Prim Compact gasoline stove

Discussion in 'Russia' started by presscall, Feb 15, 2020.

  1. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Inspired by @gieorgijewski featuring his Prim Compact in the Stove Reference gallery I dug mine out of deep storage to have another play with it, having relegated it there in frustration with it’s quirks. Crucially, for someone who likes to cook with a stove and not just boil water, it’s a stove that’s either on ‘max’ or ‘off’ with no simmer setting.

    Having had another delve into it it still won’t simmer, but although I concede that I’ve robbed it of its distinctive ‘of the era’ yellow and blue paint scheme I couldn’t resist giving it a more subdued paint finish. I acquired the stove cheaply, the pot rest missing, so I made one out of 5mm rod with silbrazed joints. Though I’ve used stove paint, it will soon burn off the trivet - I’ll report back with post-firing photos subsequently.

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    Here’s how it looked before.

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    First I looked into “why no simmer?”

    At best, this is possible for a short time until it flips into underburn or, if throttled down too much, extinguishes.

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    The burner disassembled. The regulator spindle is the one inline with the fuel inlet pipe. The spindle mounted vertically in the burner is a jet pricker device, accessible to operate with the regulator control knob and shaft through a hole in the stove box when the burner/fuel tank assembly is installed in use. Not practical at all.

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    I think this contributes significantly to the lack of a simmer setting, a straight-through, unrestricted passage of fuel through the valve. Usually, a regulator spindle is at right-angles (or nearly so, thinking Svea 123) to the passage of fuel, with the venturi/baffle effect of fine passages contributing to the control of fuel.

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    So, I tried inserting a length of wire, close-fitting in the fuel pipe bore.

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    Disappointing. No real improvement.

    I tried not pressurising the fuel tank very much. No improvement, and too low, the burner underburned again.

    Surprisingly, given the short stroke, O-ring pump washer and narrow bore of the pump tube, the pump is quite efficient.

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    Pump and non-return valve.

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    The NRV-to-pump tube end cap seal was rubber, which I replaced with a lead seal before re-installing it.

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    While I remember, for anyone dismantling one of these, removing the pricker spindle - with the jet removed - is done by screwing it clockwise into the burner riser until it emerges out of the top.

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    This photo shows how the jet pricker unscrews from the tip of the spindle. No wrench flats, the pricker has to be gripped in plier jaws.

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    The spares kit. I’ve introduced an Optimus 111 jet in there ...

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    ... part of my ‘simmer’ trials. The 111 threads match and the Prim pricker passes through the jet. Same jet orifice size, predictably no difference to the fuelling behaviour.

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    Burner caps.

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    Those three notches in the lower circumference of each cap engage with corresponding projections formed in the burner bell. The outer cap can then be twisted anti-clockwise on its ‘ramped’ lower edge flare to secure both caps firmly in place.

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    A refinement worth doing is to smooth off the sharp corners of the tank stowage clip in the stove box.

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    Finally, firing. Ok, no simmer, but the output as a water boiler is impressive.

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    I’ll post photos shortly of what that fiery blast inflicted on the trivet paint.

    John
     
  2. The Warrior

    The Warrior United States Subscriber

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    The new paint job is a huge improvement, imo. Cool looking stove, hope you get it figured out.
     
  3. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @The Warrior
    Thanks! I’ve run out of ideas for getting it to simmer for now.

    Still, the paint job on the trivet has mostly held up and I won’t be relegating the stove to ‘deep storage’ any time soon.

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    Thanks again to @gieorgijewski for giving me the incentive to look afresh at the Prim Compact.
     
  4. The Warrior

    The Warrior United States Subscriber

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    Sorry I'm no help, haha. New to all of this, I just don't understand the mechanicals yet.

    The green paint gives it that military look, which I'm a fan of.

    Also, I'm surprised the factory that made them didn't round the corners of the clip like you did.
     
  5. SveaSizzler

    SveaSizzler United States Subscriber

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    Stamp a Crow's Foot on it, and tell the gullible it's a Military No. 9-3/4.
     
  6. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    I’ve been more inclined just to stamp on it for most of the time I’ve owned it.
     
  7. SveaSizzler

    SveaSizzler United States Subscriber

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    I meant the Broad Arrow.
     
  8. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @SveaSizzler
    Yeah, I know, my sense of humour.

    You meant one of these.

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    Should be the USSR equivalent really.
     
  9. SveaSizzler

    SveaSizzler United States Subscriber

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    That's it. The Rune of Tyr, Saxon War God.
    Used to designate Crown Property since before the Danes.
    And, yes. I knew you were kidding.

    I guess the Russian equivalent would be a Red Star and/or CCCP for USSR. Not expert on Soviet markings.

    ''Military No. 9 -3/4'' was a JK Rowling reference.

    Nicely fettled, by the way.
     
    Last edited: Feb 15, 2020
  10. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Parts stowed.

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  11. hikerduane

    hikerduane Subscriber

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    Thanks John, will steer away from these if I see one.
    Duane
     
  12. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @SveaSizzler
    A red star would have been a bit much, but the name ‘Prim’ in Russian script and a number 1 - signifying a 1st-rate stove or marks out of ten depending on your point of view - seems to work. The rectangular frame around the ‘1’ evidently signifies a unit number marked on military vehicles and white lettering and numbers is, or was, too.

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    Location on the fuel tank was chosen where it was less likely to scratch off stowing the tank in the box.

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  13. Twoberth

    Twoberth United Kingdom Subscriber

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    Very funny:D/
     
    Last edited: Feb 16, 2020
  14. gieorgijewski

    gieorgijewski Subscriber

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    TESTPRIM.JPG
    FUEL consumption test

    1 hour
    max power
    --------------
    results
    maximal consumption as 100%

    btw/ John look on thats PT2 works
     
  15. gieorgijewski

    gieorgijewski Subscriber

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    5:30
    simmer ?
     
  16. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @gieorgijewski
    I see it simmer Gieorgi but not knowing Russian, when Alex is pointing to the fuel pipe on the Prim I don’t know what he’s saying.

    Do you know what he did to get the Prim Compact to simmer?

    Interesting fuel consumption comparisons. Ogonek has a silent burner installed I see. Makes fuel consumption better? Worse? Same? I like the Ogonek, my favourite Russian stove. A Prim Compact that simmers might challenge it!

    John
     
  17. salan3

    salan3 United Kingdom Subscriber

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    I watched this vid on YT and put on captions with auto translate to English. Not perfect but helps a lot.
    Alan
     
  18. gieorgijewski

    gieorgijewski Subscriber

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    ok ill check it again

    but - after a few video:
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    "hole is big as the barn" - range of real simmer is very short
    half by half examples is "puffing"
    my -with bigger amplitude
    only 3 was with orange flame
    mostly wide "sunflower shape" blue
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    1 example - out of commentary ...
     
  19. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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  20. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    I have an idea for a way of restricting the flow of fuel better than that length of wire I tried in the fuel pipe.

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    I’ll report on how it goes.