Dec 30, 2011 at 10:33 am #1283508
This stove has been discussed in a couple of threads here in the past couple of weeks, but I thought I'd post a few pics and a video of it in action. Nothing special really, except it's total ease of use, simplicity in design, and it only weighs 3g.
It started out as a 12oz red bull can. The 12oz can is a smidge larger in diameter than the 8.3oz cans, allowing for a tough more fuel volume/spill resistance. I cut the can down to 1.5" tall and deburred the edge on some scotchbrite. Then I marked 12 even spaced liens with a sharpie and using a small screwdriver (anything about 1/8", 3mm for you metric folks, diameter would work) started making the inward creases on each mark, pressing while supporting the inside on either side on the mark with my fingers. Then I did the same in between each of those 12 inward creases, but pushing outwards. I first did not use the screwdriver, but this generated sharp creases that cracked before the stove reached its final shape. Using the screwdriver as a mandrel creates smooth radii. Now, I formed the stove about 50% of the way to its final shape before punching the pre-heat holes. I found that forming the stove's pleats after punching the holes ends up with a badly crumpled stove, but ymmv. You can vary the number and the up and down location of the pre-heat holes to tune the heat output of this stove to your liking. After the holes were punched I just carefully and gradually squeezed the stove between my fingers to get it to the right taper. What that is, I don't know- I just did it until it looked good.
Until now most efficient stove was my knock off of the mbd nion, but it's 12g (not that 9grams is really that much to be a deal breaker) but it's much, much, more difficult and complicated to make. It requires pressing cans together, drilling hole, inserting rivet nuts, etc… Filling it with fuel is slow and frustrating, and then it requires priming which is always hit and miss, especially in daylight. Too much priming fuel and the thing goes nuts until it burns off, too little and it goes out- and in daylight there's no easy way to know if it stayed lit…super annoying. This is a reasonably generous fill port, and all you do is light it and start cooking. IMO, this stove solve all of the issues I have with the pressurized stove I've been using, without any drawbacks.
I'm getting pretty consistent 10 – 11 min boil times on my Heineken pot, and around 13min burn times on 4tsp (2/3oz or 20ml) of fuel under controlled conditions. In super cold (about 20f) conditions it took about 17 mins to achieve a boil, but didn't need any more I always overfill a tiny bit to err on the side of caution. I think it would have performed better if I had something under the stove to insulate it from the cold ground. I'm also certain, though I haven't tested it yet, that boil times would be much faster on a larger more efficient pot.
Anyway- here are some pics…
apparently I don't know how to embed a video…so here's the link
BMDec 30, 2011 at 12:29 pm #1817573
Rusty BeaverBPL Member
Cool. Thanks for posting.Dec 30, 2011 at 12:54 pm #1817584
Thanks for posting. That's a hot flame you're getting.
So it's a single-walled stove? Just one can? Is Red Bull any thicker or something than any other 12-ounce soda can?
And the thread wrapped around your Heinken pot – is that cotton or something higher temp? For insulation while heating and/or a built-in potholder?
There are sheet metal crimpers that HVAC guys (and gals) use to make custom ductwork when the factory crimp doesn't come in the right length. I can imagine what you mean about a radiused crimper working better and if the hardware-store ductwork crimper isn't nicely radiused, a little touch on the belt sander or with a file would make it nice and smooth.Dec 30, 2011 at 1:43 pm #1817613
Yeah, just one single walled can. As far as I know, red bull cans are the same thickness as a normal soda can.
It's a 1/16" fiberglass cord from McMaster Carr. A long while back Tinny at Mini Bull Designs was wrapping his Heineken pots in it and posted a how-to. It's serves multiple uses- built in pot holder and a spare 10' of cord should the need arise. Now that I've been following your studies into the emissivity of the aluminum cans, I wonder since my windscreen goes all the way up the sides of my can, if my setup would be more efficient with less wrappign and painting more of the can black…
As for a crimping tool- I keep thinking of a tool like what they use to reload shotgun shells. You could drop in the cut down can, and pull one handle forming all the pleats one one perfect motion. But then, you are talking about hundreds of dollars, at least, of tooling to make a product that's worth a few cents? It's hardly worth the roi.
