HO 4-6-6-4, UP #3997

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: 

• Modern Excursion version
• Oil Burner
• Era 1980's - 2000's

• Coal Burner
• Dual smoke stack
• Tender bunker coal extensions
• Era 1940's - 1959

• Coal Burner
• Dual smoke stack
• Smoke Lifters
• Era 1940's - 1959

• Coal Burner
• Dual smoke stack
• Tender bunker coal extensions
• Era 1940's - 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: 

• Two-tone grey w/ yellow lettering and striping. Oil burner
• Dual smoke stack. Era: Late 1940's - Mid-1950's.

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"

NEW FEATURES: 

• Dual cube speakers for great sound quality
• Lighted firebox flicker effect with see-through firebox door
• Upgraded headlight lighting with brighter LED 
• Improved loco-to-tender connection harness for increased durability and serviceability

SOUND EQUIPPED MODELS ALSO FEATURE

• Tender-mounted DCC decoder with SoundTraxx Tsunami2 sound
• Sound units operate in both DC and DCC
• Full DCC functions available when operated in DCC mode
• Engine, whistle, and bell sounds work in DC
• All functions NMRA compatible in DCC mode
• Excellent Slow speed control
• Many functions can be altered via Configuration Value (CV) changes
• CV chart included in the box

PROTOTYPE SPECIFIC INFORMATION

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.