Brit military No.2 (modified) reappraisal

Discussion in 'Stove Forum' started by presscall, Oct 27, 2019.

  1. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    I once composed a critical (well, tongue-in-cheek) post on military No.2 stoves - the roarer type and later ‘modified’ version with a silent burner ... saying goodbye to No.2’s

    Subsequently CCS contributor BernieDawg undertook a modification on a No.2 burner to improve its capacity to ingest a greater proportion of air with its fuel, enhancing its combustion characteristics considerably

    ... hot-rodding the No.2

    Impressed, I carried out the same modification on a No.2 burner

    Getting rid of the infernal black spot

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    As BernieDawg rightly pointed out, such power and heavy fuel consumption was impractical - though the burner could be throttled down and I got to thinking about why a No.2 burner fitted to my self-pressurising No.6 stove performed much better than the No.2 stove examples I’d had.

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    Here was the burner, an unused example, fuel/air mixture way out.

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    A new burner, with a jet also previously unused. Wrong though to assume the jet was on specification.

    I set up this photo to show a jet (Optimus 111) on the left and the No.2 jet on the right.

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    It doesn’t look much, but with the area of the jet orifice a product of the square of the radius of the hole, the jet on the right will be passing at least a third more fuel than the one on the left.

    Optimus jet installed.

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    Simmer setting.

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    So, to those who complain of bad fuelling of a No.2 (modified) stove burner I’d suggest checking the size of the jet. It looks like quality control was poor and it can’t be assumed that an ‘unworn’ jet is on specification. Incidentally, the unused spare jet in its threaded housing in the windshield was also way oversized.

    The jet pricker clears the Optimus jet orifice by the way.

    John
     
  2. Simes

    Simes Subscriber

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  3. G1gop

    G1gop United Kingdom Subscriber

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    I haven't used my number 2 for a while but I have never had a rich flame. It has always looked like the ideal flame. Seems I have been lucky!
     
  4. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @Simes
    The ‘correct’ jet size is 0.32mm (24 gauge as a hypodermic needle bore equivalent). The oversized ones I have are probably around 0.4mm, maybe as much as 0.45mm.
     
  5. cottage hill bill

    cottage hill bill Subscriber

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    John, lovely post as always from you. However, in your pictures of the no.2 the grate is upside down. Your pictures have it in the stowed position, ready for closing the lid. If you flip the grate over you'll find the four little "points" in the grate are sized just right to hold the rectangular British army mess tin.
     
  6. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Well, in principle with the mess tin, yes but I was brewing in a Primus kettle that teeters on the points. The clearance between the base of the kettle and the burner is still sufficient, points down.
     
  7. idahostoveguy

    idahostoveguy R.I.P.

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    Brilliant post, John.


    Have a great day!

    Sam
     
  8. Simes

    Simes Subscriber

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    Yes 24, my mistake.
     
  9. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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  10. cottage hill bill

    cottage hill bill Subscriber

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    @presscall Well then John, you're obviously using the wrong kettle. Brew up in your mess tin like a proper squaddie. ;)
     
  11. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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