17 Replies Latest reply on Jan 15, 2015 5:58 PM by Muge Sanli

    Bearing connector not transmitting forces

    Justin Strempke

      I have an assembly with multiple bearing connectors which do not seem to be transmitting a force, and acting more like bearing fixtures.  The setup had a part with bearing fixtures (to ground), then pivot links with bearing connectors to pins, and another parts on top (think motorcycle lift or similar).  When I apply a force on the top part, naturally equal reaction force should be seen in the bearing fixtures but I'm getting only a small fraction there (180 kips load, and only 1500# reaction!).  I've read in the KB that some bearing connector setups can give inaccurate results at this time, mainly the rigid stiffness is either too soft or hard so I've tried with rigid and flexible with high stiffnesses, as well as one end of the links as self-aligning but nothing pans out.

       

      Anyone have any insight or work-around?

       

      Thanks!

      Justin

        • Re: Bearing connector not transmitting forces
          Justin Strempke

          Quick update on this, only seems to happen when a bearing fixture is used in the same force path.  Not sure if it matters if it's in the same assembly or not, but certainly when I have a bearing fixture on a part, which is connected by a link with a bearing connector on each end to another part, it does not work.  If I replace the bearing fixtures with hinges or fixed BC's, it works, and if I suppress the bearing connectors and bond the link to the pins then the bearing fixtures report/work correctly.  I've tried all combinations of self-aligning, rigid, flexible, lock rotation, but those don't seems to have any affect.

            • Re: Bearing connector not transmitting forces
              Jared Conway

              can you post a picture of what you're working with?

               

              i can't invision what your assembly looks like.

               

              also i can't tell if you're running into problems with fixtures or connectors or which one you want and why you want them.

               

              it sounds like you have a half that has bearings both sides which is a good fit for bearing fixtures

              then you go to the next step and actually at those ends the bearings connect the shaft to 2 other components and therefore instead you need bearing connectors at those ends

               

              but when you get to that step, i don't know what you mean in your troubleshooting or where you're trying to read the forces from or how you're trying to measure them

               

              my suggestion would be to start simple

               

              shaft, fixed on both sides, read reaction at the fixed faces

              shaft, bearing fixtures on both sides....what is the bearing fixture definition, how are you applying the load, how are you dealing with the rotation inherent to this problem, where are you measuring the reaction force?

            • Re: Bearing connector not transmitting forces
              Justin Strempke

              I already tried a simplified version - see images below.  The first is with cylindrical or hinge fixtures at the holes in the base, and bearing connectors between the pin and upper/lower blocks (each with a modeled shaft/pin connecting the sides).  I have an upward 1000 lbf applied to the top faces of the upper part, and each pin shear as well as reaction forces read 1000 lbf total.

               

              The second picture is with bearing fixtures instead of hinge fixutres, and the bearing connectors mess up.  The second pin shear is almost non-existant, as is the bearing fixture reaction force. 

               

              Side note I have a pin in the upper part to prevent too much inward draw, and have ran it with and with out that with no concequence.  I also have roller BC on the faces perpendicular to the hole just for stability, and no-pen global.  Odd part is even with bonded global with both bearing fixture and connectors (the connectors should largely be bypasses due to the link/block face bonding) the same oddity occurs.

               

              With cylindrical/hinge fixture in base part:

              bearing2.JPG

               

               

              With bearing fixture in the base part:

               

              bearing1.JPG