stove making for caldera clone

dimeotane
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stove making for caldera clone

Post by dimeotane » Wed Jul 27, 2011 12:26 pm

I'd love some stove making advice. I've made a little caldera clone for my 500ml sierra cup. I've been trying to make a stove for it that can boil two cups on 15ml meths. The cone is *supposed* to be very efficient, but I'm not getting much luck.

The problem is that most stoves I've made that work well outside the cone burn too hot inside the cone. They boil off the meth and flare out the holes of the cone. The 15ml meth is burned up in 4 minutes! I've made out of pepsi cans a 'kitty stove' similar to the one that comes with the cone.
I tried a 'super cat' (with a gap below the pot).

I tried using a small steel can and it burned much slower, 10 minutes... but still didn't bring the water to a boil.

Any suggestions?
Last edited by dimeotane on Fri Aug 05, 2011 12:10 am, edited 1 time in total.

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shingaling
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Re: stove making for caldera clone

Post by shingaling » Wed Jul 27, 2011 1:57 pm

I'd try a Starlyte style burner like Zelph makes.

If 15 ml doesn't do it, then increase the amount of fuel used by about 2.5 ml and try again until you find out how much fuel it takes to get a boil. 15ml and 2 cups is a good starting point, but often I find that going strictly by 15/2, I can't always get a boil with the stoves I make. Experimenting is a lot of fun though, so I don't mind doing several burns with different amounts of fuel, different shapes of pot, different heights between stove and pot, etc. It doesn't always turn out like the clips on youtube or according to the manufacturer's claims.

I made a small tuna-can style stove recently, and I was amazed how much difference is made by adding or subtracting 1/4" from the pot to stove distance. It's also important to match the stove (the flame pattern) with the pot. I have a lot of good stoves that only work with a particular style/size of pot. Once I fine tune things so that I can get a good boil every time, I put the stove and pot aside as a unit (along with windscreen, carrying case, matching spork, etc.). Then I reach into my pile of pots and grab one, and reach into my pile of stoves and grab one, and the matching process starts all over again. :DB:
Any road followed precisely to its end leads precisely nowhere. Climb the mountain just a little bit to test that it's a mountain. From the top of the mountain, you cannot see the mountain.

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zelph
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Re: stove making for caldera clone

Post by zelph » Wed Jul 27, 2011 4:35 pm

Put an insulating cover over your stove. A 3" diameter, aluminum cat food can will work. cut a hole in the bottom of the can and then some air entry holes . Experiment till you get it right. I have a modified Starlyte that reduces the amont of surface that the alcohol is exposed to. It's a controlled release of fuel.

Look up Z-Mart stove kit in the "search" feature.

I'm on a 2 week vaction right now and am limited to on-line time in the library where I am.
http://www.woodgaz-stove.com/

dimeotane
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Re: stove making for caldera clone

Post by dimeotane » Thu Jul 28, 2011 1:30 am

shingaling wrote: I was amazed how much difference is made by adding or subtracting 1/4" from the pot to stove distance.
Any suggestions what is the typical correct hight from the top of the stove to the pot?
For example, a starlyte, a flatcat stove, or anything else... how far should it be from the pot?

right now my burner is 3 cm from the pot but I only get up to 89c in 6 minutes on 15 ml of meth.
Last edited by dimeotane on Mon Aug 29, 2011 12:05 am, edited 1 time in total.

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shingaling
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Re: stove making for caldera clone

Post by shingaling » Thu Jul 28, 2011 7:10 am

If you have the material, make a bunch of pot stands at different heights and experiment.

Using 1/4" hardware cloth, I made several pot stands, ranging in height from 1" to 3", each increasing in height 1/4" (1 square) increments. Make the diameter big enough to accommodate different sizes of stove, and then do several burns until you find the sweet spot for each stove/pot combination.

Generally speaking, I've found that a stand that is too short will cause shorter burn times - I assume because too much heat is reflected back/trapped near the stove, causing the fuel to boil off quicker. Also, the flame might not be getting enough oxygen in that small space. You may be able to make adjustments to your stove (adding fiberglass to slow the fuel evaporation rate...putting a reflector plate near the top of the burner to reflect heat back up to the pot...change the number/size/location of air vents or flame jets on the stove, if any) BUT, it's quicker to do the burn again with a stand that's a different height.

Each increase in height will affect the burn time, the boil time (if it does boil) and the flame pattern on the pot. I try to keep the flames on the bottom of the pot only.

And then, once you tweak everything so that you get a boil every time, ask yourself: What do I change to boil 4 cups of water? What do I change if I want to simmer or bake for 20 minutes? How will the wind/cold affect the burn? How many more tests can I do before my wife kicks me out of the house?
Any road followed precisely to its end leads precisely nowhere. Climb the mountain just a little bit to test that it's a mountain. From the top of the mountain, you cannot see the mountain.

