American Locomotive Company
UP Challenger
Union Pacific 4664 Challenger
United States · 1936
Specification
| Class | Union Pacific 4664 Challenger |
|---|---|
| Nicknames | Challenger, 3985, 4-6-6-4 |
| Builder | American Locomotive Company |
| Year introduced | 1936 |
| Country built | United States |
| Region | United States |
| Operators | Union Pacific Railroad |
| Era | Golden-age steam |
| Motive power | Steam |
| Role | Mixed traffic |
| Whyte | 4-6-6-4 |
| UIC | (2′C)C2′ |
| Wheel arrangement | 4-6-6-4 |
| Gauge | 1,435 mm — standard gauge |
| Quantity built | 105 |
| Power | Simple articulated; late engines around 280 psi |
| Tractive effort | 97,350 lbf on the late CSA engines |
| Top speed | 113 km/h · 70 mph |
| Weight | About 634,500 lb engine for a late example |
| Length | About 122 ft engine and tender |
| Status | Preserved |