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Fire Burn And Cauldron Bubble:
#1
Posted here at the request of ML...



BTW, all columnar data no longer has it's numbes lined up neatly... Forum software strips all tabs and spaces greater than one. It makes some data a bit more difficult to read, but it is all here.



Many thanks to ML for his efforts!



Bill



**********************************



(This material was originally posted on the Hoods Woods Forum in August, 2001)



Fire Burn and Cauldron Bubble: An ad hoc comparison of Alcohol, white-gas, and solid-fuel stoves.



On and off, most recently in the Photos section, members of this Forum have discussed the merits of simple alcohol burners/stoves. I’ve decided to add a little, shall we say, fuel to this fire in the form of a hard-numbers comparison.



Here’s the scenario: Last evening I measured the boil times for a variety of stoves under the following conditions:



Air Temperature: 78 degrees F

Water Temperature: 72 degrees F

Water Quantity: 500ml

Elevation: 770 feet MSL

Barometer: 29.05 in. Hg



Four stoves provided the data:



1.

An MSR WhisperLite Internationale using white gas (a.k.a. Coleman Fuel. This stove will burn a variety of fuels, including diesel, Jet A, and several common solvents).



2.

A Trangia alcohol burner in a three-piece aluminum burner base/pot support (the Westwind Model), burning a 90%/10% denatured alcohol/water mix.



3.

An old Svea 123R using white gas.



4.

Also included was a GI Canteen-cup burner (NSN 8465-01-250-3632) and a steel GI canteen cup with a Trioxane tab as the solid-fuel component (NSN 9110-00-263-9865, MIL-F-10805D).



Note that the first three are small backpacking stoves. Certainly one could use them for car camping, but a larger, hotter, more stable “suitcase” type propane or white-gas stove would be a better choice for the car-bound. As a control, I also included my fine 1948 natural-gas Rheem Wedgewood kitchen range which weighs something like 600 pounds--definitely a poor backpacking choice, but a superior piece of culinary equipment for the house-bound.



I used the same pot for all the stove testing, a curved-bottom stainless-steel 750ml MSR Stowaway model with a tight-fitting lid. The choice of this pot per se is irrelevant, but it is representative of a small backpacking-type pot appropriate for use with any one of these stoves. With the GI canteen stove, I used the GI canteen cup for a “pot.”



MSR Notes:



The WhisperLite is one of the most popular backpacking stoves in America. It is an excellent design in that it is easily serviced in the field should the need arise, although mechanically challenged types will find it more intimidating to operate than a butane “canister” stove. As do most stoves in the superb MSR line, it uses a remote (separate) fuel bottle as the stove’s fuel tank. The stove itself weighs 13.1 ounces; an empty 11-ounce fuel bottle weighs 2.8 ounces. The stove also features a separate windscreen and an optional base. Trying to compare apples to apples here, I used the stove with no windscreen or base, for a combined weight (stove and empty fuel bottle) of 15.9 ounces.



Trangia Notes:



The Trangia is a simple brass burner similar to those found under your Aunt Averna’s fondue set or chafing dish--with one important difference. Around the central (large) hole in the burner assembly, a threaded collar arises with two dozen 1mm (0.040-inch) holes around the perimeter. As the stove warms, the fuel in the collar vaporizes, partially pressurizes, jets through these holes and spontaneously ignites, improving the stove’s performance to some degree. The Westwind burner and base together weigh 6.8 ounces.



Svea 123R Notes:



I purchased my venerable Svea 123R white-gas backpacking stove 29 years ago. It incorporates tank, burner, and windshield into one assembly. It’s solid brass, relatively heavy, and way old tech, but in terms of packaged convenience it lies directly between the MSR and the Trangia, which is why I included it. It’s also hideously loud, but utterly reliable--I once cooked 62 days straight with it in the field, and have had it as high as 14,500 feet and in temperatures as low as -14 degrees F. Though still commercially available, I would hardly recommend it to anyone today as a new-stove purchase, but I am still fond of it, and it does still work--quite well, as the numbers show. Weight (no fuel): 17.5 ounces.



Canteen-Cup Burner Notes:



This is the current GI setup (included for the amusement and edification of Mr. Qualls and Mr. Hay). The standard 1-quart GI canteen fits into a steel cup, which in turn fits into a cup-holder/stand, and the whole shebang fits into a GI canteen pouch. In use, the cup is placed on the (inverted) stand, and a Trioxane solid-fuel block is inserted under the cup/in the stand and ignited. Weight for cup, stand, and one Trioxane solid-fuel bar (an entire bar was used to heat the water): 11.5 ounces.



Boil Times (in minutes and seconds; see “conditions” note for ambient temperature, altitude, etc.):



MSR WhisperLite: 2:20

Svea 123R: 4:15

Wedgewood Range: 5:50

Canteen-Cup/Burner: 9:00

Trangia: 14:00



Note that the water in the canteen-cup stove never reached a true rolling boil, but did achieve a “mild” boil.



In terms of performance and efficiency, the above numbers pretty clearly reflect the qualities of a stove and fuel combination. But there is more to consider. The MSR takes considerably longer to set up and preheat than the simple Trangia; the Svea is somewhere in between. So here’s another set of numbers, this time recording how long it took to assemble the stove, pre-heat it (as required) and boil the same amount of water under the same conditions.



