View Full Version : Pepsi Can Stove Optimization
I recently completed an Optimization Study on Scott Henderson's Pepsi Can Stove that you might be interested in. I won't bore you with the details (email me for the complete study), but I found out that by adding insulation material between the inner and outer walls, that the boiling time for 2 cups of 40 degree water was improved by 70 seconds! In addition, by increasing the hole diameter from .028" to .040" improved the boiling time by 13 seconds. And finally, by increasing the number of holes from 16 to 24 to 32 improved the boiling times by 8 seconds. Has anyone found similar results? Any questions or comments would be greatly appreciated!
I didn't know the insulation had all that much of an effect
As for the hole size, you may be making the stove less efficient or it may not have much of an effect on anything. try testing the stove with varying hole sizes and consistent fuel amounts and see which hole size is really better. fewer holes that are bigger may work (see Sgt. Rock's ion stove it works really well and is compact and light)
Thanks for the reply! The testing that I have done took into account
Hole Diameter, Hole number, and with and without the Fiberglass. I used 1 oz of fuel for all 24 controlled tests, using a Design of Experiments Statistical Testing technique. I stand by the results, as well as my Six Sigma Black Belt consultant(sorry, its the engineer in me). If you are interested, I would be happy to email you the data in Microsoft Excel.
I also did another analysis on efficiency, and found out that the largest diameter holes with the smallest number (.040" diam X 16 holes with the fiberglass) boiled the 2 cups of 40 degree water with the least amount of fuel (17.2 ml). The least amount of fuel used without the fiberglass was 19.2 ml (.028" diam X 16 holes).
Bottom line: Fiberglass does help with decreasing boil time and with efficency (using less fuel to boil water).
Once again, thanks for the reply!
Here is the data. The Sample ID Code is this:
1F = 16 Holes - .028" Hole Diameter
2F = 24 Holes - .028" Hole Diameter
3F = 32 Holes - .028" Hole Diameter
4F = 16 Holes - .040" Hole Diameter
5F = 24 Holes - .040" Hole Diameter
6F = 32 Holes - .040" Hole Diameter
I thought that making bigger holes without decreasing number of holes would make it less efficient. The vapors would be going out faster than they could be burnt so they wouldn't be entirly(almost) burnt. I will also expirment with this
I made a stove today with 8 holes punched with a 2" long paperclip( as in the Ion stove) figuring that since the can is bigger I could use more holes than the Ion and get good air to fuel mix. It worked great!! on 1oz of alcohol I melted and boiled 2 cups of hard packed snow( almost ice). after coming to a boil it continued burn for about 7 minutes. On a half oz I easily boiled 2cups of water from 50*. By the way nice charts!!!!!!!!!
My main point lately is fast always better? I've been trying to ge the boil down to the lest fuel needed without worrying how fast.I know I could make the Ion boil faster with more or bigger holes, or raising the pot support slightly.
Good research though. I like comparing two designs with one change to see what the outcome is. I think another test you should try is testing the with fiberglass and the without fiberglass at cold air/fuel temps. My experience shows that the fiberglass will have faster priming times.
Thanks for the comments. If you like charts, I got a hundred of them.
Anyway, all the data was taken in my unheated garage in Cincinnati, where the max temp in my garage during the testing was 40 degrees F. The fuel and water were stabilized to the garage temp. When it cools off later this week, I will try to test in a colder temp.
I am currently testing a theory that if you have a stove with an efficient hole pattern/hole diam, that works at a pot height of 1/2", and boils at around 8-9 minutes, that just by adjusting the pot height to around 1 1/4" and adding slightly more fuel, you could have a single stove that is efficient when you need it, and a flamethrower when you want (Boil times less than 5 minutes) by just changing your pot stand.
Wouldn't that be handy?
Actually that would. I could adjut my pot stand by about 1/8" - 1/4" by using a couple of tent pegs on the top. If it were colder, then raise the pot up and enjoy the heat.
Hog On Ice
I have been thinking of an adjustable pot stand also - the idea I had was to use a windscreen made of aluminum flashing (ie slightly more sturdy than foil) and then hang two or three U shaped pieces of wire on the top of the windscreen - the sides of the U shaped wire would have small hooks bent in the wire to catch the top of the windscreen - three or four small hooks on each side - adjust the height of the pot over the stove by adjusting which hooks are used to engage the top of the windscreen. The windscreen could have small "spacer" folds in the flashing to hold it open to 1/4 inch for air flow - see what StoveStomper does for the top part of his windscreen.
Stove Stomper's windscreen could be adapted by just putting holes at different heights at the right places along the windscreen, then insert two tent pins. Grizzly Bear sent me some pics of his new stove, the system would work well. I could post some pics on this thread if he gave me permission to do so.
I have looked at 2 ways to do the adjustable pot stand. The first way I tried was using a dryer vent and cutting an "E" slot on three sides and using coat hangers to make 2 arms for the stand. I wired them to the vent using picture hanging wire. Works great but I thought it was heavy. Then I tried the integrated stand ala Sgt. Rock, but I used gutter screen. I bent it into a "C" shape and stuck it in the center of my pepsi can stove. I have two different height ones and can "pop" either one in. Here is the photo
Okay Top - the Marines are here. Waddia need?
I was just saying how your design with the pics could show a good way to make an anjustable pot height stand with windscreen combo. Instead og you pipes, use a couple of tent pegs, but also add holes at different heights like robbybob1 was talking about.
Hey, since I'm pretty new to this forum thing, why don't you go ahead and put the photos up. I'll be glad to explain what I did, and the materials used. I did a minor modification, this morning, that increased the burner efficiency, tremendously. I'll fill in with that, after the pictures are up. Basically, what I did was "tame the flame" from the center opening, with a gadget that is introduced as soon as the outer holes ignite. It concentrates the flame into the blue (hotter) range, and keeps the yellow flames from licking up around the pan sides.
I'm going to grab a quick bite of supper, and will be back shortly.
