Lumber weight carrying capacity

[jjencek]

I am building a rack for my breeding tanks. I am just not familiar with lumber carrying capacity calculations. I need to span 160 cm (63 inches) and I hope not to have any addition vertical support in the middle. I plan to have four 100 kg tanks on the top of each shelf including water. The lumber that I was thinking using was pine 6x12 cm (2.36 x4.72 inches) . How many of these do I need to span across the 160 cm to carry the weight of 400 kg (882 lbs)? The shelf itself will be 60x160 cm (23.6x63 inches).

The rack will have 2 shelves of 4 tanks each plus maybe one larger tank on top. Here is my attempt of a possible side-view drawing of the rack if I were using 4 supporting pieces.

 

[Doctorgori]

1ST pic is how I do it ..exactly how ..
2nd pic is overkill, especially if you are handy with a level and square
I use exterior grade deck screws and waterproof the heck out of wood
forgive the English units but I wouldn’t span anymore than 6 feet (2x4”) without a vertical (column) support for that weight ...
I wouldn’t dispute other competent post/ideas

 

[ScottJ]

I like the 2nd design personally. No worries about it not being able to carry the load.

But then, I over build everything!

 

[Reeflux]

I did mine completely different with 6×6 poplar. Really happy with it. Giant span. This thing is a tank. I'm sure you could work out a design similar. It leaves all kinds of space.

If I could get it up there, my brother's Ford ranger could sit on this thing.

 

[Rjramos]

I am building a rack for my breeding tanks. I am just not familiar with lumber carrying capacity calculations. I need to span 160 cm (63 inches) and I hope not to have any addition vertical support in the middle. I plan to have four 100 kg tanks on the top of each shelf including water. The lumber that I was thinking using was pine 6x12 cm (2.36 x4.72 inches) . How many of these do I need to span across the 160 cm to carry the weight of 400 kg (882 lbs)? The shelf itself will be 60x160 cm (23.6x63 inches).

The rack will have 2 shelves of 4 tanks each plus maybe one larger tank on top. Here is my attempt of a possible side-view drawing of the rack if I were using 4 supporting pieces.

That would be very strong and supportive. Doubled up in the corners and a a tripled brace going down the middle of 23.6 inches across. In addition, whatever covering you use ( plywood maybe) is gonna strengthen this further. It shouldn’t sag at all. I have one I built out of 2x4 inch lumber, 48”x24”, 4 shelves. I had 600lbs on it and it doesn’t even sag.

 

[jjencek]

Ok, so here are 3 designs now. Please note that #2 and #3 have the same number of 4 spanning struts - just extra pillar. Would not the two have the same carrying capacity?

 

[RocketEngineer]

Number two would be plenty. Given the load and span, 1 may have issues without bigger crossmembers which is not ideal for stacked tanks like this. Three doesn’t gain you anything vs 2. JMO

 

[Soren]

Ok, so here are 3 designs now. Please note that #2 and #3 have the same number of 4 spanning struts - just extra pillar. Would not the two have the same carrying capacity?

+1 for #2 middle design. Better safety factor than #1, #3 is more than necessary for sufficient safety of #2.

 

[ScottJ]

Number two would be plenty. Given the load and span, 1 may have issues without bigger crossmembers which is not ideal for stacked tanks like this. Three doesn’t gain you anything vs 2. JMO

Yup

 

[jjencek]

Ok, after your help I plan to use design #2. Each shelf will carry five 62L tanks for a total weight of about 375 Kg.

Here is the front and the side view.

 

[jjencek]

So the rack is done. Did not have enough room for the top tank, but overall I am happy with it. Now the plumbing ...

 

[mdb_talon]

In case or tornado climb under that thing.