I'm a mechanical designer by trade, and have been called McGuyver and Tim Allen on occasion by my friends. My mind quickly tries coming up with methods that would improve the production my my myog projects, but when you add it all up, I'd end up spending far more than just purchasing a commercial product which in many cases would be a better product that what I could produce, especially as a novice at whatever it is I'm trying to make.
The one big exception is alcohol stoves. There's almost zero cost in materials and tools. The only think I have bought specifically for stove making is aluminum flashing and a 1/16" diameter hole punch for $7. Everything else is just stuff laying around the house. (wait- and reflectix for pot/freezer bag cozies).
BMDec 30, 2011 at 2:07 pm #1817627
For those seeing this for the first time- just wanted to clarify that this is not my original design- but inspired by a burner James Marco posted in a couple of recent threads.
And I realize I never mentioned anything about the distance between the pot and stove. I'm running the pot about 1" to 1.25" above the burner. Running it higher makes it run a little slower, lower is a touch faster, but I haven't done too many runs to form any solid data. I just figure the stove gets more thermal feedback when the pot is lower.
BMJan 5, 2012 at 10:46 am #1820170
Kevin BeedenBPL Member
;-)Jan 5, 2012 at 11:20 am #1820185
BM: Thanks for the info and answers. I'll look for some fiberglass cord. I see bigger stuff all the time as gaskets for wood stoves. Plumbers use fiberglass matts to insulate your wood framing from their torch flame (well, they should!), but you'd be left trying to secure it around a pot / wind screen.
I'd suggest painting the sides and bottom of the your pot black. Or white or whatever, since it all seems to be black in infrared. With how shiny your windscreen is, there's be a lot of IR bouncing around in there and you want those photons to land on your pot, and bounce off the windscreen.
If your alky stove is getting too much feedback within the windscreen, then shine up the stove with fine (400- or 600-grit) sandpaper and it will reflect most of the IR coming at it.
Back in the day, MSR windscreens had a bottom donut of foil bouncing radiant heat UP from below. They have a pretty broad, low stove so there was more view angle of the ground. Yours is tall and narrow so that wouldn't have much benefit.
A mod to your windscreen: You could punch more (or less) holes along the top of the windscreen since it will effect performance very little. Then if you need more air for combustion or to prevent a runaway stove in hot weather, position the end with more holes at the bottom. In cold temps (bigger chimney effect, denser air, want more thermal feedback), you put the fewer holes at the bottom.
I sometimes see the way to produce something more efficiently, but my most common "Ah hah!" moments come around heat transfer and convection (thermo-siphoning being a nice overlap of the two) and thermodynamic tweaks for better efficiency.Jan 5, 2012 at 12:15 pm #1820216
I know a good idea when I see it! The flissure joint works just as well in a cylindrical windscreen as it does on a conical one…
BMJan 5, 2012 at 12:31 pm #1820236
al bBPL Member
Perhaps you could get closer to cone performance by using the trangia idea of a pot lid wider than windshield, with a down-faced rim (eg use a foil pie/flan dish): this forces hot air to do a 180degree turn to exit.Jan 5, 2012 at 12:33 pm #1820238
"I'd suggest painting the sides and bottom of the your pot black. Or white or whatever, since it all seems to be black in infrared. With how shiny your windscreen is, there's be a lot of IR bouncing around in there and you want those photons to land on your pot, and bounce off the windscreen."
I'm definitely going to try it. I've got a spare Heineken can that I'll do up painted, and try to see if I can measure the improvement. I think I've got my test procedure pretty close to dialed for good repeatable results.
"Back in the day, MSR windscreens had a bottom donut of foil bouncing radiant heat UP from below. They have a pretty broad, low stove so there was more view angle of the ground. Yours is tall and narrow so that wouldn't have much benefit."
