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The Evolution of a Winter Stove - Part 3
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Stuart R
(Scunnered) - F

Locale: Scotland
Gas stratification on 12/04/2013 10:06:26 MST Print View

Yes but "analysis shows that stratification does occur, but it requires a column of static air several kilometers high to have a major impact" i.e. not in your average gas canister.

http://chemdaq.blogspot.co.uk/2012/09/gas-stratification-is-not-relevant-to.html

Go on, get a canister stove, you know you want to...

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Stove in use at -30 C (-20 F) on 12/06/2013 15:57:40 MST Print View

Hi All

A photo from one of our beta-testers, Douglas Frick (to whom my thanks).

Douglas Frick Winter Stove at -30 C

Douglas tells me it was -30 C (-20 F) when this photo was taken. A shade cool imho. But clearly the stove can be used at that temperature.

Cheers

Edited by rcaffin on 12/06/2013 15:58:16 MST.

Rick M
(rmjapan) - F

Locale: London, UK
Re: Stove in use at -30 C (-20 F) on 12/06/2013 17:36:37 MST Print View

At such -30C extreme cold, does one still follow the standard procedure of starting the stove with the canister upright and then inverting it after a minute or so once the preheat tube gets hot?

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Re: Stove in use at -30 C (-20 F) on 12/06/2013 18:45:00 MST Print View

"At such -30C extreme cold, does one still follow the standard procedure of starting the stove with the canister upright and then inverting it after a minute or so once the preheat tube gets hot?"

Looks like only one person knows for sure.

With the old Gerry and Mark III stoves (and similar), you had no choice. The were liquid fed, but upright.

Robert Blean
(blean) - MLife

Locale: San Jose -- too far from Sierras
What do you suggest for a wind screen? on 12/06/2013 18:52:36 MST Print View

Roger,

What do you recommend using for a wind screen with your stove?

Edited by blean on 12/06/2013 19:30:45 MST.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Stove in use at -30 C (-20 F) on 12/06/2013 19:10:42 MST Print View

> At such -30C extreme cold, does one still follow the standard procedure of starting
> the stove with the canister upright and then inverting it after a minute or so once
> the preheat tube gets hot?

It's a bit more complex at -30 C. For a start, the gas canister will not be warm enough to push out ANY fuel if it is at ambient, and this goes for ANY canister stove. So you need to get the canister a bit warmer than -24 C to get any joy (ie fuel) at all.

For ANY inverted canister stove at very low temperatures, some skill is needed. You can start with the canister upright and hope to get some gas out - it will be mainly propane with just a little butane. But running the stove for some time with the canister upright could be said to be storing up problems for the future, as the %propane will be falling rather fast. See http://www.backpackinglight.com/cgi-bin/backpackinglight/effect_of_cold_on_gas_canisters.html for an in-depth discussion of what happens inside the canister at very cold temperatures.

You might like to note there is a Coleman Xtreme behind the lit stove, to the left. The canister for this stove is the Coleman Powermax, and this always give a liquid feed. You cannot get a gas feed out of it. So the standard method for lighting an Xtreme is to first warm the stove in your hands (which happens as you set the stove up), then to light it at very low power. There may be a few burbles of orange flame right at the start - no matter. As the flames heat the preheat tube, the stove starts to function in the normal inverted canister mode.

You can do exactly the same with my stove and any canister. That is, you can start with the canister inverted if you wish. Just run it kinda slow for a little while as the heat shunt warms up. Gradually increase the power when the stove body feels warm.

One has to be flexible ...

Cheers

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: What do you suggest for a wind screen? on 12/06/2013 19:26:50 MST Print View

> What do you recommend using for a wind screen with your stove?

Have a look at When Things Go Wrong, about half way down. The pic is labeled 'Cooking dinner in the vestibule of the tent'. That is a Trail Designs windshield - one of the plain unvented ones. I leave a gap where the stove control valve handle sticks ou, may 20% of the circle. I leave a gap of about 15 - 20 mm between the pot and the windshield. OK, it's probably a bit more in this photo - it isn't really critical. And I have the windshield come about 1/2 way up the side of the pot, or maybe 3/4 of the way.

But any similar bit of aluminium shim or heavy foil will do just fine.

Cheers

Edited by rcaffin on 12/06/2013 20:40:24 MST.

