just a bit of fun...
Having seen Matt BCUK's thread on the Caldera Cone, I thought I'd have a go at designing a clone.
It actually started last night, as I was trying to figure out how to improve the vapour chamber in a Red Bull side burner. I decide that, rather than simply place the inner wall between the pressed rings on the can bases (which gives a very narrow vapour chamber), I thought I'd made an inverted conic section wall, held in place by the pressed ring at the top, but hitting the pressed dome of the bottom can.
A little bit of basic maths allowed me to derive the inner and outer radii and the conic sector angle to create a conic section of any size and shape I wanted.
Then I thought "hmmm... that's a Caldera Cone, isn't it..."
So, a bit of PostScript later, and we have a programmable Caldera Clone generator, written in PostScript, that allows you to set all tha parameters you need to suit your pan and burner setup:
Pan diameterPan heightBurner heightBurner flame offsetHandle widthHandle depthNumber of holes at bottomNumber of holes at topSize of holesScale to fit A3Split into two pages
The parameters are set by simply editing values in the file.
The idea is to print the design at full size (printing on two pages if necessary), and using the template to cut out some thin aluminium sheet (e.g. 'oven liner').
Now, if only I could find some of this mythical 'oven liner' that the Yanks seem to find at every corner shop and supermarket...
To use the file, cut & paste the following post, and save to a text file called clone.ps (or whatever name you want). Then use GhostScript/GSView to view and print the design.
Enjoy. It's only a bit of fun, after all...
Okay, here's an example...
This is very interesting and usefull Cap'n, thank you.
I recently experimented with a truncated cone like the caldera but not as tall/wide.
I wanted the mug (Alpkit) to sit on top of the cone, thus creating a stable base/pot support and windshield that would stop any heat being wasted up the side of the mug yet would be able to be rolled up inside the mug for storage. The only thing that puts me off the Caldera is the packing of it. Anyway the experiment was a flop as the stove was starved of oxygen even with large ventilation holes on one side.
I did all the calculations by hand and then used the drawing package at work to print it out but it was a very long and tedious affair. I'd like to go back and experiment some more with different sizes untill I get something that performs the way I want. This will make things much easier to do so I think.
I must admit I know nothing about Postscript/Ghostscript but I'm now off to trawl the net to learn.
(I just used stainles steel shim for my prototype/flop so will be hunting the mythical oven liner also)
Thanks Bigbananafeet (Sandy)
The first paper prototype managed to support my MSR Ti Kettle...
I didn't remember some of the sizes correctly (such as handle depth and width). They've now been corrected, allowing for top and bottom handle width settings, and the upper holes have been made bigger and moved down.
I also have a cunning plan for a simple locking mechanism for the interlocking tabs.
BBF, you shouldn't need to know much about PostScript, other than to edit the user parameters as indicated (and the 'expert' parameters if you wish).
GhostScript and GSView can be downloaded for free from here. They're very good tools.
Whilst the code isn't perfect (bashed in very quickly), it seems to cope with a reasonable range of parameter variation.
> windshield that would stop any heat being wasted up the side of the mug
Of course, there's a problem with this, as you must have a way for hot combustion gases to escape upwards; that's the only way they'll go... If you don't allow these gases to escape, the burner will go out. Or produce a lot of carbon monoxide.
The Caldera cone is a nice way of ensuring the hot gases stay in close contact with the pan, even if it's the side of the pan. As long as they're in contact with the pan, they'll continue heating the contents.
Very impressive! Thank you for your efforts.
A couple of questions if you don't mind?
Are the figures in the code the ones that you actually used for your MSR Titan Kettle? Or are they the pre-corrected ones? If so, what were your corrected ones? /forum/smilies/wink_smiley.gif ]
What does the 'Burner flame offset' variable represent? Is this the distance from burner top to pot bottom, or something else
I will also be very interested to see the version with the updated tabs.
I did some tests
classic windscreen: 12 gr
(home made) caldera windscreen:68 gr
used a ionstove
500ml water: 8°C-> 100°C
classic windscreen: 14 gr meth (=18 ml) -> 95°C (13 min.39sec)
caldera windscreen: 13 gr meth ->100°C (14 min. 20 sec)
esbit+ classic windscreen: 12 a 13 gr esbit (13 min.) ->100°Cesbit+ cone: 12 gr esbit (11 min.) ->100°C.
Yes, the burner offset is the gap between the top of the burner and the bottom of the pan.
In a Trangia, this is 24mm.
Having measured my MSR properly, the figures are:
/panHeight 95 def % height of pan/panDiam 116 def % diameter of pan outer walls immediately under rim/handleWidth 22 def % max width of pan handles/handleDepth 78 def % measured from top of pan to lowest point on handle
I've since refined the design to allow top and bottom handle widths, nice rounded corners on the handle hole, and a finger locking mechanism.
If anyone wants the latest version, drop me an email. It's a massive 6013 bytes (oh, the beauty of PostScript!)...
Oh, and I should point out that I've only ever seen pictures of a genuine Caldera Cone. I just took the basic conic section idea and designed the rest of the features.
The ratio of pan diameter to base diameter, for instance, is set to 1.5, as that seemed reasonable. I don't know what is 'correct', but, since you can set it to any value you like, it's up to you...
Im dowloading the ghostscript program right now and I'll have a play with it. I'll probably email you for the latest version later Captain.
Another attempt, this time with the correct pan height (86mm). Note the narrower handle opening.
> if you're fortunate enough to be using OS X on a Mac - a FAR better hiking computer setup IMO
Unless you want to run any of the mapping programs...
Macs may run DisplayPostScript; the Next machines did; i.e. native PostScript display.
GSView runs perfectly well, and is better for PostScript code development, as it includes debug information if you mess up. Well, I'm guessing Preview won't do this, not having a Mac...
Glad you think it may be of use. As I said, email me for the latest version.
> Im dowloading the ghostscript program right now
BBF: you'll need GSView as well; this is the 'front end' to GhostScript.
did you make a cone out of aluminium or are you still on the oven liner quest?
Seriously, have you located a suitable material for this?
It’s not all hill walking and Kendal mint cake
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