Southern Pacific Class AC-4

The Southern Pacific Railroad's AC-4 Class (meaning Articulated Consolidation) was the first class of cab forward 4-8-8-2 steam locomotives ordered by the Southern Pacific Railroad (SP). 10 of these engines were built by the Baldwin Locomotive Works between August and October 1928. They were numbered 4100-4109 and were placed into active service soon after construction. 
They were intended to improve on the railroad's previous MC (Mallet-Consolidation) class of 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. The success of these engines led to the construction and development of future SP AC class cab forward locomotives including the next batch of 16 engines known as the AC-5 Class which were nearly identical to the AC-4s with the exception of being just slightly larger.
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-4s were preserved.
==Stock list==
Image	Loco No.	Build date(s)	Builder 	Status
 	4100 	1928 	Baldwin Locomotive Works	Scrapped
 	4101 	1928 	Baldwin Locomotive Works	Scrapped
 	4102 	1928 	Baldwin Locomotive Works	Scrapped
 	4103 	1928 	Baldwin Locomotive Works	Scrapped
 	4104 	1928 	Baldwin Locomotive Works	Scrapped
 	4105 	1928 	Baldwin Locomotive Works	Scrapped
 	4106 	1928 	Baldwin Locomotive Works	Scrapped
 	4107 	1928 	Baldwin Locomotive Works	Scrapped
 	4108 	1928 	Baldwin Locomotive Works	Scrapped
 	4109 	1928 	Baldwin Locomotive Works	Scrapped
Category:Cab forward locomotives
Category:4-8-8-2 locomotives
Category:4-8-8-2 steam locomotives
Category:Scrapped locomotives
Category:Locomotives
Category:Unique locomotives
Category:Built in 1942
Category:Scrapped steam locomotives
Category:Cab forward steam locomotives
Category:Steam locomotives
Category:Tender locomotives
Category:American steam locomotives
Category:American locomotives
Category:Southern Pacific locomotives
Category:Standard gauge locomotives
Category:Standard gauge locomotives of the United States
Category:Baldwin locomotives
Category:Built in 1929
Category:Eight-coupled locomotives
Category:Articulated locomotives
Category:Built in 1928
Category:Mallet locomotives
Category:Articulated locomotives