Machinery TwinFour-bar linkage
The workhorse planar mechanism, rockers, clamps, transfer arms.
The four-bar linkage is everywhere in machinery: rocker arms, clamps, box-erector flaps, walking-beam transfers. One input angle drives the whole loop; the solver computes the coupler and output link exactly.
Parameters
| Parameter | Meaning |
|---|---|
| Motion variable | Input link angle in degrees |
| Links | 4 links, each with a length and its own model slot |
| Four-bar solution | Which assembly branch to use |
The solver uses the Freudenstein formulation: given the four link lengths and the input angle, the remaining joint angles are solved in closed form each frame.
The solution flag
A four-bar can assemble in two branches ("open" and "crossed"). If the linkage draws inverted relative to the real machine, flip four-bar solution.
Not every angle is reachable
Depending on the link-length proportions (Grashof condition), the input may only be able to rock through a limited range, beyond it, the loop cannot close and the solver has no solution. If parts jump or vanish at the extremes of travel, your input variable is leaving the mechanism's feasible range: clamp it with the variable's min/max to the physical rocking range.
Dressing the links
Each of the links (input, coupler, output, plus the fixed ground) has its own model and model-space offset. Attach additional objects (grippers, product plates) to a link via the hierarchy to ride the coupler curve.