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DIYSteve
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PostMon Nov 28, 2011 11:35 am 
hikin_jim wrote:
The thing about a Reactor is that it's only good as long as you can keep the fuel temperature at or above about 20F (colder as you climb higher).
What's the reasoning for saying "at or above about 20F" when the boiling point of isobutane (at sea level) is 11F? As you acknowledge, the BP of isobutane gets lower as one goes higher, so most NWHikers using an upright can stove in cold temps are dealing with isobutane BPs of 10F or 9F or even lower. I won't repeat here my two simple and easy means to keep the can sufficiently warm down to 0F or even colder.

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hikin_jim
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PostMon Nov 28, 2011 12:21 pm 
Steve, If you take a stock, unmodified Reactor, you can run it on good fuel (no n-butane) to the point where the fuel temperature is about 20F at sea level throughout the life of the canister. Yes, isobutane vaporizes at 11F/-12C, but you need a certain amount of pressure in the canister in order to properly drive the stove. If your vaporization point is 11F, and your fuel temperature is 12F, the pressure in your canister will be so insipid that you can't run a stove off of it. Generally, about 10F/5C above the vaporization point will give you good operating pressure. So, if your fuel vaporization point is 11F, you generally want to shoot for about 21F in order to have good operating pressure. 20F is easier to remember, so I usually just say 20F fuel temperature for upright canister stoves using a propane/isobutane blend at sea level. As you ascend, the higher you go, the lower the ambient air pressure. As the air pressure drops, so does the boiling point of your fuel, so you can operate your stove at lower fuel temperatures, as shown by the below diagram.
Elevation_vs_Boiling-Point_Chart
Elevation_vs_Boiling-Point_Chart
Of course, if you modify the stove to divert heat from the combustion to the canister or add heat by some external means, then the fuel temperature will rise, and your stove will run fine. Two main take aways: 1. In all cases, it is the fuel temperature which matters, not the ambient temperature. 2. In order to have enough pressure to properly operate a stove, you need to have the fuel temperature be warmer than the vaporization point of the fuel. Generally, about 10F/5C above the vaporization point will give you good operating pressure. HJ

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DIYSteve
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DIYSteve
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PostMon Nov 28, 2011 2:09 pm 
Yeah, I know all that. With some few exceptions, NWHikers who encounter <20F temps in the PNW are at least a couple thousand feet above sea level, and often >6K above sea level if they are dealing with such cold temperatures during prime hiking season. So the BP for isobutane for most NWHikers in most NWHiker settings is somewhere below 11F. Okay okay, I know we're talking about fuel temp, but ambient temp is relevant is relevant to fuel temp. And, again, it's very easy to warm the fuel via several methods, two of which I've written about several times on NWHikers and will not repeat here.

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hikin_jim
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PostMon Nov 28, 2011 3:21 pm 
BigSteve wrote:
during prime hiking season
Yep. And for the rest of the year, they can refer to my post. biggrin.gif Just for reference's sake (if I'm doing my math right), the boiling point of isobutane at 6000' is 0F/-18C, so your fuel needs to be kept at at least 10F/-12C. Shouldn't be too much trouble to keep something at 10F, although as with all canister stoves, the canister will get colder as you use it. HJ

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Malachai Constant
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PostMon Nov 28, 2011 4:25 pm 
It is basic Pchem that when something evaporates it gets cold (that is how a refrigerator operates). That is why the canister quickly becomes covered with frost even though the temperature is above freezing outside. It is basic entropy change. In that way the outside temperature is a poor predictor of stove performance. Here canister stoves are useless in winter. tongue.gif

"You do not laugh when you look at the mountains, or when you look at the sea." Lafcadio Hearn
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hikin_jim
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PostMon Nov 28, 2011 5:00 pm 
Malachai Constant wrote:
when something evaporates it gets cold (that is how a refrigerator operates).
I have read of some refrigerators using butane as a refrigerant. Supposedly butane has less of a "greenhouse gas" impact than other substances used as a refrigerant. Hate to have a leak in the cooling system though. eek.gif HJ

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DIYSteve
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PostTue Nov 29, 2011 8:31 am 
hikin_jim wrote:
although as with all canister stoves, the canister will get colder as you use it
Unless, of course, you warm it up via one of several means, two of which I have discussed in several posts on Gear Talk.

