Forum Index » Make Your Own Gear » Anyone tried this pocket stove?


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Dan Yeruski
(zelph) - MLife

Locale: www.bplite.com
Re: identity of device on 03/25/2008 19:16:57 MDT Print View

That little thing is part of a catalytic generator that's used to heat kerosene vapors to a high heat in a backpacking size kerosene stove. I'll try to start a thread tommorrow showing what it looks like.

The wick wrapped around it is a primer wick to jump start the heating of the kerosene.

Ian Schumann
(freeradical) - M

Locale: Central TX
Re: Re: Re: Re: Re: CFV to fit inside pot on 03/25/2008 19:46:45 MDT Print View

Where do you get your Snapple bottles? Are they sold by a specific chain of convenience stores or gas stations? I'm afraid they may not be in my area . . . :-(

Dan Yeruski
(zelph) - MLife

Locale: www.bplite.com
Re: Re: Re: Re: Re: Re: CFV to fit inside pot on 03/25/2008 20:03:36 MDT Print View

Got all of my snapple bottles at gas stations on the freeways and tollways here in Illinois.

Ian Schumann
(freeradical) - M

Locale: Central TX
Re: Re: Re: Re: Re: Re: Re: CFV to fit inside pot on 03/25/2008 20:25:48 MDT Print View

Hmm . . . anyone in TX know if they're sold here?

If not, anybody outside my neighborhood wanna ship me some? Will pay, obviously.

JASON CUZZETTO
(cuzzettj) - MLife

Locale: NorCal - South Bay
"Anyone tried this pocket stove?" on 03/26/2008 17:37:16 MDT Print View

What about using 2-56 x ?(h) - Titanium hex head bolts as pot supports through this? It would add a little weight, but I would think it would be negligible and it 3-4 of them would make a fantastic stand.

Ian Schumann
(freeradical) - M

Locale: Central TX
Re: "Anyone tried this pocket stove?" on 03/26/2008 23:31:07 MDT Print View

I may be misunderstanding, but I think putting bolts through the stove would mean the force from a pot sitting on top would be transferred straight to the ground. This is bad for the CFV bc, as I understand it so far, we want vertical pressure to help our absorbent material transfer fuel to the periphery. The vertical pressure adds force to the existing capillarity, thus, a capillary force vaporizer.

Mark Hurd
(markhurd) - M

Locale: South Texas
6 Cups Hot H2O on 30 ml fuel on 03/27/2008 15:55:10 MDT Print View

This stove needs air!
side view CFV
I was testing it today and tried 3 different setups.

First I tested it as I have before- on top of an inverted tin can with my Heiny pot on top.
CFV on can
I was getting consistant 6 min boils with this set up. (2 cups 60 F water to 212 F measured)

Second setup was with the stove directly on a flat surface and the pot on top.flat surface CFV

flat surface CFV burn
When I put it directly on the flat surface it took 50% longer to heat 60 F water to a boil than when it was on the tin can. I was getting 6 min boils on the tin can and it took an average of 8:50 min when the stove was directly on a flat surface.

I then elevated the stove about 8mm above the surface using the top of the Heiny can.
CFV on lid
That small change in elevation allowed boil in an average of 6:30 min., almost as good as on top of the tin can.
I am assuming that the difference in the air intake patterns. The flame is about half the height on the flat as it is elevated.

I also did several tests to see what the minimum amount of iso91 needed to boil 2 cups of 60 F water. 14 ml of iso91 constantly boiled the water with about a minute of boiling after it reached 212 F. The room temp was 66 F no wind and humidity of 48%. Several tests of 10 ml got the 60 F water to 185 F which could "cook" a freezer bag meal. So in ideal conditions one could fix 6 cups of hot water on 30 ml (about 1 fluid oz) of iso91.

Next step is to field test this stove.

-Mark

Edited by markhurd on 03/27/2008 18:56:16 MDT.

Nick C.
(nixie) - F
Might favor tall skinny pots on 03/27/2008 22:16:31 MDT Print View

Fun and easy stove to build!

It seems that since the heat is transferred along the sides of the pot (instead of concentrated on the bottom) this stove design is definitely geared towards tall, skinny pots.

Trying the design with my Evernew 0.9L pot and using 14 oz of denatured alcohol (Sunnyside brand), I'm getting 60 degree F water only up to about 200 degrees (in an indoor setting). Comparing this with Mark's results I'm guessing the short sides of the Evernew pot don't provide as much surface area for the flame pattern to work with.

