u.p. big boy articulated locomotive 4-8-8-4

Last crawled date: 11 months, 2 weeks ago

The only significant 4-8-8-4 locos built were the union pacific 4000 'Big Boy' class. the u.p. big boys were an expansion of the 4-6-6-4 'challenger' type of articulated locomotive. large diameter wheels were fitted to allow higher freight speeds in terrain with uphill grades. adding two more sets of driving wheels increased the pulling power of the loco and lessened the need for helper locomotives over steep grades for a given tonnage train. other american railroads considered buying 4-8-8-4s, including the Western Pacific Railroad, which already rostered large 2-8-8-2s and 4-6-6-4s, but diesel locomotives were gaining popularity and soon were able to displace these monster locos. they have since become iconic to the Union Pacific Railroad. #articulated_locomotive #articulated_steam_engine #big_boy #sherman_hill #train #up #union_pacific