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Engineering lab · Interactive tool

Four-Bar Linkage Explorer.

Explore link proportions, open and crossed assembly branches, position closure, and output geometry for a planar four-bar mechanism.

Planar mechanism position closure

Live calculation

01Link lengths

02Assembly position

Length criterionGrashof
Live four-bar position solutionGround, input, coupler, and output links shown at the selected input angle and assembly branch.O₂AO₄BPOSITION CLOSURE: VALID
Vector-loop closurer₂ + r₃ = r₁ + r₄
Assembly statusClosedopen branch
Coupler angle24.27°global orientation
Output angle75.52°global orientation
Transmission angle51.25°coupler-to-output angle

Position closure is the first gate

The live diagram solves the intersection of the coupler and output-link circles at the selected input angle. Grashof classification describes the link-length set; it does not guarantee unrestricted rotation for every grounded-link choice or a useful mechanism.

A complete mechanism design must also control branch and circuit behavior, transmission angle, singularities, packaging, joint reactions, bearing life, tolerance sensitivity, stiffness, inertia, and interference through the intended motion.

Before committing a linkage

  • Sweep the entire required input range on the intended assembly branch
  • Confirm no order, branch, or circuit defect enters the operating range
  • Check minimum transmission angle and mechanical advantage
  • Model joint clearance and dimensional variation
  • Evaluate collisions, hard stops, and actuator packaging
  • Resolve dynamic loads, balance, fatigue, wear, and lubrication

Direct senior involvement

Turn the product decision into a clear next step.

Share a non-confidential summary, the current stage, and the outcome the team needs.

Discuss Your Project