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Enlarging a Neoprene Hole

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  • #16
    The hole is too small for the rod and the problem is compounded by the tight fit in the bore which further decreases the size of the hole. .029" interference is too much for a standard lip seal at that diameter too.
    Southwest Utah

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    • #17
      Originally posted by mikey553 View Post

      Actually he said: "seemed to work at first but two days later I had to pound it out with a hammer". It seems like a good test to me. Let's wait for the OP to respond.
      I read that to mean that he poked the pushrod through the rubber and left it at that, but you may be right.

      Never hurts to ask these things...

      I've never worked on a 45, but it seems at least similar to my Pan...

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      • #18
        Too much interference..... I agree. Plus, the thickness of the piece of "neoprene" is probably significant, likely about the same as the hole size. It's likely it wiped all the oil off with that tight a fit, and then if it did swell, it might be worse.

        Although, when rubber type materials swell, they often get quite a bit more flexible, sometimes almost liquid, and in some cases turn into a gooey mess. So the net result might not be as bad as is described, and the problem may not be swelling, or not just swelling.

        That said, neoprene is not recommended for gasoline, greases, and many oils, per the McMaster-Carr site. It does not give reasons.

        The materials listed as best for oils etc are Viton and Buna-N rubber.
        CNC machines only go through the motions

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        • #19
          Originally posted by chipmaker4130 View Post
          The hole is too small for the rod and the problem is compounded by the tight fit in the bore which further decreases the size of the hole. .029" interference is too much for a standard lip seal at that diameter too.
          This.

          Also use Buna N instead of neoprene.
          12" x 35" Logan 2557V lathe
          Index "Super 55" mill
          18" Vectrax vertical bandsaw
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          24" State disc sander

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          • #20
            Originally posted by J Tiers View Post

            That said, neoprene is not recommended for gasoline, greases, and many oils, per the McMaster-Carr site. It does not give reasons.

            The materials listed as best for oils etc are Viton and Buna-N rubber.
            I am glad McMaster came to this conclusion about Neoprene rubber. But I would never rely on such opinion alone. My recommendation of Viton and Buna-N came from years working with different rubber compounds and oils (not necessarily just mineral) and performing professional compatibility studies.

            The problem with rubber and oil combination is they are never 100% compatible. You just select a pair that produces less damage than other choices.

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            • #21
              Originally posted by mikey553 View Post

              I am glad McMaster came to this conclusion about Neoprene rubber. But I would never rely on such opinion alone. My recommendation of Viton and Buna-N came from years working with different rubber compounds and oils (not necessarily just mineral) and performing professional compatibility studies.

              ..........................
              Interestingly, some manufacturer sources suggested "neoprene" was very compatible with oils etc, suggesting no issues from the combination. But "neoprene" is not one material, there are apparently many varieties, with different properties.

              While yes, I realize Mcmaster's listing is not an authoritative source, it is certainly an indication, and one that is quickly findable. Other sources strongly disagree. I found the following, and other similar information in a short search looking for industrial sources (not peripheral sources such as wetsuit companies, etc, of which there are dozens):

              The Timco rubber site has this to say about Neoprene: "Neoprene’s properties, such as high resistance to oil, flames, and even damage caused by oxygen and ozone, make it the perfect material for a range of heavy-duty applications."

              The Process industry Forum site suggests: "Neoprene is also popular due to its strong all-round chemical resistance as it remains unaffected by a range of chemicals including solvents, oils, and petroleum-based fuels"

              So according to these and other sources, the possibility of swelling etc seems not to not be an issue.

              What did the OP find after he extracted the seal from it's location? Did he find swelling, or adhesion of the neoprene to the rod?

              Most importantly, does the seal or the rod turn when the engine is running?

              The simplest explanation seems to be that the hole is too small. Most shaft seals I have dealt with are not that tight, and have relatively short contact areas. If the rod or the seal turn relative to each other, the tightness and possibility that oil may be excluded might cause a problem.
              Last edited by J Tiers; 04-28-2022, 08:11 AM.
              CNC machines only go through the motions

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              • #22
                Originally posted by mikey553 View Post
                From what you have described it sure looks like a rubber swelling issue. It was OK at the beginning, but 2 days later the seal was too tight. It is a classic swelling symptom.

