope this helps explain things.

 

[Siffy]

Where is the sump going to go? Imo, the design is a little overkill. Even with say 6000lbs, you'd have 15 4x4's each to support 400lbs. Lumber prices just came way down, so go with it if you want. But I think the design gives minimal access and space inside the stand.

 

[RocketEngineer]

Ok, a little more thought over dinner turned up this design.

The front and back beams are made up of a 2X10 outside and a 2X4 inside rail. The joists sit on this rail and are 2X6 on 12" centers.

If you had the tools, you could rip a 2X6 to make the rail 4" tall and then the 2X6 joists would be flush on top for mouting the top plate.

An idea I have been kicking around for these really big tanks is to use aluminum extruded profiles in place of wood or welded steel. These can be ordered to length directly from the company and bolted together using some pretty simple tools.

http://www.8020.net/

Just another crazy idea.

Enjoy.

 

[rnelson]

Thanks for all the replies.....

Yes, the floor has rebar in it....it's about 3 years old.

After thinking it over a bit more, I have another idea.....

Concrete block on both ends and maybe one in the middle.....3 4" H-beam steel going across them with a steel plate on top.....it would be really easy to put together and should hold just about anything, plus it would give me all kinds of room underneath.

I don't know what the cost of the H-beam and the steel plate would be though....anyone have an idea?


Thoughts?

BTW RocketEngineer, what did you use to draw your plans with?

 

[Siffy]

You could probably get away with one or the other. I-beam with plywood top or just 3/4" steel plate spanning the entire length. The former will be the least expensive. You may want to use C-Channel to cut costs even lower. Using 3 4" I beams or 3 6" C channel shouldn't even need the center support. You could possibly go smaller in their sizes as well. Or if you knew anyone/anywhere that scraps semi trailers and use the beams from that, but I'd recommend buying already hot galvanized/zinced material over spraying cold galvanizing paint yourself.

Another thought would be simple "angle iron" but it would be slightly harder to implement. Just a thought for you, I'm currently working in a substation at a fossil plant. In that yard we've been replacing breakers that the new ones weigh roughly 11,000 lbs. They're supported by 1/2" thick 3"x3" angle iron legs. The legs are nearly 6' tall and support a secondary horizontal frame of same type angle iron that covers a much larger area than your tank (just over 8' by 6' iirc, I will measure one tomorrow). The structure does have diagonal supports to prevent it from twisting. longer pieces of angle span from near the bottom of one leg to near the top of the next leg. I will also try to remember my camera as well tomorrow. I'm just trying to point out it's very easy to get carried away and overkill a project. Especially when switching from a material such as wood to aluminum or steel.

 

[RocketEngineer]

rnelson,

I use a program called SolidWorks. Its a professional design package (think $$$) that I have on my personal computer so i can do training at home.

As for Siffy's idea of the C-channel, I would stick with the I-beams because c-channel tends to want to twist sideways when loaded.

I do like the idea of the concrete block pillars. I would use aluminum instead of steel because its lighter and less affected by SW. Personally I would use the 80/20 Aluminum extrusion I meantioned above. You can buy it on McMaster-Carr in 4' and 8' lengths and all the brackets are right there. The pages from their online cataloge are 1586 and 1587. Using the beam idea I meantioned above and 3" X 1.5" aluminum profiles, I figure ~$750 for an aluminum frame that just needs to be bolted together isnt too bad. And it will weigh a heck of a lot less then steel I-beams.

Now you got me thinking, let me run some numbers and get this crazy idea out of my head .

 

[rnelson]

With all that pressure on the concrete blocks, would it break them?

Also, if I used 3 H-beams, could I use 1" plywood for the top instead of metal?

 

[TropTrea]

The biggest point I see is that you do not want your top boards suported by screws or nails. These top runnersw will have a lot of weight on them therefore they neet to directly over the endge of a 2X4. This with create a direct downaward line of solid wood form the tank to the floor.

Another option that I have frequently used here is to uses $X4's and notch them on the ends so a 2 X 4, 2 X 6, or even a 2 X8 will sit in the notch making it easier to fasten and suport..

The next issue is what is thank going to made of and how will your drains and piping be routed. If it is a fiberglass tank then the cross bracing is important to help suport the weight, But if it a Glass tank then the only purpose of the cross bracing is to add stability. Remember that if your piuping is comming through the bottom you must keep these ares clear as there is nothing mor fustrating than foinding out your return bulkhead falls dead center of one of your cross braces.

 

[rnelson]

I called some steel places this morning.....found some H-beam but the shortest length would be 40'......also found some 1/4" 6" standard channel (I guess this is C-beam?) that I could buy cut to specs......if I used solid cinder block, 3 6" C-beam, and either plywood or MDF on top, would that work? Or would wood be a better choice?

 

[RocketEngineer]

Wood. Plywood.

MDF is just like partical board and when wet will end to disintegrate.

 

[Siffy]

I'd go with the I beam over 1/4" thick C channel. Is 40' the minimum they'll sell you or shortest single piece let you leave with? If they'll cut it for you, 40' is no problem. You'll need 24' for 3 8' spans lengthwise and could use another 12' roughly for corner legs if you go away from the concrete supports idea. And likely will want two more just less than 3' legs in the center with a 4' cross front to back to support the longer spans in their middle. That'd be about 45' of I beam.

 

[cougarguy]

If you go with blocks you need to check with your supplier as to the crush strength of the block you intend to use.

If you need room under the stand for equipment I would go with the first design RocketEngineer posted and remove the center 3 4X4's and add a 2 2X4's with ply sandwiched under the 2X8's resting on top of the center 4x4 on each end.

 

[rnelson]

I paid a visit to a metal yard this afternoon. I think I'm going to go with the cinder block/beam route. They had 6" H-beam and also 3" square tube. The 3" square tube is 3/16" thick so it's pretty stout stuff. Which would be the better choice?

 

[rnelson]

This is kind of what I had in mind now:

The metal is not stacked on top of each other......

Still deciding between 3" square tube steel or 6" H-Beam.....