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Alcohol Stove Efficiency

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Alcohol Stove Efficiency

Postby Hetchy » Sun Mar 29, 2009 10:10 pm

I have been busy lately building and comparing Alcohol stoves. In particular the Penny stove made with Heineken cans and..well, a penny.
I have been trying to figure out if the 4 oz weight of my store bought Mini Trangia(Made by fellow Swede's for 150 years) is worth it's weight over a "beer" can stove.

What I found:

Weight wise it is no comparison.
The Mini Trangia is 4 OZ with a dry wick... period.
The Penny stove does not even register on my kitchen scale.

But being an amateur physicist I wanted to know the total efficiency of each to compare their respective fuel/weight burdens over time.
What I found is admittedly not the final word or even objective. I welcome any comments or suggestions. If anyone has a different experience I would love to hear it.. indeed that is the point of my posting! :nod:
So, here goes:
The Trangia, dry, given 1 fluid oz of Denatured alcohol at 60 degrees F(fuel and stove) will boil 2 cups of 56 F water in 9 minutes with fuel to spare. The stove was extinguished, allowed to cool, capped and put into the freezer(simulate overnight).
The Penny stove given 1 fluid oz of denatured Alcohol at 60 degrees will boil 2 cups of 56 F water in 8 minutes. Water was poured out and 1 cup of 56 degree water was added immediately. The Penny burned for 2 more minutes heating the "third" cup to 140 degrees. The Penny had totally expended it's fuel.
The Trangia was now retrieved from the freezer and relit. 1 cup of 56 F water is placed on it. It reaches boil in 5 1/2 minutes. The cup is dumped and a fresh cup of 56 F water is placed on the stove. The Trangia runs dry after 2 minutes with the second(actually fourth!) cup of water reaching 140 F.

Interesting.
I cannot conclude anything for certain due to the VERY subjective nature of the construction of the "pop" can stove. But I did find some facts useful.

Practical Things:
The Penny stove required 1 minute of priming before it began to burn smoothly.
The Mini Trangia required 25 seconds.
The Penny stove has no way to contain unburned fuel.
The Trangia can be screwed shut to save any fuel remaining indefinitely.

Subjective Things:
That last point is what I am getting around to. The 4 ounce weight penalty appears to net a real world advantage. In that, for 1 fluid ounce of fuel, The Trangia 28 can boil 2 cups of water for dinner and have enough fuel left over to boil 1 cup in the morning for breakfast.
The Penny stove expends it's 1 fluid ounce of fuel boiling 2 cups for dinner, the remaining fuel would not be enough for breakfast, therefore more would have to be added creating more evaporative losses.
The effect of Heat Capacity:
I am thinking that the heavier Trangia conserves the heat of combustion better than the aluminum can. The saved heat evaporates more fuel and aides the efficiency of the burn.
Ideally all the heat associated with combustion would be put into the water.
Of course the heavier construction exacts a greater amount of energy upon startup.
Yet the Penny stove requires more priming time. Perhaps the presence of the wick inside the Trangia accounts for it's quicker preheat time. Or perhaps the much lower degree of heat capacity of the tin can Penny stove boils the alcohol faster or loses much more latent heat to it's surroundings.

Weight Savings/Fuel Savings
At 3 cups of boiling water per ounce VS 2 cups, I would be saving 1/3 fluid ounce of Alcohol per day using the Trangia. That's three ounces in ten days.
During the entire planned PCT hike, if I cooked every day for 150 days, that would be about 50 fluid ounces saved.
It's kinda weird, but I would carry 4 (weight) ounces of Trangia stove everyday but It would amount to only 1 (weight) ounce after 10 days due to fuel/weight savings over the Penny, but only if i carry less fuel to begin with!
It really only amounts to a direct weight savings if you have to carry more than 11 days of fuel. My longest time between resupplies is 10 days.
So in effect I would be carrying 1 extra ounce of stove around, all the time, for the sake of not burning the 50 extra fluid ounces of denatured alcohol in 5 1/2 months.
:retard:
I am thinking I need to put a wick in the Penny stove and do the experiment over.
Any thoughts?
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Re: Alcohol Stove Efficiency

Postby hikerduane » Mon Mar 30, 2009 2:41 am

Check out Jim Wood's page, plus I know there are other places to visit in your quest for mo info. I made a Super cat stove this winter and "produced" after much agony, a Foster's pot.:) Using one of those can openers that removes the top of a can and leaves a smooth edge was worth the $10. The thing I see about an open burner like this is the pot has to make a seal for it to work properly. I bought a Red Bull stove, which is sealed and works as the pot support also. I only used one tablespoon of vintage denatured alcohol in it and it failed to bring the water to a boil. I need to give it another shot and use two tablespoons of fuel. Fun, isn't it? Be aware also, if you hit a stretch of forest where fires are banned, you cannot use your alcohol stove. Off to work.
Piece of cake.
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Re: Alcohol Stove Efficiency

