UPRR Big Boy early

UPRR Big Boy early

Union Pacific introduced the Challenger-type (4-6-6-4) locomotives in 1936 on its main line over the Wasatch Range between Green River, Wyoming and Ogden, Utah. For most of the route, the maximum grade is 0.82% in either direction, but the climb eastward from Ogden, Utah into the Wasatch Range reached 1.14%. Hauling a 3,600-short-ton (3,300 t; 3,200-long-ton) freight train demanded doubleheading and helper operations, and adding and removing helper engines slowed operations.

To eliminate the need for doubleheading and helper operations, Union Pacific decided to design a new locomotive. For such a locomotive to be worthwhile, it would have to be faster and more powerful than slower locomotives like earlier compound 2-8-8-0s that UP tried after World War I. To avoid locomotive changes, the new class would need to pull long trains at a sustained speed of 60 miles per hour (100 km/h) once past mountain grades. In fact, it was designed so that it could travel smoothly and safely at 80 miles per hour (130 km/h) — even though it was not intended to be used that fast.[2]

Led by mechanic Otto Jabelmann, the Union Pacific Railroad's design team worked with the American Locomotive Company to re-examine their Challenger locomotives. The team found that Union Pacific's goals could be achieved by enlarging its firebox to approximately 235 by 96 inches (5.97 m × 2.44 m) (about 155 sq ft or 14.4 m2), lengthening the boiler, adding four driving wheels and reducing the size of the driving wheels from 69 to 68 in (1,753 to 1,727 mm) on a new engine.

The Big Boys are articulated, like the Mallet locomotive design. They were built with a wide margin of reliability and safety, and normally operated well below 60 miles per hour (100 km/h) in freight service. Peak horsepower was reached at about 35 mph (56 km/h); optimal tractive effort, at about 10 mph (16 km/h).

Without the tender, the Big Boy has the longest engine body of any reciprocating steam locomotive.

UPRR Big Boy early
big boy art
thumbnailph.jpg 35.09KB
big boy main
big-boy.im 13.66MB
boiler.texture.txt 29 bytes
boiler.tga 12.00MB
cab.texture.txt 26 bytes
cab.tga 12.00MB
chall-roof-hatch.im 7.09KB
chall-roof-hatch.kin 488 bytes
chall-t-hatch1.im 24.22KB
chall-t-hatch1.kin 556 bytes
chall-t-hatch2.im 22.42KB
chall-t-hatch2.kin 576 bytes
chall-t-hatch3.im 22.42KB
chall-t-hatch3.kin 556 bytes
chall-windows-left.im 16.88KB
chall-windows-left.kin 3.18KB
chall-windows-right.im 19.51KB
chall-windows-right.kin 3.18KB
default.im 2.30KB
details.texture.txt 30 bytes
details.tga 12.00MB
digit_3.texture.txt 30 bytes
digit_3.tga 16.04KB
digit_4.texture.txt 30 bytes
digit_4.tga 16.04KB
digit_5.texture.txt 30 bytes
digit_5.tga 16.04KB
digit_6.texture.txt 30 bytes
digit_6.tga 16.04KB
pipe.tga 12.00MB
rear frame.tga 12.00MB
running-gear.tga 16.00MB
shadow.bmp 96.05KB
shadow1.tga 128.04KB
smoke lifter.tga 768.02KB
windows-windows.texture.txt 49 bytes
windows.tga 3.00MB
big boy shadow
chal shadow.im 447.91KB
big_boy_alpha_numbers
alphanumber_0.tga 16.04KB
alphanumber_1.tga 16.04KB
alphanumber_2.tga 16.04KB
alphanumber_3.tga 16.04KB
alphanumber_4.tga 16.04KB
alphanumber_5.tga 16.04KB
alphanumber_6.tga 16.04KB
alphanumber_7.tga 16.04KB
alphanumber_8.tga 16.04KB
alphanumber_9.tga 16.04KB
• config.txt 33.14KB
• lilbloco.gs 86 bytes
sound
compressor.wav 866.41KB
dynamo.wav 41.75KB
piston_stroke1.wav 80.92KB
piston_stroke2.wav 80.92KB
piston_stroke3.wav 80.92KB
piston_stroke4.wav 80.92KB