Quote Originally Posted by jerry clayton View Post
I can't see how the thing you show would add anything meaningful tothe joint. It might resist some twisting moment but basicly your welding strategy I believe is faulty and you will actually create a joint that is weaker by welding the two tubes to that piece inside with a wide bead, whereas if you used some holes so that you could do a rosette weld you could get some shared shear resistance.

Looking at the drawing of the frame member, you need to analize just what forces apply where---the power will be applied forward along the bottom rail at where ever your lower torque arms attach but they will probably be a couple feet forward of the axle so the joints shouldn't have anything but carry the weight of the rear portion of the body.
Jerry,
As far as adding anything meaningful, there is no difference between this reinforcement and what you recommend in the rosette welded holes other than, I am welding in a long slot rather than a series of holes. Both tubes will be individually TIG welded (not one big weld) to the inner structure. The long welds will actually provide more shear resistance, over a wider footprint, then three holes. As far as the "H" section goes this is probably not really necessary but I can see it will add a lot of crosscar stability to the joint and probably some shear also. Keeping the joint from "breathing" goes a long way in preventing weld failure.
Thanks for your comments, you are making me think this through and I know the joints will be stout.
Mark