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A triplex locomotive was a
steam locomotive A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, Fuel oil, oil or, rarely, Wood fuel, wood) to heat ...
that divided the driving force on its wheels by using three pairs of cylinders to drive three sets of
driving wheel On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons (or turbine, in the case of a steam turbine locomotive). On a conventional, non-articulated locomotive, the driving wheels are all coupled t ...
s. Any such locomotive will inevitably be
articulated An articulated vehicle is a vehicle which has a permanent or semi-permanent coupling in its construction. This coupling works as a large pivot joint, allowing it to bend and turn more sharply. There are many kinds, from heavy equipment to buse ...
. All triplex locomotives built were of the
Mallet A mallet is a tool used for imparting force on another object, often made of rubber or sometimes wood, that is smaller than a maul or beetle, and usually has a relatively large head. General overview The term is descriptive of the ...
type, but with an extra set of
driving wheels On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons (or turbine, in the case of a steam turbine locomotive). On a conventional, non-articulated locomotive, the driving wheels are all coupled tog ...
under the tender. The concept was extended to locomotives with four, five or six sets of drive wheels. However, these locomotives were never built, except for one quadruplex locomotive in
Belgium Belgium, officially the Kingdom of Belgium, is a country in Northwestern Europe. Situated in a coastal lowland region known as the Low Countries, it is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeas ...
.


Triplex classes

Baldwin Locomotive Works The Baldwin Locomotive Works (BLW) was an American manufacturer of railway locomotives from 1825 to 1951. Originally located in Philadelphia, Pennsylvania, it moved to nearby Eddystone, Pennsylvania, Eddystone in the early 20th century. The com ...
built three 2-8-8-8-2 triplex locomotives for the
Erie Railroad The Erie Railroad was a railroad that operated in the Northeastern United States, originally connecting Pavonia Terminal in Jersey City, New Jersey, with Lake Erie at Dunkirk, New York. The railroad expanded west to Chicago following its 1865 ...
between 1914 and 1916. A 2-8-8-8-2 has two
leading wheel The leading wheel or leading axle or pilot wheel of a steam locomotive is an unpowered wheel or axle located in front of the driving wheels. The axle or axles of the leading wheels are normally located on a leading truck. Leading wheels are used ...
s, three sets of eight
driving wheel On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons (or turbine, in the case of a steam turbine locomotive). On a conventional, non-articulated locomotive, the driving wheels are all coupled t ...
s, and two
trailing wheel On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle (Wheelset (rail transport), wheelset) located behind the driving wheels. The axle of the trailing wheels is usually located in a trailing Bogie, t ...
s. Because of its length, such a locomotive must be
articulated An articulated vehicle is a vehicle which has a permanent or semi-permanent coupling in its construction. This coupling works as a large pivot joint, allowing it to bend and turn more sharply. There are many kinds, from heavy equipment to buse ...
. It is not longer than a normal articulated; the third set of drivers is located under the tender. All of the examples produced were a Triplex of the
Mallet A mallet is a tool used for imparting force on another object, often made of rubber or sometimes wood, that is smaller than a maul or beetle, and usually has a relatively large head. General overview The term is descriptive of the ...
type. The first was named ''Matt H. Shay'', after a beloved employee of that road. These Triplexes were given the classification of P-1 and they could reportedly pull 650 freight cars. The triplexes were primarily used as pushers on grades requiring helper locomotives. Slow moving, the triplexes were not considered highly successful, and no more were built for Erie. The Erie Railroad scrapped their Triplexes from 1929, 1931, and 1933. Other equivalent classifications are: :
UIC classification The UIC classification of locomotive axle arrangements, sometimes known as the German classification''The Railway Data File''. Leicester: Silverdale, 2000. p. 52. . or German system,Kalla-Bishop P.M. & Greggio, Luciano, ''Steam Locomotives'', Cr ...
: (1'D)D(D1') : AAR classification: 1-D-D-D-1 :
French classification Under the French classification system for locomotive wheel arrangements, the system is slightly different for steam and electric/diesel vehicles. Steam The French system counts axles, rather than wheels. As with Whyte notation, a conventional r ...
: 140+040+041 : Turkish classification: 45+44+45 :
Swiss classification For more than a century, the Swiss locomotive, multiple unit, motor coach and railcar classification system, in either its original or updated forms, has been used to name and classify the rolling stock operated on the railways of Switzerland. ...
: 4/5+4/4+4/5 Another very similar designed triplex was built by Baldwin as a 2-8-8-8-4 for the
Virginian Railway The Virginian Railway was a Class I railroad located in Virginia and West Virginia in the United States. The VGN was created to transport high quality "smokeless" bituminous coal from southern West Virginia to port at Hampton Roads. History ...
, as No. 700, in 1916. This triplex was given classification of XA, so named due to the experimental nature of the locomotive. The 2-8-8-8-4 was considered unsuccessful because it only made a maximum speed of and had high maintenance costs. The XA was sent back to
Baldwin Locomotive Works The Baldwin Locomotive Works (BLW) was an American manufacturer of railway locomotives from 1825 to 1951. Originally located in Philadelphia, Pennsylvania, it moved to nearby Eddystone, Pennsylvania, Eddystone in the early 20th century. The com ...
where it was taken apart in 1920 and converted into a
2-8-8-0 In the Whyte notation for the classification of steam locomotives by wheel arrangement, a 2-8-8-0 is a locomotive with a two-wheel leading truck, two sets of eight driving wheels, and no trailing truck. Equivalent classifications Other equivalent ...
and a
2-8-2 Under the Whyte notation for the classification of steam locomotives, represents the wheel arrangement of two leading wheels on one axle, usually in a leading truck, eight powered and coupled driving wheels on four axles and two trailing wh ...
. These two engines were in service until 1953. Both of the two engines were scrapped.


