Most historical photos of donkey engines that helped revolutionize the logging industry show them with their "clothes on" under a roof. We can see the wood burning steam engine, but not the series of wheels and cables that really made them a workhorse in the woods. I recently ran across a couple of photos that show them "naked".
Photo courtesy University of Washington Libraries, IND0235, n.d.
Both are mounted on skids that can be drug from logging site to logging site. For me, it's all the cables, gears, drums and pulleys that make them interesting.
Photo courtesy University of Washington libraries, IND0207, n.d.
Better hope that one of those cables doesn't snap. Probably not the safest place to be around.