WARNING: LOUD NOISES AT 53 SECONDS!
First off, I apologize for the sound at those 2 points. I think my wireless headphone drivers are causing my sound to break. I will fix it for next time.
This tutorial is LONG and it covers a lot of stuff. In this one we use the distance node to control align-to-spline positions as well as inputs from rotation. This tutorial also covers the basics of null based (as opposed to joint based) rigging, so it shows how to set up the hierarchy as well as how to hook it up with xpresso.
Here is Chris's Tutorial: http://greyscalegorilla.com/blog/tutorials/how-to-make-a-hydraulic-arm-in-cinema-4d-part-revisited/