Re: Locomotive Steam Characteristics

Good subject...one example that comes to mind is the pair of Baldwin-built 2-6-6-2T locomotives built for Bloedel-Donovan on Washington States Olympic Peninsula. These two finished up their careers with Rayonier painted on the tanks.
The 9 was the better steamer, but had some boiler issues and was facing expenive work when the first two diesels arrived in the mid 50s, so she got the torch.
Sister 8 had more life in her and indeed, lasted as a standby until the summer of 1964, but was a turd to fire. Consecutive builders numbers and probably sat right next to each other on the erecting floor, but they are pieces of machinery and are not completely alike.
It could have also been inadvertent changes that came along over the years, like burner placement, a slipped petticoat, one having more scale buildup than the other, etc.