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A new engine for fall---

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  • Yep - dead ringer!
    Kansas City area

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    • I'm very pleased to announce that with rod and piston installed and all gaskets in place, the crankshaft does indeed go "round and round". No matter how much fancy 3D cad modelling I do and how many calculations I make, this is always the moment of truth for me. I actually had one little heart stopper---the crankshaft wouldn't make a full 360 degree rotation when I first assembled everything. I took out the bolts that hold the cylinder to the crankcase one by one, but it wasn't that. Then I pulled the head off----and discovered that the top of the piston actually comes up about .013" higher than the top of the deck. That would have been okay, I have .060" clearance milled into the head.---But--I had cut the gasket hole a bit small, and the piston was hanging up on the gasket material. A bit of very careful exacto knife work to trim the gasket, and that fixed things. A big sigh of relief----Brian
      Brian Rupnow
      Design engineer
      Barrie, Ontario, Canada

      Comment


      • Jeez, we're really coming down to the wire here folks.The two knurled items in this post will be what allows me to grip the ends of the camshafts and rotate them by hand after loosening of the set-screws in the timing gears to adjust the cam timing. They also limit the axial movement of the camshafts in their bushings. They will be bolted and Loctited to the ends of the camshafts.
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

        Comment


        • These are the parts I've been saving until last, for two reasons. First reason is that 95% of the engine has to be built before their is a place for them to go, and the second reason (the real reason) is that I'm not sure how I am going to make them. The method outlined by Malcolm Stride in his Bobcat/jaguar/Lynx series works very well, but involves an awful lot of mill cranking. The second method which I believe Chuck Fellows made a video of and involves doing them in a rotary table on the mil looks a lot simpler, but I'm not certain about being able to hold the accuracy with the Chuck Fellows method.
          Brian Rupnow
          Design engineer
          Barrie, Ontario, Canada

          Comment


          • So--What did I do wrong? I just used the cam-calc program http://modelenginenews.org/design/CamTable.html to create this cam profile. My inputs were --cam angle=120 degrees--valve lift 0.080"--flank radius =.640" --base radius =0.240" --engine rpm 3000, and 2 degree angular increments. It created a profile that dishes in rather than out like it is supposed to be. I am not sure I have laid it out correctly but I think I have.
            Brian Rupnow
            Design engineer
            Barrie, Ontario, Canada

            Comment


            • And just for interests sake, that generates a nose radius of a whopping great .1815" . I'm sure I must be doing something wrong. Maybe the calculator doesn't like such a slow engine speed. The only really major difference between the inputs for this cam and the one Malcolm Stride generated for his Bobcat and Jaguar engines was that he used an engine speed of 5000 rpm for his inputs, and his cam profile turned out like one would expect a cam to look like.
              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

              Comment


              • I must be doing something wrong in my layout. I just reran the cam-calc program using a 5000 rpm input and it spit out exactly the same numbers as for a 3000 rpm input. The output for both 3000 rpm and 5000 rpm inputs is also telling me that the nose radius will be .080" which I expected it to be. I'm doing something wrong in my layout. I just have to figure out what it is.
                Brian Rupnow
                Design engineer
                Barrie, Ontario, Canada

                Comment


                • Okay--I'm sorted out. I have figured out that my layout was incorrect. I am currently working on a 3D cad model which will give me the proper profile when finished, but it's not quick nor easy. I have to create a solid, then rotate it and machine away portions of it exactly as I would in the machining process. I will post the profile when I get it finished.---Brian
                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

                  Comment


                  • This was a battle royal, but I got it sussed out. The end result is happy!!! The cam profile generated by using all of the inputs for machining from CamCalc is a VERY VERY close match to what I had originally designed. I feel confident that if I use the generated numbers when actually machining my cams, I will end up with the result I was after.
                    Brian Rupnow
                    Design engineer
                    Barrie, Ontario, Canada

                    Comment


                    • Yowzahhhhhhhhhhhhhh!!
                      Brian Rupnow
                      Design engineer
                      Barrie, Ontario, Canada

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                      • Looks like a par of earrings, are you getting in the jewelry Brian?
                        Andy

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                        • Would you like me to CNC those for you Brian?
                          Kansas City area

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                          • Toolguy--That is a very kind offer, but I will try them at home first. I made a previous set of cams using this method when I built the Canadian Cub engine, and it worked out fine. If I get into trouble, I will come screaming for help.---Brian
                            Brian Rupnow
                            Design engineer
                            Barrie, Ontario, Canada

                            Comment


                            • It is little right?

                              Print an output of the profile. Cut the round non-lift portion with your rotab. Profile the lift portion with a file.

                              Cheers,
                              Norman

                              Comment


                              • I could do that Norman, but its a lot of filing and I wouldn't learn anything new.
                                Brian Rupnow
                                Design engineer
                                Barrie, Ontario, Canada

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