DIY Alcohol Stoves -- Basic Design Considerations

[hikin_jim]

There's a lot that goes into making a reasonably good DIY alcohol stove. What are the basic design considerations for putting together a decent one, one that won't burn through a week's worth of metho the first two days you're out? Well, I've tried to compile a list of basic design considerations that I've taken from the last several months of tinkering and testing.


I invite you to take a look at: DIY Alcohol Stoves -- Basic Design Considerations.

HJ

[John Sheridan]

Have you tried to make an wick stoves or any stoves half the size of the ones you have made, they will generaly burn less fuel for the same or better job.

I have made some coke can stoves and they work, but my trangia is always better, fuel and cook time wise.


Though I have a mini cat stove which is pretty good and works well on my pot.

Cheers.

[hikin_jim]

Hi, John,

I haven't experimented (yet) with wick stoves. However, the stove shown toward the end of my blog post is more efficient than a Trangia burner. I was able to boil 500ml of 7C water with 15ml of metho. That's better than what a Trangia can do. I'm very pleased to have gotten something into this range.

HJ

[Tony]

Hi HJ,

Many thanks for posting this information, it is very interesting that a height to burner hole diameter is a around a 1:1 ratio, when I checked my Trangia burned it has height of 41.75 mm and a hole diameter of 39.9 mm, though the 12-10 is a little off the 1:1 ratio, it has a 35mm height and 30 mm hole diameter.

Have you thought about the influence of mass on alcohol stove performance, I often think this is overlooked in alcohol stove design, with my volcano stove design I can adjust burn times with changing the mass of the center pin. It would be interesting to make two similar stoves of different thickness walls and then do some testing.

Another consideration is the temperature of the ground or in stove testers case the temperature of the test bench, I have noticed that when testing and using the same place on the bench or ground the efficiency can change as the bench or ground warms up, I use several pieces of wooden board that I exchange between tests.

When I do my testing I start with what ever temperature the water comes out of my tap I use 500 ml (500 grams), I then run the test but I monitor the temperature and when it gets to 95ºC I then terminate the test, I then calculate the fuel used per ºC, I then I times this figure by 80 to get a result of grams of fuel used/80ºC in this way I can accurately compare results.

Tony

[Orion]

I'm curious, all the "tinkering and testing", is it more or less a trial and error method to figure out what works?
Or do you have a sense for why some designs are better than others?
For example, why would the pin mass on Tony's stove matter?

Also, ignoring weight, is the Trangia considered a really good burner or just an okay one?

[hikin_jim]

Hi HJ,

Many thanks for posting this information, it is very interesting that a height to burner hole diameter is a around a 1:1 ratio, when I checked my Trangia burned it has height of 41.75 mm and a hole diameter of 39.9 mm, though the 12-10 is a little off the 1:1 ratio, it has a 35mm height and 30 mm hole diameter.

Have you thought about the influence of mass on alcohol stove performance, I often think this is overlooked in alcohol stove design, with my volcano stove design I can adjust burn times with changing the mass of the center pin.

Another consideration is the temperature of the ground or in stove testers case the temperature of the test bench, I have noticed that when testing and using the same place on the bench or ground the efficiency can change as the bench or ground warms up, I use several pieces of wooden board that I exchange between tests.

When I do my testing I start with what ever temperature the water comes out of my tap I use 500 ml (500 grams), I then run the test but I monitor the temperature and when it gets to 95ºC I then terminate the test, I then calculate the fuel used per ºC, I then I times this figure by 80 to get a result of grams of fuel used/80ºC in this way I can accurately compare results.

Tony

Hi, Tony,

I was hoping you might weigh in on this issue since you know more about stoves in technical terms than I will probably ever know (unless you or someone like Roger teach me).

First, let me say that most of my testing is done out in the field and done without the benefit of any precise measuring equipment. I do of course have a measuring cup for the water and another for the fuel, but I have no temperature probes, gram scales, or the like. So, when I say "about," what I mean is that I can see that there is a relationship between, in this case, height and burner opening size, and I can see that it approaches 1:1 for a practical stove, but I cannot precisely determine the ratio. And of course "practical" will mean different things to different people.

Second, these results are (necessarily) very narrow in scope. I would have a write up longer than the the voter registry of China if I were try to cover all aspects of alcohol stoves. These results are applicable for open burners of the type described in my blog post. Since the construction materials used were aluminum drink cans, the results were comparable from one of stove to another. Stoves of differing materials will undoubtedly have their own quirks. For the purposes of this blog post, I wanted something fairly "accessible" to the average person: materials that are inexpensive, readily available, and relatively easy to work with, materials that don't require a lot of specialized tools or a great deal of skill.

One note on the 12-10 burner. The 12-10 burner is actually a slightly different burner than my homemade burners. The 12-10 burner is actually a "ducted port" type burner because of the presence and positioning of the ventilation ports on the walls of the burner. Some of the same things apply, but the burner can have a proportionally smaller opening because of the way the ventilation ports are situated. My understanding is that since the ports on the outer wall are lower than the ports on the inner wall, the air will, when heated in between the walls, rise and accelerate into the interior of the 12-10 burner. It's sort of a primitive turbo charger. The net effect is that the 12-10 burner can have a smaller opening than would otherwise be practical. This is my feeling anyway; your insight into the 12-10 burner would be greatly appreciated.

I have not experimented with the effect of the mass of the materials of a stove and the effect of that mass on burn characteristics.

I absolutely have noticed the profound effect that ground temperature can have on burn characteristics. I believe I've done enough testing under enough varied conditions that I've got reliable results. I have also compared notes with other homemade stove builders. My results compare well with theirs. I will however continue to tinker.

HJ

[Tony]

Hi HJ,

I was hoping you might weigh in on this issue since you know more about stoves in technical terms than I will probably ever know (unless you or someone like Roger teach me).

I have been reading your post with interests, sorry about not replying to some of your posts but I have been busy at work trying to get some experiments up and running, I am hoping things quiet down soon and at home I have been distracted by being given a very good book about Mawson, Shackleton, Scott and Amundsen I am enjoying the book so much I am struggling to put down.

My knowledge of alcohol stoves is not that great, I really do not have that of an strong an interest in them, gas stoves is where I want to know more.

First, let me say that most of my testing is done out in the field and done without the benefit of any precise measuring equipment. I do of course have a measuring cup for the water and another for the fuel, but I have no temperature probes, gram scales, or the like. So, when I say "about," what I mean is that I can see that there is a relationship between, in this case, height and burner opening size, and I can see that it approaches 1:1 for a practical stove, but I cannot precisely determine the ratio. And of course "practical" will mean different things to different people.

I do understand what you are saying, with stove testing after a while you do get a feel for what is going on, I often run test without measuring as I have an idea what to expect.

Second, these results are (necessarily) very narrow in scope. I would have a write up longer than the the voter registry of China if I were try to cover all aspects of alcohol stoves

Yes I agree, alcohol stoves are very varied and the article is about center flue stoves, I have been trying to quantify stove flame size on the bottom of pots, not easy.

I have not experimented with the effect of the mass of the materials of a stove and the effect of that mass on burn characteristics

My mass suggestion was only that a suggestion to look at in the future, it was something I feel is overlooked in alcohol stove design.

I absolutely have noticed the profound effect that ground temperature can have on burn characteristics. I believe I've done enough testing under enough varied conditions that I've got reliable results. I have also compared notes with other homemade stove builders. My results compare well with theirs. I will however continue to tinker.

I have noticed your figure match up with a lot that I have read, thanks for posting your results and I look forward to reading the results of the next tests.

Tony

[michael_p]

I absolutely have noticed the profound effect that ground temperature can have on burn characteristics.

This is my experience as well. On one occasion I placed one of my DIY alcohol stoves directly on cold wet ground. It's the type that has an open top that you fill then light and wait for the side jets to bloom before putting your pot on. It took significantly longer to "bloom" in the field than I had experienced at home. And once it got going it didn't burn quite as well as I had experienced at home.

