In your blog you say
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I was wondering about the Caldera being a cone shape. Is it for stability or other purpose ? If I take a can ( say a #10 can ) make holes up and down, and buy a pot that just fits in, will that be almost as effective as the cone ? Or is there something else I am missing?

If, as in the above question, you have a cylinder within a cylinder, there won't be any space for air to flow up the sides of the pot. Yes, the conical nature of the Caldera Cone does provide for stability, but that's not the main reason for the cone shape. The conical shape creates separation between the walls of the pot and the walls of the cone so that heated air can be directed up the sides of the pot, transferring heat to the pot as it goes.


smile Well, a straight-wall will most definitely work , given adequate gap (10mm, or 8mm-12mm) I refer you to Pot Skirt Investigation, ETHOS 2010

I believe what the cone shape does better than a straight wall is promote swirling (venturi effect) at lower temperatures. This might mean slightly cleaner combustion; this might mean longer use-life for the cone; though I believe the difference at this scale is insignificant

I agree with your analysis of the purposes the cone serves
1. Entraps heat near the pot.
- yup, the air entering from the bottom robs heat from the cone (prevents cone melting), ie, the cone preheats primary combustion air (aluminum is reflective)

2. Protects against wind.
- yup, it protects the flame from blowing out
- the holes control the maximum amount of air available for combustion, and thus, maximum firepower

3. Controls internal air flow to maximize heat transfer.
- yup, it forces the hot gasses to scrape against sides of pot to maximize heat transfer (its a hot skirt)


You should definitely check out ( via translate.google.com ) All-round all-weather stove "The most comprehensive all-weather stove"
I really like the cardboard and aluminum foil prison smile its insulative and reflective

No screws or epoxy!! Pop-Up Fosterís Pot and Fin Shells , its a great folding/flanged/aluminum potskirt/windscreen, with 12.5 grams of alcohol ( 1 tablespoon ) it cooks 200 grams of rice in 400 grams of water ( 400 ml ) in a 750ml pot, using LannyPlans Builds an Alcohol Beverage-Can Stove


And this TLUD The Pop-Up Two Buck Stove , esentially the beefier version of the Pop-Up Foster's Pot