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  1. #1
    Registered User Mr Liberty's Avatar
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    Question Iso-Alcohol Stove

    I've been playing around with making a soda can stove that burns 91% isopropyl alcohol, and after a few iterations I came up with a version that burns cleanly, albeit not very efficiently. I took a cue from Zelph's doodah-man special/ring-of-fire stove and used a fiberglass wick around the outside, and it burns cleanly when it has a pot over it. The construction is idiot-simple, just cut two cans (one smaller than the other) and drill a hole in the base of the smaller one. You pour the fuel down the middle, through the hole (after "wetting" the wick, if necessary). You can see in the second picture that I also cut some triangular slits in the bottom of the smaller can, to let the fuel seep out to the outside of the larger can. Then it's drawn up by the wick, and burns just above the stove. It weighs between 8 and 9 grams, my scale can't decide

    Do you have any suggestions that would make this more efficient? It couldn't boil a cup of cool water with 3tsp (15mL) of fuel, although I don't have a very good pot so I just used a little metal bowl I got from the thrift store for a dollar . I bet a fancy titanium pot would boil quicker...



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    What is the advantage of using isopropyl?
    In the end, it's not the years in your life that count. It's the life in your years. - Abraham Lincoln

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    Registered User Siestita's Avatar
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    Before I learned to do better with yellow Heet or paint thinner alcohol such as SLX, I experimented instead with burning 91% isopropyl. Isopropyl's only 'advantage' was being convenient to purchase, being available at pharmacies and supermarkets. But, besides not being a very efficient fuel to use, isopropyl is, in my experience, an incredibly sooty fuel. So, I'm skeptical that anyone can make that stuff consistently burn both cleanly and efficiently.

    "...It couldn't boil a cup of cool water with 3tsp (15mL) of fuel, although I don't have a very good pot so I just used a little metal bowl I got from the thrift store for a dollar . I bet a fancy titanium pot would boil quicker..."

    Don't count on '"fancy titanium pots" heating water any more efficiently than do cheap ones acquired at thrift stores or elsewhere. Apparently aluminum pots conduct heat more efficiently than do 'titanium' ones of comparable weight. Titanium pots are reportedly actually made from titanium/aluminum alloys. Their claim to fame is possession of greater strength. But it's not clear to me that extra cook pot strength is necessary, or even particularly advantageous, to have. Cheap light weight aluminum pots are often strong enough to endure for decades, frequently lasting longer often than their owners live.

    Wind protection, use of a lid, distance between pot and stove flame, and a pot's size may affect stove efficiency more than do a pot's cost or its 'fanciness'. The more empty space (air that absorbs heat) that the interior of a pot has, the longer it takes to heat water.

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    It's not only that you have only 91% fuel, but also that other 9% is water, basically the water is working as a anti-fuel' as it takes energy (fuel) to 1:heat up and 2:vaporize that water, that's less heat that can be transferred to the pot. When water goes from liquid to gas it takes (quite a bit of) energy, yet the temperature of the water does not increase during this phase change, the energy goes totally into phase change. The net effect is that the flame is of lower temperature due to the heat of the products of combustion going to heat up water before it hits the pot and that phase change energy which cools the flame and does not raise the temperature of anything.

    It's been a while since I made those sort of calculations but it may not be possible to get a reasonably efficient burn, but getting a clean burn seems to be a step to increase efficiency and practicality of using such fuel.



    It's been a while since I did such calculations

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    Did a down and dirty experiment (had some free time this AM) of 100% Heet fuel vs 90% Heet fuel mixed with 10% water (simulating the OP's 91% iso fuel). My measurements of the fuel are a bit rough due to the very small quantities.

    Caldara cone, 12:10 stove, MSR titan kettle, 500 ml of water, tap water start (unable to measure that temp):

    Control:
    9g of Fuel 100% HEET (9g):
    Burn time 5:23, final water temp = 163F

    Experiment:
    10 g Fuel 90% HEET (9g), 10% Water (1g)
    Burn time 6:18s, final Water Temp = 158F
    Other: Sizzle sound noticed throughout burn - louder towards end of burn, orange flame parts of fire, seemed to grow more orange as it progressed.

