British no. 12 stove silent burner problem.

Discussion in 'Fettling Forum' started by Stuart Gibbins, Nov 30, 2020.

  1. Stuart Gibbins

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    Good evening all,

    I've purchased a 'Phil Beagle' silent cap for my no.12 stove and am having problems getting it to burn correctly. The problem seems to be that the vapour stream of kerosene is off centre to the cap suggesting my burner has had a knock at some point. Previously it has always ran well with the roarer plate fitted.

    You can see it here with the flame better on one side than the other. I tried a new jet but it was the same.

    [​IMG]

    With the roarer plate fitted you can see from the pattern on the bottom that it's not central.

    [​IMG]

    My question is - "how do I centralise the jet?". I thought about taking out the jet and pricker and screwing in a piece of brass bar threaded to match the jet. This would project above the. burner and should give me an idea of which direction to bend things. Does this sound feasible?

    Any suggestions appreciated.

    Thanks,

    Stuart
     
  2. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @Stuart Gibbins Welcome to CCS.

    The photo of your No.12 stove operating with a silent burner shows a flame pattern indicative of a very fuel rich mixture on one side of the burner. It is possible that this is caused by a jet alignment problem.....But there is another possibility.

    A similar problem sometimes occurs in Optimus No.111 silent burners and has been shown to be caused by a crack or penetration in the vaporisation chamber, feeding additional fuel to one side of the burner.

    A leak in the vaporiser chamber of one design of No.12 burners has alsoq been reported by CCS member.

    It would be a good idea to have close look at that side of the vaporisation chamber, before starting on the jet alignment:

    1996 British Army No.12

    Best Regards,
    Kerophile.
     
  3. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    ??? Sounds interesting. The only beagles I’ve known are very wayward chasing scents when let off the leash.

    Does running it with the flame plate produce a yellow flame?
     
  4. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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  5. Tony Press

    Tony Press Australia Subscriber

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    “Phil Beagle” is reminiscent of another stove cap designer...

    Cheers

    Tony
     
  6. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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  7. Stuart Gibbins

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    This is how the stove was burning in original condition, fuel is kerosene. There is a very slight orange tinge on the right hand side but it's been like that for the 15+ years I've owned it. I shall take a closer look at the vaporiser Wednesday evening.

    Stuart

    [​IMG]

    [​IMG]
     
  8. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @Stuart Gibbins . That looks like a good, blue flame pattern with the silent burner and I could live with that.

    It is a bit more powerful on the RHS of the roarer burner, which is interesting as the silent burner shows the LHS to be over-supplied with fuel...

    I am inclined to believe that there is nothing wrong with the vaporiser which I advised you to check.
    Is it possible that there is a minor problem with the jet aperture?

    Jet alignment would seem unlikely to be the fault, as the most powerful side of the flame pattern seems to be different between silent and roarer heads.

    Best Regards,
    Kerophile.
     
    Last edited: Dec 3, 2020
  9. Stuart Gibbins

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    Hi Kerophile,

    Yes, the flame looks ok with the roarer plate fitted. With the silent cap fitted the flame starts off ok'ish showing a rich mixture on one side. After a period of time the orange flame increases until it resembles a flame thrower almost like the cap cannot retain enough heat to vaporise the fuel:

    [​IMG]

    The vaporiser looks ok as well. The tabs that retain the roarer cap are bent down to allow the silent cap to sit flat.

    [​IMG]

    Stuart
     
  10. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    No ‘almost like’ about it I’d say, that’s a breakdown in vapourisation. Seems worse than pictured in the first post.
     
  11. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    May I suggest that you politely ask for your money back.
    Best Regards,
    Kerophile.
     
  12. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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  13. Stuart Gibbins

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    Strangely I read that post before I bought the silent cap but obviously didn't soak it all in. I have a spare Primus no. 5 outer cap and other bits and bobs so I'll have a play on my own stove. In the meantime I'm going to return the cap and give my old no. 12 a Christmas clean up for 2021.

    Stuart
     
  14. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @Stuart Gibbins . Good luck with your DIY endeavours. Be sure to give us a progress report.

    Best Regards,
    Kerophile.
     
  15. Stuart Gibbins

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    Hi Kerophile,

    1st update is the seller has refunded me for the silent cap. I'll be sure to report back on my stove story.

    Stuart