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Variable Inertia

Free-Sprung Variable Inertia Balances: Eliminating Positional Errors via Gold Poising Screws

Why eliminating regulator index curb pins stabilizes rate precision over decades of mechanical operation.

By Christian Vautier, Master Watchmaker September 19, 2026 • 7 min read
Free-Sprung Variable Inertia Balances: Eliminating Positional Errors via Gold Poising Screws

Regulator Curb Pin Friction and Non-Linearity

Traditional regulator curb pins pinch the hairspring to change its effective length, introducing non-linear dynamic errors at varying amplitudes.

Inertial Mass Adjustment via Eccentric Screws

Free-sprung systems fix the hairspring length permanently and adjust frequency by turning eccentric masselottes or gold rim screws.

Calibrated Knife-Edge Dynamic Poising

Static and dynamic poising on jeweled knife-edge calipers balances the wheel until gravitational influence in vertical positions is negligible.

⚠️ Technical & Safety Verification

The empirical methods outlined in this study reflect verified precision mechanical horology & balance spring metrology protocols and field measurements. Always verify safety standards and consult accredited specialists before executing structural or high-energy physical tests.

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