Wax Motors: The Tiny Thermal Actuators That Lock Your Washing Machine and Fly Your Airplane
A wax motor is a linear actuator that converts thermal energy into mechanical motion by exploiting the 5–20% volume expansion of wax as it melts. These simple, passive devices generate up to 4000 N of force and are used in aerospace, washing machines, dishwashers, greenhouse vents, and hydronic heating. They offer smooth operation, low cost, and fail-safe reliability compared to magnetic solenoids.
When the heat source is energized, the wax block is heated and it expands, driving the plunger outwards by volume displacement.
- limaoscarjuliet
Wikipedia page has a small error. It shows an actuator (i.e. wax motor) described as thermostatic radiator valve https://en.wikipedia.org/wiki/Wax_motor#/media/File:Thermisc...
These are two separate things: thermostat will close and open based on surrounding temp., the actuator on the other hand opens and closes based on energizing a heating element that is driven by a separate thermostat.
Wax motors are pretty cool things. They rarely fail and do their job even in damp environments. I take care of my better half's hotel with approx 100 of these installed and we replace one of these once every couple of years.
- palmotea
If you want to see one in action, I found this: https://www.youtube.com/watch?v=sApyrDEXGAI
- cbdumas
I'm surprised this page doesn't mention the automotive thermostat which uses the same principle to control the flow of coolant between the engine block and radiator in an ICE vehicle.
- kazinator
The expansion of paraffin wax is substantial. I have experience wax potting guitar pickups as well as bicycle chains. I use a skinny, tall tin can for this, placed in boiling water. When the liquid wax solidifies, it not only pulls away from the sides of the can so that the resulting ingot slides out freely, but a void forms in the center. The top surface has a depression and a deep hole in the center.
- WJW
Using this as a greenhouse vent actuator is pretty cool. It just makes so much sense.