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Senft "Poppin" ENGINE

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  • #46
    Have been building a whole armada of tiny little pieces. Valve shaft bushings, valve cross shaft, valve lever arm. I still have half a dozen little pieces to make. I just realized that I polished the wrong side of the cylinder head and installed it backwards. The taper in the center should face into the cylinder, not outward as I have it. The crankshaft does indeed fit into the engine frame but barely. I had to order a 0-80 die and a 2-56 die, as I need them and don't have them. I downloaded these plans from the John-Tom site, and while the mechanical drawings are clear enough to see, the pictures are horrible. If anyone has built this engine, please post a nice clear picture of where the spring that holds the valve open goes. I can't tell from the stuff I downloaded. I think I will try to build the roller and roller carrier that goes on the end of the valve lever this afternoon and then call it a day.
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

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    • #47
      PM me your email and I'll send that photo

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      • #48
        Originally posted by Bmyers View Post
        PM me your email and I'll send that photo
        [email protected] ---and thank you.---Brian
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

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        • #49
          Photos sent, let me know if you need any more.

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          • #50
            I lapped the cylinder this afternoon, but wasn't terribly impressed with the resulting finish on the bore. I used a home made 5/8" lap that I had turned from a piece of aluminum. I had to take a step back and ask myself "Why am I still doing design work for money?"--It was supposed to be money designated for additional tooling in my machine shop. So---I just ordered a set of five barrel laps from KBC. I have one factory built lap that I bought a few years ago for 15/16" bores, and I was very pleased with the results it gave. I ordered a 1/2", a 5/8", a 3/4", a 7/8", and a 1". Sometimes you just gotta spend some money!!
            Brian Rupnow
            Design engineer
            Barrie, Ontario, Canada

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            • #51
              Originally posted by Bmyers View Post
              Photos sent, let me know if you need any more.
              Thank you BMyers---I received the picture, and it helps a lot.---Brian
              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

              Comment


              • #52
                This morning I finished detailing the crankshaft. I used a pair of "flush cut" wire cutters to snip of the exposed ends of the 1/16" diameter cross pins , then used my monster stationary belt sander to clean up both sides. Before I cut the remaining piece of shaft out from between the rectangular bars, I chucked one end in the lathe and with my dial indicator on the unchucked end I measured 0.016" total runout. This didn't concern me too much, as these small shafts (3/16") are really flexible fliers. I took my rubber hammer and applied it to the shaft until the runout was only .002" total indicated runout. after I cut away the shaft between the rectangular crank throws, I measured again and it hadn't changed any. So---The crankshaft is finished.
                Brian Rupnow
                Design engineer
                Barrie, Ontario, Canada

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                • #53
                  Some very delicate work indeed going on here. This is the arm that operates the valve on the front of the cylinder. The arm is 1/16" thick material. The roller that you can see is 5/16" diameter. The axle inside that you can't see is .175" diameter with a .062 spigot that goes thru the arm.--And the roller has to turn freely after it is all assembled. The plans call for "peening" the head of the 1/16" part which extends thru the arm. I have never had a whole lot of luck with peening one part of an assembly while still leaving the other part free to rotate. I wimped out and silver soldered the projecting 1/16" spigot.---And my roller does spin freely!!
                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

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                  • #54
                    I'm having to retool my shop just to build this engine. So far I've had to order a #2-56 die, a 0-80 die and a tap, and I've found that nobody in Barrie carries 0-80 hex nuts. I'm working below my comfort level, size-wise, but so far it's coming together well.
                    Brian Rupnow
                    Design engineer
                    Barrie, Ontario, Canada

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                    • #55
                      Brian:

                      Those parts are big. THIS is getting kinda small :

                      CNC machines only go through the motions

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                      • #56
                        Jerry--You'll get no argument from me on that one!!!
                        Brian Rupnow
                        Design engineer
                        Barrie, Ontario, Canada

                        Comment


                        • #57
                          Okay, I'd be the first one to agree, at first glance this looks uglier than original sin. Both brass pieces of the two piece big end have been carved out, one being silver soldered to a 3/32" diameter cold rolled steel rod (which I had to turn from 1/8" steel rod because I don't stock anything that small.) They are currently crazy-glued together and later today I will tap them while still crazy glued together, insert a full thread #2-56 bolt thru all, then drill and ream the hole for the con rod journal. Seems like a very strange way to make a con rod big end, and yet it doesn't require anymore pieces than a "normal" con rod big end does. It does cut down quite a lot on the "swing radius" of the con rod assembled on the crankshaft.--It is setting on a bigger aluminum block covered with saran wrap so that I don't glue it to the big aluminum block with a couple of 0.015" thick shims under them to maintain alignment .
                          Brian Rupnow
                          Design engineer
                          Barrie, Ontario, Canada

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                          • #58
                            Originally posted by brian Rupnow View Post
                            Okay, I'd be the first one to agree, at first glance this looks uglier than original sin. Both brass pieces of the two piece big end have been carved out, one being silver soldered to a 3/32" diameter cold rolled steel rod (which I had to turn from 1/8" steel rod because I don't stock anything that small.) They are currently crazy-glued together and later today I will tap them while still crazy glued together, insert a full thread #2-56 bolt thru all, then drill and ream the hole for the con rod journal. Seems like a very strange way to make a con rod big end, and yet it doesn't require anymore pieces than a "normal" con rod big end does. It does cut down quite a lot on the "swing radius" of the con rod assembled on the crankshaft.--It is setting on a bigger aluminum block covered with saran wrap so that I don't glue it to the big aluminum block with a couple of 0.015" thick shims under them to maintain alignment .
                            I guess I don't understand why you don't modify the rod arrangement if you don't like it?
                            You should have the skills to do that??

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                            • #59
                              I never said I didn't like it. It's just very strange, that's all. It's uglier than original sin right now because it looks weird and isn't finished. By the time I'm done with it Sid, it'll be just as pretty as I am----
                              Brian Rupnow
                              Design engineer
                              Barrie, Ontario, Canada

                              Comment


                              • #60
                                Oh wow--Christmas just came at my house!!! The laps that I ordered the other day came in just now. No more screwing around with home made laps. This is very timely, because now I can finish lapping the Poppin cylinder before I make the graphite piston.
                                Brian Rupnow
                                Design engineer
                                Barrie, Ontario, Canada

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