PREORDER Athearn Genesis HO G97972 4-6-6-4, Union Pacific #3933 | 569.49

The name "Challenger" was given to steam locomotives with a 4-6-6-4 wheel arrangement. This means that they have four wheels in the leading pilot truck, which helps guide the locomotive into curves, two sets of six driving wheels, and finally four trailing wheels, which support the rear of the engine and its massive firebox. Each set of six driving wheels is driven by two steam cylinders. In essence, the result is two engines under one boiler. The Union Pacific Railroad sponsored development of this type to meet the need for higher speeds in main-line service. Historically, articulated locomotives had been limited to slow speeds by factors inherent in their design. The technical breakthroughs achieved with the Big Boy enabled the carrier to develop a newer, improved Challenger that met their speed expectations.

Though originally intended for freight service, many Challengers were used in passenger service.

Union Pacific
In the spring of 1941 UP locomotive designers began working on a locomotive to team up with the new 4-8-8-4 Big Boy's then under construction at Alco. The Big Boy's were designed to pull heavy freights up the Wasatch Range in Utah to the division point at Green River, WY. What was needed was a locomotive to take over at that point that could speed the freights eastward across the Wyoming Division. Building on their experience with the original CSA 4-6-6-4 Challengers UP and Alco's designers developed a newer and better Challenger type locomotive. The result was a group of 65 4-6-6-4 Challenger built in three separate groups during World War II.

ROAD NUMBER SPECIFIC FEATURES:
#3985
Modern Excursion version
Oil Burner
Era 1980s - 2000s

#3933
Coal Burner
Dual smoke stack
Tender bunker coal extensions
Era 1940s - 1959

#3967
Coal Burner
Dual smoke stack
Smoke Lifters
Era 1940s - 1959

#3997
Coal Burner
Dual smoke stack
Tender bunker coal extensions
Era 1940s - 1959

UP painted several of their Challengers in their two-tone grey paint scheme for passenger service. They also added smoke lifters and converted many to oil burners as well.

ROAD NUMBER SPECIFIC FEATURES:
#3976
Two-tone grey with yellow lettering and striping
Oil burner
Dual smoke stack
Era Late 1940s - Mid-1950s

STEAM LOCOMOTIVE FEATURES:
Illuminated number boards and headlights
Headlight turns off in reverse
Illuminated directional back-up light in the tender
Correctly operating eccentric cranks
Adjustable top cab vent and cab windows
Pivoting front and rear engines for negotiating 18" radius curves
Current pick-up on all driver and wheels
Boiler backhead with full details and printed gauges
Synchronized chuff, whistle, bell, blow-down, air compressor, dyno and pop-off valve sounds
User-controlled whistle, short whistle, bell, squeal, coupler crash, injector, water stop and light dimmer
Individually-applied detail parts, including brass-painted bell and whistle, piping, valves, generator, steps, air pump, air tanks, reverser and coupler lift bar
Front coupler pocket can be inserted to mount operating coupler
Minimum recommended radius: 22"