I know this is only anecdotal but the difference I experienced was enough for me to ask "why is it so?". And I'm glad to read someone else has noticed a similar effect.

Thanks for the thread hikin_jim, another good read.

Cheers,
Michael.

[hikin_jim]

I'm curious, all the "tinkering and testing", is it more or less a trial and error method to figure out what works? Or do you have a sense for why some designs are better than others?

I started getting interested in alcohol stoves in the summer of 2007. At that time, I didn't have the foggiest clue of what might constitute a good design vs. a poor one. I read a lot on BPL. I purchased some stoves and made others. Things really accelerated in 2010 when I found out just how inefficient the stove I was using was compared to the stove of a good friend of mine. I actually ran out of alcohol on one particular trip and couldn't finish my cooking. I got really disgusted and decided to find out about alcohol stoves. Now, I have a pretty good, intuitive idea of what will make for a good stove. Plus I can bounce things off of people on forums such as this.

For example, why would the pin mass on Tony's stove matter?

Tony will have more to say about this I'm sure, but my read on the matter is that it's probably more than just the mass. I would think that it has to do with thermal conductivity, surface area, and mass. Again, I will defer to Tony who has greater scientific background and has done actual testing, but, just based on what I've seen of the stove, I'll make some general remarks.

Since the central pin in Tony's volcano stove is in direct contact with the body of the stove, heat will naturally be conducted into the stove body. The mass of the body will absorb some of the heat, and then transfer that heat into the fuel which in turn will cause increased vaporization in the fuel which will affect the overall rate of combustion. If the central pin were stainless steel (a relatively poor heat conductor), I would expect less thermal conduction. If the central pin were copper (a relatively good heat conductor), I would expect more thermal conduction. Greater mass in the pin would generally transfer a greater amount of heat although there may be a limit over a certain amount of thickness. If the pin's mass were arranged in such a way to maximize surface area, I would expect greater heat transfer. Those are just some general remarks. I'm sure Tony can give us some very specific empirically derived data.

Also, ignoring weight, is the Trangia considered a really good burner or just an okay one?

In my opinion, the Trangia is a very good burner overall. I think it's a nice balance between speed and efficiency. It's robust. The simmer ring gives one the ability to a) simmer and b) easily extinguish the stove. The cap with it's "O" ring seal allows one to leave unburnt fuel in the stove for later use. Other than perhaps the weight, I have nothing but good things to say about the Trangia burner.

Now, of course, when temperatures get below somewhere around 5C, alcohol stoves can suffer a bit. And for snow melting, an alcohol stove would not be my first choice. But when the temperatures are at least two digits, I think alcohol stoves, albeit slow, are a very good choice, depending on your particular needs.

HJ

[Tony]

Hi HJ,

Tony will have more to say about this I'm sure, but my read on the matter is that it's probably more than just the mass. I would think that it has to do with thermal conductivity, surface area, and mass. Again, I will defer to Tony who has greater scientific background and has done actual testing, but, just based on what I've seen of the stove, I'll make some general remarks.

I am not sure that I have more knowledge than you do, but all of the 'thermal conductivity, surface area, and mass" are important in alcohol stoves, if Roger C sees this thread he might be able to add more.

Since the central pin in Tony's volcano stove is in direct contact with the body of the stove, heat will naturally be conducted into the stove body. The mass of the body will absorb some of the heat, and then transfer that heat into the fuel which in turn will cause increased vaporization in the fuel which will affect the overall rate of combustion. If the central pin were stainless steel (a relatively poor heat conductor), I would expect less thermal conduction. If the central pin were copper (a relatively good heat conductor), I would expect more thermal conduction. Greater mass in the pin would generally transfer a greater amount of heat although there may be a limit over a certain amount of thickness. If the pin's mass were arranged in such a way to maximize surface area, I would expect greater heat transfer. Those are just some general remarks. I'm sure Tony can give us some very specific empirically derived data.

