Jigging Tubing Before Weld

[IKE]

Originally Posted by s-neff

You can do flat weldments laid out on plywood (with dummy shafts to preserve hole alignment). This was on 192, doing welded drivetrain module frames. As long as the board was flat, we didn't even really need to put much vertical constraint on the pieces - just using a pneumatic nail gun to put wood blocks in to hold everything in place was fine. We'd tack weld one side, then flip it over in the same jig to tack the other side, then finish the welds outside the jig. Some rework occasionally required for warp. All student welds, what do you expect.

On the Mini-Baja race car team in college, we ended up designing 3/4" particleboard jigs for the tube chassis with waterjetted cutouts in the exact design locations for each tube, and laying everything out before welding. It helped that we were using the same particleboard that our tube sponsor packaged the pieces with for transport (free), and that our waterjet time was free from the ME department in return for help with the upkeep.

I have used very similar method for years. Large flat piece of plywood, with a great deal of care on the layout. Wood blocks (pieces of 2x2) pre-drilled and screwed into position to hold the pieces in place.

One problem with this style is if the fixture isn't symmetric, you may want to apply more weld to one side than you should. Also, aluminum heat expansion can be pretty large if you try to do your welds fully within the weld fixture.

If you have the ability to do what 254 is doing with the rivet then weld gussets, I think this is superior joint and fixture. Often "butt" style welds can be compromised during the rigors of play in FRC. I have personally experienced as well as witnessed a lot of failures with this style of joint. Using a weld in place gusset/strap piece is usually the remedy most teams that weld employ into their future designs.