The reference for locomotives and railcars
Union Pacific FEF-1 to FEF-3
United States | 1938 | 45 produced
FEF-1 No. 817 before conversion to oil firing in 1946
FEF-1 No. 817 before conversion to oil firing in 1946
collection LaMar M. Kelley

When William Jeffer, President of the Union Pacific, got stuck on an incline with his train, the initial order for the FEF series came about. The class 7000 locomotive used at the time with a 4-8-2 wheel arrangement was to be given a more powerful successor for mixed service, which led to the 4-8-4 wheel arrangement. This wheel arrangement was already in use on other US railroad companies and led to the designation “Four-Eight-Four”.

The first 20 FEF-1 class locomotives were delivered by ALCO in 1938 and had 77 inch diameter coupled wheels. Rolling resistance was reduced with roller bearings on all axles and tapered connecting rods ensured that the moving masses were reduced. This allowed them to travel at speeds of 110 mph with ease and without compromising safety.

FEF-3 No. 8444 in July 1981 in Colorado between Denver and Sterling
FEF-3 No. 8444 in July 1981 in Colorado between Denver and Sterling
Roger Puta

The following year, 15 FEF-2s were delivered, now with 80 inch coupling wheels, larger cylinders and higher boiler pressure. They were now cleared for 120 mph. Another ten FEF-3 followed in 1944, since no diesel locomotives were available for passenger trains due to the war.

The FEF series locomotives are known to produce between 4,000 and 5,000 hp at the drawbar and often traveled long distances in excess of 100 mph. In 1946 all were converted to oil firing, with the tenders now holding 6,550 gallons of oil instead of 25 short tons of coal.

In recent years, the locomotives were mainly used for freight trains before being retired at the end of the 1950s. Number 844 was the only US steam locomotive that was never officially retired and has since been used for excursion trips without major interruptions. In the meantime, it carried the number 8444 and is the only one of four surviving machines that is roadworthy.

Axle config4-8-4 (Northern) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Length114 ft 2 5/8 in
Wheelbase49 ft 3 in50 ft 10 in
Fixed wheelbase21 ft 6 in22 ft
Service weight465,000 lbs478,640 lbs490,700 lbs
Adhesive weight270,000 lbs265,520 lbs270,300 lbs
Total weight849,350 lbs894,960 lbs912,250 lbs
Axle load67,500 lbs66,380 lbs67,575 lbs
Water capacity20,000 us gal23,500 us gal
Fuel capacity50,000 lbs (coal)
Power sourcesteam
Estimated power4,800 hp (3,579 kW)5,200 hp (3,878 kW)5,400 hp (4,027 kW)
Optimal speed56 mph52 mph54 mph
Top speed110 mph120 mph
Starting effort55,129 lbf63,750 lbf
Power Plant
Driver diameter77 in80 in
Boiler pressure260 psi300 psi
Expansion typesimple
Cylinderstwo, 24 1/2 x 32 intwo, 25 x 32 in
Grate area100.2 sq ft
Firebox area479 sq ft442 sq ft512 sq ft
Tube heating area4,118 sq ft3,971 sq ft3,782 sq ft
Evaporative heating area4,597 sq ft4,413 sq ft4,294 sq ft
Superheater area1,473 sq ft1,900 sq ft1,400 sq ft
Total heating area6,070 sq ft6,313 sq ft5,694 sq ft
Calculated Values
steam locomotive
last changed: 04/2023

We use cookies to save the following settings:

  • selected navigation structure
  • selected language
  • preferred units
  • spelling of railway company names

If you refuse the use of cookies, the settings will only be retained for the current session and will be reset to the default values the next time you visit the site.

Display of units

Here you can set the desired unit system for the technical data.

  • Metric: Lengths in meters, weights in tonnes, and volumes in cubic meters
  • Imperial (UK): Lengths in feet/inches, weights in long tons and volumes in imperial gallons
  • Imperial (US): Lengths in feet/inches, weights in pounds, and volumes in US gallons
  • Individual: Depends on the country of origin of each locomotive
Operator names

Here you can set the display of railway company names.

  • Short: Abbreviation or short form of the name
  • Standard: commonly used name, partially translated to German
  • Complete: full name in local language