Milwaukee Road class A
Encyclopedia
The Milwaukee Road class A comprised four (#1–#4) high-speed, streamlined
4-4-2
"Atlantic" type steam locomotive
s built by ALCO
in 1935-37 to haul the Milwaukee Road’s
Hiawatha
express passenger trains. They were among the last Atlantic types built in the United States, and certainly the largest and most powerful. The class were the first locomotives in the world built for daily operation at over 100 mph (44.7 m/s), and the first class built completely streamlined, bearing their casings their entire lives. Although partially supplanted by the larger F7
"Hudsons" from 1937, they remained in top-flight service until the end. Locomotive #3 was taken out of service in 1949 and cannibalised for spares to keep the other three running until 1951. None survive.
They proved highly successful, indeed exceeding design goals. Designed for keeping a 6½ hour schedule between Chicago
and the Minneapolis-St. Paul "Twin Cities", the class proved themselves capable of handling nine cars on a 6¼ hour schedule. The only change over the years, except bumps and dents in the casing, was the addition of a Mars Light
beneath the winged emblem on the nose in 1947.
When introduced, they hauled the fastest scheduled express trains in the world, with average speeds over the whole run, including stops, of greater than 80 mph (35.8 m/s). Regular running at 100 mph or greater was required to keep these schedules; the class A locomotives were designed to cruise at over 100 mph and be able to achieve 120 mph (53.6 m/s). A recorded run with a dynamometer car
behind the locomotive was made on May 15, 1935, by locomotive #2 between Milwaukee and New Lisbon, Wisconsin
. Over a 14-mile stretch the speed of 112.5 mph (50.3 m/s) was recorded. This was the fastest authenticated speed reached by a steam locomotive at the time, making #2 the rail speed record holder for steam and the first steam locomotive to top 110 mph (49.2 m/s). There are reports, without physical evidence or accurate records, that these locomotives could exceed 120 mph. Such speeds would have placed the class A in contention with the LNER Class A4
and German BR 05
for the crown of fastest steam locomotive until that time, but so far no records have been unearthed. The successor Milwaukee Road class F7
was even more powerful, with a claimed top speed of 125 mph (55.9 m/s).
The design was fairly conventional but unusual in some aspects. One major goal was reducing reciprocating mass, which could not be completely counterbalanced. This was the reason for the high boiler pressure of 300 psi (2.07 MPa), which enabled the use of smaller, lighter pistons. The main rods connected to the first pair of driven wheels rather than the (more conventional) second; again, this reduced the reciprocating mass. The large 84 inches (2.134 m) diameter driving wheel
s (80 inches (2.032 m) was the standard) reduced piston speed and made high speeds less taxing on the machinery. The streamlined casings were designed to open easily for servicing; the front end contained a pair of clamshell doors to access the smokebox
front.
Streamliner
A streamliner is a vehicle incorporating streamlining in a shape providing reduced air resistance. The term is applied to high-speed railway trainsets of the 1930s to 1950s, and to their successor "bullet trains". Less commonly, the term is applied to fully faired recumbent bicycles...
4-4-2
4-4-2 (locomotive)
Under the Whyte notation for the classification of steam locomotives, 4-4-2 represents the wheel arrangement of four leading wheels on two axles , four powered and coupled driving wheels on two axles, and two trailing wheels on one axle...
"Atlantic" type steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
s built by ALCO
American Locomotive Company
The American Locomotive Company, often shortened to ALCO or Alco , was a builder of railroad locomotives in the United States.-Early history:...
in 1935-37 to haul the Milwaukee Road’s
Chicago, Milwaukee, St. Paul and Pacific Railroad
The Milwaukee Road, officially the Chicago, Milwaukee, St. Paul and Pacific Railroad , was a Class I railroad that operated in the Midwest and Northwest of the United States from 1847 until its merger into the Soo Line Railroad on January 1, 1986. The company went through several official names...
