On rotating the disk carrying the crank-pin working in the slotted…
On rotating the disk carrying the crank-pin working in the slotted arm, reciprocating rectilinear motion is imparted to the rack at the bottom by the vibration of the toothed sector.
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 crank disc (18 cm above the arm pivot) carries a pin 9 cm off its centre. The pin runs in a long slot of a lever (the arm) that pivots below the disc. At its foot the arm carries a sector of 5 teeth each side (module 0.8, 18 teeth pitch circle, radius 7.2 cm), meshing a straight rack below. The disc is the only driven joint (12 rpm). gen131.py.
- Measured
- The arm swings 30.7 degrees (0.5365 rad; asin(9/18) = 0.5236 plus slot clearance) each side and the rack runs -0.0745 m per radian of arm (expected -0.072, r2 0.9996), stroke +-3.96 cm. Penetration 0.05 mm, 0.01 mm after the first second.
- Notes
- The pin slides along the slot as the arm swings, so the swing is limited to asin(crank radius over centre distance) and the rack goes to and fro by the sector tooth contact alone.
Film (MP4) · GIF · Still (PNG) · Spec (YAML) · Model (MJCF)
