How can I make my alcohol stove more effecient?

[The Will]

I'm very pleased with everything about my home made alcohol stove with one exception. The top of the flames are approximately 7 inches high (from flame tip to stove top). This results in the flames "licking" up the sides of my cup rather than being concentrated on the under side. My boil times are generally 6:30 minutes for 9-10oz of water--this seems slow compared to other posts/reviews I have read, and I'm certain this is due to all the heat loss from the top of the flames doing no "heating work" what-so-ever.

Any suggestions?


The stove is a standard pop can stove, made from Red Bull cans (small). Burner holes were made with a plastic headed push-pen and they are spaced 2mm apart all around the circumference of the top of the stove.



The Will
MEGA '97

[jlb2012]

I had similar problems with the beer can "pot" that I use and finally I tried something that seems to work OK - the aluminum bottom to a tea candle - very light and it holds just enough alcohol to boil 1.75 cups of water which is what I generally use for my meals. The only adjustments to be done are to take the candle out - nothing else needs to be done. Note the time to boil will still be longish (7-8 minutes) but the flames generally stay under the pot and I don't use as much alcohol as when I was using an Ion stove for the pot.

Another possibility is to change the pot to one with a wider base - spreads the flames out more for faster boiling.

[SGT Rock]

What is your pot to stove distance?

[The Will]

The pot to stove distance is within 4-5cm.

I considered using a taller pot support in an effort to remedy the problem, but isn't that 7 or so inch flame height a bit out of the ordinary? Don't alcohol stoves usually exhibit a short, simmer-like flame? (It's is the same problem whether I burn Heet or denatured alcohol).

Thanks.



The Will
MEGA '97

[SGT Rock]

Depending on the stove and how much fuel it allows to burn, the height of an exposed flame (one without a pot in the way) could be up to 12" and bright yellow in my experience. The interaction between the pot and the stove can choke the stove. I was going to suggest that you try reducing the pot height down to abou 1/2"-3/4" (about 1-1/2 to 2cm). See if that helps control the flame.

[Miss Janet]

Try making a closed design stove that you can sit your pot on and eliminate a pot stand. My Kiss stove... Keep it simple, stupid ... has been working very well and a lot of hikers are using it this year.

[art to linda]

Where can I find the plans for your stove? I'm looking at different types and the simpler the better, "KISS stove" sounds interesting.

[SGT Rock]

I've got a stove design like that on my site: http://hikinghq.net/sgt_stove/sgt_v8...tructions.html

I haven't run a test on this model yet to compare fuel efficiency.

[anneandbenhike]

You are describing what the engineers call "Thermal Overload" which basically means that the rate of heat transfer to the stove itself (heating and there-by vaporizing alcohol) is too efficient. Try decreasing the amount of air reaching the flame at the stove, reducing the size of the flame holes (punch-hole making with a smaller needle) or similar moves--there are some great links on the web.

[David S.]

Today I thought I would try out the tea candle stove...those little candles that have the aluminum base. I took the wax out of the base and filled the base with alchohol. The base holds almost exactly 1/2 an once. I have been struggling with the same problem of flames licking up the side of my pot.
I was very impressed with the results. No flames up the side of the pot but a nice even concentrated flame in the middle. I didn't time the boil but it brought 2 cups of cold water to a boil and held it at a boil for a good 20 seconds or so. Thats with only a half ounce of fuel....efficiency I was not able to achieve with my little V-8 stove. I was pretty impressed. This little thing appears to work embarrassingly well...and it won't even register on my postal scale so I am content to say that it weighs nothing. After all the work I have put into making various other soda can stoves, this little thing appears to do the job quite gracefully...just letting the alchohol sit there and burn. Nothing fancy. Try it. Attatched is a pic of the little thing at work.

