Elliptical spur-gears
Elliptical spur-gears. These are used where a rotary motion of varying speed is required, and the variation of speed is determined by the relation between the lengths of the major and minor axes of the ellipses.
Only the input is driven; every other part of this model moves by physics (MuJoCo), and its ratios are measured. Run it live, change its parameters, or switch the friction off to see the output stop.
- Modelled as
- two equal elliptical gears (a 10, b 8.66, e 0.5) each turning on a focus, shafts 2a = 20 apart, 24 straight-flanked teeth at equal arc pitch as part pieces
- Measured
- mean ω_b/ω_a = -1.010 (equal teeth: -1), slice means swing -2.91..-0.30 (focal-radius extremes -3..-1/3)
- Notes
- Only the left gear is motor-driven (20 rpm). Negative control: teeth out of contact → the right gear only swings down to hang on its focus (qpos 1.59 rad, no turning) against -17.9 rad driven.
Film (MP4) · GIF · Still (PNG) · Spec (YAML) · Model (MJCF)
