ClassicTrainsMag.com 47On the Saturday after Thanksgiving 1955, Challenger 3940 leads a freight
west near Hillside, Wyo., about 18 miles east of Cheyenne. Union Pacific
owned 105 of the 252 4-6-6-4s built. Jim Ehernberger
FEF-3 No. 840, from UP’s last group of 4-8-4s, climbs the west side of Sherman
Hill with a troop train of heavyweight Pullmans near Hermosa, Wyo., on Sep-
tember 1, 1956. Built for coal, all FEFs were converted to oil in 1946. R. H. Kindig
Big Boy 4-8-8-4s, 20 of which were built by Alco in 1941. They starred in
UP publicity and movie-theater newsreels, and why not? Extrapolated
from the Challengers, the 4000s operated at the practical limit of boiler
pressure, 300 psi. They produced energy in a firebox 8 feet wide and
nearly 20 feet long, including the combustion chamber. All this power
was delivered to two sets of eight-coupled 68-inch drivers, putting
135,375 pounds of tractive force in the hands of the engineer. The last 5
of the giants arrived in 1944. The Big Boys more than fulfilled their mis-
sion, hauling unprecedented volumes of freight east out of Ogden, Utah.
And that brings us to the thoroughbreds of the UP fleet, the 45
members of the FEF (“four eight four”) class. These huge Northerns
were comparable to any on American rails — including Santa Fe’s
2900s. The first order of 20 FEF-1s arrived from Alco in 1937, boasting
77-inch drivers, a boiler pressure of 260 psi, and 63,611 pounds of trac-
tive force. They were upsized in subsequent orders, including 15 FEF-2s
in 1939 and 10 FEF-3s in 1944, all with 80-inch drivers and 300 psi of
boiler pressure but only a slight increase in tractive force. Designed in
the era of standard heavyweight cars, they ended up looking fine on the
point of streamliners — and troop trains and freights. The last and most
famous among them, 844, was never retired and continues to work in
UP’s heritage program [see page 86].