'Big Boy,' the 1.2M pound locomotive, still operates like it did in the mid-1900s

DENVER (KDVR) — One of the world's largest locomotives passed through Colorado in October, operating much like it did when it was first built in the mid-1900s.

The train, known as Big Boy No. 4014, was one of several 1.2 million-pound locomotives built in the 1940s. However, they all went out of commission, including Big Boy No. 4014, which traveled over a million miles within its 20 years of service.

Since retirement, many of the locomotives have been in museums across the country, including Big Boy No. 4014. That was until Union Pacific began the multi-year restoration process that turned it into the world’s largest operating steam locomotive.

After a lengthy restoration, the train began its “Heartland of America Tour,” which started in Wyoming in late August and stopped in Colorado this week. While the train was repaired with some modern upgrades, it runs nearly the same.

Inside 'Big Boy,' the 1.2M pound train

According to Mike Jaixen with Union Pacific, Big Boy No. 4014 operates much like it did in the 1940s and 50s.

Jaixen said it runs by water heated in the boiler, which creates 300 pounds per inch of steam pressure that drives the locomotive's wheels. Meanwhile, there are three tenders, or separate vehicles, behind the locomotive. The black tender contains fuel oil and water and the two yellow are filled with water.

While the locomotive runs the same, the process is a little different now.

"In the 1940s and 1950s, steam locomotives would stop periodically at watering towers to refill their water tender, but those were all decommissioned 60 years ago. Now, the Big Boy has to bring its own water supply for a full day of operation," said Jaixen.

Behind the train's body are support cars, which Jaixen calls a "rolling tool shop," where the crew brings their own tools. This is different than when it was built because rail networks had equipment to maintain and repair steam locomotives, but today, Jaixen said those facilities now support the regular diesel-electric locomotive. 

The tool shop is a slight modification, the only major difference in the locomotive is the brakes.

Jaixen said the brakes were custom-made when it was restored, and the crew brings along a modern diesel-electric locomotive and some empty freight cars to help with braking. 

"While the Big Boy's brakes were standard items in the 1940s and 1950s, they now have to be custom made and it's easier to rely on the diesel-electric locomotive to handle the braking load," said Jaixen.

On Wednesday, the train left Colorado, ending its tour in Wyoming.