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# Frictionless Axis of rotation

## Frictionless Axis of rotation

(OP)
I want to analyse the force required to compress a spring, the lever has a 'frictionless' pin at the bottom, to rotate around and the spring at the top.

When I analyse the lever bends around the axis(assumes 100% friction) - how can I get it to rotate around the pin freely?

thanks

### RE: Frictionless Axis of rotation

Assuming you are using solid elements (blue) to mesh the model as opposed to shell elements, create a rotational constraint by first creating a cylindrical coordinate system in mechanical located at the axis of your pin hole.

Next, create a constraint, but change the coordinate system reference to the newly created cylindrical csys.  You should now have new constraint options r, theta, and z.  My guess is that you would pin r and z and free theta.

Good luck,

Steve

### RE: Frictionless Axis of rotation

(OP)
cool - worked straight off....spent a whole day yesterday trying and knew I was missing a trick....thanks.

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