There was an open air version of one of these in Exxon USA when I worked there. It was built in the early 1900's I believe. The paddles on the one I saw were maybe sixteen by eighteen inches or a little bigger, quite small! There wasn't a whole lot of gap between them either. It went from one level to the next in a unit in the chemical side of the plant best I recall. I looked at it many a time contemplating riding it. Always chickened out! Seemed like a lot of bad things could happen and Exxon would fire contractors in a heartbeat! Thought Trump was tough on TV? Exxon: "You are fired, ... and take your arm with you as you go!"
Hu