I know the the six NW SD50S were considered pre-production units. I have read that they were supposedly built on SD40-2 frames and were thus slightly shorter thatn the production SD50. However after looking at photos of both I can’t see any noticeable difference. Does anyone know if there are any visual differences between the S and the standard SD50?
Yes, the NW/NS EMD SD50S locomotives were built on the same length frame as the SD38-2, SD40-2, SD45-2 and KCS SD40X models. On the SD50S, the engine compartment is 24" shorter at the rear, having one less door per side than a production SD50. The radiator compartment is the same length on both models, but the hood door/latch arrangement under the radiator grilles also differs.
Chris Toth
The Utah Railroad units 6060-6064, ex Hamersley Iron in Australia (and built in Australia) are also SD50S units built on the shorter frame.
To meet the cooling demand in their original location, their radiator intakes were moved downward to improve airflow through the cores, and the rear grille was deeper than the forward grille.
M636C