Built in Autodesk Fusion

Sketch geometry, ready to cut.

These came out of the script pack as closed splines in a Fusion sketch — the same curves, but sitting in the model where a toolpath can reach them.

Spiral track, eight pens — Spiral track, eight pensPathTrochoid · DP 15 · 275T track · 12T planet

Popsicle-stick track — Popsicle-stick trackPathTrochoid · DP 10 · 138T track · 12T planet

Sun and planet, cut — Sun and planet, cutEpiHypoTrochoid · 24T and 12T · DP 10

Racetrack gear set — Racetrack gear setStadiumTrochoid · 48T track · 12T planet

Gear profiles for print — Gear profiles for print20° pressure angle · 0.04 backlash · 0.30 fillet

Internal ring study — Internal ring studyEpiHypoTrochoid · internal mesh · 9T planet

Put it in your model.

Four scripts that build the curves, fit the teeth, and hand you geometry you can extrude or machine.