Stove performance?

[SGT Rock]

For ya'll that make your own stoves, how do you measure performance?

The reason I ask is because when I first started, I prefered the Cat Stove because it is an inferno. It makes hot water like a volcano. My primary concern was seeing hot water made quickly, and the Cat Stove is about the best for that. You can see bubbles forming in this sucker in about 3:30 or so depending on weather. But when I started truely testing stoves I found this was only about 175-200 degrees. IT takes about 24ml of fuel to get a true 212.5 degree boil in a Cat Stove.

After I started testing fuel efficiency of stoves, I've been working to maximum efficiency for that because in the end, this means I carry less actual weight. My current stove only weighs 0.3 ounces and has a 0.3 ounce windscreen for a 0.6 ounce total. But best of all, it can achive a true 212.5 degree boil with a mere 12ml of alcohol, but it takes about 11:30 to get there - but I don't mind the weight. And I've even figured out how to make this stove simmer (if I want it too) for 21 MINUTES on 6ml of fuel without any extra parts! But if it sounds too good to be true, it may be - this is only in kitchen conditions, I still need to trail test it before I post the instructions.

I've found a good middle ground of solid performing stoves, the Turbo V8 stove being my current favorite.

But It gets me to the tortise and hair thought. A stove that heats water quickly is like a dragster, it takes a lot of energy to do it. While a weight efficient stove is like a Honda Hybrid car, it is slow and small, but highly energy efficient. Some hikers like the sexy volcano like stove (I know I did), but the slow burning economy stoves are probably the best for us.

So anyway, back to the original question, how do you measure your stove performance?

[Hammock Hanger]

I'm real precise... Does it cook my dinner! Actually most soda can stoves I made were unreliable as they would cook fast one day and not at all the next. That's when I went to the tangia. I never really got down to measuring the time, the amount of fuel, fuel used per minute, etc. I carried one bottle of fuel - it lasted 6-7 days. My water boiled up in a couple of minutes, I was happy.

Sgt Rock: You are one man for DETAILS! I think that's a compliment.

Hammock Hanger

[highway]

Originally posted by SGT Rock

IT takes about 24ml of fuel...
....it can achive a true 212.5 degree boil with a mere 12ml of alcohol..
21 MINUTES on 6ml of fuel without...

So anyway, back to the original question, how do you measure your stove performance?

I don't mean to offend but,speaking for myself, I'd prefer the measurements not in the metric system, but in our antequated, archaic, English system. Those little mililiters are a little difficult for this 'ole Southern boy to get a quick grasp on. I'm not bad on Km for distance but the metric volumetric measurements seem to slip on by me. Now, if you would just convert them to ounces[weight], a unit which most of us use daily, it would make it easier for us to grasp the significance of your findings. I honestly don't believe many US citizens can quickly picture a ml, because we just don't use them much, yet.......and I'm not even sure I want to!

[SGT Rock]

Sorry about that Highway.

Up until very recently I was using measurements in 1/4 ounce increments, based on the belief that a cap from a soda bottle was 1/4 ounce. But it turned out I was a little off. Turned out that a soda bottle cap is approximately 6 ml of fuel. So when I say it takes me 6 ml, it really means it takes me one cap full of alcohol from my soda bottle. When I say it takes me 12 ml to boild, this means it only takes two caps full. I used this as a standard because it is easy to measure in the field.

Now to convert it to weight, well that is a little more math. Alcohol weighs .82 ounces per fluid ounce, so a 12 ounce bottle of fuel weighs 0.9 ounces (for the bottle) and 9.85 ounces for the fuel, or 10.75 ounces total. A 12 ounce bottle of fuel is really 355 ml, so that is almost 60 caps filled. That means with my stove I can boil 30 meals, or boil and simmer 20 meals. Honestly a 12 ounce bottle will last me about 1.5 to 2 weeks of hiking.

[Kerosene]

Here's a good on-line calculator that will help you convert those ml to ounces, and much more!

http://www.onlineconversion.com/

[highway]

Kerosene:
Here is the best one I have found:

http://www.convertit.com/Go/ConvertI.../Converter.ASP

But, the problem I see is converting a measure of volume(mililiters) to a measure of weight(ounces avoirdupois or weight ounces) as opposed to volumetric ounces(fluid ounces). The problem in these tests is they are mixed and confusing. On the one hand the weights for the stove are, by necessity, given in weight ounces, which we can all understand. But the alcohol consumption is given in ml, which is difficult to grasp and not readible convertible. I have done some trangia tests and weighed the alcohol consumed on a balance to get weight ounces, as opposed to measuring the volume(metric[ml] or English [fl oz])because what is important is the weight carried for the alcohol to be consumed, not the volume carried for the same alcohol. So, since the weight of the consumed alcohol is appropriate, I have attempted to convert and am having difficulty!

