Hey,
I've had a few people ask about the subframe connectors I put in my car, so I thought I'd put together a thread on how I did them.
I used 75x50x3mm RHS for the bars. The final length of the fitted bars was 1050mm, I guess you'd add two inches for a challenger?
Because the rear chassis rails are narrower than the RHS I reduced the width of the end of the bars by grinding a 5mm gap 170mm long along the top and bottom. I clamped 120mm of the bar in a vice to reduce that amount to the required width of 45mm leaving 50mm of the gap to form a taper. I beveled the edges to allow a full penetration weld.
I used a 250amp MIG on max to get full penetration and maximum strength. This meant I had to do short beads or you'd blow big holes.
The welds were ground smooth.
Because E body rear chassis rails aren't parallel with the body, an angle was needed to the end that was to slide into the rails. 170mm of the end of the bar was bent at 5°. The same procedure for reducing the width of the bar was followed.
The finished bar. The inside was rustproofed.
For the torsion bar crossmember plate I designed a piece that would also gusset the torsion bar anchor. This design matches the holes in the crossmember of a 72-74 E body, I believe earlier cars only had one aperture on each side for fuel and brake lines, and this hole would be covered by this design.
I had access to a computer controlled plasma cutter, so I cut the plates out on that. I used 3mm steel.
The finished connector. The crossmember plate was tacked to the bar with everything mocked up in the car, then removed and welded solid.
One of the holes cut in the floor to allow the bar to slide into the rear chassis rail.
The rear chassis rail was opened up, drilled for plug welds, and rust proofed.
The bars welded in. First I welded up the plug welds at either end, then I stitched the floor to the bars in short steps, moving around the bars to allow areas to cool and prevent warping.
The floors were welded on from top and bottom. A rotisserie sure made this easier!
The welded up crossmember plate, note the gusseted torsion bar anchor, like the Trans Am race cars had.
There you have it! Please feel free to ask any questions.
I'm no expert by any means, but I did a lot of research into these things before I proceeded, and feel the result should be about as effective as possible!
Cheers,
Aaron
