Union Pacific Challenger
|Union Pacific Challenger|
UP 3985 running through Alton, Iowa in October 2008
|Type and origin|
|Builder||American Locomotive Company (ALCO)|
|UIC classification||(2′C)C2′ h4|
|Gauge||4 ft 8 1⁄2 in (1,435 mm)|
|Driver diameter||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
|Weight on drivers||404,000 lb (183.3 t)|
|Locomotive weight||627,900 lb (284,800 kg)|
|Tender weight||446,000 lb (202,000 kg)|
|Locomotive and tender
|1,073,900 lb (487,100 kg)|
|Fuel type||Coal, UP 3985 converted to No. 5 fuel oil|
|Fuel capacity||32 short tons (29 t)
6,450 US gal (24,400 l; 5,370 imp gal) UP3985
|Water capacity||25,000 US gal (95,000 l; 21,000 imp gal)|
|Boiler pressure||280 lbf/in2 (1.93 MPa)|
|527 sq ft (49.0 m2)|
|– Flues||3,687 sq ft (342.5 m2)|
|– Firebox||500 sq ft (46 m2)|
|– Total||4,795 sq ft (445.5 m2)|
|Superheater area||2,162 sq ft (200.9 m2)|
|Cylinder size||21 in × 32 in (533 mm × 813 mm)|
|Maximum speed||70 mph (110 km/h)|
|Tractive effort||97,350 lbf (433.03 kN)|
|Operator(s)||Union Pacific Railroad|
|Class||CSA-1, CSA-2, 4664-3, 4664-4, 4664-5|
The Union Pacific Challengers were a type of simple articulated 4-6-6-4 steam locomotive built by American Locomotive Company for the Union Pacific Railroad. 105 of these locomotives were built between 1936 and 1943. The Challengers were nearly 122 feet long and weighed more than one million pounds[clarification needed]. They operated over most of the Union Pacific system, primarily in freight service, but a few were assigned to passenger trains operating through mountain territory to California and Oregon. The locomotives were built specifically for Union Pacific and much of the experience gained later went into the design of the "Big Boy".
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 105 were divided into five orders, which can be put into two groups: the first two orders of "light" Challengers, and the final three of "heavy" Challengers.
|Class||Quantity||Manufacturer||Serial Nos.||Year||UP No.||Notes|
|CSA-1||15||American Locomotive Company||68745–68759||1936||3900–3914||Converted to oil fuel in 1941–43; renumbered 3800–3814 in 1944|
|CSA-2||25||American Locomotive Company||68924–68948||1937||3915–3939||Converted to oil fuel; renumbered 3815–3839 in 1944|
|4664-3||20||American Locomotive Company||69760–69779||1942||3950–3969|
|4664-4||31||American Locomotive Company||70158–70162
|1943||3975–3999||31 built but only 25 delivered to UP (see below); 3975–3984 converted to oil fuel in 1945; renumbered 3708–3717 in 1952|
|4664-5||20||American Locomotive Company||72792–72811||1944||3930–3949||3930/31/32/34/37/38/43/44 converted to oil fuel in 1952 and renumbered 3700–3707.|
As part of Union Pacific's fourth order in 1943, ALCO built 31 locomotives for Union Pacific using the same specifications. However, the War Production Board diverted 6 locomotives after completion to the Denver & Rio Grande Western Railroad via a lease through the War Department's Defense Plant Corporation. Locomotives 3900-3905 formed the Rio Grande's Class L-97. These were later sold to Clinchfield Railroad in 1947, becoming 670-675.
- Union Pacific Steam Shop Information on locomotives and excursion schedules.
- UP 3985 Challenger, Steam Locomotive - photos and additional information
- Union Pacific locomotive classes Information on the Challenger and other Union Pacific locomotives
- Kalmbach, A.C., ed. (August 1944). "Almost Identical Twins". Trains Magazine 4: 29.