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Re: World's fastest putt putt engine?

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  • jeanyves_renaud
    Hi Zoomkat, The thrust delivered by an optimized pop-pop engine is roughly proportional to its tube ID and to the number of tubes. Optimizing requires time
    Message 1 of 40 , Jul 5, 2010
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      Hi Zoomkat,
      The thrust delivered by an optimized pop-pop engine is roughly proportional to its tube ID and to the number of tubes. Optimizing requires time because many parameters are to be adjusted: tube length, boiler volume, tube slope and bends, materials for tube and boiler, thermal isolation, gas content (other than steam), heating power, nozzle shape and diameter…
      My big engines (ID 18mm and 23.5mm) work almost endlessly. The biggest engine I know (the one built by Eljoh and Jorn) uses a 2" pipe (ID=54mm) and a big boiler. I do believe that a drum lid engine can work. However, be prepared to spend time if you expect to optimize it and don't forget that any diaphragm deteriorates the thrust. I built approx hundred engines and most of them have been modified (length, slope, bends, isolation, heating power…) to determine the influence of various parameters; and there is still much to learn to optimize most of them. Slater built 300 prototypes to come up with his cheap and performing pop-pop boat. Daryl tested many alternatives to get his performing engines (which are the best I know).
      Patience and good luck!


      --- In pop-pop-steamboats@yahoogroups.com, "zoomkat" <Zoomkat@...> wrote:
      >
      > --- In pop-pop-steamboats@yahoogroups.com, Slater Harrison <Sharrison@> wrote:
      > >
      > > I just have to say, this ongoing discussion of theory and scaling up is particularly fascinating. I am often asked about scaling up engines (I present the instructions for making engines from aluminum cans, epoxy and straws). I struggle to explain why you can't simply quadruple the size of the engine and flame, and expect to quadruple the power--in everyday vocabulary. This gives me a new way to help people grasp the idea.
      > >
      > > Slater
      >
      > I think some of the short commings of pop pop engine development is that engines that actually run well haven't been closely studied to find the keys as to why they run well as opposed to other designs that don't. Daryl's engines, Slaters engines, Indian boat engines, and copper coil engines generally run well and have consistant performance. A common factor is that they are generally in the same size range. An uncommon factor is that they have significantly different mechanical arrangements, yet generally work well. I think one of the more interesting things to pass thru the forum is Daryl's coffee maker engine. It appeared to run strong and consistantly even though it is significantly larger than the typical engines. My next project may be to see if I can duplicate the coffee maker engine and do some study of what is critical for its operation. Still interested in being the first with a working "drum lid" pop pop engine.
      >
    • jeanyves_renaud
      Hi Slater. I agree with Daryl. It is a nice page on your great site. I would comment only one sentence. it is All these friends I ve quoted, and dozens more,
      Message 40 of 40 , Jul 6, 2010
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        Hi Slater.
        I agree with Daryl. It is a nice page on your great site.
        I would comment only one sentence. it is "All these friends I've quoted, and dozens more, are members of an informal e-mail group of pop pop enthusiasts scattered around the world.". There are dozens of pop-pop enthousiasts to talk and write on forums... but I think we are a very few (one dozen?) real amateurs spending time to develop pop-pop engines or/and pop-pop boats.

