The deal Lonnie is that you haven't yet mastered out of position welds on round tubing. Your first question is enough in and of itself to see you don't yet have the experience for a chassis. You won't believe it but here are many, many others that came before you trying to do the same thing. You say you can't go more than 90* on piece of tubing. That, you will need to practice. Your teacher may have had that experience but at this point you don't. Not yet, anyway.

The couple of guys like Sundown (who certainly knows what he's doing) and Old Skool make good points, not on assumptions but on what you've actually posted to the thread. You asked the question in the first place when before starting this project, you should have known. Your choice of machine is a bit suspect as well. It's a fine machine, but this sort of work is usually done with a minimum of a 180 amp class machine. That's not to say you can't do it with the MM140 but it's not the best tool for the job. An MM211 or a 252 would be a better choice. Then you state you can't do out of position rounds very long. Nothing wrong with learning, but those three things alone make others with more experience question the wisdom of tackling such a project at this point.

Most of these projects never see th light of day anyway. The builders lose interest or get to the point they are over their head and it get abandoned. Don't get me wrong, I'd like to see your project succeed but at this point you still have more learning to do.

Good luck!