Loading ...
Sorry, an error occurred while loading the content.
 

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

Expand Messages
  • Donald Qualls
    ... Well, at least as it stood ca. 1900, when internal combustion wasn t yet a major player in the prime mover game. In fact, most steam engines made over the
    Message 1 of 17 , Nov 30, 2007
      David Halfpenny wrote:
      > Jargon:
      >
      > A Stirling engine:
      > - compresses a load of gas (usually air),
      > - heats it up while compacted
      > - lets it expand (providing a power stroke)
      > - cools it down while expanded.
      > Repeat.
      >
      > A Rankine engine:
      > - boils a load of liquid (usually water),
      > - lets the steam expand (providing a power stroke)
      > - condenses it back into water
      > - pumps it back into the boiler.
      > Repeat.
      >
      > Either can be used either as a motor or be motor-driven to act as a heat
      > pump shifting heat from a colder zone to a warmer one. For example a
      > Rankine engine can be made either as a steam power plant or as a
      > motor-driven refrigerator.
      >
      > There have been a lot more Rankine engines built than Stirling engines
      > because it's a heck of a lot easier to pump liquid than to compress gas,
      > and because a lump of steam holds a lot more heat than a lump of air at the
      > same temperature.
      >
      > 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. In fact, most steam engines
      made over the past four hundred years have been an "open" version of the
      Rankine cycle, with the pump back to the boiler and often the condenser
      omitted in the interest of mechanical simplicity and/or reliability
      and/or lightness. I'm sure that's the case, because there have almost
      certainly been more steam engines built as locomotives and tractors than
      all other applications together, and virtually all of those are open cycle.

      Which, of course, doesn't change the elegance of an engine that can
      drive a tiny watercraft with no moving parts other than the working fluid...

      Worth noting relative to Stirling that the compression and expansion is
      typically a pretty small percentage of the volume; most of the designs
      I've looked at seem to run 3-5% volume change over the full stroke of
      the power piston. Steam, by comparison, has an expansion (if I recall
      correctly) of about 260:1 over the liquid phase; that makes steam
      engines capable of immense effort at very low speed (at least those that
      are designed for that kind of thing, minimum feature set including a
      variable cutoff valve gear) while Stirling is closer to an internal
      combustion engine in the way it runs -- that is, must keep up a pretty
      good rotational clip to run at all, because each power stroke produces
      relatively little energy.
      --
      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 ... Yes indeed - letting the condensing happen in the atmosphere and substituting alternative Working Fluid
      Message 2 of 17 , Nov 30, 2007
        ----- Original Message -----
        From: "Donald Qualls" <silent1@...>


        > most steam engines
        > made over the past four hundred years have been an "open" version of the
        > Rankine cycle, with the pump back to the boiler and often the condenser
        > omitted in the interest of mechanical simplicity and/or reliability
        > and/or lightness.

        Yes indeed - letting the condensing happen in the atmosphere and
        substituting alternative Working Fluid is technically cheating, just as
        leaving a turbine wake behind and ingesting substitute air is.

        > there have almost
        > certainly been more steam engines built as locomotives and tractors than
        > all other applications together, and virtually all of those are open
        > cycle.

        I'm sure you are right, but for such an influential piece of kit the number
        of steam locomotives built has been surprisingly few. I've not seen any
        estimate that exceeds a million. The humble pop-pop may well be (or soon
        become) more numerous!
        >
        > Which, of course, doesn't change the elegance of an engine that can
        > drive a tiny watercraft with no moving parts other than the working
        > fluid...
        >
        Absolutely! D
      • Donald Qualls
        ... Well, don t forget that most of steam s influence was in the days when a few dozen of something important could change the world. But look at what else
        Message 3 of 17 , Dec 1, 2007
          David Halfpenny wrote:
          > ----- Original Message -----
          > From: "Donald Qualls" <silent1@...>
          >
          >
          >> there have almost
          >> certainly been more steam engines built as locomotives and tractors than
          >> all other applications together, and virtually all of those are open
          >> cycle.
          >
          > I'm sure you are right, but for such an influential piece of kit the number
          > of steam locomotives built has been surprisingly few. I've not seen any
          > estimate that exceeds a million. The humble pop-pop may well be (or soon
          > become) more numerous!

          Well, don't forget that most of steam's influence was in the days when a
          few dozen of something important could change the world. But look at
          what else steam has done -- powered ships (the bulk of which after about
          WWII ran turbines instead of steam expanders) and operated stationary
          power installations (either electric generation -- again, virtually
          always turbine -- or things like mine engines); both of those are surely
          fewer in number than even locomotives. One could make a case that there
          have been more model steam engines built than there ever were full size
          ones, though I don't know where you'd get the figures to back it up...

          --
          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 ... OK then: An Infernal Confusion engine: - compresses a lump of air, - heats it up a lot - expands it
          Message 4 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 5 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 6 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 7 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 8 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 9 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 10 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 11 of 17 , Jul 26 5:17 AM
                          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.
                          >
                        Your message has been successfully submitted and would be delivered to recipients shortly.