We apparently have a few folks that have been doing some "book learning", with no understanding of the REAL steam locomotive work environment, nor the physics involved.
1) The famous C&O H-8 was definitely NOT "unsuccessful"! Maybe the C&O never properly utilized the Lima Super Power 2-6-6-6 design to their fullest capabilities, instead of "just hauling coal".
2) The various eastern coal roads, i.e. C&O, B&O, and N&W for example, all had EXCELLENT supplies of VERY HIGH BTU coal as fuel. Thus their furnace systems were properly designed FOR THAT FUEL! By comparison, the "poor Union Pacific" was relegated to burning southern Wyoming Hanna Coal, and thus need MUCH larger fireboxes and furnace system designs, on order to burn lower BTU coal. Thus, the 4000 class locomotives truly excelled at their DESIGNED service assignments, while burning that southern Wyoming fuel. As another comparison, look what the poor Northern Pacific had to burn, i.e. Montana Lignite!
3) Trying to compare various wheel arrangements, total locomotive weights, and total locomotive lengths add nothing to a discussion of individual steam locomotive performance.
