GoKawiilA wide range of waxes can be used in wax motors, ranging from highly refined hydrocarbons to waxes extracted from vegetable matter. Specific examples include paraffin waxes in the straight-chain n-alkanes series. These melt and solidify over a well-defined and narrow temperature range.
Design [ edit ]
The principal components of a wax motor are:
An enclosed volume of wax
A plunger or stroke-rod to convert the thermo-hydraulic force from the wax into a useful mechanical output
A source of heat such as: Electric current; typically a PTC thermistor, that heats the wax Solar radiation; e.g. greenhouse vents Combustion heat; e.g. excess heat from internal combustion engines Ambient heat
A sink to reject heat energy such as: Convection to cooler ambient air Peltier effect device arranged to transfer heat energy away
When the heat source is energized, the wax block is heated and it expands, driving the plunger outwards by volume displacement. When the heat source is removed, the wax block contracts as it cools and the wax solidifies. For the plunger to withdraw, a biasing force is usually required to overcome the mechanical resistance of seals that contain the liquid wax. The biasing force is typically 20% to 30% of the operating force and often provided by a mechanical spring or gravity-fed dead weight applied externally into the wax motor (Duerig 1990, p. 214).
Depending on the particular application, wax motors potentially have advantages over magnetic solenoids: