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Thread: Tube in a tube in a U2

  1. #1
    Flashaholic alantch's Avatar
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    Default Tube in a tube in a U2

    I recently acquired a pre-owned early-serial Surefire U2 that could accept 18650 cells. To increase my options for cell-usage, I decided to put regular 123s in it, but there was battery rattle as the diameter of the tube was much larger. So far, I've only read about people asking for the inserts to be removed, but never the other way around - correct me if I'm wrong. So on to the hunt for an insert that would fit nicely into the tube. Various items were looked at - the kids toys, candy containers, glue sticks etc etc. Of all things, I found an aluminum tubing that fit the batteries perfectly AND could go into the tube with minimum effort. An alu tube within another alu tube - perfect!

    A 60mm section of the tube is cut, then both edges filed flat and smooth. I had to sandpaper the inside of the U2 a little as the boring was not very smooth and the tube wouldn't go in easily. A little more sanding on the outside of the alu tube and it now fits into the U2. I can remove it by inserting a finger into the tube and twist it out.

    Hopes this will be useful for those who've either lost their inserts or who'd like to have the option to run 123 cells in earlier U2s.


    The 2 tubes


    Not sure if you can see clearly in this pic, but there's a lip at the end of the U2 tube that'll allow only 123 sized cells to enter. 17670 and 18650 cells will have to be loaded from the front.


    Tube part-way in


    Tube now fully inserted


    Tube fully inserted - front view

  2. #2
    Flashaholic* Fallingwater's Avatar
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    Default Re: Tube in a tube in a U2

    Is the flashlight dimmer with a 18650? If it isn't, I really can't see why you'd want to use primaries in it.
    Eat, drink and be merry, for tomorrow you may die.

  3. #3
    Flashaholic alantch's Avatar
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    Default Re: Tube in a tube in a U2

    One reason to switch to primaries is when you're travelling or on the move and there's no way to recharge your batteries. The other is well, just the pure the enjoyment of the process

  4. #4
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    Default Re: Tube in a tube in a U2

    Cool but I'd leave the tube out and use 18650's. Maybe carry your spare "emergency" primaries stored in the tube and use it as needed?

  5. #5

    Default Re: Tube in a tube in a U2

    there is a very small difference in brightness using the 18650.
    but i haven't used CR123s in my U2 since the ones that came wiht it ran out.
    i just carry extra 18650 if i am travelling anywhere
    two of the 2400mah cells give me like 4hrs on high

  6. #6
    Flashaholic yekim's Avatar
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    Default Re: Tube in a tube in a U2

    Nice work, looks good. I find it disconcerting people are bashing you for your choice in batteries. Soon I guess they'll lynch those of us who still prefer to burn up alkies.
    Has me and you wants to accompany, in darkness.
    Buying Broken Flashlights and flashlight parts.

  7. #7
    Flashaholic* Fallingwater's Avatar
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    Default Re: Tube in a tube in a U2

    Where do you see bashing?

    "OMG you're using primaries hahaha you suck idiot" = bashing
    "I can't see why you'd want to use primaries" = polite opinion
    Eat, drink and be merry, for tomorrow you may die.

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