Homemade Downdraft Gassifier Wood Buring Stove

Nicely done, Miguel. FYI, if you’re ti Pot is NOT the non-stick lined kind, I recently found an easy way to get the soot off… set the pot, empty, on a butane stove (snowpeak giga ti, etc) and let’er’rip… burns the soot right off and leaves the pot unharmed (other than a cool bluing effect)

Not this ONLY works with pots that are JUST ti, no rubber handles (which as I type this I can’t remember if your’s is) no non-stick lining. IMO, the best pots for this are the Snowpeaks…

Nice stove Miguel,

I may try out this stove idea with some other cans and see if it works, I like the whole wood stove idea, but so far out of the ones I have made, one is too large and heavy, and another is small, it works , but can be hard to light. and can only hold a little wood at a time, so you have to keep refueling.

Thanks Joshua for the inforamtion about getting soot off the Ti pot. Since my pots don’t have a coating inside your suggestion just might work. But I think that I might just dedicate one of my pots to wood stove cooking. The soot will make the pot more effective.

Ryan, I, too, have wondered about using a small wood stove. I’ve successfully used the fan-driven zip stove for hiking and I suspect the stove I have shown here can do the same. The pencil-thin lengths of wood used to fuel the fire are small enough that collecting them around the area where you would use the stove presents little problem for obtaining enough fuel, and feeding the stove with such small kindling really doesn’t take a lot of work. My only concerns are if it would be more difficult after several days of heavy rain and if I could maintain enough fuel while climbing in alpine regions, without disturbing the fragile habitat.

Downdraft gassifers, unlike simple, single-walled wood stoves, are lit from the top. Once the wood gets burning the red-hot layer of embers at the bottom of the stove serves to turn the burning wood into wood gas, which is the fuel that runs the stove. It’s similar to the gas put out by liquid fuel stoves.

Miguel, You said “The stove is made of two tea cans with airtight lids”

Are these “Tea” cans Matcha tea? I have a bunch of these but they are a little heavy. Most of mine are the smaller size cans as the tea stays fresh if it isn’t opened. I do have a few empty larger cans put away someplace and I have a few other cans that look like the type you used for the inside.

I might try a stove made from one of my tea cans. I would cut the bottom off the can and use it but replace the side of the can. I would make a new side out of Aluminum or Titanium. Then I would use the cap from the can and see if I can lighten the stove a bit.

Hi Bill. How are you holding up these days? Are your treatments getting any easier? I do hope that you will finally be able to get a full recovery soon and you’ll be able to get out to the mountains for your walks. After all, you’re making all that equipment for a reason!

The inner can is a Chinese jasmine tea can made of a steel that is slightly thicker than that used in soda drink cans (the macha tea cans I’ve bought tend to be made of heavier steel). The outer can is a generic tea can that I found at a thrift shop. The steel is heavier than it need be, but since I don’t have access to a lot of titanium without spending an arm and a leg, I just went with this for now. I think your idea of using titanium would be great! Certainly would make the stove a more reasonable weight, but I also figure that since I wouldn’t carry a fuel cannister or fuel, the weight of a wood stove is offset by the weight savings in not carrying a cannister/ fuel bottle, or fuel itself. The downdraft gassifier burns very hot, with the top vents actually shooting out flames, much like with an open top alchohol stove. Just one caution… make sure the grating at the bottom of the inner can is open enough to allow the resulting ash to fall through and to allow as much air to get into the inner can as possible. By having a removeable top it is easy to clean out the accumulated ash at the bottom.

Here is the original article I first referenced when starting to research inverted downdraft gassifier stoves.

This article was also very helpful for ideas.

Miguel,

just to confirm, you’ve made an inverted downdraft woodgas stove without the gas wick, correct?

Joshua, actually I’m not exactly sure what the “wick” is. I think it’s meant to mean the air space between the double walls of the stove wherein the wood gas rises from the bottom of the inner can, up along the sides and out of the vents at the top of the inner can. The “wicking” I think refers to this movement of wood gas through this “flue”. I don’t think it’s a physical wick. The Bushbuddy also has this double wall construction. It’s the double wall that is important, and why the single wall wood gas stoves I’ve seen seem to be missing a key component. At least that’s how I think this all works.

HOw do you light the stove.

do you have to use a starter fluid?

I just made a double wall wood gas stove, based on Miguels stove above. I have not tested it and dont have a pot stand yet, But I think it is a good little design, it took about an hour to make, and weighs 5 oz. And fits in a snow peak 900 mug
The space between the two walls and the bottom of the inner and outer cans is only about 1/3″, I dont know if this will make it so the stove performs poorly.
Here is a picture of the holes on the inner wall

I did not have any wire mesh so I drilled a bunch of 1/4″ holes in the bottom of the inner can. It worked on other wood stove designs, so it will work fine…I think

I used a progresso soup can for the inner wall, and a pumkin can for the outer wall, (the 31oz bean can on the right is the exact same size as the pumkin can)

I am working on the pot stand and will test it, and post some pictures of the stove in action this weekend

Hey cool, Ryan! I think maybe your design is lighter than mine, so I might give the food can idea a try.

