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Re: [pop-pop-steamboats] Our new members

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  • brian458666@550access.com
    ... Yes, I had completely forgotten about the stovetop variety and was going with the electric ones only. Most of the electric percolators used a small boiler
    Message 1 of 17 , Dec 1, 2007
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      Quoting Donald Qualls <silent1@...>:

      > brian458666@... wrote:
      > >
      > >> There are actually a couple valveless pulse jets that are even closer to
      > >> a pop-pop in operation;
      > >
      > > Yes, and I had a moment of illumination just now as I was loading up
      > my
      > > coffee maker...although it does use a check valve, and the older style
      > > percolators used a restricted inlet to work.
      > > Brian
      >
      > I've got a stovetop type percolator that has a very broad, flat funnel
      > covering the base and feeding into the vertical pipe, with liquid flow
      > under the funnel permitted only through a couple tiny openings or under
      > the edge if a pressure pulse should lift the pipe and basket clear of
      > the pot base. The electric percolator I used to own had a rather tiny
      > boiler chamber, roughly hemispherical, under the base of the pipe, and
      > again a couple small openings to admit liquid. To my eye, they depend
      > on the bulk of liquid in the pot being fairly well below boiling, so it
      > takes a few seconds (even when the pot has begun to perk) for inflowing
      > liquid to boil, after which rising bubbles push liquid out the top of
      > the pipe; as the coffee heats, bubbles push smaller and more frequent
      > slugs of liquid into the dome to drip through the grounds until the pot
      > stops working at all when the liquid is very close to boiling -- just
      > steam comes up the pipe, because the liquid can't fill the working
      > chamber, much less the pipe, before it boils.
      >
      > An automatic drip coffee machine (a la Mr. Coffee) works similarly but
      > with a limited supply of water; mine seems to have an unrestricted
      > intake from the tank, and depends on the temperature of the water supply
      > to regulate the rate of boiling, which in turn regulates the temperature
      > of the water that gets poured into the grounds basket. It's a little
      > topsy-turvy, though; start with water that's too warm and you'll get
      > mostly steam and poor flow through the pipe, while starting with icy
      > cold water gives the best coffee because you get good slugs of water and
      > they heat up just right before the hot spot boils and pushes them
      > through. This pot, however (mine's a Melitta), seems to depend strongly
      > on the inertia of water in the tank as well as on heating most strongly
      > near the intake to produce a useful pumping action. I didn't see
      > anything I could identify as a check valve when I had it apart for
      > cleaning after a period of disuse...

      Yes, I had completely forgotten about the stovetop variety and was going
      with the electric ones only. Most of the electric percolators used a small
      boiler of under an inch in diameter that was at the very bottom of the pot. I
      haven't seen or used one of those in many years and further details are elusive
      now, and my Mr. Coffee type devices get a lot of use. It seems that each
      manufacturer incorporates their own flaws so my standard backup is a french
      press. But all of mine have check valves molded into the bottom of the
      reservoir.
      Brian
    • Donald Qualls
      ... I ll have to go look at mine; I couldn t get some pieces apart (they seem to be assembled with one-time latch-in parts, you d break them before they d
      Message 2 of 17 , Dec 1, 2007
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        brian458666@... wrote:

        > It seems that each
        > manufacturer incorporates their own flaws so my standard backup is a french
        > press. But all of mine have check valves molded into the bottom of the
        > reservoir.

        I'll have to go look at mine; I couldn't get some pieces apart (they
        seem to be assembled with one-time latch-in parts, you'd break them
        before they'd fully disassemble), so it's very possible it has a check
        valve I missed. That would make a lot more sense in terms of avoiding
        bubbling back up through the tank, and it would only need a small
        plastic ball trapped in the joint between two pieces.

        --
        If, through hard work and perseverance, you finally get what you want,
        it's probably a sign you weren't dreaming big enough.

