Larry Peceniak has caught the cone kiln bug and has made several versions out of lightweight sheet steel:
I used 2’x3’ 30 gauge galvanized steel for duct work from Home Depot. The metal is pretty flimsy, but it gets the job done.
Looks like he uses pop rivets to hold it together. We'll have to get a report from him later on how long this lightweight materal lasts, but for now he's having a great time. He says:
The first char with the new kiln was outstanding. I charred 15 gallons of split 2x10 pine from a home construction site in about 2 hours while sitting on my patio enjoying the fire! The cone kiln I can actually set in a patio fire pit that I bought and it works great. Now I can sit on my patio, do a char, and enjoy the fire while I’m just sitting with my wife enjoying a glass of wine.
Here are the pictures: