Smoker barbeque build
Morphing two drums into a cold smoker
W hen my friend Evan Wade said that he was going to build a smoker from two 200-litre drums, I leapt at the chance to cover it as I had been wanting to cover a Texasstyle smoker build for some time. This isn’t quite a traditional offset smoker like a Texas smoker — it can be used in the same way, but this is primarily a cold smoker. Evan is very partial to meat, fish, and especially smoked sausages. He had found the design on the internet and followed more or less the same process as the designer: jmillerid.com/wordpress/category/55gallon-drum-smoker/.
The drums that he sourced had previously contained cooking oil, so they would be safe to use for food. Be aware of what your drums have previously contained, as it could influence the taste or even the safety of what you eat. Beware of drums that have held volatile liquids like petroleum products. Apart from the danger of poisoning they can also explode, especially when empty.
Cutting the drum
This design calls for two drums welded together in a T-shape. That requires cutting the bottom barrel so that it accepts the horizontal one. It’s possible to lay out the shape involved by working the design out in CAD or by developing the shape via traditional sheet-metal development draughting.
To do this (see panel on page 46) you will need to be able to print the resulting design in actual size, so you will need several sheets. You can then wrap the printout around the drum and cut to the line. Or you could just wing it as we did, using a flexible rod and knowing the four points where the curves would meet to draw a fair curve between them that approximated the shape of the developed curve.
The drum was carefully cut with a thin-blade abrasive disc but it could be cut with a jigsaw.
It is important to keep the cut as close as possible to the line or you could find large gaps that would be difficult to fill later when you weld the two together. It took some trimming and some additional work to accommodate the rolling ribs on the horizontal barrel but eventually Evan got a good fit between the two drums. The wing-it system proved quite good in the end and resulted in a good fit for the barrels with only a minor bit of filling at the end.
The next task was to cut a door into the main drum. To do this Evan marked out the door parameters with masking tape. This will also allow you to get a good visual on door size and make corrections easily. With the shape set, he cut along the back edge of the door with an abrasive disc. It’s wise to attach the hinges prior to cutting the rest of the door. You can attach them with screws but it’s a good idea to weld plates in place to hold the screws properly, or simply weld the hinge with plug welds through the screw holes.
First, clean off any paint around the area that the hinges will be welded to. These drums are usually of very thin gauge (20 gauge), or barely 1mm thick, so it’s important not to crank up the MIG voltage or wire speed too high.
With synergic machines like the BOC Smootharc Elite, set the thickness to something like 1.6mm or less. The hinges are stainless and 2mm thick. Weld alternate holes at opposite ends of the hinge to spread the heat and prevent warping. It is possible to run a weld bead along the edge too, but it pays to reduce the voltage to prevent burnthrough. Avoid hinges with nylon bushes as they might not respond well to the temperature.
Make sure that both the hinges are in line and square to the door, especially if you are welding them. With the hinges
The wing-it system proved quite good in the end
in place you can proceed to cut the rest of the door. Do it carefully — you want the door to be able to close reasonably tightly.
The next stage is to reinforce the door and provide a lip for the door to close on. Welding heavy-gauge metal to thin sheet metal is often best achieved with ‘plug welds’ — welds made through specially punched holes in the sheet metal or the heavier gauge. Plug welding works in a similar way to spot welding, where a series of discrete spaced welds hold the piece. The final result can look very industrial chic — like rivets if you space them regularly. Punch the holes with a drill or more easily with a joggler and punch plier as used for automotive body repair.
The secret to welding thin metals with MIG is to keep the metal as cool as possible and use short bursts widely spaced to avoid distortion or burn-through. It pays to move the weld around to prevent overheating any particular region. The welds will be small enough that they will be unlikely to cause any distortion provided that you do spread the heat.
Before the 3x40mm strips could be welded in place, the strips for the sides needed to be shaped into a fair curve.
The ideal means of doing this is with a roller. The roller consists of three rollers set in a triangle with the middle roller able to be screwed down. The strip of metal is passed between the two bottom rollers and the top adjustable one and after each pass the middle roller is tightened down slightly more, causing the strip to bend gradually on each pass until the desired curve is obtained.
