I wonder what the difference between them is for mean time between boiler repair and ton/miles. The earliest steamers needed a great deal of maintenance to run well, whereas a modern steamer could go many hours with just fuel, water, and periodic hand lubing and inspections. Boiler HP, and this is just a guess for the Dewitt Clinton, would be 100 HP vs. 4500 for the Challenger. Tractive effort would have been maybe 1000 lbs (?) vs 97K lbs for the UP Challenger. Note that other challengers were much more powerful and generated more TE than the UP 3900 Class. In fact, a Pennsy two cylinder J1 2-10-4 was within about 1000 bs of TE.