DIY Alcohol Stove Design — Basic Considerations

[Hikin’ Jim]

There's been a lot of discussion, good discussion, here on the forum lately on the basics of DIY alcohol stove design. This post is based on my own testing and tinkering over the last two years as well as the discussions here on BPL.

What follows is NOT a "follow the steps and you'll get such and such a stove." Rather, I list some basic design principles for making decent DIY alcohol stoves. For pragmatic reasons, this post is limited in scope to open type burners made from aluminum beverage cans.

For those of you who like DIY, at the end of the post there is a list of suggested "standards" that you can benchmark your stoves against.

So, without further ado, I give you: DIY Alcohol Stove Design — Basic Considerations

HJ
Adventures in Stoving

[Bob Gross]

I think the challenge is getting a fast burner design that can be choked down with a simmer ring or something so that it can become efficient. Then you can control it either way. For some night when you are freezing to death, you control it to be fast. Then for the rest of the trip, you control it to be efficient and economical with alcohol.

What other rules of thumb are there? If you get sooting on the cook pot, then that is a sign that either you are burning fuel too rapidly, or else the burner is not getting enough air (which is sort of the same thing).

–B.G.–

[Sergiy Sosnytskiy]

Self-made stoves are so light that, at least in my case, most of the weight is in the pot stand and the windscreen. So, why not take another stove, that will burn faster for those occasions when you need it fast even if it means you burn more fuel? And may be yet another tiny-winy stove for simmering.

[Hikin’ Jim]

Bob,

Yeah, that sounds nice — a variable burner like that. I'll get there eventually (I hope!), but for now this post is just about some basic considerations. DIY alcohol stoves 101 if you will. (if that).

Seriously though, I've been talking to a couple of guys about simmering and such on alcohol stoves, and of course I've got some ideas of my own on the subject. Stay tuned. :)

HJ
Adventures in Stoving

[Bob Gross]

I confess. I grew up with the MSR-XGK white gas line of thinking, so I go for the hottest/fastest burner I can find, even if that is alcohol-based.

As soon as denatured alcohol goes over $20 per gallon, I will probably change my thinking and go after fuel efficiency.

–B.G.–

[James Marco]

Basic stove design really isn't a matter of stoves. It is a matter of *systems*.
Small stoves that seem to not burn that well can burn quite well with proper mods to other pieces of the system.

1/2oz seems to be about average for the best of the alcohol stoves in the real world, ie out of a lab or kitchen. While it is generally possible to carry over some results, not all will work in the field, or, are simply too fiddly to bother with.

There is NO relationship between opening size and height except within broad parameters. This is not correct. I have made several quite tall stoves that burn hot and fast. I have also made tall stoves that burn slow, like the one you describe. Different materials in the stove have some effect, allowing heat to penetrate into the stove, boiling off vapour, very fast. This changes with alloy's. Ti doesn't conduct very well, aluminum conducts very well, copper even better, gold even better. Depending on what material the overall design and the rough temperature of operation, the size ratio can vary between 6:1 to 1/8:1. So the 45* angle you describe (1:1) ratio is not fixed except with a certain type/material/size (parameters) of the burner. This makes a good guide line for anyone building a semi-pressurized stove, though.

There are basically 5 types of stoves.
1) A plain "Altoid" burner: with or without fiberglass insulation (or pearlite)
2) A ducted port or "chimney" stove: like a Brasslite or 12-10
3) A semi-presurized stove, like many of yours, relies on liquid weight to vaporize fuel to pump the burner.
4) A pressurized stove: with fully enclosed fuel vaporization to pump the burner
5) A wicked stove: which allows full control of fuel vapourization while burning.

Possibly some others. For example the Mercury stove, a combination of several of the above. But, the primary heat is generally provided by one of the above.

Mostly, they vary on the ammount of oxygen and where it is delivered in the stove used to burn the fuel. So, enters altitude, air pressure, vapour pressure, as parameters. Since fuels are not 100% pure, (ethanol is commonly purchased as 180 proof) this also plays its part in fuel vapourization.

