SRV Cap Tester/Setter

Discussion in 'Fettlers Master Class' started by BernieDawg, Sep 11, 2012.

  1. BernieDawg Banned

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    Put this device together the other day for an extremely knowledgeable expert on the Svea 123/123R. It's a dressed up version of the rig I use here in the BD Labs to set SRV's using my shop made penta-wrenches. The regulator and gauge are from Harbor Freight. The plumbing and air components are off-the-shelf from Home Depot. The cap mount is lathe turned and threaded here in the Labs as are the two aluminum regulator spacers. The aluminum angle plate is from the metal recyclers, dust-blasted and sprayed with three coats of auto lacquer. Designed to be hooked up to an air compressor, it could be used with a static air tank or a large truck tire. In use, a container of water can be put under the cap mount "U" so that the cap is submerged and the pressure can be dialed in with the penta-wrench by watching the gauge and looking for bubbles out the SRV.

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  2. bajabum

    bajabum R.I.P.

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    Slick! :thumbup:
     
  3. dwarfnebula

    dwarfnebula United States Subscriber

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    Sir, you are officially a badass.

    Out of curiosity, what pressure have you decided to set the blow-off at? I'm not even sure what kind of pressure they operate at, I'd imagine it's fairly low, at least compared to say a coleman stove.
     
  4. BernieDawg Banned

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    Oh now. :oops: I don't think I can live up to that! :lol:
    http://www.imdb.com/media/rm1242740480/tt1928330

    I set the caps to begin releasing pressure at 40psi and be pretty much full open by sixty psi. The 1915 Svea catalog here in the Reference Gallery makes the claim that every Svea stove was tested at the factory to a pressure of four atmospheres.
    https://classiccampstoves.com/fusion/gallery/15/1264858204-2.jpg

    An atmosphere is right about 15psi. Four atmospheres would be about sixty psi. So, 40psi is about two thirds the pressure that stoves were actually brought to in 1915. Later Svea catalogs indicate the tradition of pressure testing continued over the years. The stoves of that era were assembled with soldered joints. The 123s, 8s and 111s have tanks assembled with brazed joints and should be somewhat stronger.

    It is my feeling that 40psi is a goodly safety margin. For the record, I have pressurized the 123, 8, and 111 tanks to significantly higher pressures for brief periods. I won't say how high. But, no one should try this stuff if you don't agree with the analysis I've suggested. I feel confident that my setting of the safety caps is well within a reasonable margin of safety and probably is overly conservative. In any case, it's my feeling that a SRV that functions is better than one that does not.

    Sorry to get wordy - a disclaimer seemed in order. Realize that I have no certain knowledge of the proper pressure. If you choose to abide by anything I've said you do so completely at your own risk.
    Cheers,
    Gary
     
    Last edited by a moderator: Jul 1, 2015
  5. dwarfnebula

    dwarfnebula United States Subscriber

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    I was actually contemplating building one of those for myself, but to work off of a bike pump. I don't have access to a lathe so I figured I'd have to wait for a trashed tank to canibalize, that has not materialized.

    Have any interest in renewing a pump cap for me? :lol:
     
  6. BernieDawg Banned

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    Heya Dwarf
    Well.... I don't think a bike pump alone is gonna work for you. You'd need a reservoir tank to go with it. Those are available from Harbor Freight for under $30.
    I can turn the cap fitting for you on the lathe if you are interested. A PT is the way to go on that. Likewise, cap setting - send me a PT.
    Cheers,
    Gary
     
  7. hikerduane

    hikerduane Subscriber

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    Gary, the cap on my Campingo was received soldered over, can that be resurrected you think if all the major pieces are there? Not a big deal to me as the stove doesn't get used for long periods or with large pots to cause the tank to heat up. Also, it has not been used but one time by me. Regular flame thrower those burners are!
    Duane
     
  8. Rob McMillan United States

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    4110DAEB-0D59-4551-8D1E-53D63741861B.jpeg

    Before I disassembled my Svea 123 srv, I thought I’d check to see how much force it took to start to open the relief valve. This is WAY less reliable a measurement than what BernieDawg did in this thread, but it was curiosity driven and I thought I’d share. And, I think I’ll count turns of the Penta screw on disassembly / reassembly. Easiest horseshoes and hand grenades way to get it close. My experiment was to get a number, not make reassembly safer.

    What you see in the picture is a pretty reliable scale, set to grams. The cap, paperclip and cloth were set to zero weight at first, and what I was measuring was the downward force on the cap. Upon release, I could feel (or not feel) the spring move to reset itself. After about 20 iterations, I got a feel for it and estimate that it takes about 225-250 grams of force to open the spring partially.

    Hope this helps someone, sometime.
     
  9. snwcmpr

    snwcmpr SotM Winner Subscriber

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  10. Rob McMillan United States

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    You have amazing depth of knowledge on this site!
     
  11. snwcmpr

    snwcmpr SotM Winner Subscriber

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    No, but "I know a guy".
    Stick around and you will find out who has the real depth of knowledge here. I just copy what the smart people do.