Last summer I had time to do this projekt to finish.
I had three metal rims and idea for lasting grill. So just take grinder out of toolbox and get to work!
First step, I cut out edge from two rims that they fit nicely to each other.
Second step is to cut center out for two upper rims. Small grinder fits nicely inside of 15" rim.
Third step is to find some crap metal to make grate for center rim. To spacing for grate metals, I just use 5mm metal piece and then weld them straight to rim.
Fourth step, I use one rim center to adjust draft under the grate level. Hard to explain it but I weld metal plate to center of rim and also one for disconnected rim center. Then I drill hole 6mm center of metal plates connect them with bolt. Now I can adjust level of draft little bit better. Metal stick comes out for rims side for sliding "valve" on and off.
Fifth step is to make little hatch for adding wood. I just drew lines to side of rim and use grinder with thin blade to cut it off. Very accurate job, because I use same piece to hatch door. Then little cleaning to edges and welding hinge at place. Handle is just piece of metal plate and "lock" is bent metal stick. Hatch opens just to raise it little. You just have adjust pieces to fit nicely.
So then just put rims together and start grilling!
Grid I bought, because it cost about 4€, so no effort to make it by myself.
Sorry for bad english, but hope you understand my instructions. :)