    Conclusion: Both fuels have the same amount of energy, both contained 9g of HEET. What was noticed is that the fuel that had water added burned for a 15% longer time (6m13s vs 5m23s ), but also burned partly orange which indicates perhaps inefficient burning. The pure fuel did reach a higher final temperature of the water (163F vs. 158F).

    Speculation: The slower burning time of the diluted fuel may have helped efficiency as is commonly noticed that slower stoves are a more efficient method of heating water, however this gain of efficiency due to a slower boil is offset by the loss of efficiency due to the water in the fuel. A modified 12:10 stove tuned to burn the 90:10 fuel in apx the same time as the standard 12:10 stove should have produced a lower final water temperature then the 158F for the fuel mix.
    Last edited by Starchild; 05-14-2015 at 10:18.

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    Quote Originally Posted by BirdBrain View Post
    What is the advantage of using isopropyl?
    My question is genuine. It was intended to gain perspective. I believe that the best way is often missed because it is dismissed because of what we think we know. I think I know why isopropyl is a bad fuel choice. In this case it would be just noise to list what I know. I seek knowledge. Many people try to build a functional and efficient isopropyl stove. I know why I use other fuels. Honestly, why build a stove for isopropyl? I am not being sarcastic.
    In the end, it's not the years in your life that count. It's the life in your years. - Abraham Lincoln

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    Registered User Mr Liberty's Avatar
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    Quote Originally Posted by BirdBrain View Post
    My question is genuine. It was intended to gain perspective. I believe that the best way is often missed because it is dismissed because of what we think we know. I think I know why isopropyl is a bad fuel choice. In this case it would be just noise to list what I know. I seek knowledge. Many people try to build a functional and efficient isopropyl stove. I know why I use other fuels. Honestly, why build a stove for isopropyl? I am not being sarcastic.
    Isopropyl/Rubbing Alcohol is infinitely easier to find than other alcohol fuels (I don't think I've ever even seen HEET or esbit before, though I've never looked for it specifically) and it's also very cheap ($3/liter at Walmart, IIRC). I also happen to already have it at my house, so that makes it basically free to play with, for a little while.
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    Quote Originally Posted by Mr Liberty View Post
    Isopropyl/Rubbing Alcohol is infinitely easier to find than other alcohol fuels (I don't think I've ever even seen HEET or esbit before, though I've never looked for it specifically) and it's also very cheap ($3/liter at Walmart, IIRC). I also happen to already have it at my house, so that makes it basically free to play with, for a little while.
    Particularly in northern latitudes like Illinois, you should be able to find yellow HEET quite easily in the automotive section of Walmart. Also Walmart usually stocks KleenStrip denatured alcohol, either in the fishing section as it's marketed as boat alcohol stove fuel, or in the paint department where denatured alcohol is generally sold as well. Esbit is readily available at almost any store that carries hiking gear, and Esbit or similar solid fuels (Coglans brand) are also stocked at many other stores in the camping aisle.
    Last edited by 4eyedbuzzard; 05-14-2015 at 18:01.
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    Registered User Mr Liberty's Avatar
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    Quote Originally Posted by 4eyedbuzzard View Post
    Particularly in northern latitudes like Illinois, you should be able to find yellow HEET quite easily in the automotive section of Walmart. Also Walmart usually stocks KleenStrip denatured alcohol, either in the fishing section as it's marketed as boat alcohol stove fuel, or in the paint department where denatured alcohol is generally sold as well. Esbit is readily available at almost any store that carries hiking gear, and Esbit or similar solid fuels (Coglans brand) are also stocked at many other stores in the camping aisle.
    Thanks for the info, I was sure it was around, but I've never looked for it. (My point was more that you can get isopropyl at any dinky town in the middle of nowhere, but only larger towns will probably have a walmart or outdoors/auto store where you can get other fuels... and iso is cheaper too, I believe).

