Author: Haijun Su, Professor, Department of Mechanical & Aerospace Engineering, The Ohio State University
ME 3751 Kinematics and Mechanism Design
Grashof Condition for 4-Bar Linkages:
For a planar 4-bar linkage with link lengths s (shortest), l (longest), p, q: s + l < p + q → Grashof linkage s + l > p + q → Non-Grashof linkage s + l = p + q → Change point (special case)
Double Crank: (Grashof) Shortest link is the ground link. Both input and output can fully rotate.
Double Rocker: (Grashof) Shortest link is the coupler link. No link can fully rotate.
Crank-Rocker: (Grashof) Shortest link is the input or output link. That link can fully rotate, others are rockers.
Double Rocker (Non-Grashof): No link can fully rotate.