Emergency Stoves for an Uncertain Future - We build and test a MIDGE stove.

Why should you or I care about building a little stove out of discarded cans? One of the necessities of any dislocation - should it be a Katrina storm surge, earthquake, political upheaval or terrorist threat, is that people are often forced to move unexpectedly and without a lot of preparation. If you can make a good little stove in just a few minutes with a minimum of tools, then you can sterilize water, heat canned food, and reconstitute dry food.
If you've been reading this website or the blog for a while you have seen my solar oven. That oven is provided in many areas in Mexico for low cost, yet it's primary purpose is not to cook food but rather to sterilize water. Most Norte Americanos are insulated from the effects of bad water, but in the rest of the world, drinkable (potable) water is NOT a given. An emergency stoves first function is water sterilization, then cooking.

There are other reasons to build a good emergency stove. They use much less wood than an open fire. They do not attract unwanted attention (if you're trying to keep a low profile), as they produce much less smoke. They are portable and fast and in almost of all the USA you can find enough brush, twigs, paper scrap, or card board to run it long enough to boil water and cook food.

My criteria for an emergency stove is that it should possess these characteristic:
1. Quick to throw together with a minimum of tools.
2. Tolerances and exact sizes can't be critical as you don't know what cans you salvage.
3. It should be stealthy, making much less smoke than a fire
4. It should be more efficient than an open fire - it should use less wood or other bio-mass.
5. It should be easy to pack up and take with you. Perhaps it stores any pieces in itself, or better yet, has no pieces to loose.
6. It should be light.
7. It should be able to boil water quickly and cook a meal with a couple of fists of twigs.

How did the MIDGE that ED and I built stack up?
There are three pieces to the MIDGE stove. The outside can which we call the cowling. The inside can where the fire goes which we call the burner. On top of the burner goes a little can, (tuna for instance) that makes the air path. I call that the cap.

We used every tool on the table (right hand edge) and more. We worked about an hour an 1/2, Ed and I doing different tasks. I cut myself twice, Ed once. Mine were little. Ed dripped. So far I'm unhappy with the chicken shit design and instructions in the web article. But we persist.	Ed began by making the sieve holes in the burner can.
Here is the first step on the burner completed. Next, RIGHT we make the actual holes on the burner can that the wood gas will come out of when the downdraft takes over.
We drilled out the burner holes in the burner can to the suggested (required???) 1/4 inch. The instructions also said to make holes around the bottom next to the sieve to let in even more air. We did not do this at this time.	We turned out attention to the cowling, the big outside can. We made the can opener holes around the bottom and made the holes for the 4 screws.
Here are the four screens in place. I hate the screws, it is a stupid weak design and I replaced them later with pieces of my fence wire crossing each other which was much stronger. Did the MIDGE designer even run his stove more than once?	I begin work on the cap by putting the burner can on top of the tuna can and scribing around it. The tuna can will be a cap on the open end of the burner can leaving an airspace between the burner can and the tuna can. They should not be tight but should have 1/4" (guessing) of space at least. This is how the wood gas gets up to the holes to come out after it has switched itself to downdraft.
Cutting the tuna can along the scribe line	Ruined tuna can. The hunting knife slipped and cut too close to the edge. That would mean the can would not rest closely on the open end of the burner can which would mean the wood gas wouldn't go through the holes in the burner can. So we find a bamboo shoot can that I had from last year when I was going to cook a stir fry. It was just a little bigger and a little longer and seemed possibly a better choice.
Here is the tinder I used to start the stove.That is dryer lint (that I've been carrying in a plastic bag and little petroleum jelly. Just a dab 'll do ya! It makes great tinder. If you have emergency boxes you can make it up before hand and just put 20 or so in a sealable freezer bag. It starts and burns hot and long.	Here is our first test. We packed the twigs in vertically so that none were sticking out of the top. Per the instructions the tinder (dryer lint) was about 1/3 of the way down the twigs. it wasn't hard to light the tinder with my stove lighter but I wonder how hard it would be with a match. Without tinder this wouldn't work.
OK, after the smoky phase it started burning up out of the burn can, they puffed once and sucked down through the wood and we had flame both out the top of the can and through the downdraft out the burner holes. Hard to photograph when it is light but the little flames are coming out the 16 burner holes we made at the open end of the burner can (opposite the sieve).	There we tried a second burn and put in the extra air holes in the burner that we had not originally done. We could not keep it lit. Also the four screws in from the side where wobbly and it was very hard to keep the can centered. The screws, as we thought, are STUPID. I took some wire (the wire I am using for my DC welder) and made two straight pieces that go completely through the can and form a firm base. You can see them in the above picture. Also I covered the extra air holes in the burner with aluminum tape for this test to see if we could get back to the success of the first test. You'll also notice that I did not bury the tinder this time and I filled more wood into the burner. This is a batch process and you have to use all of it before you can reload.
It is nearly dark now, as I hoped I could get a better picture for you this way. I have just lit the 3rd test and there is no smoke but the flame is burning UP (not downdraft yet). It is consuming the wood quickly.	Three minutes later is puffed and shifted to down draft and the flames from burning wood gas (CO) started coming out from the burner holes as it should.

