Had a go at making a stove following your instructions and (as you warned could happen if care is not taken) I managed to make a hole in the inner wall whilst piercing the jet holes.
It struck me that the jet holes could be made at stage 7-8 of the instructions instead, no danger of us heavyhanded stovies putting holes where they shouldn't be then, also you would no longer need to make the cuts in the dimple as the jet holes would let the air out when mating the 2 halves. Just a suggestion.
Yes, you could make the holes at any point before mating the halves. It is likely to cause problems if you do this with 250ml red bull cans, though, as I've found the inner wall snags on punched holes; drilled holes should be okay.
Ah; I though I had a sense of deja vu...
The answer for me is to use that little stop on the pin, or a drill press to control the depth of drilling.
The cuts in the dimple are preparation for removing the dimple; the air thing is incidental.
I've since refined these steps to use a single pricked hole, just below the scored line around the dimple, followed by a single cut from this hole to near the centre of the dimple. The dimple is then removed in one piece after mating. The pricked hole allows the start point of the cut to be well-defined.
captain paranoia wrote (see)
Oops, missed that one.
Making a pinhole then cutting to the centre of the dimple makes sense, no chance of cutting too far then. Hadn't thought about the holes snagging on the inner wall, good point.
> Hadn't thought about the holes snagging on the inner wall
I hadn't either, until I discovered the problem... cue much cursing as I cut the outer can off and got out the sellotape...
I made a second stove but this time followed CPs instructions. No real problems but it is more complicated than the chimney style. It works well but the flame is really too big. I tested it outside with 1/2 litre tap water and got a rolling boil in about 6.30 min but there were flames coming round the side of the pan and soot on the base of the pan.
When burning the jets were about 2-3cm high and then there was a large central flame 15+ cm high. I couldn't determine whether this was the jets joining together or the central reservoir burning. I could also hear boiling and hissing from the burner which I have never noticed from trangia burners.
Has anyone tried making a simmer ring for these? I thought of trying with the very end section of another can. The Trangia one covers the jets and leaves the middle open but I wondered how the reverse would work. Also I wondered about making holes in the simmer ring to match the jets but fewer ie so only 4 or 8 jets worked.
Bailout, I'd suggest you look at the size of the holes you made. If they're too big, things can get a bit lively. 6.5 minutes is quick to boil 500ml.
What pan support did you use? If it was the Trangia Mini, then I suspect you're getting problems with thermal feedback to the fuel, which makes it evaporate and thus burn quicker.
The flame from the open fuel pot usually disappears when you put a pan over the burner, since it's now starved of oxygen by the surrounding ring of flame. If the flame gap was too large, this flame might continue, and thus make the stove run hotter.
The hissing you heard is probably the fuel boiling; if this happens, the vapour bubbles back into the open cup, again feeding the inner flame.
I have tried simmer rings, but they've never been too successful. Have a look at the Q&A thread, or check my photo galleries.
Twiglegs; nice tank cutter. I keep meaning to get one for wood stoves, but never seem to find a roundtuit...
That particular tool looks very suitable for cutting dimples. I use a carpenter's wood bit for cutting partial holes in dimples (I found a range of sizes in Poundland).
CP, thanks for the feedback. I think the holes may be the problem. I used a noticeboard push pin. The resulting holes are 1mm. IIRC you say 0.8 mm which isn't a big difference but x16 it will add up. I wish now that I had started with just 8 holes and then added more if needed.
For the test the stove was just placed on a concrete slab and I used a bent coat hanger pot stand. Hence there couldn't be any heat feedback to the burner other than the hot air inside the windshield. The burner was probably losing heat to the slab.
Burner -> pot base distance was 1.5". Too much?
My best results so far.
Ambient temperature 21 celcius, water from the tap. I don't have a thermometer.
Using a 16 jet stove following Kevin's simple guide but a taller stove to replicate the height of the trangia burner and the Caledera cone (again Kevin's design) which was sized for the trangia burner. (easier to make a taller stove than a new cone)
500 ml of water 5'.00" to produce the first vapour, 5.20" to get a good rolling boil. Meths consumption was 22ml.
I'm happy with these figures - do they seem about right to the experts?
> The resulting holes are 1mm. IIRC you say 0.8 mm which isn't a big difference but x16 it will add up
Area is the square of diameter, or radius, of course, so your 1mm holes are 56% bigger than my 0.8mm holes...
Try fitting a 'cork' stop on the map pin to limit the hole size.
Flame gap of 1.5" might be a little high; try adjusting (up & down). I usually use 1".
No thermal feedback. Hmmm... it is burning fast, isn't it?
> 500 ml of water 5'.00" to produce the first vapour, 5.20" to get a good rolling boil.
> Meths consumption was 22ml.
That's probably why, assuming you measured the fuel to just achieve a boil.
I can usually boil 500ml with about 15ml of fuel.
In the Clone, you're probably getting a lot of radiative feedback (heat reflected back to the burner), so the burner's running a bit hot.
The 330ml drinks can burners do seem to put out more heat than the small 250ml red bull cans.
