Project 33

C1 — Four-bar linkage with over-center locking

Paper claim: The folding-fin mechanism uses a four-bar linkage with over-center locking at θ_toggle=92° to secure fins in the deployed position.

Recomputed result: Deterministic parameter sweep completed across ground link (20-30mm), coupler (55-65mm), input link (12-18mm), and output link (12-18mm). The baseline design (ground=25, coupler=60, input=15, output=15) yields:

• Grashof condition: change-point
• Transmission angle range (0° to 92°): 78.46° to 101.54° (well within recommended 40°-140° limits)
• Over-center detection: confirmed (moment sign flips from negative to positive at toggle)
• Swept envelope: compliant (radius < 2.5x body radius)

Artifact paths:

• docs/EVIDENCE/C1_four_bar_sweep.json
• docs/EVIDENCE/C1_four_bar_plot.png

Deterministic parameter sweep — no physical measurement

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