                Now may we assume that 50W motor oil is a mineral oil? Also how sure you are the seal is made out of Neoprene? There are many Neoprene compounds in use today and in general they are not the best to work with mineral oil. If I could, I would select Viton or Buna-N. Both of them have good resistance to mineral oil, but Viton can tolerate higher service temperatures.

                I doubt you can enlarge the hole in the original seal, but maybe you can make a new seal from the sheet of the correct rubber material. You can make a steel tube of let's say .250" diameter, bore the inside taper to a sharp edge and use it to drill a hole in rubber. You may have to play with tube diameters to get the right fit to your actuator rod. Use mineral oil or water as a coolant.
                I'm not sure of the following:
                Composition of 50W Harley Davidson oil
                Composition of the seal
                Intended OD of the rod
                Intended OD or ID of the seal
                Intended ID of the bore the seal is in
                Amount of force required to move considered to be too much

                My first effort will be replacement. There are a lot of NOS and reproduction seal kits available.

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                • #23
                  Originally posted by Jim Stewart View Post
                  Any reason you can't replace it with a standard lip seal?

                  -js
                  A standard lip seal that would have all the correct dimensions to fit with everything else?

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                  • #24
                    When some web site says "high resistance to oil", it looses my respect. While there are different Neoprene compounds in use today, there are different oils as well. In addition to mineral oils there are POE, PAO, PAG oils just to name a few. They are widely used synthetic oils and they react with rubber in a different way than mineral oils. For example Buna-N seals work OK with mineral oil, but POE oil requires Neoprene or HNBR compounds. The direct application - automotive air-conditioning systems, requiring Buna-N seals for R-12 refrigerant with mineral oil and HNBR seals for R-134a refrigerant with POE oil.

                    Rubber swelling was just my guess. I could be wrong, but the description from OP points to it. Let's wait to what he has to say about it.

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                    • #25
                      Originally posted by andywander View Post
                      The forces acting on the pushrod during use will be pretty large-are you sure that it will stick when the clutch springs and pedal are hooked up?

                      I don't know that for sure, but I'm not comfortable installing it the way it is.

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                      • #26
                        Originally posted by mikey553 View Post
                        ............................

                        Rubber swelling was just my guess. I could be wrong, but the description from OP points to it. Let's wait to what he has to say about it.
                        Yes, it would be nice to find out what the seal looks like now, compared to when it was put in.

                        The seal was a "new component" (so was the rod), so presumably it is an OEM part, or an "aftermarket" part. There must be some history about it, from various M/C forums, possibly "reviews" of the product itself (I tend to disbelieve all reviews, they are totally uncontrolled).

                        If this is a common problem, then it will show up somewhere.
                        CNC machines only go through the motions

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                        • #27
                          Originally posted by mikey553 View Post

                          Actually he said: "seemed to work at first but two days later I had to pound it out with a hammer". It seems like a good test to me. Let's wait for the OP to respond.
                          I can't put a force quantity on this test ,but last time I replaced this there was about as much drag as would be expected for the intended purpose, easily moved in either direction with one hand, but a noticeable resistance.

                          This one I can't budge at all pulling with one hand and pushing against the case with the other. I'm not installing it that way.
                          Last edited by Spindle; 04-28-2022, 09:59 AM.

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                          • #28
                            Originally posted by chipmaker4130 View Post
                            The hole is too small for the rod and the problem is compounded by the tight fit in the bore which further decreases the size of the hole. .029" interference is too much for a standard lip seal at that diameter too.
                            What would be a reasonable interference fit for just a disc seal?

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                            • #29
                              Originally posted by andywander View Post

                              I read that to mean that he poked the pushrod through the rubber and left it at that, but you may be right.

                              Never hurts to ask these things...

                              I've never worked on a 45, but it seems at least similar to my Pan...
                              I polished the annular grinding marks out, lubed with oil, then tested by moving it in and out for several minutes.

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                              • #30
                                Originally posted by Spindle View Post

                                I can't put a force quantity on this test ,but last time I replaced this there was "about as much drag as would be expected" for the intended purpose, easily moved in either direction with one hand, but a noticeable resistance.

                                This one I can't budge at all pulling with one hand and pushing against the case with the other. I'm not installing it that way.
                                You are not telling the whole story. Was this seal exposed to oil for 2 days? Have you removed it, checked for dimensions and compared them with new seal measurements?

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