Due to the slow burning, low heat nature of the fuel (methanol, ethanol or blend) all need some sort of windscreen. And a good pot. And a lid. Or, as in the case of a Caldera cone, integrated system of cone/pot/lid. The windscreens generally will heat and maintain a fairly consistent external enviornment for the stove. And, transfer heated gas to the pot to transfer to the water. Lots of different heat transfers, both radiant and conducted, going on. All work into the water and out of the water.

So, in conclusion, the entire system you use for boiling water is important.

For myself, I use a WG stove for all except the shortest of weekend trips. It is very hard to compete with the actual heat density of the fuel. The stove itself, is quite heavy…but, that is another subject . . .

[Eric Blumensaadt]

Yes, White Gas is great for winter. I use an MSR Dragonfly stove – HEAVY but very controllable and efficient. Great for baking.

I prefer ESBIT/FireLite fuel tabs over alcohol. With the excellent CC Sidewinder stove/pot system & Gram Cracker fuel tab holder I use less fuel than with my former Vargo Triad base and MSR windscreen.

BUT, I use a wide pot made of Aluminum (never Ti) for the most efficient heat transfer. As mentioned several times above, it's about the system as much as an efficient stove.

[Hikin’ Jim]

Hi, James,

Thanks for all your insights! I don't have time to digest them all right now, but I'll dig into them a bit more later.

I will say this though: If you look through the photos in my blog post, you'll see that 100% of the tests were done outdoors and the great majority of those were done in the field. Only those photos with stoves shown on a slab of marble or a wooden table (two photos) were done in a backyard. The remainder were done in Santa Anita Canyon, Winter Creek, near Aspen Grove in the San Bernardino National Forest (elevation about 7,000'), and in the woods near Beaudry DDA.

You are of course right about stoves being a system, and this is particularly true for alcohol stoves. These stove were tested with a variety of windscreen configuration as you can probably see from the photographs. Between the variety of windscreen configurations used and the variety testing conditions and locations, for the type of stove shown, the results have a lot of content. I have (as I noted on my blog) limited the discussion to only Type Three of the five types of stoves you list. Thank you for your list by the way. You are one of the people mentioned in the "acknowledgements" at the bottom of my blog post. :)

HJ
Adventures in Stoving

[Hikin’ Jim]

Bob Gross wrote: > What other rules of thumb are there? If you get sooting on the cook pot, then that is a sign that either you are burning fuel too rapidly, or else the burner is not getting enough air (which is sort of the same thing).

I will have to admit to some frustration when it comes to soot. With high ethanol blends of alcohol, I get some soot with almost every design that I've tried. I consider the soot level to be acceptable (certainly FAR better than running with isopropyl alcohol!), but even on good, efficient designs I'm still getting some soot.

Methanol (yellow HEET to be specific) burns very cleanly as does Klean Strip SLX Denatured Alcohol. However neither methanol nor SLX denatured alcohol have as much heat content per gram as a high ethanol content blend.

What have I come up with at this point? I've come up with the basic design considerations for an open burner of the type shown in my blog. I've done enough testing and have talked with enough people to have very strong confidence in what I'm saying. But do I now know everything about alcohol stoves? No. The necessarily limited scope of my blog post reflects that.

Now that I know the basic burner design considerations, I'd like to turn to subjects such as:
-Fuel efficiency considerations.
-High Ethanol content alcohol blends — do they make a material difference?
-Beyond boiling: Versatile alcohol stove systems.

Naturally, I've got some other ideas too.

HJ
Adventures in Stoving

[Bob Gross]

There are all sorts of minor details which can make a particular alcohol burner handy. I have tiny open-top burner where the fuel storage (35mm film can) fits perfectly into it. Even with a bit of aluminum foil and some paper matches, the whole thing fits into a shirt pocket.

Many simple alcohol burners are so narrow that they will tip over too easily when a pot is on-board. To avoid that, you can try to sink the burner into the sand or gravel, but then that has a cooling effect on the fuel, and that tends to demand more priming.

–B.G.–

[Larry De La Briandais]

.

