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UP 4-8-8-4 Big Boy N XL L M4

Equipped with ESU "FULL THROTTLE STEAM" features!

During the late 1930s, the Union Pacific often used helpers to move trains from Ogden to Wasatch. The UP wanted to simplify this move so they asked their "Department of Research and Mechanical Standards" (DoRMS) to design a locomotive that could pull a 3600 ton train unassisted over the 1.14% grade of the Wasatch.
The designers determined that to pull a 3600 ton train, a tractive effort of 135,000 lbs would be needed. Assuming a factor of more…