Union Pacific 3985

Union Pacific 3985
Union Pacific Challenger No. 3985 runs through Alton, Iowa, on October 1, 2008
Type and origin References:[1] Power type Steam Builder American Locomotive Company (ALCO) Serial number 70174 Build date July 1943 Rebuild date 1979–March 1981 (first restoration) January 2023–ongoing (second restoration)
Specifications Configuration: ​  • Whyte 4-6-6-4  • UIC (2′C) C2′ h4 Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Driver dia. 69 in (1,753 mm) Wheelbase 60 ft 4+1⁄2 in (18.402 m) Engine 121 ft 10+7⁄8 in (37.157 m) Engine + tender Axle load 67,333 lb (30,542 kilograms; 30.542 metric tons) Adhesive weight 404,000 lb (183,000 kg; 183 t) Loco weight 627,900 lb (284,800 kg) Tender weight 446,000 lb (202,000 kg) Total weight 1,073,900 lb (487,100 kg) Fuel type No. 5 fuel oil, originally coal Fuel capacity 32 short tons (29 t; 29 long tons) 6,450 US gal (24,400 L; 5,370 imp gal) Water cap. 25,000 US gal (95,000 L; 21,000 imp gal) Firebox: ​  • Grate area 132 sq ft (12 m2) (grate removed in 1990) Boiler 94 in (2,400 mm) Boiler pressure 280 lbf/in2 (1.93 MPa) Heating surface: ​  • Firebox 140 sq ft (13 m2)  • Tubes 527 sq ft (49.0 m2)  • Flues 3,687 sq ft (342.5 m2)  • Total surface 4,795 sq ft (445.5 m2) Superheater: ​  • Type Type E  • Heating area 2,162 sq ft (200.9 m2) Cylinders Four Cylinder size 21 in × 32 in (533 mm × 813 mm)
Performance figures Maximum speed 70 mph (110 km/h) Power output 5,000 hp (3,700 kW) Tractive effort 97,350 lbf (433.03 kN) Factor of adh. 4.15
Career Operators Union Pacific Railroad Class 4664-4[2] Number in class 11 of 25 Numbers UP 3985 UP 3967 UP 3718 CRR 676 Nicknames "The Challenger" Delivered 1943 First run 1943 (revenue service) May 1981 (excursion service) Last run 1957 (revenue service) October 14, 2010 (excursion service) Retired 1962 (revenue service) January 2020 (excursion service) Restored March 1981 (first restoration) Current owner Railroading Heritage of Midwest America Disposition Undergoing restoration to operating condition

Union Pacific 3985 is a four-cylinder simple articulated 4-6-6-4 "Challenger"-type steam locomotive built in July 1943 by the American Locomotive Company (ALCO) of Schenectady, New York, for the Union Pacific Railroad. No. 3985 is one of only two Challengers still in existence and the only one to have operated in excursion service.

No. 3985 operated in revenue service until 1957. It was then stored in the roundhouse in Cheyenne, Wyoming, until 1975, when it was placed outdoors beside the Cheyenne depot. In March 1981, after a group of Union Pacific employees restored the locomotive to operating condition, it was placed into excursion service as part of the Union Pacific's heritage fleet and became the world's largest operational steam locomotive. Mechanical problems took it offline in 2010, after which it was stored at the Union Pacific's Steam Shops in Cheyenne.

In May 2019, the title of largest operational steam locomotive passed to the newly restored 4-8-8-4 "Big Boy" Union Pacific 4014. No. 3985, still in poor mechanical condition, was retired from excursion service in January 2020. In April 2022, UP officials announced that the company would donate the locomotive to the Railroading Heritage of Midwest America (RRHMA), which is now restoring the locomotive to operating condition.