Light-duty rollers are quite cheap although they can only roll limited gauges — in this case up to 5mm thick mild steel, which is more than enough for this job. Each strip was bent to fit and then tacked and welded in place. Evan felt that the door itself was a bit thin and required some reinforcement to prevent it either warping or twisting in use. Two more strips were cut and welded to the inside of the rolling ribs, tacked first, then a small bead was run, taking care not to burn through.
With the door set it only remained to add a handle, cut from 12mm square tube.
Now came the messy bit. These drums had been painted on the inside and that paint had to be ground off to prevent it from contaminating the food being prepared through releasing fumes or burning during the cooking process.
If you attempt this, make sure that you wear appropriate personal protective equipment (PPE), including a dust mask. Cover your hair (if you still have any), otherwise you will be washing it out for days.
Once the two barrels are cleaned of paint they can be tacked together. First grind off any paint in the vicinity of the join on both barrels. Place the drums in position and mark the contact for the upper one from the position of the lower drum. Keep the weld tacks spaced to prevent any distortions. Later the weld can be made complete, but in the first instance it’s enough that the two drums are connected.
With both drums joined it was time to finish the layout of the top unit. First Evan tacked strips of 25mm angle iron to the sides and back to hold a series of rods or mesh from which to hang sausages or meat for smoking. The smoke and heat gets generated in the lower barrel. A series of holes needed to be drilled through the base of the upper drum
To keep the doors tightly closed on both drums requires latches
to allow the smoke to come through. These are best and most easily cut with a step drill. The holes should be cut in a diamond pattern, making sure they stay within the lower drum.
Joining the drums
Welding the two drums together with a solid bead is important to avoid air intake and smoke loss. It is also important to avoid burn-through — to ensure that, it’s a good idea to cut the voltage, or, in the case of synergic machines, set the
material thickness to around 1.2mm.
You will still not be able to run a long bead. It’s best to work in short bursts that are well spaced and return to fill in the gaps. Where there are gaps that need filling — no matter how good your initial fitting you will likely have some — build up the gap in a series of runs, allowing the bead to cool between runs. Take some time — don’t try to rush it.
The last process is to mark and cut the door on the lower drum for the burner/ smoker.
The process is the same as before. Cut the rear of the door and fit the hinges and then cut the rest of the door. Punch the holes for the plug welds and bend the curves in the steel strip to fit the curve of the drum. Holding the strip in place with
clamps, tack every other hole and then come back and fill the remaining holes.
To keep the doors tightly closed on both drums requires latches. The latches are attached with pop rivets and serve to keep the door tight to the steel strips at the edges retaining the smoke and the heat. The top drum took two latches and the bottom door took one.
To regulate the airflow, the burner holes should be drilled with a small hole saw along the base of the burner and through a strip of metal that acts as a damper. The damper strip was cut from the remnant of the upright drum so it matched the curvature of the drum. The damper strip is held in place with self-tapping screws set to let it slide to control the airflow.
A handle was made from a piece of 25mm dowel. Attaching the strip in place with tape or by tightening the screws on which it slides allows the step drill to cut through the damper strip and the base of the drum, at the same time ensuring the holes line up.
Evan cut a circle of steel from the remainder of the upright drum to act as a controller for the smoke release in the top drum. The circle was bolted to the side of the top drum and holes cut with a set drill through both the circle and the drum. A handle of 25mm dowel was then attached to the controller to regulate the smoke release.
The burner for the smoker is set in a basket in the lower drum to allow it to be removed easily for cleaning. In our case we used an office wastebasket in lieu of a more permanent solution. The final step is to paint the whole thing in a high- temperature paint. Two standard barbeque grills fit in the lower part of the top drum to allow meat or fish to be laid there, and rods or mesh on the upper shelves can hold sausages for smoking.
Evan Wade laying out the shape of the two-barrel joint
Cutting the lower barrel
The cut barrel
Cutting relief for the roller ribs
Cutting the back of the door
Cleaning the inside
Weld in short runs
Cutting the holes in the damper
Welding the hinges on the lower drum
Cutting the burner door
Thickness setting for attaching the two drums
Cleaning up the welds
Lighting the smoker
Drilling the smoke release