DIY Alcohol Stove Users!!
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Addison Page
(Nihilist_Voyager) - F

Locale: Down the Rabbit Hole!
DIY Alcohol Stove Users!! on 11/10/2011 10:03:47 MST Print View

Sounded important didn't it?

It's not, just wondering, how long can your stove run on 1 ounce of Alcohol?

I'd prefer to hear from the MYOGer's, but if ya got a cottage industries one you wanna share go right on ahead.

My best stove runs for 10 minutes on one ounce. That's the best I can get although I feel it's average at best. I didn't even make it on purpose. I poked a hole in it with pliers that I figured would ruin it, said screw it I'll finish it and set it on fire anyway, poked like 18 unevenly spaced/shaped/sized punctures into it, set it up, and it blew all my penny designs out of the water (it's an open top design, single can, where you take the whole top of the coke can lid off).

I even remade a cleaner version of the same design but it still didn't work as well as my FUBAR can. Explanations?!?

(The image insert button isn't working for me, I'll post pics of my design when I can)

But what I really posted this thread for was to know your 1 ounce of fuel run times. (Fair weather)

Harald Hope
(hhope) - M

Locale: East Bay
2/3 ounce on 11/10/2011 11:27:29 MST Print View

With a modified penny stove (for narrow pot), 12oz can size, 5 jets pointed in, 1 out towards rim, using a bent bottle cap to prime it, which also heats the pot/water), 2/3 oz runs around 7 or 8 minutes. That will bring 2.5 cups of water to a boil, maybe 3.

I never tested with 1 oz because it wasn't needed, got tired of buying quarts of alcohol.

That's with a real windscreen, about 3/8" clearance between pot and screen.

Fuel is kleanstrip green, which is about 90+% ethanol.

If it's really important to you I'll do a test burn with an oz of fuel to see how long it burns.

That's not using a simmer ring, which cuts air to flames, just regular.

By the way, when I was testing this, I found a huge variance in actual quantity using normal tblspn measuring spoons, I found a plastic cylinder that was narrow enough to serve as an accurate gauge, then I scored it for 1/2 and 1 tbspn, so my measurements are fairly accurate.

Edited by hhope on 11/10/2011 11:30:47 MST.

Addison Page
(Nihilist_Voyager) - F

Locale: Down the Rabbit Hole!
Re: 2/3 ounce on 11/10/2011 12:35:09 MST Print View

That definitely helps. It means I'm still a bit under average but getting there. If 2/3 gets you 7-8 min, then an ounce should bring ya up to 10-12 minute range, which is more or less where I'm at. I got 600mL of water to a roll for about 30 seconds (also using a windscreen with bad airflow) which ain't too shabby I guess, especially for a stove I figured was just going to explode. Now if only I could replicate the darn thing!

Edit: Windscreen to Pot stand. No literal windscreen, but the pot stand serves the purpose

Haha! And just learned that 1 cup is 250mL. So pretty much you're running about 33% more efficiently then me in general. Using a third less fuel and boiling about a third more water. Stop that!

Edited by Nihilist_Voyager on 11/10/2011 12:59:03 MST.

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

Locale: Silicon Valley
Re: Re: 2/3 ounce on 11/10/2011 13:03:16 MST Print View

Addison, for most alcohol stoves, some of the windscreen factors are critical. No joke.

Even if you don't have any real wind, the windscreen helps retain heat around the cook pot. Some of that reflects back down to warm the alcohol. Too much or too little doesn't work so good. However, the windscreen still needs to admit cold air in at the bottom, and if there isn't enough draft, then it doesn't work so good. Too much draft and all of the heat ends up warming up the air and not the pot. The pot height above the flame is critical, as is the diameter of the pot.

That's why a lot of real stovies do lots and lots of burn tests until they can see exactly which factors get it done perfectly. Then, simply change the water temperature or air temperature or something else, and the perfect solution is not so perfect anymore. But, the real stovies understand all of those variable factors, and they know how many milliliters will get them how many minutes of flame to boil how much water. Sometimes putting a piece of aluminum foil on the ground underneath the alcohol burner will help a lot. It helps insulate the alcohol from cold ground temperatures.

