Multiple joints in a circle won't collapse

[markrdrew]

I'm guessing there's something missing here or I've just got something not quite right. I'm trying to get this octagonal ring to collapse inward by folding the arms downward in the middle. All joints were flexing until I built the last revolute. I added sliders to the 8 corners thinking they were needed to move those parts towards the center. Nothing. I changed the grounded component from the first (first designed) corner, to the hub in the center but that likely doesn't do anything because it's not connected? Still nothing.

What am I missing? Or is this just not possible?

Thanks in advance.

Mark

[davebYYPCU · Accepted solution]

Or is this just not possible?

In current construction, yes, it is not possible.

As the grey component slides towards the camera, the red and bone arms should drop and fold together.

The red and bone arms are hinged on the centre line to the grey component.  The hinge pin for the two arms is not on the same alignment.  This pin when lowered (along the yellow arcs, exaggerated) to pass horizontally past the hinge at it's other end, are pushing the grey components off their intended move axis.

Might help....

[markrdrew]

Ahhh that joint is over-centered so it locks up. Tomorrow I'll try re-positioning the arms so the hinge point is below the horizontal level of the corner pins. Makes total sense. It won't look right at rest but I can have a separate drawing for that if I need it.

Thanks for the hint.

Cheers