3D printed marble Stirling engine

This type of Stirling engine, known as the beta configuration, features just one cylinder with a hot end and a cool end. The working gas is transferred from one end of the cylinder to the other by a device called a displacer (here the marbles do the job of displacer). The marbles have a smaller diameter than the cylinder, thus their motion does not change the volume of gas in the cylinder they justtransfer the gas from the hot end to the cold end. Motion of the marbles is obtained with an appropriate inclination of the cylinder. When the gas expends, it pushes the syringe piston which turns the wheel and reaches a heigher position, the marbles will roll towards the hot end... The gas beeing pushed toward the cold end, it retracts and pulls the piston which returns to its bottom position. Then the marbles are rolling toward the cold end driving the gas toward the hot end, and the cycle goes on ...

Well, it's easier to see it running here ;-)
Please, don't forget to turn the so