[Footslogger]

Today I thought I would try out the tea candle stove...those little candles that have the aluminum base. I took the wax out of the base and filled the base with alchohol. The base holds almost exactly 1/2 an once. I have been struggling with the same problem of flames licking up the side of my pot.
I was very impressed with the results. No flames up the side of the pot but a nice even concentrated flame in the middle. I didn't time the boil but it brought 2 cups of cold water to a boil and held it at a boil for a good 20 seconds or so. Thats with only a half ounce of fuel....efficiency I was not able to achieve with my little V-8 stove. I was pretty impressed. This little thing appears to work embarrassingly well...and it won't even register on my postal scale so I am content to say that it weighs nothing. After all the work I have put into making various other soda can stoves, this little thing appears to do the job quite gracefully...just letting the alchohol sit there and burn. Nothing fancy. Try it. Attatched is a pic of the little thing at work.

=============================
I'm guessing that your experiment was performed inside and without any wind, and thus no wind screen. Just wondering how well the Tea Candle stove would perform outside in cold temperatures, with moderate to high winds and with water in the 40 degree range.
===========================

[SGT Rock]

I made one of those, I really didn't like the performance in field conditions. You don't have the ability to increase the volume of fuel in colder or windy conditions since the total volume available is only 1/2 ounce - add to that the fact that if your stove is on a slight angle, then you loose some ofthat 1/2 ounce. I also found that although it did get bubbles forming and moving to the top, the real temperature achive when measured with a thermocouple was not 212 degrees, more like 190-200. Anyway, it does good at heating water, but not great.

[David S.]

Good point Footslogger. In my enthusiasm about my indoor results, I didn't think about how outdoor conditions would effect things. Time to take it to the back deck and try it. I'll also try it with some 40 degree water. I don't think it will do nearly as well. For the weight though, you could bring it along for those warmer windless days and save some fuel. Use the V-8 type stove for windy, colder conditions.
Sgt Rock you make good points....sigh...off to the drawing board again. Theres gotta be an optimum stove just for my pot. I thought about making a pepsi can style alcohol stove except with the fire holes on the inside top of the inner wall so the flames point inward rather than outward and hopefully focus the flame more on the bottem of the pot. What I think is happening is the alcohol is vaporizing to fast and making a flame much bigger than my stove needs.

[SGT Rock]

My general guidlines for a good stove:

-1 ounce capacity just in case.

-stable enought to hold a pot up even when on a slightly uneven surface.

-flame concentrated to the center of the pot whenever possible. The flames should not shoot up the sides of the pot since this is wasted energy.

-the flame should be blue, with the ends just turning yellow. This is achived for each different stove by adjusting pot heght.

-any stove should be able to achive a rolling boil consistantly with a pint of water in almost any condition with 3/4 ounce alcohol. It should be able to achive a roiling boil unconditionally with 1 ounce fuel. 1/2 ounce alcohol is a best situation fuel consumption and for some tasks like making some hot water it should be sufficient.

[Dances with Mice]

I thought about making a pepsi can style alcohol stove except with the fire holes on the inside top of the inner wall so the flames point inward rather than outward and hopefully focus the flame more on the bottem of the pot. What I think is happening is the alcohol is vaporizing to fast and making a flame much bigger than my stove needs.

The miniature cat burner, construction steps show in my gallery, keeps the flames focused in the middle of the burner. Getting it centered under the pot, of course, is your responsibility. Weighs 0.4 oz. http://www.whiteblaze.net/gallery/sh...cat/500/page/2

There is also a very stable, one piece, combination windscreen and potholder that goes along with the burner to complete the stove. I just finished constructing another one tonight and I'll try to post the photos tomorrow after I edit them a bit. I also want to take the windscreen/potholder to work and weigh it.

[jlb2012]

Today I thought I would try out the tea candle stove...those little candles that have the aluminum base. I took the wax out of the base and filled the base with alchohol. The base holds almost exactly 1/2 an once. I have been struggling with the same problem of flames licking up the side of my pot.
I was very impressed with the results. No flames up the side of the pot but a nice even concentrated flame in the middle. I didn't time the boil but it brought 2 cups of cold water to a boil and held it at a boil for a good 20 seconds or so. Thats with only a half ounce of fuel....efficiency I was not able to achieve with my little V-8 stove. I was pretty impressed. This little thing appears to work embarrassingly well...and it won't even register on my postal scale so I am content to say that it weighs nothing. After all the work I have put into making various other soda can stoves, this little thing appears to do the job quite gracefully...just letting the alchohol sit there and burn. Nothing fancy. Try it. Attatched is a pic of the little thing at work.

