[pct-l] Pop can stove

[elee@microsoft.com (Eric Lee (RAT))]

Steve wrote:
>
I'm interested if anyone else is trying stoves from the smaller cans. Hey,
it saves a fraction of an ounce! Monte will appreciate that, he could
carry 75 of them for one of his canoe winter stoves!
>

I'm not exactly sure what the Henderson and Photon designs are that you
referred to, but I'm guessing that the Henderson is the double-wall, open
center design and the Photon is the single-wall, sealed chamber design.

I've built several models of both of them.  My favorite one so far is a
single-wall, sealed chamber stove built out of 5.5 oz juice cans.  I based
it on designs found on the net and added my own twists.  Priming it is a bit
of a pain but it seems to be the most efficient (though not necessarily the
fastest) stove.  Because this stove is so small, I can angle the jet holes
up and outward at a 45 degree angle and still have the flame contained
underneath my pot.  I'll refer to this one as #1.

My second favorite one is a double-wall, open center stove built out of 12
oz pop cans.  No priming required, so it's easy to light.  It's also the
fastest-to-boil stove I've built.  But I'm pretty sure it's less
fuel-efficient than the juice-can stove above.  I'll refer to this one as
#2.

I'm no expert, but from what I've read and seen, a stove that runs too rich
(too much fuel, not enough air in the combustion zone) will end up wasting
fuel.  The problem with the #2 stove is that it releases far too much
vaporized fuel at one time, and some of it escapes without being completely
burned.  When I test it, I can smell thick alcohol fumes rising up above the
pot/windscreen.

The #1 stove doesn't have this problem.  Because the stove is sealed, the
only way the vaporized fuel escapes is through the burner jets so it's
more-or-less completely burned.  Furthermore, having each jet point outward
gives each one some separation from its neighbors and allows more air to be
mixed with the fuel.  It boils water a bit more slowly than #2, but I
believe this is simply because it's a smaller stove with less total flame
area.  I tried building this same design out of pop cans, but the flame area
ended up being bigger than my pot.

On the other hand, priming the #1 can be kind of a pain.  It actually
doesn't require a whole lot of fuel - several drops will do it, if the fuel
is in the right place.  It takes a lot of practice though.  Too much priming
fuel will definitely cause flare-ups like you saw, which kind of defeats the
fuel-efficiency advantage!  When it's done right, priming is easy and quick,
but when it gets screwed up, it's a pain.  I haven't used the #1 this stove
on a long trip so I can't say if the hassle of priming outweighs the fuel
savings.

I've never been concerned with the safety of the #1 stove.  I can't give you
specific engineering figures, but I'm pretty sure that, given a decent
number of burner holes, there's no way you could build up enough internal
pressure to explode the stove.  But I'm no expert.

I can give more specific details on my stoves if anyone's interested.

Eric