[pullquote]use the distance node to control align-to-spline positions as well as inputs from rotation[/pullquote]
Devin Sloan shares a pretty detailed look at rigging Xpresso driven pistons and sliding actuators in C4D. This covers a wide range of material, but it is mainly centered on using the distance node in C4D to control the positions of Align-toSpline as well as inputs from rotation values.
Devin also provides an overview and offers a look at the basics for null based rigging, in opposition to joint based rigging, showing how to set up the hierarchy for the rig and how to hook everything up with Xpresso. Devin has some pretty good tutorial that he shares from time to time on his site, so be sure to check out DSC4D.com here.
Thanks for sharing!