Postby frediver » Mon Mar 30, 2009 2:47 am

Try a Brasslite stove.
www.brasslite.com
They have a sale on till Wed.
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Re: Alcohol Stove Efficiency

Postby Hetchy » Mon Mar 30, 2009 9:22 am

Thanks for the replies.
I am going to fabricate one of those cat food can stoves (Y'all know my penchant for Dog biscuits so it makes sense).
The Brasslite site led me to the Backpacking gear test site which had some very useful information and testing results.
In fact there is, buried in the text, a reasonable explaination for the effects of different materials used in alcohol stoves.. seems the idea stove would be made of Silver or Gold!
Unfortunately the Brasslite Turbo F .85 oz stove is no longer in production and a search of Google and the WWW turned up not ONE single such model for sale!
People must love their Turbo F VERY much.
The other models listed(adding the windscreen) are just as heavy as my Trangia 28(windscreen/stand included).
The Turbo F would be just the ticket though.. if only I could find one!
Oh well, Many Thanks to you both for the Info.
I am off to buy some cat food, though I don't have a cat.
Whatever will I do with the cat food... :yummy: HA! Just kidding!
I only eat the dry stuff. :D
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Re: Alcohol Stove Efficiency

Postby copeg » Mon Mar 30, 2009 9:57 am

Nice tests. Sounds like there really isn't a huge advantage either way. Its been a while since I've messed around with making alcohol stoves, but I remember going through a weekend years ago where I made and tested quite a few, including one made out of Guiness cans (had to make a few of those :D ), V8 cans, and Cat food cans (I ultimately settled on a Cat Can stove and have been using the same one for about 4 years now). One thing I did find was that adding a piece of fiberglass insulation to the inside of the stove really seemed to improve its performance and burn time - so your numbers could change based upon this. I also noticed that regardless of wind, a windscreen always seemed to help.
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Re: Alcohol Stove Efficiency

Postby frediver » Mon Mar 30, 2009 10:16 am

I'm kinda lost. If you are comparing apples to apples then a brasslite should be half the weight. The heaviest stove they list is 2.8 oz. and the compact model is only 1.9 oz.
The weight of a wind screen doesn't count if you are using the same style of screen for each stove.
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Re: Alcohol Stove Efficiency

Postby Hetchy » Wed Apr 01, 2009 8:41 am

You are right there Frediver. The compact model would save me about an ounce.. but they are nowhere to be found these days. The next lightest model is 2.8 ounces without a windscreen. The Mini Trangia 28 comes with an integrated windscreen/potholder and together (burner included) they weigh 4 ounces. The other main weight savings is fuel lost to priming. The more i experiment with these stoves I am coming to realize that a pop can stove set in the freezer requires 1/3 more fuel total when compared to my Trangia(from the freezer). The trangia simply lights and preheats while it is warming the pot. The popcan stoves I have made consistently need extra fuel to preheat before they operate efficiently.
My other concern, and one which I am compiling some data on at the moment, is the amount of fuel lost to evaporation by having to continuosly fill stoves(Pop can) at each use versus being able to fuel up the stove once every few days and simply screw the cap back on the stove after use(Trangia).
My testing data suggests I could save .24 ounces per day in fuel weight with the Trangia over the Penny Stove, and Pop can stove. That means in four days I save 1 ounce in fuel weight which is equal to the difference in weight between the Lightest Brasslight(availiable now) or my pop can stoves after the weight of pot stand and windscreen are added). Over the length of a 145 day trip like the PCT that could mean 34.8 ounces less fuel weight to carry. The unknown for me is how efficient is the Brasslight? Believe me If I could get my hands on a Turbo F right now, I would!
I know it sounds like I am just trying to rationalized using the Trangia. Let me illustrate my point with an analogy: Two cars each with a 10 gallon tank. One car gets 10 miles a gallon the other 20.
Assume Gasoline weighs an even 6lb/gallon.
The 10MPG car on a full tank can go 100 miles 6lbsX10Gal =60 lbs fuel weight
The 20MPG car on a Half tank can go 100 miles 6lbsX5Gal =30 lbs fuel weight
In my case the weights of the stoves are different. But the weight of the fuel to operate the stoves can become a much greater difference over time.
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Re: Alcohol Stove Efficiency

Postby frediver » Wed Apr 01, 2009 11:02 am

No need to rationalize the Trangia, besides you already own that stove.
I just don't think you can compare the brasslite to a pop can stove they are
two completely different designs. Preheating is not much of an issue with brasslite
models except in cold weather.
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Re: Alcohol Stove Efficiency

