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Wax motor

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Summary

Wax motors are linear actuators that turn thermal energy into mechanical motion via wax phase change. They consist of a wax chamber, a plunger, a heat source (electric, solar, combustion, ambient) and a heat sink. Wax expands 5‑20% on melting, delivering forces up to ~4000 N, with a bias spring providing 20‑30% of that force for retraction. Advantages include high force density, smooth actuation,…

  • Design: sealed wax volume, plunger, heat source (often a PTC thermistor), and heat sink; bias spring needed for re‑traction.
  • Performance: wax expansion 5‑20% yields forces ~4000 N; bias force 20‑30% of output.
  • Control: resistive load lets you drive with simple TRIACs, no snubber circuits.
  • Passive operation possible by matching wax melting point to ambient temperature range.

Wax motors offer a high‑force, low‑power alternative to solenoids where smooth, passive actuation is valuable—e.g., safety‑critical door locks or temperature‑driven venting—making them a niche but useful component in many mechanical systems.

5/10
thermal actuatorshvacaerospacepassive actuationmechanical design

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