Union Pacific “Big Boy” and Southern Pacific “Cab Forwards” (with Video )

Cab Forwards


 The best known example of the cab-forward design in the United States, the Southern Pacific Cab-Forward (also known as “Cab-in-fronts”) placed the cab at the front by the simple expedient of turning the entire locomotive, minus the tender, by 180 degrees, an arrangement made possible by burning fuel oil instead of coal.


The cab forward design was widely used by the Southern Pacific Railroad, which developed it to deal with the peculiar problems of its routes. The 39 long tunnels and nearly 40 miles (64 km) of snow sheds of the Sierra Nevada Mountains could funnel dangerous exhaust fumes back into the crew compartment of a conventional locomotive. After a number of crews nearly asphyxiated, someone had the idea of running his locomotive in reverse. This meant that the tender was leading the train, which introduced new problems. The tender blocked the view ahead and put crewmen on the wrong sides of the cab for seeing signals. The tenders were not designed to be pushed at the lead of the train, which limited speeds. Southern Pacific commissioned Baldwin Locomotive Works to build a prototype cab-forward locomotive, then ordered more before the prototype had even arrived.

All of the cab-forwards were oil-burning locomotives, which meant there was little trouble involved putting the tender at what would normally be the front of the locomotive. The oil and water tanks were pressurized so that both would flow normally even on uphill grades. Visibility from the cab was superb, such that one crewman could easily survey both sides of the track.

 Big Boy

Big Boy could generate a maximum of 6,290 drawbar horsepower. The Big Boys were the only locomotives to have the 4-8-8-4 wheel arrangement in the Whyte notation, combining two sets of eight driving wheels with both a four-wheel leading truck for stability entering curves and a four-wheel trailing truck to support the large firebox.

The Big Boys rendered important service in the Second World War, especially since they proved so easy to fire that even a novice could do a fair job. Since many new men who were unsuited to combat service or exempted were hired by the railroads to replace crewmen who had gone to war, this proved advantageous. During the war, after German agents filed reports that the Americans had giant steam engines that were moving huge trains full of vital war material over steep mountain grades at high speed, their reports were dismissed as “impossible”. Their performance in moving a huge volume of war material throughout WWII was repeatedly cited and the Big Boys are generally acclaimed as having made a huge contribution to the war effort

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About dummidumbwit

"I live in a trailer at the edge of town!" Neil Young=Revolution Blues
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12 Responses to Union Pacific “Big Boy” and Southern Pacific “Cab Forwards” (with Video )

  1. Pingback: » Longview, Texas Montessori-Based Dementia Programming

  2. Bodwyn Wook says:

    Howdy, ddw!

    I have been putting together a bunch of stuff in my ‘Trains, ‘Planes & “Getting There”‘ category, in Bodwyn Wook:


    Right now, the discussion (again!) is about the “most powerful ” steam locomotive. Which one was it?

    I am partial to ‘Allegheny’ 2-6-6-6s at this time, but also realise that the N & W 2-8-8-4 Y6b series had really tremendous TE — they just weren’t very fast….

  3. Bodwyn Wook says:

    Also, the PRR Q2 4-6-4-4 duplex steamer was way cool!

  4. Pingback: Hi-Ball UP Challenger No. 3985@70mph (watch the video) « Dummidumbwit’s Weblog

  5. Pingback: High Horsepower Locomotives « Dummidumbwit’s Weblog

  6. Joshua G. says:

    It would be a beautiful thing if one of these behemoths could be restored to active duty.

  7. John Pierce says:

    I remember as a kid, the DM&IR railroad used these to ship iron ore to the Duluth ore docks. I remember they would pull 150 empty ore cars from Proctor, MN and then pull 150 fulls back to the ore docks in Duluth. I lived next to a switch where the Mallet would turn around. My father worked in the iron or mines for 45 years. It was something to see this huge bemoth pulling those ore cars. Those were the days.

  8. Missabe says:

    In 1961 I had the pleasure of riding in the cab of Missabe Yellowstone #224 from Biwabeck to Two Harbors, about 17 miles as I recall. It was part of the tour out of Chgo called “Weekend on the Missabe”. Some of my 135 ore cars and several engines can be seen on the AMRE (division of TTM) website. A photo of mine made the front cover of Railroad magazine later.


  9. The first image here of a Cab Forward locomotive is an oil on canvas painting by me, Gary Symington. It’d be nice if you’re going to copy and paste my artwork from the web (likely Fine Art America?) that you at least give a credit line. Common courtesy, really. Thanks.

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