Michael Mangold
(mkmangold) - F
ROF and something else on 03/27/2008 22:34:56 MDT Print View

I am very blessed: I get to try out the ROF in a couple of weeks, as soon as the state parks open here in Wisconsin.
Also, my wife brought home some gourmet ice cream home called "Sheer Bliss." The steel can is about 6 inches tall and has a lid that fits VERY tightly. I tried to take a pic of it just now but my camera batteries are de-juiced. Later, if anyone is interested.

todd harper
(funnymoney) - MLife

Locale: Sunshine State
Re: ROF and something else on 03/28/2008 06:28:03 MDT Print View

Yes, please show us pics!! Thanks

Mark Hurd
(markhurd) - M

Locale: South Texas
Re: Might favor tall skinny pots on 03/28/2008 17:40:59 MDT Print View

Nixie,

You might try your Evernew 0.9L with isopropyl alcohol 91% (aka rubbing alcohol). At my local supermarket it comes in 50%, 70%, and 91%. The iso91 has slightly more heat capacity than the Sunnyside ethanol, so that might get you the extra 12 F.

-Mark

Michael Mangold
(mkmangold) - F
Re: Re: ROF and something else on 03/28/2008 17:56:23 MDT Print View

OK: about 4.5 inches high:Sheer Bliss

Michael Barber
(barber5) - F

Locale: Midwest
Re: 6 Cups Hot H2O on 30 ml fuel on 03/28/2008 22:18:37 MDT Print View

Wow Mark, 6 min boils with 1/2oz isoalc. That is fantastic. What are the metal plates you are using on top and bottom? Are they mason jar lids? I am using circles I cut out of pie tins that measure about 3 15/16" (for my heinie pot) with 15 layers of paper towel. I use 1oz of fuel to get 6 min burn times. I do have the stove elevated as you did. Is there something I can change to get your boil times on 1/2 oz of fuel? By the way, in my experiment I boiled 16oz of 57deg water in 70 deg climate. No idea the humidity.

Edited by barber5 on 03/28/2008 22:24:49 MDT.

Mike Hinsley
(ArchNemesis)

Locale: England, UK
Re: Anyone tried this pocket stove on 03/29/2008 05:20:13 MDT Print View

I've had a play with some of these ideas...

Vaseline Stove

This is a 20g pocket tub of vaseline that has been cleaned out and stuffed with glass-fibre tissue (it's like tissue paper) and then topped off with aluminium mesh.

It holds up to 19g of fuel.

I ran a simple test of weighing the stove empty, full, and after and measured the time taken to boil a large (300ml+) cup of water.

It boiled the cup in about 6 minutes (I made sure it was boiling for at least 30sec before I called it) and then weighed the stove. It had lost about 16g in weight - i.e approx. 1/2oz fuel (28g/oz).

I thought it worth revisiting the science bit of this stuff because we are all getting carried away looking for the miracle stove.

1. Alcohol that is burnt 100% efficiently will produce a certain amount of energy. You may make it burn faster or slower by stove design but the amount of energy produced will be the same.

2. This heat must be transferred into the water being boiled. Any heat that 'escapes' is lost energy.

As things stand ISTR that the most efficient stove around is probably the Caldera Cone stoves. They have tried to optimise both the burn efficiency - to ensure 100% combustion and the heat transfer efficiency by use of the cone.

Little stoves like this one are cleary getting 100% combustion because alcohol vapour can only leave the stove in one direction, cannot miss the flame and the flame is burning blue.

It might be an idea to investigate pot stands / heat shields more than stoves. It's likely to have a significant impact on fuel consumption...

Mark Hurd
(markhurd) - M

Locale: South Texas
Re: Math of isopropyl alcohol efficiency on 03/29/2008 12:47:13 MDT Print View

Ok here is the math for what it is worth

1 calorie = amt of energy to raise 1 ml of water 1 degree C.
So it will take 500 calories to raise 500 ml (2 cups or darn near) 1 degree C.
Water at 15.56 C (60 F) raised to boiling (100 C) is a change of 84.44 C.
So to heat 500 ml of water from 15.56 C to 100 C will take 500 x 84.44 = 42,220 cal = 42.22 kcal.

