The Train Too Rigid To Turn — The Terrifying Physics Of Union Pacific's 30-Foot Monster

The Union Pacific 9000 class was an audacious attempt to solve a massive freight crisis in the 1920s. By placing twelve rigid driving wheels under a massive boiler, ALCO engineers created the 4-12-2 locomotive. While it generated incredible pulling power, its rigid thirty-foot frame, complex Gresley valve gear, and hidden third cylinder created severe maintenance issues and aggressive track wear before high-speed articulated steam locomotives finally made this rigid design obsolete.