Here is a video of the linear drive cube: https://youtu.be/R3sCj6oPCtw
Here is a video of the Linear Drive InMoov neck installed and testing: https://youtu.be/R95s6OxsMGg
I started with the original InMoov neck Gael Langevin www.Inmoov.fr designed which only had flexion/extension and left and right rotation. Then I changed over to Bob Houston's articulated neck here: https://www.thingiverse.com/thing:861146 After a series of mods and patches I changed over to Drupp's Parloma style neck here: https://www.thingiverse.com/thing:2059967 Still not satified with the movement control I decided to design a linear drive similar to that I created (https://www.thingiverse.com/thing:3743426) as a mod to Bob Houston's Articulating Stomach here: https://www.thingiverse.com/thing:1409964
The Drupp files are needed to make modifications to the InMoov torso so it can receive the linear drive cube. Drupp's Parloma Neck fits in this same space. HomPlateBackLeft and Right needed a wee bit of trimming after install to maintain the 80mm width of the rear entry.
Printing & Assembly Hints:
Imagine these parts in a stack:
Drupp_Neck_Hinge - the head mounts on this.
Neck_U_Joint_Base is secured in above with a 5/16" or 8mm bolt.
Neck_U_Joint_Coupling assembles to the Base
use the Neck_U_Joint_Star and print four Neck_U_Joint_Pins
Neck_Coupling - Print two and glue and press fit them together
Then glue that to the Neck_U_Joint_Coupling
Neck_Servo_Lid receives the entire neck & head assembly above. Glue it in place.
Route all the cranial wires down through the center holes & around the body of the star.
Now we'll start at the bottom and work our way back up to assemble the drive cube:
Print Neck_Servo_Base as the foundation.
Print Neck_Servo_Base_Insert - it contains 5 parts, a body, two spacer fins, and two risers.
The spacer fins press into place with their holed ends down. The fin with the little square hole presses onto the body with the little square tab. The left and right risers press and glue into place facing up. They will act as guides for the two Neck_Lead_Screw_Drives assembled later.
Print InMoov_GearPotentio - this contains both Pot gears - the original InMoov elbow gear scaled to 109.5% The gears will each snap into a Neck_Pot_Frame_Assy (print two)
Set aside the Pot retainer clips.
Print two Neck_Pot_Rack_Gears.
Now would be a good time to ready two MG996R or equiv. servos for continuous rotation (remove the pin) and external potentiometers. (remove the pots and solder extension leads on) I've used servo extension cables so the pots may be unplugged and reversed as needed.
Glue the Neck_Pot_Frame_Assy onto the Neck_Servo_Base (with pot retainer clips and rack gear temp. installed to get spacing right)
Print two Neck_Servo_Lead_Screw The file contains a top and bottom half that interlock (not yet). The side with the central column gets pressed onto a 100mm x M8 x 2mm Pitch Lead Screw. Make sure the central column is facing away from the lead screw. The side with the two little pins mounts to the servo disc with two very small self tapping screws. Now the two halves may be pressed together.
The Neck_Servo_Base_Insert may now be slid down into the Servo_Base over the two Lead Screws.
Print the Neck_Lead_Screw_Drives. Press an M8 Lead Screw nut into each, aligning the holes. Use four M3 x 10mm screws to secure each in place.
Thread each Neck_Lead_Screw_Drive onto its respective lead screw with the recessed holes on the side facing out. Those will secure the push rods to the Neck_U_Joint_Base, and the Neck_Pot_Rack_Gear. Spin the servos by hand to get the Neck_Lead_Screw_Drives all the way down.
I used a dental mirror to get eyes on the slot for the pot in each gear. I would rotate the gear as needed so when the rack gear is inserted into the pot frame all the way the slot would match the position of the pot turned all the way as if the gear had driven it there. Now the pots may be installed and their retainer clips slid into place.
Now the Neck_Pot_Rack_Gears may be secured to the Neck_Lead_Screw_Drives
Lastly, slip the Neck_Servo_Lid into place and secure with four M3 x 15mm machine screws.
It is possible to wait to glue the head assy into place so you may test and calibrate the cube first.
Once you have the cube tested and calibrated (I used an EZ-Robot ioTiny) then you can install the head to the cube, and the whole business into the Torso with two M3 x 15mm machine screws in front and two small self tapping screws to hold Neck_Cube_Rear_Lower_Clip in place which mounts on the lower back of the cube and holds it in place.
To provide some added stability and a wire guard mount Neck_Rear_Cover on the bottom back of the skull. Drill a 2-3mm hole at the bottom of Neck_Rear_Cover. Fasten two 6mm x 25mm springs - one under each of the screws that hold the rear of the lid on. Fasten the other end of the springs to the little hole drilled in the bottom of Neck_Rear_Cover
To connect the Neck_Lead_Screw_Drives to the Neck_U_Joint_Base I used M3 x 50mm threaded rods (https://www.amazon.com/gp/product/B01LWPOXJO/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1) attached to RC ball joints (https://www.amazon.com/gp/product/B07SSZ1T46/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1)