Step 1: Optionally, Add a Cap
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...
Step 4: Then Assemble the Air End Cap
Step 5: Like This...
Step 6: Air End Assembled
Step 7: Cut a Piece of Screen to Fit
Step 8: The Bottom End Complete
Step 9: The Smoke End Connection
Step 10: Smoke End Continued
Step 11: Little Things From Big Things
Step 12: It Looks Like This
Step 13: And This
Step 14: The Smoke End: the Smoker Connection
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!
Step 16: And Voila! She Smokes!
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.