Why were the Big Boys built?

January 25, 2016  •  Leave a Comment

Why were the Big Boys built?

The Union Pacific (UP), along with many other railroads needed more power to pull ever longer and heavier trains.  Beginning in the early 1900’s railroads sought other means of pulling the trains other than just adding more engines and crews to pull the freight.  The articulated locomotive was developed by a Swiss engineer named Mallet.  He took two engine-driver wheel sets, and hinged one in front to turn, rather than a longer, rigid frame, which made it more difficult to manage curves in the tracks.

These Mallet’s, or articulated locomotives gave the railroads what they needed in larger, heavier, and more powerful  locomotives to pull those heavier trains.  Most Class I railroads, like the UP, built a variety of sizes of these behemoths.

The UP 4014 and her 24 sisters were the culmination of this type of steam engine, as the diesel age had begun, and more and more of the diesels were added to the fleets of railroad power.  The Big Boys were the last steam engines built for the UP and were used to pull the long freights over Sherman Hill in Wyoming.

More information about these locomotives here:




No comments posted.