Southern Pacific class AC-4
| Southern Pacific class AC-4 | |
|---|---|
|
Southern Pacific 4100 and crew | |
| Type and origin | |
| Power type | Steam |
| Builder | Baldwin Locomotive Works |
| Serial number | 60575, 60576, 60623-60625, 60666-60669 |
| Build date | August–October 1928 |
| Specifications | |
| Configuration | 4-8-8-2 |
| Gauge | 4 ft 8 1⁄2 in (1,435 mm) |
| Driver diameter | 63 in (1,600 mm) |
| Weight on drivers | 475,200 lb (215.5 t) |
| Locomotive weight | 614,600 lb (278.8 t) |
| Boiler pressure | 235 psi (1.62 MPa) |
| Feedwater heater | 4¼-BL Worthington |
| Cylinder size | 24 in × 32 in (610 mm × 810 mm) (bore × stroke) |
| Performance figures | |
| Tractive effort | 112,760 lbf (501.6 kN), 116,900 lbf (520 kN) rebuilt |
| Career | |
| Operator(s) | Southern Pacific Railroad |
| Class | AC-4 |
| Number in class | 10 |
| Number(s) | 4100 – 4109 |
| First run | October 1928 |
| Disposition | scrapped |
Southern Pacific Railroad's AC-4 class of steam locomotives was the first class of 4-8-8-2 cab forward locomotives. They were intended to improve on the railroad's MC class 2-8-8-2 locomotives with a larger firebox.
The AC-4s were the first SP Mallets built for simple expansion. Baldwin Locomotive Works built them in August through October 1928 with a maximum cutoff of 70%, so tractive effort was rated at 112,760 lbf (501.6 kN); a few years later limited cutoff was dropped and calculated tractive effort increased to 116,000 lb.
The AC-4s were removed from service starting in 1953 and all ten were scrapped by June 1955.
References
- Diebert, Timothy S. and Strapac, Joseph A. (1987). Southern Pacific Company Steam Locomotive Conpendium. Shade Tree Books. ISBN 0-930742-12-5.
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