A questions for any structural engineers

[howdy20012002]

just wondering if anyone knows what size and thickness of metal tubing I would need to hold 2 x 4 foot 130 gallon tanks above another tanks. I want to make a stand that holds 2 x 4 tanks above a 7 foot tank.
any info would be greatly appreciated
thanks
Neal

[sphelps]

Assuming you're talking about two 120 gallon tanks over another tank meaning you'll be running two 8 foot beams over the lower tank to support the two tanks above (1400 lbs each) you'll need 3"x3"x.313 HSS tubing (grade 50W or better).

[howdy20012002]

that big eh?
lol
was hopping for a big smaller. Could I go 2 inch but thicker?
that is exactly what I am looking to do btw
thanks again
Neal

[sphelps]

You could use 4"x2"x.313" (2" height) and get the same strength.

You could use a smaller size if you add a center support column. The weakest point in going to be at the ends where the weld is in place, if you reinforce that area with truss support or something similar you could get away with 2"x2"x.25" but it really depends on how the stand is designed and fabricated.

[no_bs]

The smaller the tubing the more gussets and vertical supports you will need.

[hillegom]

[quote=sphelps;468908]You could use 4"x2"x.313" (2" height) and get the same strength.

Sphelps: Did you mean the 4" as vertical? I would have thought that deeper would hold more weight.

[sphelps]

Originally Posted by hillegom

Sphelps: Did you mean the 4" as vertical? I would have thought that deeper would hold more weight.

Deeper would hold more weight in terms of beam strength however the guy asked for a lower profile than 3" so I suggested a 2" x 4" instead of a 3" x 3". Has enough beam strength if laid out 2" tall and the 4" width provides more support at the ends which is the critical spot anyway.

[golf nut]

If you have space behind the tanks you could run a cantilever.

[Fishward]

What kind of defelection are you going to get with an 8ft beam like that? i imagine standard design tolerance is greater than that for a big glass fish tank. it may hold it up but if the beam bends you won't be level and you'll get uneven loading in the tank (and on the beam).

Unless you're on the basement floor (or Concrete Slab) i would also suggest having someone look into your flooring situation. 2 four foot tanks and a 7 foot tank over the same joists is a boatload of weight... a quick guess is over 4000lbs.. not including any rock. or you standing over them to feed/clean/gawk...

[sphelps]

Originally Posted by Fishward

What kind of defelection are you going to get with an 8ft beam like that?

About 40 thou on the sizing I suggested which is about 1mm.