The beta-Stirling engine as its analog engine alpha- Stirling , is an external combustion engine. That allows it to work on any kind of fuel and even solar energy.
A distinctive feature of beta-Stirling engine is that it has only one cylinder. Displacing and working pistons are on the same axis inside the cylinder. The rule of pistons motion is determined by the peculiarities of two gears system and a rhombic drive construction.
This interactive 3D model shows the principle of beta-Stirling construction and operation.