        Donald Qualls, aka The Silent Observer http://silent1.home.netcom.com

        Opinions expressed are my own -- take them for what they're worth
        and don't expect them to be perfect.
      • Double Diamonds
        i was also looking into the possibility of using pulse-jet designs to improve on putt-putt engine work and was considering that it might allow for a faster
        Message 3 of 17 , Jul 26 5:17 AM
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          i was also looking into the possibility of using pulse-jet designs to improve on putt-putt engine work and was considering that it might allow for a faster engine cycle and quiet running from the lack of a diafram might allow more speed

          --- In pop-pop-steamboats@yahoogroups.com, Donald Qualls <silent1@...> wrote:
          >
          > David Halfpenny wrote:
          > > ----- Original Message -----
          > > From: "Donald Qualls" <silent1@...>
          > >
          > >>> There: the fundamentals of Mechanical Engineering on a postcard!
          > >> Well, at least as it stood ca. 1900, when internal combustion wasn't yet
          > >> a major player in the prime mover game.
          > >
          > > OK then: An Infernal Confusion engine:
          > > - compresses a lump of air,
          > > - heats it up a lot
          > > - expands it (providing a power stroke)
          > > - lets it escape along with the products of combusion (which may also
          > > provide a reaction thrust)
          >
          > Of course, this cycle, like the Rankine, can be used either in "batch"
          > mode or in "continuous" mode. Common piston, rotary, and pulse-jet
          > engines operate in pulsed or "batch" mode, where a discrete "lump" of
          > working fluid goes through the entire cycle independent of other
          > charges, while ramjets, turbojets and turbofans and at least one variant
          > piston engine (an internal combustion version of an elbow engine)
          > operate in continuous mode, where all parts of the cycle operate on a
          > flowing stream of working fluid (rather like the difference between pot
          > distillation and a distillation column, or lab synthesis vs. an
          > industrial process).
          >
          > > The one closest to the pop-pop is the pulse-jet or doodelbug engine, which
          > > also uses an oscillating column of fluid in a backwards-pointing tube. (My
          > > parents weren't very fond of these as they were married in London in August
          > > 1944.) In this case, the resonant pressure wave opens and closes the air
          > > inlet valve, sucks in and atomises the liquid fuel and compresses the
          > > ingested air. Ignition is usually by contact between the explosive mixture
          > > and the hot walls of the combustion chamber.
          > > The result is very simple and powerful model boat engine that is several
          > > decibels noisier than a pop-pop
          >
          > The classic valved pulsejet actually has a front intake and almost
          > entirely one-way flow, and model airplane versions have a venturi
          > carburetor built into the intake at the forward end (the German design,
          > too large to work well with a flat reed valve, incorporated the fuel
          > delivery into the grid that held the valves, so didn't as much resemble
          > a simple venturi carburetor).
          >
          > There are actually a couple valveless pulse jets that are even closer to
          > a pop-pop in operation; all compression and flow control is due to
          > pressure pulses in resonance with the pipe, and both pipe openings face
          > backward and produce thrust (though the designs I've seen have them
          > different lengths and the overall flow is from the shorter pipe to the
          > longer; there has to be some directional flow to keep drawing in fresh
          > air and fuel and removing combustion products, of course, but it could
          > be worth testing to see if this would be the case with our kind of
          > pop-pop, since tuning the tubes to product directional flow has the
          > potential to greatly increase the efficiency of the engine). The
          > resonance frequency in these, in hobbyist scales, tends to be in the
          > mid-upper audible range, leading them to produce a very distinctive
          > screaming sound in addition to the usual loud roar of any jet exhaust.
          >
          > > David 1/2d
          > >
          > > There are one or two additional details, but the core science behind post
          > > mediaeval Mechanical Engineering isn't mechanics, or mechanisms, or
          > > materials, important as they all are: it's thermodynamics.
          >
          > Yep, pretty much anything invented since James Watt improved the pumping
          > engine at the mine where he worked (by inventing, out of laziness, an
          > automatic valve gear to replace the continuous attention of a boy)
          > depends on thermodynamics, at least until you start getting into
          > practical electricity in the late 19th century. At that point,
          > Maxwell's laws of electromagnetism become the important ones...
          >
          > --
          > If, through hard work and perseverance, you finally get what you want,
          > it's probably a sign you weren't dreaming big enough.
          >
          > Donald Qualls, aka The Silent Observer http://silent1.home.netcom.com
          >
          > Opinions expressed are my own -- take them for what they're worth
          > and don't expect them to be perfect.
          >
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