Wanted to try to model a planetary gear that is modular, in the way that you can stack multiple together to achieve higher reduction ratios. A single gear has a reduction ratio of 1:5 between the sun gear and the carrier.

However, my printer died so I did not get to test it. So if someone loves to print stuff as much as I enjoy to model, let me know how the model works :)

Print and build instructions:
For each gearbox you need

• 1*N-1 Spacer (N=1, 0 spacers. N=2, 1 spacer, N=3, 2 spacers)
• 4*N-4 casing pin (N=1: 0 pins. N=2, 4 pins. N=3, 8 pins)
• 2 casing cover (2 regardless of N)
• 3*N planet gear center pin (N=1: 3 pins. N=2: 6 pins. N=3: 9 pins)
• 1 Sun gear center pin (1 pin regardless of N)
• 1*N carrier (N=1, 1 carrier. N=2, 2 carriers. N=3, 3 carriers)
• 1*N casing with ring gear (N=1: 1 casing. N=2, 2 casings. N=3, 3 casings)
• 1*N sun gear (N=1, 1 gear. N=2, 2 gears. N=3, 3 gears)
• 3*N Planet gear (N=1, 3 gears. N=2, 6 gears. N=3, 9 gears)
  (where N is the number of modules you want to stack together).

No supports are needed. Casing covers, spacers and casing with ring gear are aligned with the casing pins and glued together. Sun gear center pin should be glued into the sun gear. Other than that the items are held together by other items.

Would really appreciate if anyone would try to print and see if it works :)