Postby Hetchy » Wed Apr 01, 2009 6:14 pm

Thanks Frediver. :D I get what you mean by comparing apples to apples now.
I have no experience with the Brasslite stoves so I assumed they were much more akin to the popcan design..my bad :retard: .
I would like to know how the Braslite turbo F fuel economy compares to the Trangia mini 28.
So let et me dispense with all this and just ask:
If you were to hike the PCT carrying an alcohol stove which one would it be and why?
Thanks :D

I am gonna check out that keg thingy, Thanks Hikerduane.
Last edited by Hetchy on Wed Apr 01, 2009 7:47 pm, edited 1 time in total.
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Re: Alcohol Stove Efficiency

Postby hikerduane » Wed Apr 01, 2009 7:07 pm

Did you see the "Keg", over on Anti-Gravity Gear? Plus some of the other stoves.
Piece of cake.
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Re: Alcohol Stove Efficiency

Postby frediver » Thu Apr 02, 2009 2:16 am

Truthfully I'm not sure I would pack an Alcohol stove for more than a short hike.
I really like my Turbo 11D but with my style of cooking fuel for over 1 week adds
up fast. Over the long haul I expect you will avg. at least 1.5 oz. fuel use per day,
I use closer to 2 oz. Hot drinks in the am/pm, hot cereal in the am then dinner water.
So one week =12-14oz. fuel =24cups=6qts.
Now if I use the same style of wind screen ( roof- flashing ) the total weight might increase 1-1.5 oz over what would be needed for my brasslite alone. A good cartridge stove can weigh as little as 3-4oz. and a full 1 lb. tank of fuel about 24oz. ( stove,fuel,
wind screen) total pk about 30-32 oz. using a 1/2 size fuel tank might weigh 16oz total.
The small tank will boil about 6-7 liters of water using 100gm of fuel. An Alcohol stove
will require twice as much fuel. (100gms= 3.5 oz ) so 1 8z. cart. will boil 12-14 liters.
Have you checked the REI web site?
After all that I still like my Brasslite I just dont know if I would depend on it as my only source for more than 5 days, packing 7 days worth of fuel.
I was hoping your thread would convince me otherwise.
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Re: Alcohol Stove Efficiency

Postby Hetchy » Thu Apr 02, 2009 12:30 pm

Hey Thanks for the info. I am going to look at the REI site again.
I think I was rather hoping to find a solid answer, but like so many things in life it seems to come down to personal preference I guess. I must admit I really like the silent burning of the alcohol stoves but that is likewise totally illogical if I am trying to lower my packweight not to look the CERTAIN weight advantages of the canister stoves.
I did manage to build a pretty decent Alcohol burning stove out of two Heinekin cans and a strip of coors can. I used the Penny design but left out the penny and the quarter inch hole. Instead I made a 1/32 hole half way up the dish. I also made 8 burner holes 1/32 around the ring. I put a divider strip in between the halves. When I fill the dish the alcohol stays up top, not able to drain into the bottom through the 1/32 hole. As the stove primes and heat a vacuum is created in the center chamber and draws the fuel in, forcing vapors out of the 8 jets in the burner ring. The remaining fuel below the hole in the primer pan continue to burn as the 8 jets of the ring come to life. When at full power I have 8 small jets around the outside and one large jet of flame in the middle. 9 Jets of FIRE! :eek:
I shall call it my "Little Heiny 9" !
I will be famous and sell millions of them...MuaHaHa!
Okay, reality check.
The best fuel economy I can get with it is 1 ounce per 2 cups(6minutes) including priming and it dies just as the water reaches boil. And that is back here under smiling conditions at 1532' elev. I think your figure of 2 ounces/day is more realistic. Despite the fact that my homemade Alky weighs a fraction of an ounce, the fuel weight more than makes up it's weight advantage over my Trangia. In fact the Trangia under the same test uses 3/4 ounce of fuel.. but is 3 ounces heavier!
Interestingly, I also found that the cure for an Alky stove that burns too quickly, perhaps wasting heat, is to add a few drops of water BEFORE starting the stove. My little HeinY stove I made burns it's ounce in 6 minutes.Originally, I noticed the flames would creep out from under the pot and actually rise above the level of the lid. I believed this was wasted heat so I added the water (Trangia manual suggested it) to slow the reaction. The stove did seem to burn a bit slower(subjective) though I really have no way to accurately discern the exact difference with the equiptment I have. I was able to get my stove to keep most of it's flames under the sides of the pot.. thus the 1ounce/6minute/2cups performance. Although when it gets ready to die it always goes out with a little burst for the last 10 seconds or so! Really cool looking in the dark! :evil:
While I am not giving up on the Alky stove I plan to now take on the PCT, I would be remiss If I did not take another look at the canister stoves.
Thanks for your help everybody! Hey if nothing else I got to drink beer for the first time in a while.. FOR SCIENCE!!! :drinkers: :partyman:
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