Escapement Lift Angle
The angular displacement of the balance roller pin while in contact with the pallet fork slot during energy transfer. Essential for timing machines (Witschi / Weishi) to compute balance amplitude accurately.
\[ \alpha_{lift} = \theta_{pallet\_lock} + \theta_{impulse\_face} + \theta_{drop} \]
Plain Text Formula:
Lift_Angle = Pallet_Lock_Angle + Impulse_Face_Angle + Drop_Angle
📐 Variable Definitions & Parameters
| Symbol | Variable Name | Standard Unit | Physical Definition |
|---|---|---|---|
| \[ \alpha_{lift} \] | Escapement Lift Angle | degrees (°) | Standard caliber lift angle (typically 48°–54°) |
| \[ \theta_{pallet\_lock} \] | Locking Angle | degrees (°) | Angle traversed during stone unlocking |
| \[ \theta_{impulse\_face} \] | Impulse Face Sweep | degrees (°) | Angle traversed along pallet jewel impulse plane |
💡 Worked Engineering Example
Problem Statement:
Explain why setting the lift angle to 50° instead of 53° on an ETA 2824-2 distorts amplitude readout on a timing machine.
Step-by-Step Solution:
- Timing machines measure the time delta between unlocking noise and drop noise
- Apparent amplitude scales proportionally with lift angle setting
- Delta = (53° - 50°) / 53° ≈ 5.66% under-reporting
🎯 Result: Entering an incorrect lift angle skews amplitude reading by ~16°.