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zelph
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Re: stove making for caldera clone

Post by zelph » Thu Jul 28, 2011 7:51 pm

great advice from shingaling :D

The farther away from the flat cat the better. What does the maker of the stove recommend?
http://www.woodgaz-stove.com/

realityguy
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Re: stove making for caldera clone

Post by realityguy » Thu Jul 28, 2011 9:41 pm

How many more tests can I do before my wife kicks me out of the house?
I think Zelph can give you the answer to that one... :lol: Around here..as long as I'm baking something for dessert she doesn't seem to mind.. ;) ...:mrgreen:

Heat verses distance to the pot. :roll:..I found on my two stage sheba can stoves(search sheba or simplicty,spice can) that when potstands are placed low within 1" from the pot I can get boils from the inside smaller 1" simmer burner ring because of the increase in the heat factor,making it burn clear out on the outer perimeter of the stove;when using an aluminum shield for wind protection and it won't simmer like it normally does.Raising it up to about 1-1/2" seems to maintain a two stage effect with the stove for boiling ..then simmering.With a caldera,you may need to raise the cone off the ground some for maintaining a simmer mode;let enough air in there to keep things cooler and simmer with the same stove..or use a simmer ring to decrease the burner's flame diameter/heat factor and consumption of fuel.
Maybe some type of adjustable simmer ring will allow you to use the stove for more purposes without carrying a lot of additional pieces..and make it more adjustable for occasional wind,higher temperatures outside,snow or wet areas on the ground around the stove, or other factors you may run into on the trail that normally adversely affect the stove from your testing at home in usually perfect conditions.I have yet to see my stoves work as well on the trail as on the stainless counter at home in the garage..and I know I won't be packing that with me! :lol: It's nice to have some adjustment mode to compensate for those outside factors.How about an air damper door on the non-wind side of your cone? ;) I'm kind of assuming your potstand is your cone with that idea... or raise it off the ground a tad..
The views and opinions expressed by this person are his own and not the general consensus of others on this website.Realityguy

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zelph
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Re: stove making for caldera clone

Post by zelph » Sun Jul 31, 2011 10:04 am

All tests should be done while your wife is not home. You need to know also the exact time she'll return so you can have plenty of time to get rid of the evidence. :D

Learn to bake muffins with your stoves so you'll have some proof of how well they work and the benefits of testing them in the kitchen. ;)

Sometimes things can go wrong, ask DLarson :P He has a video of his remote fueled stove that is exciting.
http://www.woodgaz-stove.com/

dimeotane
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Re: stove making for caldera clone

Post by dimeotane » Fri Aug 05, 2011 12:00 am

Any thoughts on the difference in results between using a stainless steel sierra mug vs using an aluminum pot? Will one absorb the heat from the stove better?

By tweaking my stove and potstand I managed to get to 95c in 7 min using 15ml meth, but I had to switch to a Brunton aluminum pot with lid first.

Using the stainless steel mug I only got up to 75c. Perhaps the steel is thicker walled than the aluminum? Maybe it's the effect of the material? Also the steel pot had no lid on it.

I'll post a picture of my setup after I do more testing. I'm using hardware cloth for the pot stand. My stove is stuffed with fiberglass and has 12 'blades' bent 90". I'll post a pic later.

The hardware cloth potstand is a good idea for testing different heights because it's easy to measure out different heights in 1/4" increments. It easily makes a good lightweight potstand in general.
Last edited by dimeotane on Mon Aug 29, 2011 12:04 am, edited 1 time in total.

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shingaling
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Re: stove making for caldera clone

Post by shingaling » Fri Aug 05, 2011 7:58 am

I think that aluminum transfers the heat a little quicker. I pick aluminum, though, for the weight. If I'm just day hiking, I don't want to lug anything heavy. If car camping, I bring out the stainless - especially if I'm using the pots over wood stoves or campfires.

Jason Klass did a couple of videos on where to start when putting together a cook set (with good emphasis on matching the pot with the flame pattern). I see now that he's also got a review of the Flat Cat stove:
http://www.geartalkwithjasonklass.com/

I also note that in the Flatcat videos, jonfong always recommends using a 1.3l pot, which is about 5 1/2 inches in diameter. The Flatcat is about 3 inches in diameter, and the flame pattern is probably 3 1/2 inches wide - wider than a Sierra cup. I've never had success putting flames up the sides of a pot. I like small mug-sized cups, so I'm always searching for those stoves with more of a central flame pattern that I can focus on the bottom of the mug.
Any road followed precisely to its end leads precisely nowhere. Climb the mountain just a little bit to test that it's a mountain. From the top of the mountain, you cannot see the mountain.

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