I'm quite new to this smoking thing. My wife had one back home made from two 45 gallon drums. She had been talking about getting one or me making one but whilst I was researching it this flimsy cheap thing turned up. Its fire bowl in my opinion leaves a bit to be desired it has a small trivet style fuel tray and an ash pan, and in common with other bbqs I've seen in the UK the bars are too wide and let a lot of fuel fall through into the ash pan (it could be Lump wood charcoal here is too small) It has a very poor air supply and the first few attempts were almost self extinguishing , even after buying a pair of real weber fuel trays which again had holes that let a lot of good fuel fall out. I appreciate for smoking you don't want a huge fire but even so you do need it to stay alight.
Step 1: Improvement
My first step was to stop so much fuel falling into the ash pan. I achieved this by wrapping some 1/4" square weld mesh over the trivet. (something I've been doing to the fuel support grid in the normal bbq for several years) The trivet was a bit unstable but I found a wok ring in a kitchen cupboard that proved to be just the right size to support the trivet and still allow air flow underneath the coals.
Whilst this produced a small fire that burnt well with no charcoal in the cold ashes bellow . It didn't form a very stable surface for the box of wood chips and some coals fell off the edge into the ash pan where they went out.
The mesh is galvanized. Now there are warnings out there about heating zinc, the problem is with inhalation of zinc oxide vapors. Whilst this could get hot enough to do this:
A) it's only going to occur once,
B) All that smoke and carbon monoxide is probably worse for you
C) By the time the fumes have left the smoker its no longer hot enough to be vapor just particles.
As for the possibility of zinc oxide contamination of the smoked food, zinc oxide is sold as a mineral supplement, so no issue there I think.
Step 2: Advancement
It occurred to me if I secured a section of mesh between two wok rings I'd have a supported fuel bed, with air flow, sides to stop fuel falling into the ash pan and they would also support the box of wood chips.
A trip to my local oriental foods wholesaler yielded a pair of wok rings at about £8
I still had plenty of the weld mesh a 500cm square panel was £5 from my local garden center its meant for building averies or bird feeders I think.
My salvaged screws box produced 8 small self tappers they are about 3mm(1/8") diameter and 15mm (3/4") long (5mm 1/4" would have done)
I used a center punch to mark 8 evenly spaced point around the inner lip at the narrow end of one of the wok rings. I drilled a 1.5mm(1/16") pilot hole then place it on top of the second ring and drilled through that as well and screwed the two together (this would have been easier if I'd taken the time to enlarge the first hole to 3mm) I then positioned the rings so they were nicely aligned and drilled the hole opposite the fist and Secured the position with another screw I then drilled pilot holes in the remaining 6 positions.
Next I marked the rings so I could re assemble them in the same align ment. I removed the 2 screws already in place and opened up all the pilot holes in the top ring to 3mm. I placed a section of mesh between the two rings and fitted all 8 screws and tightened them fully. I then trimmed the mesh and folded it up the top ring. With a little advanced planning I could have arranged it so it covered the holes in the top ring)
Step 3: Opperation
In use so far, less than a quarter of a starter funnel of coals is need to fill the top ring,and burns for about an hour and a half maintaining a temperature of about 180-200F. A gentle rake in position and the addition of another couple of hand fulls of charcoal keeps it going for a couple more hours. I'm considering blocking off half the holes in the lower ring as I think I may have created too efficient a fire. So far the holes in the top ring haven't permitted any coals to fall out so the need for mesh over them may be unnecessary. Prior experience with the weld mesh suggests it should with stand weekly use for about 6 months and the rings look as if they will out last 2 or 3 remeshings.
It turns out the Weber fuel trays are meant for bricketts, due to the chemical binders my wife doesn't want to use that for smoking. but a weld mesh liner worked quite well on them as well for use in the normal grill.