Introduction: Homebrew Cold Smoke Generator
Runner Up in the
Low & Slow BBQ Contest
Control your smoke independently of your temperature! Generate as much or as little smoke as you desire, for as long as you like! Cool and smoky, hot and smoky, anywhere in between, it's up to you!
Step 1: Optionally, Add a Cap
A cap will allow you to stop the smoke generator at any time and save the remaining wood for the next smoking session.
Step 2: The Players
a 12" (more or less) piece of 3" Schedule 40 aluminum pipe (available from Online Metals, Speedy Metals, McMaster-Carr Industrial Supply, etc.)
One (or two, if you decide to make the optional cap) 2 7/8" fence post caps, available from your local fence supply.
A piece of stainless steel screen, from your local hardware store or industrial supply.
A fitting for your air hose, a washer that fits over the threaded part of the fitting, and a brass pipe coupling that acts like a nut to secure your air hose fitting from the back side.
Not shown here:
a short length of 4" metal dryer hose ducting
a sheetmetal 3" to 4" duct adapter
a 4" duct cap
some duct tape (I used Gorilla Tape)
a couple of 4" hose clamps
Optionally, if you decide to make the top cap, a wooden drawer pull knob and a short screw.
Please, be safe and avoid the use of toxic materials, like zinc or cadmium plated steels.
Step 3: Take This Pipe And...
...go to your local fence supply. Try to find a loose fitting fence post cap for the optional cap end, and a snug fitting cap for the air end. Bigger is better for the air end - if necessary, you can drill a hole into the cap for a nut and bolt and chuck it up in a drill press or drill motor. A wood rasp or coarse file will make short work of any cap that is too large. Try to file a tapered shape so that the cap will enter the aluminum pipe about halfway, and then use a hammer and a block of wood around the ribbed part of the cap to seat it firmly.
Step 4: Then Assemble the Air End Cap
The cap has been drilled slightly larger than the threaded end of the air fitting that you are going to use. Using the washer as a spacer, thread the brass pipe coupling on the backside so that the pipe cap is sandwiched between the fitting and the coupling...
Step 5: Like This...
...snug is good...
Step 6: Air End Assembled
Step 7: Cut a Piece of Screen to Fit
Cut a squarish piece of screen and bent the corners up so that it fits snugly inside the pipe. Recess it slightly to allow room for the pipe cap to fit inside.
Step 8: The Bottom End Complete
Now tap the cap into the end of the pipe using a hammer and a block of wood around the rib of the cap. Loctite or high temp silicone can be used if the fit is too loose, but if you are careful it shouldn't be necessary.
Step 9: The Smoke End Connection
I used a 4 x 3 duct adapter and slipped the 4" end over the pipe. I measured how far down the pipe seated on the taper, added about a half inch, and...
Step 10: Smoke End Continued
...found something of suitable height to mark the perimeter. I cut the excess off with a cutoff wheel in a 4 1/2" angle grinder, but a hacksaw or metal snips will do just as well.
Step 11: Little Things From Big Things
The piece on the right is discarded. The piece on the left is deburred inside and out with a file or piece of sandpaper.
Step 12: It Looks Like This
The 4" end fits over the pipe and seats on the tapered part of the adapter...
Step 13: And This
A view from the inside.
Step 14: The Smoke End: the Smoker Connection
I'm sure all of us have different smokers, so here is where you can let your imagination run wild!
Not wanting to add any holes to my smoker, I used a 4" duct cap as an adapter, drilled a hole in the center, and then marked it so that it lined up with my vent opening. I punched a couple of holes in the appropriate areas, bolted it to the vent, and taped it securely.
Step 15: A Happy Face!
Another view of my vent adapter. I used the sticky-backed foil HVAC tape to hold it all together.
Step 16: And Voila! She Smokes!
Some duct tape, a couple of hose clamps, and we're off to the races!
I used a well-used charcoal chimney to support my smoke generator simply because it was available, but I kind of like it because the smoke generator gets very hot during operation and it isolates the generator from the dog, the grandkids, etc.
I have an 80 gallon air compressor in the garage, and I have an airline with a flow control and regulator that supplies my air. I realize that not many people will have that luxury, so an inexpensive aquarium air pump will do well as the air source. It certainly does not require much in the way of air to generate billowing clouds of smoke, but it does need to be continuous. Imagine gently blowing across a smoldering piece of wood...it doesn't catch fire, but it will smolder for hours and hours...
I have found that the best way to start my smoke generator is to put a layer of wood chips in the bottom of the generator and drop a well-lit briquette or similarly-sized piece of lump on top of it. Then I fill the rest of the generator with a mix of chips and chunks, put the duct hose on and then adjust the air flow until I have the amount of smoke I want. I have gotten better than 3 hours of smoke out of my generator this way, and I am able to control the amount of smoke all the way from light and wispy to billowing clouds by regulating the amount of air supplied. Because of the metal ducting, the smoke does not contribute to the heat inside the cabinet, so cold smoking is definitely within the realm of possibilities of your homebrew cold smoke generator!
I have about $40 or $50 tied up in this project, and a couple of hours to fabricate and assemble. It was a fun project and turned out much better than I anticipated.
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