I cannot unscrew preheater (or can I?)

Discussion in 'Fettling Forum' started by Lars Høyrup Jensen, Jul 7, 2019.

  1. Lars Høyrup Jensen Denmark

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    Hi,

    I recently bought my first pressure lamp. It is an old 300CP Primus lantern and it has a "KTAS" stamp on the lever for the preheater. I believe this means that many years ago it was bought by a big Danish telco (today TDC) for use by its enigneers when on field work. I don't know what model it is - would be nice to know:-)

    I have changed almost all gaskets. Only thing: I am not able to unscrew the preheater. The preheater is a different design than the standard Petromax preheater.

    There is a nut at the bottom of the preheater. I have tried to loosen it with quite some force (without giving it maximum torque). I am unsure whether this nut is soldered onto the fount or if it is just the deformed lead gasket that looks like soldering metal.

    My question: should I be able to unscrew the bolt? If yes, I will try again with more force.

    I have tried to attach photos of the lamp. If that fails, here is a link to the photos and also a short video of the lamp: https://photos.app.goo.gl/FwafqnUL5wpr46EV8

    I am new to this forum so please forgive any ignorance on my part.

    Best,
    Lars, Denmark

    IMG_20190518_165951.jpg IMG_20190629_194433.jpg IMG_20190629_194442.jpg IMG_20190629_194715.jpg IMG_20190629_194729.jpg IMG_20190629_194924.jpg
     
    Last edited by a moderator: Jul 7, 2019
  2. A Hendrikx Netherlands

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    Lars,
    i think it i soldert in and het hex profile is only to holt on wen you mount or los the preheater.
    live it if it is air thight
     
  3. Nils Stephenson

    Nils Stephenson Founder Member

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    Hi Lars and welcome to the forum. This lamp should be a Primus 1084. The model number was most likely on a label on the collar. This is one of the models KTAS used at the time. Under the tank there should be a small stamp of a circle with letters and maybe numbers as well. The letters are the date code and I would guess that they would be either AU or AV, for 1955 or 1956.

    The preheater would normally screw out but it looks like someone has soldered it in. Normally it is mounted with a loose lead washer under the fitting. If the alcohol dish was fitted to the lamp then I would recommend using that for starting rather than the quick starter.

    If you like you can always get in touch via PM. Maybe I know of a collector near you that might be able to help.
     
  4. MYN

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    Looks like its already soldered at the threads. If its not blocked and able to pass both fuel and air properly, I'd leave it as it is.
    Unless you are skilfull at using a blow torch, I wouldn't recommend re-melting the solder as that would risk unintended melting of other soldered joints nearby.
     
  5. AussiePete

    AussiePete Australia Subscriber

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    Agree with MYN. If it works, don’t touch it. You may do damage. If it ain’t broke, don’t fix it.
    Cheers
    Pete
     
  6. MYN

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    I'd leave that alone. You don't want to be greeted with a horror that awaits the unwary fettler under that solder-joint.
    For your infomation, I, myself had soldered a preheater to the fount before. Not a Primus, but a Butterfly.
    However, that was only because I had actually twisted off the threaded section by over-torqing it.:mrgreen:
     
  7. Lars Høyrup Jensen Denmark

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    Hi everyone,

    Thanks for the very useful replies. It is now obvious to me that 1) the preheater is soldered to the tank and 2) I shouldn't mess with that solder joint (I am definitely a rookie with a blow torch). Fortunately the preheater actually works and has a proper seal, so there really is no need to unscrew it. I just like to take things apart:-)

    Regarding lamp model and date, I haven't been able to find any stamps - not even under the tank. There are two lables on the collar but whatever was printed on them is now gone. See photos.

    Thank you for your kind offer, Nils, I will send you a PM.

    IMG_20190708_191136.jpg IMG_20190708_191047.jpg IMG_20190708_191101.jpg
     
    Last edited by a moderator: Jul 10, 2019
  8. Nils Stephenson

    Nils Stephenson Founder Member

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    With these extra pictures I can tell you that this is a Primus model 1094. It is identical to the Optimus 1550 except for the tank stamping, control wheel and quick start lever. It would have been made some time between 1957 and 1962. From 1957 on Primus stopped stamping the base of the tank, so it is correct that there is no mark there. The larger label that is riveted on would have had the model number. The smaller label is one added by KTAS which just said "For petroleum".
     
  9. Lars Høyrup Jensen Denmark

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    Excellent. Thank you for the very detailed information. And nice to know what model I own:content:
     

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