It is a two-wall design, which preheats air in between the walls to ignite the smoke. Well-tended, this produces a bright, smokeless flame which produces little soot and leaves little to no scorching on the ground below.
It is built from commonly available (in the United States) parts: a quart paint can, a smaller tin can, and a shorter tin can. The only specialized tools are a safety-style can opener and an Irwin Unibit #1, though similar designs can be made with just a church-key and ordinary can opener and alternate tools are discussed in appropriate steps.
The whole thing can be built in about an hour. This model weighs 6.6 oz (187 grams) after several firings, and nests in, e.g., the Snow Peak 900 Ti or Al pot.
Ready? You'll need:
Step 1: Materials
A 19 ounce Progresso soup can. Other cans such as 20 ounce cans of fruit will work as well, but the
Progresso cans are a bit shorter, which we want.
A Large, short can. Mine had bamboo shoots in it; many cat foods and canned meats come in this sort of can. The diameter should be a little larger than the inner ring on top of the quart can. Don't get an aluminum one, it'll melt and buckle in the heat.
Step 2: Tools
Irwin Unibit #1 Though one can use several bits to make successively larger holes, this tool will make you life easy and your holes better.
Safety Can Opener This is the kind that takes the top entire off the can, rather than cutting a hole in the top. One could use the other kind but this will leave a jagged hole and isn't recommended.
Sharpie, Electrical Tape and Scissors for marking where the holes go. The ruler turned out useless, however a:
Fabric Tape Measure proved very useful indeed.
Step 3: Drill the Bottom Sides of the Inner Can
What I did here was drill two rows of 1/4" holes in the bottom side walls of the can. This does not provide enough draft. A design known to work, this stove's closest relative in fact, has holes in the bottom, rather than the bottom sides, so one could drill out a bunch of quarter-inch holes into the bottom.
I intend to drill out another can in the near future, with three rows of 3/8" holes up the inner walls, and perhaps more holes as well. I'll update this instructable accordingly, and welcome comments on people's luck with this step.
Step 4: Measure Top Holes of Inner Can
The quarter-inch fabric measure is about a quarter-inch from the top corrugation of the can; this gives a good result.
Step 5: Drill the Top Holes
Step 6: Measure Holes in Outer Wall
5/8" up from the rim turns out to be the sweet spot for the holes. An eighth inch either way won't kill ya.
Step 7: Drill Holes in Outer Can
Step 8: Remove Bottom of Outer Can
Step 9: Press Fit Cans Together
Step 10: Drill Out Potstand/windscreen
Leave room to cut a feed slot out.
Step 11: Cut and Crimp Feet Slot
Remove the bottom of the can with your safety opener, and discard.
Slice through the top, leaving a ring that can be stored between the walls or nested into the top ring of the can.
Step 12: You're Done!
Step 13: Use It!
Fill the can with sticks, laid parallel to the ground in alternating rows like a grid. Bring the wood to near the top burner holes, but do not cover them.
Place the cooker on something that won't ignite, and shelter it from the wind. You could carry a windscreen but unless you're traveling in particularly harsh terrain it's worth it just to find a quieter place to cook your meal.
Build and start a small fire on top of this fuel. Fire-lighting is an arcane art with many approaches, all of which call for some practice and skill. A general approach that works well is a tinder ball with a small tipi of sticks around it; the idea is to get the sticks burning and start to char the layer below, as well as to make glowing coals that drop down to ignite the lower wood.
Place the windscreen/potstand in the groove of the can; this can be used to build a lean-to style top fire as well. Experiment before it makes the difference between dinner hot and dinner cold!
If properly built and loaded, the stove will ignite the smoke from the fire readily, within a minute of ignition. When the smoke is burning cleanly and brightly, it's time to put a pot on the stand. I keep steel chopsticks on hand to stir the fire if needed, but a light hand is best here and the fire if well built will burn without interference.
When the existing wood has all become coal, one can keep the fire going by feeding sticks in one at a time. They quickly ignite and the smoke feeds the fire for awhile; the stove in this mode must be frequently but lightly fed, finding a balance between too much smoke to burn it all and not enough to keep the secondary burn going.
I keep the lid around, as a trivet for the pot, and to cover the fire when i'm done with it. This will cause the remaining charcoal to smother out slowly; leaving the lid off will led it burn down into clean ash. The can could be used for charcoal making by firing it until the volatiles are mostly gone, covering the bottom holes with dirt, and putting the lid on.
As I implied earlier, the stove as shown here doesn't work as well as it might. I chalk this up to the small holes at the bottom of the inner can; larger holes, and more of them, will feed the fire properly and keep everything nicely aglow.
Step 14: Credits
This design closely models http://tjamrog.wordpress.com/2008/12/22/the-evolving-backpacking-wood-stove/, by Tim Jamrog. His design has holes in the bottom of the inner can, rather than the bottom sides, and this is known to work well. I'm working on a design with a solid bottom, for various reasons including catching the ash and embers. As I've indicated, it works, but it could work better, and I think larger holes on the sides of the inner can will help. For just under six bucks in materials, experimentation is easy.
For those wanting the lightest weight and blingiest gear, the Bushcooker LT from http://www.fourdog.com/index_files/bushcooker.htm can't be beat. Titanium won't rust out, ever, and the LT II, which is closest in size to this model, weighs a wispy 3.5 oz.
Making stoves is easy, fun and satisfying. Experiment to your heart's content, and let me know what you come up with.