Taku, I'm pretty sure that Kevinkris Wants to get into casting copper and/or bronze.
Yes, coal forges like you describe are still out there, mostly at farm auctions, or perhaps for sale through some of the blacksmithing sites.
I have one myself, a Champion Forge and Blower Works, it isn't exactly a squirrel cage, but uses an impeller that is hand cranked.
I did a lot of work with it, but as soon as I made a propane forge, I really didn't use it much anymore, good coal was hard to find, and I never used charcoal much. Also, propane was much cleaner to use, and it was easier to do forge welding with.
Kevinkris, Yep, there is lots of us firearms folks with some knowledge about other things that are somewhat related to firearms, I worked at a custom gunshop that made front and rear sights, scope rings and bases, bottom metal, and other parts for sporting rifles. That is where I learned about case hardening some of our parts, and also heat treating some of them also.
Most of the little I learned, I mostly remember.
There are many times I really miss that forge.
It was useful for a lot of things.
And, for that learning thing
I figured out about the time I was 30, the older I got the more I realized how much I didn't know, and it got worse every year. The more I learned the less I knew.
That is a curve that is hard to get ahead of.