Since disassembling UP No. 4014, the ‘Big Boy,’ the Union Pacific Steam Team has cleaned, inspected and repaired nearly every part of the locomotive down to its smallest piece.

Now, the UP Steam Team, headed by Ed Dickens, is putting it all back together starting with the boiler’s fire box and combustion chamber.

“Modern American steam locomotives use what is known as a fire tube boiler with a stay bolted firebox,” Dickens said. “As the coal fuel is burned on the grates inside the fire box, the combustion gases flow through the fire tubes to the smoke box in the front of the locomotive. There, the smoke is driven out very rapidly by the exhaust steam pressure from the two engines on the 'Big Boy' out of the smoke stack.”

March 2018 Steam Update Ed Dickens, who heads the Union Pacific steam team, talks through the work being done to put the 'Big Boy' back together, starting with the boiler's fire box and combustion chamber.

The exhaust steam is channeled out through precisely cast bronze nozzles that create steam flow up and out the twin UP-designed smokestacks. This creates the characteristic locomotive sound as the steam blasts upward creating the very strong draft that provides combustion air in the firebox for the fuel burning cycle.

Dickens described the nature of a steam locomotive as rugged, heavy duty and quite loud.

Although originally designed to burn coal, the UP Steam Crew will convert No. 4014 to burn oil. The oil used in No. 4014 is very similar to what comes out of your car during an oil change.

“This was a common practice during the age of steam locomotive operations,” Dickens said. “In today’s railroad network, the use of coal would present numerous challenges and safety risks, whereas the use of fuel oil makes for a cleaner, safer operation.”

Locomotive No. 4014’s front engine rests in the foreground, and in the background sits the locomotive’s smoke box with its door wide open.

The crew will fabricate a new oil-burning system, which consists of a fire pan below the level where the coal-burning grates once were located. An oil burner will flow and atomize the fuel oil into a fine mist.

This fine mist mixes with combustion air that, when properly handled by a skilled UP steam-trained firemen, results in a giant fire ball inside the firebox/combustion chamber. The tremendous heat energy is transferred to the water through boiler plates in the fire box, combustion chamber and tubes and flues, generating the massive power of the steam locomotive.

Dickens said rebuilding a big boiler is labor-intensive with many steps, but the crew enjoys the process. “The long-term payoff will be very rewarding.”