I've been using only coke for 28 years. That being said.... forget about the rheostat to control the air, use an air gate, the blower will run free air without issues and the pull of the lever will increase or decrease the flow. The tuyere isn't necessary, I have an air blower,air gate, right angle up to the fire, with a thick grate, right angle to the ash clean out. I can melt 3" sq. by accident. Don't restrict the air, cut it off with the gate....I hate to say it , BUT...that fire pot may ( will ) get red hot so keep that in mind when making the frame. Coke isn't like coal, it's way hotter