La locomotora de vapor mas grande del mundo funciona en los USA la BIG BOY 4014 de Union Pacific RRC

Big Boy was the name given to twenty-five Union Pacific Railroad Class 4000 4-8-8-4 articulated steam locomotives built between 1941 and 1944 by Alco. #coneduardoamador #bigboy4014 Locomotive number 4014 was reacquired by the Union Pacific in 2013 for restoration. The restoration was completed in early May 2019, and the locomotive has returned to service, taking the title from Challenger 3985 as the world's largest and most powerful operating locomotive. After the introduction of the first Challenger-type (4-6-6-4) locomotive in 1936, the Union Pacific Railroad needed a locomotive with greater horsepower and sustained tractive effort to eliminate the need for double traction and assist in operations on the grades of eastern Utah and western Wyoming. In collaboration with the American Locomotive Company, the Union Pacific design team, led by Otto Jabelmann, studied the original Challenger design, executed by A.H. Fetters. They found that by increasing the firebox size to 6 x 2.4 m (approximately 14.4 m²), lengthening the boiler, adding four driving wheels, and reducing their diameter from 1,753 mm to 1,727 mm, the desired locomotive was achievable. A Big Boy could generate more than 6,290 hp (4.7 MW). This is a conservative estimate because the 4000 series locomotives burned low-quality Wyoming coal. The Big Boys were the only locomotives to have the 4-8-8-4 wheel arrangement in Whyte notation, combining two sets of eight driving wheels, along with a four-wheel leading bogie for stability on curves and another four-wheel bogie to support the large firebox. The Big Boy locomotives were specifically designed to meet the need to haul 3,300-ton trains up the long, 1.14% grades of the Wasatch Mountains in Utah. Until then, auxiliary locomotives were required. Coupled and then uncoupled auxiliary locomotives slowed train movement. For a locomotive to be successful in this task, it had to be faster and more powerful than the 2-8-8-0 and 2-8-8-2 compound locomotives that the Union Pacific ("UP") had tested after World War I. To avoid locomotive changes, the new class had to be able to haul long trains at a sustained speed of 60 mph (97 km/h) once past the mountains. By the end of the 4000 series' service life (in the late 1950s), it was found that it could still haul more than its rated tonnage of 3,300 tons. The weight of the trains was increased to the point where they could haul 4,000 tons up the Wasatch Grade without assistance. The Big Boys were designed to be stable at 130 km/h and built with a wide margin of safety and reliability, as they were normally operated well below that speed in freight service. Optimal power was achieved at around 56 km/h, and optimal traction at 16 km/h. Few articulated locomotives of the time were capable of such speeds, such as the Union Pacific's Challenger 4-6-6-4. In many respects, the Big Boy could be considered a larger, heavier, and more powerful Challenger. In total, 25 Big Boys were built, in two batches of ten and one of five locomotives. All were coal-fired, with large fireboxes to burn the low-quality Wyoming coal from the railroad's own mines. One locomotive, No. 4005, was experimentally converted to burn fuel oil. Unlike the Challenger-type locomotives, this conversion was unsuccessful, and the locomotive was soon converted back to coal. The reason for this failure was the use of a single burner, which, in the Big Boy's large firebox, produced insufficient and uneven heat. It is unknown why multiple burners were not employed, although with dieselization at its peak after 1945, the company probably lost interest in further steam developments. The Big Boys provided important service in World War II, especially because they were easy to operate, and even novices could do a good job. Since many new men, who had been exempted from military service at the front, had been hired by the railway companies to replace the crews who had gone to war, this proved advantageous. Big Boy 4014 is the world's largest steam locomotive still in operation, as it can be seen on the Union Pacific Railroad tracks in the USA. Of the 25 largest locomotives built for the Union Pacific, only 4014 remains in service today. Although eight Big Boys are visible, only 4014 has been restored so that future generations can witness its thunderous power. With these repairs, it could remain in operation for another century. Big Boy is the world's largest operating steam locomotive, and it will remain so for a long time to come.