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

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  • David Halfpenny
    ... From: Donald Qualls ... OK then: An Infernal Confusion engine: - compresses a lump of air, - heats it up a lot - expands it
    Message 1 of 17 , Dec 1, 2007
      ----- 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)

      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

      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.
    • 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 2 of 17 , Dec 1, 2007
        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 3 of 17 , Dec 1, 2007
          ----- 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 4 of 17 , Dec 1, 2007
            >
            > 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 5 of 17 , Dec 1, 2007
              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 6 of 17 , Dec 1, 2007
                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 7 of 17 , Dec 1, 2007
                  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 8 of 17 , Jul 26, 2013
                    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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