If I made the air flow and ash dump (tuyere) out of the 4 1/2" pipe would it be to big?

I suppose it depends on the fan also?

What kind of fan would I need with this 4 1/2" pipe? (Why 4 1/2" pipe? Because it is laying here asking to be put on the new forge build).

Could I get away with this?

http://ittybittyurl.com/2EMu

Or would I need to step up to this?

http://ittybittyurl.com/2EMv

Could get something like this and maybe blow the fire outa the pot. Not bad price thou.

http://ittybittyurl.com/2EMC

 

Naw, 4.5" pipe isn't a problem, it's the size of your air grate that helps determine how wide the base of your fire is. I trimmed the number of openings in the air grate in my coal forge quite a bit. I don't know which of those fans would be best, I use a blow drier or Coleman Inflateall the raft, mattress, etc. inflater blowers you can find in sporting goods sections all over. I grab them at yard, garage, etc. sales when I see them. I have both 12v and 120v and they make a pretty impressive fire. I also have a champion 400 crank blower on a rivet forge. Keep your eyes open and do NOT get in a hurry something will turn up. Ever think of making a bellows? They're easy to make.

All that said I almost never burn solid fuel let alone coal. Without sampling and performing tests I don't know which seam of more than 35 is the good smithing coal so I burn propane.

Frosty The Lucky.