Design

The triplex locomotives were of the Mallet type, but with an extra set of driving wheels under the tender. The centre set of cylinders received high-pressure steam. The exhaust from these was fed to the two other sets of cylinders. The right cylinder exhausted into the front set of low pressure cylinders, and the left into the rear set; this is also why the high pressure cylinders are the same diameter as the low pressure cylinders, making the engine a 2 to 1 compound, whereas most Mallet locomotives have much smaller high pressure cylinders. The front set exhausted through the
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 ...
and the rear set exhausted first through a
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 o ...
in the tender and then through a large pipe directly to the outside, as can be seen in the photo. As only half of the exhaust steam went through the blast pipe in the smokebox, the draft in the firebox and the heating of the boiler was poor. Although the boiler was large in comparison with contemporary two-cylinder and four-cylinder locomotives, six large cylinders required more steam than even such a boiler could supply. The Erie locomotives always operated in compound mode and did not have "intercepting" valves that would have put full pressure on all six cylinders, yet the triplexes produced huge amounts of
tractive effort In railway engineering, the term tractive effort describes the pulling or pushing capability of a locomotive. The published tractive force value for any vehicle may be theoretical—that is, calculated from known or implied mechanical proper ...
that may have been the highest of any steam locomotives ever. Westing gives a figure of in compound mode and seems to indicate that it was the largest tractive effort for any locomotives up to the mid-1910s. The
Union Pacific Big Boy The Union Pacific Big Boy is a type of simple articulated locomotive, articulated 4-8-8-4 steam locomotive manufactured by the American Locomotive Company (ALCO) between 1941 and 1944 and operated by the Union Pacific Railroad in revenue service ...
, built in the 1940s, did not exceed the tractive effort of the Erie locomotives either, as it had a tractive effort of only . The triplexes could also be considered the largest
tank locomotive A tank locomotive is a steam locomotive which carries its water in one or more on-board water tanks, instead of a more traditional tender (rail), tender. Most tank engines also have Fuel bunker, bunkers (or fuel tanks) to hold fuel; in a #Tender ...
s ever built, as the tender also had driving wheels and thus contributed to the traction. The problem of diminishing adhesion of the tender unit as water and coal was used; was ''not'' a significant factor or design flaw, as the rear engine as designed was not to produce as much adhesion than the front and middle engines, by adjusting the steam lap; which compensating for the usage of coal and water. Even nearly empty, the rear engine produced equivalent amount of tractive effort. Also, pusher locomotives had frequent opportunities to take on additional fuel and water as they were not not "line haul" assignments. Coaling facilities were close at Susquehanna, and Port Jervis.


Usage

In all, only four triplex locomotives were built, and only in the United States. Because the
tractive effort In railway engineering, the term tractive effort describes the pulling or pushing capability of a locomotive. The published tractive force value for any vehicle may be theoretical—that is, calculated from known or implied mechanical proper ...
of the locomotives was so great that the couplings and frames of the cars could not withstand it, the triplex locomotives could only be used to
bank A bank is a financial institution that accepts Deposit account, deposits from the public and creates a demand deposit while simultaneously making loans. Lending activities can be directly performed by the bank or indirectly through capital m ...
heavy trains up steep grades. Even with their huge boilers, the Erie locomotives could only produce enough steam to run at , the Virginian only . The reason for this was the poor performance of the boilers due to the lack of exhaust draught from the driving wheelset under the tender. The Erie locomotives were used as helpers on the Susquehanna Hill also known as the Gulf Summit, near
Deposit, New York Deposit is a Administrative divisions of New York#Town, town in Delaware County, New York, Delaware County, New York (state), New York, United States. As of the 2020 census, the town's population was 1,427.United States Census Bureau, 2020 U.S. ...
, on the
Southern Tier Line The Southern Tier Line is a railroad line owned and operated by the Norfolk Southern Railway in the U.S. states of New York and Pennsylvania. The line was built by the Erie Railroad and its predecessors and runs from Buffalo, New York, to Suff ...
. After 13 years they were replaced by 2-10-2s and retired. All Erie triplex locomotives had been scrapped by 1930, and none have survived. The Virginian XA #700 2-8-8-8-4 was unsuccessful. It was returned to Baldwin, where it was rebuilt into a Class MD
2-8-2 Under the Whyte notation for the classification of steam locomotives, represents the wheel arrangement of two leading wheels on one axle, usually in a leading truck, eight powered and coupled driving wheels on four axles and two trailing wh ...
, numbered 410, and a Class AF
2-8-8-0 In the Whyte notation for the classification of steam locomotives by wheel arrangement, a 2-8-8-0 is a locomotive with a two-wheel leading truck, two sets of eight driving wheels, and no trailing truck. Equivalent classifications Other equivalent ...
, numbered 610. A two-wheel trailing truck was later added, making it into a
2-8-8-2 A 2-8-8-2, in the Whyte notation for describing steam locomotive wheel arrangements, is an articulated locomotive with a two-wheel leading truck, two sets of eight driving wheels, and a two-wheel trailing truck. The equivalent UIC classification ...
. These two locomotives were operated until 1953.


References


Patent

*


External links

* Site about commercial model train triplex locomotives {{Whyte types Steam locomotive types 2-8-8-8-2 locomotives 2-8-8-8-4 locomotives Scrapped locomotives