In 1908 the Southern Pacific ordered two 2-8-8-2 conventional mallets classified MC-1 (Mallet - Consolidation) numbered 4000 and 4001. On a trial run up the "Hill" two problems became immediately evident.
Shortly after delivery of the MC-1s, an enterprising engineer decided not put up with nearly being asphyxiated or exposing himself to the tremendous heat and noise. He had the engine turned, hooked the engine pilot to the front of the train, and backed his locomotive over the hill pulling the train behind. This alleviated the above problems but created others such as pushing the tender ahead of the engine and the engineer being on wrong side for the signals. Despite these problems, other engineers began following this example.
A team of Southern Pacific design engineers came up with a plan and designs for a mallet with the cab in front, classified MC-2. Southern Pacific had Baldwin build 15 without testing one! Numbered 4002-4016, they were delivered in February and March of 1910. The engineer's and fireman's controls were shifted to opposite sides of the cab so that when run "backwards" the crew was on the usual side of the track.
Since the firebox on these locomotive was located in the front (far from the tender), they were designed to burn oil. Oil was piped from the tender along the locomotive to the firebox. The oil bunker in the tender on these locomotives was made air-tight and was structurally braced. They were slightly pressurized with air from the main air reservoir to insure a constant oil flow to the burner in the fire box when to the locomotive when traveling upgrade.
After the MC-2s had proven themselves, 32 more, classified MC-4 and MC-6 (MC-3 and MC-5 were skipped) were ordered. Before it was all over, Southern Pacific ended up with a total of 256 Cab Forwards (all classes). these Cab Forwards came in several wheel arrangements including 2-8-8-2, 4-6-6-2, and 4-8-8-2.
Although the crews initially complained about concerns that if they hit a gasoline truck at a grade crossing they would be right on top of it when it exploded. Fortunately, in 46 years of running Cab Forwards, this never happened. This was partially because of the unobstructed view from the cab. The advantage in visibility was tremendous.
Cab Forwards were a distinct trademark of the Southern Pacific. They were
sometimes also called "Cab-in-fronts" or "Backup Mallies" (even though,
technically, only some of the first classes were true mallets). According to
the definitive book on Cab Forwards (Those Amazing Cab Forwards by
George Harlan), no other railroad in the world had locomotives like them.
However, a few other unique examples did exist.
|AC63||Articulated Consolidation, 63 inch drivers|
|24 24||Cylinder diameter (front and rear) in inches|
|32||Piston stroke in inches|
|475||Weight on drivers in thousands of pounds|
|SF||Superheated, Feedwater heater|
|No.||Class||F.M. Whyte||Gauge||Railroad Line||Location||Status||Builder Info||Notes|
|4294||AC-12||4-8-8-2||4'-8½"||SP||California State Railroad Museum, Sacramento, CA||display||Baldwin #70101, 1944|
|4219||AC-10||4-8-8-2||4'-8½"||SP||Oregon Rail Heritage Center, Portland, OR||operational||Baldwin #64310, 1942||Tender only. Used as aux tender behind 4449.|