OK, here are some pics. I like the design, just replace the pipe with tent pegs and add more holes for different burner positions:
And the parts:
Hey, they turned out pretty good. I haven't figured out how to post pictures, yet.
Yeah, the tent peg thing would certainly work. I just ordered some pegs from REI. When they come, I think I'll give that a go. Wouldn't have to carry extra rods, that way. For those of you who are interested, I built the wind-screen/bottom reflector out of aluminum dryer-vent pipe. The already pre-formed connectors at the edges, work beautifully to slide the two side-pieces together, to form a rigid, six-inch-diameter cylinder. With a system of tiny tabs around the bottom of the cylinder, the reflector-disk lays flat on the tabs, and becomes an integral part of the assembly. The can-bottom disk is also attached to the reflector, by four bent tabs, and the stove sits securely over this dome, and remains dead-center in the assembly. As you can see in the picture, it would be easy to replace the rods with tent pegs, and by adding sets of holes at different levels - voila - an adjustable-temperature Pepsi can stove - or as I've dubbed mine - "The Grizzley MINI". The whole thing - including stove - weighs only 2.3 oz., and by eliminating the need for the two rods, would come in under 2.
As I mentioned before, I added a little gem, this morning, that has really impressed me. I cut around the foot of another Pepsi can, releasing the domed bottom-disk. I drilled a 1/16" hole in the very center. I light the stove, and as soon as the alcohol begins to vaporize, and the outer holes ignite, I position the disk down over the stoves center hole. The 1/16" center-hole ignites, and the it, and the flames, all around increase in blue intensity, with just tips of yellow. I only had time to do two burn-length tests, and two boil-tests, this morning, but with very interesting results. Without the new center disk, I got a 2 minute-5 second burn on one capfull of fuel. With the disk, I got a 3 minute-10 second burn. Without the disk it took 6 minutes to get a rolling boil, starting with 16 oz. of 55 degree F water, and with the disk, and all other conditions the same the water was boiling at 5 minutes. (I have my pot bottom 3/4" from the top of the stove)
I'm going to run some more stringent tests tomorrow, and I'll let y'all know the results.
If anyone is interested, I'll be glad to write up my method for building the wind-screen/reflector assembly, along with some dimensions and drawings, and will post them here on the forum.
My favorite tent pegs are aluminum gutter nails from Lowes.
Grizzlybear, impressive part for the stove. I'll have to try that. Also do you punch your holes with the needle(as in Scott's instructions) or do you use another method?
pobbie - Actually, I've just begun playing around with this stove. The one pictured, above, is only the second one I've built, and prior to the first, I think I looked at every variation on homemade alcohol stoves, the Net has to offer. I'm not sure why, but I decided to go with Top's (SGT ROCK) suggestion - via Buddhur - of eight small knife slits, rather than punched or drilled holes. At this point, I'm not totally satisfied with the slits, and am going to experiment with holes of varying patterns and forming methods. I'm, by no means, a thermal engineer, but from what little experimentation I've done, it appears that flame-pattern is greatly affected by the regularity or irregularity of the metal surfaces of the hole, itself. I've noticed that the smoother the metal around the hole, the more evenly-burning the flame, and so far, the most consistent holes I've made, have been with a steel "map-tack". (the plastic ones have a tendency to break and drive the pin into your thumb - very painful)By tapping the pin through the aluminum, then rotating it a few times, a very clean hole can be formed. By the way, I do all my cutting with a Dremel Tool - especially around the can bottoms where the forming process has hardened the aluminum. Blood tends to clog the flame holes, and makes a helluva mess on the bench.
Another thing I noticed when I tried the "center-cap", was that I lost some of the yellow from the outer flame-tips. Since the blue flame is by far hotter, and far more efficient than the yellow, it seems that finding a way to reduce the amount of cooler, yellow, flame, will result in longer burn times, and shorter boil times. It appears to me, that equalizing the pressure between the center- chamber, and the outer chamber will "tame-the-flame", and result in more efficient use of fuel. When I was burning with the center of the stove wide open, I had a lot of wavering, yellow flame, that swirled and licked up the sides, and past the top of the pot. It was mezmerising, and pretty, but it stands-to-reason, that once the flame loses contact with the pot surface, about all you're doing is warming mosquitoes. Varying the height of the pot from the stove top, and restricting the distance of the wind-screen to the pot, both helped, but didn't appear to be nearly as effective, as what happened when I dropped my "center-cap" on the stove. Last evening, I covered the center hole in the cap, and made four smaller holes halfway between center and the outer (main) holes. The idea had struck me while I was preparing for an inspection, and in my haste, I made the holes too small. They were quite large enough to maintain constant burning, so I'm going to play with that a little bit, today.
I'd really like to hear from anyone who might be well versed in thermal and pressure dynamics, but I really think that striking a balance in pressure, between the two chambers, is the ticket to more efficient burning.
This probably seems like "much ado about nothing" to a lot of people, but, damn, it's fascinating! And, I do love to tinker. My approach is pretty much seat-of-the-pants, and, although very interested in quantification of results, am not much of a record keeper. If this tinkering results in what appears to be "significent" improvement, perhaps robbyrob1 will show us. Great charts! I've always wished I had the patience to do that, but I just can't sit still long enough.
I will incorporate the center cap in my next round of testing. I am building up 12 of my "Flying Saucer Stoves" with various hole numbers / diameters and fiberglass wicks. Do you use fiberglass in your stoves? I am interested to see if the effect is different if you use fiberglass or not. Anyway, I am also looking at pot height as well. Right now the plan is find the best hole pattern at both 1/2" height (for efficiency) and 1 1/4" (for boiling speed), and then try the center cap on the winner. Any other suggestions from the "Peanut Gallery" ? :p
PS: Lots of Charts and Photos soon!
robbyrob1 - Yes, I have used a common, pink. fiber-glass wick, mainly because it seemed to make sense to me. On the first stove, the wick was up near the holes, and I wasn't satisfied with that, so on the second (the one I am using) I kept it farther down, so as to maintain a vaporization-chamber. I think that the size of this chamber, above the wick, has a lot to do with speed of vaporization, pressure, hence flame formation, has a whole lot to do efficiency of the stove. As soon as I settle on hole-pattern and formation, I'm going to experiment with variations in wick-height.
Are we nutz - or what? I was just so utterly fascinated by the total simplicity of this stove, that I can't leave it alone. I've set a goal for myself. The three basic elements of the stove, itself (Soda can, wick, and alcohol) must not be comprimised. Variations on "only" those three, in order to reach peak efficiency, is rapidly becoming an obsession, with me. I'm sure "Top" will understand my militarily induced motivation, here. KISS (Keep It Simple, Stupid)
If somebody would explain - in detail - to this "dumb ol' Marine", how to go about attaching a photo to a post, I will post a pic of the "center-disk" I'm working with.
When you make a post, look at the bottom, about two boxes above submit repply that you hit when done. There is a box with a button beside it marked "Browse". Hit this button before finishing your post and a browser will open up that says "Chose a File" simple navigate to where the phjoto is on your computer and select it. Then finish your post by hitting the "Submit Reply" your pic will be attached.
Hey, thanks, Top. I'll try that in a few minutes. Got some "real" work to do, before I play.
AW JEEZE! I looked! How vague. "ATTACH FILE"
Don't say it, Top! I can hear you - loud and clear! I shoot good, and know how to spit-polish shoes, an' blouse trousers, 'n shine brass. Guy can't have everything, ya' know. At least I don't lock myself inside an iron target, and then run around in the open desert where everybody can see me.
I have found that fiberglass should be full inside the inner chamber of the stove, but not tightly packed.
The number (or rather surface areas) of the stove meter out how much fuel get out, so a slower burning stove will have less, faster more. But pot height also plays into this because the pot disturbs air flow. A pot normally has to be about 3/8" above the burner holes for enough space to allow the flame to breath. Less than that may work, but not in all situations. 1/2" is a god standard height for most situations, and 1" will help turn the stove into a dragster for fuel consumption. The higher up you put the stove, the more air/fuel mixing area and the bigger and hotter the flame will get, but this will also increase consumption as the stove heats up and increases vaporization of the fuel. I think adjusting pot height for air temp would be the way to go since it would be hard to add and remove hols.
As for fuel chamber size, I've been using these small cans because I've atempted to keep this as small as can absolutly gotten away with so the stove heats better, but since it keeps the stove weight and size to absolute minimum. The easiest way to do this was to fill a small juce can with 1 ounce of alcohol, give it about 1/8" over that so I could get the holes in, then make my scribe line for the Ion stove. That is how I arrived at the dimensions of the stove. The Turbo V8 can handle more fuel, but for a minimalist, 1 ounce is a gacefull plenty, typically 1/2 ounce will do everything you need in most 3 season weather.
If I got this right, a photo may appear. If I didn't, I'll try again. The say that "even a blind pig finds an acorn once-in-awhile".
Wow! Just like magic, eh?
These are of the disk I'm trying. It was cut from the bottom of a Pepsi can, using a Dremel tool cutting wheel.
SNAFU - sent the same one twice. Sorry. Here it is on the stove. I'll let you know what happens with different hole patterns.
When I first started experimenting with Pepsi stoves a couple of years ago I tried using insulation and found it did increase the effiency somewhat. My only problem was their always seemed to be unburnt residual fuel and odor. As I keep store my stove in my cookpot I was a little leery of contaminating my pot. Without insulation I get 100% burn off and hardly any leftover odor. Has anyone else experienced this and/or come up with a solution?
Prozac - Sounds like you may have had too much insulation (too tight), and the fuel couldn't all vaporize before the chamber cooled and the flame went out. I had that happen with the first one I built, but I had the chamber jammed tight with insulation.
I was also concerned about contamination of my cook-gear, and have been closing the stove into it after each use. Thus far, I've not been able to smell even a hint of left-over alcohol, and I've got a nose that can detect gas in a house down the street.. I am, however, considering the use of Everclear, as fuel, rather than denatured alcohol. I like the multi-natured aspect of "grain": stove-fuel - antiseptic - disinfectant - toilet - cleaner - mouthwash - rocket fuel - jungle juice - tick bath - and no (exceptionally) hazardous after effects. Just need to be careful that you don't "drink" all the stove-fuel.
I'd actually be more concerned about the possible effects from using galvanized hardware cloth as a pot stand. That stuff contains lead/tin, and when heated at high temperature, out-gasses, profusely.
Having worked with stained glass and lead, for many years. I got to know a lot of old guys who soldered without an exhaust fan. Some of them had trouble remembering how to unzip their fly.
Maybe because they were using Everclear as the fuel for their soldering tourch.
griz-about the knife slits in my expirience they are fine except for simmering when there is too big of a flame coming out of only one hole. Also thanks for the picture I made it wrong the first time:D
Does the part work by burning the fuel that comes out of the large centre hole in a more efficient manner? This may be why the fiberglass insulation helps (absorbs fuel and contains the vapors in the inner wall)
That could be, Top. I'm going to get some, and run some data on that. I'll letcha know how it works.
pobbie - that the way it appears to me, (more efficient burning of the fuel from the center) but I'm still not satisfied with the hole arraigement in the disk. I've been playing computer mechanic all day, today, on my daughter's machine, and haven't had a chance to fiddle with the stove.
I really made a great find at my local True Value, yesterday. Got a mini-chuck, that fits the collet of my Dremel Tool, and a set of 20 drill-bits that go from .039 down to .0135. Man, can I play with can stoves, now.
Any details on that mini-chuck? I would love to use bits that small with my Dremel. Thanx
I got the drills at our local True Value Hardware - the East's answer (along with Aubochons, in New England) to small-town chain hardwares. I'm sure you guys in Are-U-Gone have an equivalent. They'll probably all be going out of business, soon, in the wake of the mega-monsters like Home "Despot", hardware's answer to the WalMart Lunacy.
The tools are in bright red and yellow blister packs, and are made by Forney Industries of Ft. Collins, CO (Atlanta, GA; Horseheads, NY; Regina, Sask./Canada) The Forney Cat. numbers are 60239 for the drill set, and 60265 for the "Micro Chuck".
I checked the Forney website, but apparently they are a big welding and machining supply manufacturer, with the mini stuff as a satellite industry. They don't say a thing about them.
Hope this helps.
Hey, I'm sorry. I wanted to mention the price. I got the chuck, drill set, and a pack of cut-off wheels for 18-bucks. I'm not sure what the list price is. I'm a hardware and gadget junkie (I'm the Tim Allen of Big Cove Tannery), and they give me some kind of discount. When I park out front, the store owner is standing at the window drooling, and he wants to keep me happy. The list can't be much more than what I paid.
I truly appreciate all of the information. Are-U-Gone still has at least one True-Value, so I'll be off for some Sat. morn shopping. I too am a bit of gadget junkie. If it's bright, shiny and involves gears...Must have.:D
I have used the small chuck in a dremel to drill the holes, but I use a large darning needle. Grind it flat on one side and it will burn/drill it's way through. You can adjust the size of the hole by how far in to the can you push it.
Originally posted by GrizzlyBear
I'd actually be more concerned about the possible effects from using galvanized hardware cloth as a pot stand. That stuff contains lead/tin, and when heated at high temperature, out-gasses, profusely.
I wouldn't be too worried. the galvanic process uses no lead or tin (just zinc) and the base metal is welded mild steel. now if you were using copper or brass mesh, then i'd be worried. that stuff is soldered.
GrizzlyBear: The everclear idea is a good one, considering the poisonous nature of methyl. However, I've found no reasonably inexpensive way of buying ethyl alcohol. Everclear (pure grain, etc) is quite expensive unless maybe you've got close connections with certain people in questionable occupations. I live in central Kentucky and though I've heard from reliable sources that a few people continue to operate stills up in the "mountains" of eastern Kentucky, I don't know any of these people personally. I would very much like to have such a supply of high-grade ethyl alcohol, since I have no intention to illegally use it as untaxed liquor. Ethyl alcohol is simply a safer substance and has definite multi-use advantages over methyl.
I will mention that methyl is claimed to have better cold-weather performance than ethyl due to its higher vapor pressure. However, this isn't much consolation when you go blind from methyl alcohol poisoning. I'm currently using 100% methyl (HEET), because it is the least expensive fuel I can find, but I will very likely be switching to denatured even though it costs a bit more. <20% methyl seems safer than 100%. Maybe I can make my own moonshine still... :rolleyes:
I know that ethyl alcohol is safer as it isn't poisonous(methyl alcohol,I think, can be absorbed thru the skin). I find myself wondering if it just wouldn't be better to be careful than spend so much more money. Also I don't know if I could carry a bottle of Everclear in scouts(for stove and medicinal reasons only:D)
Der Eismann-Sprechen Sie Deutsch?
kank...i found a gallon of denatured alcohol for 7.99 at home depot. How much do u get HEET for!?!?
Actually, $7.99 per gallon is not much more than I pay for HEET at Walmart. I pay about 5 1/2 cents per floz. for HEET while you paid about 6 1/4 cents per floz. for denatured. I hope my math was right (I recently paid $2.62 for 48floz of yellow HEET in a 4-pack of 12oz bottles).
Alcohol is so good at wicking (there's a scientific word for this that I simply can't think of) that it tends to get onto my fingers even when I am as careful as possible. At my house, I quickly wash my hands each time I screw the cap back on my fuel bottle, but in camp that isn't always so easy. I am looking at improving this process somehow to better avoid skin exposure, but I think it's a good idea to use denatured to begin with (though it is still dangerous). I plan to buy denatured next time I need fuel. I'm not really sure just how easily methyl is absorbed through the skin and I have no idea how much of the stuff is required to become a health hazard. I just figure its worth avoiding exposure whenever possible.
7.99 for a gallon????? I pay 3.59 a quart! I'll have to look around, but since I live in a small town there isn't much to shop around. or I'll just use heet.
Anyone know which alcohol performs better,because I don't have any problem with spilling fuel(my fuel measure has a handle on it, so my hand is away from where I am pouring)
Heet is pure methyl alcohol, denatured is a mix of ethyl and methyl. Ethyl alcohol has more BTUs per pound than methyl, so the higher the ethyl alcohol content, the more energy per ounce. Thus denatured SHOULD give you better performance.
So there actually is a benifit of all local hardware stores going out of buisness b\c of lowes and HD- cheap denatured alcohol..can anyone think of anything else?:rolleyes:
As Sgt Rock noted, ethyl should burn hotter due to its slightly higher btu content. However, it is my understanding that methyl should provide better cold-weather performance (vaporizes easier than ethyl). I have neither personally tested nor do I know of tests intended to compare the two types, so I cannot say whether either factor is substantial enough to notice in real world usage.
re: Stove optimization:
I look forward to further test results concerning these stoves, because my examples cannot approach the levels of performance indicated by Sgt Rock and others. However, I am getting proficient at building them ;). As of now, my best performance is reaching a true boil with just over 20mL of fuel. I very much hope to get down to 15mL/boil. Even a small efficiency gain makes a substantial percentage difference in fuel weight when you get down below 20mL/boil.
20ml ain't bad at all.
Sarge I may be wrong but I am sure that I read somewhere that HEET is 80% Methyl Alcohol "spinked" with 20% Ethyl Alcohol and that is why it makes a better gas-line antifreeze than straight Denatured alcohol - and why it burns hotter in our alcohol stoves than straight methly alcohol.
Anybody else come across that reference??
I wrote the company that makes HEET, it is 99% pure methyl alcohol. The other 1% they didn't say.