The other way of making the burner match the Trangia burner height is to rest a shorter burner on a cut-off can cap & shoulder. The advantage of this is that it should isolate the burner from cold ground. Not that you seem to be having a problem with a cold burner...
Actually I measured out 30ml and then measured what was left - may have wasted a ml but certainly not 7.
Good tip on raising the burner.
I tried a 30mm stove in the cone but that was way too fierce, 30ml of fuel, and about a minute slower - loads of flame running up the side of the kettle.
I'll try raising the 'trangia' can stove up a bit & see if that makes it more efficient. Given my 'bodge it and see' approach to all this it may not be as tall as I intended
Sure I've got the neighbours intriqued, lighting stoves in the dark, taking pictures of stoves etc etc
I tested my insulated cup last night, using a 150ml mixer can as reference, measuring both together with a dual input K-type thermocouple thermometer with 0.1C resolution.
A not very successful result...
Starting with just boiled water, after 60 minutes, the insulated cup was at 53.3C, and the uninsulated cup at 48.4C. I'm not sure that 5C over an hour is worth all that bother. It might be more noticeable in still air.
My suspicion is that the metal:metal contact at the top of the can allows the outer can to get quite hot, and, given that it has a larger surface area, this radiates just about as much energy as the uninsulated can...
Spurred by this, I tried 440ml cans, one with a single-layer thermawrap sleeve, the other without. After 40 minutes, the insulated can was at 75.1C, uninsulated at 69C. I repeated the test adding an insulating cap, which gave 76.9C at 40 minutes, and 68.3C at 60 minutes.
Again, I'm not sure if this is worth the effort.
I suspect a cap and base insulation might have be the best compromise...
Interesting how little the difference was. I've found that the difference between single wall & twin wall mugs is pretty marked in practice (lost count of the number of enamel mugs of coffee I've had go cold in what seems like no time whilst camping, my usual camping mug now is a twin wall SS vango one and its a heck of a lot better, but weighs a ton of course)
The test for my new insulated mug was a bit less scientific than yours: Had a cup of tea in it yesterday, outer wall was pretty warm and I left it for 20 mins or so thinking it'll cool a bit in that time.....now I've got a scalded tongue, should be glad it works really.
I've been doing some tweaking.
Finally getting the implications of what CP said I made a new stove to go with the caldera cone. It was another tall one to match the trangia height but I only made 4 jets this time rather than the 16 previously.
This seems to be a much more controlled and efficient set-up.
500 ml of water at ambient temp (15 celcius), time to a good rolling boil 6'10", fuel used 18 ml
I think I may stop there otherwise I can see myself getting really into this stove malarky.
> I tested my insulated cup last night
This post should have been on the Q&A thread...
> but I only made 4 jets this time
Four jets is likely to result in continued burning from the centre, as they won't form a continuous ring of flame around the open pot.
Try a chimney burner next; this is about the most efficient but quick (7' to boil) burner I've made to date (55.8%). The most efficient burners have been an inward-pointing, conic walled red bull (10'45", 60%), and Mark Jurey's Half Penny (17'40", 62%).
A burner built as per the article (16*0.8mm holes) boiled 500ml in 6'00", but went out after 7'30", giving 53% efficiency.
All theses figures are with a Clone and MSR Titan kettle.
Cheers for the guide Captain, made the stove, took quite a while to do but it works great, I'll be running some tests in comparison to the pocket rocket and the Jetboil for DT coursework.
Back yard now stinks of meths of course!
This design is very slick and cool, but complicated. You can get similar result by:
1 - Cut off the bottoms of two cans, about 1" from the bottom for both.
2 - Poke a 3/8" hole in the centre (bottom) of one can bottom.
3 - Slide the can bottom with the hole in it over the other can bottom, so the hole is on top and the bottom of the other can bottom is on the bottom (get it??). Heat the top can and cool the bottom can to do this easier. This is the trickest part.
4 - Poke 6-10 holes along the edge of the top with a push-pin.
5 - Add alcohol or Methel-Hydrate (SP?) or whatever you're burning, fill until the level is just above the 3/8" hole.
6 - Put a penny over the hole.
7 - Light.
8 - Its good to have a stand to put a pot on - I used sheet metal, bent it into a open ended cylinder and cut out air holes.
9 - cook.
Love all the can-stove designs.
It's true that there are hundreds of different designs of drinks can burners, and the first one I ever made was exactly as you describe.
But I've found that the one I presented in the article is fairly easy to make, and works every time. Burners as you describe are sometimes a pain to prime & get burning; I built mine the opposite way to yours, so that the lower can is the outside. If you make the lower can slightly taller than the inner can, this provides a lip that can be used to contain some fuel to prime the burner.
> fill until the level is just above the 3/8" hole.
That means you have to put a lot of fuel in the burner; most meths burner users are lightweight freaks, and we measure the meths out to match what we're cooking.
If you've not already seen it, have a look at the 'How to make meths stoves Q&A' thread, linked to in the article.
'Methyl hydrate' is more commonly known as methanol.
The simplest burner is simply to cut the bottom off one can; job done (the open pot burner).
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