I have a model of a machine that needs revolute and prismatic (or slider) joints. The revolute joints are each a pivot with one rotational axis. The prismatic joints are each a slider with one translational axis.

Modeling the revolute joints was easy. I constrained the location of one part to another and limited its rotation to the appropriate axis. This worked great.

Now I need to constrain parts so that they can only slide along a common axis (like the segments of an old radio antenna or the trolley of a tower crane). I've tried most of the constraints available, but I'm at a loss as to how I should model this.

It may matter that the prismatic joint goes in a closed loop (with the sliding parts already connected via revolute joints to a common parent). Closed-loop linkages are an issue in some modeling and animation environments, like Three.JS (at least as of a few years ago), so maybe it is an issue here too?

Thanks in advance for any tips you can spare!


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