We use a lot of wire rope and one thing that has always given me fits is the mating of the sheaves. It's obviously simple to mate sheaves when the tread is on the same plane/axis. But, if you want to create an angle in the sheaves then it becomes a bit more complicated.

Please view the attached picture.

I need to create a mate where in if I move sheave 1 (in the direction of the arrows) then sheave 2 will will pivot on the big red dot (left of sheave two). The big red dot is the rope tread drop. The red line(s) represent the wire rope (hand drawn for illustration purposes). As sheave 1 is moved sheave 2 should angle to maintain the rope tread line.

Now, I can do this with my mouse. If select sheave 2 it will rotate (as shown by the arrows) on the reference axis I created for the rope drop. I can also move sheave 1 with no problem. However, I can't seem to create a mate that will permit me to move sheave 1 and have sheave 2 maintain the rope tread.

The goal
What I am trying to determine is the proper angle to install sheave 2 based on the position I place sheave 1.

All sheaves have planes and axises representing the rope tread. What I think I need is a circular axis that represents the rope tread around the sheave and create a tangent mate between a plane/axis from sheave 2 to sheave 1.

Any help would be appreciated.