--B.G.--

Harald Hope
(hhope) - M

Locale: East Bay
lots of testing on 11/10/2011 13:29:28 MST Print View

addison, it took a lot of testing and a few prototypes to get to this point.

And as Bob notes, heat/wind screen is critical part of it, especially with narrow pots. With wind, you have to stick the stove/wind screen behind something to block the wind otherwise the turbulence really messes with the cooking times and speeds.

Note that if I had a 1.3 liter or 0.9 liter evernew wide pot, I'd be getting better efficiency, but I think I did ok with snowpeak narrow pot, about 700 ml or so, not sure.

The real penny stoves, by the way, use the top of a can to form a base, which then creates a small insulating layer of air to help keep the alcohol warm. I never tried using aluminum foil on the ground, but that would probably also boost efficiency a bit.

By the way, the priming solution for penny stoves found online, creating a base with slots / spaces cut in it, to pour alcohol in, is a very bad idea since you are removing the insulating layer. I was able to easily see this problem at normal temperatures with one of my less successful prototypes, that already didn't burn hot enough.

A few other things, don't punch a half circle of small holes around the bottom for air, cut one large rectangle, 1x1.5 inches or so, that way you can point the air hole away from wind. Then you can even make an aluminum tunnel of sorts for that, though I didn't find that did much when compared to wind blowing over the top of it. This air opening needs to be under the slot you make for the pot handles, if you have handles.

Don't know if it matters, but I'm using a 3 leg bicycle spoke pot stand, which gets very hot as well, sometimes red hot, and probably helps a bit transferring even more heat to the pot.

I also got tired of making different sized heat / wind screens to test different diameters so I just drilled 3 holes top and 3 bottom and use wing nuts to pick the ideal diameter for the pot. That works fine, and also make it very solid when i put it together, and it rolls up and fits in the pot, sticking out of the top, then I just put the lid over it and put it in the snowpeak stuff bag, just fits with cozy.

Edited by hhope on 11/10/2011 13:34:33 MST.

Ultra Magnus
(Ultra_Magnus) - F
Re: DIY Alcohol Stove Users!! on 11/10/2011 16:02:42 MST Print View

As a recovering alky addict I've built probably at least 100 stoves over the period of a few months and have built stoves that burn from anywhere around 5 mins to 25mins on 1oz of fuel. I've found in all of my testing that low and slow is usually the most efficient. High flames get faster boil times, but more heat is lost up the sides of the pot also. Low flames allow more of the heat to be absorbed into the pot.

BM

Ozzy McKinney
(PorcupinePhobia) - F

Locale: PNW
Confirmation! on 11/10/2011 21:11:40 MST Print View

I had the exact same experience! Made a few tricky stoves, then made a lazy low pressure side burner (read: poked a few holes in it) and it performed better than the others. Glad to see I'm not the only one who thinks these are... overengineered :P

Addison Page
(Nihilist_Voyager) - F

Locale: Down the Rabbit Hole!
Thanks everyone. on 11/11/2011 07:34:44 MST Print View

Don't get me wrong these aren't my first designs, I've been drinking 12pks of Mellow Yellow on an almost bi-daily basis to keep the supply of cans coming in for my own experimentation.

Your words really helped, I've been idle for about a week now and after reading these posts I designed two new ones completely differently then the other twenty-odd ones I currently have.

Got an 18min burn time and 7min boil time (2cups) on 1oz of fuel. It's a penny design (so two can bottoms, the cans are pushed into eachother, not slotted together) 1/16th" holes, eight of them around the RING of the can (like if the can was upright, the holes are on the ring that would be physically touching the table, so the flames point upwards).

It seems to work for me, but I'm not done yet. FOR SCIENCE!!

Kevin Beeden
(captain_paranoia) - F

Locale: UK
run time vs heat output on 11/11/2011 09:15:59 MST Print View

> It's not, just wondering, how long can your stove run on 1 ounce of Alcohol?

I assume you want a slow-burning stove for a particular reason: simmering, for instance. Otherwise, if it's just heating water, then fuel efficiency may be a better measure. I measure the latter using a fixed water load (500ml), a fixed fuel load (15ml) and measure the time to boil (jet of steam escaping from lid) and total burn time. The figures go into a spreadsheet that makes a few assumptions about burn rate, and knows the energy content of the fuel, and energy required to boil the water, and spits out an energy transfer efficiency (55-60% is fairly usual). That's the effciency of the entire burner/pan/windshield setup.

