The Sacramento division of the Southern Pacific had close to 150 miles
of grades of up to 2.5%. On this Roseville - Sparks line over the Sierra
Nevada there were also almost 30 miles of snow sheds and tunnels. Over the
years, as trains grew in length, more powerful locomotives were required.
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.
The second problem was easily handled by installing
"stack splitters" (a deflector located above the smoke stack which directed
the exhaust to the sides), as shown at the top of the image on the right.
The first problem required more consideration.
- The great volume of exhaust gasses almost asphyxiated the crew.
- The stack exhaust velocity was so great that it blew the roof boards off
of the snow sheds.
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.