CHS and other Alcohol Stoves

Discussion about making bushwalking-related equipment.

CHS and other Alcohol Stoves

Postby Brekel » Mon 09 Apr, 2018 2:55 pm

I've begun experimenting with alcohol stove designs.
I always used a trangia in the past and loved it, but it "disappeared" during the course of a divorce (even though the ex doesn't bushwalk!). Rather than go out and buy a new one, I'm looking at options that might be lighter.
My main design goals are:
  • Lightweight
  • Efficient
  • Work well even when cold
  • No need to prime
  • Simple to use
I made a "supercat" first as something simple, and something to benchmark other attempts against. It worked well, efficiency was ok on the test bench (about 16ml to boil 500ml of water starting at 15°C) and when the pot was in place it burnt with a fairly clean blue flame.
The aspect I don't like are:
  • Has to run for a while to build up heat, otherwise when a cold pot of water is placed on the flame dies down to almost nothing.
  • It is very wind sensitive.
  • It is very sensitive to ground temperature

If the pot is held over the flame while warmng up you save some of the heat and fuel that would be wasted, but this adds to it being a bit fiddly. And when it's cold and breezy, you have to hold it there a long time or it will die down, then stay burning very low (one test it even went out after a couple of minutes).

Obviously a windscreen will help with wind sensitivity, but a design that was a bit less sensitive to begin with would be better. And insulating it from the ground would solve the cold issue... but again, it's more items to carry and more fiddling.

I've turned my efforts to the Capillary Hoop Stove variants designed by Tetkoba. So far I've achieved designs that work better than the Supercat, but not as good as they could be from what I read online. The main references I've looked at (other than Tetkoba's youtube videos, and some google translations of some of his blog) are the (extremely long!) Alcohol Stove thread on Appalachian Trail Cafe and some posts on WhiteBlaze, mainly contributed top by user BirdBrain.

While I can hold it on my hand for a minute or two, it does end up very hot whereas Tetkoba and others indicate it shouldn't get this hot (one of the supposed advantages).
My boil times are similar to Tetkoba's but not as quick as BirdBrain on the ATC forum gets (around 3:30 IIRC) and my fuel useage is marginally higher than BB, even though I'm using metho (95% ethanol) rather than methanol and theoretically I should use a little less.

My flame is blue at the base, but when no pot is present it is quite orange at the top indicating incomplete combustion. When a pot is in place and is low enough, it is mainly blue and there is very minimal sooting. However with the pot low it forms a bronzy-coloured film on the bottom of the pot in the centre of the flame, which again indicates products of incomplete combustion (although better than soot). Tetkoba's videos show a blue flame even without a pot in place.

I was wondering if anyone else has played with this design?

My thoughts are that a lot of what I am seeing comes down to the fuel. Tetkoba doesn't state what he uses but BirdBrain uses Methanol (Heet) and even goes so far as to state not to use 95% ethanol, which our methylated spirits is down here.

Ethanol has a higher energy content as theoretically should use slightly less fuel if it burns efficiently and completely. But this obviously also requires more oxygen, and a design optimised for maximum efficiency with methanol may require adaption for ethanol.

Also, ethanol boils at 78°C as opposed to Methanol at 64°. This means the hoop at the top necessarily needs to get 14° hotter, which will translate to a warmer base as well. The metho in the bowl at the bottom of mine is not getting hot enough to boil, so that is a good sign and my hotter temp may just be because of the fuel.

The pro's I've seen with my design over the supercat so far are:
  • The flame pattern and pressure from the jets in the top hoop make it more stable in a breeze.
  • Efficiency was slightly improved
  • No issues with the pot killing the flame (although you need a separate pot stand)
  • Consistent flame throughout the burn time until only a few seconds before it goes out.
  • Much better cold tolerance. As it is only the fuel traveling up the walls to the hoop that needs to be vaporised, the bowl being cold doesn't matter. I put alcohol in one of my stoves, placed the stove in a tray of water, and put it in the freezer until the water froze the stove in place. It still lit within a couple of seconds from a match, and bloomed in the same time as usual when warm, albeit with smaller jet flames initially.

