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Milwaukee Road class F7

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For other uses, see F7 (disambiguation).
Milwaukee Road class F7
A class F7 being moved out of the Alco factory
Type and origin
Power typeSteam
BuilderAmerican Locomotive Company
Serial number69064–69069
Build dateAugust to September 1938
Total produced6
Specifications
Configuration:
​
 • Whyte4-6-4
Gauge4 ft 8+1⁄2 in (1,435 mm) standard gauge
Leading dia.36 in (914 mm)
Driver dia.84 in (2,134 mm)
Trailing dia.38 and 44 in (965 and 1,118 mm)
WheelbaseLoco & tender: 89 ft 10 in (27.38 m)
Length100 ft 0 in (30.48 m)
Axle load72,250 lb (32,770 kilograms; 32.77 metric tons)
Adhesive weight216,000 lb (98,000 kilograms; 98 metric tons)
Loco weight415,000 lb (188,000 kilograms; 188 metric tons)
Total weight791,000 lb (359,000 kilograms; 359 metric tons) full
Fuel typeCoal
Fuel capacity50,000 lb (23,000 kilograms; 23 metric tons)
Water cap.20,000 US gal (75,700 L; 16,700 imp gal)
Firebox:​
 • Grate area96.5 sq ft (8.97 m2)
Boiler pressure300 lbf/in2 (2.07 MPa)
Heating surface4,166 sq ft (387.0 m2)
Superheater:
​
 • TypeType E
 • Heating area1,695 sq ft (157.5 m2)
CylindersTwo, outside
Cylinder size23+1⁄2 in × 30 in (597 mm × 762 mm)
Performance figures
Maximum speed120 mph (193 km/h)
Tractive effort50,294 lbf (223.72 kN)
Factor of adh.4.29
Career
OperatorsMilwaukee Road
Numbers100–105
RetiredNovember 1949 to August 1951
DispositionAll scrapped

The Milwaukee Road's class "F7" comprised six (#100–#105) high-speed, streamlined 4-6-4 "Baltic" (Hudson) type steam locomotives built by the American Locomotive Company (ALCO) in 1937–38 to haul the Milwaukee's Hiawatha express passenger trains. Following on from the success of the road's class "A" 4-4-2s, the F7s allowed the road to haul heavier trains on the popular Chicago–Twin Cities routes.

The F7s are major contenders for the fastest steam locomotives ever built, as they ran at over 100 miles per hour (160 km/h) daily. One run in January 1941 recorded by a reporter for Trains magazine saw 110 miles per hour (180 km/h) achieved twice—in the midst of a heavy snowstorm. Baron Gérard Vuillet, a French railroading expert, once recorded a run between Chicago and Milwaukee where the locomotive reached 125 mph (201 km/h) and sustained an average 120 mph (190 km/h) for 4.5 miles (7.2 km).[1] However, the British locomotive LNER Class A4 4468 Mallard is officially accepted to be the world's fastest, with a run recorded at 125.88 mph (202.58 km/h) but authenticated at 126 mph in 1938. The Mallard run was slightly downhill and the locomotive broke down at the end of the run.

The Milwaukee F7s are accepted as the fastest steam locomotives by a different measure—scheduled speed between stations. In 1939, shortly after they were introduced into passenger service, the Twin Cities Hiawatha schedule was modified such that the engines would need to run the 78.3 mi (126.0 km) between Portage and Sparta, Wisconsin in 58 minutes—a start-to-stop average of 81 mph (130 km/h).[1]

In the late 1940s, the Milwaukee F7s were modified to equip an additional Mars Light above the original single highlight to further enhance the safety of daily highspeed operation.

On July 27, 1950, F7 #102 was on a run between Chicago and Milwaukee on the "North Woods Hiawatha." 73 miles from Milwaukee, the right main crosshead froze in its guide. It immediately overheated, broke, and dropped from the guide while the train was traveling at an estimated speed between 90 and over 100 mph. Air brake lines were severed, putting the engine into emergency. The engine was severely damaged, broken drive gear tore up ties and roadbed, and debris (including the main rod) was found as far as 1400 feet west of Edgebrook Station. Information is conflicting on the number of injuries that resulted: Some report that two railroad employees were injured, while another report stated that as the locomotive passed by the Devon Avenue crossing an automobile driver was injured by flying debris. Whatever the case, no one was killed. The train stayed on the rails, and continued to over 10,560 feet from the station until coming to a complete stop.[2] The cause of the incident was later found to have been caused by the failure of a connection link between the valve gear's combination lever and a Nathan mechanical lubricator. In fact, both of the locomotive's crossheads had been running dry on lubrication, but the right one was the first to fail. After this incident, #102 never ran again, as the cost was not considered worth repairs.

The first one built, #100, was also the first withdrawn from service, on November 10, 1949; and the last one built #105 was the final one in service and was withdrawn August 10, 1951. None survive today, as the last one was scrapped in 1951.

Table of locomotives[3][4]
Milwaukee
Road No.		 Alco
serial No.		 Built Retired
100 69064 August 1938 November 1949
101 69065 August 1938 April 1951
102 69066 August 1938 August 1950
103 69067 August 1938 June 1951
104 69068 September 1938 June 1951
105 69069 September 1938 August 1951

See also

Notes

  1. ^ a b Scribbins 1970, p. 63.
  2. ^ Young, Jan (30 November 2017). Fashion in Steel: Streamlined Steam Locomotives in North America. Lulu.com. ISBN 9781387408610.
  3. ^ Edson 1977, p. 51.
  4. ^ Scribbins 1970, pp. 226–227.

References

Media related to Milwaukee Road class F7 at Wikimedia Commons

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