I want to animate a crankshaft and found several tutorials for it which are quite good and nearly everything works so far. Only problem left are the cylinders of the pistons. I need to move them only along one axle; problem: At the "Limit Location" constraint of the bone, i am not able to use the axes I want. I need to use the normal axes like in this picture:
http://imageshack.us/photo/my-images/856/bildschirmfoto20120620u.png/
Becuase then i could simply set the constraint accordingly. But the only available axes are "World Space", "Local Space", "Local with parent" and "Pose Space".

The local axes of this bone are like the world axes (see picture).
http://imageshack.us/photo/my-images/812/bildschirmfoto20120620u.png/
Can i somehow rotate the axis or use the normal axes?
I don't have any idea how to solve this.

EDIT: I found quite a lote of tutorials and other instructions on how to do this and everytime i was able to make it work. Problem: The tutorials always make the piston only move exactly vertical, but due to the reason that i want to make an v8 engine, i need to animate the pistons in any direction. I just am not able to make the right boneconstraint or use other axis in the "Limit Location" constraint on the bone.
Any ideas on how to solve this?