03 June 2013

MYOG: cat can stove

My Whisperlite seems to be coming to a pressure just high enough to use, but no more.  I keep having to pump it while cooking or it will go out, but it'll still have pressure in the morning.  Actually, considering how little the volume changes during use, there's probably something else wrong.  I need a new pump, probably.  Instead of getting a new pump, I decided to go for something that actually is extremely light, but still runs on a liquid fuel.  And it can be made for under $10, a bit more if a few things aren't already had.  I tossed together an alcohol stove from cat food cans, bike spokes, and a lasagna pan.

The stove itself is described here, although there are quite a few other places, and I took clues from there.  I had to get a small cat food can, because my cat doesn't get overpriced food in tiny cans.  I punched a single row of holes out with a hole punch rather than the church key on this one.  The larger can has holes punched around in a double row and a smaller chimney hole based on some page somewhere.  Two wide strips of lasagna pan held together by paperclips at the top and bottom and also punched with holes just goes around the pot with a little spare space for exhaust.  A bit more lasagna pan is folded over to be a simmer ring.  The bike spokes are bent to make a pot stand described here with the joints actually a bit more lasagna pan in strips, wrapped around the spokes a few times and glued down.  A bit of found ancient fiberglass house insulation makes the wick inside the small can.

It ain't pretty, but it doesn't seem to matter.  I went for glue to keep the cans together, but it couldn't take the heat so they are loose.  Tabs from using a church key on one of them would be handy for centering them, but this doesn't seem to be critical.  The first day I left it out, a raven went after it for the lingering smell of cat food, so now it gets a pot over it or stuck in something.

Fuel sources are described here.  I started out with isopropyl alcohol because I had a 91% bottle of it under the sink for cleaning wounds.  It lets off a somewhat sweet and likely poisonous smell as it burns, but deposits a nice layer of soot onto the bottom of the pot so the IR doesn't reflect off the shiny titanium.  Now that that has run too low, I poured in some Everclear instead.  This burns nicely but turns out to not be sold in 95% any more.  The bottle has had the 95% blocked out and is actually claims something more like 75%.  This burns much more nicely.

Getting the right amount of fuel seems to be quite a game.  I have poured in a bit more to start it up again and I have watched it burn for minutes after I was finished cooking.  Up on Sawmill with half the water actually ice, it didn't take quite so much extra isopropanol as expected with the extra height and cold.  In the Sierra Nevada, just 1000 feet higher, the ethanol somehow seemed too effective in the morning and not enough in the evening.

The simmer ring is a bit hit or miss, mostly miss.  It is placed to cover the holes in the bottom of the chimney piece so that much less air passes through.  Basically, starve the alcohol of oxygen and it will burn more slowly, allowing simmering.  Placing it on the chimney above the holes while getting the water up to heat makes moving it difficult because, of course, it gets hot.  Leaving it off and then going to loop it over doesn't work so well either, because there's still a bit of a roaring flame.  I have managed to poke it down with a stick for use.  Half the time I have used it, there was still plenty of air getting in and no simmering was possible.  The other stoves show an extra piece under the stove that I do not have because they don't say what it's for, maybe this helps with controlling the air supply.  Still, it has worked sometimes and is quite handy when it does.  As the stove simmers, the flame seems to breath giving bursts of heat, so it still isn't perfect, but better than constant stirring on a stove that wouldn't think of simmering.

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