[James Marco]

Yeah, this was one of my basic objections to going with high efficiency burners. Great when you have a well tuned system for one. Not real usefull, otherwise. I am really not that big of an alcohol user. It is rare for me to spend less than a week to ten days out at a time for the past couple years.

[al b]

A burner with yellow flames with no pot above it may well give nice blue flames once pot on top causing turbulance.

I dont get normally get sooting from 90% ethanol 10% methanol, but the purple dye causes blackening.

[Hikin’ Jim]

Bob:

I don't know if you saw my criteria for what constitutes a "good" stove:
1. Lightweight. Hey, I gotta carry this thing, right? And if I'm going to give up the convenience of gas, then I better be getting something out of it — like a lighter pack.
2. Efficient. So, what good is a light stove if it eats fuel like an old 450 V8 Chevrolet engine with a four barrel carburetor? Who cares if the stove is light if I have to carry four times the fuel?! The danged thing needs to save me weight, remember? I want a stove that will do the job with a minimum amount of fuel. See also Technical Appendix at the end of this post.
3. Effective. Yeah, it has to be light. Yeah, it has to be efficient. But it has to do the job. A stove that won't cook doesn't save me anything. It's got to work. Not negotiable.
4. Minimum "fiddle factor." If I need a degree in mechanical engineering and a Rube Goldberg mindset just to run the thing, then it's not the stove for me.

For me anyway, per #4 above, if I have to dig it into the ground, or my dinner is at risk, it's not the stove for me. Also, per #2 above, if a stove requires priming, it's not the stove for me. Priming is by definition inefficient.

HJ
Adventures in Stoving

[Jon Fong / Flat Cat Gear]

HJ – given your 4 criteria, a tealight stove would meet all of your needs.

1) Lightweight – probably the lightest stove out there
2) Efficient – 15 ml will boil 2 cups. If you need more capacity get a bigger cup. you could probably cut down a small juice can and it will be fine.
3) Effective – As above 15 ml to boil 2 cups
4) Minimum fiddle factor – nothing simpler than a tealight stove.

Best regards – Jon

[Bob Gross]

"4. Minimum "fiddle factor." If I need a degree in mechanical engineering and a Rube Goldberg mindset just to run the thing, then it's not the stove for me."

I guess you really don't like the MSR-XGK then.

That senior class in Thermodynamics and Combustion really helped.

–B.G.–

[M B]

Yep. Agree totally with the tealight.

If you want a stove to use for a small solo 2 cup pot like SP600, thats all that is needed.

But its just too simple for some.

K.I.S.S.

[Hikin’ Jim]

Alan Bradley wrote: > A burner with yellow flames with no pot above it may well give nice blue flames once pot on top causing turbulance.

Alan,

Yes, just about every stove burns differently with the pot in place. I take the pot off for photography, but I'm definitely getting soot even with the pot on.

Alan Bradley wrote: > I dont get normally get sooting from 90% ethanol 10% methanol, but the purple dye causes blackening.

A couple of people have suggested I try cutting the high ethanol blend alcohol with methanol rather than water to eliminate sooting. I'm going to have to try that although I wonder if high ethanol content blends are worth it if I'm going to have to fiddle with blending in some methanol. SLX might wind up being more practical even if the high ethanol content blend has more heat per gram. I'll have to play with this some.

HJ
Adventures in Stoving

[Hikin’ Jim]

Jon Fong wrote: > HJ – given your 4 criteria, a tealight stove would meet all of your needs.

1) Lightweight – probably the lightest stove out there
2) Efficient – 15 ml will boil 2 cups. If you need more capacity get a bigger cup. you could probably cut down a small juice can and it will be fine.
3) Effective – As above 15 ml to boil 2 cups
4) Minimum fiddle factor – nothing simpler than a tealight stove.

Best regards – Jon

Hi, Jon,

ZenStoves has a nice tealight stove section. To be honest, I haven't played with them. Building a stove out of them looked like it would be little tricky. I was also concerned that their maximum alcohol capacity would be a little limited on those occasions where I need to boil 3 cups at a time. I'll have to try a simple open cup burner type tealight stove some time. I've seen Jason Klass' tealight set up on YouTube, and it looks pretty simple yet effective.

