Forum Index » Editor's Roundtable » The Evolution of a Winter Stove - Part 3


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Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: Legs: centre-support vs tripod on 07/17/2013 20:08:05 MDT Print View

> The primary benefits are being able to couple the stove with a Caldera Cone

Please note that I do not recommend ever enclosing any canister stove, remote or upright, in a 360 degree windshield. The Caldera Cone is fine for an alky, but a canister stove generates a lot more heat and uses a lot more oxygen. Just don't do it!

I do recommend a 3/4 windshield, sitting about 20 mm from the pot, and coming 1/2 way up the side of the pot. You need room for fresh air to get in and for the hot air to get out - for both uprights and remotes.

Cheers

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: The Evolution of a Winter Stove - Part 3 on 07/17/2013 20:11:09 MDT Print View

> Is there a time frame for when the stove will be available to us who camp year round?

I have a few of the FMS-116T stoves here for immediate sale. I am still making a larger batch of the FMS-300 stoves. That will take some weeks yet to complete. No promises, and no payments accepted until I can ship.

Cheers

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Canister connector 3D printable on 07/17/2013 20:14:29 MDT Print View

> Was/could a 3d printer be used to make the canister connector?
No and no.

No 3D printer generates a surface smooth enough for O-rings. Post-machining would be needed.
The cycle time to print one unit would be many hours, at least as far as I know. That's too slow.

Injection moulding is possible, but even so not simple. Plastic shrinks on cooling, especially on lumpy bits. Thin shells are OK, but this is not a thin shell.

Cheers

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: The Evolution of a Winter Stove - Part 3 on 07/17/2013 20:17:42 MDT Print View

> what diameter circles would circumscribe legs and pot supports)
Legs: 130 mm circle diameter.
Pot supports FMS116T: 110 mm
Pot supports FMS-300T: 82 mm
Pot supports are exactly the same as for the upright stoves.

Folded up photo - OK, coming.

Cheers

Ross Bleakney
(rossbleakney) - MLife

Locale: Cascades
Re: Re: Re: Re: Legs: centre-support vs tripod on 07/17/2013 20:29:12 MDT Print View

>> The primary benefits are being able to couple the stove with a Caldera Cone

> Please note that I do not recommend ever enclosing any canister stove, remote or upright, in a 360 degree windshield. The Caldera Cone is fine for an alky, but a canister stove generates a lot more heat and uses a lot more oxygen. Just don't do it!

> I do recommend a 3/4 windshield, sitting about 20 mm from the pot, and coming 1/2 way up the side of the pot. You need room for fresh air to get in and for the hot air to get out - for both uprights and remotes.

I agree. A Caldera Cone concentrates the heat and supports the cook pot. These aren't necessary for a canister stove. Concentrating the heat in an alcohol (or wood) stove makes it work like a well engineered wood stove; the heat from the fire makes the fuel burn more efficiently. In this case, it is completely unnecessary. Supporting the stove is also unnecessary.

But a huge advantage of this design over an upright canister stove is that you can easily isolate the canister from the windscreen. This makes a wind screen a lot safer. You need to have a hole to let in sufficient air, but that is about it. Otherwise, the windscreen will help separate the burner from the canister. In other words, with this design, a windscreen makes the stove safer; with an upright canister, a windscreen around the entire apparatus makes it more dangerous. This means that to be really safe with an upright, you have to design a windscreen which goes between the canister and the burner, which is a pain the butt to build (a previous article describes how to make one).

Michael Martin
(MikeMartin) - BPL Staff - MLife

Locale: North Idaho
Re: Xtreme rod (and super secret winter stove technique) on 07/17/2013 20:30:16 MDT Print View

Ahhh, that makes sense. Thanks, Roger. I sold my Xtreme years ago when it became hard to find fuel so I haven't had one in my hands for a while. :-)

Like you, I've been trying to find/build the "perfect" winter stove for almost a decade. I've finally settled on a regular old sit-on-top canister stove with a bit of super secret tricky technique involved. ;-)

The trick is to stomp out a snowpit, say, 50cm in diameter and 50cm deep. I make sure the canister is prewarmed with body heat to get the fuel to initially vaporize. I lower the stove into the pit, light it, and let her rip. The volume of the pit is small enough that the stove heats it to 40-50F even when the outside temp is as low as -15F. (I've verified this with thermometers). The snow also buffers the pit temp by melting if it gets too warm, reducing the chance of thermal runaway. If it's windy, I'll partially cover the pit with a sleeping pad while cooking. The canister stays warm enough in the pit (well above 0C) to easily vaporize the fuel. The canister itself is plenty stable on the compacted snow, so I don't need any kind of stove platform. The pit makes a superb windscreen, so I don't need an aluminum one like I would with a remote canister stove.

