Class 4000 – The Big Boy in America. The double-heading of locomotives or the use of locomotives in pusher service was cost intensive and used a lot of crews. From the Forties on, the Union Pacific Railroad (UP) needed an extremely powerful freight locomotive especially for use on the grades of the Rocky Mountains in order to reduce to a minimum or even avoid using locomotives in situations as mentioned above. The new locomotives had to be capable of relatively high speeds so that long routes could be covered without changing locomotives. Otto Jabelmann, an experienced designer at American Locomotive Company (ALCO), developed a gigantic, articulated locomotive that entered the annals of railroad history as the "Big Boy" and that more than earned its nickname. Twenty-five units of this 40,500 mm / 132 foot 10-7/16 inch, 350.2 ton, 4,560 kilowatt / 6,115 horsepower, and 112 km/h / 70 mph fast 4-cylinder locomotive steamed through the wide expanses of the USA between 1941 and 1957. The Big Boys had a 4-8-8-4 wheel arrangement and the equally massive looking tender carried 24.5 tons of coal and 94.6 cubic meters / 24,991 gallons of water. The Big Boy show its strengths on the notorious grades in the Wastach Mountains or on Sherman Hill (1.14% and 1.55% maximum grade), and the locomotive fulfilled all of the expectations set for it. Six thousand ton freight trains were not rare in everyday operation and an experiment on level terrain showed that "Big Boy" was capable of pulling a 25,000 ton train on its own. Even on Sherman Hill this immense locomotive could still haul 3,600 tons on its own over this difficult route. With a full load the coal consumption was naturally also gigantic. A stoker automatically fed enough coal from the tender to the 14 square meter / 150.70 square foot grate in the firebox. No fireman would have been in a position to master this with pure muscle power. By the mid-Fifties, powerful diesel locomotives were gradually replacing the class 4000 steam locomotives, which has already become legendary in their "life times", so that it's not surprising that a total of 8 "Big Boys" , unfortunately not operational, have been preserved in museums to remind people of the great past for steam motive power in the USA.