        --- In pop-pop-steamboats@yahoogroups.com, "darylcanada73" <darylcanada73@...> wrote:
        >
        > Nice page Slater and a good addition to your great site. I wish I had been able to read a page like it when I first started building. And thanks for the link.
        >
        > Daryl.
        >
        > --- In pop-pop-steamboats@yahoogroups.com, Slater Harrison <Sharrison@> wrote:
        > >
        > > Hi Gang,
        > >
        > > I have added a new page, http://www.sciencetoymaker.org/boat/BigPopPopBoat.htm just about scaling up. My apologies to David, Jean-Yves and Daryl for cutting and pasting stuff shamefully-under a bit of time pressure. Where I've goofed, let me know and I'll get it worked out. Understand that it's not supposed to be a comprehensive study of scaling, rather it's to let them know I don't have the answers. And if they want to know more they really need to get connected with the group.
        > >
        > > I've reprinted the gist of what's in the page below: Titles, Daryl's embedded page did not transfer.
        > >
        > > Slater
        > >
        > >
        > >
        > >
        > > So You Want to Build a Giant Pop Pop / Putt Putt Boat?
        > >
        > > Before delving into scaling up the engines, I insist that you learn a new word: serendipity. Serendipity means we go looking for one thing, and perhaps we don't find exactly that thing. But-if our minds are flexible enough to be open to it-we find something as good or better in the process of looking.
        > >
        > > OK, many intelligent, curious people have wondered, "If pop pop boats are this cool, how cool would it be to make a person-sized pop pop boat?!" In fact, the idea has even seeped into popular culture. In the children's animated movie Ponyo, the young heroes use magic to transform a toy putt putt boat into a big boat and ride in it.
        > >
        > > Alas, those of us who are lacking in magical powers have to grapple with the persnickety laws of nature.
        > >
        > > My friend David Halfpenny from England has some interesting things to say about the difficulty and hope of scaling up in general: I quote,
        > >
        > > "There's a critical size for everything in nature. That's why you'll never see a moth as big as a dog - the insect respiration system just can't get enough oxygen."
        > >
        > > "There's an old joke that goes:'According the laws of aerodynamics, a bumblebee cannot fly. Fortunately nobody has told the bee.'Well actually, bees cannotfly, not like a bird or a plane - they 'swim' through the air, which, at their small size and low weight, is much stickier than it is to us. Or a bird. Or a dog. So that means there must be a crossover between Insect Size 'lungs' and Dog Size lungs, and sure enough you can get a beetle as big as a mouse."
        > >
        > > "In a wind tunnel (used to simulate aircraft flight), the airspeed isn't scaled in the same ratio as the aircraft model size. In an oil tunnel (used to understand insect-sized flight), the fact that oil has to be used instead of air speaks volumes about what it's like to be an insect."
        > >
        > > "It means there must be a crossover between Gnat Flight and The Flight of the Condor, and sure enough there is the Humming Bird - a bird so small it can swim though air as well as glide, and so skilled it can hover."
        > >
        > > Then my friend Jean-Yves Renaud from France adds some specifics:
        > >
        > > Building a half meter engine should not be a problem. My bigger one (just to check that there is no limit) was approx 3m long. However, I must warn you about the performances. When the size of the engine increases, its thrust/weight or power/volume ratios decrease. In other words, for the same weight two small engines are better than a big one. The thrust doesn't increase much with the pipe ID though the weight does as well as the volume. The velocity of the jet decreases when the size of the engine increases. Multiple pipe engines and or multiple engines are to be preferred if performances (speed and thrust) are expected.
        > >
        > > Jean-Yves has also measured the efficiency of pop pop engines and found them wanting. And he notes that pop pops do not reverse, and questions how long the appeal of being shaken back and forth several times a second will remain amusing.
        > >
        > > From Canada, my friend Daryl Foster has created some extraordinary boats with many pipes. Look half a minute into this video and see the new world record holder for speed. Even vetran pop pop builders are amazed http://www.youtube.com/watch?v=9rt1l-zmCug
        > >
        > > So, at top of the page, what was all that about serendipity-discovering things while looking for something else? All these friends I've quoted, and dozens more, are members of an informal e-mail group of pop pop enthusiasts scattered around the world. Despite the fact that I have only met one of the members in person, I do mean friends. We share a common bond. These charming boats have tickled our imagination we're all and curious about what are the possibilities? There's the serendipity. If you've come to this page you might not have found an easy answer the question of scale, but you have discovered a community of people who are finding out.
        > >
        > > I rarely participate, but I get the e-mails automatically and I stay abreast of what's going on. Sometimes the chatter is about a new discovery, sometimes there's a contentious issue, sometimes there's humor, sometimes the group goes into hibernation, sometimes the topics go careening delightfully off topic, and sometimes we welcome new members. So consider joining. It's a Yahoo group that you have to join, but it's free, and-other than being hosted by Yahoo for administrative convenience-non-commercial. As you might expect, there's great archived threads and pictures.
        > >
        > > http://groups.yahoo.com/group/pop-pop-steamboats/
        > >
        > >
        > >
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