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Source for high temp retaining compound?

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  • #16
    Originally posted by QSIMDO View Post
    I have this book marked but haven't tried them yet;
    http://www.cotronics.com/vo/cotr/index.htm
    Thanks for the link, they have some things that look promising.

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    • #17
      Originally posted by redlee View Post
      Instead of a Brass sleeve could you Braze it then machine to spec. ?
      As of now, the design can’t be changed. I believe that the manufacturer is looking/working on making outer ring out of steel as well. That would at least open up the option of TIG welding the 2 together.

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      • #18
        I'm sure NASA has something, and it probably far exceeds 600 degrees.

        JL.........

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        • #19
          Permatex red high temp silicone can withstand 650 f
          Beaver County Alberta Canada

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          • #20
            I don't remember the name, but there is a substance which is used to seal the leadout wires in the manufacture of tubes. The name invar comes to mind, but I don't know if that is it. I'm guessing that you could perhaps plate one of the pieces with either this or something else, then re-press them together.
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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            • #21
              Excuse me for the criticism , but the factors you originally gave make it an impossible program to work
              First , let me say that my extensive experience in building Dies for plastic that had similar size components and operated in the 375 to 575 temperature range and used the same materials- Steel rings with brass outer rings all held to ..0005" tolerance
              Your problem says you need to reconsider either the materials or the design in my opinion .
              Second, thermal expansion alone says that the brass ring will grow .0108" MORE than the steel inner ring at the 600 degrees.
              No adhesive will withstand those forces and the temperature encountered that I am aware of .
              You said "Press fit" ..no good , It can only be a shrink fit and that must be at least a .011 shrink, which means that you'll have to heat the brass to do it during assembly.
              But it doesn't end there, you will have to know the Hoop Stress and tensile strength of your Brass/Bronze material to see if it will "stretch" ( ie fail) under load and that will resize it's diameter and that means it will pull away at operating temps
              Brazing/silver soldering offers some solution , but presents other
              Nothing is impossible ! Solutions just take longer
              Rich
              Last edited by Rich Carlstedt; 10-25-2020, 11:09 PM.
              Green Bay, WI

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              • #22
                I have to assume you are using this as a rotating seal assembly, where the brass ring is pressed onto the steel inner ring and that (Brass OD ) becomes the bearing surface.
                Reconsider instead to let the brass expand outward and lock on the steel piece on it's OD and then use the inner surface of the brass as a rotating seal against inner steel ring.
                Then you can control fits through sizes.
                When Brass cannot expand outward, it then closes it's ID
                When brass cannot expand in any direction thermally ( ie "Total restraint" ) it actually liquefies and seeks any crevice or opening ( and the Pressures are sizable !!!)
                Rich
                Green Bay, WI

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                • #23
                  It may be impossible, but can either the steel or the brass be slit to provide an allowance for the differential expansion? Several slits may be necessary to bring the amount of that differential down to manageable proportions. I am envisioning something like an ER collet with partial slits coming from both ends.
                  Paul A.
                  SE Texas

                  Make it fit.
                  You can't win and there IS a penalty for trying!

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                  • #24
                    I am wondering if these rings a considered a consumable. Are they expected to wear out and be replaced at predicted intervals. Because of the differences in thermal expansion it seems the two rings would “work” and eventually break down epoxy type adhesives. I think silver soldering would be a good solution and you would only need to solder along the ends/edges. You wouldn’t need full migration on the faying surfaces.... er the od of steel and id of the brass.

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                    • #25
                      Originally posted by J Tiers View Post

                      Well, when they had the program here to get old gas guzzling cars off the road, I understand they used that to jam the engines and make sure they were scrapped. If it doesn't stick well enough, I'd suppose some other thing would be used. It is also used for a sealant on wood stoves, which definitely get hotter than the OP wants, AND presumably sticks well enough to cast iron.

