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Re: Membrane type engine cycle.

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  • Jean-Yves Renaud
    Hi Paul, The membrane pops up when the stress exerted on it by the pressure increases above its mechanical resistance. Similar in the other way. It is only a
    Message 1 of 3 , Jul 29 9:48 AM
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      Hi Paul,
      The membrane pops up when the stress exerted on it by the pressure
      increases above its mechanical resistance. Similar in the other way. It
      is only a matter of pressure and mechanical resistance. If you use a
      soft membrane (such as mylar) the engine will "pop" very easily but the
      sound will be weak. If you use a too rigid membrane the sound will be
      difficult to get. The best (loud) sound corresponds to a rigid membrane
      just soft enough to go up and down with the extreme HP and LP of the
      cycle. Slater's engines are a good example. Very often they miss
      some "pops" but each real one is a loud one.
      Jean-Yves


      --- In pop-pop-steamboats@yahoogroups.com, "lordbthry" <lordbthry@...>
      wrote:
      >
      > Welcome of course to the newcomers and thanks to Daryl for sharing
      > info and for his beautiful models.
      >
      > I think JeanYves honkhonk boat also quite interesting, it surely is
      > the first putt-putt boat I have ever seen with a turbocharger mounted!
      >
      > Now for the question, in a working membrane engine its obvious the
      > membrane pops up when water starts boiling and pops down when entering
      > fresh cold water. But I can't find anything about the precise popping
      > moment in the cycle. Does the incoming water have the benefit of
      > beneath atmospheric pressure (lower boiling point) or is the membrane
      > spoiling this while popping down?
      >
      > Paul M.
      >
    • Slater Harrison
      Paul, In addition to Jean-Yves good answer, you mentioned the boiling water expanding and popping up the membrane. Additionally, that expansion starts the
      Message 2 of 3 , Jul 29 11:46 AM
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        Paul,
         
        In addition to Jean-Yves good answer, you mentioned the boiling water expanding and popping up the membrane. Additionally, that expansion starts the column of water in the pipes moving ouotward. Even when the boiler is no longer pushing the water out, it continues because it has momentum (Newton's 1st law of motion). As the water in the pipe keeps moving, it actually creates low pressure in the boiler which pulls the membrane in. I am starting to create an animated video to show my students some of the reasons why the pop pops work.
         
        This page is in need of updating, but it discusses the cycle.  http://www.sciencetoymaker.org/boat/howBoatWorksl.html 
         
        Slater


        From: pop-pop-steamboats@yahoogroups.com [mailto:pop-pop-steamboats@yahoogroups.com] On Behalf Of Jean-Yves Renaud
        Sent: Tuesday, July 29, 2008 12:48 PM
        To: pop-pop-steamboats@yahoogroups.com
        Subject: [pop-pop-steamboats] Re: Membrane type engine cycle.

        Hi Paul,
        The membrane pops up when the stress exerted on it by the pressure
        increases above its mechanical resistance. Similar in the other way. It
        is only a matter of pressure and mechanical resistance. If you use a
        soft membrane (such as mylar) the engine will "pop" very easily but the
        sound will be weak. If you use a too rigid membrane the sound will be
        difficult to get. The best (loud) sound corresponds to a rigid membrane
        just soft enough to go up and down with the extreme HP and LP of the
        cycle. Slater's engines are a good example. Very often they miss
        some "pops" but each real one is a loud one.
        Jean-Yves

        --- In pop-pop-steamboats@ yahoogroups. com, "lordbthry" <lordbthry@. ..>
        wrote:

        >
        > Welcome of
        course to the newcomers and thanks to Daryl for sharing
        > info and for his
        beautiful models.
        >
        > I think JeanYves honkhonk boat also quite
        interesting, it surely is
        > the first putt-putt boat I have ever seen with
        a turbocharger mounted!
        >
        > Now for the question, in a working
        membrane engine its obvious the
        > membrane pops up when water starts
        boiling and pops down when entering
        > fresh cold water. But I can't find
        anything about the precise popping
        > moment in the cycle. Does the
        incoming water have the benefit of
        > beneath atmospheric pressure (lower
        boiling point) or is the membrane
        > spoiling this while popping
        down?
        >
        > Paul M.
        >

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