Has anybody built any experimental/ prototype design engines? I'm just curious because I'm very interested in all the concept rotary/super efficiency/crazy claims engines and I'm currently in the process of designing my own. (which I swear I will actually build) ;D But anyway, from seeing so many conceptual videos of cool engine ideas, but very few running prototypes, I wonder what these people are waiting for. I mean, everyone here could probably build them in a matter of days by simply looking at the conceptual animations and seeing how it works. Has anybody done anything like that? Some examples of the concepts I'm talking about are the Scuderi, libralato, Liquidpiston, Rad Max, astremo, Revetec, Ox2, Star Rotor, Anroon, Hefley, or even the Wankel engine. Some of these are truly fascinating mechanisms.