| Beautiful original photo of the 1937 Alco built Challenger just recently delivered to Union Pacific when this photo was taken by an unknown photographer. Specifics - class CSA-2, 69" drivers, impressive 255 psi boiler pressure, 22x32" cylinders (4), massive engine weight of 566,950 lb, impressive tractive effort of 97,305 lb. Union Pacific eventually had 105 4-6-6-4 Challengers on their roster before falling to the diesel revolution. This locomotive was converted to burn oil in 1944, renumbered to 3831, retired in June 1957. |