This Book is a practical introduction to a whole new branch of stirling engine technology. The Ringbom engine is a hot air engine with a normal crank coupled piston but with a displacer free of any mechanical linkage. The displacer is driven anuomatically by changing pressure within the engine. this makes the ringbom an utterly fascinating engine to see in operation and opens up a wide new world of possible configuration for stirling engines.This is a how to book for making working engines with detailed plans and instructions for making three different model ringbom engines.