Shears for cutting iron plates, etc
Shears for cutting iron plates, etc. The jaws are opened by the weight of the long arm of the upper one, and closed by the rotation of the cam.
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
- The upper jaw is a lever pivoted on a post: a long arm of 21 cm reaches left over a round disc cam (3.5 cm radius, on a shaft 1.35 cm off its centre), and a short jaw reaches right over the fixed lower jaw. The cam is the only driven joint (12 rpm). The long arm rests on the cam by its own weight, with a stop under its tip to hold the jaws open. gen130.py.
- Measured
- Closing: the jaw turns 0.0777 rad per radian of cam over the lift (expected 0.0776, r2 0.9999); opening again under the arm weight: -0.0889 (r2 0.9986). Jaw swing 0.173 rad (9.9 degrees) per turn, as eccentricity 2e = 2.7 cm over 16 cm arm gives (0.169). Penetration 0.00 mm after the first second.
- Notes
- The cam lifts the long arm and the jaws close; the weight of the arm opens them again as the cam comes round.
Film (MP4) · GIF · Still (PNG) · Spec (YAML) · Model (MJCF)