The slowest burner I've made was a 'mini-penny' stove, which ran for about 27 minutes on 15ml of fuel. Like all Mark Jurey Penny Stoves I've built (as opposed to a generic penny stove...), it was a pain in the butt to light and get to prime. It also had wild flame variations, with rapid changes in flame size.

Other ways to get long burn times are to reduce the amount of exposed fuel that can burn, so wicking systems with small wicks and enclosed fuel reservoirs, or simply small bottle tops, although these can't hold much fuel.

Thermal feedback within you pan/windshield setup is also a factor; if you get a lot of feedback, more fuel evaporates, and the burner runs hotter. With a limited air supply, you can have too much fuel and incomplete combustion, resulting in sooting, CO production, and poor heat transfer efficiency.

Addison Page
(Nihilist_Voyager) - F

Locale: Down the Rabbit Hole!
Re: run time vs heat output on 11/11/2011 11:27:34 MST Print View

I guess that was pretty poor wording on my part. I am also interested in how fast you can attain a boil and how much water you're boiling.

Especially if you're getting down to the sub 5 minute range (if it's homemade pics would be appreciated but I understand you spent your time getting it right, maybe PM me we'll talk about me buying one or at least the instructions)(if it's cottage made please don't, that ain't fair to them)

Dan Yeruski
(zelph) - MLife

Locale: www.bplite.com
DIY Alcohol Stove Users on 11/12/2011 12:50:07 MST Print View

The famous SuperCat stove is fast to boil 2 cups with 1/2 ounce of fuel using an aluminum pot under ideal conditions.

James Nomura
(Lockon) - F
Re: DIY Alcohol Stove Users!! on 11/15/2011 04:59:00 MST Print View

1 oz using SLX on an Evernew Titanium DX stove stacked is about 7 minutes. (stove burns at full power)

1 oz using SLX on an Evernew Ti stove (stove only, no stand) with a pot sitting directly on top is about 15-16 minutes. (stove power is significantly less)

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Re: DIY Alcohol Stove Users!! on 11/15/2011 07:03:51 MST Print View

After maybe 50-75 different stoves, I pretty much gave up trying for any more efficiency than about 1 ounce per quart (30ml per liter.) With very long boil times (on the order of 13-15 minutes for two cups) it is possible to reduce this slightly. But, the savings are pretty much not worth it. A small cone type burner like one of these and a cladera cone or home made equivalent (sans handle cutouts) runs for about 17-18 minutes on a half ounce of fuel:
Stoves

Basically, they concentrate the flame near the center of the pot. Any wasted heat is recovered by the cone and pot as it slides up the sides. These require a highly tuned system to get better than 1/2oz for two cups. I was able to get this down to 1/3oz by narrowing the second "can" stove opening, and ridging the bottom of a grease pan by a series of 1/2" deep "ripples", but the 17min boil time was getting very slow. In colder weather(much below 50F) I doubted it would ever boil because of the heat loss to the outside air.

Anyway, it seems that boil time and heat loss to the outside air are related. This is beyond what you would also consider normal fuel efficiency. An indicates a need for better windscreen/pot designs that also incorporate some degree of insulation. This also goes a ways in explaining the fuel efficiency of the jetboils, which have some insulating properties in the pot, itself, but do nothing to capture wasted heat from the bottom (though the heat exchanger is also a good idea.)

Edited by jamesdmarco on 11/15/2011 07:23:30 MST.

Kevin Beeden
(captain_paranoia) - F

Locale: UK
re: cone-type burners on 11/23/2011 11:01:50 MST Print View

> A small cone type burner like one of these

Those are interesting burners, James. Both seem to use the principle of reducing the area of exposed burning alcohol I mentioned earlier.

I've tried reducing the exposed area by cutting a small hole in a burner made from two can bases, but if the hole is too small (<24mm diameter), it seems to prevent air getting into the reservoir during priming, and the flame goes out before the burenr gets going properly. I note that the left-hand burner has an air vent (?) in the side that may be to overcome this problem. The ripples in the right-hand one may allow air to get to the flame.

