Bill of Materials (BoM):
 

• 8x 5/16”-18 by 5” hex bolts
• 28x 5/16”-18 hex nuts
  • 4 go to the housing clamp screws
• 24x 5/16” washers
• 2x M8 cap screw
  • MP gear mounting
• 2x M8 nut
• 4x M6 nut
• 4x 6908Z bearing
  • main bearings
• 4x 608-2RS bearing
  • MP gear bearings
• 2x 6202-2RS bearing
  • internal worm bearings
• 4x 5/16”-8 by 3” button head screws
  • main housing clamp screws

Assembly Guide

You will need 2 of every printed part (with the exception of the drivetrain mounts, which you will need 4 of), plus the extra materials in the BoM above.

Creating half of the mechanism:

1. Insert 2 608 bearings into the monopole gear (with an optional bushing if needed). Insert the monopole gear into the semicircular housing, and secure it with an M8 cap screw and nut. If the bearings bind, you may need to add a small washer on either side of the monopole gear.
2. Fit the small pinion gear into the recess in the housing. Secure it with a 6mm M3 standoff screw and nut.
3. Press one of the 6202 bearings into the back of the internal worm gear. The bearing should be flush with the external surface of the gear.
4. Slide the worm gear over the pinion on the monopole housing until it contacts the shoulder on the housing. Secure it by screwing on the large driver gear with internal threads with the gear facing TOWARDS the worm gear.
5. Press two 6908 bearings into the circular drivetrain mounts.
6. Slide four of the 5/16"-18 x 5" hex bolts through the four hex slots in the CS gear housing. Add a washer to each bolt.
7. Slide a drivetrain mount with the recess facing TOWARDS the housing onto the 4 studs. Secure it with a washer and nut.
8. Push the monopole assembly into the bearing, followed by the second drivetrain mount with the recess facing AWAY from the housing. Secure with a washer and 2 nuts (hold the bottom nut steady with a second wrench to ensure the housing is square)

At this point, repeat all the steps above to create the second half.

Joining the halves:

1. Insert 4x of the smaller M8 cap screws into the halves, and secure with 4 additional nuts.
2. Before snugging down, insert the CS gear. You will need to align it along the poles:
   1. The central point of each monopole gear must line up with a pole on the CS gear.
   2. The easiest way to do this is to put the monopoles into the housing with the “point” of the gear facing upward.
   3. Next insert the CS gear in the correct orientation, with its pole being the smallest in the ring of elongated teeth.
3. Snug down the remaining screws and drive it by selectively turning the gears on the sides of the housing.

If you have trouble, refer to the exploded diagrams above.

OTHER INFO
Original research paper:

https://ieeexplore.ieee.org/document/9415699

Writeup of the build:
Blog post