Union Pacific Big Boy 4004

Union Pacific Big Boy 4004
electric train sets
Image by cliff1066™
A 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 were specifically designed to meet the need to pull a 3,600 short ton (3300 metric ton) freight train over the long 1.14% grade of the Wasatch Mountains in Utah and Wyoming.

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