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Senft "Poppin" ENGINE

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  • #31
    Again, lookin great Brian.

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    • #32
      Originally posted by brian Rupnow View Post
      Not a great deal done today, as I had a few hours of "real" work. I did however manage a pair of flywheel hubs and their accompanying nuts. (I cheated on the nuts---took a pair from my tool-chest and thinned them down on the lathe.) I have never seen flywheels made this way before, but it seems to work okay.


      Is one flywheel copper and the other brass?


      Watching again in anticipation of a good runner!

      I finally found out the name of the "flame engine" that has sparked my interest in flame engines. They are called "pop-pop boats". Where I saw my first one was in an old Japanese animated film my children were watching years ago. Unlike most cartoons this film was accurate and didn't "lie" to the kids. It was quite an interesting cartoon actually and they explained how the pop-pop boat they were using worked.

      Ever since flame engines have fascinated me. The pop-pop boat isn't exactly an "engine" but more of a steam boiler. But the idea of slipping a candle under a dead simple chamber and it moves the boat is amazing to me.
      Andy

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      • #33
        Yes, good eye--One is brass and one is bronze. I had a pop-pop boat when I was a little kid.
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

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        • #34
          You can still buy them. I've got a couple in the fleet.
          Set up a piece of gutter on some saw horses and the neighborhood kids just go wild.


          https://www.ebay.ca/itm/CANDLE-POWER...UAAOSw3fpap0Lg
          Home, down in the valley behind the Red Angus
          Bad Decisions Make Good Stories​

          Location: British Columbia

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          • #35
            I've wondered for years about making a life size pop pop boat... I'm sure the engine would not scale well, but the looks you'd get going around the lake would be awesome.

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            • #36
              In full size, the "pops" might be a bit bigger, but further apart....

              I have seen the "engine" of the toy size as a box with one or two tubes out the back, and as just a 1 1/2 turn coil of small tube. Starting at the transom below water line, tube comes in, goes straight for about 2 x as far as the bend diameter, then is bent around 1 1/2 turns, and run back to the transom at the same level as the other end.

              The candle etc is under the back part of the coil, between the straight sections, where there is just one tube. That puts it in the middle of the total tube length.
              CNC machines only go through the motions.

              Ideas expressed may be mine, or from anyone else in the universe.
              Not responsible for clerical errors. Or those made by lay people either.
              Number formats and units may be chosen at random depending on what day it is.
              I reserve the right to use a number system with any integer base without prior notice.
              Generalizations are understood to be "often" true, but not true in every case.

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              • #37
                It seems to me that there was no absolute reason that pop-pop boats ran, from a scientific point of view. They definitely do run, and many theories have been advanced as to the actual "why" but it is still a bit of a scientific oddity. Maybe my knowledge is way out of date on this factoid, but I do remember reading that sometime in the last 71 years.---Brian
                Brian Rupnow
                Design engineer
                Barrie, Ontario, Canada

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                • #38
                  I believe the cycle is as follows:-

                  Candle heats tube before boat is placed in water.

                  When boat placed in water water flows in the tube until it reaches the hot spot whereupon water flashes to steam and pushes the water out..

                  Inertia of the exiting water causes slight vacuum in the tube which draws in more water for another cycle.

                  Others say tube must be filled and boat put in water prior to lighting candle.
                  Last edited by The Artful Bodger; 03-16-2018, 10:05 PM.

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                  • #39
                    I had one.

                    As I recall, you DID fill the tube first, which makes sense. If not filled, you had to get some water in it and get it to the back coil where the candle is. Then the steam would blow out the air, and water would suck back in, and be heated until the cycle repeated.
                    CNC machines only go through the motions.

                    Ideas expressed may be mine, or from anyone else in the universe.
                    Not responsible for clerical errors. Or those made by lay people either.
                    Number formats and units may be chosen at random depending on what day it is.
                    I reserve the right to use a number system with any integer base without prior notice.
                    Generalizations are understood to be "often" true, but not true in every case.

                    Comment


                    • #40
                      Originally posted by brian Rupnow View Post
                      It seems to me that there was no absolute reason that pop-pop boats ran, from a scientific point of view. They definitely do run, and many theories have been advanced as to the actual "why" but it is still a bit of a scientific oddity. Maybe my knowledge is way out of date on this factoid, but I do remember reading that sometime in the last 71 years.---Brian
                      They run because the outflow is in the form of a jet, whereas the inflow is a hemispherical convergence (a "sink" flow). The momentum of the jet in pushing is much stronger than the momentum of the inflow in the opposite direction.
                      Last edited by aostling; 03-17-2018, 01:28 PM.
                      Allan Ostling

                      Phoenix, Arizona

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                      • #41
                        My ball bearings came in yesterday. They are shielded bearings, not sealed. They should turn more freely than sealed bearings because the shields don't really touch the inner race. I may still have to wash the grease out of them in a solvent bath--will know about that later. Today I hope to make the crankshaft.
                        Brian Rupnow
                        Design engineer
                        Barrie, Ontario, Canada

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                        • #42
                          So, here we have crankshaft phase-1. Everything is cut to length and Loctited together. The shafts are not "press fit" into the square bars. They are a sliding fit. After 24 hours set-up time I will and pin all the joints with 1/16" dowels (Loctited into place), then wait another 24 hours and saw out the center bit.
                          Brian Rupnow
                          Design engineer
                          Barrie, Ontario, Canada

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                          • #43
                            I decided not to use any J.B. Weld on the flywheel hubs. That would have been a bit too barbaric, even by my standards. I made the cam and cam spacer this afternoon, assembled everything and tightened it down as much as I dared, then set the flywheels up one at a time on a stub shaft with their hub assemblies in place and "trimmed" the outer diameter and the sides of each flywheel. It didn't take much, but it did take some. Now the flywheels don't visibly run out or wobble.
                            Brian Rupnow
                            Design engineer
                            Barrie, Ontario, Canada

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                            • #44
                              This engine has a very interesting big end on the con rod. I haven't built one like this before. The red con-rod is silver soldered to the pale yellow part on the right hand end. The pale yellow part on the right is fastened to the pale blue part on the right with cyanoacrylate glue before any holes are made. Then both yellow and blue parts are tapped all the way through. A bolt is screwed through both parts and tightened. Then the hole is drilled and reamed for the crank journal on the split-line between the two pieces. Then the bolt is removed and the assembly is heated to release the crazy glue.
                              Brian Rupnow
                              Design engineer
                              Barrie, Ontario, Canada

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                              • #45
                                This morning I got up and pinned the crankshaft. In a perfect world, I would have drilled the four holes undersize, then reamed them to 1/16" diameter.--In my world, the smallest drill I could find was 1/16" diameter, so that's what I used. In the foreground on top of the vice you can see the four "pins" prepared to go into the holes. The pins are flat on one end and a small taper ground on the other end, and about 1/4" longer than they need to be. First I tried the pins in the holes for fit and yes, they did fit perfectly. Then a small drop of Loctite on each hole, and the pins are inserted pointy side first and brought down until the top of the pin is flush with the side of the crank journal. In the second picture, the pins have been inserted and you can see the extra length extending below the underside of the crankshaft. If the four pins look a bit like welding rod, that's because they are. I can only buy 1/16" rod as "music wire" which is harder than the devil's horn to work with. However, somebody on the forum suggested 1/16" steel, copper coated welding rod, which is perfect for what I'm doing here.

                                Brian Rupnow
                                Design engineer
                                Barrie, Ontario, Canada

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