I really enjoy the section of the site on engine designs; some of them are even animated, like this bit: http://www.douglas-self.com/MUSEUM/POWER/unusualICeng/

I really enjoy the section of the site on engine designs; some of them are even animated, like this bit: http://www.douglas-self.com/MUSEUM/POWER/unusualICeng/axial-ICeng/axial-IC.htm http://www.douglas-self.com/MUSEUM/POWER/unusualICeng/axial-...