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: re: cone-type burners on 11/23/2011 11:59:27 MST Print View

Yeah, neither are presurizied, which requires priming. As you correctly guessed, the 1/4" holes were to let a self heating flame to occur inside, causing increased vaporization of the fuel. Too many and it flames out the holes, though. Too few and the flame goes out...three works pretty well. The flange on top is a nozzel for mixing air and vapour. There is some degree of countroll, perhaps 7-8 minutes difference between high and low. Both were designed around a base load of a half ounce of unpresurized fuel.

The folded one serves two purposes. It narrows the opening, and allows air (small amounts anyway) into the vapor as some sort of pre-ignition primer. Note that this burns quite cool, there is no burned paint, yet it has been burned 20-30 times. It allows more air to be burned with the fuel than normal since it sort of scavanges air. But, it is wind sensitive. No problem in a caldera cone. Another one has a primer hole which burns a lot hotter and faster. If you make one use rounded pliers, the aluminum is quite brittle around the sharp bends.

Hikin' Jim
(hikin_jim) - MLife

Locale: Orange County, CA, USA
Re: Re: DIY Alcohol Stove Users!! on 11/23/2011 13:37:44 MST Print View

Ultra Magnus said: > As a recovering alky addict I've built probably at least 100 stoves over the period of a few months and have built stoves that burn from anywhere around 5 mins to 25mins on 1oz of fuel. I've found in all of my testing that low and slow is usually the most efficient. [emphasis added] High flames get faster boil times, but more heat is lost up the sides of the pot also. Low flames allow more of the heat to be absorbed into the pot.
That's certainly been my experience (that low and slow is the most efficient).

I see people above commenting about stoves losing too much heat. In weather of about 48F/9C last weekend, I did a bit of experimenting. My experience this past weekend and in general is that most alcohol stoves burn too hot. My current interest is to find ways to limit the thermal feedback so as to get lower flames and greater efficiency.

HJ
Adventures in Stoving

Jon Fong
(jonfong) - F - M

Locale: FLAT CAT GEAR
A good alcohol stove on 11/23/2011 14:00:55 MST Print View

A well designed alcohol stove should be able to boil two cups of 70 F water using 15 ml of DA (using a wider pot , say at least 5" in diameter). A very good alcohol stove will be able to accomplish this using a windscreen and heat shield. The next trick is to see how fast you can boil 2 cups while using 15 ml. I would say that anything below 8-9 minutes is a pretty good system. An 8 minute time to boil would mean that the stove is putting out an effective 325 watts. Best regards - Jon

Hikin' Jim
(hikin_jim) - MLife

Locale: Orange County, CA, USA
Re: A good alcohol stove on 11/23/2011 20:15:57 MST Print View

Jon Fong wrote: > A well designed alcohol stove should be able to boil two cups of 70 F water using 15 ml of DA (using a wider pot , say at least 5" in diameter). A very good alcohol stove will be able to accomplish this using a windscreen and heat shield.
Hi, Jon,

You lost me there. Wouldn't a well designed stove also use a windscreen?

HJ
Adventures in Stoving

Jon Fong
(jonfong) - F - M

Locale: FLAT CAT GEAR
Re: Re: A good alcohol stove on 11/24/2011 00:13:29 MST Print View

A majority of stove results are reported in calm conditions while not using a windscreen. Windscreens can have a dramatice impact on the overall performance. This is one of the reasons that pressurized stoves tend to have some problems when using a windscreen as the internal temperatures around the stove rises and cause the stove to burn too hot. Making the gap around the pot can reduce the interior temperature at the cost of poor perfromance in the wind. This is exactly why Trail Designs makes a great product. They have matched the stove performance to the windscreen design. The performance of the 10-12 stove in the open is ok, match it with the CC and you have a great system. I hope that explains my statement - best regards - Jon

Hikin' Jim
(hikin_jim) - MLife

Locale: Orange County, CA, USA
Re: Re: Re: A good alcohol stove on 11/24/2011 12:21:18 MST Print View

Thank you, Jon, and, yes, that makes a great deal of sense.

HJ
Adventures in Stoving