The Union Pacific was the sole purchaser of these engines, owning and operating a total of 25 of the colossal 600 ton engines. The 4-8-8-4 wheel arrangement combined stability and power, with the four wheel leading truck allowing for smoother entry into curves while the two sets of 8 drive wheels provided 135,375 lbf of tractive force. The trailing four axle truck helped support the large firebox that was needed to keep the massive engine fed. The original Big Boy engines were coal powered, with 4014 being converted to oil when it was rebuilt after its retirement to be used in excursions.The Big Boys plied the rails as reliable workhorses until the final unit was retired from revenue service in 1959, with eight engines surviving today. Kato's N scale Big Boy engine is a wholly new and unique design from any steam engine that has come before, utilizing two coreless motors in dual articulated metal mechanisms to power the 16 total driving wheels. Thanks to the articulated design just like the real engine, the two sets of driving wheels are able to move independently which gives the engine the ability to navigate 11? Radius curves, allowing the locomotive to run with Kato's other large scale engines like the FEF-3 and GS-4. Model Features: Dual coreless motors with brass flywheels for unmatched pulling performance Weights carefully placed along the body even in the cylinders to give the engine perfect balance and weight distribution. (282mm) Operational tinted LED headlight 4014 has the iconic "Big Boy" chalk lettering on the front of the smokebox 4014 is built to match the 2021 Excursion tour appearance: - Oil Tender - Graphite Firebox - Silver cylinder head and piston covers - Builder's Plate.