Ditmar 581 Flames with or without a hood

Discussion in 'Fettling Forum' started by Camp numao, Jan 16, 2025.

  1. Camp numao

    Camp numao Japan Subscriber

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    I am burning a ditmar581 with kerosene.

    It glows before I put the hood on, but when I put the hood on it bursts into flames.

    Changing the nipples did not improve the situation.

    The j-tube is not glowing red.

    It feels like it is bursting into flames due to reduced air intake, but why?

    If anyone has had the same experience please let me know the solution.

    Thanks.
     

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  2. Camp numao

    Camp numao Japan Subscriber

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    I think this can be solved if I can adjust the height of the J tube.

    Thank you.
     
  3. Piotrek

    Piotrek Poland Subscriber

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    or install even smaller jet. Somehow... Maybe these jets that you have are a bit bigger then 100cp.
    Maybe try with petrol. Carefully ;)
    good luck,
    Piotrek
     
  4. podbros

    podbros United Kingdom Subscriber

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    Hi @Camp numao
    When I zoomed in to the first photo it looked like the jet was angled and not pointing straight up?

    regards
    pb

    IMG_3100.jpeg
     
  5. JonD

    JonD Subscriber

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    That's a good point. My own thoughts concerned that "rim" above which should seal the air intake gallery from the exhaust one.

    If the hood does not seal well there it has to eat it's own combustion products and it won't like it. Not a best feature of the Pmax system.
     
  6. Martin K.

    Martin K. Subscriber

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    The jet definitely doesn't seem to be pointing straight up. That could be a problem. You could also try carefully smoothing the edge of the mixing tube using a countersink.

    Maybe also the seat of the jet is damaged. I have one 581 here at which I had to tighten the jet several times when hot until there was no more leak between jet and vaporizer. Even now, it still comes loose from time to time, so I have to check it occasionally and retighten it if necessary.

    BTW: You can reduce the jet orifice using a pliers wrench by pressing the six flanks of the nozzle firmly together all round. I have done this successfully several times. The result can be checked with a small square broaches.
     
    Last edited: Jan 16, 2025
  7. MYN

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    @Camp numao
    How long does it take to burst into flames outside the mantle when you put the hood back on?

    1. If it is near-instantly, then it can be an issue of air intake or too much combustion products getting mixed with the air.
    The jet certainly looks skewed. That can lead to poor fuel-air mixing in the J-tube. The same would also apply if the jet orifice is slightly enlarged.

    2. If it takes a while before bursting into flames, then it can be an issue with J-tube overheating. This can be checked if you temporarily wrap it with some ceramic or asbestos insulation.
     
  8. Camp numao

    Camp numao Japan Subscriber

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    @Piotrek

    Thank you.

    The hole in the nipple is big enough for a 0.12mm needle to pass through, so there seems to be no problem.

    IMG_20250117_224958.jpg

    The same was true for the 100cp nipple purchased from a third party.

    This lantern does not have a shutoff valve, so I will refrain from using gasoline.

    Thanks for your advice.
     
    Last edited: Jan 17, 2025
  9. Camp numao

    Camp numao Japan Subscriber

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    @podbros
    @Martin K.

    I followed your advice and straightened the vaporizer, and it stopped flaming.

    IMG_20250117_224342.jpg



    Thank you.

    But it's still not burning completely. (You can see the mesh of the mantle.)

    IMG_20250117_231926.jpg
     
  10. Camp numao

    Camp numao Japan Subscriber

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    @JonD

    Thanks.

    Are you saying that if the top hood doesn't seal tightly against the inner chimney when it's attached, the heated air will get sucked back into the j-tube?
     
  11. Camp numao

    Camp numao Japan Subscriber

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    @MYN

    When the hood is removed, it glows so brightly that the mesh of the mantle is not visible, but as soon as the hood is put on, it goes dark.

    Therefore, I do not think that combustion is occurring inside the J-tube, but rather that there is a problem with air intake.


    So I tried installing a 523 inner chimney which has a taller j-tube.
    The left is for the 581, and the right is for the 523.

    IMG_20250117_224157.jpg   IMG_20250117_225353.jpg

    As a result, it continued to shine even with the top hood attached.

    IMG_20250117_232037.jpg


    Based on this result, I put it back into the 581 inner and tried lifting the j tube with a washer.

    IMG_20250117_224238.jpg

    However, even when I lifted the j tube, the air intake distance did not change because the hex nut for fixing the j tube for the 581 is located at the intake port.

    And it only lit up enough to see the mesh of the mantle.


    It looks like the only way to raise the height of the j-tube without a nut is to silver braze the inner chimney and j-tube.

