This is a Stirling engine which is a type of heat engine. It needs about a 50 degF (28 degC) heat differential to run and cruises about 300 rpm unloaded. All the plans and information to build this engine is now available. You can see lots of information about the engine with a video of it running at http://www.solarheatengines.com/2012/10/29/3d-printed-stirling-engine/The zip file contains all 11 3D printed parts for the engine. PDFs provide assembly drawings and parts drawings. A discussion of building these parts is available at http://www.solarheatengines.com/2012/11/21/3d-printed-stirling-engine-now-open-source/An assembly and BOM PDF is now available. More assembly details are available at http://www.solarheatengines.com/2012/11/27/3d-printed-engine-bom-and-assembly-instructions/ I've posted an article on building the regenerator for the PE2 engine. If you build the engine you want to be sure to build one for good performance. I've included information for those wanting to learn more about Stirling engine regenerators too. http://www.solarheatengines.com/2012/12/18/a-regenerator-for-the-3d-printed-pe-2-stirling-engine/I've posted an article on alternate designs for the power piston and the displacer. These new designs will not affect the engine performance, but may be simpler to build. The STL files are available in piston insert 3.zip and displacer3.zip. The article is at: http://www.solarheatengines.com/2012/12/31/new-power-piston-and-displacer-for-3d-printed-stirling-engine/To build this engine you need a drill press to accurately drill out the rough 3D printed holes and for drilling the aluminum plates. Some simple lathe work is necessary to machine the power piston to fit in the brass tube.