HJ
Adventures in Stoving

[Hikin’ Jim]

Sergiy Sosnytskiy wrote: > Self-made stoves are so light that, at least in my case, most of the weight is in the pot stand and the windscreen. So, why not take another stove, that will burn faster for those occasions when you need it fast even if it means you burn more fuel? And may be yet another tiny-winy stove for simmering.

Hi, Sergiy,

That's actually a very practical solution, and there's not a lot of extra weight with this type of burner. I know guys who do just that. They carry two burners: one for slow cooking, and another for fast cooking. I may do some experimentation with just exactly that kind of set up.

HJ
Adventures in Stoving

[USA Duane Hall]

HJ, you have mail.
On topic of sorts. Just thinking if you had too much fuel capacity in your stove and you filled that up, would that slow down the stoves ability to reach high heat output? I've noticed on my old brassy stoves, that when I prime them, it takes a few minutes for the flames to really get going as the fuel needs to vaporize in the priming pan to burn. Could a larger alky stove be used for slower cooking or best to just rig a simmer cap/ring on the normal sized stove? Your thoughts, just throwing something out here.
Duane

[Hikin’ Jim]

Hi, Duane,

At least with what I've tried, adding more fuel hasn't appreciably slowed the stove down throughout the burn. Adding more fuel might cause the stove to take longer to warm up, but it doesn't really cause more efficient burning in my experience.

A stove with more physical mass will likewise take longer to warm up but won't necessarily burn more efficiently overall.

I'd say the best way to get an efficient burn is to use a burner that is efficient by design.

Now the whole simmer ring idea is very intriguing to me. In my experimenting, I've come across some designs with very low flames, generally a tall stove. It occurs to me that I could cut the top off a tall stove and press fit it over the top of a shorter stove whenever I need a low flame. You'd basically have two settings: High without the "over cap" and low with the "over cap." This isn't a particularly elegant solution, but it is simple and would work.

A more elegant solution is one where you can truly vary the flame not just have a high and a low setting. This is more where my interest lies. With something like a 12-10 stove, with ventilation ports in the side wall, you could construct a "ring" cut from the wall of an aluminum can that would slide over the 12-10 stove's outer wall. The "ring" would have holes cut in it that align with the ports in the 12-10 stove. If you aligned the holes exactly, the 12-10 stove would function normally. If you rotated the "ring" slightly, you would partially block the 12-10's ports, causing a smaller flame.

I've talked to guys online who have done something along these lines, and I've seen some photos of DIY rigs, but I've not tried it (yet) myself.

A DIY stove of the sort shown in my blog doesn't have ports that you can use to vary the flame.

The first solution I mention above (an "over cap" instead of a "ring") might be youre only option with something as simple as the stove on my blog.

HJ
Adventures in Stoving

[Hikin’ Jim]

The idea behind this blog post was to list out some design elements of decent DIY alcohol stove (within a certain scope, e.g made from aluminum beverage cans).

With any project, it's important start with the desired result in mind, so maybe you'll want to take a look at the appendix: Standards for DIY Alcohol Stoves. These are a set of "standards" by which you can benchmark a stove and say, "yep, it's a good stove." or "nope, still needs a little work."

You may need to tweak my "standards" to fit your particular style and needs, but at least you've got a starting point all in one place in a fairly concise form. I wish when I started looking at alcohol stoves in 2007 that I had had a clear idea of what constituted a good stove.

I hope that these "standards" will at least be food for thought and discussion.

HJ
Adventures in Stoving

[Hikin’ Jim]

James Marco wrote: > Basic stove design really isn't a matter of stoves. It is a matter of *systems*. Small stoves that seem to not burn that well can burn quite well with proper mods to other pieces of the system.

Agreed. It's not just about burners, it's about systems. However, the burner does matter. If you were to look back at the last several posts on my blog, you would see that I use several different set ups to test burners including a Trangia 27, a Clikstand, a plain BPL Ti windscreen, and a Caldera Cone. I'm actually employing a variety of windscreen/pot support combinations just so I can get some idea of how good the burner itself is.

