Monday, December 26, 2011

The "Magic" of the Caldera Cone

(AKA, why is the Caldera Cone so efficient?)

I got a really good question in connection with my recent What "Color" is your Caldera? post. 
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?
Let's use the above question as a jumping off point for taking a look at just why the Caldera Cone stove system is so efficient.

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. In addition, the conical shape, much like an inverted funnel, affects the air flow in such a way as to cause more efficient heat transfer. Most stove set ups just heat the bottom of the pot via the flame. The Caldera Cone makes use not only of the flame but also the heated air. This is why the Caldera Cone set up is more efficient than other stove set ups.

Take a look at this photo.
Two Caldera Cone stove systems, side by side.  Note the air vents near the top of the burner.
Notice the vents at the top of each cone.  You can't see them in this photo, but there are corresponding vents at the bottom of the cone.  Air enters at the base.  As air is heated by the burner, it flows in a controlled fashion up the sides of the pot, transferring heat as it goes through the system, exiting out of the top vents. 

This is really a brilliant design. The cone serves (at least) four purposes:
1. Entraps heat near the pot.
2. Protects against wind.
3. Controls internal air flow to maximize heat transfer.
4. Supports the pot.

Most stove set ups, if they have a good wind screen configuration, do only numbers one and two. The "magic" of the Caldera Cone is that you get all four in one neat, practical, ultralight package. The conical shape and the placement of the air vents is not random nor is it optional if you want the kind of efficiency that you can get with a Caldera Cone.

Now, if you're car camping, you could just "throw fuel at it." In other words, when car camping where you don't care that much about weight, so you could simply go with an inefficient design and just burn lots of fuel to make up for it. But if you're carrying that fuel on your back, it's a wholly different equation.  As for me, I'll take an efficient stove system like the Caldera Cone, thank you very much.


In case you missed any of the series:


  1. Hi Jim! With all of the recent posts about the Caldera Cone I'm wondering if it could be compatible with my Primus OmniFuel... I assume not :(

  2. Probably not. With something as high output as an Omnifuel, you'd probably melt the Caldera Cone, and I don't think the Omnifuel would run well inside the low oxygen environment of the Cone.

    You should use a windscreen, but I'd say you'd be better off with an MSR or Primus windscreen with your Omnifuel.


  3. Brilliant stove and one I've used on EVERY trip for 2 years or so now. Never looked back.

    For general backpacking, it's a beaut. I light it, wander off, come back and all is well and done.

    Absolutely love the Caldera Cone - works ok with a Trangia stove too :)

  4. @Lewis: thanks

    @terrybnd: Isn't it great? I love it. It's what I call a "fire and forget" stove. Once it's started, there's absolutely nothing to do. I go and set up my shelter or what have you. Come back in a few minutes, and... job done. Nice!

    I keep hearing that it works with a Trangia burner. I'll have to try that.


  5. With the Caldera Cone there is still one point where one could improve efficiency: Because the Cone is made of a heat conducting metal it takes heat from the rim of the pot and from the hot air and radiates it on the outside of the Cone. If the Cone were made of heat insulating material this heat could be used for boiling the water.

    1. True, but heat loss through the walls of the cone isn't particularly significant. You could cover the cone with a sheet of carbon felt cut to mimic the cone, but that would be a bit of fuss, and I wonder if it would be worth it in terms of efficiency gained. Interesting experiment, though. If you use a titanium cone (the Ti-Tri Cone from Trail Designs is the same general pattern but is made of titanium instead of aluminum), then you'd also minimize heat loss (Ti is a poor conductor of heat).