Thanks Evan ---
Just a technical note, I used round tube because in this scale it's easier to use (and get by with) but in the real world, the sections of pipe are not actually round, at least that's how they develop out as when I draw it correctly. The reason is the angled connections are actually round because there's a bearing race there which means the short straight section parts are a round to angled round tranistion, and the middle straight section is really an elipse in shape
This below might help with the explanation. If you cut a round pipe at an angle, the resulting cut face is an elipse, in reverse, if the angle cut is actually round then the piece of pipe is really eliptical in shape