Denatured was normally almost pure ethyl with some methyl added so it didn't fall under alcohol beverage taxes. Each manufacturer is slightly different as to what percentage they use, but the SLX bran is currently 50/50.
Most companies have their MSDS sheets available on the internet to make companies labeling of their hazmat easier. The good news is by doing a web search for MSDS denatured alcohol you can find some of the manufacturers, especially if you include the company name. I just did one and found one for Syndel that is 16% methyl and 83% ethyl.
Here is the MSDS for HEET in the yellow bottle: http://www.imperialinc.com/msds0055060.shtml
And here is the MSDS for Zip Strip brand denatured alcohol available at the PX: http://www.starbronze.com/pdfs/763.pdf
Now that all that is said, I have heard from people that they have slightly better performance from straight HEET than from ethyl alcohol or denatured. I don't know how they arrived at that - maybe the data isn't scientific enough to bear any real consideration. But if it is true, it would be interesting to figure out why. And if so, is the difference that much to make it important.
I tried isopropyl alcohol once because it has a lot more BTUs per pound than either methyl or ethyl, but the flame was too much, and the soot was incredible compared to the others. I would not reccomend isopropyl unless under a real supply emergency and that was all that was available. You can get isopropyl in 90% pure form at pharmacies, and 99% pure form in ISO HEET and Costal brand fuel line de-icer.
Correction, Coastal is methyl, my bad.
Another update, the article I found that said SLX brand was 50/50 was wrong. According to the MSDS it is 5% methyl and 95% ethyl.
The reason for the isopropanol not burning cleanly is that it requires more oxygen to burn clean than ethanol or methanol.
Pobbie, you are probably right, but I think the amount of ar required would make a larger than needed flame for backpacking cooking. Probably a good idea to use methyl or ethyl.
Ja. Spent almost 10 years in Deutchland. Miss that beer und Die Fraulein.
Cheers and Beers
If you want to get pure ethanol you might want to check out lab supply companies. They MIGHT sell it liquor tax free because of it being made pure for lab use only. As for isopropanol I would imagine that you could cut down on amount of fuel and increas air but I am pretty sure that a pepsi style stove would not work. I think I'll just stick to ethanol.
Der Eismann- Wo in Deutschland? Mein Bruder wird nach Deutschland im Juni gehen. Ich werde in einige Jahre gehen. Das beir schmeckt sehr gut.:D
I got the wild hair to try isopropyl alcohol in the stoves and see what happened. Well, Well! Some very interesting things.
1) With the Iso-Heet, I was able to get a true boil in less than 4 minutes (3:55 to be exact) with 1/2 oz of Iso-Heet.
-BUT- It took a while to clean all of the soot off of the pot,
I melted a hole in my stove liner windscreen, and I am afraid that I permanently damaged the stove. I got some serious heat damage (Discoloration) to the stove. I am afraid I "smoked" it! The flames over the pot were 18" easy! (Not for the faint of heart)
I have been trying to use smaller and fewer holes and closer to the pot, and it seems to be helping the sooting some. I am also going to try to turn the windscreen upside down (vent holes on top) to cut down on the airflow and see what happens.
Word to the wise: BE CAREFUL! :eek:
I chcked at school and the stuff we got is denatured but is 95% pure so This stuff from the lab supply company may be more expensive so I don't know if it would be worth it for only slightly better alcohol.
Also with isopropanol you actually might want to try making a stove out of heavier cans. I once saw some cans of juice that were steel cans and were about as thick as regular cans. You're on the right track robbybob since isopropanol is higher powered there needs to be less vapor to air so it can have a chance to burn completly and under control. :D
Hey, you guys are getting scarey! You intending to cook with these things - or launch them into space? Pleeze don't anybody try acetone. You're starting to sound like my buddy and me, when we were kids. "Hey, Bill - Let's see if this stuff'll explode?!"
Must be "stove day" around the Country. I got sick of working on taxes, real early, and have been playing with stoves, since. I re-built my wind-screen/reflector, to reduce the pot-to-screen distance to 1/4". I'm going to now put a step of holes for tent pegs, in the screen, so I can adjust pot height from 3/8" to an inch or so in 1/4" increments. Then I'm going to build a couple of new stoves with different hole sizes, placement, and number.
I may run into town before the coming blizzard. Pick up some Super-Hi-Test. Mix it with some acetone and moonshine. See if I can blow this sucker to pieces.
***### - For any kids, or others who may be watching in --- For God's sake - DON'T TRY ANY OF THAT STUFF!!!! I'm only joking with these other stove junkies! - ###***
What a day to test stoves, here in the mountains of south-central Pennsylvania. 12 degrees F; snowing like a bandit, and blizzard conditions predicted by nightfall.
I just finished some real-weather testing of my modified Grizzly MINI, and am quite happy with the results. Here are a couple of pics of the beast I tested:
PIC #3 - Test Results, next post
I used the same design for my windscreen, as in previous posts,with certain modifications: Screen diameter was reduced to allow 1/4" space between screen walls, and pot - a la Sgt. Rock; bottom vent-holes were reduced to 16 (initially) but stove would extinguish when pot was placed on rack, so I increased the number of holes to 24 - BINGO; pot bottom was reduced to 1/2" from stoves top ridge (suspended by tent pegs in holes in wind-screen); screen top is 1-1/8" from top of pot, with 1/4" notch, for pot handle; stove was made with 16 evenly spaced holes of .040" diameter, drilled at the very bottom of the stove's top ridge.
The insulation (wick) I used is new stuff I found at True Value. It is fiber-glass "pipe wrap" insulation that is called "Frost King", made by Thermwell Products out of Sparks, Nevada. The stuff is a "consistent" 1/2" before compressing. I cut it 1-1/2" wide, and just long enough that the ends jam somewhat tightly, when wrapped around the center cylinder. This width fits snuggly against the interior stove bottom, and extends just to the to the top of the side-wall, where the bend toward the center of the stove, begins.
