Primus 71 (1930's?) How to disassemble

Discussion in 'Fettling Forum' started by Karolina, Jan 28, 2021.

  1. Karolina Sweden

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    Hello,

    this is my first post, so I hope I am posting it correctly. I recently aqquired this very nice Primus 71 that I believe is from the 1930's (no date code). I would like to unscrew the pipe in order to have a look at the wick. However it is very stuck, and I can see that someone before me has tried to unscrew it, as the pipe is a bit "crushed". How should I proceed? I attach some pictures of it from the ad.


    Thank you in advance.
    primus711.jpg primus712.jpg primus713.jpg
     
  2. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Welcome @Karolina
    Used on an Optimus 8 tank here, but same technique works on Primus 71, Optimus 80, Svea 123.

    5063D35C-9C2A-438B-B651-1E2C057320AD.jpeg

    B496939F-B4B6-4609-BF44-827DF4F44C91.jpeg

    Either cut grooves in the blocks to fit the Primus burner or use a soft enough wood to be indented by the burner when you clamp it. I used nitrile sheet for extra grip/cushioning.

    John
     
  3. Karolina Sweden

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    Marvelous :) I will try that.
     
  4. Karolina Sweden

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    Oh, and another question! Where can I find a handle that fits the pan, and pot? :)
     
  5. Optimust

    Optimust United Kingdom Subscriber

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    @Karolina

    Fogas in Sweden will stock the handle for the pot / pan. The model 71 stove you have is a good example of it'-s type, enjoy your find. My Best Regards too you.
    Optimust. :content:
     
  6. Karolina Sweden

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    I just ordered a wick from them, should have been more patient haha. Indeed I will, it will go lovely with my other 1930's camping equipment.
     
  7. Dutchmike

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    Hello, if there are no reasons to check the wick, I would leave it. A weak functioning of the burner is most often caused by a not 100% efficient seal in the fuel cap. If that checks out, then the method suggested by Presscall is excellent.

    You do have a beautiful set there, and the first version with a detachable pot support and small fuel tank, making it the most compact set Primus offered.
    So first half of the thirthies, I reckon.
    The later model had the pot supports attached to a higher structure (see Gallery) which allowed a slightly bigger fuel tank as well.

    Welcome to this site Karolina! Mike
     
  8. Karolina Sweden

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    Thank you, I tried it, and it does run, but it doesn't become "glowing hot". The cork seal in the cap seems fine, but I can use some cork grease that I have for my antique flutes, or just maybe replace with some cork if need be.

    Wonderful! Is there any more ways to date it? Also I don't seem to be able to locate a handle (the one that looks like small shoehorn haha).
     
    Last edited by a moderator: Jan 28, 2021
  9. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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  10. OMC

    OMC Subscriber

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    Welcome @Karolina .
    You have a very nice fairly rare kit there, year range should be 1931 -c1933/34, it matches the 1st version of No.71. source

    With good suggestion above you are onto... "Marvelous :) I will try that."... hang on.
    There's also a suggestion to "...leave it", that might at least give you pause.

    John's block method seems to be the best to-date and he has explained you want to improve fit and grip on your vaporizer... that said, IF you were to proceed with wood clamp method....
    please note re this vaporizer to tank threaded connection.
    "Yours like many is 50+ yrs old, plenty are 100+, the repairs are a challenge and the brass can be soooo unforgiving ... that type vaporizer included (seized, prev. owner: bent, stripped, soldered etc) can give a guy fits."
    The fragile thin wall vaporizers of pre-37 P70 & 71s are especially prone to damage during repair attempts.
    ie sheered P70rizer.jpg or 2. twisted P71rizer.jpg
    "2" gave the wood block approach a shot. IF it fails it is at the thin wall portion source
    In link the vaporizer eventually sheered, that repair had to proceed (no turning back), John added "... the Primus and can stand a fair amount of heat from a blowtorch. Purge the tank of fuel with soapy water and expect the wick to burn.
    Direct the heat at the base of the burner stem and on cooling it’s likely to have broken the bond between the burner and tank threads.
    "
    Anything else John wants to add.. @presscall ?

    This by no means says best method/wood block after penetrant soak is a problem. It is cautionary note that to proceed is not w/o significant risk and...
    IF proceeding, then do so with very close eye and utmost care.
    FWIW I have soaked some for week+, tried to undo w/o over torque and no luck. They are set aside...
    going with the "...leave it" approach for the foreseeable future.
     
    Last edited: Jan 28, 2021
  11. Karolina Sweden

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    I will try to use a few times before proceeding to do any sort of repair. Thank you for all of the information above. Very useful! I have a torch that reach some 1900 degrees Celsius which I have used to loosen rusted bicycle parts (1920's bicycle). I would probably leave it with some penetrating oil for a month or so before trying anything.
     
  12. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Fair comment @Dutchmike and @OMC in the light of ...
    Indeed, @Karolina there’s a risk of the existing damage making the procedure risky, though the clamping block method supports all parts of the stem evenly and concentrates the torque on where it’s needed - to break the tapered threads joint bond.

    The prudent thing to do would be to establish with a test firing how the stove performs. Yes to confirming the tank cap is sound, the jet thoroughly pricked and the burner bell properly hand-tight to maximise heat transfer and vapourisation of the fuel.
     
  13. Karolina Sweden

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    Yes I will test fire it, and take some photos to help with evaluation. Thank you for all the help so far :) I can sit for hours just looking at it, it's so beautiful.
     
  14. Karolina Sweden

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  15. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @Karolina
    Output is subdued but that might be because you started filming not long after priming and start-up. Self-pressurising stoves take a while to get up to speed - a couple of minutes maybe.

    A dense-grade cork was often used originally but these days it’s as well to use a viton cap seal and leave no doubt that the sealing is optimum.
     
  16. Karolina Sweden

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    My cork is probably not especially dense, any idea where I might find some? :)
     
  17. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Use viton sheet, 1.5mm thick or so. Site sponsor Fettlebox is a good source for readymade seals.
     
  18. Karolina Sweden

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    All right :) Ordered one.
     
  19. magikbus

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    The test to see how my stoves are running is to take exactly 1 liter of room temperature water, run the stove for 5 minutes and then put the pot of water on the stove. Take the amount of time it takes to bring 1 litre of water to a rolling boil. Then do the fettle and re-test to see if there was any improvement.
    It works for me.
    Stan
     
  20. Karolina Sweden

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    Thanks I received the seals yesterday, and will do a test later today to see if there's any difference. One more question: Does anyone here know where I might purchase a buckle identical to the one supplied with my primus. The one that I have is rusted to pieces, and it would be nice if it was functional, and as original as possible. The ones I have found either were too big, or not the correct design.

    Thank you :)