80/20 aluminum acceptable deflection

Harpo · Jul 22, 2023

I'm building a stand for my sump and I plan on using 80/20 - 40 series (40mm). Using their beam deflection calculator, I get the following:

.0132 inches over 52 inches with two fixed ends
.065 inches over 52 inches with supports on 2 ends

1) how much deflection is OK?
2) what is the difference between 2 fixed ends vs supports on 2 ends

Thanks

Doctorgori · Jul 22, 2023

I’ll lurk but my .02 cents; I don’t like ANY!!
Just curious, what are the tank/sump dimensions?

Harpo · Jul 22, 2023

52 x 24, about 65 gallons

Doctorgori · Jul 22, 2023

I’m no expert but I used 30 series and if 40 series is thicker than I’d bet you could span 3-4’ w/o issue …
This is at the bottom? what are you using to terminate the legs? Wheels or leveling feet? or just those plastic squares … How high off the floor is it?
Reason I ask is I’d put a short leg midway regardless.
You got a rough drawing/plans

Reefer Reboot · Jul 22, 2023

In your screen shot you do not have the profile load entered, so you may not have done this right. Exactly which T-slot profile are you going to use?
Fixed end is a piece that is supported by brackets at each end. Supported end is when the ends of a horizontal piece rests on top of a vertical piece. (See https://fandl8020.com/t-slot-aluminum-bar-use/ for visual)
Also keep in mind that each long beam will only be carrying a little less than half of the entire load as you have a front piece, back piece and two side pieces to spread the load across.

KStatefan · Jul 22, 2023

Fixed on two ends means attached to other structure.

Supported at each end means the ends are free

I would use the two ends supported calculations. It is hard to get fixed ends the way 80/20 is bolted together.

Reefer Reboot · Jul 22, 2023

Is this close to what you are envisioning? You say it's for a sump but this is drawn for a tank so I'm kind of lost as to what you're looking for.

Harpo · Jul 22, 2023

Thanks guys.

This is simply a flat frame out of 40 (40 x 40mm) series extrusion with casters in four corners. The only legs are the 3/4 adapters.

Harpo · Jul 22, 2023

Reefer Reboot said:
In your screen shot you do not have the profile load entered, so you may not have done this right. Exactly which T-slot profile are you going to use?
Fixed end is a piece that is supported by brackets at each end. Supported end is when the ends of a horizontal piece rests on top of a vertical piece. (See https://fandl8020.com/t-slot-aluminum-bar-use/ for visual)
Also keep in mind that each long beam will only be carrying a little less than half of the entire load as you have a front piece, back piece and two side pieces to spread the load across.

Is profile load the weight of my sump? 65 gallons (520 lbs)

Harpo · Jul 22, 2023

Reefer Reboot said:
Is this close to what you are envisioning? You say it's for a sump but this is drawn for a tank so I'm kind of lost as to what you're looking for.

Yes, except remove the legs and add casters

PotatoPig · Jul 22, 2023

All the load will go to the legs.

The horizontal pieces on these stands, and frankly any stand, are so much more flexible than the vertical pane of glass on the tank they’re not able to draw anything more than nominal loading from the glass.

In a rimmed tank (Aqueon, etc) the tank should be designed to load only at the corners.

Rimless tanks you’d have to look at the manufacturer guide on stands, but fundamentally you need to provide legs at a suitable spacing.

The horizontal pieces are there to hold the legs together and to either provide a rigid enough connection to the legs to prevent the stand tipping over, or provide a substrate to attach panels to that will then provide stability.

Harpo · Jul 22, 2023

Reefer Reboot said:
In your screen shot you do not have the profile load entered, so you may not have done this right. Exactly which T-slot profile are you going to use?
Fixed end is a piece that is supported by brackets at each end. Supported end is when the ends of a horizontal piece rests on top of a vertical piece. (See https://fandl8020.com/t-slot-aluminum-bar-use/ for visual)
Also keep in mind that each long beam will only be carrying a little less than half of the entire load as you have a front piece, back piece and two side pieces to spread the load across.

At F&L Industrial Solutions, we use a target defection of 1/10” or under for most t-slot structures. If a bar has a chance of bending more than 1/10”, then we usually redesign with a stronger bar. So it is important to remember that target – a tenth of one inch or under. If each of the 52-inch beams carry half the weight, then my deflection is down to .1748 inch.

But is this applicable for aquariums?

topjimmy · Jul 22, 2023

I'm building a stand for my 75 rimmed with 4545 light. I think you would be fine with 4040 for 65 gallons. If you search for 8020 there's a nice article and discussion about it. 3030 is probably fine for anything under 120 gallons according to the author and he's built quite a few.

Reefer Reboot · Jul 23, 2023

Harpo said:
Yes, except remove the legs and add casters

Something more like this? Just a rolling platform?

I threw in the center casters just for good measure. Are you going to put any type of table top on the stand? Is your sump glass or acrylic? It's best to get all the details figured out in the planning stages.

Harpo said:
Is profile load the weight of my sump? 65 gallons (520 lbs)

Yes, it is all of the weight that will be placed upon it, tank, water, rocks, equipment, etc.

Harpo · Jul 24, 2023

Thanks Reefer Reboot, that looks great

My sump is 8mm acrylic. There will be a 1/2 piece of PVC as a base and sheet of open cell foam on top of that.

Reefer Reboot · Jul 24, 2023

Harpo said:
Thanks Reefer Reboot, that looks great

My sump is 8mm acrylic. There will be a 1/2 piece of PVC as a base and sheet of open cell foam on top of that.

You're welcome. Just for your peace of mind, if you build it per the mock up, you will be disbursing the weight across 7 beams. In doing so, the deflection will be approximately .0054" (about a human hairs width.) An acrylic sump should handle that easily. Add on the 1/2" PVC sheet and the foam and well... yeah, no problem.

You do have me curious now, why the rolling sump if you don't mind me asking?

Harpo · Jul 25, 2023

I lost my leg in a car accident. While I received a prosthetic leg, I have not mastered it yet. Not that I'm going to be moving these around much, but I like the ability to push it around and not being dependent on others for help. I was inspired by Than @ Tidal gardens.