As you know, pole beans can grow outrageously tall. CRW cages basically top out at 5'. To me, they aren't the right material for the job. You can get flat sheets of CRW and stand them up on the 8' length. You'll need to support them well though.

I visited with a local gardener this morning not too far from my lot, and he's using 20' cattle panel. He has them stood on end about 1' - 2' into the ground, then bent over to form a tunnel with approx. 3' distance at the bottom. They are very a thick gauge of galvanized metal, and he said they cost about $20/panel. They are definitely lifetime quality.

He plants on both sides of the tunnel and the plants run up and over. It's a nice set up, and at 4' wide, each panel is making 8' of linear row. It's definitely a smart method, and a good investment. I would suggest skipping the CRW for beans and get the cattle panels instead. The CRW might be good for half runners, but I don't see pole beans being manageable on CRW.

What if I make the 5' ones, then cut others in half and fasten it to the top, making it 7'? Any taller and I can't reach them anyway.

For tomato plants 18" diameter is a bit small - 24" + is much better.

For cukes - 2 plants work ok in one of them, 3 if you are into over-crowding plants. Pole beans, no. Not only not tall enough but not sturdy enough either to support the weight of pole beans in any wind. Even for tomato plants they have to be well-staked and they aren't nearly the wind screen that pole bean plants become.

And no you won't get the same yield - much less soil involved in a circle than in any linear feet amount - and the round shape encourages over-laping vining that reduces production.

Dave

I use CRW for pole beans, but I make sides and tops out of galvanized electrical conduit pipe, then fasten the CRW to it with bungee cords. It works great for pole beans.....but they do grow over the top, since mine are only about 7' tall. I also use my kids' old swing set and lay CRW across the one side of it. the cucs love it. I have used cattle panel arches in the past and didn't have a lot of luck with winter squash and pole beans....which I think pole beans especially prefer the size of wire on CRW, rather than the cattle panel thick bars........but everybody is different in their experience.
Here's a pic of my trellises. I haven't had much luck growing those vining things in shorter cages. To stabilize these trellises, I hammered a 3-4' metal stake in along side the bottom sides of each pipe. Works great! Sometimes I do need a ladder to reach the top beans though.