Rectangular Tube replacement for Channel

[cmaddox03]

I've got a gooseneck livestock trailer that needs modification. I cannot get the front low enough to level out the trailer. The gooseneck portion of the trailer is comprised of C8x11.5 channel with gussets at the hitch & trailer connection. I want to replace the C8x11.5 channel with a 6"x? rect tube with ? wall thickness to gain 2" of vertical hitch adjustment. How do I determine what size tube to replace the channel? Do I use the moment of inertia in the Y plane since that is how the channel is orientated? Do I need to be concerned with the moment of inertia in the X plane?

The I_y for C8x11.5 is 1.32 in⁴. If I just have to match or exceed this value, I could go with a HSS5x2-1/2x1/4 tube that has a I_y= 3.28 in⁴. This would be great to gain 3" more of adjustability / clearance.

Thanks for the help.

 

[Bagman2524]

You need to compare the I (moment of inertia) value to determine the deflection difference between the 2 shapes. You need to compare the S (section modulus) or Z (plastic section modulus) to determine the strength difference between the two shapes. I would select a HSS size that has I and Z y axis values equal to or greater than the C8 x 11.5 size.

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