A mind is a terrible thing to waste.

[SGT Rock]

Well in my case, I measure the amount I burn by volume, so I track it that way. I don't try to determine weight until I know how much I need for the trip, then I just multiply by .82 and have my answer.

If I were to calculate it by weight, then I need about .32 ounces to boil and about .16 ounces to simmer. I'm still testing the stove to make sure there are no flukes in the results. So far I've only tried the 6ml test (.16 ounce) once but was amazed by the results. I could really care less if it simmers though, I'm only interested in boiling.

Anyway, my goal this entire process is to equal or beat the Trangia which I've found the be the best stove for fuel econemy, but not weight economy since the base weight is so high. If I can get it to the point it boils as well and consistantly as the Trangia with a low base weight, I'll be happy.

If you really want to get math intensive I can give you a bunch of figures to show why I should be able to boil a pint on 9ml of fuel.

[highway]

I swear I hate mathematics. I have always been challenged in that arena. But I do struggle and try, though, to decipher everyone I find. I need to ponder it some more; its most likely not as significant as, at first glance, appears.

But damn, a stove weighing 0.30 oz. What did you make it out of, fairy wings?

[SGT Rock]

Actually it's made from a couple of grape juice cans. Here is a URL, but the data is way from complete. It's currently more an article on what I'm doing and experimenting with. Some of the numbers are WAY out there because I'm still tweaking the design. The final tests and article are likely to look different.

http://hikinghq.net/sgt_stove/ion_stove.html

Promise not to take it all as total fact yet. I've also got some pictures comming.

[EarlyRiser]

ah high school chemistry, conversions between english and metric how i loathe thee. i grew up learning metric because thats what they are trying to teach in schools now so i guess i have a bit easyer time grasping it. but i mean we all know how big a liter is because its about the volume of a nalgene a mililiter is one onehundredth of a liter. a liter is a decimeter cubed and a mililiter is a centimeter cubed. think of it as a box which each side of the box being divided into one hundred sections (ten along each side) the large box is a liter the smaller are each a mililiter. and then to convert to weight youd have to find out the weight per liter of whatever substance you are using in the case of alcohol i believe it was said that it was .82 ounces per fluid ounce and theres all the conversions and everything so yes it does get confusing and if this helps anyone than awesome i really did learn somthing in chemistry.

[slabfoot]

Sgt. Rock

Saw your post and ran rite out to the garage and made one. of course I did not follow your instructions exactly, so it cooks like a blowtorch but won't do the simmer gig. Difference was I packed in the insulation fairly dense and made 32 holes high on the burner rim with the tip of an exackto blade. boils very nicely though but I have probly lost a lot of efficiency.

[SGT Rock]

The burner holes are the big difference in your stove and mine. If you get a chance to try making it with the loose fiberglass and low hole numbers the performance will supprise you, although be prepared to wait about 13 minutes or so to achive boil. Mine is the exact oposite of a blow torch, and that is exactly what I'm looking for.

[slabfoot]

I just finished a new micro wid only 8 holes and loose pack on the fiberglass. took 3 capfuls to acheive boil about 9 minutes and still does not simmer. I think the problem is that i'm using a Kevin S. windscreen/potstand cut for good boil time on my shrunkened pepsi stove. It sets the pot above v8 micro to 1 inch. of clearance. Ican only do so much here at my desk, but I am going to try it at 3/4 and 1/2 inch clearances to see if I can't get the efficiency and the simmer effect. I am driving the guys here at work crazy since I keep borrowing time in the welding booth to do my tests.

[EarlyRiser]

just like the ion engine nasa uses. it only produces about as much thrust as the weight of a piece of paper on your hand but it can accelerate to tremendous speeds efficiently. slow but steady wins the race right? i dont mind waiting a few minutes for my water anyway, i can sit back and relax or even do a few things around camp.

[SGT Rock]

Exactly Early Riser. The whole aim in lightweight hiking is efficiency of weight.

I figured using methyl alcohol, you would only need 9 ml (theoreticly) to boil a 60 degree F. pint of water. This would be the optimal stove.

How did I figure that?

