The simplest ideas are usually the best eh?
I have been experimenting with various designs of improvised camping stove for some time now. They have varied from a simple open cup of burning fuel to highly intricate vapour pressure devices that take hours to build.
This is my latest favourite, it is a combination of two established types of stove. A chimney stove and a low pressure side-burner. It takes about three minutes to make and so can be constructed as and when you want to use it.
This design also has the advantage that it will run on pretty much any flammable liquid you put in it. I have used methylated spirits, rubbing alcohol, xylene, white spirit and petrol.
This brings up an important safety issue though, anything other than an alcohol type fuel is inherantly a lot more dangerous. Pure hydrocarbon fuels like xylene and petrol are toxic, dirty (they make a real mess of your pan!), smelly, potentially explosive and can't be put out using water. An alcohol fire can be extinguished by upending your pot of water over it if things get out of control (don't believe me? Try it.)
For more info on improvised stoves have a look at the site that inspired me to try experimenting: zenstoves
Step 1: Build Your Stove
Ok. To do this you will need:
1) Empty 330ml soft drinks can (size not that important)
2) Can opener.
3) Pointy thing (bradawl, nail, tentpeg, sharpened stick)
So essentially an empty drinks can and a swiss army knife.
First remove the top of the can using your can opener, be careful not to damage the rim too much.
It would appear that the rim is an important part of this design. Without it, the aluminium of the can might start to melt and crumple from the heat. Some can openers slice the entire top off, these are not suitable (see picture below for what the completed stove should look like).
Now punch eight, equally spaced holes through the side of the can about 1" up from the base. The holes should be roughly the diameter as the awl tool on a swiss army knife or a round steel tent-peg. (again, size isn't all that critical, spacing is more important)
Punch another ring of eight holes round the angled part of the can just below the top rim.
Punch a third ring of eight holes through the side of the can just below the angled part, arrange them so they fall inbetween the upper row of holes.
Your stove is now complete!
Step 2: Setting Up and Lighting
Right, this stove is also your pot-stand. So, you need it to be steady enough to support the weight of your full pot without falling over. A level surface might suffice or you might want to peg it upright by arranging three pegs round the outside of the can.
If you're outside, try to protect it from wind as much as possible for efficient functioning.
Now, fill with fuel to just below the bottom row of holes. I'd suggest alcohol or methylated spirits. Petrol and xylene will work but are much more dangerous both in terms of health and in terms of fire hazard.
Light the stove by holding a match or lighter to the bottom holes.
You'll notice the flame lights inside the can and 'chimneys' up the middle.
Allow the flame to build until it is a few inches above the top of the can then slowly place your cooking pot on top. The flames should transfer to the side holes and start burning like a gas ring. If they don't, remove your pot, allow the flame to get a bit higher and replace it.
You'll note that the flame is actually burning deep in the bottom of the can near the base holes then jetting up through the top holes. Looking down into the uncovered can (from a height, eyebrows!) you can appreciate the pattern of flame this arrangement of holes generates.
These stoves are remarkably efficient, almost no heat escapes through the sides, it all goes straight up. Mine will boil two mugs of water in my stainless cookpot on a single fill of methylated spirits. I was using it this weekend to great effect in temperatures below -6C
N.B. I have occasionally seen these stoves 'flashback' through the bottom holes so keep the area around it clear of flammable material!
Oh yeah, they're quite difficult to extinguish once they are going. I try to just fill it with what I'm going to use but an upended cooking pot placed over it for a while seems to do the trick too.