Leg Animation
Hiya,
ran in the same problem, but nobody here could help, so i did it on my own. Take a look at the animation if it is what you want.
Mechleg Animation
I am no more that often around SimplyMaya, but you can find me at: https://www.macs3d.com if u need more information how i did it 
cheers
mac
..the Force is with me (sometimes)