I wanted to (1) practice brazing, and (2) build something cheap, i.e. not a frame. I have also been reading a lot of the hype surrounding French Porteur bikes, and really like the concept.
So I went on a quest for local materials to build a porteur rack for my commuter/errand bike. As luck would have it, my local Autozone stocks 5/16" brake line, which I assume is mild steel. It is quite bendable using automotive tubing benders. I also had a length of 1" by 1/8" steel strap.
I used Stay-Silv white paste flux, and whatever generic brazing rod my local welding shop had on hand. It seems to work fine, but I am too inenxperienced to know the right stuff from the wrong stuff.
I fashioned a crude shadetree jig to attach the vertical supports. It actually worked great, and the final result is quite staright and fits the bike really well.
The only thing that doesn't seem to work well is using an axle to support the dropouts. The axle absorbs so much heat that it is very difficult to get things the right temperature for long, and I ended up overheating the shit out of it, and still not getting much penetration. I probably should have just tacked the dropouts and then finished them out of the jig.