Southern Pacific Class AC-5

Southern Pacific class AC-5
SP No. 4116
Technical specifications
Serial number(s)	60866–60869 60884–60889 60952–60957
Manufacturer(s)	Baldwin Locomotive Works
Build date	July–September 1929
Total produced	16
Classification	AC-5
Rail gauge	4 ft 8+1⁄2 in (1,435 mm) standard gauge
Boiler pressure	235 psi (1.62 MPa)
Bore stroke	24 in × 32 in (610 mm × 813 mm)
Fuel type	Oil
Performance figures
Tractive effort	116,900 lbf (520 kN)
Service information
Running numbers	4110–4125
Disposition details
Preserved	None were preserved
Disposition	All scrapped

The Southern Pacific Railroad's AC-5 Class (meaning Articulated Consolidation) was the second class of cab forward 4-8-8-2 steam locomotives ordered by the Southern Pacific Railroad (SP). 16 of these engines were built by the Baldwin Locomotive Works between July and September 1929. They were numbered 4110-4125 and were placed into active service soon after construction. The AC-5 class was only slightly larger than the previous AC-4 Class.

These oil-fired engines had three ostensible disadvantages—and one big advantage—over conventionally laid-out locomotives. The disadvantages were the crew's vulnerability in a collision, the need to keep a high water level in the long boiler to account for grades, and an occasional back blast from the firebox from flameout and sudden relight caused by the long distance from tender to grate. (The fuel was helped through the lines by an 5-lb overpressure in the cylindrical tender.) The great advantage was the reduction of smoke in the cab when travelling through the miles of tunnels and snow sheds between Roseville, California and Sparks, Nevada.

The class were removed from active service by 1953 and were all scrapped by 1955. None of the members of the AC-5s were preserved.

Stock list

Image	Loco No.	Build date(s)	Builder	Status
	4110	1929	Baldwin Locomotive Works	Scrapped February 3, 1953. The first 4-8-8-2 cab forward locomotive to be scrapped.
	4111	1929	Baldwin Locomotive Works	Scrapped
	4112	1929	Baldwin Locomotive Works	Scrapped
	4113	1929	Baldwin Locomotive Works	Scrapped
	4114	1929	Baldwin Locomotive Works	Scrapped
	4115	1929	Baldwin Locomotive Works	Scrapped
	4116	1929	Baldwin Locomotive Works	Scrapped
	4117	1929	Baldwin Locomotive Works	Scrapped
	4118	1929	Baldwin Locomotive Works	Scrapped
	4119	1929	Baldwin Locomotive Works	Scrapped
	4120	1929	Baldwin Locomotive Works	Scrapped
	4121	1929	Baldwin Locomotive Works	Scrapped
	4122	1929	Baldwin Locomotive Works	Scrapped
	4123	1929	Baldwin Locomotive Works	Scrapped
	4124	1929	Baldwin Locomotive Works	Scrapped
	4125	1929	Baldwin Locomotive Works	Scrapped

Gallery

Cab forward steam locomotives of the 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)