See-saw, one of the simplest illustrations of a limited…
See-saw, one of the simplest illustrations of a limited oscillating or alternate circular motion.
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
- A plank 2.4 m long is balanced on a trestle 50 cm high, with a seat and handle near each end. The only input is the riders' feet: under each seat a pair of legs, sprung up out of the way, is pushed down by a foot pressing 80 N, the two feet in turn, a second each (never pulling). A foot can only lift its end when it reaches the ground, that is when its end is down. Two pads on the ground take the ends as they come down; the plank's pivot has a little damping.
- Measured
- The plank rocks to and fro 0.32 rad (18.5°) each way, with each end coming down on its pad in turn, in a steady swing of 2.000 s (the feet's own time), and the swing is as wide at the end of the run as at the start. Contact penetration stays under 1 mm.
- Notes
- Brown gives no sizes. The riders are left out but for their seats and feet, so that the plank's weight lies near the pivot.
Film (MP4) · Still (PNG) · Spec (YAML) · Model (MJCF)