The stove is lit from the top using tinder that is pushed inside a little. No lighting fluid needed. Tinder can be anything like dry white birch bark (easily found hanging in strips from the trees), shaved wood (this is where a knife, even a small one, comes in handy), small, dry pine cones with lots of resin, dry pine needles, dry leaves, or, if you can find it, bits of the tinder fungus (those saddle-shaped funguses that grow on the sides of old trees). The pencil thin lengths of kindling that you use to keep the fire going are so small that lighting them is no problem. For further information on lighting wood fires without modern methods see Bushcraft UK. Ray Jardin’s book, “Beyond Backpacking” also has some information on lighting cook fires.

While I don’t know exactly how much space is needed between the outer and inner cans, I do have a few concerns. Since there is no way to easily remove the inner can from the outer, you might have some trouble with cleaning out the accumulated ash from the bottom of the can. In the BushBuddy design a separating bottom with the side vents punched in is used beneath the stove proper. Also, I’ve tried the hole-punched grating and the ashes tend to clog these up fairly quickly. If you can find mesh grating somewhere it would improve the airflow significantly. And last, I’m wondering if maybe the inner can sits a little too far down toward the bottom of the outer can. Is there enough air flow here? Remember ashes will fill this space.

I’m looking forward to seeing the stove in use. Please post pictures!

Miguel and Ryan: Really neat stoves! I’ve read about these types of stoves before but never thought to make one. I may give it a try. I really can’t wait to see what Bill Fornshell comes up with!

I’ve got a Kelly Kettle myself and like it except for the bulk. The weight is actually not too bad when you consider it replaces a stove, pot, fuel container, fuel, etc.

Dale Coryell of Wilderness Access posted on the user reviews that he uses fire starter sticks. I never though to use these before. I went down to Safeway and bought some Diamond brand fire starting sticks:

Each stick (you can actually light it as a match) is flattish and about 6 inches long. One stick weighs 0.8 oz and can be devided into 12 pieces to get a pretty good chunk for starting a fire. I did a couple of tests with these small squares and was quite impressed. Each small square will stay lit easily for 5 minutes. What really impressed me though was how easy they lit. When you break a chunk off it leaves a fuzzy edge. I was easily able to light the chunk by directing some sparks to the fuzzy edge with a light my fire starter. The package says this stuff is just compressed sawdust and wax so it has no noxious fumes too.

I actually like this stuff more than the tinder quick tabs sold on this site. They light just as easy but stay lit longer. I’m adding this stuff to my fire starting kit.

Miguel,

Do you think drilling some small holes on the inner cans side at the very bottom would help? The two can bottoms are about 1/3 inch from each other that may not be enough, some holes on the side bottom may help

hope I explained that OK?

Daniel,

when I test it I will use some starter sticks I have similar to those, you posted.

Hmmm, Ryan, I dunno. I’ve never tried it. It might work. I guess all you need to keep in mind is that you want as much air flow as possible there at the bottom. Why don’t you give it a go and see what happens? Since it’s only the inner can that needs working on, it shouldn’t be too much trouble fashioning a new inner can to fit into the outer one if something should go wrong.

You might also want to try one of those steel sink drain grates.

I lit up the stove this afternoon, but right after lighting it, I found my camera was out of charge, so no pictures, sory.

I tested it anyway.
I was very happy with the performance the gassifacation was a sucess.
Before teting I cut larger holes in the bottom of the can, actually I cut between holes with a pocket knife so instead of a bunch of small holes they are combined to make fewer, larger holes.(I will post a picture)THey were not clogged by ash.
anyway, I lit the stove using a colgahans fire stick and grabbed a bunch of dry wood, broke it in to small peices, threw them in the stove, light the stick and in a few minuets I had a nice fire going, I was afraid that there would not be enough room for the wood gas to come up the sides but it worked and the flame was not coming from the wood it was coming out of the holes in the top of the inner wall like Miguel described they should. I was very impressed, The flame burned hot, burned the full can down to coals, and lasted for mabey 10-12 minuets without refueling. And the flame at the hihgest was about a foot tall.

This is a great stove, I will make a potstand for it and use it for boy scout campouts, and hikes where low weight is not important because we are not moving fast, or at all.
And I dont want to spend $$$ on alc. or esbit for just an overnight campout.
again, a great stove other styles of wood stoves dont compare, sorry again for no pictures

Hey, Ryan, I’m confused — is this stove running on wood or beans? — I don’t get the “gas” thing.

Seriously, nice job using recycled cans. For an overnighter, I wonder if some sort of charcoal stove would work. A few briquettes would put out some heat and be light and cheap.

