Steam Locomotive with a Tender.

Prototype information

The Union Pacific Railroad (UP) class 4000 known as the "Big Boy" is surely one of the most popular steam giants in America if not worldwide. These articulated locomotives with their 4-8-8-4 wheel arrangement had their origin in 1941 at ALCO from the continuation of the "Challenger" concept, extremely successful UP articulated steam locomotives with a 4-6-6-4 wheel arrangement. The conception of the "Big Boys" resulted from the usual requirements as with all the other American classes of large locomotives. Fewer locomotives were expected to pull heavier loads at higher speeds. The UP bought the 25 units for only one single route: From Cheyenne, Wyoming 830 kilometers / 519 miles westwards through the foothills of the Rocky Mountains over Sherman Hill to Ogden, Utah. Before the pass named after General William T. Sherman is a long grade of about 50 kilometers / 31 miles from Cheyenne with a maximum climb of 1.5 percent. In the opposite direction, the 105 kilometer / 66 mile long grade of 1.14 % through the Wasatch Range of the Rocky Mountains demands it tribute. The result was a gigantic machine with a service weight of 548 tons (including the tender). An attempt was made to reach an equal distribution of the weight with the 4-8-8-4 wheel arrangement that had not been built up to then. With a grate area of almost 14 square meters / 150.70 square feet and a superheating surface of 229 square meters / 2,464 square feet, the Big Boys had a continuous power rating of 6,290 horsepower at the couplers. Boiler performance of over 10,000 horsepower or 8,200 electrical horsepower was recorded. The assigned range of duties for the "Big Boys" was fast freight service. They were capable of pulling 4,000-ton trains over the mountain passes without help. The new locomotive had a design speed of 128 km/h or 80 mph that it reached with only 1.7 meter / 66-15/16" diameter driving wheels. This put it in the ranks of the fastest articulated steam locomotives. However, these units were not allowed to thunder through this part of the West at this speed in regular service. Locomotive engineers confirmed, however that the speedometer often showed more than the allowed 112 km/h / 70 mph when they were running late. According to the legend, these giants acquired the nickname "Big Boy" from a young worker who scribbled the name on the smoke box shortly before the locomotive was presented. Officials from ALCO and UP liked this so much that "Big Boy" was even used in the advertising for the locomotive. On average, these units consumed 47,200 liters or 12,469 gallons of water and 22 tons of coal per hour. Of course, a fireman would have been overwhelmed if he had had to feed one of these ravenous beasts with a shovel. A stoker moved coal from the tender to the locomotive by means of a screw in a pipe and sprayed it into the firebox with steam pressure. The fireman adjusted the distribution of the coal in the firebox by controlling the steam pressure. In the fall of 1945, the UP decided to equip a "Big Boy" with smoke deflectors as an experiment in order to keep the smoke out of the engineer and fireman's eyes. In the beginning of December 1945, the "Big Boy" with road number 4019 had smoke deflectors installed on it at the maintenance center in Green River, Wyoming. The tests were finished on January 20, 1946 and these "large ears" were removed again in Green River. The tests had shown that at lower speeds in freight service and with recently improved blowers, the smoke could be routed ever better over the engineer's cab and without smoke deflectors. The Big Boy era was definitively past in July of 1959 when the fires in all of the units were banked for good. The hope of many railroad fans to see road numbers 4003 and 4019 (stored in operational condition as reserve locomotives in 1960) thundering one more time over Sherman Hill sadly did not happen. At least eight of the steam locomotive giants were preserved but not in operational condition.