Jim,
everyone can watch the videos of my built models on youtube under "charly05ize". Among others the Callahan inspired engine after Doug Kelley & other American (Galloway 5 HP) & German engines (e.g. "Daimler - Maybach" test engine 1883) & a "Dürkopp" trunk piston engine. There is also an atmospheric gas engine from "Otto & Langen 1867", to name just a few. There are also Stirling engines, flame eaters and steam engines to see. So there is something for everyone who wants it.
Greetings Karl