Union Pacific Big Boy Number 4012 at Steamtown - Scranton PA
Configuration 4-8-8-4
Big Boy was the name of Union Pacific Railroad's 4000-class 4-8-8-4 articulated steam locomotives, built between 1941 and 1944 by American Locomotive Company (Alco). The class were the only locomotives to have the 4-8-8-4 wheel arrangement, with two sets of eight driving wheels, a four-wheel leading truck for stability entering curves and a four-wheel trailing truck to support the large firebox. - Wikipedia
Union Pacific Big Boy Number 4012 at Steamtown - Scranton PA
Configuration 4-8-8-4
Big Boy was the name of Union Pacific Railroad's 4000-class 4-8-8-4 articulated steam locomotives, built between 1941 and 1944 by American Locomotive Company (Alco). The class were the only locomotives to have the 4-8-8-4 wheel arrangement, with two sets of eight driving wheels, a four-wheel leading truck for stability entering curves and a four-wheel trailing truck to support the large firebox. - Wikipedia