Playing with fire!

After exhaustive research I decided to try flame straightening. The concept is fairly simple: heat up the metal to around 1200 degrees which is a dull red glow. This causes the metal to expand and yield while being constrained by the cool metal around it. By heating in certain patterns, the metal can be made to shrink in certain ways inducing controlled deformation. In this case a V/wedge shape slightly more than halfway down height of the rectangular tube and over the top causes the beam to bend but not shrink in length which is what I wanted!

I did have to buy an oxy-acetylene setup which was yet another tool, but it worked out. Initially I bought a smaller "B" size acetylene tank and a smaller 80cf oxygen tank to save cost but found the output for the size 4 cutting torch which I used (only the pre-heat function to heat the steel) had a semi-unstable flame after reading up I decided that I was too close to the limit of pulling less than 1/7th of the acetylene's tank capacity per hour so I went up to a larger 135cf tank and the unstable flame issue was resolved.

For the actual flame straightening I'd do both frame rails at the same time, one heat pattern on each rail and then let both air-cool until I could touch the steel and not be uncomfortable. Then I'd move to the next area and repeat. In practice this was 30-60 minutes between each pair of heat inputs for each main frame rail. It took a while but I also wanted to go slow and make sure I wasn't making new problems.