This site describes a new engine design having these key benefits:
The new design is substantially simpler than a conventional Stirling engine. Until now, ultra simple heat engine designs were generally devices that rocked or vibrated but did not rotate. This new design is extremely simple and rotates. (This site assumes familiarity with conventional Stirling engines. To learn about Stirling engines search for them at google.)
The new design unifies the displacer and flywheel. Unification is achieved by placing the flywheel inside the displacer chamber, placing the hot and cold plates adjacent to each other instead of parallel to each other, and using a D-shaped displacer attached to the flywheel. Although a low temperature differential (LTD) model is described, the concept extends to HTD configurations.
With the chamber held horizontally (like a pie) the hot and cold sides are to the front and rear respectively instead of top and bottom. A rotating flywheel/displacer rotates the air in the chamber between the hot and cold regions. An external piston is the only other significant moving part and is oriented parallel to the chamber instead of perpendicular.
This configuration has several advantages over the conventional configuration, including:
The compactness comes from eliminating the 90 degree relationship of the flywheel to the displacer chamber.
Although this design has less points of friction than a conventional Stirling engine, it is slightly less efficient as it lacks dwell time and a regenerator, and chamber air turbulence is lower. It is not the first pseudo-rotary heat engine but it is the simplest. This site shows the simple parts needed to build the engine. The model shown has a 6 inch chamber diameter.
Note 1: We do NOT offer a kit of any type - however you can use emachineshop.com to design and make many of the parts.
Note 2: I did this project many years ago and am not active in this area - working on other projects now.