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

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  • Donald Qualls
    ... 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
    Message 1 of 17 , Dec 1, 2007
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      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.
    • David Halfpenny
      ... From: Donald Qualls ... All good stuff, and worth remarking - for the benefit of Our new members in the subject line - that
      Message 2 of 17 , Dec 1, 2007
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        ----- Original Message -----
        From: "Donald Qualls" <silent1@...>

        >>>> the fundamentals of Mechanical Engineering on a postcard!

        All good stuff, and worth remarking - for the benefit of "Our new members"
        in the subject line - that very little of our traffic is this
        philosophical.

        We major in the sheer delight of simple little boats, whether mass produced
        from printed tinplate or cunningly homemade out of cardboard or balsa wood.


        My 'Rattanndeep Enterprise' tinplate Titanic fell out of the cupboard today
        (I caught her before she hit the deck).
        http://www.angelfire.com/extreme2/rattandeepenterprise/

        I took a look at her workings. The burner is a 7/8" diameter tinplate tray
        balanced precariously on the outlet pipes out of reach and out of sight,
        and very close to the underside of the pop-chamber. So I think it's fair to
        say that the chances of a successful run As Supplied are vanishingly
        small - par for the course I suppose ;-)

        I shall try to sail her in the kiddies' paddling pool in the park while
        it's too cold for kiddies to paddle, but not cold enough to be drained for
        the winter. I've got some brand new Wellies (gumboots) in case of
        emergency!

        David 1/2d
        Chartered Mechanical Engineer
      • brian458666@550access.com
        ... 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
        Message 3 of 17 , Dec 1, 2007
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          >
          > 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
        • Donald Qualls
          ... 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
          Message 4 of 17 , 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.
          • 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 5 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 6 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 7 of 17 , Jul 26, 2013
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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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