rmx
Do you want to achieve a movement like the following animated GIF?:
This is what the rig looks like on Spine:
I added a child bone a bit away from the center of the Flywheel bone, made it the target bone of the Piston bone's transform constraint, and gave it only the Translate X mix. This makes the Piston bone to move horizontally as the Flywheel bone rotates.
Then create the Crank and Connecting Rod bones that connect the Flywheel and Piston bones, constrain them with a new IK constraint, and set the Piston bone as the IK target to make it look like the piston is being pushed by the crank. (In reality, the crank and connecting rod bones are just for show).
You can download the Spine project shown in the video here:
