PRR M1
Encyclopedia
M1 is a class of steam locomotive
of the Pennsylvania Railroad
(PRR). It was a class of heavy mixed-traffic locomotives of the 4-8-2
"Mountain" arrangement, which uses four pairs of driving wheels with a four-wheel guiding truck in front for stability at speed and a two-wheel trailing truck to support the large firebox needed for sustained power. Although built for both passenger and freight work, they spent most of their service lives hauling heavy high-speed freight trains. Many PRR men counted the M1 class locomotives as the best steam locomotives the railroad ever owned.
. It spent three years in intensive testing, including all kinds of main-line service as well as a session on the railroad's static locomotive test plant. Having received very favorable reports, a further 200 were ordered from commercial locomotive builders; 175 from the Baldwin Locomotive Works
and 25 from Lima Locomotive Works
. Breaking with the PRR tradition of random locomotive numbering, these were numbered in a solid block from #6800-#6999.
In 1930, a further 100 locomotives were ordered. These, classified as M1a, featured several improvements from the previous locomotives. Instead of separate cylinder block and smokebox saddle castings, the M1a featured a one-piece casting (first seen on the K5
Pacific) which included inside steam delivery pipes, instead of the outside, visible pipes of the M1. A Worthington feedwater heater
was installed, with a boxlike mixing chamber fitted behind the stack. Twin cross-compound air compressors were hung next to each other on the left hand side of the locomotives, instead of the single compressor of the M1. The M1a locomotives were fitted as standard with larger tenders than the previous locomotives.
The M1a locomotives in particular were intended for passenger as well as freight service, and some bore decorative gold-leaf lining on tender and cab sides, but they proved better suited to freight work, and extensive electrification
saw a surplus of K4s
locomotives available for passenger trains. While they were mostly used on freight, their dual service purpose entitled them to have smokebox mounted keystone shaped numberplates. Freight engines on the Pennsy had circular numberplates.
Like most PRR steam locomotives, the M1 and M1a featured the square-shouldered Belpaire firebox
. The square-topped section continued ahead of the firebox proper, revealing the presence of a combustion chamber
- an extended firebox, giving more room for complete combustion of burning gases. The standard M1/M1a boiler used a working pressure of 250 pound per square inches (1.72 MPa). 38 locomotives were later converted into class M1b; the differences were all in the boiler, those being the addition of firebox circulators—large tubes carrying water passing through the firebox space, increasing water circulation and heating area, and thus steam generation—and an increase in boiler pressure to 270 psi (1.86 MPa). The only externally visible difference was extra cleaning plugs in the firebox sides, for washing out the circulators. The M1b had greater tractive effort
, thanks to the greater pressure, and more power at speed, thanks to the increased steam-generating ability.
All were fitted with intermediate-size 72 inches (1.829 m) driving wheels, two 27 by 30 in (685.8 by 762 mm) cylinders, and cast-steel KW pattern trailing trucks, similar to those fitted to K4s
Pacifics. M1 and M1a tractive effort was 64550 pound-forces (287.1 kN) while that of the M1b was 69700 pound-forces (310 kN). The locomotive weight was 385000 pounds (174.6 t). PRR standard small steel cabs were used. A distinctive spotting feature was a large cross-mounted air tank at the front of the locomotive above the pilot
. There was a distinctive family resemblance with other PRR locomotives. After World War II
, the M1 locomotives underwent similar front-end changes to those made to the K4s, including sheet steel drop-coupler pilots, the moving of the headlight to the smokebox top in front of the stack, the moving of the steam-driven generator to the smokebox front for easier maintenance, and the addition of a wide step above the air tank to service the air compressor.
A wide variety of tenders
were fitted to M1 locomotives, of steadily increasing size. During later years, some hauled sixteen-wheel 210-F-75B tenders almost as long as the locomotives themselves. All were fitted with scoops to pick up water from track pan
s. On the rear tender decks, all were later fitted with "doghouses" to house the head-end brakeman on freight trains, giving him a view backward over the train and placing him out of the way of the engineer and fireman. Many had railing-like trainphone
antennas added during the 1940s.
As dieselization progressed, the M1 locomotives were assigned heavier trains, while the diesels were assigned the high-speed freight trains previously the M1s' preserve. Their final years of service saw them hauling heavier trains than ever. Many remained in service until the withdrawal of steam from the PRR in mid 1957.
One locomotive, M1b #6755, was saved from the scrapper's torch for the PRR's historical collection housed at Northumberland, Pennsylvania
. It is now in the possession of the Railroad Museum of Pennsylvania
. It was added to the National Register of Historic Places
in 1979 as Locomotive No. 6755
.
- The New York Central Railroad
's equivalent of the M1, a dual mode 4-8-2
"Mountain" 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...
of the Pennsylvania Railroad
Pennsylvania Railroad
The Pennsylvania Railroad was an American Class I railroad, founded in 1846. Commonly referred to as the "Pennsy", the PRR was headquartered in Philadelphia, Pennsylvania....
(PRR). It was a class of heavy mixed-traffic locomotives of the 4-8-2
4-8-2
Under the Whyte notation for the classification of steam locomotives, 4-8-2 represents the wheel arrangement of four leading wheels on two axles , eight powered and coupled driving wheels on four axles, and two trailing wheels on one axle...
"Mountain" arrangement, which uses four pairs of driving wheels with a four-wheel guiding truck in front for stability at speed and a two-wheel trailing truck to support the large firebox needed for sustained power. Although built for both passenger and freight work, they spent most of their service lives hauling heavy high-speed freight trains. Many PRR men counted the M1 class locomotives as the best steam locomotives the railroad ever owned.
History
A single prototype, #6699, was built in 1923 at the railroad's own Altoona WorksAltoona Works
Altoona Works is a large railroad industrial complex in Altoona, Pennsylvania. It was built by the Pennsylvania Railroad to supply the railroad with locomotives, railroad cars and related equipment. For many years it was the largest railroad shop complex in the world.-History:In 1849, PRR...
. It spent three years in intensive testing, including all kinds of main-line service as well as a session on the railroad's static locomotive test plant. Having received very favorable reports, a further 200 were ordered from commercial locomotive builders; 175 from the Baldwin Locomotive Works
Baldwin Locomotive Works
The Baldwin Locomotive Works was an American builder of railroad locomotives. It was located in Philadelphia, Pennsylvania, originally, and later in nearby Eddystone, Pennsylvania. Although the company was very successful as a producer of steam locomotives, its transition to the production of...
and 25 from Lima Locomotive Works
Lima Locomotive Works
Lima Locomotive Works was an American firm that manufactured railroad locomotives from the 1870s through the 1950s. The company took the most distinctive part of its name from its main shops location in Lima, Ohio. The shops were located between the Baltimore & Ohio's Cincinnati-Toledo main line...
. Breaking with the PRR tradition of random locomotive numbering, these were numbered in a solid block from #6800-#6999.
In 1930, a further 100 locomotives were ordered. These, classified as M1a, featured several improvements from the previous locomotives. Instead of separate cylinder block and smokebox saddle castings, the M1a featured a one-piece casting (first seen on the K5
PRR K5
The Pennsylvania Railroad's class K5 was an experimental 4-6-2 "Pacific" type, built in 1929 to see if a larger Pacific than the standard K4s was worthwhile. Two prototypes were built, #5698 at the PRR's own Altoona Works, and #5699 by the Baldwin Locomotive Works. Although classified identically,...
Pacific) which included inside steam delivery pipes, instead of the outside, visible pipes of the M1. A Worthington feedwater heater
Feedwater heater
A feedwater heater is a power plant component used to pre-heat water delivered to a steam generating boiler. Preheating the feedwater reduces the irreversibilities involved in steam generation and therefore improves the thermodynamic efficiency of the system...
was installed, with a boxlike mixing chamber fitted behind the stack. Twin cross-compound air compressors were hung next to each other on the left hand side of the locomotives, instead of the single compressor of the M1. The M1a locomotives were fitted as standard with larger tenders than the previous locomotives.
The M1a locomotives in particular were intended for passenger as well as freight service, and some bore decorative gold-leaf lining on tender and cab sides, but they proved better suited to freight work, and extensive electrification
Electrification
Electrification originally referred to the build out of the electrical generating and distribution systems which occurred in the United States, England and other countries from the mid 1880's until around 1940 and is in progress in developing countries. This also included the change over from line...
saw a surplus of K4s
PRR K4s
The Pennsylvania Railroad's K4s 4-6-2 "Pacific" was their premier passenger-hauling steam locomotive from 1914 through the end of steam on the PRR in 1957....
locomotives available for passenger trains. While they were mostly used on freight, their dual service purpose entitled them to have smokebox mounted keystone shaped numberplates. Freight engines on the Pennsy had circular numberplates.
Belpaire firebox
The Belpaire firebox is a type of firebox used on steam locomotives. It was invented by Alfred Belpaire of Belgium. It has a greater surface area at the top of the firebox, improving heat transfer and steam production...
. The square-topped section continued ahead of the firebox proper, revealing the presence of a combustion chamber
Combustion chamber
A combustion chamber is the part of an engine in which fuel is burned.-Internal combustion engine:The hot gases produced by the combustion occupy a far greater volume than the original fuel, thus creating an increase in pressure within the limited volume of the chamber...
- an extended firebox, giving more room for complete combustion of burning gases. The standard M1/M1a boiler used a working pressure of 250 pound per square inches (1.72 MPa). 38 locomotives were later converted into class M1b; the differences were all in the boiler, those being the addition of firebox circulators—large tubes carrying water passing through the firebox space, increasing water circulation and heating area, and thus steam generation—and an increase in boiler pressure to 270 psi (1.86 MPa). The only externally visible difference was extra cleaning plugs in the firebox sides, for washing out the circulators. The M1b had greater tractive effort
Tractive effort
As used in mechanical engineering, the term tractive force is the pulling or pushing force exerted by a vehicle on another vehicle or object. The term tractive effort is synonymous with tractive force, and is often used in railway engineering to describe the pulling or pushing capability of a...