    But I don't want to modify it while still wondering why I have to do that to get complete combustion.

    There must be some other problem that won't solve the problem, so I'll think about it a bit more.

    I'd appreciate any more advice.
    Thank you.
     
  12. Martin K.

    Martin K. Subscriber

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    From the fit of the inner chimney and the protrusion of the jet everything looks right, so I don't think it's sucking in combustion gases or the distance between jet and mixing tube is wrong. My bet is that the vaporizer is not sealing properly against the jet, or the jet is still too big for that lantern even though you tried a new one. Have you checked that there is no blockage in the mixing tube or burner? Sometimes insects use it as a shelter if the lantern has been in a shed for a long time.
     
  13. MYN

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    Then I would suppose this to be so.
    There shouldn't be a need to alter the basic design as all the original parts are present, supposedly not damaged or missing in any way.
    Now that you have corrected the skewed direction on vaporizer/jet, then it should be glowing somewhat better than before(when you first lighted it). ...With significantly less flaming outside the mantle (when the outer hood is attached).
    I cannot see that clearly from the picture but you can check again the 581 inner hood and J-tube's respective alignment with the direction of the jet:
    137335-2389fe6d34899cbe9493d7f9e44248e2.jpg
    Check that the J-tube current position is as aligned as possible in the direction of the corrected jet/vaporizer direction. A slight tilt towards the right or left can sometimes make a huge difference in the resultant glow.
    Also check that the 581 inner hood is not unintentionally tilted when you put on the outer hood. The rim should be uniformly in contact with the outer hood's inner wall to seal off the combustion products from the air intake point(air gap).
    IMG_20250116_194958.jpg

    Depending on the current corrected jet's direction, check that the J-tube's assembly is not tilted beyond its ideal alignment in the above direction too especially when the hex nut is tightened. It looks slightly off-path in the above picture. (Not sure how it looks now that you have corrected the jet/vaporizer's direction). Sometimes, a slight correction in the above can make a marked difference as well.
     
  14. Camp numao

    Camp numao Japan Subscriber

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    @Martin K. @MYN

    Thank you so much for all your advice.

    After reading everyone's advice, I replaced the nipple with a different one.

    The hole in the previous nipple was small at first, but it seems that it had become slightly larger because I had poked it several times with a 0.12mm needle.

    I also purchased a nut of the same size as the original nut and thinned it to about 2/3 its thickness to make it easier to take in air.

    These two steps, combined with straightening the vaporizer, allowed me to improve the situation.

    I'm very happy that I was able to improve it, thanks to everyone's advice.

    Thank you!


    IMG_20250118_163132.jpg DSCF1666.JPG
     
  15. MYN

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    Great results. It looks awesome.:thumbup:
     
  16. Sellig33

    Sellig33 France Subscriber

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    Nice result :D/

    Gilles
     
  17. Piotrek

    Piotrek Poland Subscriber

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    Congrtulations!

    You can also file top of the generator by 0,5mm and that would also increase the air gap, but it was mainly up to unappriopiate jet size.

    If 0.12mm needle fits the jet then the jet is approx. 0.14mm.

    According to @WimVe site 0,14mm jet is for 150cp lamps.

    PETROMAX NUMBERS

    According to this thread

    Optimus 300 help needed

    100cp jet should be "100cp, 0.12mm, 0.0047" so needle would be approx. 0.10mm

    Bigger jets can be all right for petrol 100cp lamps, but it is to big for kero.
    Please see the table jet/power/fuel type in attached file which was published by @Nils Stephenson in the past.

    In my opinion new needle/jet 0,12mm/0,14mm sets manufactured currently in Korea and available on ebay are not correct for 100cp kero lamps.

    By the way, I have a different jets in my small 100cp petrol Ditmars from 1941, 1942. My jets look like Coleman jets, not a Petromax/Optimus/Hasag. I do not know why.

    Piotrek
    Optimus jet.jpg
     
  18. Camp numao

    Camp numao Japan Subscriber

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    @MYN @Sellig33

    Thank you!
    I usually have problems when I repair a lantern, but the feeling of satisfaction when I solve it drives me crazy.
    (I only need one lantern, but I keep buying more and more.)


    @Piotrek

    Thank you!

    It seems that the needle I purchased on eBay is indeed 0.1mm.

    I saw on another site that 100cp=0.12mm needle, so it seems I used incorrect information and performed the wrong procedure.
    I will make sure to remember the information you taught me from now on.

    I learned a lot, thank you.
     
