[rockpaperscissor]

Based on the drawing in your initial post, I expected that the horses would be walking around on a circular track, driving a single shaft that turned both paddlewheels, so I was a bit confused when I saw your in-progress diagrams in your second post. Then I went back and read your first post a little closer. The belt type treadway design you're building is different from the drawing, but might be preferable since each paddle wheel was driven independently. If one horse was made to stop, it could turn on a dime. Cool