I've been using this approach for the last year or so with my beer can pot - it's the only approach that minimizes the flames up the side of the pot problem I was having with the other burners. With respect to boiling 2 cups of water - for the most part I don't try - I boil 1.75 cups of water which is enough for most of my meals (typically Liptons noodle or rice dinners). In the colder weather I sometimes don't get a full rolling boil but in those cases I just put in a little more alcohol and light it again after it goes out the first time. One nice thing about this approach is that once the water is boiling you can blow out the tea candle burner and pour the excess alcohol back into the fuel bottle. This is why I no longer put any fiberglass into the tea candle cup - so I can pour the excess back into the bottle. Other notes - beer can pot is a Heineken 24 ounce minikeg - ridges help it hold its shape and make it easier to pickup. The actual cooking is done in a zip lock bag in a cozy - the beer can is only there for boiling the water.

In general it is not as fast as some stoves but it works well enough for me.

[peter_pan]

Try making one of Atlanta Randy's ( Sgt Rock's site) Potted meat can Stoves.....they are super...no moving parts....cost $0.20 for the can. ....can be made in less than 5 minutes with nothing but a push pin.... I use an old alum BSA mess kit pot with the handle removed...capacity 0.8 qt....put the pot on the can....instant pressure...great blue flame....Boils two full cups - 16 oz- in 4 minutes...on 0.5 oz of alcohlol...The stove complete is 00000.33 oz.....yes 9-10 grams as close as I can measure.

Wgt 1/3 of a sode can stove
cost less than 12 of a soda can stove
pressurized. Not all soda stoves are
no moving parts, most pressure soda cans have a screw
no pot stand needed
replacable in any trail town with out tools ( borrow push pin off the employee BB)
uses less alcohol
fits in any pot and most all cups for storage
boils 16 oz water in 4 minutes
PS.....You can eat the meat first

[David S.]

On the flames licking up the side of the pot. I have noticed that when I remove the windscreen, the flames do a better job of staying centered under the pot. I overheard a firefighter saying that fire will gravitate to where the oxygen is. I think that may be what is happening under my pot. Maybe I need more air holes around the bottem of the windscreen and maybe more open space around the edge of the pot.

[Dances with Mice]

On the flames licking up the side of the pot. I have noticed that when I remove the windscreen, the flames do a better job of staying centered under the pot. I overheard a firefighter saying that fire will gravitate to where the oxygen is. I think that may be what is happening under my pot. Maybe I need more air holes around the bottem of the windscreen and maybe more open space around the edge of the pot.

Yeah! David, you just did what many scientists I work with can't - you observed an effect and postulated not one but two hypotheses! That's outstanding, and I am not being at all saracastic. Good job.

From my observations - if the stove is starved of oxygen you'll get "Blumps". That's a word I invented, it means a series of small explosions. If the stove doesn't have enough air then it will give off unburned alcohol vapors. When they mix with air and reach some critical level the stove will go "BLUMP! pause BLUMP! pause BAH LUMP!" as the vapors ignite.That means you don't have enough airholes in your windscreen, it could also mean the open space around the pot is too small and vapors are backing up since they can't escape.

If the flames rise above the pot it means your stove is burning welll and your pot is too low.

[Dances with Mice]

There is also a very stable, one piece, combination windscreen and potholder that goes along with the burner to complete the stove. I just finished constructing another one tonight and I'll try to post the photos tomorrow after I edit them a bit. I also want to take the windscreen/potholder to work and weigh it.

http://www.whiteblaze.net/gallery/sh...cat/500/page/1