Methyl alcohol has 10,200 BTUs per pound. A pound of alcohol is 19.5 fluid ounces, or about 585 ml.

A BTU is the energy required to raise the temperature of 1 pound of water 1 degree. A pint of water is about 16.7 ounces, or slightly over a pound.

So a 60 degree pint of water needs to be raised 152 degrees to boil. That means 152 BTUs are needed.

Divide 10,200 BTUs by 585 ml, and you get 17.5 BTUs per ml. Divide 152 degrees by 17 (to make it easy) and you get a result of 9 ml.

So if a stove is 100% efficient, it could boil a pint of 60 degree water with 9 ml methyl alcohol. Mine takes 12 ml, making it about 75% efficient.

A Trangia Westwind, in comparison, is about 60% efficient.

To show a comparison, a propane/butane stove has 25,000 BTUs per pound. Using the same math, it should take about 0.097 ounces of fuel to achive boil if its 100% efficient. The SnowPeak Giga stove actually needs .29 ounces, so it is about 33% efficient. If you take the mass of fuel my stove now uses, it needs only slightly more mass (.03-.08 ounces) of fuel to work than a canister stove despite the canister stove's higher BTU fuel.

Anyway. This may bore some of you or be over your heads. But to me it is a pretty exciting breakthrough. If it works as I hope it does on the trail, I've found my perfect stove.

[chris]

I am truly impressed by the science that is taking place in this thread! Although not directly related to the spririt of this thread, I do have a question about stove performance. I currently use the lower third of a beer can with some fiberglass insulation in it for a stove. Works fine. Fairly fuel effecient and reasonably fast. My question is, how much insulation is optimal for fuel effeciency? Loosely put it? Tightly packed? Happy medium? My guess would be that the more insulation, the better fuel economy but the lower heat output. I would also guess that SGT. Rock knows the answer to this question.

[SGT Rock]

Different stoves have different requirements, so there isn't a one size fits all rule.

But with a can stove like your using, I reccomend loosely packed for all aplications.

See, the fiberglass does do some wicking, so it actually reduces the amount of fuel standing in the center where you prime it. The benifit to this is it takes less time to boil the alcohol. When the fuel starts to boil, it vaporizes better and burns evenly. If you ever pay attention to the stove while it's burning you can actually here the alcohol boil.

Another benifit to the fiberglass wicking is it gets the fuel into the inner wall where it needs to be. Unce the alcohol vaporizes in a double wall stove, it takes time to transfer to the borner holes. By wicking the fuel to the outside walls, you speed this process. Depending on how well you pack the stove, you can see this happen within seconds of lighting it.

The third benifit that is hard to show unless you build a cat stove is the way fiberflass insulation acts when burned. It doesn't actually burn, but it can glow like a very dim lantern mantel. This helps to speed the heating of the alcohol, especially in cold weather. This really helps when using the stove in cold weather. Another trick I've found that helps is to put an insuator under the stove when using it in cold weather, but that is a whole nother thread.

But if you pack the insulation too tight, you either get all the fuel wicking into the walls and none is left to prime (this has happened to me) or you pack them so full that you clog the inner wall up too much.

[chris]

As I have a surplus of beer cans laying around, I think it is time for an experiment! Thanks for the answers.

[EarlyRiser]

you let us know if that stove of yours works, cause that sounds like a great lightweight stove. i dont currently own one so id much rather make one than to go out and buy a new one. especialy if itll save me weight (and from the looks of it, a lot of weight)

[SGT Rock]

I'm working on getting a trip going now. I'm thinking Ozark Mountains around Columbus day. I actually have three stoves that need a trail test:

Turbo V8 Micro
Trangia
Brasslite Solo

On top of that I have a Clark Hammock I need to trail test some more, another Hennessy on the way, and a new LED on the way.

Brfore ya'll get the wrong impression about me, I do not consider myself a gear head, I'm just a devil about the details. The funny part is I don't like to think about gear while I'm on the trail. I want to enjoy the hike. So I do a lot of preliminary testing here at home and get some ideas about things to try while hiking, then I go have fun.

It's like this. I hike all day, enjoying the trail and nature, friends and/or family, breeze in my face or ants carrying stuff across the trail, etc. Then its: "Oh by the way I need to cook my dinner tonight!" so I get a 7-15 minute test done, then it's back to watching stars, playing in the creek, hiking side trials, or taking a nap.

It ain't all about the gear, it is the hike. The gear is a means to an end.