beam support for brew stand

[Bensiff]

I have never taken an engineering class in my life and I'm a decade away from physics so help me along here. I'm finishing up welding a single tier stand and trying to determine if I need center support or if that is just over engineering that everyone seems to do. I suppose the question is, can the beams support the weight with a small enough deflection that it won't negatively impact the systems stability or cause a permanent bend in the metal?

The specs, brew stand is a 48"Lx16"Dx22"H framed cuboid (outsides only) using 1.5" 14 gauge (.083") mild steel built to support 3 20 gallon kettles. Assumption of max load would be all 3 kettles full plus the kettles weight of approximately 30lbs each (just going with water weight of 8.34). So each kettles max weight would be 30+(20x8.34)=about 200 lbs.

So, I found this nifty deflection calculator:

http://metalgeek.com/static/deflection.php

For the center load spec I assumed 500 lbs (I just don't remember the math to figure out the weight distribution so I'm just assuming the outside kettles are lending 3/4 of their weight to the center). Anyway, the nice little deflection calculator tells me the beam will only bend .0614". As there are two beams I would suppose that halving the deflection would be reasonable, so my stand with no center support would only have a deflection of .0307" which seems like it is so small there is no reason to concern myself with added bracing as I would have no worries of bending the metal or the kettles become appreciably off balance. So, for you engineers others who know this stuff, please let me know if this works out or if my complete lack of knowledge is shining?

 

[JDGator]

5gallons of beer is pretty close to 50lbs. so 60gallons would be 600lbs. i'm just using round numbers.

am i miss understanding you kettle setup?

 

[JDGator]

now that's if your 3 kettles are full of water all at the same time. and for the purpose of your build i would stick with that number. hot water is not fun when it lands on you.

any pics to help clarify your stand dimensions.

 

[Stealthcruiser]

Post a pic of it, unless you're still in the planning stages.

.083 wall is pretty stout stuff! with good welding, and some corner "gussets",( if that concerned about it), and you should be good to go!

No engineer here, just a sheet metal fabricator, with 'bout 30 years experience.

 

[JDGator]

i would use another upright if your spanning 48". really don't need it but it will help with any flex.

 

[Stealthcruiser]

i would use another upright if your spanning 48". really don't need it but it will help with any flex.

Duh, guess I missed that part........

48", yes, you need a center support between the span, "metalgeek" or not!

 

[jhoyda]

Figure 23- Beam Fixed Both Ends- Uniformly Distributed Load

Distributed load (w)= 600 lbf/48 in= 12.5 lbf/in

Span (l) = 48in

Modulus of Elasticity of Steel (E) = 30 x 10^6 psi

2nd Moment of Area of Square Hollow Section (I) = 0.159 in^4

Deflection at Center = wl^4/384EI

Deflection = 0.036"

But that is for one beam, you have two so the deflection would be half that so 0.018".

Or, you could do what most engineers do: build it, test it, if it is too "wiggly" add some more support

 

[Bensiff]

Figure 23- Beam Fixed Both Ends- Uniformly Distributed Load

Distributed load (w)= 600 lbf/48 in= 12.5 lbf/in

Span (l) = 48in

Modulus of Elasticity of Steel (E) = 30 x 10^6 psi

2nd Moment of Area of Square Hollow Section (I) = 0.159 in^4

Deflection at Center = wl^4/384EI

Deflection = 0.036"

But that is for one beam, you have two so the deflection would be half that so 0.018".

Or, you could do what most engineers do: build it, test it, if it is too "wiggly" add some more support

So you are getting half the deflection the calculator I found figured for. .018 for this application may as well be zero. And, like I said, that is only factoring for a span, not the sides being welded onto legs that are welded to another beam which would further resist deflection. But, I will still fully load the system to make sure it doesn't need a center brace...it would really suck to have to sand and weld after the 10 coat paint process and color sand job is done.

 

[Stealthcruiser]

10 coats and color sanding?

Ya' gonna' brew on it, or put it in a museum?........

 

[jhoyda]

So you are getting half the deflection the calculator I found figured for. .018 for this application may as well be zero. And, like I said, that is only factoring for a span, not the sides being welded onto legs that are welded to another beam which would further resist deflection. But, I will still fully load the system to make sure it doesn't need a center brace...it would really suck to have to sand and weld after the 10 coat paint process and color sand job is done.

My calculation accounts for that, that is why the calculated deflection is less.

 

[Bensiff]

My calculation accounts for that, that is why the calculated deflection is less.

Ah...nice, my non-engineering self didn't pick up on that...is that the "2nd moment of area" part?

 

[jhoyda]

Ah...nice, my non-engineering self didn't pick up on that...is that the "2nd moment of area" part?

Haha, no the formula in the link is for a beam with fixed ends. The formula you used is for pinned ends which can rotate, fixed ends do not.

 

[Grossy]

Does it look it it will hold the weight or not?


Here is my $12 brew stand. If I wanted to I could park my car on top of this and it would not fail.

No cross beams, no other support than the ends. Sometimes the simple approach will work just fine.

 

[JDGator]

That looks like rectangle tubing which will be able to handle the weight better then the square tubing.

 

[HeavyKettleBrewing]

Does it look it it will hold the weight or not?


Here is my $12 brew stand. If I wanted to I could park my car on top of this and it would not fail.

No cross beams, no other support than the ends. Sometimes the simple approach will work just fine.

I would put some lag bolts through the cross members on top.

 

[Grossy]

I would put some lag bolts through the cross members on top.

Thats what this thread is about, where do you draw the line on engineering and strength.

I could also brace under the cross member with a 2x4 "jack stud". But the truth is that there is no way that 500 lbs of weight (max load) is going to sheer through eight 2.5" drywall screws, after over 20 brews with this rig, I'm confident as to it's strength.

 

[Bensiff]

Finally got some empirical data, which with my clear lack of engineering knowledge, is the way to go for me. Do to not having the TC fittings yet to close off some of the ports I was only able to load the system with one 20 gallon kettle and then two old kettles, one 15 gallon and one 12.5. I put the 20 gallon center and the smaller ones left right, I figured I got about 42 gallons total. The stand does not have casters on it yet so the bottom rectangle sat on the garage floor allowing it to remain static for a good measurement. Anyway, measuring from the bottom beam to the top at the center point the difference between loaded and unloaded was just shy of 1/8" measured from a tape measure (only have a good 16" straight edge so the tape measure was as good as it got). So, that was a little more deflection than I expected.

Given it wasn't fully loaded with three 20 gallon kettles I did the most reasonable thing I could think of and jumped on to add another 170 lbs to the system. That wasn't quite good enough though so I jumped up and down (without letting my feet leave the frame as that would be dangerous and way overkill on applied force). Anyway, I didn't have the ability to measure deflection, but the frame held rock steady to the point that the water in the kettles didn't even ripple.

So, my conclusion is that 1.5" 14 gauge mild steel tubing in a cuboid frame can easily manage the weight of a 20 gallon system with no need for additional bracing.

 

[Stealthcruiser]

Thats what this thread is about, where do you draw the line on engineering and strength.

I could also brace under the cross member with a 2x4 "jack stud". But the truth is that there is no way that 500 lbs of weight (max load) is going to sheer through eight 2.5" drywall screws, after over 20 brews with this rig, I'm confident as to it's strength.

Simple and functional!

Just for your info: Drywall screws only have what miniscule strength they possess, in the head of the screw.
That is the ONLY part of them that is heat treated, basically so you won't round out the drive recess.

You're better off with deck screws for a wooden structure.........(just for peace of mind!)