animating mechanical parts

i recently created a thread asking about animating an automotive suspension system, i realized now what i want to do is to anchor certain armatures to points in space or eachother.

How do u anchor the end of a bone to a point in space so that when the other end is moved that part rotates and doesnt move. Like when animating a 4 cycle engine i want it so that when i lower the armature linked to the connecting rod, the result is that the crankshaft will rotate.

Add an IK constraint to the bone. do that either to an empty or to a bone that is not the child of any other bone. Then the chain will move to match the empty or extra bone.

This is the same technique as when animating walking characters to avoid slipping of the feet.