The Caldera Strata – a secondary cone

[Kevin Beeden]

One of the few problems with Trail Design's excellent Caldera Cone is the fact that it can only accommodate one pan, as it has to be carefully tailored to the pan.

Here's an idea for adding a 'secondary cone' for the Caldera Cone, allowing it to be used with a second, smaller pan. I'm calling it the Caldera Strata…

It uses curved folds in foil to make an annular extension for the Cone, forming a 'secondary cone' within the first. I got the idea for the circular folds when making conic walls for red bull burners; as I was breaking out the inner wall, I noticed that the folded curve formed a very stable shape, and thought I must be able to do something with it; now I've found a use…

The Strata uses two folds; an outer fold to allow the Strata to sit on the Cone, and an inner fold to form the secondary cone to support the inner pan. In order to fit to the existing Cone, the walls of the Strata are the same slope as the Cone, so that it fits snugly.

The design concept is very versatile, and can accommodate a wide range of height differences between the pans, controlled by the position of the inner fold.

For a cone wall slope s, a difference in pan radii dR, and pan height difference dH, the vertical fold depth f, can be found

f = (dH + s.dR)/2

For a minimum fold height x, the range of height difference that can be accommodated is

+/- (s.dR – 2.x)

So, for s=5, dR =10mm, x=10mm, the range of height difference that can be accommodated is

+/- 30mm.

A taller inner pan sits above the top of the 'normal' Cone.
A shorter inner pan sits below the top of the 'normal' Cone.
The base of the inner pan remains at the same height above the burner as designed for the main Cone and pan.

The down sides are that it cannot roll or fold up, so it has to be stored somewhere, and it's so light (6g) that it may blow away. It also takes some careful folding to make the curved folds. I was worried that it might get too hot and soften or melt, but it seemed to survive its first test unscathed; no sign of overheating at all, even though the flames from the burner played up the sides of the pan (it was a 'normal sized' burner).

Here's the method I used to score the fold lines:

Here's the first test firing with a Caldera Strata for an Alpkit MyTiMug in my MSR Titan kettle Clone:

[Keith Selbo]

… and nice workmanship too!

[Kevin Beeden]

I opened up the handle cutout after I took the pictures, so it looks a bit neater now.

Ideally, I'd make a Clone with handle opening to both kettle and mug, but I've taken the handles off my kettle; will have to tweak the Clone script to add some logic to find the optimum handle opening for the combined system.

I've just put in the numbers for a 400ml MSR Titan mug in the Kettle clone. It makes for a deep Strata, as it has to bridge a big gap between the two pans (20mm all round). This could be reduced by using a less steep wall slope for the Strata (as in my first, hacked together, rather than designed, paper prototype). It wouldn't fit snugly to the main Clone though…

[Roger Caffin]

Hi Kevin

Can I offer a caution here? The use of the word 'Caldera' is probably covered by a patent owned by Trail Designs. I suggest you contact them before they contact you.

Cheers

[Kevin Beeden]

Thanks, Roger. I've edited the post to add an explicit link to Trail Design's website, so it highlights their excellent Caldera Cone. All I'm trying to do here is extend the potential use of their Cone by addressing one of its few limitations, sharing ideas in the spirit of the MYOG community.

A couple of points.

– I'm not selling anything; the Strata is public domain information, and may be freely used by anyone wishing to extend the use of their Caldera Cone.
– Tradenames (e.g. 'Caldera Cone') are not covered by patents; concepts are (and, in UK, and thus RoW other than US, a patent title may not contain a tradename). TD might take offence at a potential trademark violation (but see below).
– Part of the original intent of patents was to spur the sharing of information, to encourage what we'd now know as innovation. Thus, freely sharing the ideas encompassed in a patent is not a violation of that patent. Only commercial exploitation of that idea is a patent violation.
– Trail Designs do indeed have patents pending on the Caldera Cone, although, on a cursory search, I've not been able to find what they are in order to check what it is that they have applied for a patent on (purely out of curiosity); they're certainly not listed on Trail Design's website. If you have details of the patent application numbers, I'd appreciate it.

Besides which, if you do an internet search (including BPL), you'll find plenty of other references to the use of 'Caldera' to mean a cone-style pan support, including DIY articles, and I've not heard any cases of Trail Designs pursuing these in the courts; if anything, it's free publicity for them; I'd suggest that the number of active MYOGers is far, far smaller than the number of people who read MYOG pages, but end up buying their gear due to lack of confidence, time, ability or inclination… If TD want to take the Strata and make it, they're free to do so (just not exclusively).

If this thread causes BPL a problem with Trail Designs, then, of course, you're free to take it down. But I think you'd have to take down quite a lot of other threads and posts, too… Rand actually joined in a discussion entitled Caldera Clone, so my guess is they're pretty relaxed about the issue, and, judging by this thread, I think they appreciate the discussion and development of their product.

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