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A new attempt at making piston rings

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  • The rings have been sanded on both sides with 600 grit paper on a flat cast iron surface plate to 0.038" thick, and tried for fit into the grooves on the piston. This picture is the Trimble deburring fixture that "sorta kinda" works. Ring is placed on end of fixture in a "step" machined in the end of the fixture and then the cone is pulled in by the bolt to expand the fixture and hold the ring for deburring. I don't think I would dare to use a cutting tool on the ring because I'm sure it would fly off. However, it does seem to hold the ring secure enough that I can get in there with a piece of 240 grit emery paper and knock off any burrs, both on the o.d. and the i.d. of the exposed side of the ring.
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

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    • Out of 8 rings, 4 survived the polishing, deburring, and gapping. The four that didn't was because of a mistake on my part. I have a 1.006" hole thru that round piece of cast iron (same as the cylinder bore) and I used it as a guide for gapping the rings to a 0.004" end gap when squarely inserted into the hole. Surprisingly, Trimble doesn't cover this gapping procedure at all. He just says to run a piece of fine emery paper between the cleaved ends of the ring. The surviving four which are on the heat treat fixture will now go into my heat treat oven at 1100 degrees F for three hours.
      Brian Rupnow
      Design engineer
      Barrie, Ontario, Canada

      Comment


      • blimey, that's a process.

        As for the india stone, I'm not sure what grit it is, but the Arkansas stones I have are much finer than 220 grit. They don't remove much material, but they do produce a very clean scratch free finish.

        Comment


        • Yes Arks can be very fine indeed. How the surface of the stone is prepared makes a difference, as is likewise with India hones. Both are very hard (in terms of bond) so they don't let go of abrasive particles easily. That means they hold a shape pretty well, so whatever texture you put on the surface of the stone during flattening is going to be there for a while. If you make it very coarse the stone wil produce a coarser finish and cut faster. If you make it very smooth the stone will produce a finer finish and cut much slower. If you are going to be stoning precision surfaces, do yourself a favor and make certain the stone is flat. It's also a good idea to use a lubricant. Mineral spirits or kero work very well for extremely fine stones. You may want something a little thicker in viscosity for coarser stones.

          Comment


          • These are the rings about three hours after heat treat. Lots of black crud on both rings and fixture, but it seems to brush off very easily. Tomorrow I will take the heat treat fixture apart to free up the rings and clean them individually.
            Last edited by brian Rupnow; 07-03-2021, 07:58 PM.
            Brian Rupnow
            Design engineer
            Barrie, Ontario, Canada

            Comment


            • ekretz--the paperwork that came with this stone says to use water as a lubricant.---Brian
              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

              Comment


              • Originally posted by brian Rupnow View Post
                ekretz--the paperwork that came with this stone says to use water as a lubricant.---Brian
                You can use water if you like, but it won't work as well and the stone will dull much faster. That will be fine if you're looking for a polish, but not so good if you need to remove any material.

                Comment


                • Wow, just finished reading this thread from beginning to end. I have a few observations and perhaps suggestions to make, although I hesitate to do so because of some past criticism and the fact that I have no experience designing or machining miniature IC engines. But I will add my thoughts, and you may take or leave them as you wish - I have no "skin in the game". But I'd be happy to see success with this project.
                  1. The engines with CI rings all seem to have a lot more friction than the running models with Viton O-rings, so they need to be designed to deliver more power for the same RPMs.
                  2. There have been some previous unsuccessful attempts at making such engines provide considerable power to perform work, like the saw mill. Probably due to spark advance and carburation under low vacuum conditions.
                  3. Most of the effort has been to minimize leakage between the outer surface of the CI rings and the bore of the cylinder, but I think it is leaking around the ring and the face of the groove, which may not be smooth and flat enough.
                  4. There may need to be a little more chamfer on the rings to avoid the sharp edge scraping the cylinder walls, especially if the ring twists in its groove.
                  5. I haven't seen any details on the lubrication system for the piston in the cylinder - it's a lot more critical for metal rings as opposed to Viton O-rings.
                  I also think it would be helpful to make some of the pressure, force, and vacuum measurements as suggested by JT and others. Also actual figures for valve and ignition timing, which may need to be adjusted for CI rings and the increased friction.

