1 Reply Latest reply on Sep 16, 2007 1:04 PM by Ian Hogg

    How do you specify torsion springs

    Jamie Myrhum

      I have a linkage assembly that I'm running a motion analysis on. I'm trying to specify a trosin spring in the assembly to activate the linkages. The confusing part is that it doesn't clearly specify where the pre-load is set & the direction the spring is activating. The options are there, but it does not make clear how the spring will function in the assembly. Can any one explain this to me better as the help file for this features is clearly lacking.

      I'm also still trying to figure out why is askes for both a pre-load angle and a starting toque, as the angle and spring factor will give you the pre-load

      Thanks,

      Jamie
        • How do you specify torsion springs
          Ian Hogg
          Hi Jamie,
          The main aspect of torsion springs to be aware of is the signconvention. It is best to use a face to define the direction as thenormal vector of the face will determine your positive directionbased on the right hand rule. You have the option of specifying thespring in either a free condition or a preloaded condition. If youspecify an angle value and the torque as zero, you are stating thatrelative to the current position, this this is the relaxed position(free angle) of the spring. If you set the angle as zero andspecify a torque value, you are stating that the torsion spring haspreload at the current position.
          This is identical to the linear spring behavior. So the sameaspects apply there also.

          COSMOSMotion always assumes the model is in an assembled state.Hence typically a spring will be in an installed position (therewill be preload) at the start of the simulation.

          With respect to sign convention, remember that the sign of theangle or torque values is important as well as the first component,second component. Let's normal vector of spring is in the directionof your thumb. A positive angular position for part1 with respectto part2 will be a counter-clockwise rotation. The same applies forthe positive torque direction acting on part1. The oppositeconvention exits for part2. It can sometimes be a little trickywith action reaction forces/torques to think about this, so makesimple model if you want and test the behavior of the spring todifferent inputs.

          I hope this helps clarify the spring settings for you.
          Cheers,
          Ian