caldera cone

Bought a discounted caldera cone (discontinued model) at BPL, then trimmed a little off the top to resize it for a barely larger pot.

Suggestions for building one: Start with a model cut from sturdy paper before cutting the real one from thin aluminum. Heavy scissors, but not as heavy as tin snips are good. Use a pen on the end of a no-stretch string as a drawing compass. A three dimensional cone is formed from a two dimensional (2D) circular band. Cone height is the distance between the two circular lines. The length needed on the two partial circles is about a third of each of the whole circles. For the top of the cone, 3.14 times the diameter of your pot is the 2D length needed, but add extra for an overlap to fasten the ends together.

Plan B: Get flashing tall enough, cut a length just over 3 times the diameter of the bottom of the cone. Form that into a circle with the sides slightly overlapping. Pin the overlaps together at the base, leaving the top loose. Then shape the top into a smaller circle that fits your pot. Mark where you need to trim, then disassemble to cut out your cone, leaving some overlap material on the sides for joining the two ends together.

The pro built one has a base that is 2 inches wider than the top, with sides 7 inches tall. Consider how tall you need your pot to be above the stove.

Since I haven't built one, if someone does, please extend the above suggestions into directions.

This is a link to an Excel spreadsheet set up for making a truncated cone http://jwilson.coe.uga.edu/EMT725/CarlCone/CarlCone.html
Click on the reference to the person from Australia as it is an Excel formula that only requires inputting 3 measurements. I made several paper patterns first (fitting this exactly is not easy) and then a final one from a foil oven liner. I made one to use with my FeatherFire (I believe already the most efficient alcohol stove on the market) and my initial test indicate a 35% savings in fuel. Later in the fall I'll do a full write up on the patterns, fastening, etc.

i built a similar style stove that works for wood burning and for a wind screen w/ alcohol stove. mine is just a cylinder that fits around a snowpeak 900. I can boil water on a hand full of twigs in about 5 min, and it takes about the same to boil with my pop can alc. stove. i will have to get some pics taken soon. It is about 10 inches tall and has vent holes, and a place for me to add wood when i need it, the pot sites all the way down and rests on the rolled rim around the top.

here are pics of my stove, it is made of stainless sheet stock and weighs about as much my snowpeak trek 900. the trek 900 sits down in the stove, resting on the rolled rim of the pot. this insulates the sides of the pot somewhat and makes it very stable. I put 4 triangular cutouts along the bottom, keeping part of one side clear if i need to block them from wind, and 4 rectangular cutouts at the same level as the bottom of the pot. I can boil 2 cups of water with a hand full of sticks in around 6 min. it also works well with an alcohol stove, pressurized popcan type. i have not tried it with an open alcohol stove but i think it would still work well, I add twigs through the hole near the handle, in my next version I will have a hole on the opposite side from the handle for adding fuel, and the handle hole will only go down far enough for the handle to keep the handle cooler and the stove more stable. hope this is a design others will try. thanks.

thanks for the pictures aj makes understanding what is being discussed easier. how do you pack this up, rolled or flat?

for many years I have just carried a flat version, ill make a new thread.

A few questions...
Does the cone fit snugly around the pot at the top, or is there a gap?
Are the openings level with the pot bottom, higher or lower?

I am packing it rolled up inside my cook pot with the cook pot lid on the top. I keep me fuel, alc. burner, utensils, cup, and bear hang line in the " tube" formed from the pot, stove and lid. Mine is made of stainless, witch is a bit heavier, but will not melt like aluminum. I have melted aluminum shields and pot stands with my alc. burners, once in the field where i ended up having to make a pot stand out of a discarded canteen i found in a shelter w/ my fork and my mulitool. no more aluminum pot stands or shields for me.

Yes the aluminum will melt and after melting a half dozen or so I finally got the thing to co-operate. Proper amount of fuel, proper diameter of cone and stove. And height of pot from stove. It still warps slightly but what a hassle. Although it held up well on my last trip, I will source stainless and build a new one. I sized mine for a heine pot but am considering a new coated 3 cup cook pot with a lid. I bought a trangia stove that I want to use next trip and it will definatly make molten metal of the aluminum. It seems to put out much more heat than my pop can stove.

Aside from the differences in stove, any evidence the CC makes a noticable difference in fuel usage in the field?

My brother bought an AGG caldera cone with matching stove. I use the penny stove. (both of us have the AGG pot) we've been on trips together and while his caldera is nice, from a practical in the field purpose it doesn't seem like he uses any less fuel. (me using the penny
stove with a foil windscreen, and he using the caldera stove and cone, both of us with
the same pots)

im not sure if it is worth having it if you are always going to use the alc. burner. Seems like a simple foil wind screen will do as well. i built mine so that i would be able to carry the alc. burner and only a few oz. of fuel for very rainy days or any time i cant find a hand full of twigs. This will also save me money in the long run because i will not have to buy fuel nearly as often.

Unfortunately then I'm back to - why bother with the screen at all - I just use a few more
twigs <img src="/forums/images/graemlins/smile.gif" alt="" />