Strain Wave Gear
Strain wave gear visualization - see the YouTube at 0.25 speed to understand it.
See another Hackaday Post on strain wave gears:
Download simple model:
- 2 concentric gears
- Outside gear has N teeth, say N=100
- Inside gear is smaller and offset from center. It has a slightly smaller number of teeth - say N-2
- Difference in teeth number creates geardown of 100/2 = 50