When I was designing the Volcano my thoughts were that the heat will be transferred into the alcohol via the pin, I tried several different size and shaped pins with larger surface area and smaller surface areas, I made one with a large flat head and I also tried a copper pin, by using a smaller pin I could make the flame smaller and a bigger pin a bit faster, I cannot remember the results with the copper pin but I think it did not work as well as the aluminum pin I am using at the moment, in all cases the stove body also heated up which I think is from the flame not from any feed back from the pin, the contact area is very small. I will have to go through my stove results note book to find my test data.

Tony

[andrewa]

I'm going to throw in a few more potential variables that I've just run into.

I've been doing some basic comparisons between the standard coke can stove and the cat tin stove, however I also wanted to use a cut down Ikea cutlery holder as a stove stand, as I wanted the option of making a wood burning stove on our forthcoming trip. I also use som flashing as a wind shield, although the piccies I have put below were taken inside a shed

With the cat tin stove, I found that my particular version worked better if the pot wasn't resting on the top of the tin. For mine, the pot needed to be about 5mm above the top of the cat tin to get the side burners to work properly. Using the Ikea pot holder as shown below, and with cat tin elevated to be about 5mm below the billy, the side burners certainly worked, but the flame shot out well beyond the cutlery stand and the billy, which seemed wasted heat, even with the windshield to direct it up the sides of the pot. 20mls of metho boiled 500mls of tap water in 10-11 mins, and burned for ~12mins

With the coke can stove in my "Ikea stove stand", I was surprised that instead of getting the rather weak 2-3cm vertical jets out of the holes around the rim which you get when resting the pot on a wire stand, something happened whereby the jets became more powerful, and started to shoot out sidewards, beyond the confines of the Ikea stand, but not as far as with the cat tin stove, and basically the whole bottom of my Evernew 1.2l billy was being heated.

Boil time about 9 mins, and burn time about 12 mins. Looking at the piccies I've taken, I note that the pot could be lower down towards the tips of the blue flame to improve efficiency.

Wondering whether the stove/ikea cutlery holder, and outside wind shield make a "multi-walled" burner which improves efficiency.

Whilst this is all very basic observation, and I'm not interested in testing it more accurately, it works for me. My need is to boild 500mls of water 18 times during a trip, and maybe have enough fuel for assisting lighting a few damp fires. We have peviously taken a Kovea stove/windsheild etc, and 2 x 250ml gas cylinders (1 lasts 7 days for our use). Total weight of that about 830g+. This metho stove will be lighter - ~400mls of fuel, and about 100g of Ikea cutlery holder and stove. Slower boiling times, but a few mins doesn't make much difference to our day.

[hikin_jim]

When I do my testing I start with what ever temperature the water comes out of my tap I use 500 ml (500 grams), I then run the test but I monitor the temperature and when it gets to 95ºC I then terminate the test, I then calculate the fuel used per ºC, I then I times this figure by 80 to get a result of grams of fuel used/80ºC in this way I can accurately compare results.

Tony,

That's a very good protocol. At the very least, it saves you from having to try to have water at a standard temperature. Just use whatever temperature you've got, then calculate fuel usage per degree C and multiply by 80. Very smart.

I suppose I really ought to break down and buy some proper test equipment. Our place is very small right now, but some day...

HJ

[hikin_jim]

I cannot remember the results with the copper pin but I think it did not work as well as the aluminum pin I am using at the moment, in all cases the stove body also heated up which I think is from the flame not from any feed back from the pin, the contact area is very small. I will have to go through my stove results note book to find my test data.

That's very interesting that aluminum would work better than copper since copper as I recall is a bit better at conducting heat. Maybe the copper provided too much thermal feedback?

Perhaps you've shared this before, but how did you come up with the idea for your Volcano stove? The somewhat conical top is interesting to me. I've seen a couple of variations on this time, and I'm wondering what it was that led you to try this design.

I think you've told me before, but how many ml of metho does it take for the Volcano stove to raise 500ml 80C? And how does that compare to a Trangia burner? A 12-10 burner? Sorry, giving you homework, aren't I? Answer if you get the time.

