In Whyte notation, a 4-6-6-4 is a railroad steam locomotive that has four leading wheels followed by six coupled driving wheels, a second set of six driving wheels and four trailing wheels. The equivalent UIC classification is (2'C)C2'. This wheel arrangement was used by the Challenger class of locomotives on the Union Pacific Railroad. One locomotive of this class, Union Pacific 3985 is still operable, and it is currently the largest operable steam locomotive in the world. Another example, Union Pacific 3977 is on static display in North Platte, Nebraska. Though originally intended for freight service, many units could be found leading passenger consists as well. Railroads that used the Challenger type locomotive include:
| Railroad | Quantity, Builder |
|---|---|
| Carolina, Clinchfield & Ohio | 12 ALCO, 6 from D&RGW |
| Delaware and Hudson | 40 ALCO |
| Denver and Rio Grande Western | 6 ALCO, 15 Baldwin |
| Great Northern | 2 from SP&S |
| Northern Pacific | 47 ALCO |
| Spokane, Portland & Seattle | 8 ALCO |
| Union Pacific | 105 ALCO |
| Western Maryland | 12 Baldwin |
| Western Pacific | 7 ALCO |
External links
- The Challenger Type Locomotive
- The Union Pacific Challenger Roster
- Web Site of ToyTrains1 4-6-6-4 Challenger Steam Locomotives
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| Single engine types | 0-2-2 • 2-2-0 • 2-2-2 • 2-2-4 • 4-2-0 • 4-2-2 • 4-2-4 • 6-2-0 0-4-0 • 0-4-2 • 0-4-4 • 2-4-0 • 2-4-2 • 2-4-4 • 4-4-0 • 4-4-2 • 4-4-4 0-6-0 • 0-6-2 • 0-6-4 • 2-6-0 • 2-6-2 • 2-6-4 • 2-6-6 • 4-6-0 • 4-6-2 • 4-6-4 0-8-0 • 0-8-2 • 0-8-4 • 2-8-0 • 2-8-2 • 2-8-4 • 2-8-6 • 4-8-0 • 4-8-2 • 4-8-4 • 4-8-6 • 6-8-6 0-10-0 • 0-10-2 • 2-10-0 • 2-10-2 • 2-10-4 • 4-10-0 • 4-10-2 0-12-0 • 2-12-0 • 2-12-2 • 2-12-4 • 4-12-2 • 4-14-4 |
| Duplex engine types | 4-4-4-4 • 6-4-4-6 • 4-4-6-4 • 4-6-4-4 |
| Garratt (articulated) types | 0-4-0+0-4-0 • 2-6-0+0-6-2 • 4-6-2+2-6-4 • 2-8-0+0-8-2 • 4-8-2+2-8-4 • 4-8-4+4-8-4 |
| Mallet (articulated) types | 0-4-4-0 • 0-4-4-2 • 2-4-4-2 0-6-6-0 • 2-6-6-0 • 2-6-6-2 • 2-6-6-4 • 2-6-6-6 • 2-6-8-0 • 4-6-6-2 • 4-6-6-4 0-8-8-0 • 2-8-8-0 • 2-8-8-2 • 2-8-8-4 • 4-8-8-2 • 4-8-8-4 2-10-10-2 • 2-8-8-8-2 • 2-8-8-8-4 |