REVIEW of the MIDGE stove we built:
The instructions in the adobe pdf file for this MIDGE are badly written, confusing, sometimes precise but mostly the document doesn't address any of the important spacing, clearances, construction or use necessary to make this work.
The physical support of the burner on the four screws is ludicrous, totally stupid. Nothing centers the burner can in the middle of the screws (or later wire cross that I used). You have to center it by hand. There is similarly nothing that holds the cap can centered on the burner can. Given all that, we built it and it works.

First a quick understand of how burning wood releases heat for you: You have wood with is a complex carbon based fuel. You heat it in the presence of oxygen and it starts to release gases and tars and water. The gases burn as they mix with oxygen (which is why you see flame). The flame of a fire is unburned carbon and carbon monoxide changing to carbon dioxide. The twig as part of a tree or bush stored the carbon from the air when it was alive through photosynthesis. No you are releasing it back to the atmosphere. The plant used solar power to store the carbon and that is the heat that you get back, the heat that boils your water or warms your food, it is delayed solar energy.

Now that we've nailed fire we have to wonder why we started with such a complex emergency stove. The simplest fire you would make, and is made untold number of times every day all over the world is a 3 stone fire.
Just as it sounds, it is three rocks about the same height so your pot can sit on top. Twigs and sticks crossed underneath and lit on fire. Air rushes in between the three rocks and if you need to cook a little longer you can add a couple of sticks. It wastes MOST of the heat produced because there is nothing that directs the flame to the pot and because the burning wood is exposed to moving air and is open to everything, most of the radiated heat simply escapes to warm surrounding materials (you for instance) and less goes to the food., So it is somewhat obvious that if we can put the fire in something perhaps we can point the heat released to where we want it to go.

Enter wood stoves. Too big a topic for this discussion, but focusing on small emergency stoves that burn wood scraps or dung we can see what we have to control and how we utilize the wood better.

There is a stove called and L stove or a Jet stove or an elbow stove that is used in refugee camps throughout the world, especially in Africa. It was introduced because the landscape is nearly denuded, especially around the camps to provide cooking fuel for the concentrated mass of people living (hanging on) there. I will be building and jet stove and link to that stove later.

Because Ed and I were excited by the concept and efficiency of an emergency wood stove that burns the wood AND the released gas, we built the MIDGE first.
The MIDGE works oddly. It is a combination normal wood fire in a can and a downdraft stove that makes wood gas and burns it. As a fire in a can - when you light it (see the pictures of my third attempt above) it burns UP, the flame going up and the twigs burn and the fire - sits on top. Then something odd, interesting, cute and funny happens.
AS A DOWNDRAFT: The air that is between the burner can and the cap heats up and rises out the 16 holes in the top of the burner. This creates a suction beneath the bottom of the burner can and three separate things begin to happen.
1. Air is drawn down between the cowling (big can) and the outside of the cap (bok shoy can) and is brought to the bottom of the can.
2. Air from within the burner can is sucked down through the burning twigs and begins to cook the wood below it giving off water, carbon monoxide, tars, and other sticky stuff- which looks exactly like smoke - which it is - which exits the bottom of the burn can and mixes with the air being sucked down in number one.
3. There are four holes in the bottom of the cowling and outside air is sucked directly into the bottom of the cowling can below the burner can (the burner can does not reach the bottom of the cowling but instead sits on the crossed wires or screws).
4. The three streams - 1 warm air, one cool air, and the smoke mix and are sucked up and out between the burn can and the cap can (tuna can). The heat from the fire makes this pathway the most "pull-y" as the air is the hottest. IT sucks all three streams up and if there is enough smoke and oxygen in the mixed three streams then we have FIRE out the holes around the top of the burn can.

OK so in down draft mode the fire is burning DOWN not up through the twigs and flame should shoot out the burn can holes at the top producing a very nice blue and sometimes yellow flame. That will open happen if we can test and test and test various can and hole size combinations. Even then the density and dryness of the full will vary and without adjustable control on all three streams I just don't think this is a practical stove.

The short story Review!
. The stove fails my criteria in these ways.
1. It has too many pieces and those pieces are not well attached. True we could build a better version, but I think the reason we didn't find more plans for these on the internet is that this design is to "fragile" in operation to depend on.
2. It requires many tools to build it. I cannot see me doing this under stress.
3. It is a design that is iffy as to whether it will work, so why use it. It takes part of the wood (in my third attempt . 1/2 of the wood) to get it to shift to the downdraft mode.
4. In the small size that we built there was not enough heat to boil water in a small sauce pan before we ran out of wood.
5. It has no advantage over the jet stove which has the same number of pieces but is completely tolerant of any three cans you find that will even roughly fit the design. Also the jet stove can be continually fed new fuel until your cooking is done. Look for that tomorrow. Meanwhile, just say NO to MIDGE, yes to jet stoves.