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JohnF1-Visitor
1-Visitor
September 5, 2016
Question

Multi bar Linkage

  • September 5, 2016
  • 3 replies
  • 2374 views

full_engine_ass plus link.jpgDoes anyone out there know how to create a bar linkage mechanism in CREO 3.0?  I have 4 levers each moving on a Pin connection, I need to connect them via  single bar so that when one lever moves all 4 move. 

      3 replies

      T
      tbrotherhood12-Amethyst
      12-Amethyst
      September 5, 2016

      John, as long as the dimensions all match you should be able to create pin joints and the thing will work.

      Model is attached and here are the steps.

      1. I created a long link and a short link.
      2. New assembly with a long link in default (fixed) location.
      3. Add short links with pin connections at one end in each of the four holes in the long link.
      4. Bring in a second long link with pin connection to the first short link.
      5. With the assembly dialog for the second long link still open, add coincident constraints to each of the other three short links.
      D
      dschenken1-Visitor
      1-Visitor
      September 5, 2016

      Tim's advice is very likely correct - I don't have Creo access to remodel it to check.

      Keep in mind that, attached to more than two levers, the bar is over constrained. In real parts this is offset by deflection of the connecting rod or clearance in the holes. In the model there may be problems with numerical accuracy from finite precision available in floating point calculations.

      J
      JohnF1-VisitorAuthor
      1-Visitor
      September 6, 2016

      Hi All

      Thank you all for your input especially with regard to accuracy of assembly.  It transpired that the cylinder assembly had a 0.15076 degree offset orientation which fouled the mechanism assembling correctly.  By changing a constraint on the cylinder assembly to remove the angle offset the mechanism slotted into place as predicted.  In a real mechanism that minute difference would have been compensated by tolerances in the mechanism.  In a parametric model everything has to line up precisely.  A good lesson learned.  Consider me well chastised for not checking accuracy.

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