This thread is really two threads, Charle's frame design and the brazing / welding stuff. If Charles doesn't mind I think we should split it at some point?
I'll make a couple of more comments about Charle's frame project. First, I am not sure that a Maserati birdcage is a reasonable project for an average home builder. It doesn't strike me as an entry level project to design yourself, or to do all the work to carry it off. I'm glad your starting to get serious about the FEA, because that's what you need to do to give yourself the education to do this. I hope that your software package will be able to carry this off, because I think you can see that enering the table of numbers to describe every joint in 3 dimensions is a lot of work. The more tubes the more work
So one thing is that space frames and ladder frames are different. That means that the black tubes would be the heavy ones in a ladder frame, but not a space frame. The big loads are in the top of the frame. Everything is hanging off those tubes and they are in compression. When you choose size for tubes in compression, you need to consider how slender they are. A tube in tension can be any length and be the same strength. A tube in compression gets weaker according to it's length in a very complex way, because buckling is a complicated thing. This has been discussed at length here in a thread by aero_bro. If the tube is more then about 30-40 times it's width long, you need different math to calculate it's strength. You need to know what the compression load is on every tube in the car. At least to some degree. This is actually why it looks like a birdcage!
You need a load path from the front coilover to the rear coilover. The cockpit is a difficult area for this, especially with regards to making it stiff to twisting. Perhaps you can post a picture of a birdcage frame for us to refer to. Most space frames make obvious efforts in this area.
It will be difficult to put a real ( that is spec. ) roll bar into this type of frame because what do you connect it to? A bunch of 1/2" tubes? There can be real devils in this area - the original probably didn't have much.
I've become a firm believer in building a spec ( SCCA or NASA ) roll cage and then connecting the rest of the car and frame to that. It's not a Birdcage Maserati, but it's safer, doable and you can drive it on a track. There's a whole world of bodywork you could put on that.
I agree. The design and construction of a birdcage has little to do with the differences between welding and brazing, other than the fact that the birdcage was. Sort of. I don't have a new picture of my project, or the potential frame I'll be building but it's sitting at home right now rendering one.