pic: REV Robotics building system

[MechEng83]

Originally Posted by EricH

Moment of inertia (and in this case, that's MASS moment of inertia) is something you'll tend to hit somewhere around 2nd-year engineering coursework, possibly a hair sooner. It's not that hard in concept; the simple definition works out to how much torque it takes to rotate an object about a given axis. Now, the actual application of that definition, and the formulas to help determine it, are where that gets fun, as the shape of the object in question plays a role (which is why that was brought up in the explanation). If you're interested in running through some of the math, let someone know; that can be arranged...

I'm pretty sure the discussion is about AREA moment of inertia (units of [length]^4). Though your description of mass moment of inertia (units of [mass]x[length]^2) is related to rotational inertia, it's not germane to this discussion.

Regarding OP's question:
We found the extrusion to be heavier than the thin-walled tubing we've previously used for frame elements. Are you possibly referencing 1/8" wall square tubing? If so, I'm fairly confident the tubing is stiffer in bending and torsion than the Rev Extrusion. As far as axial stiffness (along the length) it's going to be proportional to the cross sectional area, which is proportional to the weight/unit length for the same material.