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A new attempt at making piston rings

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  • Jerry---I've answered your posts a couple of times and called you Mike.--Sorry about that. senility setting in--Brian
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

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    • Originally posted by J Tiers View Post
      That accounts for the insistence on clamping the rings flat in the heating fixture. If not flat, they won't seal well against the groove.
      I would think that surface grinding them flat after heat treating would be the way to go. I seem to recall that the Chevy 350 only had around 4 or 5 pounds of ring pressure against the cylinder walls due to "spring" from the rings -- the rest of the sealing pressure came from the gasses themselves. Which means that the ring grooves need to be extremely parallel and straight and flat, etc.

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      • someone above mentioned a fixture for lapping rings to get the ODs perfectly round. Given all your experience with lapping pistons in, trying that might be worth a shot.

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        • Brian, I have no experience with model engines or making rings, but have been around the hot rodding world for a long time, as have you. One trick the rodders use is to drill gas passages into the top of the piston that intersect with the bottom of the ring groove. This lets the combustion gas pressure get behind the ring easier and force the ring into the cylinder wall. Just a suggestion, thinking outside the box.

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          • bluechips---Thank you. I too have spent a lifetime around hotrods, and I did know about that trick. It's pretty extreme stuff though.---Brian
            Brian Rupnow
            Design engineer
            Barrie, Ontario, Canada

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            • Hi Brian,
              A long while ago I made a 15cc petrol engine of my own design, which (by luck) worked very well. I recall making the piston rings by machining a tube of cast iron oversize enough. I then cut a slit about 1/8" wide the whole length of the tube. Then I put it in the 3 jaw chuck and tightened the jaws so that it closed the slit. With the gap closed by the chuck jaws I machined the rings to the desired size and parted them off. I think I lapped the rings down to the required thickness afterwards, They seemed to work well. You may have considered doing this already but I just thought I would mention it anyway. Good luck and keep up the good work.

              Alan

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              • Aren't we all happy we are not trying to seal a Wankel / rotary piston engine? Apex/ side etc.

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                • Any update?

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                  • Yes Ringo.--I have bought a toolpost Grinder for my lathe and I'm in the middle of buying a heat treat oven. As soon as I have both items I will carry on with my ring making exercise.---Brian
                    Brian Rupnow
                    Design engineer
                    Barrie, Ontario, Canada

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                    • Just another design suggestion that helps break in seating. Angle the face slightly to provide point contact with the bore.

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