4-6-6-4
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.
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.
| Steam locomotive types |
| 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, 4–6–0, 4–6–2, 4–6–4 |
| 0–8–0, 0–8–2, 2–8–0, 2–8–2, 2–8–4, 4–8–0, 4–8–2, 4–8–4, 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, 2–12–2, 4–12–2 |
| Duplex engine types |
| 4–4–4–4, 6–4–4–6, 4–4–6–4, 4–6–4–4 |
| Mallet (articulated) types |
| 0–4–4–0, 2–4–4–2 |
| 0–6–6–0, 2–6–6–2, 2–6–6–4, 2–6–6–6, 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 |
Categories: Rail stubs | Locomotives