Hey, also wanted to jump in and show a setup using Control Rig in case others stumble across this post. I was able to replicate the setup we use in Maya for hydraulics. Mind you the hydraulic joints are one joint chain (pictures and video below)
This is the joint chain, with the following orientations
The control rig setup might look a little confusing, but hopefully, you should be able to make a similar setup for your character.
The rig hierarchy is as follows:
The controls and locators are created from the joints so that they have the same placement. Again, you might have to change the hierarchy to work with your setup.
I start by constraining the joints to these controls. The controls in this case are merely used as a buffer, but you could make the setup the other way around where the joints are parented to the controls. This is just what we needed for our use case.
Next up is the aim-constraint setup. You’ll have to play with the aim and up axis to work with your joints.
The last step is setting up the parent constraint between the different locators/nulls we use and the joints.
Mind you, there are different ways to make a setup for hydraulics, but this is the one we were able to whip up.