Self-lighting JUWEL 15 (circa 1930) with asymmetric burner

Discussion in 'Juwel No:15' started by Radler, Feb 27, 2019.

  1. Radler Switzerland

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    This stove has a non-symmetrical burner similar to some very early JUWEL petroleum cookers over 100 years ago. The unrestaured stove:
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    The rising tube of the burner is screwed into the tank with a tapered thread. No hexagon, but two wings are used to tighten. Damaging the thread by over-turning with a spanner can be avoided. The spirit-cup lies loosely on the fount. In the rising tube of the burner is a rolled steel wire mesh along the whole length. This prevents pulsation of the flame by the Leydenfrost effect.
    The inner cap of the burner and the mixing tube together form one component. The outer cap has the shape of a hat with brim. With 32mm diameter it is much smaller than the Primus burner caps (~ 44mm). The jet diameter is about 0.25mm, which allows a good down regulation of the flame.

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    The fount is made entirely of brass and holds 1 litre.
    The pump has a diameter of 26mm and a stroke of 74mm. The stroke volume is 39 ml.
    This is twice the volume of most Primus stoves (20 ml)!
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    The stove was obviously made for the worldwide market, as the texts in the non-Latin writings show.
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    The bottom line: JALNIZ "JUWEL" ISMI VE FABRIKANIN MARKASI OLURSA KABUL EDINIZ is Turkish, written in Latin capital letters. Turkish was written exclusively with the Arabic alphabet until 1928. The Turkish reformer Attatürk decreed on November 4, 1928 the mandatory use of the Latin alphabet. So the stove was made after 1928.

    The Turkish alphabet has some special characters, e.g. an "i" and an "ı" (without superscript dot) are two different characters. Therefore, the i-dot should be superscript on all capital "İ" except in "JALNIZ" (today written "YALNIZ"). I interpret the use of capital letters and the incorrect spelling as sign of the uncertainty when the new Turkish alphabet was established.

    The stove can be dated so far: not made before 1929 and not after 1939, because in Germany, with the war economy, brass had to be replaced by steel. After 1945, this model seems to have been no longer produced.

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    All parts except the gasket in the filler lid are original. The trivet had a silver colour originally (tinned?) and is not restored yet.

    The stove is pleasant to use. Even if only 250ml of fuel are in the tank, pressure is achieved with a very few pump-strokes.
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    How does self-lighting work?
    During priming the air release must be closed, if self-lighting is intended. From the spirit-cup and the rising tube heath is conducted to the upper part of the tank. The air in the tank gets warmer and expands. This forces fuel up the rising tube, where it vaporizes.

    Soon a few blue flamelets play around over the holes of the burner. When the priming flame dies, these flamelets become steady. The burner is lighted. To have more power some pumps are necessary now.
    Why no underburn occurs? I am studying the auto-lighter at the moment and made the following observations:
    As long as the priming flame is alight, the jet stream is relative slow and takes the flue gas of the priming flame into the mixing tube. There is not enough oxygen in the mixing tube and the burner for underburning. Only after having left the burner holes, some fresh air is available.

    What is the advantage of a self-lighting stove? It is not necessary to wait for the right moment to light and you can't miss it.
    The disadvantage is the smell. Not all vaporized kerosene is burnt during the priming process. This makes bad odours which are really unpleasant. If the stove is left alone unlit, it will spill vaporised and liquid fuel out of the jet for a while.
    Maybe the stove should have a lighter tube, to make lighting a bit more reliable. But this is an other story.

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    Radler
     
  2. Tony Press

    Tony Press Australia Subscriber

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    Thank you, Radler.

    That is a very clear portrait of an interesting stove.

    Cheers

    Tony
     
  3. gieorgijewski

    gieorgijewski Subscriber

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    chapeau bas - for quality of description
    ---------------
    But Now important question - tank to burner mounting point system - its mystery for me - and necessary to rebuild transport fuel cap.
    My few collapsible stoves need reserve cap - but german area system around 1920, is unknown.
    Juwel, Perfectus, Phoebus - diameter seems to be non metric and oscilated less then 1/2 inch
    -----
    If You could look at this problem...
     
  4. gieorgijewski

    gieorgijewski Subscriber

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  5. Lennart F Sweden

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    The usual German pipe threads of that time was the British Whitworth pipe threads but with German name and decimal size (today like the Japanese renamed to metric numbers but still inch dimensions) - check 1/4"BSPT(size 0.25 in old German system) that has a nominal max diameter slightly over 1/2" but most specimens should be under that because pitches are always rounded or flattened to prevent seizure.
     
  6. gieorgijewski

    gieorgijewski Subscriber

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    ok.
    thanks
    ill try to check that
     
  7. Nicola Francesco Elia

    Nicola Francesco Elia Subscriber

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    Hi, very nice, I have the same stove, but it's not marked Juwel 15 but Juwel Novum, not sure if the Novum came before or after the 15L.

    It's posted here.

    Unfortunately I am missing the burner caps that are very unique, you're very lucky to have them. Primus no 4 caps should be the right ones, I've found an outer cap, but I am still looking for the inner cap that I will modify to add the central spigot.

    Eventully could you provide some mesaurements of the caps?

    Many thanks,

    Nicola
     
  8. janders

    janders Subscriber

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    Great writeup and photos!!!
     
  9. Radler Switzerland

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  10. ROBBO55

    ROBBO55 Subscriber

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    Excellent post Radler and an interesting stove. :clap:
     
  11. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi, for comparison here are some dimensions for Primus silent burner caps:

     
  12. Nicola Francesco Elia

    Nicola Francesco Elia Subscriber

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    @Radler

    Thank you very much for taking the time to share with us all the sizes of the caps, I really appreciate your help.

    Nicola
     
  13. Ed Winskill

    Ed Winskill United States Subscriber

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    I remember in early days here I had a fascination with the Juwel/Gustav Barthel variants on the Swedish classics. Curvy founts, strange burners, etc. Then somehow they came to seem aberrant to me, unlike the simple Swedish concept. Just a random observation....