55-gallon drum smoker
Friday, 25 December 2009
This past fall I took an evening welding class at a local technical school and got very excited about making things out of metal. I already had an old stick welder that I didn’t really know how to use, and I ended up buying a MIG welder–the Hobart Handler 140 from Northern. After making lots of small assemblages out of scrap metal I managed to build a stool and a couple of plant stands, but I had bigger plans.
There’s something special about creating useful objects. A smoker is a nice combination of supremely useful (preparing sustenance) and slightly frivolous (do you need a smoked pork butt to survive?). There are certainly faster and more efficient ways to cook food, but damn smoked meat is good.
I looked around at commercial smokers and custom hacks and talked to a few connoisseurs, and decided the Weber Smoky Mountain was a good design to start from. It’s simple and effective, and in the end it mostly convinced me that the design need not be complex.
Something appealed to me about using the iconic 55-gallon drum as a building block, so I went out and bought a couple from the local scrap yard. One of them even got immediate use as a beer barrel at Crushtoberfest!
A little sketching on different configurations, and I decided a ‘T’ shape would be simple, stable, and functional, and provide plenty of opportunity to practice the MIG on some thin sheet metal. I laid it out in CAD, which made it easy to generate the intersecting curve between the two barrels.
I printed the curve at full scale and wrapped it onto the barrel, traced the curve, then cut the barrel with a jig saw. The first dry fit was amazingly close (way to go, CAD!) but there was still a lot of grinding here and there to accommodate the ribs in the barrels.
I measured and marked the door openings on the barrels and cut them out with the jig saw.
The next step was grinding the paint off. The last thing I wanted was burning paint fumes getting into the food, so every bit of paint needed to go. If I were to do this again I would find another way… sand blasting, chemicals, burning it off, etc… anything but taking it off little by little with an angle grinder. I’ll admit the Gator brand paint & rust remover discs I found at Lowes were very effective (if a bit pricey at 9 bucks a piece). But my shop is now coated with a thin layer of green paint dust, much of which ended up in my nose and likely my lungs.
On the first day of grinding I wore a respirator and glasses but nothing else. After washing my hair three times in a row to get the paint dust out I learned to don more protection. For the insides of the barrels I also used an LED headlamp.
As the barrels were made of surprisingly thin metal (20 gauge) the door openings needed to be reinforced with some angle and rolled sheet metal strips, which were plug welded from the outside and tacked from the inside.
The doors also needed reinforcement, in the form of sheet metal ribs tacked onto the undersides.
I welded small pads onto the barrels and doors for the stainless steel hinges. These pads were ground flat then drilled and tapped.
After grinding the rest of the paint off I welded the two barrels together. This was a challenge, since the metal was so thin and the fit was far from perfect. To prevent burn-through and warpage I used a “stitching” technique where you put a quick tack weld across the joint, wait a second or less and put another tack next to it, continuing like that for about an inch at a time. Apparently this puts less heat to the metal than a continuous bead, but the end result looks very similar. With a little practice I was even able to bridge relatively large gaps between the barrels with short, controlled beads that build on each other, kind of like ants crossing a stream.
I shopped around looking for off-the-shelf replacement grates that would work but none of them were big enough for this guy. So I bought about 80 feet of 1/4″ diameter 304 stainless rod (from onlinemetals.com) and cut it to length on the abrasive chop saw. I scored a piece of 1x pine on the table saw at the proper spacing to use as a jig, and clamped the rods down. The MIG would have been perfect for welding the grates, but I would have needed to buy stainless wire and a separate tank of tri-mix gas (65% argon, 33% helium and 2% CO2). The stainless itself was already pushing my budget, so I bought a handful of stainless welding rods and used the arc welder.
Next I drilled holes for the dampers– two sets of three holes at the top and two sets of four holes the bottom. The top ones were made like typical grill dampers with a round rotating plate. The bottom ones needed to be on a curved surface, so they slide along the surface rather than rotating.
In both cases the moving damper is retained by screws, so I drilled holes and tacked some steel nuts behind them.
I then drilled a series of holes to allow the smoke and heat into the top barrel. My step drill bit did an amazing job, but the cordless drill still went through two fully charged batteries getting the job done.
Next I tacked on some small support tabs for the grates and six small sections of square tube as feet.
After a thorough deburring, wire-brushing and degreasing with alcohol, I set about applying a high-temperature grill paint. There are several available but Rustoleum High Heat Brush On was a) available at Lowes and b) didn’t require curing at a high temperature like most of the products I found online. Unfortunately it only comes in black, which is actually slightly brownish. They recommend only applying one coat, which I agree with after trying to touch up a few spots after drying, resulting in some weird gloss differences. I then tried the spray can version of the same paint, but found it to be flat finish (vs. the brush-on which is satin). The lesson here is get it right with the first coat because you really can’t go back and hit it again.
While the paint was drying (24 hrs… it’s oil-based) I fabricated some handles out of a 1″ maple dowel. I don’t have a wood lathe but the metal lathe did the job. A few coats of Polycrylic and they’re ready to assemble.
The smoker can be used in one of two different ways– with charcoal in an expanded metal basket or with wood on a traditional fireplace grate. I suppose I could retrofit some gas burners or even electric heating elements, but that’s a project for another day.
And last, final assembly. I bought a 3″ smoker/grill thermometer online, and used some nickel-plated chain for the lid stays. I also fabricated a sheet metal “drip tray” to cover the holes under the food and deflect some of the heat.
I figured my brother-in-law Pete would make much better use of this than me, so we gave it to him for Christmas. Here he is opening it…