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Rockerblock I.C.--Something a little different-

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  • #46
    The only real bad dancer I had was the first "Rupnow Engine" which was a horizontal hit and miss single with a set of flyball govenors. It had full diameter brass discs for crank throws, and they were heavy. Since I always bolt or clamp my engines down, I never realized how badly out of balance those full discs made it. A guy from Australia built it and posted a video of it "walking" across his fathers living room floor. He hadn't bolted the engine down when he started it, and they were all amazed to see an engine take off and try to walk back to Canada by itself.
    Brian Rupnow

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    • #47
      What good is a build thread without "in process" shots? This is my 50 tooth gear, emerging from another "chucking stub" left over from making a cast iron cylinder. It was barely, barely long enough. I hate doing really short stubs, because if you get to close to those hardened chuck jaws with the gear cutter you can kiss $80 goodbye. The 25 tooth gear which I will do next is on a comfortably longer piece of 1045 steel that was left over from a customer job.
      Brian Rupnow

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      • #48
        So--Today we made a start. I like cutting gears. I especially like making gears from left over bits and pieces that I have laying about. I always drill a pair of holes the calculated distance apart in a piece of scrap and fit the gears to shafts which set in the reamed holes. It is much better to do it this way and correct any "tightness" in the mesh, rather than trying to do it in a partially assembled engine. These gears seem to be "just right", although that is never a certain thing.
        Brian Rupnow

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        • #49
          Wow, before I have a chance to blink, you are at it again and have another engine designed with the build started.
          I really like the looks of this one. I have one question right now. Why are the points running on the crankshaft instead of possibly the off end of the camshaft?
          Larry - west coast of Canada

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          • #50
            The crankshaft is a much more convenient place for the points. True, you get a spark with every engine revolution, but so what? There is nothing in the cylinder to burn on the exhaust stroke, so it doesn't matter. This is known as a "waste spark" ignition. Almost all of my single cylinder engines are built that way.--Brian
            Brian Rupnow

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            • #51
              Originally posted by brian Rupnow View Post
              The crankshaft is a much more convenient place for the points. True, you get a spark with every engine revolution, but so what? There is nothing in the cylinder to burn on the exhaust stroke, so it doesn't matter. This is known as a "waste spark" ignition. Almost all of my single cylinder engines are built that way.--Brian
              Actually was common practice in automotive not too long ago, there's was a transitional stage between what's going on now (which is low voltage being ran all the way to the individual coils right at the plugs themselves) and when they first decided to do away with the distributor and just rely on crank and cam sensors,

              they did it by using two ignition coils for a 4 cylinder engine and creating spark twice as often as needed, each coil had two leads - for something like an in-line 4 cylinder #1 and #4 would spark at the same time, and #2 and #3 would do the same,
              one on the power stroke and one on the end of the exhaust,
              This system was simply done for one main reason, it was dirt cheap to build, but it did wear plugs at twice the rate,

              Still - better than the typical distributor system as you drastically cut down on moving parts that wore out and also had extra resistance in having to jump gaps other than the plugs themselves, also created a system that was superior around moisture.

              I know I sound like a luddite in many of things but not when it comes to engine controls - things just seem to keep getting better and better, got my start having to file, lube and adjust points and replace condensers and free up centrifugal mechanical weights and test vacuum advance diaphragms, all which created an archaic advance curve in comparison to today millisecond control monitoring...

              that being said - there is still a place for points to be used and Brian is doing that, I would think something would be missing if he used sensors and did it electronically - this is how stuff got done, watch them flutter - watch them arc, it's how people used to get around in the world...

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              • #52
                I think that to make the con rod a two piece like I'm thinking of, two separate pieces would have to be machined and bolted (and possibly dowelled) together as shown in the first picture. Then after they are firmly bolted and possibly dowelled together, the hole gets put in as shown in the second picture. The sides would have to be match marked to make sure they went back together the same way they came apart. Then they could be separated and put back together around the rod journal.

                Brian Rupnow

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                • #53
                  I just had a thought to throw in the mix. Could you mill a small keyway slot in each side of the con rod the mill the male equivalent in the removable end piece to keep the alignment perfect.
                  With it tight back against the little shoulder you have at the end of the rod and some well fitted bolts, it should not go anywhere.
                  Larry - west coast of Canada

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                  • #54
                    Bri is it the ease of assembly why your adding that type of rod "cap"

                    conventional caps use the tensile strength of the rod bolt and your using the shear strength,

                    your method also is leaving a hole in the rod width wise,

                    looked at your OP and it does seem your limited on space for assembly of a conventional style rod but also seems like you could just drill one hole in the lower "head mount plate" to gain access ?

                    just thinking out-loud here,

                    very nice job on the gears and like Cutting said you don't waste any time from design to build is a blink of an eye

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                    • #55
                      Here is a cross section thru the centerline of the engine. You can see how tight it gets between the rod cap and the underside of the water jacket. Of course, since it is a pressed together crankshaft, I could use a conventional closed rod end and assemble the rod when the crankshaft is pressed together. there's just something about doing that that makes me quiver all over----
                      Last edited by brian Rupnow; 04-09-2017, 01:16 PM.
                      Brian Rupnow

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                      • #56
                        Gotcha, You must just be trying to keep things compact then im guessing because your crank center-line is well above the lower rocker pivot, would gain you room and overall structure dimensions would remain the same,

                        would have to be an angle hole under the cam aligned with the rod to tighten cap - ?

                        Edit; overall dimensions would remain the same "except" for the flywheel - if engine base not mounted on a raised plate flywheel would drag on surface set on, is this the reason?

                        just curious questions as I do find it all very interesting
                        Last edited by A.K. Boomer; 04-09-2017, 01:34 PM.

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                        • #57
                          Nope, flywheels won't drag. Won't clear by very much, but won't drag either.
                          Brian Rupnow

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                          • #58
                            Right but they would if you lowered them (the crank) to gain clearance enough to run a standard rod,,, is that why your not wanting to lower the crank? smaller flywheels on these little engines have there own set of problems?

                            am just trying to figure out the reasoning

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                            • #59
                              Brian Rupnow

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                              • #60
                                The connecting rod could just be bored and assembled into the crank during assembly. This would assist with clearance.

                                Another option; press a sealed bearing into the connecting rod big end, then assemble that into the crankshaft assembly.

                                Norman

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