FIRST TEST -
Tested outside (Air Temp = 12 degrees F - no wind) with the denatured alcohol at inside room temp (appx. 70 F)
First thing I did was pack my SnowPeak Titanium pot, to the top, (700 ml)with snow. I then poured 4 soda bottle caps of alcohol (24 oz. Pepsi)into the stove, and lit it. You have to wait until the flames from the outside holes are healthy, before putting the center-cap on, or they will go out. As soon as the center cap was in place, I sat the pot of snow on the rack, and started timing. The pot was covered with the lid/frying pan, except during several quick peeks to ascertain heating activity, inside. Here are the results:
Snow had melted and reached a rolling boil in 4 min. - 38 sec. (Preheat time was 40 sec., before center cap was placed) I removed the pot from the stove, within a few seconds of boiling, since the inside of my pot, above water-line, was beginning to discolor. My total burn-time - including pre-heat - was 8 min. - 28 sec.
SECOND TEST - Air temp. still at 12 degrees - no wind.
I left everything outside (stove, wind-screen, alcohol, and 500 ml. of water, in the 700 ml. pan)sitting on a cast-iron wood-stove top, until there was approximately 3/16" of ice on the water, before starting the test.
I had a little trouble getting the alcohol to light (4 capsfull), needing to leave the match in the stove, (didn't want to vaporize at 12 degrees) lengthening pre-heat time to 61 sec., before introducing center cap, and positioning pot of water with ice. Lid was left on pot until I could hear the beginning of boil, then returned, immediately, until water was boiling out under lid edges. The lid was then removed, and the pot left in position, on the stove, until the end of the burn.
Here are the results (which I consider rather impressive, for my needs, anyway):
61 sec. pre-heat, until pot was set on stove-rack
12 min. - 0 sec (including pre-heat time - I did hold pot near top of wind-screen, during pre-heat) until water was at a rolling boil!
14 min. - 57 sec. TOTAL BURN TIME on 4 capsfull of denatured alcohol, until the final, tiny, plume of flame flickered out.
I had absolutely no yellow flame, as long as the pot was in position. Apparently, the wind-screen, bottom-hole,number/size/placement, to the "gap-around-pot" ("Top's" [Thats "First Sergeant" for you non-Marines] finding)ratio, must be pretty close to right. You can see from the consistent wind-screen discoloration, in the photos, that there was a very even burn.
I intend to try a few more sets of holes at different pot-rack elevations, and I'm wondering if those will require a complementary reduction in the wind-screen bottom holes. Hmmmm
Has anybody seen the stove for sale on e-bay? Search: "Ultra Light Alcohol Stove". There's a nice movie clip, it takes a while to download but neat to see. Nice paint job.
The experience shared by robbybob1 piqued my curiosity concerning isopropyl. Does anybody here have the edumacational knowledge to explain whether it is possible for isopropyl to burn cleanly in a simple stove of the proper design? My understanding is that the soot cannot be avoided, but why does it soot so badly?
If isopropyl could somehow be made to burn more cleanly, it would make an excellent fuel for backpacking. The stove and perhaps pot support would need to be heavier gauge metal in order to deal with the increased heat, but this could be offset by the lower fuel weight. After all, a "pepsi can" alcohol stove itself is nearly weightless when compared to the fuel required for a multi-day trip.
Are there dangers other than soot when burning isopropyl alcohol? A sooted pot may not be such a horrible thing if it didn't get all over your other gear, but I wouldn't want to inhale dangerous fumes or anything like that.
Hey, isopropyl alcohol is being used as rocket fuel (http://www.space.com/businesstechnology/technology/rocket_plane_011113.html) these days, so I figure it's worth a look. Some people do seem to use it as backpacking stove fuel, but they typically seem to use hardier stoves and simply put up with the soot.
Has anybody seen the stove for sale on e-bay? Search: "Ultra Light Alcohol Stove". There's a nice movie clip, it takes a while to download but neat to see. Nice paint job.
Theres NO way that you can light the stove and have the fuel sprout of the holes that fast. There are 2 explanations to this
a) the cut off about 1 min of the time
b) he poured already BOILING fuel into a preheated 500 degree stove, and it took 4 secs to vaporize.
Yes it is possible the key is fuel to air mix. the isopropanol (as it has more carbon to it) burns sooty if not burnt completly.
griz what in the heck are you burning???? I have had the same oven liner foil screen for a year and no discoloration
pobbie - I'm just using the same old regular denatured alcohol from True Value Hardware, that I used with my first couple of stoves. I didn't get any discoloration, either, until I reduced the size of the space between the wind-screen and the pot, to 1/4", and reduced the number of holes at the bottom of the screen. I, too, was amazed at the discoloration, but just passed it off as pushing the envelope of maximum BTUs from the fuel. I tried an aluminum disk with a hole in the center (donut style), with a quarter-inch space to the windscreen, in an attempt to focus the flames on the bottom of my little espresso maker, rather than have them lap up around the pot and cup. The thing (the disk of the same material as the wind-screen)melted down around the tent-stakes and stove, about two minutes into the burn. It was quite impressive! Aluminum free-form sclupture.
yesterday I tested a stove that could boil a quart of water on less than an ounce of fuel. Temp was 15* at best w/ a 10-15 mph wind. lit and primed quite quickly despite cold.weight unknown but I'd say less than .75 oz
Construction: pepsi cans with fiberglass according to scott h. except burner holes. his burner hole configuration is (in my expirience) less than 50% efficient and hard to make as there is alot of tiny hole punching and with the fiberglass, when the holes plug, I don't want to clear 30 some tiny holes when I'm freezing my butt off on the side of a mountain. I used a larger needle and punched 18 holes( this is the best out of several stoves that I have tested) the reason for the 18 holes is that I find that simmering is done better with smaller holes i.e. better control. I could have made it out of grape juice cans/red bull (gotta love that stuff) but I figure with the larger can I can boil faster because I can release more fuel at one time (yes a very small amount but...) and still have good fuel to air mix(more distance between burner holes) also I didn't have the cans:D
Pobbie - Not familiar with scott h stove. Is the configuration basically the same as other Pepsi can stoves? Holes around the outside of the ridge. What have you done differently - other than the 18 holes - to bump the efficiency so much?
griz- I filled the gap with fiberglass and use the disk that you came up with. Regarding the holes the 18 holes are larger than in scott h's but with better spacing thereby getting better airflow between holes (in his the holes are way too close to burn the vapor efficiently) thats all I did
BTW are you able to slide the top can over the bottom with out slits? the reason for my asking is I'm running low on JB weld:D
Pobbie - I've been so wrapped up "trying" to do my own taxes, and some other things, that I haven't done a thing with stoves, for some time, but there is something I've been wanting to try.