Douglas Frick
(Otter) - MLife

Locale: Wyoming
Re: Re: Re: Stove in use at -30 C (-20 F) on 12/08/2013 21:32:50 MST Print View

Sorry for not responding sooner, I was out camping this weekend.


>At such -30C extreme cold, does one still follow the standard procedure of starting the stove with the canister upright and then inverting it after a minute or so once the preheat tube gets hot?


I had three inverted-canister stoves set up: the beta Caffin stove, a Coleman Xtreme, and an MSR Whisperlite Universal. All had set out overnight (low of -34C / -29F) with their canisters attached (so they wouldn't warm by handling), exposed to the air, and insulated from the snow with silicone pads. The Caffin stove had a new Snow Peak Giga Power 110g canister. I lit it with the canister upright (small flame) and _immediately_ inverted the canister, without waiting for the heat shunt to warm up. As expected, it flared up; I dropped my pot on the burner; and after about 20 seconds, the heat shunt warmed and it settled down to a nice flame. As Roger mentions in his post above, it was burning mostly propane at the start, which is why I immediately inverted it to save the propane for pressure. The wind had dropped so I didn't need a windscreen, and the heat from the burner warmed the canister a bit more, which kept the stove going without intervention.

The Coleman Xtreme had a Powermax canister that was about 1/3 full. It wouldn't start until I poured some (precious body-temp) water over the canister. It ran after that, but the flame didn't really get roaring until I heated more water to pour over the canister. If I had set the canister in a basin before pouring, I would have wasted a lot less water.

The MSR Whisperlite Universal had a 3/4-full Snow Peak canister, and it wouldn't start. I closed the valve, inverted the canister, and poured warm water into the concave base. I let it sit for a minute, so the heat from the water could work its way down the side of the canister to the liquid fuel, then lit it in fireball mode. It flared a while until the preheat tube warmed up, then settled down nicely. The water in the bottom of the canister soon froze solid, but it had done its job of producing sufficient gas pressure.


So two of the three stoves were non-starters (insufficient gas pressure in the partially-used canister to force either gas or liquid down the hose to the burner), and probably the only reason the Caffin stove started was that it had a brand-new canister. However, by simply applying a bit of warm water to their canisters, both non-starting stoves soon ran fine. I intentionally tried starting the stoves with chilled canisters, and inverted them cold, to see if/how they would work under these conditions. If I had either slept with the canisters or set them in water baths before attempting to start the stoves, the stoves would have had no problems starting and properly heating the preheat shunt/tubes, and thus I could have avoided the flare-ups from burning liquid-state fuel. I should also mention that I slept under a tarp, so the flare-ups weren't a problem; there's no way I would invert the canister without a hot preheat shunt/tube in the vestibule of a tent!

I also tested an upright-canister stove, but I'll post about that in a separate message.

Edited by Otter on 12/08/2013 22:01:35 MST.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Re: Stove in use at -30 C (-20 F) on 12/08/2013 22:08:23 MST Print View

I might point out one more trick. When you get up on a cold morning and you think you will need some warmth to start these canisters... just drain the dragon, so to speak. The fluid is plenty warm, and it is going to go to waste anyway. Just make sure that you don't get frostbite in this process.

--B.G.--

Douglas Frick
(Otter) - MLife

Locale: Wyoming
UPRIGHT CANISTER STOVE in use at -30 C (-20 F) on 12/10/2013 20:57:29 MST Print View

I also wanted to test an upright canister-top stove under challenging conditions.


upright canister stove at -30C / -20F


That is a stock Fire Maple FMS-300t stove with a nearly-empty canister (approximately 3 grams / 0.1 ounce of fuel left), which is about the worst case for cold weather. At room temperature, I had shaken the canister and couldn't hear any liquid slosh. With the canister/stove combo having sat out overnight and exposed to ambient air at -30C / -20F, I opened the valve and held a lighter to it: no hiss, no flame.

I then set the canister in a shallow cold-water bath. (I used a lid from a jar of protein powder; 1.0 oz / 28g.) After waiting one minute, the stove lit easily and ran without flare-up, just as if it was warm out. The flame guttered and died after about three minutes--canister empty. Was it just the propane that burned off? Nope. Afterwards, I let the canister/stove combo warm up to room temperature. I lit it, and it held a very small flame for 10 seconds, then went out. Clearly, it had burned the remaining isobutane/propane mix, not just the propane.

I prefer and trust an inverted-canister stove when it's cold, especially for longer burns, melting snow, stabilizing larger pots, with a close windscreen, etc. But upright-canister stoves also work just fine at -30C with proper technique. I think if people knew this trick there would be a lot less trepidation about using canister stoves in the cold.

Edited by Otter on 12/10/2013 20:59:34 MST.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Update on the UL Winter Stove project: ex stock on 01/01/2014 21:58:03 MST Print View

5595: 19 winter stoves lined up finished

Well, this is batch 4, all 19 of them. 8 have been sold already and will be
posted in the next couple of days. The rest are available ex stock. We have
moved from many weeks of lead time to on-the-shelf!

Going from a one-off MYOG hack for myself to a small production process
safe for others has been 'interesting' - especially for an academic. My
respect for all those cottage industries out there has gone up
considerably. The number of production problems encountered was more than I
had expected, but probably par for the course.

My CNC had a recurring 'fault' in the electronics which kept shutting the
machine down. The system said it was getting a 15 Amp over-current problem
on one of the drive motors - which sounded bad as things start to melt at
those current levels. It turned out to be a design fault in the
fault-detection circuitry. I modified the circuit so it would work
properly.

There were delays in getting some parts - with the supplier in one case not
bothering to tell me that there would be a 3 week delay for an order quoted
on their web site as 'ex stock'. We 'discussed' the matter (politely!), and
the critical parts were supplied Express (overnight).

One of the supplied components changed source during production, with the
new part being 'less than satisfactory'. I think the new part came from
China, but can't be sure. I had to find a completely different part to
replace it and redesign the stove body to handle that. Fortunately that was
not hard. You might not even notice the difference.

A couple of early beta testers found some tiny hiccups, which were
individually fixed, but nothing major. One tester had a problem with a
Powermax canister valve which I don't understand (it would not open
properly), but I do know that the crimping of the valves on those canisters
was 'variable' as the supplier was changed. A slightly longer pin solved
that for him.

A couple of almost invisible cosmetic changes were implemented when I had
the chance. Here's the burner:
5593: Winter stove, batch 4, burning

More user photos of the stove in use in the field (especially in the snow) would be appreciated.

Cheers

E J
(mountainwalker) - MLife

Locale: SF Bay Area & New England
A beautiful sight; Photo of folded stove on 01/02/2014 11:43:06 MST Print View

Roger, best wishes for the New Year.

That's a beautiful sight...

Could you post a picture of the 300T and 116T burner stoves compactly folded up? Or just the 300T if that's the only one you'll be making going forward.

Edited by mountainwalker on 01/02/2014 11:45:13 MST.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: A beautiful sight; Photo of folded stove on 01/02/2014 21:53:03 MST Print View

Hi EJ

5607: my stove curled up inside a pot

OK, herewith a photo of the stove folded up inside an MSR Titan 1.5 L pot - our normal dinner pot for most walks. I usually get a lot of other stuff in with the stove. In addition, my folding windshield is inside the pot along with some rather solid Ti mini-stakes for holding the stove down. I think the stakes are a bit of an overkill, but the weight is negligible.

Then I thought 'how about a stove comparison'? So herewith for that too.
5603: several stoves compared to mine

On the left we have an MSR XGK with a small (white gas) fuel bottle, 429 g / 15.1 oz with no fuel in bottle

In the middle we have a Primus Eta Power with integral windshield and optional pot, with a standard 230 g screw-thread canister, 375 g / 13.2 oz plus canister but without the pot shown here

On the right at the back we have an MSR Reactor stove plus pot, with a standard 230 g screw-thread canister, 571 g / 20.1 oz with special pot, plus canister extra

Finally, front right hand corner, we have my stove with a small Powermax canister, 85 g (3.0 oz) plus about 68 g for the empty canister.

Cheers

Billy Ray
(rosyfinch) - M

Locale: the mountains
Inverted canister fuel use on 01/24/2014 20:28:50 MST Print View

I have a Roger Beta Stove.

So I've read the directions and played around with it at about 20F.

I have a question. Not about the stove itself, but about what happens inside the canister when using an inverted canister stove.

