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Senft "Poppin" ENGINE

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  • The engine ran with previous test burner, it does not run with the new burner. This would indicate a burner/flame problem rather than a mechanical problem.

    The various videos indicate these engines are sensitive to flame position and shape, and that would be the area that i would explore.
    Jim H.

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    • Brian - Don't give up yet, it ran once it should run again.
      Did you not change the cylinder head since it ran ? If so maybe go back to the original head and valve to see if you can get it to go again.
      Larry - west coast of Canada

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      • I have watched about a hundred videos of Poppin engines in the last week. In a number of cases, the spring which holds the roller in contact with the cam is a tension spring connected to the 1/16" diameter arm which supports the valve. It runs vertically from the arm down to a screw tapped into the sub base. This is not what Dr. Senft calls for on his drawings of this engine. I'm curious as to why people do this. Does it put less load on the flywheels? Does it make the engine spin more freely? Is it part of a set of plans similar to Dr. Senft's?--Or is it just that some guys had a tension spring and not a piece of 0.020" music wire to make a spring like Dr. senft calls for?
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

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        • Just for grins here, and maybe it will spark some idea......

          These things run on a vacuum developed by a difference of temperature.

          Therefore, it seems likely that the idea would be to bring in the maximum amount of flame on the "suck-in" stroke. You undoubtedly realize that already, but that means there must be a burner type and position that allows for the maximum flame to be sucked in. Maybe you have not found it again since your first video of this engine running.
          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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          • The sun is shining---the birdies are singing--All is well at the Rupnow house!!! I finally got my Poppin to run the way I wanted. What did I do to make this happen? First of all I disconnected the valve mechanism completely and removed the con rod and piston. A flip of the flywheels would only make them run for about 15 seconds.---What?--That can't be right. I loosened off the two #2-56 bolts that clamp the straps on top of the bearings and tried again. Flywheels would now spin for over 60 seconds. I remounted the con rod and piston, and then the flywheels would spin for about 12 seconds. I remounted the valve mechanism and a flip of the flywheels would only make it free-wheel for about 3 to 4 seconds. I wasn't happy with the piece of 0.026" spring wire I had mounted as per Dr. Senft's instructions. (actually he called for 0.020" spring wire, but I was only able to get 0.026") I made up a hub for the "off" side of the cross-shaft and hooked up a very light tension spring to replace the .026" spring wire. At first the tension spring was too weak to totally open the valve, but I kept cutting off coils until it was just strong enough. that seems to have done the trick. Engine fired right up as you see in the video. I don't know what the honking and squealing noises are, but I put that down to the 0.002" thick valve. I don't care if it honks a bit.--I've got a runner!!!!!
            https://www.youtube.com/watch?v=UXn6...ature=youtu.be
            Last edited by brian Rupnow; 03-30-2018, 01:24 PM.
            Brian Rupnow
            Design engineer
            Barrie, Ontario, Canada

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            • Glad to see you cracked it - looks very smooth now
              If it does'nt fit, hit it.
              https://ddmetalproducts.co.uk
              http://www.davekearley.co.uk

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              • SUPER....

                Runs well. Cool.
                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


                • Well done. It's always the little things that get those "flea power" engines. Glad you found it.
                  At the end of the project, there is a profound difference between spare parts and left over parts.

                  Location: SF East Bay.

                  Comment


                  • Originally posted by Cuttings View Post
                    Brian - you don't say what you are holding the dies with. I made a die holder to fit in the tail stock of the lathe and find it works very well. Seems like you need a bit of constant pressure to get those little guys started, specially in harder metal. I keep the tail stock pressure on until I get at least a few threads started. The tail stock die holder also makes sure the die is square with the rod you are threading. Yes, sometimes I have to open up the die for the first cut, then if the thread is too tight I close it up a bit and make another pass until I like the fit of the thread.
                    Cuttings--I too have made die holders that fit into my tailstock chuck. A bit of pressure from the tailstock and turning the headstock chuck by hand makes the dies start and holds everything straight.
                    Brian Rupnow
                    Design engineer
                    Barrie, Ontario, Canada

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                    • I have had a bit of a chance to calm down since this mornings run, and set the engine up on an old textbook . That cuts down on a lot of the noise generated by the desk it is setting on (Like an echo chamber). The audio pickup on my camera is super sensitive, the engine runs much quieter than it sounds in the video. Most of the honking and squealing sounds have gone away.
                      https://www.youtube.com/watch?v=frwk...ature=youtu.be
                      Brian Rupnow
                      Design engineer
                      Barrie, Ontario, Canada

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                      • Great job Brian. Persistence usually always wins.
                        Larry - west coast of Canada

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                        • Nice Work Brian.

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                          • Nice job Brian! Very nice runner you made there! Thanks for sharing it with us!
                            Andy

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                            • Some of the flame eaters I seen on you-tube (Big Nick for example) have exhaust stacks on the cylinder. What's that about? Has anyone knowledge of why. Obviously it must help from blowing out the flame, but I would like some more information. Thank you in advance, Brian
                              Brian Rupnow
                              Design engineer
                              Barrie, Ontario, Canada

                              Comment


                              • Some of them seem to be for show or for the relief valve that some have. I've seen a number of them where the flame box doesn't even connect to the stack. so "it depends"... .

                                Reading your posts and the trials with the .002 thick intake valve I realized that the idea of using the shim stock is that the valve also can act like a pressure relief on the up stroke. Very clever of Mr Senft.

                                In looking at a large number of YT videos of flamelickers I noted that some really like to blow out their lamps or burners. But it seemed like the ones with shrouds seemed to get blown out as often as the ones without. And I didn't see enough with stacks that were part of the firebox to say if it helped or not.
                                Chilliwack BC, Canada

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