HJ

[hikin_jim]

I have been reading your post with interests, sorry about not replying to some of your posts but I have been busy at work trying to get some experiments up and running, I am hoping things quiet down soon and at home I have been distracted by being given a very good book about Mawson, Shackleton, Scott and Amundsen I am enjoying the book so much I am struggling to put down.

Quite understandable. You wouldn't hear from me for a week.

HJ

[hikin_jim]

...the side burners certainly worked, but the flame shot out well beyond the cutlery stand and the billy, which seemed wasted heat, even with the windshield to direct it up the sides of the pot.

Generally, yes. If the flames go up the side of the pot, fuel is being wasted. It's better to find a stove that burns a little bit more slowly with a bit smaller flame. The ideal is a flame that stops a cm or two short of the edge of the pot.

With the coke can stove in my "Ikea stove stand", I was surprised that instead of getting the rather weak 2-3cm vertical jets out of the holes around the rim which you get when resting the pot on a wire stand, something happened whereby the jets became more powerful, and started to shoot out sidewards, beyond the confines of the Ikea stand...

That's what makes comparisons different -- there are so many variables. Windscreens and stands like yours can dramatically change the burn characteristics. In your case, I'd say the windscreen/pot support set up reflected a lot of heat back to the burner which caused the fuel to vaporize more rapidly which in turn caused your stove to burn hotter.

20mls of metho boiled 500mls of tap water in 10-11 mins, and burned for ~12mins

Not bad on fuel consumption, and you got a pretty good duration for 20ml. The more efficient stoves out there boil 500ml with 15ml metho. At least that's the standard I aim for. Relatively few stoves can beat that, and those that do are typically very "touchy" and take forever to bring water to a boil.

HJ

[hikin_jim]

Speaking of standards, what constitutes a good alcohol stove? I don't know if anyone saw it because I added it after the fact, but I added an appendix to my blog post: Standards for DIY Alcohol Stoves.

Now, those are fairly high standards. They're not meant to be overly critical of stoves like the one referenced in the post above. 20ml is by no means a poor showing (now above 30ml for 500ml boiled, that generally is a poor showing). But high standards are something to shoot for if you're someone who likes to continue to refine things.

What do you think? Are those reasonable standards? Helpful at all?

HJ

[Ticklebelly]

Thanks for the thread hikin_jim, another good read.

Me too. But now off to play some more. Interest only, really, I love the tinkering.

Ticklebelly

[hikin_jim]

Interest only, really, I love the tinkering.

Ah, yes, I believe I can relate to that. Got any photos for us?

HJ

[awells]

I've been making various alcohol stoves for a few years now after my interest was aroused by a bloke (Paul ?) from Springwood Bushwalkers telling me about his Duke of Edinburgh high school students making their own "Pepsi Stove". From my experience the "Pick of the Crop" is Mark Jurey's Penny Alcohol Stove II. It is so simple, quick and easy to make from just a couple of aluminium drink cans using nothing more than a pair of scissors and a push-pin/thumbtack/tiny nail etc. The cold ground issue is solved with an insulation base made from the top of one of the cans. The other can top is used to make a simmer ring which works like a charm. It is a pressurised stove and the "pressure regulator" is the penny covering the fuel hole in the centre of the burner_ I just use a 5c piece as it's small and light enough. Using 30ml of meths it easily brings 500ml/2cups of water to the boil with enough fuel left for a simmer before covering the billy with a cosy if you're cooking a meal. Using 40ml of fuel gives you a verylong simmer or you can boil a liter of water. I use the lid off a plastic peanut butter jar to snuff out the flame and conserve fuel. The attached photo shows my version of a side-jet stove on the top left (no pot stand required; just carefully balance your billy on the top once the side jets are alight). The rest of the photo shows the various parts of a Penny Alcohol Stove including the wire potstand.

[Leppy]

passing time by making stoves is one of my favs...

This one is a dual wall

Red Hot Bull.JPG (40.38 KiB) Viewed 108253 times

[Leppy]

And this one is a single wall "cat can" stove

PC100177aaa.JPG (33.24 KiB) Viewed 108247 times

[Leppy]

And here is a old vid from when I first started making them. I was testing the hole patterns