Ok back after visiting the first one of these upright ones I built..
I had already cut this keg as a crab boiler when I was asked to make
a drum burner that didn't drop ash .. so this is the result ..


the later versions are cut off at the bottom of a keg to act as the ash pan ,as this makes the center hole for the spear an inlet for more air and an ash out let so air can flow..
I cut thin disk cuts with the angle grinder radiating out from the center...
they burn well and you can slid a cast bbq plate on to cook as well..
cheers