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O ring/piston fit

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O ring/piston fit

Home › Forums › Miscellaneous models › O ring/piston fit

Viewing 5 posts - 1 through 5 (of 5 total)
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  • 22 October 2018 at 09:45 #377045
    michael howarth 1
    Participant
      @michaelhowarth1

      I am refurbishing a twin cylinder marine engine with 5/8" pistons fitted with O rings. One of the pistons glides down the bore in an smooth and easy manner. The other piston requires more pressure to push it down. I assume that it is most desirable to have equal resistance in both cylinders for best performance. I thought that I might "measure" the force required to send the "easy" piston down the bore by applying weights. Then I could possibly adjust the O ring groove depth on the second piston until the same amount of weight sends it on its way.

      As a master of indecision, I then thought….."perhaps the "easy" piston is too easy and the stiffer piston is correct ?" In other words tighten up the "easy" piston ring.

      Just how much force is optimal. Any ideas please.

      Mick

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      22 October 2018 at 09:45 #4288
      michael howarth 1
      Participant
        @michaelhowarth1
        22 October 2018 at 17:57 #377097
        Neil Wyatt
        Moderator
          @neilwyatt

          Have you tried swapping them over?

          22 October 2018 at 19:37 #377120
          Boiler Bri
          Participant
            @boilerbri

            The pistons with no o rings on should move freely. As Little side play as you can get. Then with the orings fitted. Presuming there silicone should has a small amount of resistance. But not enough to have to force them. When the pressure comes on the pushing side by adding steam the o rings will seal more. Even running should ensue.

            If you look up EAP on the internet they have a chart that gives you the tolerance for the grooves for o rings

            Brian

            22 October 2018 at 20:22 #377130
            duncan webster 1
            Participant
              @duncanwebster1

              My current loco will use O ring piston seals, so I've been scouring the web for recommended fits. This looks interesting

              **LINK**

              it recommends a much lower squeeze than I would use for a static seal, basically 5% on diameter of ring squeeze, and width 30% more. This fits with what other people have told me, but real experience would be re-assuring. I'm hoping someone with real experience will respond

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