Homebrew Cold Smoke Generator

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Introduction: Homebrew Cold Smoke Generator

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

Main ingredients:

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

...DONE!

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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    33 Comments

    I looked around and could not find any Stainless Screen around town. But I did have some scrap .060 alum laying around. The first one I cut....I did it with a 3in holesaw not thinking that the slug would be undersize....So I had to redo it and cut it with a 3 1/4in holesaw. It was aprox .020 oversize and a sander cleaned that right up. I also added a 90deg fitting so ash would not fall directly into the venturi. Don't know if that was necessary? I'd been wanting to build one of these for a couple of years now. I laid out a criss cross pattern on 1/2in incerements and drilled holes all in it to Swiss cheese it. I have pix's but it will not let me post them.

    Very nice design!
    How does the pipe stand up in the briquette starter?
    Is the small black line on the ground the air supply to the generator?
    Since the volume of smoke is low, do you think a coil of 1/4-1/2" copper tubing (say 10' ran through ice water for really cold smoke) could be substituted for the flex ducting? This would simplify the hookup from the pipe to the smoker.

    Alot like the Smoke Daddy which sells for $125+. Good design.

    This has inspired me. I've made several versions but have changed things up since I can't just walk into a store and get fence caps here. I've used a length of pipe "capped" on both ends with a coffee can. The bottom is fixed to the pipe with the air feed into it and the top one is removable to use as a cap. Fit the exhaust hose over that (drill some holes in the top first to let the smoke out) and you just remove the top coffee can to add more chips. I'ts cooler too. This is very cheap to make too. I guess I might post it once I solve a problem. The pipe was something I had laying around and can't find the same size cheaply. My local hardware store has some cheap but it's galvanized so I'm worried about contamination. Does anyone know if you could use galvanized pipe and coat it with something like grill paint? Would that have any effect. Especially, since my new design has a fitting on top (actually a galvanized stove pipe cap) and another air fitting and some copper line. You can then snake it into small side holes in a normal gas grill instead of smoker. Put a bottle over the end of the pipe and you end up with very strong liquid smoke! Oh thanks danneauxs

    Thanks very much for taking the time to detail this project.  I am going to add one of these to my UDS.  I watched another video and on a similar product and just knew that this was a simple project but what alluded me was what the materials were and the sources. I was searching for more hints and found your instructable.  I did want to know what volume air pump you would recommend. Is around 5,000 cc/min sufficient? Thanks again for sharing this.

    This pretty nifty.  I ordered my pipe today.  I was wondering what kind of fitting would be used for an aquarium pump.

    Nice job. I like the portability this creates. Any chance we can get a clip of it in action?

    2 replies

    You're in luck! I'm smoking some spares today. I like to smoke thin and wispy over a long period of time, but I'll crank her up for the video and produce some serious smoke for demo purposes. Keep in mind that I don't try to cook with that volume of smoke! Believe me, you will love the immediate control you have over your smoke! Be warned, though, that the aluminum tube and the metal ducting get uncomfortably hot during the smoking process, so you will need oven mitts if you need to add more wood while it is still generating smoke. Let me figure out what to do with the video I just made and I will try to post it later today. Thanks for asking!

    Try using double walled exhaust ducts to shield your hands from the heat generated in the smoking process and then vented through the aluminium ducts.  I installed one of those tankless hot water heaters, and the installation directions called for the double walled stainless steel exhaust ducts (I think they call it type "D", I'm not sure about that...anywayssss...) Instead of going out and buying the more expensive double walled ducts (or buying anything at all), I had some left over 3" & 4" ducts that I just put the 4" over the 3" and used spacers(washers) and self taping sheet metal screws to secure the ducts together and bingo double walled ducts at the best price in town, even at twice the price, its still the best price in town....for those who didn't get that joke...the price was FREE b/c it was left over material.....lol  Anywaysss I digress......Use that tip for the smoker or anything.....just  take it light....
    --KB

    I love the idea and most of the design, however i must question you logic on one point. you advise against coated pipes yet use galvanized fence caps whice contains zink / lead in the galvanizing? I would find a different way to cap the ends or wory of slowly giving my familt lead poisining or worse.

    1 reply

    Umm...these are cast aluminum fence post caps. They also offer steel fence post caps. Use a magnet if you are unsure.

    Great instructable! I'm in the process of building a smoker out of an old filing cabinet, and this looks like the perfect addition.

    Just checking on the size of the pipe before I put an order in - is this the right size?

    Nominal 3"
    OD 3.5"
    ID 3.068"

    1 reply

    Yup, that's the one! But being the eternal cheapskate that I am, I saved a couple of bucks and bought the random length (10"-12"), which came in right at 12" on the nose. It will help to take the pipe with you when you go to find a fence post cap, if you can. I bought one cap that was made in China that was too big and had to be filed down, and another cap that was made in India that fit just right. I filed the Chinese-made one down until it fit real tight and then drove it in with a block of wood and a hammer, but then I broke it trying to take it out so I could take pictures! So I think it would be best to use a cap at the bottom that fits snugly enough that it won't fall out but loose enough so you can pry it out with a couple of screwdrivers if you need to for some unforeseen reason. I went to both Lowe's and Home Depot in my area and neither one of them carried fence post caps for 2 7/8" fence posts...they were all for 2 3/8" posts. Make sure that you have a fence post supply near you that you can get the larger caps from, or you might have to downsize the aluminum pipe...

    This is the best instructable I have read yet and the first one I will do. Have a smoker that looks just like yours! I smoke a lot of deer jerky and have tried making my own bacon and have always had a tough time getting constant smoke at low temperatures. I was actually going to start looking for a "better" smoker but now I don't have to! Thanks for all the time you put into making this and sharing with the world (wide web).

    1 reply

    Thanks so much for your kind words! I am so happy with the way this works I'm just looking for things to try...we smoked some sharp cheddar cheese the other day. It didn't noticeably raise the temperature in the smoker, but it was a warm (mid to upper 80s) day, so that might have had an impact. I was going to put some ice in the water pan if the temp went up but it didn't. I also came up with an "upgrade" of sorts...I was using the charcoal chimney to support the CSG and then disconnecting the CSG to use the chimney to start the charcoal for our Weber kettle. The air hose was taking a set and getting hard to disconnect from the air fitting at the bottom with my big clumsy hands, and I was worried that maybe the heat might melt the plastic part of the fitting at some point, so I replaced the fitting with a street elbow and a 3" pipe nipple to extend the air fitting out and away from the bottom of the CSG. The air fitting is now outside the perimeter of the chimney for easy access, and the chimney is now dedicated to supporting the CSG. We bought another chimney for lighting charcoal. BTW, I smoked the cheese for an hour, which turned out to be 'way too long...too smoky for our tastes (using hickory). I love oak wood and I should have used it, but hickory is so cheap and so plentiful in my area...

    this is cool

    lol good call " I didnt inhale"- bill clinton after being charged with smoking pot...lol

    Maybe something to try between BBQ's...turn off air suppy,put cherry or apple wood chunks in pipe,and put end cap in place.Fill the chimney starter with scrap wood and ignite.You now have the in-direct heat method of making charcoal.