Southern Pacific class AC-4
Performance figures | |
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Tractive effort | 112,760 lbf (501.6 kN), 116,900 lbf (520 kN) rebuilt |
Career | |
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Operators | Southern Pacific Railroad |
Class | AC-4 |
Number in class | 10 |
Numbers | 4100 – 4109 |
First run | October 1928 |
Disposition | All scrapped |
Southern Pacific Railroad's AC-4 (meaning Articulated Consolidation) 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 (Mallet-Consolidation) class 2-8-8-2 locomotives with a larger firebox, hence, the four-wheel leading truck (instead of the two-wheel).
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 lbf (520 kN).
The AC-4s were removed from service starting in 1953, and all ten were scrapped by June 1955.
References
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
- Diebert, Timothy S. & Strapac, Joseph A. (1987). Southern Pacific Company Steam Locomotive Conpendium. Shade Tree Books. ISBN 0-930742-12-5.
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- SP 4269 (AC-12)
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