First, excuse my english. I'm not a native speaker. I try to be as clear and simple as possible. Photographs may help you more than my gibberish. It could be worse, you could have to listen to me, so you would laugh so much that you couldn't do anything.

As promised, my english translation of the instructable I had posted. But first, the pseudo-legal crap:

I'm in no way advertising for the products or tools I use. I have no sponsor. I don't endorse any of these brands. I just have no time to doctor each shot to anonymize the brands.
I only report how I solved my problem. I give no waranty that my solution will work for you.
This realisation, and all the processes it relies on, implies risks. You are responsible for what you do. You have to PROTECT yourself.

Summary: I am an individual amateur, and don't invite you to anything. If in doubt, abstain yourself.

Final remark: I give you the global process, I will spare you every trial and error, etc... Sorry, some shots are missing. I was in my enthusiastic creation process, or crying after hurting my fingers at some point. I think it is evident enough anyway.

I entered the "creative misuse" contest, just for the fun of it. Well... the prizes are quite appealing :-)

Step 1: Presentation

Copper is fashion. Industrial look and feel. Quite easy to engineer. My wife loves it.

BUT: copper isn't made to withstand heavy weight. And it will tarnish with time. You are warned.

Step 2: Conception

Let's be clear. I live in an old house, where there were never any real flat surface, nor square angle. Really. We checked for years. And that's a real pain in the spirit level. Well, I just put it there because he was the exact width that I will use for the cross beam. Don't look further, it is the only right surface in this closet; believe me, I checked.

What we need is storage room, for... everything you have in such a house. If it's hidden, it's better. And, you know what, we have such a space, under the stairs; halleluia!

So let's convert this twisted closet (you have no idea) to a wardrobe.

Design constraints

Remember? No square angle. Wow. Did I mention the stairs are the revolution ones? And by the way, the roof you see, up the photograph, it's adobe, projected on wooden toothpicks. You don't want to hang something in this, especially a rod on which you will hang clothes for a family of 5.
We will anchor the rods in the walls.
Forget about metrics (no square angles, again). I don't know that, so I will cut each piece at each step.

General Idea

I will build a "T" shaped rod that will go in the walls.
The one on which the porte-manteaux will hang will be grossly parallele to the wall facing the door.

Yes, I know, many products exist, that would do the job. Just buy it. But they are all either impractical, or inadequate, or ugly, or all of that. Plus, where would be the fun?

Assembly method

The copper pipes are designed to be soldered. I assume you could glue it too, using an epoxy for example.

But I bet that just screwing everything will be enough. And I want to be able to disassemble the thing in case it needs maintenance.

I found a way that keeps the screws away from the eyes.

Step 3: What I Used (materials and Tools)

Well, that's where I will need a really good dictionary!

Sorry for Oncle Sam, I use only metric system, like all civilized lazy amateur (but how the hell do you find your way with inches, yards, ounces, etc...? I wonder).

Materials

First and foremost: copper pipe. The plumber kind. I bought some, sold in 2 to 3 meters rods, in 18/22 mm. In France, we find it in big coil too, but I didn't trust my capacity to make it right, and I doubt it would withstand the heft of the clothes.
Remember copper pipe is engineered to carry inside pressure, not mechanical vertical weight.
"T" connectors. You make 2 supports with one. So I bought 2. Choose a connector that matches the rod diameter, of course.
Some plastic, like Polymorph or Instamorph. Still hard to find in France, but easy on the web. No heat involved in a wardrobe, so it's my choice.
Wood rod, with a diameter allowing to slide it into the copper pipe. I found it, but had to wedge it.
So,... a wedge. I used some popypropylene wedges, used here to apply wooden flooring.
Screws and inserts adapted to the material of your walls.

Optional:

Glue. Once again, I didn't use it.

Tools

Well, the usual things:

Spirit level (the one I stuck in the closet.
A measuring tape.
Drill, screwdriver, tips and borer according to the diverses operations.
Metal files, to soften the edges of your cuts (a flat one and a round will do).
Pencils (with emphasis on the "S", I tend to lose them...)
A hacksaw.
Protective equipment. Remember, you are responsible for your own safety!

I will spare you the optional tools. Workbench, pipe cutter, you name it...

Step 4: The Supports

Not sure it's the good noun. But you understand: I talk about the thing that will keep the rods to smash with a big noise on the floor.

To cut it, no magic. A vise, a hacksaw, and it's quick - the copper is soft, compared to steel.

Don't forget to soften the edges.

Then mark and drill the holes through which you pass the screw.

Well... the tricky part. The copper is soft, if you screw your support as is, you will flatter your support against the wall. So you have to fill the gap. I used the moldable plastic for that.

You may use something else: screw insert, wood half cylinder...

BUT, remember that you will put the rod in the hollow superior part of the support; so shape your material accordingly.

Step 5: The Cross-beam

Easy!

The only tricky part is to cut at the good size. Warning: you can't pass the pipe through the T connector. So your cross beam is in 3 parts.

The wood rod is screwed inside, it adds rigidity.

Step 6: The Rod

Not far from the end.

Do the same as the cross beam with the wood and the wedge, and that's it.

Step 7: Assembly

Remember, nothing is glued.

Sorry, on the photographs, the thing is already screwed, but it is the next step...

Step 8: Screw That!

Well, I must tell I was a little afraid; there was a big disgracious gap between the rods and the supports. And I don't think that it would keep in place by magic.

But don't worry: remember that there is a wood core inside the hollow pipe. So it is quite simple: drill and screw it all together, on each support and... voilà!

Mark, drill, screw, and that thing will resist an army of kids addicted to ritaline.