Have you ever seen a "crimping tool", that is used by sheet-metal workers, to reduce the diameter at the end of one pipe, so that it will fit into another pipe of the same diameter? (Lay your index finger between the index finger and second finger of your other hand, and move the singel index finger up-and-down between the other two) I'm thinking of gluing two pieces of coat hanger wire to one jaw of a plier, and one piece - centered between them - on the other jaw, so that when the jaws come together, the one will pass between the other two, forming a miniature crimping tool. By using this tool to crimp, judiciously, around the edge of the top can, it will reduce the edge diameter. This should alloy the top to start into the bottom, easily. I'm not sure if forcing the two together will be a problem, but if it appears to be, I'm going to attempt heating the bottom, slightly, on a stove burner, or with a torch, and maybe chilling the top piece with an ice cube. Such a fit, would surely never come apart, or leak fuel.
Pobbie - When you say "fill" with fiberglass, do you mean the entire outer chamber - to the holes? I've been allowing the ridge-section to be empty.
fill the gap between the two walls with the fiberglass. Yeah I've seen the crimping tools but never thought of using one for stoves as the ones I've seen would be too large and probally rip ccans to bits. also I put the top over the botom.
Hog On Ice
for crimping the bottom (inner) can I use a pair of needle nosed pliers - grip side of can and twist then move over a small amount grip and twist the other direction
Crap! I keep pushing the two halfs together too hard and splitting the top, resulting in fire everywhere but in the can, think I'll try the crimping suggestion. On a brighter note, a Dremel rotary tool and a small cut off wheel make nice clean cuts, without the need to trimm. Be gentle though, as the weak sidewalls will catch and the can will try to fly out of your hand.
Sorry to dredge up this old thread, but got an idea when I was reading it.
Sounds like being able to adjust the pot height is a good thing.
The pot is fairly heavy, though, and an adjustable support is weaker than a fixed-height support, so getting the required strength/stability adds a lot of weight.
The engineer in me notices that the burner weighs next to nothing. So rather than moving the _pot_ up and down, why not leave it at one height, and make an adjustable support for the _burner_? This could be really flimsy and still work fine. A series of "hoops" of different heights made like the inner wall of the burner might do for a first try. They could be "unlatched" and stored (even when lit) rolled up inside the burner.
Of course this means a taller (but fixed) pot support is needed so that the burner will be at max spacing when setting on the ground.
Also moving the burner maintains the relationship of the windscreen to the pot.
Perhaps getting out of the thought box: "the burner has to sit on the ground" will allow this nut to be cracked.
Originally posted by Kevbo
...The pot is fairly heavy, though, and an adjustable support is weaker than a fixed-height support, so getting the required strength/stability adds a lot of weight.
The engineer in me notices that the burner weighs next to nothing. So rather than moving the _pot_ up and down, why not leave it at one height, and make an adjustable support for the _burner_?...
I'm not sure if this was discussed in this thread or not, but some people do indeed vary their stove height rather than their pot height, at least for the purpose of testing the varying pot-to-burner distances. They typically revert to varying the pot height for their field equipment. When I am testing stove performance, I also vary the stove height by sitting it on various household items (non-flammable, of course). This makes it easy to determine obtimal pot-to-burner distances and then to incorporate those distances into your windscreen's pot support mechanism. When you move to actual field usage, I'm not so sure that it's better to move the burner rather than the pot.
The method most posters in this thread have been using to adjust their pot height is by making multiple pot-support holes in their windscreen, each pair set to a different height. These posters use aluminum poles or extra tent stakes for these supports and in some cases the tent stakes are from their tent/tarp system so that they aren't carrying any extra weight for the pot supports. I don't see that such an approach to adjusting pot height (multiple pot support holes of differing heights) compromises strength in any way and adds no weight to the system. I don't see that an adjustable support made in this manner is any weaker than a fixed support.
Another thing I notice is that I would actually be worried about having a flimsy burner support. When burning, the bulk of the weight (fuel) will be near the top of this column (if you used a cylinder for support) and it might be a bit tipsy on uneven ground (ie: anywhere otudoors). I understand that you had not fully explored a solution for a burner support and were just offering a preliminary idea. I am simply voicing my concerns with this approach. There is surely a stable method of supporting the burner at different heights.
You do have a point about the pot/windscreen relationship remaining constant with your approach. As you noted, however, varying the burner height forces the windscreen to be made at the "maximum" height. You mentioned that obtaining the strength to support the pot at varying heights adds weight to the system, yet moving the stove instead actually seems to add weight rather than reduce it. I haven't yet seen anyone's windscreen that has gained weight when they added adjustable pot height to their system. They merely made some more holes in the sides. Yes, the windscreen ends at a lower height on the pot as you move the pot higher in this system, but that is the only sacrifice that I see with that method. When people are using the burner with the maximum pot-to-burner distance, they are typically sacrificing fuel efficiency in exchange for faster boil time. They probably don't mind the reduced windscreen efficiency caused by raising the pot further out of the windscreen, since they are still achieving fairly fast boil times and obviously have the fuel to spare.
