Tongue weight capability of 2x3x.125 steel tube at 21"?

[Kawana87]

Hello everyone. I'm building myself a half-rack for weight lifting that included 2 overhung support beams above from which to hang a safety strap incase of a failed lift. They are made from 2x3x.125 steel tube (they're Oriented with the 3" vertically). The tube are overhung by 21". How much weight could they support statically, but also what could they sustain from say a 3ft drop? Edit: image added for reference.

 

[Lnewqban]

Welcome!
The weakest link is the base.
It will fail by bending prior to the element you are asking about has a chance to fail.

 

[Kawana87]

Welcome!
The weakest link is the base.
It will fail by bending prior to the element you are asking about has a chance to fail.

Ah, I hadn't considered that. What info would you need to figure the fail point of the base? Same overhang, 2x3x.125 tube, 75" between top and base. Realistically till be more than strong enough for anything I could lift but I'm curious what the math says.

 

[berkeman]

Thread closed temporarily pending Moderation...

 

[berkeman]

Ah, I hadn't considered that. What info would you need to figure the fail point of the base? Same overhang, 2x3x.125 tube, 75" between top and base. Realistically till be more than strong enough for anything I could lift but I'm curious what the math says.

After a Mentor discussion, the thread will remain closed for safety and forum liability reasons. Here is one of the comments from that Mentor discussion:

There is more to making a safe rack than just the bending strength of the top pieces. There is also the bending strength of the bottom legs, the buckling strength of the vertical columns, the strap alignment, strap connection, stability, weld strength, and impact load. The impact load is several times higher than the static load, and cannot be calculated accurately because the strap spring constant is both unknown and nonlinear.

We cannot do a full engineering analysis for you, but can make this suggestion: Build it, then drop test the heaviest weight the longest possible distance. Do the drop test by having two people pick up the weight so that both people are standing outside the safety rack. That way, if it fails, it will collapse between the people so nobody will get hurt.