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1075Re: [pop-pop-steamboats] Our new members

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  • Donald Qualls
    Dec 1, 2007
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      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...

      --
      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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