Winter Stove Snow Pit

I've used this technique snow camping since 2007. I don't know what the lower ambient temp limit is, but I've used it successfully down to -15F with my old, faithful Giga stove and down to -5F with a Jetboil Sol. The Jetboil works particularly well as all the parts are connected and it's easy to lower into the pit. It does waste less heat than the Giga, though, so doesn't warm the pit as much and likely has a higher low-temp limit.

Cheers,

-Mike

Disclaimer: The above describes my personal stove technique. There are risks such as CO emissions in a reduced-oxygen pit, possible canister overheating/explosion, weather conditions that make it impossible to use, and the risk of the system failing and leaving you with no working stove system. Attempt at your own risk.

Edited by MikeMartin on 07/18/2013 01:11:06 MDT.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Xtreme rod (and super secret winter stove technique) on 07/18/2013 00:56:32 MDT Print View

Hi Mike

Stove pit ...
I learn something new every day!

Mind you, stomping a hole that deep in Australian snow might be a bit more difficult. It tends to be horribly solid. Even so, NEAT!

Cheers

Michael Gillenwater
(mwgillenwater) - M

Locale: Seattle area
Re: Re: Xtreme rod (and super secret winter stove technique) on 07/18/2013 01:33:31 MDT Print View

I'd be a little worried of the CO output of this setup.

Franco Darioli
(Franco) - M

Locale: Melbourne
The Evolution of a Winter Stove - Part 3 on 07/18/2013 02:43:32 MDT Print View

Michael,
Very simple , very clever... after all that is how a snow cave/igloo works.
Thanks

Bill Townsend
(Olmanwilly) - MLife

Locale: Midwest
Good work on 07/18/2013 08:37:33 MDT Print View

For us non-mountain folk, with your low profile is a true windscreen needed? I used to just lay my pack (or myself) on the windward side when the powermax stove fuel was still available here in the us. In snow, I use my caldera as a wind screen, just not closed up, I simply flip it over and jamb an inch or so of it into the snow/dirt leaving it open like a normal screen, got sick of using other alternatives. Been looking for a well thoughtout, and what appears to be a "universal" canister stove, weight is good for the type of stove, an ounce extra (if that) to use any brand canister you find is worth it. Well done Roger!

peter vacco
(fluff@inreach.com) - M

Locale: no. california
Re: Re: Re: The Evolution of a Winter Stove - Part 3 on 07/18/2013 09:05:44 MDT Print View

FANTASTIC !

all i can add is that if one desireth to deburr plastic parts, a fast way is to dust them with a propane torch flame.

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Good work on 07/18/2013 10:14:30 MDT Print View

Hi Bill,
Yes, wind screens are still necessary. They actually serve two purposes.
1) Shield from winds
2) Trap and concentrate heat output from the stove

Ignoring the first part 1) above, the second part is what is missed. Rather than distributing heat in a 180 degree arc, roughly speaking, it is trapped and sent back to heat the pot. As a corollary, any heat lost around the edges of the pot is also reflected back to the pot. Heat is produced in two parts: convective and through infrared radiation. Convective heating is through exhaust products and heated air that is not combusted. Infrared radiation acounts for a large portion, though.

Discussing convectition first:
I do not agree with a strict 3/4" gap around the top. This allows too much heat to be lost for no productive purpose. Conversly, too narrow of a gap will form a heat "puddle". The puddle will force heat down, into the combustion and stove. This is not what we are trying to heat, rather the pot, and what it contains, is the target. This will also increase CO production.

From this reasoning, I believe that a variable gap is needed. Depending on the setting of heat output you are using, anything between a 1/4" (on very low) to 3/4" (on high.) This will match the combustion products flow rate with their actual production. This assumes that air input is about 3-5 times exhaust output. Input is less important than output, however, so a good sized opening larger than needed will always work well. It also allows the air to cool the lower stove components.

Also, not all the heat is transfered upon contact with the pot. Some will be, some will not. Some will be picked up from the pot. This is usually carried away in the flow.

