Chasing the right flame gap

Discussion in 'Kitchen' started by Gadget, Jan 9, 2018.

  1. Gadget

    Gadget Thru Hiker

    To celebrate my new Ti cone, I decided to experiment to find my ideal flame gap.
    My setup is a Trangia style 1lt pan in a caldera clone, using a Starlyte style burner, made from a 30ml aluminium screwtop jar (with ceramic felt and steel mesh).
    Up 'til now I had been running it with the generally recommended 25mm flame gap, but this new cone was a bit taller, and enabled me to increase that to a maximum of 40mm.
    For the test, I used 15ml of bioethanol to bring 400ml of tapwater to a rolling boil, them let the fuel burn right out.
    I changed the flame gap by sitting the burner on a number of 5mm CF pads (under a layer of baking foil, to protect them).
    I even tried a flame gap of 60mm, by clamping the burner in my B&D Workmate and sitting the cone on the work surface (sealing the airgaps with baking foil).

    Here are the results,
    Flame Gap······Time to Rolling Boil·····Time to Flameout

    It looks like my ideal flame gap is around 35 to 40mm.
    Bears out my observations, the cooler, blue, fuel-rich flame cone was impinging more on the base of the pan at the smaller flame gap.
    Interesting to see the choking effect of the small flame gap, extending the total burn time.
    Last edited: Jan 9, 2018
    Robert P, dovidola, DodgyKnee and 5 others like this.
  2. Chiseller

    Chiseller Thru Hiker

    Excellent work Albert :pompus: :thumbsup: save fuel, save time, save weight.... What's for dinner?
  3. cathyjc

    cathyjc Thru Hiker

    Next you should test the most efficient width/size of flame (ie. the size of the burner surface) :D:D:whistling::bag:
    Gadget and edh like this.
  4. Gadget

    Gadget Thru Hiker

    Making adjustable simmer/choke as you typed!
  5. stormin'

    stormin' Ultralighter

    Different pot diameters, stoves, pot to stove distance, fuel used etc will give different readings. All dependent of each combination, what works for your particular setup will only work with your experiment. Keep trying Gadget,.
  6. Mole

    Mole Thru Hiker

    :thumbsup:Good boil times.

    For the last few cones, I've been using floor to pan of 55mm, which gives reasonable results with Starlyte and Speedster stoves (so 25:30mm and 20:35mm stove height:flame gap)

    It would be great if you were using the 'standard' 500ml(2cups), for the test then other stovies will be able to compare the times/performance easily. 15ml should boil 500ml indoors.
  7. Gadget

    Gadget Thru Hiker

    Interested you said 500ml, the stuff I was looking at was using 400ml as a standard measure.
    I shall do some 500ml boils soon (with colder water too)

    Boil times with the 30ml pot (50x20mm)....

    05:20s for 400ml of tap water with less than 15ml of fuel
    37ml of fuel burned for 17:40, bringing 800ml to a rolling boil in 09:16.
    Added another 100ml, and it took 'til 11:16 to get that back to a boil.
    Comtinued to boil it until 17:05, burning out at 17:40


    Anyways, phase two... introducing,

    Boiled 400ml of water in just over 5 minutes, then set to simmer, bubbling away nicely,

    At 39 minutes so far, still going strong!
    (on 35ml of fuel)

    continued to boil until 1hr02min, flamed out just after 1hr03min.
    Last edited: Jan 9, 2018
    Padstowe, dovidola, Teepee and 2 others like this.
  8. Gadget

    Gadget Thru Hiker

    Hence the reason I said MY ideal flame gap.... ;)
    Chiseller and Mole like this.
  9. Gadget

    Gadget Thru Hiker

    Phew, I was getting bored waiting for that to burn out.
    Lost 100ml of the original 400ml to steam over the hour.
    (despite having the lid on all the time)
    Chiseller likes this.
  10. el manana

    el manana Thru Hiker

    That Simmer Stick has the added bonus of being an excellent Pizza Peel for mice :)
    Gadget likes this.
  11. Clare

    Clare Ultralighter

    or a cat hole trowel, for the hiking mouse.
    Mole and Gadget like this.
  12. edh

    edh Thru Hiker

    I'm sure some on here would have watched an entire 1hr 2 min video....
  13. Enzo

    Enzo Thru Hiker

    I use 50mm diameter burner too, for all but my 400mm brew kit, seems to get faster boil without using any more fuel
    Mole likes this.
  14. dovidola

    dovidola Ultralighter

    Gadget, have you noticed whether the size of 'flame gap' has any effect on the amount of 'sooting' to the base/sides of the pot?
  15. Shewie

    Shewie Administrator Staff Member

    You shouldn't really get sooting with alcohol unless your setup is choking the oxygen, I've had one stove which wouldn't vapourise the fuel and would start to pool on the underside of the pan, that was fun when it started to run
    WilliamC likes this.
  16. Gadget

    Gadget Thru Hiker

    I shall have to report back on that one.
    I have been running it with a 25mm flame gap (too small it turns out), my pot is fairly blackened, but I left it on, supposed to aid heat transfer innit?
    Although, to gauge whether it blackens less with a bigger gap, I would have to clean it first.... therein lies the rub!
    WilliamC and dovidola like this.
  17. dovidola

    dovidola Ultralighter

    I use Stormin's purpose-built cone for my Evernew 900 pot, so it should be letting the optimum amount of air in. I've tried meths and bioethanol, and I get a layer of soot whichever setting I use it in. Before the cone, I just used a freestanding windshield (Vargo aluminium) which was more ventilated, and still got soot, although a little less of it. The burner is the standard (30ml) Speedster. Apart from the soot, everything's brill.
  18. dovidola

    dovidola Ultralighter

    Fair enough. Maybe I'm just being a clean freak.
  19. stormin'

    stormin' Ultralighter

    Do you use the burner supplied with the Cone?
  20. dovidola

    dovidola Ultralighter

    Tried both the supplied burner and the Speedster burner - same results. The reason I prefer the Speedster is its lid, which is lighter than the separate container which comes with the Stormin burner and does a tidier job IMO of conserving unused fuel.
  21. WilliamC

    WilliamC Thru Hiker

    A while back I did some testing on a Keg-H set up. I was getting no sooting at the standard height. I found that increasing the pot-stove distance shortened the time to boil without having a noticeable effect on efficiency but led to soot on the pot. Increasing the air holes (by quite a bit) got rid of the soot.
    Within the same pot and stove set-ups I have found that there is quite a possibility to alter pot height without much effect on the efficiency; with a 400ml boil there was generally only about a 0.5g difference in fuel use within about 20mm of difference in height. For us, that would equate to just 2g per day. There was a much bigger effect on boil time.
    The problem is it is hard to know how much home findings relate to real world practice in windy conditions.
    Last edited: Jan 11, 2018
    dovidola likes this.
  22. Gadget

    Gadget Thru Hiker

    I think fuel use would be the least of your problems with a 200mm potstand!
    Last edited: Jan 11, 2018
    WilliamC likes this.
  23. WilliamC

    WilliamC Thru Hiker

    I think fuel use would be the least of your problems with a 200mm potstand![/QUOTE]
    :) Better edit that...
  24. JimH

    JimH Ultralighter

    I added some coconut oil to my Starlyte stove ages ago (I wanted to see how it'd burn), it wasn't the greatest success, and I now get a bit of smoke/soot when it runs really low on meths as I guess there's still some coconut oil residue in there.

    The smoke is possibly useful as an indicator that it's running out of fuel, but it's not ideal!

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