Project ForgeA planar closed kinematic chain is formed with rigid links PQ=2.0 m, QR=3.0 m, RS=2.5 m and SP=2.7 m with all revolute joints. The link to be fixed to obtain a double rocker (rocker-rocker) mechanism is
- APQ
- BQR
- RS
- DSP
Explanation
Shortest link s=PQ=2.0, longest l=QR=3.0; other two are RS=2.5, SP=2.7. Since s+l=5.0 < RS+SP=5.2, this satisfies Grashof's criterion (a Grashof chain). For a Grashof chain, fixing the link OPPOSITE the shortest link produces a double-rocker mechanism (the shortest link then becomes a fully-rotating coupler, not connected to the frame). PQ's opposite side in the quadrilateral loop P-Q-R-S is RS, so fixing RS gives the double-rocker.
Source: GATE ME 2013 (Booklet Code A) (2013)
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