, thanks to the greater pressure, and more power at speed, thanks to the increased steam-generating ability.
All were fitted with intermediate-size 72 inches (1.829 m) driving wheels, two 27 by 30 in (685.8 by 762 mm) cylinders, and cast-steel KW pattern trailing trucks, similar to those fitted to K4s
PRR K4s
The Pennsylvania Railroad's K4s 4-6-2 "Pacific" was their premier passenger-hauling steam locomotive from 1914 through the end of steam on the PRR in 1957....
Pacifics. M1 and M1a tractive effort was 64550 pound-forces (287.1 kN) while that of the M1b was 69700 pound-forces (310 kN). The locomotive weight was 385000 pounds (174.6 t). PRR standard small steel cabs were used. A distinctive spotting feature was a large cross-mounted air tank at the front of the locomotive above the pilot
Pilot (locomotive)
In railroading, the pilot is the device mounted at the front of a locomotive to deflect obstacles from the track that might otherwise derail the train. In some countries it is also called cowcatcher or cattle catcher....
. There was a distinctive family resemblance with other PRR locomotives. After World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, the M1 locomotives underwent similar front-end changes to those made to the K4s, including sheet steel drop-coupler pilots, the moving of the headlight to the smokebox top in front of the stack, the moving of the steam-driven generator to the smokebox front for easier maintenance, and the addition of a wide step above the air tank to service the air compressor.
A wide variety of tenders
Tender locomotive
A tender or coal-car is a special rail vehicle hauled by a steam locomotive containing the locomotive's fuel and water. Steam locomotives consume large quantities of water compared to the quantity of fuel, so tenders are necessary to keep the locomotive running over long distances. A locomotive...
were fitted to M1 locomotives, of steadily increasing size. During later years, some hauled sixteen-wheel 210-F-75B tenders almost as long as the locomotives themselves. All were fitted with scoops to pick up water from track pan
Track pan
A track pan or water trough is a device to enable a steam railway locomotive to replenish its water supply while in motion...
s. On the rear tender decks, all were later fitted with "doghouses" to house the head-end brakeman on freight trains, giving him a view backward over the train and placing him out of the way of the engineer and fireman. Many had railing-like trainphone
Trainphone
Trainphone was the Pennsylvania Railroad's system for voice communication between train crews on moving trains and with dispatchers, tower operators and similar. It was also used by the Kansas City Southern, and to some lesser extent on the Duluth, Missabe & Iron Range. It did not use radio, but...
antennas added during the 1940s.
As dieselization progressed, the M1 locomotives were assigned heavier trains, while the diesels were assigned the high-speed freight trains previously the M1s' preserve. Their final years of service saw them hauling heavier trains than ever. Many remained in service until the withdrawal of steam from the PRR in mid 1957.
One locomotive, M1b #6755, was saved from the scrapper's torch for the PRR's historical collection housed at Northumberland, Pennsylvania
Northumberland, Pennsylvania
Northumberland is a borough in Northumberland County, Pennsylvania, United States. The population was 3,714 at the 2000 census.-History:Northumberland was founded in 1772. The land that became Northumberland was purchased from the Iroquois in the first Treaty of Fort Stanwix in 1768, and the...
. It is now in the possession of the Railroad Museum of Pennsylvania
Railroad Museum of Pennsylvania
The Railroad Museum of Pennsylvania is a railroad museum in Strasburg, Lancaster County, Pennsylvania.The museum is located on the east side of Strasburg along Pennsylvania Route 741...
. It was added to the National Register of Historic Places
National Register of Historic Places
The National Register of Historic Places is the United States government's official list of districts, sites, buildings, structures, and objects deemed worthy of preservation...
in 1979 as Locomotive No. 6755
PRR 6755
Pennsylvania Railroad 6755 is a preserved 4-8-2 "Mountain" type steam locomotive. It is preserved at the Railroad Museum of Pennsylvania.-History:...
.
See also
NYC MohawkNYC Mohawk
The New York Central Railroad called the 4-8-2 type of steam locomotive the Mohawk type. It was known as the Mountain type on other roads, but the mighty New York Central didn't see the name to be fitting on its famous Water Level Route, so it instead picked the name of one of those rivers its...
- The New York Central Railroad
New York Central Railroad
The New York Central Railroad , known simply as the New York Central in its publicity, was a railroad operating in the Northeastern United States...
's equivalent of the M1, a dual mode 4-8-2
4-8-2
Under the Whyte notation for the classification of steam locomotives, 4-8-2 represents the wheel arrangement of four leading wheels on two axles , eight powered and coupled driving wheels on four axles, and two trailing wheels on one axle...
"Mountain" 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...
.