1941 Big Boy Locomotive
edited by David Barth, 12 December 2009.
Courtesy The Forney Museum of Transportation at 4303 Brighton Blvd., Denver,
Colorado 80216. Photos were taken in 2001, during the move.
Twelve 4000-class 4-8-8-4 engines were built for the Union Pacific by the American Locomotive Company in Schenectady,
New York. The first Big Boy built was number 4000. It arrived in Council Bluffs, Iowa in route to Utah, on September 5,
1941.
The original order of fifteen engines, numbered 4000 through 4015, made in 1941, was increased by an order of five more,
numbered 4015 through 4019, in the same year.
These twenty engines were assigned to the Ogden-Green River district to operate on the eastbound Wasatch
mountains.
The final order of five engines, numbered 4020 to 4024, were built in 1944.
Big Boys were 132 feet in length from the front of the pilot (cowcatcher), to the end of the tender. They weighed
approximately 1.2 million pounds (600 tons). The tender carried 25,000 gallons of water and 26,000 tons of
coal.
Coal is fed into the engine by a stoker screw that moves coal from the bottom of the tender, through a tube beneath
the cab, into the firebox. Air jets, operated by the fireman, distribute the coal inside the firebox.
The numbers on the side of the cab below the number, 4005, are as follows:
4-8-8-4: Wheel configuration.
68: Diameter of the driving wheels, in inches.
23 3/4: Diameter of the pistons, in inches.
32: The distance that the pistons travel, in inches.
540: The weight, in thousands of pounds, on each of the driving wheels.
MB: The type of stoker.
The 4-8-8-4 designation of these engines indicates that they have four small pilot wheels in front, eight drive wheels,
eight more drive wheels, and four small wheels beneath the cab. Because the great length of the engine, it was
articulated between the first and second set of eight drivers to enable the engine to negotiate curves in the track.
However, some trackage had curves that were too sharp for these engines.
Locomotives were not rated in horsepower but in tractive effort derived by using a mathematical formula. However, in
1943 pulling power was calculated differently by using a dynamometer to determine brake horsepower. The Big Boys
developed almost 7,000 horsepower that gave it a top speed of 79 mph, but most freight was pulled at 35 to 45 mph.
During WWII, these trains carried freight, coal, and troops.
Big Boys were built to pull trains over the Continental Divide between Cheyenne, Wyoming and Ogden, Utah. Occasionally
Big Boys were seen in Denver and rarely in Nebraska, as far east as Kearney, especially during the great blizzard of
1949.
Engine 4005, on display at the Forney Museum of Transportation in Denver, Colorado, was retrofitted to burn oil, used
from 1946 to 1948 when a coal strike became a possibility. The engine was converted back to coal because oil can not
produce as much heat as coal, resulting in reduced power.
4005 was involved in an accident in 1953 when it rolled over a switch that was mistakenly set to curve from the straight
track. The engine rolled on its left side, killing the engineer and fireman. Even though the engine and tender were
repaired, signs of the wreck can still be seen in the wavy steel on the left side. It is thought by some that this engine
is in the best condition of any of the eight remaining Big Boys because of the complete restoration that was done
following the accident.
All Big Boy engines were in use until the fall of 1957. A few briefly pulled freight in July 1959. All Big Boys were
retired from service in 1961 and 1962. 4005 had run approximately one million miles before its retirement. It was the
last Big Boy to roll down Sherman Hill from Green River to Cheyenne, Wyoming where it was given a cosmetic makeover by
the Union Pacific Railroad before being donated to the Forney Museum in June 1970.
Restoration of a Big Boy back to running condition was estimated to be one to three million dollars in 1998. Other
considerations, besides the cost of refurbishing the engine, included allowable track weight restrictions, bridge weight
limits, switches, shop tracks, maintenance costs, etc.
Big Boy number 4023 was considered to be the most eligible engine to be brought back to operating condition, but that
project was never undertaken. In 1974 it was moved to Omaha. In 2005 it was moved again, this time to the John C.
Kenefick Park located on a steep hill in the Lauritzen Gardens overlooking highway Interstate 80.
The smaller Challenger Class, 3900 Class, is sometimes mistaken for a Big Boy. These engines pulled loads east of
Cheyenne through North Platte, Nebraska and into Council Bluffs. The Challenger engines were also articulated with
a wheel arrangement of 4-6-6-4.