    On a tangent: what's the difference between red and yellow HEET? I've seen it argued about before but I never paid attention.
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    Registered User 4eyedbuzzard's Avatar
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    Different alcohol chemistry. Yellow HEET is methanol (methyl alcohol), Red HEET is Isopropyl, denatured alcohol is typically Ethanol (ethyl alcohol, aka booze) with methyl alcohol added to poison it so that people can't drink it (think tax revenues). http://www.brainstuffshow.com/blog/g...ropyl-alcohol/
    Last edited by 4eyedbuzzard; 05-14-2015 at 18:35.
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    Add more fiberglass wrappings if you can to slow down the burn. Have a smooth seam edge sticking up at the top rim of the pot support. Have it even with the pot support, not sticking above it. Try it and see if you can get a boil with 17ml of fuel.

    How do you like the smell of burning Iso?

    Stove design is a great hobby :-)

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    I have had no trouble finding Heet, even when we lived in FL.

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    In the more northern latitudes, you can find HEET at just about any truck stop or gas station, and denatured alcohol at any hardware store, lumberyard, paint store, big box, and so on.

    Not to mention that a lot of hostels will sell it to you, particularly if the hostel is in a place where there are none of the above.
    I always know where I am. I'm right here.

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    Quote Originally Posted by zelph View Post
    Add more fiberglass wrappings if you can to slow down the burn. Have a smooth seam edge sticking up at the top rim of the pot support. Have it even with the pot support, not sticking above it. Try it and see if you can get a boil with 17ml of fuel.

    How do you like the smell of burning Iso?

    Stove design is a great hobby :-)
    Thanks for the tips! I'll try some out tonight or tomorrow, if I have time.

    Question: what do you mean by "Have a smooth seam edge sticking up at the top rim of the pot support"? Also, if more fiberglass slows the burn, wouldn't that make it burn less hotly? Or would it just make the heat last longer?

    If 17mL is the goal, I'll see what I can do . Burning iso doesn't smell that bad, I just make sure to have good ventilation if I'm burning more than 5mL at a time. And I agree, stovemaking is addictive! I think I made/attempted to make 4 in my first 2 days
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    Registered User Mr Liberty's Avatar
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    So I made some modifications and did a boil test. Here's the results, 1TBsp (~15mL) of 91% isopropyl each and water starting at about 75 degrees F:

    Trial 1: add more wraps of fiberglass (full 4ft)
    -burned about the same as before, barely heated water, "jets" kept going out, not much heat output.
    Picture:

    The weight stayed the same, 8g.

    Trial 2: kept extra wraps of fiberglass from Trial 1, added a little pot stand to put more distance between the pot and the stove.

    Holy cow! This made a world of difference!
    Picture. Windscreen just some aluminum foil.


    It did get a boil in about 8 and a half minutes. However...

    After a few minutes, it started to get yellow:

    And once the water hit about 180 degrees F, it started to really get yellow:

    And yellow flames = soot




    Why did it suddenly become so not-clean at the end? It burned cleanly for at least the first half of the time.
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    Reduce the width of your original pot supports to 1/4 wide. They will probably melt but you'll see a difference and should remain clean burning.

    Switch to steel outer can to prevent melting of pot supports.

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    The water was the only thing left at the end of your burn cycle. (Remember the 91 percent? 9%=water)
    One of the gurus advocates removing your pot and shutting it off as it starts to turn yellow. This will cut down on soot also. Smear dawn dish wash soap on bottom of pot before burn to make clean up easier. Experiment with diff size slits/jets to vary fuel ratio.

    stay with it. Knowledge is power. I too like having the option of getting fuel in more places. Even if slightly more inefficient.

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    Oh yeah, pot bottom should just cover the spread flame pattern. Too large pattern let's heat go up sides of pot. Too small creates hot spot and inefficient heat transfer. Vary height of pot support and bottom of pot size. Wide flat with rounded corners on bottom to sides is best. Aluminum is better than titanium actually for heat transfer.

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    Quote Originally Posted by Rolex View Post
    The water was the only thing left at the end of your burn cycle. (Remember the 91 percent? 9%=water)
    ....
    That's what happened in my experiment posted above with diluted HEET (water added) also, orange flames were noted and increasingly were 'more' orange towards the end.

    You just may have to use a bit more fuel knowing that last part would be undesirable to burn and blow it out before the soot starts. Also don't reuse that last part of the fuel, it is sure to be much less then 91% at that point, much more water.

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    I was wondering if you have tried 99% ISO ? I can get it from the pharmacy.

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