84 g-body frame boxing

[steve40]

any opinions if boxing the frame is worth it. i have the body off to clean up the floor, frame and do new mounts. i don't have plans to cage the car....want to make an all round car.

thanks,
steve

[Randy67]

Yes, boxing helps quite a bit. A cage would do more, but boxing is still worthwhile. On my El Camino, just welding up between the factory welds on its existing boxed frame stiffened the frame quite a bit.

[exwestracer]

We've boxed a number of these chassis here at the school, and like everything else it helps if done correctly.

Those frames are built of very thin material and are very susceptible to heat warpage. One of the ones done here pulled the center of the frame in more than 1 1/2". Also, be sure to clean inside the rails at least 1" behind where you will be welding the boxing plate.

[monteboy84]

What do you do to avoid the warpage Ray? Alternating stitches and cooling?

-matt

[exwestracer]

Mainly bracing. No matter how you weld it, you are still putting all the heat along the inside edge of the frame. I actually said it wrong in my older post. You end up shrinking the frame in that direction. The rails really like to bow OUT.

As far as welding procedure, the best we have found is to tack the ends and center of the boxing plates, then begin splitting tacks halfway until you are down to 3" sections. Weld 3" at a time, then immediately weld the same spot on the other leg of the same rail (i.e. top, then same spot on the bottom). The trick is to get both sides welded while still hot. Once a spot cools, it is LOCKED, so whatever warpage you put in won't come back out without reheating. Welding opposite sides balances the warpage the best. It's still not perfect... Moving from one rail to the other is a good idea, as long as you follow the above procedure.

[monteboy84]

Cool, thanks. I plan to do a 1x3 X-brace of some sort, so I'll try to limit the shrinkage somehow. I plan to have it vibratory stress-relieved as well, so that should keep everything in check from moving all over when it hits the road afterward.

Do you stress-relieve your chassis' when they're done?

-matt

[steve40]

thanks for the tips, gonna try and get most of the boxing done this weekend...have to see how the weather goes.

[exwestracer]

Cool, thanks. I plan to do a 1x3 X-brace of some sort, so I'll try to limit the shrinkage somehow. I plan to have it vibratory stress-relieved as well, so that should keep everything in check from moving all over when it hits the road afterward.

Do you stress-relieve your chassis' when they're done?

-matt

Matt,
We don't stress-relieve our student projects. Proper fit-up and minimal heat to get the job done are the keys to minimizing stress in a structure. IMO, heat-relieving is the best method as it is directly reversing the process which induced the stress.