For infrared or radiative heating, using a wind screen made of aluminum or some reflective material alows the radiation to be reflected back to the pot rather than lost. Painting your pot black helps with this.

Using windscreens helps by about 25-30% given still air. In winds, they will help a lot more.

E J
(mountainwalker) - MLife

Locale: SF Bay Area & New England
Beautiful work Roger; TP jet filter and moisture, maintenance on 07/18/2013 12:08:23 MDT Print View

Beautiful work Roger, along with an excellent article on the product development.

Is there any chance the toilet paper filter could be compromised by moisture from high humidity or water from rain getting into the jet and deforming the filter?

Should the TP filter be proactively changed every X number of uses?

What would be a sign that the TP filter has been compromised (allowing gas to flow through but not catching contaminants)?

Forrest G McCarthy
(forrestmccarthy) - MLife

Locale: Planet Earth
Carbon Composite Gas Cylinder on 07/18/2013 12:28:29 MDT Print View

Cool looking stove. The next step is producing a reusable ultra-light fuel cylinder like the carbon composite cylinders used for paint ball guns and oxygen on Everest.

Carbon composite cylinders are already in production. Designing a lightweight DOT approved valve is the crux.

http://www.luxfercylinders.com/products/alternative-fuel-cylinders/443-type-3-alternative-fuel-cylinder-specifications

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Good work on 07/18/2013 17:21:20 MDT Print View

Hi Bill

> For us non-mountain folk, with your low profile is a true windscreen needed?
There's no magic here, just two points to watch.
* If the wind blows the flames sideways much, they won't be heating the pot.
* If the wind blows the hot air away, it won't be heating the sides of the pot either.

For that matter, what James wrote is equally appropriate. So anything which protects the stove is fine. Yes, I have used rocks, packs, boxes etc instead. But the extra IR reflection from a metal windshield adds a bit.

> I simply flip it over and jamb an inch or so of it into the snow
Um ... that's rather clever!

Cheers

Edited by rcaffin on 07/18/2013 17:23:03 MDT.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Beautiful work Roger; TP jet filter and moisture, maintenance on 07/18/2013 17:29:27 MDT Print View

Hi EJ

> any chance the toilet paper filter could be compromised by moisture from high
> humidity or water from rain getting into the jet and deforming the filter?
Um ... if you are getting rain inside the burner tube and through the jet, you may be taking outside cooking a bit TOO far! Humidity - nah, wouldn't worry. It will dry off pretty quick when the stove is running.

> Should the TP filter be proactively changed every X number of uses?
The ideal answer might be yes, but ... what is X?
If the canister is very clean (eg Coleman powermax) then X=100 is reasonable.
But if the canister is one of those Chinese ones I tried to use (once), then X < 1. The Chinese canister was full of very fine dust, and everything blocked immediately.

> What would be a sign that the TP filter has been compromised
Hum ... if you can't get a decent gas flow, then the TP might be rather blocked. Bad (dirty) canister.

Cheers

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Carbon Composite Gas Cylinder on 07/18/2013 17:36:45 MDT Print View

> Carbon composite cylinders are already in production. Designing a lightweight DOT
> approved valve is the crux.

I suggest that using a Lindal valve is the OBVIOUS solution here. That gives compatibility with every other canister AND stove on the market. Otherwise you would have cylinders with no stoves.

In addition, you might then be able to get cylinders rated for 100% propane, like the existing Sievert ones. Oh boy, winter fuel!!!!

Cheers

Josh Brock
(needsAbath)

Locale: Outside
fire maple model on 07/18/2013 19:51:29 MDT Print View

I just sent the link to Fire Maple Stove company and they are going to have a production model of this soon for half the cost.....JK

but seriously how long do you think it will take them to completely steal this stove? Given that some of the parts are already theirs and the excellent detail in which the engineering is described.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: fire maple model on 07/18/2013 22:44:12 MDT Print View

> how long do you think it will take them to completely steal this stove?
I have no idea.
Yes, I use a Fire Maple burner, and I know the designer at Fire Maple. But my article does not specify ALL the fine details which are essential to making the stove work.

If they want to negotiate with me later on, that's fine.

Cheers

Josh Brock
(needsAbath)

Locale: Outside
Re: Re: fire maple model on 07/19/2013 14:33:13 MDT Print View

"But my article does not specify ALL the fine details which are essential to making the stove work."

I see.... Smart you left out the part that keeps it from shooting fire balls at the user.