Thanks to Manu Järvinen for sharing his original concept you can find here https://www.blendswap.com/blend/1629
It inspired me to make this kind of rig tutorial "How to rig pistons in Inverse Kinematic ?" I hope it help you in your animations!
If you download this model feel free to use it in your artwork, modifie it, play with it, share it!
Thanks for downloading!
This is one nice piece of mech art!