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...g-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-Ind...inum+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]

Originally Posted by sfsuphysics

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]

Originally Posted by 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.

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]

Originally Posted by sfsuphysics

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.

[Member No. 1]

Yes the legs are 80mm x 40 mm or 1.575" x 3.150".

Cheap? Haha! With this new 120G build I'm looking cheap in the rear view mirror!

Stand alone was a little over $1,600.
Then plywood for the top and inside shelf alone with paint was another $150
Stand is not skinned, I wanted the industrial look. I also used 80/20 in the 40-4040 size to incorporate a built in light rack.
Understand lighting $50
Apex 2016 and modules mounted in the end along with a iPad mini for a display, and (4) MP40wQD Controls
Front black sliding doors are removable.

All said and done, was about $1,800

[davocean]

Originally Posted by 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.

I have to wonder how that formula applies as pins sit taller, meaning the more out of level, the higher the pins, the more vulnerable.

My stand held up fine in a 6.3 which is a pretty good one, but yeah I agree bigger than that and issues could be other bigger things...

As a contractor living in CA myself I just pay a lot of attention to this, so far I've never heard of a shim failing.

My other thought is how a lot of our metal fasteners seem compromised these days, and keep in mind stainless will vary in strength and quality, not sure how you can know w/out just trusting the manufacturer that you got what you ordered for sure, so much Chinese crap is substituted for cheaper materials, so don't cheap out, perhaps make sure US made would be my suggestion.

[sfsuphysics]

Originally Posted by davocean

I have to wonder how that formula applies as pins sit taller, meaning the more out of level, the higher the pins, the more vulnerable.

Yeah I'm sure the formula is a very VERY rough generic one used by that particular company that popped up on google just to give a feeling for how much sheer they prepare for when they reinforce the mudsill to the foundation or strap the vertical beams or whatever. Other than that though I can't really guess on how much sideways force will be.

My stand held up fine in a 6.3 which is a pretty good one, but yeah I agree bigger than that and issues could be other bigger things...

As a contractor living in CA myself I just pay a lot of attention to this, so far I've never heard of a shim failing.

No I haven't either, but the idea of feet was basically to allow airflow under the tank in the case that water gets there I'd like it to air out as opposed to having a "box" sitting on the floor, I mean there would be air pockets under the tank, but ultimately no airflow, and if I was worried about what the feet would do to a floor.... I have plenty of experience in reefing with wet floors that aren't allowed to dry

My other thought is how a lot of our metal fasteners seem compromised these days, and keep in mind stainless will vary in strength and quality, not sure how you can know w/out just trusting the manufacturer that you got what you ordered for sure, so much Chinese crap is substituted for cheaper materials, so don't cheap out, perhaps make sure US made would be my suggestion.

True, but sourcing material seems to be harder and harder these days. I mean I got a good source for stainless fasteners, but they don't always have the fasteners I need (in the case of 8020 they don't have the "t-slot" nuts, but I probably can use their bolts on them.

[sfsuphysics]

Originally Posted by Member No. 1

Yes the legs are 80mm x 40 mm or 1.575" x 3.150".

Cheap? Haha! With this new 120G build I'm looking cheap in the rear view mirror!

Stand alone was a little over $1,600.
Then plywood for the top and inside shelf alone with paint was another $150
Stand is not skinned, I wanted the industrial look. I also used 80/20 in the 40-4040 size to incorporate a built in light rack.
Understand lighting $50
Apex 2016 and modules mounted in the end along with a iPad mini for a display, and (4) MP40wQD Controls
Front black sliding doors are removable.

All said and done, was about $1,800

Well I wanted the "fun" factor of playing with an adult Erector set (thankfully auto-correct didn't make that an embarrassing statement!), and in order to justify I had to make sure it would be "cheap", I mean I can make a wood stand for quite a bit cheaper that it isn't funny. But this is going to be my little piece of "art" so having some pretty is a necessities, big issues was sourcing out those fasteners because buying them 8020 they are quite a bit more expensive. I figure the vertical strength can EASILY be held with the size of material I went with, and I do plan on bolting full sheets of plywood in all 3 dimensions that it can move to prevent racking so not worried there.

Who knows maybe this summer I'll find some time and actually get around to building it

[Member No. 1]

Adult Erector set was exactly how I described my stand.
With this new build, I knew it was going to be costly, but I promised myself
that if I couldn't correct all the little PITA things that I don't like about my current 80g, and do everything right, then don't do it at all.

http://www.reefcentral.com/forums/sh....php?t=2661614

Since I am not skinning the stand and the structure would be exposed, I went with the 80x40mm for aesthetics. It's way overkill. You could park a truck on it!
I used all 80/20 fasteners. https://8020.net/shop/40-3362.html

This was in the early stages of construction. It's progressed a lot since then.