Isopropyl alcohol has 7.4 kcal/gm.
42.22 kcal/7.4 kcal/gm = 5.7 gm

So it should take 5.7 gm of isopropyl alcohol to boil 500 ml of 15.56 C water at 100% efficiency.

Now, isopropyl alcohol's density is roughly 0.786 gm/ ml so 5.7 gm/0.786 gm/ml = 7.25 ml

7.25 ml of isopropyl alcohol to heat 500 ml (2 cups) of 15.56 C (60 F) water to boiling under ideal conditions.

-Mark

Mark Hurd
(markhurd) - M

Locale: South Texas
Re: Re: Anyone tried this pocket stove on 03/29/2008 13:09:40 MDT Print View

Mike,

Nice stove! The whole idea of a wick stove is enjoying a renaissance. Minibulldesign.com sells several and I think Zelph actually sells a variation of your stove on his sight.

This CFV pad stove is a side burner and since it can be made out of paper towels and a couple of can lids I just find it fascinating. And this stove is pretty efficient for all of it's simplicity ( somewhere between 55-65 % by my calculations). And that is with a beer can pot which are notoriously inefficient to heat compared to a pot with a broader base.

I agree with your assessment of the Caldera Cone and I rely on mine.

Anyway the CFV pad stove just makes me smile, especiallly when I think of all the complex contraptions I've made to burn alcohol over the years.

-Mark

Mike Hinsley
(ArchNemesis)

Locale: England, UK
Anyone tried this pocket stove?" on 03/29/2008 14:50:13 MDT Print View

Mark,

Thanks!

It was a quick and dirty experiment to try the concept out. I'd bought the tin as a "it might be useful for a stove if I can work out how" about a month or two ago.

Some playing around in the kitchen suggests that this type of stove works well with a relatively low stove-pot distance. 1-1.5" seems to be about right and did improve the efficiency.

Using a pot-stand that also acts as a bit of a windscreen also seems to help a little.

I haven't done anything yet but I'm thinking that an idealised windscreen/stand should work on a difusion principle so that air-speed is reduced as you go inwards - an outer ring with a large number of small holes and then an inner ring with a smaller number of large holes.

Transfer of heat from the stove to the pot seems to be the area most worth investigating since any stove that clean-burns alcohol is going to get the same bang for yer buck.

Time-2-boil might be a contributing factor in efficiency in the real world since minimising the exposure of the pot to cooling may improve the perceived efficiency. So, a fast-burning stove might appear more efficent than a slow burning one due to lower overall convective losses.

OBTW thanks for the math...

Mark Hurd
(markhurd) - M

Locale: South Texas
Re: Anyone tried this pocket stove?" on 03/30/2008 11:20:32 MDT Print View

Just back from an overnight camping trip and wanted to report on the CFV pad stove in the field.

Well as you might guess there are a few kinks to work out. Worst problem was the wind. Very blustery here and the stove does not do well in the wind. Lots of flare and yellow flame with the slightest breeze. I improvised several windscreen configurations with a large sheet of aluminum foil I had. None of which were entirely satisfactory. The best of the lot was basically a bowl shape with the stove sitting in the bottom.

Mike, I like your idea for a a diffusion windscreen. May need to work on this.

Overall the stove did heat water in the field and I was able to "cook" (i.e. boil water) for dinner and breakfast on about 45ml of iso91. It lights easily and you can blow it out if you need to. Will need improved windscreen for any practical use.

-Mark

Tony Beasley
(tbeasley) - MLife

Locale: Pigeon House Mt from the Castle
Re: Anyone tried this pocket stove?" on 03/30/2008 15:06:13 MDT Print View

Hi Mark,

This capillary pocket stove is interesting stuff.

I have been doing some thinking about the design, at the moment I am too busy with several other stove projects to play with my Ideas .

I noticed that you are using a piece of flat plate for the top layer, my thinking is to use some material that conducts fairly well like copper, aluminum, brass and then use a flat bottom pot, the stove top should take some of the heat from the edge and transfer to the bottom of the pot like a solid electric hot plate, it would still leave most of the flame to heat the outer edge.

I feel this idea at least needs some testing it could improve the efficiency of the stove.

Tony

Jim Colten
(jcolten) - M

Locale: MN
Re: Anyone tried this pocket stove?" on 03/30/2008 15:48:50 MDT Print View

I wait with baited breath to see where JSB or Tinny might take this idea!