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Parametric Non-Circular Planetary Gear Generator

This internal project was inspired by this classic demonstration video:

These gear systems have unique motion properties and exhibit a mechanical analog of the "uncanny valley" with their cognitively dissonant motion and unique geometries.


"Carving" the involute sun-gear teeth along the pitch curve.

Gear System Program Inputs and Output

Design Inputs:

  • Arbitrary sun gear pitch curve, lobe and tooth count. (Sun gear is currently constrained to be radially symmetric with an integer lobe/tooth-count ratio)

  • Circular planet gear radius and tooth count.

  • Sun/Planet orbit ratio.

  • Gear tooth profile;  Involute, circular, arbitrary or null (pitch curve only)  

Design Output:

  • 2D gear profiles for sun, ring and planet gears in DXF-format.

Gear System Program Example Run

  • Sun gear form& tooth count: Rs = 4 + 4*cos(3*theta), 72-tooth.

  • Planet gear radius & tooth count: 1, 12-tooth.

  • Gear tooth profile:  Circular.


3:4:7 System: Combined DXF Profiles (left),  Pitch Curves Animation (right)

3:5:8 Gear System Prototype


Demonstration Model of 3:5:8 Involute System.  Laser cut in acrylic and MDF

Contact Access Systems & Circuits and learn how we can help.

Discussion of your goals and needs is complimentary.

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