Floor pressure how much (feet not whole stand)

[sfsuphysics]

So long story short, an idea to level a tank stand I have in my mind using self leveling feet. So my question is how much pressure can a floor take to not dent too much. I've already come to the mindset that it will dent some, but if it is going to dent I don't want it to punch a hole through the floor/subfloor. My plan is just a thin sheet of 1/4" on top of the 3/4" base underlayment so that if I ever do move the tank later I can just pull that up and hopefully the base is still in good condition. Another option would be self leveling concrete but not that keen on pouring a slab of that (although not out of the question).

2500 lbs of tank (or so), so if I use feet with 1" of surface over 8 legs, that's over 300 PSI for each foot, which I'm sure would squeeze plywood considerably, just curious about how much.

Or should I not even bother and build a box for the bottom that the legs attach to and use composite shims to level?

 

[mcgyvr]

A floor made of what?
plywood? what type?
feet with 1" of surface... is that the area of the foot or diameter or what?

You can absolutely use adjustable feet and likely wouldn't dent anything unless these are spiked feet or something and you didn't use enough of them..

2500 across 8 feet would be like a 300lb load for each to carry.. A quick look shows you aren't going to come across a self adjusting foot with such a small base diameter rated for that weight (assuming 1" is the diameter you meant..) you will be in the 2" or so min range and at that point will likely not cause any permanent indentations on plywood..

 

[sfsuphysics]

Well the floor is bare now, just the underlayment 3/4" T/G ply (pine or fir I'm guessing?), going to finish the floor around the tank stand when it's all installed whenever that may be not under the tank. As mentioned I might throw in a sheet of 1/4" under just to not dent the subfloor, perhaps some water proofing on it as half of the tank is going to be "behind a wall" in a fish room, the rest will be the finished room.

Sorry for being very lazy/sloppy. 1 square inch of surface area for each foot. I mean I guess I could easily test the compression by putting my fat butt on a 1/2 square inch object to see how much it would compress (that'd be well over 400PSI).

You must not be looking at the same stuff I am, or are looking at the cheapy ones.
https://www.grainger.com/product/S-W-MANUFACTURING-Leveling-Mount-14H412
Here's one with only a 3/4" base and it's got a 700lbs capacity, although I do see quite a few 1/4" diameter bolts with only 250lbs so you're excused

But is 300 PSI really that acceptable for feet?

 

[mcgyvr]

Yeah I was looking at the "non-marring" feet versions at mcmaster as I thought you might be using them on wood floors. They have substantially lower load limits vs full steel/metal feet..
I was trying to find the punch/shear limits for OSB/AC ply but am at work and people keep asking me to do stuff.. The nerve of them..

 

[Gorgok]

Just as a counterpoint... a person in high heels can really push down with a bunch more force than that...

 

[sfsuphysics]

And as a counter counter point a person in high heels wont be standing still for years at a time

 

[Gorgok]

Neither does a hammer blow, but that will dent wood in a hurry.

I use 4 feet on my 75 + 40 metal stand, i think they are only 2" in diameter. Rating was either 4000 or 5000 lbs.

Real wood might even be coaxed back to smooth (from any of the above) with some steam if it ever is needed. Basically run an iron over the area on a damp towel or mashing the steam button. As long as the fibers aren't torn (like from a deep enough hammer blow) its pretty forgiving.

 

[Member No. 1]

Why not 1/4" thick x 2" squares of aluminum under each foot to spread the load.

https://www.amazon.com/Remington-In...1524128660&sr=8-6&keywords=aluminum+bar+stock

 

[sfsuphysics]

Definitely was a thought to shove a bigger something under the feet. Curious how effective it would be if the aluminum wasn't centered under a foot, because I really want to bring the flooring in the room right up to the edge of the stand.

 

[Member No. 1]

How thick is the flooring?

 

[davocean]

And as a counter counter point a person in high heels wont be standing still for years at a time

I agree, live load vs dead load is not a fair comparison.

 

[mcgyvr]

Personally I would get leveling feet with about a 2" diameter foot.. Use 8 or so of them (rated for the load) and never look back.. It will NOT dent the floor.

 

[davocean]

I would also make sure you get good quality stainless so they don't rust over time.

Personally I prefer to keep it simple, I've never heard of shims failing, but I have levelers, and yeah, they do make them able to carry a pretty substantial load, I just think what a headache it would be to deal w/ one that failed while tank was set up, so w/ that thought I do agree if you go w/ them, don't go minimal on load capacity or number of them.

 

[sfsuphysics]

Personally I would get leveling feet with about a 2" diameter foot.. Use 8 or so of them (rated for the load) and never look back.. It will NOT dent the floor.

Here's a problem, are there 2" diameter feet that have a relatively small (1/4") bolt? My stand is going to be made out of 8020, and I'm limited to how large of a hole I can bore (tap) from below.

 

[davocean]

1/4" bolts living in earthquake happy san fran...eek

 

[Member No. 1]

Here's a problem, are there 2" diameter feet that have a relatively small (1/4") bolt? My stand is going to be made out of 8020, and I'm limited to how large of a hole I can bore (tap) from below.

I just built my own stand from 80/20.
What size are the legs?
On mine I used 40-4080 for the 4 columns and was able to use
these on the bottom https://8020.net/40-2135.html
and these feet https://8020.net/12194.html and screws https://8020.net/12200.html

 

[Member No. 1]

Did you ever said what size tank this is? If so sorry I missed it.

 

[sfsuphysics]

Wow 4080 stuff? You basically made 2x4 legs out of aluminum, that couldn't have been cheap

Legs are going to be 25mm legs, so using an M12 bolt ain't going to cut it

And I never did mention the actual size of the tank, just the weight, the size is a 200g tank with a 4' x 3' footprint.

 

[davocean]

That's a substantial load, hopefully it's not too out of level relying on tall exposed pins, plenty strong w/ force down straight on them, but shaking in earthquake area as heavy of yours would make me a little uncomfortable.
I would probably be inclined to have shims down as well as a safety, but then I'd probably just use shims alone if it were me.

 

[sfsuphysics]

Interesting question about the sheer on those bolts. A little super quick digging (aka google) found info showing a 1/4-20 bolt has a sheer strength of 1500 lbs (of course depends on other factors as well), then trying to figure out how much sheer would actually be applied in an earthquake... well that is the hard part, but did find a formula by an earthquake retrofit company that has a formula used for houses, well my tank is a baby house right? And it was the most easiest formula that didn't require much thinking Basically 0.2 x Weight, so 2500 x .2 = 500 lbs of sheer. Now could it be more? Sure, but I'm guessing if "the big one" hits then me worrying about the bolts on the tank is the least of my worries, plus I would think the bolts of the stand would also be suspect as well.