Building the
Jet Stove!
Introduction:
I lied. You shouldn't build one of these because if you're
an idiot you'll burn down your house, apartment, cat, etc.
So standard disclaimer: Fire is dangerous. Have your parent's
help you, never run with sissors, and don't touch yourself
inappropriately. I think that covers it.
A jet stove is called that because of the fan, the jet,
of flame and the sound when it is running full blast. It
is also called and elbow stove or an L stove for the simple
reason that it is shaped like the letter “L.”
I built one in about 30 minutes. I will make a few enhancements
to it that will add about ½ hour soon, but they are
not necessary..
What
is it – the essence- of the stove?
It is two cans, say a 2 lb coffee can and a tall apple juice
can, one inside the other. The space between them is filled
with something that will insulate and not burn, and the
easiest material to have on hand is wood ashes. Finally
a small can, like soup can comes from the outside, down
low, about an inch above the bottom of the cans and goes
through both cans, sticking in about an inch and sticking
out about 2 inches. Just follow my pictures and you can
build one too. It is simple.
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It
is three pictures simple. Three cans. In my case I used
a coffee can for the cowling, a V8 big juice can for
the burner can, and a soup can for the air feed or horizontal
can.
First on the coffee can I held up the soup can to the
it's side about an inch from the bottom, and stabbed
it repeatedly with my swiss army knife. This was the
hardest part because the coffee can steel was thicker
than the other two cans. So I cheated and cleaned the
whole with tin snips (so shoot me).
Next I cut the hole in the burn can (the V8 can). Notice
that I only cut the hole about 1/2 inch from the bottom.
That is so I could get some insulation (wood ashes)
under the burn can, thus it would not rest directly
on the metal of the cowling can (coffee can).
Last I cut the bottom out of the soup can by stabbing,
and rolled the resulting edge down with a smooth rock
and choice words.
Last I put some wood ashes in the bottom, put the burner
can in and pushed the soup can through both of them.
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Left:
That is it assembled. I put more wood ashes in almost
to the top, stopping only because that is the amount
of as I had. It would work without the wood ash, but
the burn temperature is higher and more complete, and
thus more efficient if you can insulate the inside can.
You could use fiberglass insulation but I think the
simplest thing is camp fire ash. You could even use
coarse sand but it would slow your initial burn.
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OK
now lets see how the stove works!
You put several parallel sticks in through the horizontal
can, the soup can, and stick them all the way in. They can
be quite long as they will simply stick out the open end
of the soup can. When you look down at them from the open
top the form a platform. You put a hunk of paper and a few
twigs on top, or tinder (dryer lint with a dab of petroleum
jelly works great) and light it with a match or your flint
fire starter. It lights easily and smokes lightly for about
15 to 30 seconds.
I loaded the sticks through the soup
can until they touched on the opposite side. It's nice
to have some bigger twigs or little branches for this,
as you can see that it makes a little platform. On top
of this platform I dropped a bit of bit of paper and
some twigs. With the jet it is not fussy, you can throw
in what you want, but as soon as it starts, all your
wood goes in through the soup can. |
Here is a good example of the jet when the stove is
going. Air sweeps in through the soup can and enters
the very hot burner can (remember it is insulated and
all the heat is being focused on the fuel in the burner
can), ignites and bends upward and out the burner can.
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Here
is a nice shot of the jet, from which the stove gets
it's name. It sounds happy when it's lit. To continue
the cooking just keep pushing the long sticks in.
You can add more. Unlike the MIDGE stove this is not
a batch stove. You can feed it for as long as you
need to cook your meal.
RIGHT: I cooked a can of beef stew (as I'm going to
use the can on an enhancement to this stove), by resting
it on the burner can (which sticks up about 1/2 inch
taller than the coffee can cowling), but leaving it
off center as not to slow down the burning.
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I
will make a taller chimney that clips to the inner burner
can. It will have spaces around it so you can just set
the pot on it. See enhancements
below. |
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Because it
is insulated with the wood ashes from my campfire of
last week, even after cooking for 10 minutes I can lay
my hand right on the coffee can, and carry it if necessary.
By 1/2 hour it was hot, but not hot enough to burn at
the soup can horizontal can. The bottom and lower sides
remain cool, the top is hot to the touch. |
How
it works continued:
Then it takes off, sucking air through the soup can into
the burn chamber. The wood ash insulation keeps the heat
right there on the sticks and they burn quick and hot. You
feed it by pushing the sticks in as they burn and it keeps
roaring.
Like all high efficiency stoves that burn wood waste, cardboard,
rolled newspaper, twigs and branches, the jet stove has
you put your cooking pan or pot right on top of the exhaust
flu. It is where all the heat is and that is where the efficiency
comes from. Also you radiate almost no heat sideways or
down because of the insulation so all the heat goes up to
the pot. This of course means it's useless for heating (as
it is but I have many ideas), as there is no chimney to
get rid of the C02 and any unburned fuel, and because it
is designed to NOT RADIATE but to contain the heat and direct
it to the cooking pot.
Planned
enhancements:
The modifications
to a simple jet stove are these, and I'll be doing them
and adding the pictures to this page:
1.Create a “crown” on top of the inner burn
can to hold the pot. This will also extend the burn can
into a chimney.
which allows more time for the flame to burn, and also to
increases the speed of the hot rising gases, which increases
how much the jet sucks – it makes the stove hotter
and more efficient yet
3.Create a larger pot shield that wraps right around the
water boil pot to force the flame into even closer contact
with the pot allowing more time for the heat to transfer
to the water. This is specific for boiling water in a specific
pot. I'll make that out of another coffee can.
Notes about elbow stoves in general:
The jet
stove is a full burn stove. It has one heat - hot! You don't
reduce heat – it goes as fast a you push the fuel
in. You can be slower about feeding fuel but it is not really
the design. The whole concept is to burn a small amount
of fuel very hot and fast and then capture as much of that
energy as possible in the pot you are cooking in.
In
use, this is what I have found. If you want to fry food,
like eggs, you can simply lift the pan once you reach the
cooking temperature and hold the pan up. Works but requires
you to hold the pan. Unlike a campfire where you would be
burning yourself from the fire at that point, with the jet
stove you have a four or five inch column of HOT flame and
gas, but it is localized so it is easy to hold the pan over
it and not burn yourself.
Size:
I found the coffee can sized burner perfect for a small
simple meal of hot water for coffee and heating canned food.
I think this would be good for boiling up to 1/2 gallon
or so at once. Any more weight and I'm not sure you could
keep the stove balanced.
In Africa they make the outer can out of the square metal
kerosene cans, standing about 14” high and use a ceramic
flue liner for the middle – something they get from
wells I think. Both of those would not be readily available
here and I don't like the larger size, it won't fit in a
small pack. My focus is on cooking on the go without spending
one dime on fuel.
What
does make sense to me is to make two of them and cook simultaneously
if you made one slightly smaller when you were moving, traveling,
you could empty the wood ashes into a sealed garbage bag
and pull the horizontal cans out and fit all of them together.
I may pursue that. If you kept the plastic lid of the largest
coffee can you could trap all the cans together, sort of
like one of those Russian dolls, one inside the other. This
would give you the equivalent of a two burner stove.
I'll
add more when I do the enhancements. To learn more about
Appropriate Stoves check out this link!