                      I'd think it works to a very high temp, since it is used to make sand mold cores even for iron casting.
                      so i tried it and it doesnt work. i "glued" two strips of clean sheet metal and let them bake overnight. the adhesion was very weak. it didnt try co2, as i doubt it would get to the joint. the exposed waterglass was brittle.

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                      • #26
                        Originally posted by Ironbearmarine View Post
                        I am wondering if these rings a considered a consumable. Are they expected to wear out and be replaced at predicted intervals. Because of the differences in thermal expansion it seems the two rings would “work” and eventually break down epoxy type adhesives. I think silver soldering would be a good solution and you would only need to solder along the ends/edges. You wouldn’t need full migration on the faying surfaces.... er the od of steel and id of the brass.
                        They are consumable but not for the reason you are thinking. There can also be no build up of material on the edges. Any silver solder or anything else needs to be in between the 2 sleeves.

                        When the 2 move it causes premature wear and makes additional handling to try and repair. There are around 40 of these in an assembly and they can’t really be swapped out individually. The $1500-1800 cost might be high but they were $1200 a piece a few years back and I think the cost has gone up.

                        They will eventually wear out, the “retaining compound” is to try and get some more use out of it before it does.

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                        • #27
                          Originally posted by Rich Carlstedt View Post
                          Excuse me for the criticism , but the factors you originally gave make it an impossible program to work
                          First , let me say that my extensive experience in building Dies for plastic that had similar size components and operated in the 375 to 575 temperature range and used the same materials- Steel rings with brass outer rings all held to ..0005" tolerance
                          Your problem says you need to reconsider either the materials or the design in my opinion .
                          Second, thermal expansion alone says that the brass ring will grow .0108" MORE than the steel inner ring at the 600 degrees.
                          No adhesive will withstand those forces and the temperature encountered that I am aware of .
                          You said "Press fit" ..no good , It can only be a shrink fit and that must be at least a .011 shrink, which means that you'll have to heat the brass to do it during assembly.
                          But it doesn't end there, you will have to know the Hoop Stress and tensile strength of your Brass/Bronze material to see if it will "stretch" ( ie fail) under load and that will resize it's diameter and that means it will pull away at operating temps
                          Brazing/silver soldering offers some solution , but presents other
                          Nothing is impossible ! Solutions just take longer
                          Rich
                          I am not doubting your thermal expansion numbers but there is not .100” clearance between the 2 rings while at temps. Inner sleeve is steel and outer is some sort of “brass”. Gold in color but I don’t know exactly what.

                          This is a rotating assembly but no bearing load on the outer sleeve, at least not how you are thinking.

                          Yes I said “press fit”, but they are probably shrunk on at assembly. We buy these from the manufacturer, I don’t know there exact procedure or tolerances.

                          Sorry for being cryptic on the details of this, I am not really allowed to give out a bunch of information on it.


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                          • #28
                            Originally posted by oxford View Post
                            I am not doubting your thermal expansion numbers but there is not .100” clearance between the 2 rings while at temps.......................
                            Yes I said “press fit”, but they are probably shrunk on at assembly. ........................
                            I don't think I said a hundred thousandths (.100") , I said eleven thousandths ( .011 ) if there was no shrink or press fits .
                            Some of the shrink will modify the .011 , but it greatly depends on the calculations I mentioned .
                            If it is not a bearing ( as you said) then I don't understand the "use and wear" comment ?
                            The other option is for sealing and then perhaps you should investigate thermo plastics for sealing, like PEEK ?

                            Rich
                            Green Bay, WI

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                            • #29
                              Loctite 2422 and 2620 are listed as being capable of resisting temperatures up to 650° F
                              Larry - west coast of Canada

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                              • #30
                                Originally posted by Rich Carlstedt View Post

                                I don't think I said a hundred thousandths (.100") , I said eleven thousandths ( .011 )

                                Rich
                                Sorry, I missed the zero. I see it now. I thought it seemed like a lot.

                                The brass rings are basically a carrier for something else, that is where the normal wear occurs. The brass slipping on the steel inner is just causing accelerated wear and service life of the whole assembly.


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