I have done something similar to that for a inverted downdraft wood gassifer cookset I've been playing with. The designs has been obsoleted by the discontinuation of the Heineken beer cans though… It's still something I was to develop as I have the time, which is pretty much never. If you think alcohol stove testing is slow and tedious, try wood stoves. Burn times are SO much longer, plus fuel prep time takes forever in comparison to pouring out a measured amount of some liquid.
https://lh6.googleusercontent.com/-ibQiMQQCshE/TWlOthtWrAI/AAAAAAAAAXs/nvyuBYq7J1g/s800/DSC06089_email.jpg (that is a wood fire, good old USA douglass fir)
I was trying to eliminate secondary cold air from drafting up and diluting the hot gasses coming out of the combustion chamber, while more efficiently blocking drafts with the added benefit of redirecting radiant heat at the pot (as confirmed by your experiments).
Here's a picture of the whole kit – https://lh4.googleusercontent.com/-xRFK4oig-eQ/TWlOs_arPsI/AAAAAAAAAXs/JXvhLP7RlYA/s800/DSC06084_email.jpg
"A mod to your windscreen: You could punch more (or less) holes along the top of the windscreen since it will effect performance very little. Then if you need more air for combustion or to prevent a runaway stove in hot weather, position the end with more holes at the bottom. In cold temps (bigger chimney effect, denser air, want more thermal feedback), you put the fewer holes at the bottom."
That's definitely a good idea- I'll have to consider that for my next windscreen/pot stand build. There is always a "next" build… My poor wife… sometimes when she asks me what I'm doing, I'm ashamed to tell her I'm building/testing another stove/windscreen combination.
BMJan 5, 2012 at 12:39 pm #1820244
>"The designs has been obsoleted by the discontinuation of the Heineken beer cans though… "
Darn. I was seeing all these Heinekan can designs and planning on buying a dozen (only in the interest of advancing stove science of course :-).
You know Heineken once made brown-glass beer bottles to double as building bricks? They were rectangular and had bumps / divots so they'd stack nicely. The idea was that if they were shipping all these bottles to the Third World, they might as well be useful trash.Jan 5, 2012 at 12:50 pm #1820256
Yeah, it sucks. I still browse the beer section of the supermarket hoping to find some old stock. Foster's cans are our last hope, but need ridges added to them to make them durable (I use that term loosely in regard to beer can pots).
BMJan 7, 2012 at 9:42 pm #1821542
Ultra, what is the height before you crimp the can?Jan 9, 2012 at 1:38 pm #1822258
"Ultra, what is the height before you crimp the can?"
I don't have the exact dimension of where the three holes are punched. I just go by the graphics on the can as my point of reference… If it's not clear in the photos, when I get a chance I'll grab a 12oz red bull can and measure. The 8.3oz cans are just a tiny bit smaller in diameter. Don't know how that would affect stove performance if everything else was left the same.
BMJan 9, 2012 at 3:10 pm #1822300
James MarcoBPL Member
@jamesdmarcoLocale: Finger Lakes
Actually the height, angle, number of folds, and opening size are all related.
A taller stove, given the same number of folds and the same incident angle, makes a smaller flame opening. 20 folds make too little sized air injection into the flame and loss of efficiency. 12-16 seems to work best with dulled pliers. I started playing with angling the folds slightly to produce a vortex in the flame but it did not seem to help with efficiency, it just looks cool. A smaller diameter outlet means less air is needed on the inlet side. Two holes rather than three. The smaller the flame outlet, the less air you need. Cup sized cones work well with NO air inlets. Tune these params any way you need for use in a cone. I eventually got it down to about 1/3oz for two cups of water in about 9 minutes. I remember starting at 40F and calling it "boiled" at 200F.Jan 16, 2012 at 8:31 am #1825289
How many pleats and holes did you use to reach the 9 minute mark? Does it matter whether the holes are punched on the inside versus outside pleats? (The stove I made last week is very efficient, but painfully slow to boil)
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