At the Indiana State Fair this year, Tam and I saw an amazing -- and, I suppose, twee -- miniature steam traction engine, about half-scale, plenty big enough to ride aboard. It was steaming gently, clearly functional.
It turns out to be the work of Harold Stark, Master Steam Engineer, who's been a major part of the working antique farm machinery exhibit at the fair for the past 31 years. He's quite a guy. You'll find the short video and a little biography at Artisan Ancestors.