Hiawatha
Hiawatha (passenger train)
The Hiawathas were named passenger trains operated by the Chicago, Milwaukee, St. Paul and Pacific Railroad , and traveled from Chicago to the Twin Cities in Minnesota. The original train takes its name from The Song of Hiawatha by Henry Wadsworth Longfellow...
express passenger trains. They were among the last Atlantic types built in the United States, and certainly the largest and most powerful. The class were the first locomotives in the world built for daily operation at over 100 mph (44.7 m/s), and the first class built completely streamlined, bearing their casings their entire lives. Although partially supplanted by the larger F7
Milwaukee Road class F7
The Milwaukee Road's class F7 comprised six high-speed, streamlined 4-6-4 "Baltic" or "Hudson" type steam locomotives built by ALCO in 1937–38 to haul the Milwaukee's Hiawatha express passenger trains...
"Hudsons" from 1937, they remained in top-flight service until the end. Locomotive #3 was taken out of service in 1949 and cannibalised for spares to keep the other three running until 1951. None survive.
History
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
and the Minneapolis-St. Paul "Twin Cities", the class proved themselves capable of handling nine cars on a 6¼ hour schedule. The only change over the years, except bumps and dents in the casing, was the addition of a Mars Light
Mars Light
Mars Lights are signal-safety lights used in the United States and built by Mars Signal Light Company for railroad locomotives and fire apparatus...
beneath the winged emblem on the nose in 1947.
When introduced, they hauled the fastest scheduled express trains in the world, with average speeds over the whole run, including stops, of greater than 80 mph (35.8 m/s). Regular running at 100 mph or greater was required to keep these schedules; the class A locomotives were designed to cruise at over 100 mph and be able to achieve 120 mph (53.6 m/s). A recorded run with a dynamometer car
Dynamometer car
A dynamometer car is a railroad maintenance of way car used for measuring various aspects of a locomotive's performance. Measurements include tractive effort , power, top speed, etc.-History:...
behind the locomotive was made on May 15, 1935, by locomotive #2 between Milwaukee and New Lisbon, Wisconsin
New Lisbon, Wisconsin
New Lisbon is a city in Juneau County, Wisconsin, United States. The population was 1,436 at the 2000 census.-Geography:New Lisbon is located at ....
. Over a 14-mile stretch the speed of 112.5 mph (50.3 m/s) was recorded. This was the fastest authenticated speed reached by a steam locomotive at the time, making #2 the rail speed record holder for steam and the first steam locomotive to top 110 mph (49.2 m/s). There are reports, without physical evidence or accurate records, that these locomotives could exceed 120 mph. Such speeds would have placed the class A in contention with the LNER Class A4
LNER Class A4
The Class A4 is a class of streamlined 4-6-2 steam locomotive, designed by Nigel Gresley for the London and North Eastern Railway in 1935. Their streamlined design gave them high-speed capability as well as making them instantly recognizable, and one of the class, 4468 Mallard, still claims the...
and German BR 05
DRG Class 05
The Deutsche Reichsbahn's Class 05 was a German class of three express passenger steam locomotives of 4-6-4 wheel arrangement in the Whyte notation, or 2'C2' in the UIC notation used in continental Europe...
for the crown of fastest steam locomotive until that time, but so far no records have been unearthed. The successor Milwaukee Road class F7
Milwaukee Road class F7
The Milwaukee Road's class F7 comprised six high-speed, streamlined 4-6-4 "Baltic" or "Hudson" type steam locomotives built by ALCO in 1937–38 to haul the Milwaukee's Hiawatha express passenger trains...
was even more powerful, with a claimed top speed of 125 mph (55.9 m/s).
The design was fairly conventional but unusual in some aspects. One major goal was reducing reciprocating mass, which could not be completely counterbalanced. This was the reason for the high boiler pressure of 300 psi (2.07 MPa), which enabled the use of smaller, lighter pistons. The main rods connected to the first pair of driven wheels rather than the (more conventional) second; again, this reduced the reciprocating mass. The large 84 inches (2.134 m) diameter driving wheel
Driving wheel
On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons...
s (80 inches (2.032 m) was the standard) reduced piston speed and made high speeds less taxing on the machinery. The streamlined casings were designed to open easily for servicing; the front end contained a pair of clamshell doors to access the smokebox
Smokebox
A smokebox is one of the major basic parts of a Steam locomotive exhaust system. Smoke and hot gases pass from the firebox through tubes where they pass heat to the surrounding water in the boiler. The smoke then enters the smokebox, and is exhausted to the atmosphere through the chimney .To assist...
front.