Spherical Parallel Mechanism Joint

Here is a Spherical Parallel Mechanism Joint. This is a work in progress. Mechanism uses three stepper motors.

Here is a short video is the joint working.
https://youtu.be/cFRcwntOpEg

Assembly:
The Image shows the assembly order of the mechanism pieces. Screw together the pieces as you go. The circles indicate when to add the 4.5mm balls.

Press fit bearings into arms. Bolt together mechanism arms, placing a spacer between the two bearings. Tighten nylon nuts so that the arms rotate freely but don't wobble.

Hardware:
15 Bearings 11/16"OD x 1/4"ID x 1/4"TH
Torx screw for Plastic M2.26 8L 0.91thread (McmasterCarr (99397A189))
4.5mm BB's (Actual dimension seems to be 4.38mm) QTY: A LOT
1/4" bolts 1" long QTY 6
1/4" nylon nuts QTY 6
1/4" rod 3.5" Long QTY 3
17 NEMA stepper motors QTY 3

Update:

Jan. 4, 2020 - Updated the arms to give a wider range of travel.

More information to follow.