This is a simple servo controlled animatronic eyeball that uses 2 servos. The eye can look left and right and the top eyelid can open and close. you can drive 2 eyeballs with a servo Y cable. The servo control arm for the eyeball can slide onto the main shaft or plugged into the back of the eyeball itself as shown in the snapshots.
The included separate servo mounting bracket is designed to work with micro servos..
I use these, they are cheap and reliable - http://www.hobbyking.com/hobbyking/store/__9549__Turnigy_TG9e_9g_1_5kg_0_10sec_Eco_Micro_Servo.html
Use a Y cable to drive two eyeballs - http://www.amazon.com/gp/product/B007XP0NXE/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1
Print the parts -
eyeball_42_slot.stl, this version has a slot if you prefer to plug the servo control arm directly into the eyeball instead of the shaft. Print this with a high amount of infill and support turned on. I print mine at .1 layer height, 30% infill, 2 shells, support enabled. You need a high amount of infill so you don't get holes in the top at the end of the print when it closes the sphere up.
servoBracket.stl - this is a separate bracket that can mount to the base of the eye mech if you want to have the servos mounted close to the mech. Itherwise you can mount the servos wherever you want separate front he eye mech and use longer pushrods. I used shoe goo to fasten the bracket to the mech base.
servoclip.stl - this snaps over the top of the servo to hold the servo onto the bracket.
servocontrolarm_42.stl - print two of these to control the eyeball and the eyelid. you can use a paperclip for the pushrods.
lowerEyelid_42mm.stl - This is a fixed lower eyelid that snaps onto the base.
eyelid_42mm.stl - the upper eyelid, snaps to the base and then glue a servo control arm to the side.
shaft_42mm.stl - the shaft mounts to the base and then glue the printed washer to secure the shaft in place.
base_42mm.stl - the main base that the eyeball and eyelids mount onto.