Southern Pacific class AC-11

SP 4274 leading an excursion train out of Reno, Nevada, on December 1, 1957.

Type and origin
Power type	Steam
Builder	Baldwin Locomotive Works
Serial number	64677 – 64706
Build date	November 1942 – April 1943

Specifications
Configuration	4-8-8-2
Gauge	4 ft 8 ¹⁄₂ in (1,435 mm) standard gauge
Driver diameter	63 in (1,600 mm)
Adhesive weight	531,700 lb (241,200 kg; 241.2 t)
Loco weight	657,900 lb (298,400 kg; 298.4 t)
Boiler pressure	250 psi (1.7 MPa)
Feedwater heater	6SA Worthington
Cylinder size	24 in × 32 in (610 mm × 813 mm) (bore × stroke)

Performance figures
Tractive effort	124,300 lbf (553 kN)

Career
Operators	Southern Pacific Railroad
Class	AC-11
Numbers	4245 – 4274
First run	November 24, 1942
Retired	1954 – 1958
Disposition	all scrapped

Southern Pacific Railroad's AC-11 class of cab forward steam locomotives was the seventh class of 4-8-8-2 locomotives ordered by Southern Pacific (SP) from Baldwin Locomotive Works; SP was so pleased with the AC-10 class built a year earlier that the railroad began placing orders for AC-11s while the AC-10s were still being built and delivered. They were built between November 1942 and April 1943, closely resembling the AC-10s.

The first AC-11, number 4245, entered service on November 24, 1942, and the last, 4274, on May 9, 1943. SP used these locomotives for between 12 and 15 years, with the last retirements from this class occurring on September 24, 1958. Shortly after their retirement, the AC-11s were scrapped, with the last, number 4262, on August 27, 1959.

References

Diebert, Timothy S. and Strapac, Joseph A. (1987). Southern Pacific Company Steam Locomotive Conpendium. Shade Tree Books. ISBN 0-930742-12-5.

Cab forward steam locomotives of Southern Pacific Railroad

2-6-6-2	MM-2

4-6-6-2	AM-2

2-8-8-2	MC-1 MC-2 AC-1 MC-4 AC-2 MC-6 AC-3

4-8-8-2	AC-4 AC-5 AC-6 AC-7 AC-8 AC-10 AC-11 AC-12

Preserved	SP 4294 (AC-12)

Southern Pacific Railroad Articulated Consolidation Steam Locomotives

2-8-8-2	AC-1 AC-2 AC-3

2-8-8-4	AC-9

4-8-8-2	AC-4 AC-5 AC-6 AC-7 AC-8 AC-10 AC-11 AC-12

Preserved	SP 4294 (AC-12)

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