I'm playing with a few design modifications. BirdBrain stated his opinion that 95% ethanol would need a bigger top hoop and a smaller aperture in the top of the stove, ideas I have not pursued yet.
Has anyone else played with this design? Specifically, using ethanol/metho rather than methanol? If so, I'd be keen to hear your thoughts and experiences.
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Re: CHS and other Alcohol Stoves

Postby Brekel » Mon 09 Apr, 2018 3:09 pm

Shots of a couple of versions :
IMG_20180409_150323.jpg

IMG_20180409_145727.jpg
IMG_20180409_145727.jpg (67.17 KiB) Viewed 7341 times

IMG_20180409_150042.jpg
IMG_20180409_150042.jpg (100.6 KiB) Viewed 7341 times
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Re: CHS and other Alcohol Stoves

Postby Mark F » Mon 09 Apr, 2018 3:13 pm

Sounds like you are rapidly disappearing into the zombie underworld world of diy backpacking stoves - repent now! :roll:

If you haven't found it already there are a million threads on the subject on https://backpackinglight.com/forums/forum/gear/make-your-own-gear/

On the fuel issue I would be thankful that we have a decent methylated spirits in Australia rather than hotch potch of US fuels, some of which contain quite nasty additives.
"Perfection is attained not when there is nothing more to add, but when there is nothing more to remove".
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Re: CHS and other Alcohol Stoves

Postby Brekel » Mon 09 Apr, 2018 3:20 pm

Yes, our fuel is certainly nicer. Diggers even state that none of the additives in their metho are toxic - they just taste really bad! I think it's just a matter of a slight redesign to work with the different fuel.

I'll do a search on bpl, thanks :-)
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Re: CHS and other Alcohol Stoves

Postby robbieb » Wed 06 Jun, 2018 2:44 pm

The simplest one I've come across, and can be made with a Swiss Army Knife or a pair of scissors and a single can, is the capillary stove where the jets are made from the top dimples of the capillaries which are dented into the top part of the can, stuck into the bottom part of the can. No glue, no drills, no dies, no lubricant, no aluminium tape, just a can and something sharp to cut it in half and make some capillary dimples.
The top part of the can retains its solid rolled ring which is strong enough to be its own pot support.

https://tomsbiketrip.com/how-to-turn-a- ... eed-video/

I have made a few of them and been able to boil water using methylated spirits, but as you have stated, it runs hotter. It needs a short time to cool down before you can handle it. it can deform the can slightly. It will glue the inner top piece inside the bottom piece if you leave the paint on it. But it is simple, easy and quick to make, and if it breaks or whatever, you just need another can. It lights quickly and primes easily because like Tetkoba's CHS, it is only vapourising the fuel in the capillaries.
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Re: CHS and other Alcohol Stoves

Postby ChrisJHC » Thu 07 Jun, 2018 1:37 pm

robbieb wrote:The simplest one I've come across, and can be made with a Swiss Army Knife or a pair of scissors and a single can, is the capillary stove where the jets are made from the top dimples of the capillaries which are dented into the top part of the can, stuck into the bottom part of the can. No glue, no drills, no dies, no lubricant, no aluminium tape, just a can and something sharp to cut it in half and make some capillary dimples.


I sometimes make these when I get into a campsite early. Unfortunately you can pretty much always find a soft-drink can lying around in more accessible places.

Also note that stoves made out of Diet Coke cans are much lighter than full-strength cans!
;)

I still think that a tuna-can stove is better all round.
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Re: CHS and other Alcohol Stoves

Postby robbieb » Fri 08 Jun, 2018 8:42 am

ChrisJHC wrote:Unfortunately you can pretty much always find a soft-drink can lying around in more accessible places.


Indeed. Sad that people just don't care what happens, or rather doesn't happen to their rubbish when the discard it improperly
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Re: CHS and other Alcohol Stoves

Postby Oldnslow » Wed 27 Jun, 2018 4:32 pm

Apart from making one I bought a cheap Chinese trangia for under $8 inc. Postage....
How the hell do they do it?
Brass and seems to work well.....
Yet to field test it.

Metho stove (Copy).JPG
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