Optimus 300 J-tube replacement

Discussion in 'Fettling Forum' started by Kuman, Nov 16, 2020.

  1. Kuman

    Kuman Sweden Subscriber

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    Greetings from Sweden!

    This is my first post so: hello Everyone!

    I've just got (for free almost) Optimus 300 lamp, simillar to the one Nils has here: 1931 Optimus 300

    I tried disassembling it before lightning. Unfortunately J-tube broke while trying to unscrew holding nut and mantle holder.
    I've managed to free these parts (holder and nut) from tube rests but now the tube is shorter by a good 12mm.

    I'm considering turning a brass extension/adapter to fill this miss but I'd rather replace the J-tube instead.

    Do you happen to know if any other lamp uses same size tube? I recall someone mentioned that it's a copy of Petromax (?) lamp but which model?

    Tried finding replacement in Fogas but they don't seem to have it.

    In the worst case the lamp will serve as a donor for the other 300 but it would feel good to resurect her.


    IMG_1292.JPG IMG_1291.JPG IMG_1290.JPG IMG_1289.JPG
    IMG_1288.JPG
     
  2. podbros

    podbros United Kingdom Subscriber

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    Hello @Kuman .. Welcome to CPL!

    Thank you for showing your lantern, hopefully someone on here will be able to help you ?

    Good luck with everything :thumbup:
     
  3. Nils Stephenson

    Nils Stephenson Founder Member

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    Unfortunately I havn't found a replacement for these older J tubes. If you have the skills, then the best option is to try and extend the original one. This is something I have thought about before, but don't have the skills to do it. Just make sure you don't decrease the inner diameter.
     
  4. Graham P

    Graham P Australia Subscriber

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  5. Kuman

    Kuman Sweden Subscriber

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    Thank you gentlemen!

    I think I'll then try brazing my adapter, since it's only few mm which are missing.
    I'll post pictures once I'm done.
     
  6. MYN

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    Yes, you could try to fit on an adaptor piece. Threaded or brazed.
    Quite a lot skills and work would be required for jointing the tube without reducing the inner diameter.
    I'd definitely give it a shot.
    Brazing on a thin connecting sleeve, grinding off the excess, re-threading and some touch ups in the bore, etc. Finishing off so that it'll look as if it had never been broken. Easier said than done.
     
  7. BigStevie

    BigStevie United Kingdom Subscriber

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    @Kuman

    Hi and welcome to the forum. Good luck with fettling your lamp!
     
  8. Kuman

    Kuman Sweden Subscriber

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    It turned out to be quite an easy fix.
    I considered 2 options: brazing copper/brass extension pipe or making screwed-in adapter.
    I went for the adapter since the original J-tube is thin walled and quite weak. I was afraid that brazing could puncture it. Besides - adapter gave me an option to fine-tune the air gap since my Optimus 300 does not have any options to regulate that.

    I found copper pipe of adequate internal diameter. It turns out to be a standard dimension used in Sweden for most water/gas installations. I found mine in a pile of junk in my factory.

    Threading on the original J-tube was a bit of a mystery. Closest threads matching are M15x1 and UNF 5/8"

    FullSizeRender.jpg

    Since the lamp was made in Sweden long time ago (when?) they definitely used imperial threads so I went for UNF 5/8".

    IMG_1301.JPG

    The original thread is so thin - and J-tube so thin-walled - that it was collapsing while I attempted re-threading it.

    IMG_1302.JPG

    After straightening the J-tube back to circular shape I've turned temporary reinforcement to add stiffness to the pipe.

    IMG_1303.JPG

    Threading went well then.

    IMG_1304.JPG

    The adapter is made from brass, it's simply an oversized nut.

    IMG_1305.JPG

    After trimming length of both new components I could assemble the lamp.


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    The adapter is hidden inside the hood, not visible if you don't disassemble the lamp.

    FullSizeRender-2.jpg

    Internal diameters matching nicely.

    IMG_1309.JPG

    Tried first time without the globe nor mantle - looked good enough for me to try with the mantle.

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    And so she woke up!

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    Compared to my other Optimus lamps this one is very silent - and probably the oldest of them all.

    After 1h of operation still all was good so now it's time to clean her and give her "living-room look"
     
  9. Tony Press

    Tony Press Australia Subscriber

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    Good work, @Kuman. :thumbup:

    Cheers

    Tony
     
  10. Norman

    Norman United States Subscriber

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    @Kuman

    Great job. She is running very well indeed.
    Thank you for sharing your victory with us.

    Cheers,
    Norman
     
  11. rayw

    rayw United Kingdom Subscriber

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    Great innovation
     
  12. george United States

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    Welcome aboard!! You did a great job presenting your lantern and I hope you can find the parts you are looking for. Good luck!
    :D/:thumbup:
     
  13. JEFF JOHNSON

    JEFF JOHNSON United Kingdom Subscriber

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    Welcome aboard and well fettled!:thumbup::thumbup:
     
  14. MYN

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    A great job done with success.:thumbup:
     
  15. Kuman

    Kuman Sweden Subscriber

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    Post scriptum to this adventure:

    I've recently bought another, slightly younger, Optimus 300 in really bad shape (bought it only to get a globe).

    Out of curiosity I disassembled the vent to see if I can extract J-tube, as a replacement to my adapter solution.
    To my surprise the setup is almost identical to what I have "invented".

    I had to tear apart the vent as someone used steel screws which galvanically corroded and welded all parts together.
    Exploded (literally) view below:

    IMG_1351.jpg

    After some cleaning the J-tube assembly back in one piece:

    IMG_1353.JPG

    It seems that Optimus turned into this construction to save costs: instead of variable-diameter tubing they used standard, generic tubes and thin-threaded adapters to connect all together.

    I'll probably substitute my J-tube with this original assembly.

    As a side note - this "heavily fettled" Optimus 300 is now one of my favourite workshop lamps. Probably due to all work which went into fixing the lamp (there were all kinds of problems, including punctured tank close to pick-up valve) I like it very much and it will stay in my collection. It acquired character, I guess.
    Too bad these lamps are so susceptible to wind blows. Not really storm lanterns - for heavy weather I take Radius 119 or Primus 981. Optimus 300 is an indoors beast.

    Does anyone know what is the purpose of that thread on another side of this J-tube? This is the side where vaporised kerosene enters the tube. On all my Optimus 300s there is nothing screwed here. I wonder if adding a "cap" will act as a silencer, like on some Primus lanterns?
     
  16. Nils Stephenson

    Nils Stephenson Founder Member

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    This 2 piece J tube is seen on the early Optimus 300s. Why they did it is a mystery to me. It is a more expensive solution to make.

    The thread on the intake end of the tube is also a mystery. I have never found an explanation in any documentation, so all we have is guesses. I was wondering if it could be for attaching a restrictor for converting the lamp to alcohol. You would think that would be mentioned in a catalogue though, which it isn't.
     

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