You may have a very good idea and I am in no way trying to attack you for it. You may find that you can incorporate an adjustable burner support into your system quite well and be perfectly happy with it. I'd be very interested in the resulting system. I'm merely pointing out the reasons why I remain unconvinced that moving the pot support is heavier and/or weaker than moving the burner.
Admittedly, I don't see myself adopting any method of varying the pot-to-burner distance anytime soon. It just isn't feasible with my current windscreen and I have no real need to decrease the boil time. If I eventually find a way to substantially improve fuel efficiency at the expense of an extremely long boil time, then I might try to vary the pot height by making a new windscreen similar to those discussed in this thread. At the moment, I'm satisfied with my boil times. In the meantime, keep sharing your ideas.
I stumbled upon this design which was what I was trying to make myself, but which I failed to do because I believed those who insisted that I would need to make some vertical cuts in one can to push the two cans together. This always resulted in flame leaks. My first try at this design was a bit too tall for my Esbit which I used as a pot support. I could barely make it work (about 1/8th inch distance between the burner top and the pot with the esbit closed to the 45 degree position). The next effort left about a quarter inch gap with the Esbit in its normal 90 degree position. The first effort obviously did not get enough oxygen, and it took a long time to achieve a boil. The second effort was about what the inventor suggested was optimal. Check it out at http://flappyhappy.tripod.com/cobrastove.htm. It has the simplicity of realistically being made in the field. I would like to know what people think of the design, and I would also like to know what any might know or speculate about the efficiency. I believe that I made smaller holes than the designer (except for the fill hole).
One way to make the two halves of a soda stove slide together easily is to apply some JB Weld to one half where it will come into contact with the other half. This lubes it up and makes the two halves slide together easily and then when it dries it seals out leaks and holds the stove together very well. Streamweaver
On slipping the two cans togethor:
I can't get them started togethor without splitting the outer one, crimping the inner one, or my new favorite:
I use a muffler-pipe expander tool to pre-stretch the outer can. I
already had it, for it's intended purpose. Not economical if this is the only thing you want it for, but I recall that they are available for well under $10 when Harbor Freight puts them on sale.
There is a trick to making this work. The expander is much too long
for this job, so it will try to form itself into a cone because the can is only on one end. A hose clamp around the opposite end limits this. A little coning is good because it allows the assembly to snug up as it reaches it's final position. It is easy to over-stretch the can, so some trial and error is required. I wrap a piece of paper around the can, and have a mark at the circumfrence that provides a good fit.
This only works for atmospheric (non pressurized) stoves because you can only use the expander after the center of the can has been cut out, otherwise the dome interferes with the drive bolt that sticks out of the end of the expander.
I still claim that adjusting the pot height adds weight because the way this is typically done is to use a substantial windscreen (e.g. drier vent)...The weight is not in the adjuster itself, but an indirect result of needing a heavy-duty windscreen to bear the weight of the pot, where as ovenliner is adequate when the windscreen serves a single purpose. Yes, there is something to be said for having the windscreen do double duty, and if you are already sold on the heavier windscreen then it makes sense to have the adjustibility.
Using tent stakes to support the pot is dual use only if the stakes can be spared from tent support duty while you are cooking. Since you are probably not IN a tent while cooking, the stakes might be needed to keep the tent from taking flight. If you have to carry seperate stakes for the two uses, you have some backup in case one is lost or damaged, but you are not saving weight.
I am not saying that it was easy, but I had no real trouble pushing the cans together to form the cobrastove (see my previous post for more information on the stove). I did bend the very top (1/8 of an inch or so) inward of the inner can. It does take patience to get it started, but unlike the inventor, I did not need to do any tapping once the cans started to go together. I only tried it twice, but once started, the cans were easily pressed together with the fingers of two hands. I can easily see that if you left sharp points when you bent the top of the inner can (hard to do if you just use your fingers) you may risk splitting the outer can. The author does not mention it, but I also try to flatten the bottom of the bottom can (to increase capacity) by inverting most of the concave surface with my fingers. As I said in my previous post, I like the simplicity of the design. I made both my stoves with my Swiss Army Classic knife, a push pin, a curtain hook (a slightly larger sharp thing than the push pin to adjust the holes), and several cough medicine measuring cups to score the cans at a measured height. Once made, the stoves are hardly indestructible, but they are also very far from fragile. I always carry my Classic, and it would not take too much of an outpost of civilization to acquire the other materials. On a long hike, even if I managed to destroy the cobrastove, I could probably manage to get by until I could make a new one (probably carry a few Esbit tablets).
I have some free time here but not really the ability to test the stoves well, but I made a new model sort of.
I was thinking about making a smaller cat stove to test over here, but catfood is a little scarce. So I did this:
Step 1. Get a juice can like a V8 can, cut it about 1/2" tall. Line the bottom with 1/4" deep insulation. Around the edge cut four notches about 1/8" deep. This is the burner and resivoir.
Step 2. Get a vienna sausage can, cut it to about 3/8" tall. Make a hole in the bottom the size of the small circle dented into it. then cut six notches 1/4" deep around the edge. this is the air jacket.
Step 3. Take the bottom of a coke can and cut it off at the bottom of the paint for the lable. This is the base and cold weather priming cup. If yu want to shave about .2 ounces, cut some of the center bottom out, it is useless.
Step 4. Put the burner on top of the primer cup. I need to get some super glue and make this permanent.
Step 5. The jacket is removable, when you put it on it will go to the correct position automatically.
Step 6. Make a stand. I made one from some bailing wire that has the pot 1/8" above the burner.
To use, pour the fuel into the burner and then put the air jacket on. Light it and put the stand and pot on. In cold weather, add a slight amount to the burner cup first, then light it and put the jacket on.
I don't know boil times, but it works. I also don't know weights, but it weighs about .5 ounces.
This is just a test stove. I don't know exactly how well it works, and I also think I can make this simmer by simply removing the jacket. I'll keep you updated as I have time.
I'll call it the Baghdad Cat stove or something LOL!
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