Hi Dale, take a look at the link to the woodgas stove concept above. It explains in detail how it works. It’s not just the wood itself burning, as in regular wood stoves (note those are not “woodgas stoves). It’s much hotter, cleaner, and more efficient. It’s why Ryan J. took the Bushbuddy to Alaska. The concept is not really intuitive at first. But when you use the stove, as Ryan F. did, you will see the gas burning as jets from the top holes in the stove.

I’m not sure if others understand that you don’t need an extra windscreen for this stove, though a layer around the opening under the pot would help with conserving heat. The outer can acts like a windscreen. Because you don’t need a windscreen, or carried fuel or fuel container, the stove is lighter than alcohol, gas, or cannister stoves with their extra containers and fuel requiements. Ryan J. expains about this on his Arctic 1000 site. If you learn bushcraft and how to obtain dry fuel even in the rain, this kind of stove could be an ultralight walker’s dream. I’d just like to get the materials even lighter, and learn more about how to get the woodgas to burn blue… the epitome of the stove design’s efficiency.

These kinds of stoves burn all kinds of fuel. I just don’t know enough about the chemistry and physics behind it to be able to say if things like charcoal would produce wood gas. Anyone else have any idea?

Check the stoves “Discussion List” at http://www.repp.org for _extensive_ discussions of TLUD (Top-Lit UpDraft) technology, including the elusive blue flame. Note especially the contributions of Tom Reed (also offering a battery powered woodgas campstove at http://www.woodgas.com), Paul Anderson and Alexis Belonio. ALW

I was kidding— “gas,” “beans”…. geez guys.

It’s a great idea. I like the fact that it doesn’t use a fan or batteries– less “gizmo” factor. What about using these stoves where there is a burn ban in effect? I could see a ranger having fits.

The charcoal idea was more of a tangent concept rather than using it directly in the wood gas stoves. Titanium hibachi anyone?

Ryan,

I was wondering if you tested the cooking speed of your stove?

ie … How long did it take to boil a pint of water on it?

Also notable are the contributions of Ray Garlington: http://www.garlington.biz/Ray/WoodGasStove/

and Mark Jurey:
http://www.csun.edu/~mjurey/pennywood.html

I have made both of these stoves (in 5-15 minutes), and they do a remarkably efficient job of burning wood without smoke, without the double wall. I’m not sure the double wall is worth the effort for most occasions.

ALW

Wow– those are so simple! Is it possible to make one of these where the pot can sit down in the stove a bit and use cross-wise stakes to support the pot?

Rig it up however you like. They’re surely not as efficient or hot burning as your ingenious double-walled version. The most important aspect of them is the “top-down” burning. If it weren’t for this, they are little more than modified hobo stoves, which work by limiting convective heat loss. Having spent many weeks trying to perfect their use under wet conditions, I can say that they do a little better than a simple cooking fire. But any wood stove is no substitute for basic wood craft.

The true champions of efficient wood burning for cooking are the fan-powered cook stoves by Belonio and Reed. Without a fan, there will never be blue-flame, carbon-monoxide free efficiency. See the recent posts by Anderson and Reed on the http://www.repp.org “Stoves” “discussion list.” But these folks are working with impoverished rural populations where fuel shortage is a problem, and smoke is intolerable (as they will be used inside the home like our ranges). Such efficiencies are not needed in the backcountry where smoke is easily dissipated and fuel relatively abundant.

A more ambitious goal might be to develop a wood-burning stove that is acceptable to forestry officials for use in burn-ban areas. As it is, a properly contained wood fire is as safe as an alcohol, esbit, or gas stove (all will wreak havoc if fuel is spilled or kicked) and does burn only a handful of twigs to boil a few cups of water. Is anybody up to addressing this regulatory issue? ALW

Nicely done. I had (at one point) tried to make a similar integrated unit stove, but ran into problems as (I believe) mine had a much smaller annulus space than yours did.

Not having enough time to refine my idea, I’m glad to see someone else did.

I suspect that your design could be refined so that a group of boyscouts could make a similar design without the need of power tools (using a church-key can opener, a hold punch, a side-cut can opener maybe a couple other things… some tins snips…) I may need to find some similar-sized cans and try it out.

Miguel, I was just relooking at your pics. Am i wrong, or is the bottom of your ‘firecan’ (the inner can) solid? did you not put mesh in the bottom? does the ash simply collect in the bottom and you dump it out at the end of the burn?

Hi Joshua, you picked up that little unfinished business in that picture. :P When I took the first indoor photos I hadn’t yet found a grating for inside the inner can. Since then I found a lightweight steel drain cover. It’s being used in the lit stove picture.

This weekend I will be getting out to the mountains and trying the stove out. I’ll bring a backup cartridge stove just in case. SInce it is the middle of the rainy season here, my woodcraft skills will be nicely tested… hope I can find the dry fuel I will need for the stove!