Variable crank, two circular plates revolving on the same center
Variable crank, two circular plates revolving on the same center. In one a spiral groove is cut; in the other a series of slots radiating from the center. On turning one of these plates around its center, the bolt shown near the bottom of the figure, and which passes through the spiral groove and radial slots, is caused to move toward or from the center of the plates.
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 plate cut with an Archimedean spiral groove (1 cm of radius a radian) turns at 4 rpm, the only driven joint. A bolt rides in the groove by real contact with its two walls, and is held also in a fixed plate with radial slots, so it can move only toward or from the centre. As the spiral plate turns the groove carries the bolt in or out: the crank-radius varies uniformly with the angle.
- Measured
- Bolt position against plate angle: slope 0.0100 m/rad (ideal 0.0100), r2 1.0000, over two windows; bolt travel 0.16..3.90 cm from the centre; max penetration 0.005 mm.
- Notes
- The radial slot is the slide joint (drawn, damping 1.0) set horizontal so gravity does not move the bolt; each groove wall is a 90-segment polygon strip.
Film (MP4) · GIF · Still (PNG) · Spec (YAML) · Model (MJCF)
