Tire rims are steel, brake drums are usually cast iron: welds to cast will typically shear or tear out if stressed. Having a suddenly two piece forge might make for a bad day. Bolt it together, the holes are already there.

Sometimes pictures help. Hope these do.

 

We are looking at upgrading to forge larger items. We may retro fit this with a table or shelf. The air plate does a good job of spreading the air flow to the whole pot, as it sits on the bolt heads, and air comes up around the edges as well.

Thanks for the pictures Archedan, I like the drum setup you have, a brake drum on a drum  :P. I am thinking of just drilling through a pipe cap and screwing it onto a pipe coupler on the  side of the drum, here is a link to the Blacksmith that convinced me to get into it. I don't know him personally, just from his videos, but he give very good advice on a range of things.

 

It's a great video for an easy way to make a forge that he put together. I did find it odd though that he goes through the trouble to make an educational YouTube video, then throws a jab at anyone who watches educational YouTube videos.