re: #169 Varek Raith

They were pretty much the at the limit of steam/boiler technology with these things.
And that wasn’t enough. Some lines over the Wasatch mountains needed two of them to get over the grade and to prevent it from running away once on the other side.

The Wikipedia article says otherwise, though. According to teh wiki, the load capacity of the Big Boy was uprated.

. Towards the end of their career, the Big Boys could still pull more than their rated tonnage of 6,573 tons (6,573 t). The Big Boys’ ratings were increased several times until they regularly pulled 8,727 short tons (7,917 t) over the Wasatch range.

en.wikipedia.org