5 rolling marbles act as the displacer in this engine. The rigid connection between the piston and conrod is what tips the test tube, rolling the marbles.
Model of stirling engine realized by a syringe and a test-tube.
In the family of heat engines, 'Stirling engine' defines a closed-cycle regenerative hot air engine (or other permanent gas) engine, though the term is often used incorrectly to refer generically to a much wider range of hot air engine types. In this context, "closed-cycle" means that the working fluid is permanently contained within the system, whereas "open-cycle" engines such as internal combustion engine and some st...