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PostTue Nov 29, 2011 8:40 am 
Air temperatures in Stevens Pass mid-winter are typically in the 5-15 degree range at night. I've been in Commonwealth Basin overnight when it was below -10. I was at Lyman Lake just a couple of years ago in late September and woke up to 18 degree temperatures. It certainly can be difficult to keep a stove canister above 10F mid-winter in the mountains.

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PostTue Nov 29, 2011 10:16 am 
Schroder wrote:
It certainly can be difficult to keep a stove canister above 10F mid-winter in the mountains.
I think the whole gas vs. liquid fuel decision is sort of a personal thing. Some people absolutely detest liquid fuel and will go to any lengths to use their gas stove. I myself am pretty comfortable with either. If a gas stove looks like it's going to take too much fiddling with to get it to go, I just bring my XGK or something. My "planning number" is 20F. That's just me. I know guys who use their gas stoves well down into the single digits. If you've got something like a Coleman Xtreme, you can go down below 0F, especially if you do some canister warming. HJ

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DIYSteve
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PostTue Nov 29, 2011 10:26 am 
Schroder wrote:
Air temperatures in Stevens Pass mid-winter are typically in the 5-15 degree range at night. I've been in Commonwealth Basin overnight when it was below -10. I was at Lyman Lake just a couple of years ago in late September and woke up to 18 degree temperatures.
I usually take my XGK* for mid-winter trips where temps <15F are anticipated. I've had no problem using my Reactor down to 10F (ambient temp) and even colder a few times on crisp cold east slope high country fall/spring ski touring trips with isobutane-propane mix fuel so long as I use a water bath and/or copper wire heat exchanger. *And plenty of fuel because the XGK is a fuel pig

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PostTue Nov 29, 2011 5:19 pm 
It's all academic for me at this point. My Reactor can handle temperatures colder than I want to spend the night at these days. Give me a warm lodge in the winter. smile.gif

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hikin_jim
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PostTue Nov 29, 2011 6:10 pm 
Stoves that can operate at a lower temperature than you can. Hmm, I haven't got a blog post for that. wink.gif HJ

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Ski
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PostSat Jan 21, 2012 11:19 pm 
coleman_502-700_400A701_550B499
coleman_502-700_400A701_550B499
left to right: Coleman #502-700 "Sportster" DOM 07-74 purchased 02-75 Griggs Pasco Wa $12.77 - Fired, but never used in field. Coleman #400A701 "Peak1 Easy-Lite" DOM 1986 (?) purchased (?) $30.99 - Received second hand, I've never used it Coleman #550B499 "Peak1 Multi-Fuel" DOM 12-92 purchased 1993 Backpackers Supply Tacoma $43.50 - Workhorse. Coleman #550B499 "Peak1 Multi-Fuel" DOM 12-92 purchased 1993 Backpackers Supply Tacoma $? - Repaired by factory, then cannibalized for parts.
msr_dragonfly_11774-11776
msr_dragonfly_11774-11776
MSR #11774/11776 "Dragonfly" DOM 06-07 purchased 03-09 REI Tacoma $130.00 - Loud. Boils water fast. Doesn't do a low simmer as well as the Coleman above. * edit 08-02-13: for weights on above stoves, see here

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hikin_jim
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PostSun Jan 22, 2012 8:18 am 
Hey, Ski, Is it fair to say you like Colemans? winksmile.gif HJ

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Ski
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PostSun Jan 22, 2012 2:16 pm 
I never used a stove until 1993. The two on the left (502-700 and 400A701) were both given to me, and I've never used either, other than to put fuel in them and make sure they both worked. Both the 550B499 units have seen a lot of use. It's a good stove: blast furnace to low simmer (for rice). It's also a bit heavy by today's standards, so I retired it and got the Dragonfly a couple years ago. If you go back through my trip reports, you'll find I had recurrent problems with the Coleman in the field. I wouldn't necessarily atttribute that to bad design, but rather heavy use. So far the Dragonfly has been completely trouble free for two years. If it were a "car camping" thing, or I was making a cup of tea on the tailgate, I'd prefer the Coleman over the Dragonfly. No "set up", no fumbling around with the fuel bottle, pump, or windscreen: just fire it up and go.

"I shall wear white flannel trousers, and walk upon the beach. I have heard the mermaids singing, each to each."
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