First, Roger's directions recommend using the canister upright for 30 seconds or a minute to prime the stove... to get the warming chamber warm enough so that the liquid fuel easily vaporizes when the canister is inverted. Question: If the typical canister contains only 20% Propane, will this priming cause you to run out of propane (and thus priming ability) before running out of butane??? Obviously, if you only primed one or twice or thrice during the life of the canister (cooking for long times inverted) this would not likely be a problem. But I'm only boiling 8 oz of water in the morning and maybe 12 oz of water in the evening. That's a high proportion of prime time to cook time (even if you cook while priming) so I fear I will run out of propane and thus the canister will be useless at cold temps before it is empty.

Second Question:
After the canister is primed and inverted, does the stove burn equal amounts or equal proportions of butane and propane? I'm thinking if one of the two is heavier/denser than the other it will settle to the bottom and more of that will burn.

Please enlighten me.

thanks,

Billy

Stuart R
(Scunnered) - F

Locale: Scotland
Re: Inverted canister fuel use on 01/25/2014 02:27:31 MST Print View

Billy

1. If your canister contains 20-30% propane, then when you are priming the gas coming out will be 50-60% propane, so the answer is yes, if you do a lot of priming and not much cooking then the canister will become less effective at cold temperature as the contents are used up. I don't think it will be useless tho'

2. The liquid propane and butane mix pretty well, so if the mix is 20% propane then that is what will come out when inverted.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Inverted canister fuel use on 01/25/2014 03:19:16 MST Print View

Hi Billy

As Stuart said, if you do too much priming the canister will get low on propane.

However, if you switch to a filter disk under the jet, have the stove just a little warm before starting (body heat?), and start with a very low flame, there is little reason why you can't do the prinming thing with an inverted canister. If you are using a Powermax canister that is what you will be doing anyhow.

Filter Disk:
A recent upgrade. Cut out a 6 mm diameter circle of filter paper from either lab filter paper (I had lots left over) or use a paper coffee filter instead. You may find some sort of paper punch will give you the right size disk.
Remove jet, remove any tissue paper from inside. Check the jet is clear.
Insert filter disk into socket/hole and push down to near the bottom. It doesn't have to go all the way. It should NOT be floating loose: that would be too small.
Replace jet with just a little tightening.

It seems to me, from my testing, that this works a whole lot better than the tissue paper. It seems to catch and delay small drops of liquid fuel so they vaporise before reaching the jet. Well, works for me. Yes, this is included in the latest version of the Instructions.

I am making yet another batch of stoves, but my CNC is STILL playing up. I think I will have to replace most of the older electronics - all the motor drives. This will delay me a little, but it WILL be done!

Cheers

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Inverted canister fuel use on 01/25/2014 08:06:25 MST Print View

isobutane boils at 8 to 16 F - I don't know why there is a range given rather than a specific temperature

You said you were at 20 F, so it doesn't matter if there is less propane in the mix.

Gary Dunckel
(Zia-Grill-Guy) - MLife

Locale: Boulder
re: Isobutane vapor temperature range on 01/25/2014 08:29:17 MST Print View

"isobutane boils at 8 to 16 F - I don't know why there is a range given rather than a specific temperature"

Jerry, since the vaporization temperature is lowered when the altitude increases, maybe that's why they state a range?

Billy Ray
(rosyfinch) - M

Locale: the mountains
Re: Re: Inverted canister fuel use on 01/25/2014 08:31:53 MST Print View

Thanks Roger and Stuart, very helpful answers.
Jerry, I have played around with the stove at 20F just because that's the lowest temps I've had to work with on my deck lately; not because that is the only temp at which I expect to use the stove.

Roger, another question:
I would like to use a windscreen around the stove and pot fairly tight around the pot in cold temps. Will the heat inside the windscreen harm the flexible fuel feeder tube?

thanks,
Billy

Billy Ray
(rosyfinch) - M

Locale: the mountains
Re: Re: Re: Inverted canister fuel use on 01/25/2014 08:40:05 MST Print View

Roger... also...
In your instructions sheet you suggest that it's and option to start cooking/put the pot on the stove while priming.

I would add that placing the pot and windscreen actually helps to shorten the needed priming time because having the pot on top of the flame (and the windscreen in place) shunts more heat out to the aluminum plate that transfers heat to the pre-heat chamber and thus warms the chamber faster and allows sputter free inversion of the canister sooner.

does that sound right?

Billy