Rolling large metal hoops

When he got it home, we built a station for it to mount on out of channel iron (we can lay stock in the channel and pry it up into position), and just high enough to be comfortable to work with. Caster wheels on the bottom of the legs allow us to move it around as needed. He also happened to have an electric motor with a 90-degree reduction gearbox already attached. He mounted that underneath the channel and used a couple of chains with different gears to get the power to the drive roller and slow it down even more.

I agree with the others -- you'll need a really hefty machine to bend channel. Can you get your hands on something 5' in diameter that you could use as a pattern to bend the channel around? If so, you could gather up a bunch of clamps and a torch and get the job done. Find a way to clamp the end of your channel to your 'pattern', then start heating the channel and slowly bend it around, pinning it in place as you go. When you get to the end, tack weld it and you should be in good shape. Just a thought.