James Marco wrote: > 1/2oz seems to be about average for the best of the alcohol stoves in the real world, ie out of a lab or kitchen. While it is generally possible to carry over some results, not all will work in the field, or, are simply too fiddly to bother with.

Yep.

James Marco wrote: > There is NO relationship between opening size and height … so the 45* angle you describe (1:1) ratio is not fixed except with a certain type/material/size (parameters) of the burner. [emphasis added]

And in this case, my blog post is very definitely limited to certain materials (aluminum cans) and a certain type of burner (open, semi-pressurized).

James Marco wrote: > There are basically 5 types of stoves.
1) A plain "Altoid" burner: with or without fiberglass insulation (or pearlite)
2) A ducted port or "chimney" stove: like a Brasslite or 12-10
3) A semi-presurized stove, like many of yours, relies on liquid weight to vaporize fuel to pump the burner.
4) A pressurized stove: with fully enclosed fuel vaporization to pump the burner
5) A wicked stove: which allows full control of fuel vapourization while burning.

That's a good and helpful list. I think I've seen something like it before, maybe on Zen Stoves, but I haven't looked at Zen in a while. Thanks for posting that.

HJ
Adventures in Stoving

[James Marco]

Jim,

Feel free to use whatever you can glean out of my poor writings. I cannot keep them organized. Besides, making and building alky stoves is an old subject. Rand at TD sent me a picture from the Civil War for one a couple years back. It was an older design then that seemed to be fairly effective, though likely heavy made out of brass. Since it was in production at that time, I assume it was based on earlier designs.

Anyway, some other important considerations:
1) Oxygen (or air)
2) Heated Fuel vapour
3) Mixing of the two
4) Some kindling flame, preferably *after* mixing
5) A control of some sort

Plenty of heated fuel and air. Initially, a small reaction, then larger flames as the fuel air warms. BOTH need to react. BOTH need to be heated. Not just the fuel. Whatever fuel you use, a primer, it might be a self primer, is needed. The fuel and air need to be brought to kindling temp before they can react, but some sort of additional spark is required to start the reaction. Some controll of the reaction is needed to prevent runaway reactions (self limiting is the usual methode for small camp stoves like you pictured.)

I was focusing on mixing the fuel/oxygen for efficient burning. Some observations: Swirling seems to add a lot to mixing, and tends to focus heat to the bottom of a pan. The later disipation leads to wide pots, up to a point, being much more efficient than tall pots, but even these can benefit from a smaller, more focused flame. Using a press pin, rather than a drill, it should be possible to angle the jets. In a dynamic flow, this will create a swirl, helping to focus heat, and create a greater degree of mixing turbulence. Adding air inlets into the combustion chamber seems to help by increasing the burn time available to the fuel. Probably not possible on the stove you picture. For some slight modifications to the stove you pictured, turbulence in a semi-pressurized stove design can help, too. I would submit, that the jets should be alternated between the inner and outer part of the stove, allowing more turbulence to the inner, open priming/combustion chamber, and more oxygen to the outer jets. This should have the effect of delaying the burn slightly for the inner, open fuel by reducing available oxygen. And, heating the fuel vapour so it will burn more quickly when it IS mixed with the oxygen. Again, using a push pin, angle the jets upward A slight diameter decrease would also help by reducing the ammount of oxygen available to the inner combustion chamber. The control is important because the initial heat output(for the first minute or so) is different from a stable system. This means that initially a slow burning stove may overheat and become a fast burning fireball(two extremes.) So moderating the maximum heat helps maximize the efficiency and prevents the high secondary heat outputs, and comensurate loss of efficiency, common with small stoves. This is really difficult with the stove you pictured, however. I believe the modifications I suggest will help some. Again, expect no more than 5-10%, though. But, it should also solve the ethanol/soot problem. Higher reaction temps will usually mean cleaner burning, provided the reaction gets enough oxygen. Just a thought…

[Author]

Posts