Jul 042012
In this video, remade for 2.6 from an older one, we model a simple piston/actuator, then, using parenting and constraints, control the movement of it with a couple of empties.
Here you can find the original BlenderCookie tutorial for Blender 2.49, by Jonathan Williamson – : cgcookie.com/blender/2009/09/21/rigging-a-piston/