Thanks for the info, Mike. Because friends know I'm a railfan, I often get questions about the horsepowers of the 3985 and 844 locomotives when they make their appearances here. People seem to be really inquisitive about the "brute power" of these machines, probably because of their massive size and their very visible and impressive driving mechanisms. And there always seems to be the curiosity about how they compare with today's locomotives that replaced them. Although I was aware that steam locomotive horsepower is variable depending on speed, I appreciate your insight about comparisons with diesel-electrics being misleading - and your recollection of a peak horsepower output of the Challenger.