Another more simple example, I'll upload the file, so you can see it on your own.

Basically it's 2 chains that are connected at the white and the black objects.
I'll name the objects with their colors, because I think it makes it easier to understand:

Orange = rotating disk with spin modifier
White = parented to orange

Green-Blue-Black = IK-chain
Green = Slider, free in the z-axis, locked in x and y-axis
Blue = parented to Green, Ball joint with only 1 free axis (y)
Black = parented to blue, tracking white - full constraint (it's just there to follow white)

Here is the file:
www.evajoe.homepage.t-online.de/mechanics2.rar

Edit: typo