This can be done with threaded plumbing pipe, which is often called "Black Iron" pipe. This stuff is available at most Home depot stores. You will need two short pieces to cross the beam, two "Tees", a longer piece for the main pull up area, two short pieces for the horns that go past, and two caps for those ends. HD has a threading machine to cut this pipe to length and rethread ends, or you can buy factory cut small sections known as "nipples". You will need to find two pipe wrenches to get the whole thing together. Now to clamp it to the bottom of the beam you will need four clamps that can be found at any electrical supply house. The counter guy will know what you mean when you swagger on up and ask for a "Korn clamp". Might want to google it first to see what you are talking about. As for pipe diameter, you are going to have to figure that out at HD. I'm guessing 1" trade size pipe will be good, but you would know better that I. Two hints, when you assemble everything, do the two Tees and the long bar first. Second, Black Iron is some oily, nasty shit. Clean it up paint thinner and rags before you get too involved, or you will be covered in a black layer of oily stink.
