This example animation is of a rotary engine, which I found particularly hard to envision when it was explained to me, and even when looking at diagrams in a book. But animated like this, it seems so simple and elegant. The others are just as interesting.
Please note: I've moved my active blogging over to a new site, called Jason Clarke - Infinite Bass Line. I will leave this site up indefinitely, but if you're interested in my latest posts please consider visiting the new site.