Linkage & Mechanism Simulator
A planar mechanism workbench. Place ground pivots and pin joints, connect them with rigid links, add a slider on a straight guide and make one link the motor-driven crank, then press play and the solver moves every joint to keep the links rigid. Mark any joint to trace its path and watch coupler curves, straight-line motions and walking gaits appear. Presets load the classics: four-bar crank-rocker and double-crank, the piston crank-slider, Watt’s and Chebyshev’s straight-line linkages, the Peaucellier–Lipkin inversor, a pantograph and Theo Jansen’s Strandbeest leg. A Grashof check, the transmission angle and an input-output plot show why some designs turn all the way round and others lock up. Edit link lengths directly and export the mechanism and its traces as SVG.
Runs 100% in your browser — simulations are computed locally on your device.
Notes
- Each frame the solver turns the crank by a small step and runs Newton iterations on the link-length constraints, starting from the previous pose so the mechanism stays on the same assembly branch.
- Grashof’s rule decides whether a four-bar can rotate fully: with s and l the shortest and longest links and p, q the others, some link turns all the way round only if s + l ≤ p + q.
- The transmission angle between coupler and output link measures how well force gets through; designers keep it above about 40°, because near 0° the mechanism jams.
- Runs 100% in your browser — simulations are computed locally on your device.
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