bennett
Bennett's four-bar at 40°
Four bars, four revolute joints, and axes that are not parallel — a spatial four-bar, which Kutzbach counts at -2 degrees of freedom. Bennett's condition, sin α / a = sin β / b, makes the screw system rank 3 instead of 4, so the mechanism has 1. Driving the first joint through a full turn, 48 of 48 positions assemble. Orthographic projection, viewed from 40° azimuth and 24° elevation; dashed stubs mark the joint axes.
Out of the planedraggable: first jointwide
Where it is used
- Six freedoms, not three Out of the plane
- The joint that is not constant velocity Out of the plane
- Bennett, and the condition that moves it Out of the plane
- Fragility has a direction As built
- Bennett's condition is a ratio Out of the plane
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