                  That's all I have for now. I won't comment further unless invited to do so. Good luck!
                  http://pauleschoen.com/pix/PM08_P76_P54.png
                  Paul , P S Technology, Inc. and MrTibbs
                  USA Maryland 21030

                  Comment


                  • All of the black crud came off very easily with a brass bristled brush. The rings have "taken a set" at the required gap (0.150").
                    Brian Rupnow
                    Design engineer
                    Barrie, Ontario, Canada

                    Comment


                    • PstechPaul--the engines running cast iron rings have considerably less friction than those running Viton o-rings. The Viton rings must have a certain amount of "squeeze" to function properly and that provides more friction on the cylinder walls than a cast iron ring. The hit and miss engines that I have made running Viton rings have a much shorter "coast cycle" than the same engine running cast iron rings.
                      ----You may be right about the seeming lack of power from these small engines. Valve and ignition timing play a very big part in how these engines perform.
                      ----The face of the groove (I think you mean the gap) is filed with an ignition file to get the right ring gap when the ring is installed in the cylinder. This gap is 0.004" wide. There will always be some leak-down of compression at the ring gap, but not enough to keep an engine from running.
                      -----the rings do have a chamfer, but it is very small. I have never seen a case where the sharp edge of a ring has gouged into the cylinder, unless the engine failed from overheating or from too small a ring gap.
                      -----the lube system for the rings can be an oil cup attached to the cylinder, set so that it releases a drop of oil onto the moving piston periodically, or it can be a small amount of 2 cycle engine oil added to the fuel.
                      Brian Rupnow
                      Design engineer
                      Barrie, Ontario, Canada

                      Comment


                      • Rings are installed on piston (lots of 30 weight oil and very deft fingers). Piston is installed in cylinder, rod cap bolts are back on, and engine has excellent compression. I'm not going to try and start the engine tonight. I have trouble sleeping as it is, and if I start this engine tonight I will be too revved up to sleep. This is all looking very positive, and tomorrow morning we will see if the engine runs.---Brian
                        Brian Rupnow
                        Design engineer
                        Barrie, Ontario, Canada

                        Comment


                        • Originally posted by brian Rupnow View Post
                          Rings are installed on piston (lots of 30 weight oil and very deft fingers). Piston is installed in cylinder, rod cap bolts are back on, and engine has excellent compression. I'm not going to try and start the engine tonight. I have trouble sleeping as it is, and if I start this engine tonight I will be too revved up to sleep. This is all looking very positive, and tomorrow morning we will see if the engine runs.---Brian
                          Way to go Brian ! Excellent compression says the rings came out good. Better yet, the compression will probably improve even more after the rings seat !

                          With excellent compression there isn't much doubt the engine will run fine. Glad you hung in there on this one.

                          Comment


                          • Yay Brian! I've been reading the entire thread, trying to learn.
                            What was the black crud on the rings, out of the oven? Any idea?

                            I wouldn't be able to sleep, your wife must be a saint.
                            Last edited by nickel-city-fab; 07-03-2021, 10:41 PM.
                            25 miles north of Buffalo NY, USA

                            Comment


                            • Originally posted by Sparky_NY View Post

                              Way to go Brian ! Excellent compression says the rings came out good. Better yet, the compression will probably improve even more after the rings seat !

                              With excellent compression there isn't much doubt the engine will run fine. Glad you hung in there on this one.
                              What Sparky said!!!

                              At this point I don't know if it would harder to sleep not knowing or have it running tonight and still be all revved up about all night. LOL

                              Looking very promising Brian!
                              Home, down in the valley behind the Red Angus
                              Bad Decisions Make Good Stories​

                              Location: British Columbia

                              Comment


                              • Good compression says the rings came out right. Bodes well for the test run, but I think everyone, (nobody more so that you) has learned not to expect too much until it is proven......

                                Good work!

                                I think there will be more questions, but those can wait for after the test run.
                                2730

                                Keep eye on ball.
                                Hashim Khan

                                Everything not impossible is compulsory

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