Here are some photos of the construction of my ammobox forge.
I got the ammobox from the army-surplus up the road from me. The air pipe inside is an old scaffold pole, the plate half way up the forge is an old side panel from a transit van.
It’s not clear from the photos, but there is a removable plate resting on the top of the Tuyere, with holes drilled to allow the air though but stop large pieces of coke falling though.