  19. Piotrek

    Piotrek Poland Subscriber

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    @Camp numao
    I think it is confusing regarding size of 100cp jet/needle for 100cp/100HK lamps for petrol, kerosene and spiritus.
    Different fuels have different jets just like in modern multifuel stoves. If anybody can post such a documents that would be great. That Optimus jet technical drawing from my previous post is super helpfull and reliable, but does not cover 100-150CP size and lacks info regarding spiritus fuel.

    It is good to know that there are 0.1mm needles available. I was looking for such recently and could not find any. So I just took a new 150CP Petromax needle, inserted it in the Dremel type micro drill and reduced needle dimameter with very fine sand paper. Easy even for me. OK, maybe it is not perfect because mainly the tip part is narrower, but only that tip protrudes from the jet. It works just fine and cost me much less then needles from ebay from S. Korea.
    all the best,
    Piotrek
     
  20. MYN

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    @Camp numao
    The interesting thing is,...the lantern appeared to glow pretty well even without changing the jet(nipple), or straighening the vaporizer or any dimensional changes on the J-tube nut when it was operating without its outer hood. :):-k
    I can't exactly tell from the pictures but was that glowing just as well as it is after the nipple and nut replacement?
     
  21. Camp numao

    Camp numao Japan Subscriber

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    @Piotrek

    The needle that comes with the nipple sold by the Korean seller seems to be 0.1mm. I'm using that one now.

    Your idea of filing down the 0.12mm needle to 0.1mm is a nice idea. I'll try it next time I have a chance.

    Please let me know if there's a good way to make the nipple hole 0.12mm.

    I tried Mr.MartinK's method, but with my processing skills I couldn't crush it properly. The method is great, but it's just a matter of my skill.

    Do you know how to make the nipple hole smaller?
     
  22. Camp numao

    Camp numao Japan Subscriber

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    @MYN

    Yes, at first both nipples glowed when I removed the top hood.

    After that, I think the hole in one of the nipples widened because I repeatedly used a 0.12 mm needle to manually remove the soot.

    At the same time, I made several improvements, and I think the problem was finally solved when I finally replaced the nipple with the remaining one.

    As for your question about the glow when the top hood is not attached, I don't understand the logic behind it, but it may have something to do with the fact that air can be taken in from the front of the nipple without the hood.
     
  23. MYN

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    Great efforts. Anyhow, I would suppose the main problem was that the nipple orifice was unintentionally enlarged...a little?
    Not so little actually.
    0.1mm is indeed one of the smallest (if not the smallest) of all for pressure lamps. An increase to 0.12mm diametre would mean an increase in its cross sectional area by about 44%. I'd say that is pretty significant :).
     
  24. Camp numao

    Camp numao Japan Subscriber

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    @MYN

    I see, there is certainly a square effect when considering area.
    I learned something new.

    Thank you for reading.
     
  25. Piotrek

    Piotrek Poland Subscriber

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    @Camp numao
    You can try method below, but with even smaller hypodermic needle. This is "level hard" difficulty in my opinion, but I believe you can do any small and precise things :content:
    Petromax 900 “ Little Baby” Hypodermic Needle fix for the Jet | Classic Pressure Lamps & Heaters
    Other method might be tapping the jet from the top to reduce the orifice size - reportedly, sometimes it works.
    Maybe silver soldering the orifice and drilling new, smaller one would work as well - I do not know, just an idea.
    Contact seller from ebay and request different jet size? That should be no problem for him/her.
    Recently I bought two old 100cp jets from a private person. These have no visible orifices at all, so I will just drill 0,1mm hole. I can always make it bigger, but in general I prefer smaller jets then original.
    Please let us know which method works, which does not, so it will be easier for some lazy Polish collectors in the future :lol:
    all the best,
    Piotrek
     
  26. Camp numao

    Camp numao Japan Subscriber

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    @Piotrek

    Thank you for letting me know.

    I've tried transplanting a syringe when repairing a stove, but I've never tried a 0.26mm syringe. It looks like a difficult task.

    I've also heard about the method of making the hole smaller by hitting it, but it requires courage to try it.
    I'll probably end up deforming the nipple as a whole. [-(

    The method of drilling a hole seems difficult for me too.
    I bought a 0.1mm drill the other day and tried using it, but it broke after just a little pressure.
    I want to be more dexterous.

    If I need a 0.12mm nipple in the future, I'll try the method of making the hole smaller by hitting it.
    Thank you for letting me know all about it.:thumbup:
     
  27. Martin K.

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    That's not a matter of skills, but only of force. You could also try to use a vice. But press carefully and check the results with a tapered needle after each pressing step, until the correct Ditmar needle fits in snugly.
     
  28. Camp numao

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    @Martin K.

    I didn't want to deform it in any weird way, so I just clamped it in a small vice, so maybe that didn't work.

    I'll try using a larger vice. Thank you.
     

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