Hi all -
I built my first forge, and I'm looking for a little feedback. I made the forge by cutting the bottom off of an old steel vacuum tank. Mostly because I had it, and it had legs on it, and it already had a threaded hole in the bottom that I could attach an air pipe to. I used a 5/8" cast iron drain cover to cover up the air pipe (is it really a tuyere if it's just a pipe? seems pretentious! ). The air pipe itself is 1" inside diameter black pipe.
You can see the rest of the tank in the background - I thought I might cut the other end off and cut it in half to make a long trough with a horizontal tuyere in the future.
I lined the tank bottom with potters clay mixed with some sand. I tried kitty litter first, but I mixed it too wet I guess. After two weeks it still wasn't dry. My wife (a potter) graciously donated some clay that was drying out to the cause. It cracked some, but seemed to provide some insulation. The paint on the bottom of the forge didn't burn off anyway.
I attached a shop vac to the pipe to act as a blower. Note to self: Shop vacs blow WAY too much air, but they sure get the coal burning in a hurry! I ended up turning on the vac for about 5 seconds at a time to get the coals going good.
The up-shot is that it all worked. I was able to heat up steel very nicely and work with it. I made a set of tongs and some J-hooks to hold some pulley wheels to make a sliding barn door.
Anyhow, I know I need a MUCH less powerful blower, or at least some kind of valve so that I can reduce the air flow dramatically. I was wondering about the clay? It's not very thick - perhaps an inch or so near the grate - mostly to sort of contain the coals over the grate. It's probably a half inch thick around the outer edge. I'm not sure it's necessary at all? I've read that cast iron forges can suffer from thermal shock, but this is made of steel (mild steel probably). It's about 1/8" thick steel. Way thicker than my bbq grill that I burn the same coal in. Granted, I'm not forcing air through that fire.
I've been using natural hardwood charcoal, because it's available at the local wal-mart. I can get good blacksmith coal (bituminous?) but it's an hour away. Would the clay be necessary with that due to higher heat?
Any other thoughts? Is a round forge better/worse than a rectangular one? What other changes might you make?
Thanks in advance for any feedback!