Wedgewood Range: 5:50 (including 0:00 setup and preheat)

MSR WhisperLite: 6:02 (including 3:42 setup and preheat)

Svea 123R: 6:55 (including 2:40 setup and preheat)

Canteen-Cup/Burner: 10:50 (including 1:50 setup and preheat)

Trangia: 15:00 (including 1:00 setup and preheat)



Please review these numbers for what they are. At altitude, or in cold weather, the pressure-fed gasoline stoves will perform in a superior manner. Conversely, the Trangia is simpler and more compact than even the simplest canister gas (propane, butane) stoves. White gas can be difficult to find in other countries, although the MSR will burn just about any flammable liquid. Alcohol is universally available, and the airlines won’t have a hemorrhage if you try to transport it. The amount of water is small (500ml is roughly one pint), but this is the maximum capacity of the Trioxane stove’s capabilities and not too far from the limit of the Trangia. The MSR and the Svea, on the other hand, were just getting started at this quantity.



A final note: Cyberspace is full of plans for do-it-yourself alcohol stoves built from nothing more than a pair of aluminum soft-drink cans and using nothing more than a jack knife, a pair of scissors, and a thumbtack for construction materials. As a lark, I whipped up a couple of these, but was disappointed with their performance compared with the Trangia. The upside--they’re virtually free. The downside--check the numbers below.



(Author’s note, February, 2005: In the three and one half years since I originally wrote this post, Forum Member Alan Halcon has done a great deal of experimenting with these small “soda-can” stoves, and I believe he has had much greater success with them than I. He clearly should be looked upon as the authority in this matter. I can only report on my original results, however, which appear below. Still, though, I suspect Mr. Halcon will be able to contribute far more favorable numbers, especially if he is able to pass along some of the tips for their use. Perhaps he will even create another ebook concerning these stoves to match his excellent Hand Drill effort.—ML)





Self-made soda-can aluminum stove (same “conditions” as prior):



Weight: 0.4 ounce

Boil Time: N/A--water heated to 170 degrees after 15:00

Construction Time: 15-20 minutes



In an emergency (read that as your regular stove pukes blood), you could easily fabricate one if you had the pop cans, but you’d need the alcohol too.



Certainly many members of this Forum will prefer to light a campfire with flint and steel and boil their water in a coffee can next to that fire, as I have so many times myself. But when you’re above the treeline, at a picnic table, or simply don’t want to light a fire for legal, ecologic, aesthetic or other reasons, you should know where the strengths and weaknesses of these stoves lie. To go high above the treeline into the snowpack with anything less than a pressurized stove is deficient thinking.



At some point in the conversation, I need to mention that spilled gasoline is extremely dangerous, as well as nasty to clean up. Also dangerous, as mentioned in a previous post, is the fact that alcohol burns with a near-invisible flame in daylight. Finally, all of these combustion devices product carbon monoxide, an odorless gas that kills insidiously--adequate ventilation must be insured under all circumstances.



Well, I’ve used up enough bandwidth for today. So now, if you don’t mind, I’m going to have a cup of tea--about 500ml heated to 212 degrees F, to be exact.



Best regards,



--ML





More Stove Experiments



Still up sleepless at nights, plagued by nagging stove questions? Here are a couple of more variables to consider while watching that pot boil.



I decided to investigate the effects of two common variables, namely water temperature and pot color (light vs. dark). Both results were surprises.



The conditions again, first for the water-temperature variable.



Air Temperature: 78 degrees F

Water Quantity: 500ml

Elevation: 770 feet MSL

Barometer: 29.05 in. Hg

Stove: MSR WhisperLite Internationale burning white gas

Pot: 750ml MSR Stowaway model with lid.



Note that in the previous testing, this stove had proven to be the most efficient.



Time to boil (minutes and seconds) starting with water at



72 degrees F 2:20

34 degrees F 3:21



Water doesn’t get much colder than 34 degrees (another two points on the thermometer and it turns to ice). Still, I was very much surprised by the large increase in boiling time for such a small amount of water. With greater amounts of water the difference will be even more dramatic.



Next, for Mr. Montabasco’s enlightenment as well as my own, I decided to see how much difference pot color made on the time-to-boil test. Going into this, I thought that a soot-blackened or dark-colored pot would make a big difference and lower boil times significantly.



I was lucky enough to have two identical 2-liter stainless-steel pots (from an MSR Cascade cookset), one new and one older. The new one has a polished, shiny bottom, theoretically the worst scenario as it should reflect heat away. The second pot was sanded with 440-grit abrasive paper and painted on the bottom and one inch up its sides with VHT (Very High Temperature) flat-black paint. Both pots were filled with 500ml of water under the same “conditions” listed above. Here are the numbers.



Time to boil (minutes and seconds)

Silver pot 2:32

Blackened pot 2:28



This is virtually no difference, and well within the margin of error of my observations.



Also please note that the boil times for the silver pot are gratifyingly close to the smaller 750ml Stowaway pot. Pot shape and size appears to make more difference on a small stove like this than pot color.



Finally, a few other facts to chew on. We all know water boils at lower temperatures (read sooner) at higher altitudes, although stoves burn less efficiently at altitude as well. It’s been my experience that boiling times at altitude generally increase as stove inefficiency outweighs the lowered boiling temperatures. Indeed, at 14,500 feet, I’ve found it difficult to light my pressurized white-gas stoves with a metal match, although a conventional match (open flame) does the job nicely. For those interested, here’s a chart of boiling temperatures at altitude:



Sea level 212 degrees F

2000 feet 208 degrees F

5000 feet 203 degrees F

7500 feet 198 degrees F

10,000 feet 194 degrees F

15,000 feet 185 degrees F

30,000 feet 158 degrees F



Here too is a breakdown of (approximate) atmospheric pressures at altitude:



Sea level 14.7 psi

5000 feet 12.5 psi

18,000 feet 7.35 psi



(Author’s note, February, 2005: An excellent rule of thumb to apply is that one loses approximately 3 percent of sea-level atmospheric pressure with each 1000 feet of elevation gain. This is not an absolute, but it is close, especially for altitudes below 1000 feet. –ML)



Best regards,



--ML



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