No. 4294 was the last of 20 Southern Pacific class AC-12 4-8-8-2 cab forward locomotives in a larger series of 256 Southern Pacific articulated cab forwards starting with class AC-1. Articulated locomotives are essentially two locomotives sharing fire box, boiler and crew. The front locomotive has its cranks quartered 90 degrees apart. The front and rear drive axles are free to roll out of phase with respect to each other. If unloaded, the locomotive has a vertical oscillation, near 50 mph, that can lift the tires above the rails.

Photographed by Bruce Macdonald, May 4, 1981.
Added to the photo archive by Bruce Macdonald, September 15, 2021.
Railroad: Southern Pacific.

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