big boy

Union Pacific’s No. 4014, the world’s largest operating steam locomotive, is currently touring the East Coast to celebrate America’s 250th anniversary. Measuring 133 feet long and weighing 1.2 million pounds, the historic 4-8-8-4 articulated engine is touring Pennsylvania before continuing its multi-state summer route. The Union Pacific Big Boy produces a starting tractive effort of 135,375 pounds-force (lbf), which translates to roughly 360,000 to 380,000 lb-ft of turning torque at the rails depending on wheel slip limits.Power and Pulling StatisticsTractive Effort: 135,375 lbf (602.18 kN) — the pulling force measured at the rim of the driving wheels.Horsepower: 6,290 to 7,000 horsepower at the drawbar.Driving Wheels: 68 inches in diameter with a 32-inch piston stroke operating at 300 psi boiler pressure.