Under the

Whyte notation Whyte notation is a classification method for steam locomotives, and some internal combustion locomotives and electric locomotives, by wheel arrangement. It was devised by Frederick Methvan Whyte, and came into use in the early twentieth cen ...

for the classification of steam locomotives, a 2-8-8-8-8-2 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, four sets of eight driving wheels, and two

trailing wheel On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle ( wheelset) located behind the driving wheels. The axle of the trailing wheels is usually located in a trailing truck. On some large locomotives, ...

s. Because of its length, such a locomotive must be an multiplex locomotive. It is longer than a normal

articulated locomotive An articulated locomotive is a steam locomotive (rarely, an electric locomotive) with one or more engine units that can move independent of the main frame. Articulation allows the operation of locomotives that would otherwise be too large to neg ...

; the fourth set of drivers is located under the tender. 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'', Cre ...

: 1-D-D-D-D-1 (also known as German classification and

Italian 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'', Cre ...

)
AAR classification: 1-D-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+040+041

Turkish classification In the Turkish classification system for railway locomotives, the number of powered axles are followed by the total number of axles. It is identical to the Swiss system except that the latter places a slash between the two numbers. Thus 0-6-0 beco ...

: 45+44+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+4/4+4/5 The equivalent

is to be refined to (1'D)DD(D1').

Usage

This type of articulated locomotive was never built, the only proposal for such a locomotive came from the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

. George R. Henderson was granted US Patent 1,100,563 for a quadruplex locomotive, in June 1914. The patent was assigned to the

Baldwin Locomotive Company The Baldwin Locomotive Works (BLW) was an American manufacturer of railroad locomotives from 1825 to 1951. Originally located in Philadelphia, it moved to nearby Eddystone, Pennsylvania, in the early 20th century. The company was for decades t ...

. Baldwin presented the design to the Atchison, Topeka, & Santa Fe Railway (AT&SF), which was a strong proponent of

compound locomotive A compound locomotive is a steam locomotive which is powered by a compound engine, a type of steam engine where steam is expanded in two or more stages. The locomotive was only one application of compounding. Two and three stages were used in shi ...

s in the 1910s.Solomon, Brian, 2015. ''The Majesty of Big Steam''. Voyageur Press. Drury, George H. (1993). ''Guide to North American Steam Locomotives''. Waukesha, Wisconsin: Kalmbach Publishing Company. This would have been, in 1913, by far the largest steam locomotive ever proposed. In quadruplex form, it would have been in overall length, total weight of about , with tractive effort of ."What Might Have Been", ''

Trains In rail transport, a train (from Old French , from Latin , "to pull, to draw") is a series of connected vehicles that run along a railway track and transport people or freight. Trains are typically pulled or pushed by locomotives (often know ...

'' August 1951 The Quadruplex was to comprise three

articulated An articulated vehicle is a vehicle which has a permanent or semi-permanent pivot joint in its construction, allowing it to turn more sharply. There are many kinds, from heavy equipment to buses, trams and trains. Steam locomotives were sometim ...

engines of 8 driving wheels each beneath the locomotive itself, and a fourth engine beneath the tender. As a

, engine cylinders 7 and 9 (as numbered on the above image) would receive high pressure steam to drive the first and third engines, each would exhaust as low-pressure steam to power cylinders 8 and 10 on the second and fourth engines. Both sets of low-pressure cylinders would then exhaust direct to atmosphere through stacks 33 and 38. The drivers had a diameter of 60 in (1524 mm). Due mostly to its extreme length the design included a number of mostly untried innovations: *An

engineer Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the limit ...

’s cab (24) at the very front, as well as a

fireman A firefighter is a first responder and rescuer extensively trained in firefighting, primarily to extinguish hazardous fires that threaten life, property, and the environment as well as to rescue people and in some cases or jurisdictions also ...

’s cab (23) behind the

firebox Firebox may refer to: *Firebox (steam engine), the area where the fuel is burned in a steam engine *Firebox (architecture), the part of a fireplace where fuel is combusted *Firebox Records Firebox Records was a Finnish record label based in S ...

(17). Communication between the cabs was proposed as cable- or rod-operated signalling devices, similar to the

engine order telegraph An engine order telegraph or E.O.T., also referred to as a Chadburn, is a communications device used on a ship (or submarine) for the pilot on the bridge to order engineers in the engine room to power the vessel at a certain desired speed. C ...

used on steamships, and possibly a

voice pipe A speaking tube or voicepipe is a device based on two cones connected by an air pipe through which speech can be transmitted over an extended distance. Use of pipes was suggested by Francis Bacon in the ''New Atlantis'' (1672). The usage for tel ...

*A jointed boiler with a flexible coupling (16) allowing the boiler casing to flex laterally on track curves. Such an accordion joint was already in use on a 2-6-6-2 locomotive of the AT&SF. * Two separate boilers, served by the single firebox: The front boiler (21) to supply the front two engines, the rear boiler (20) to supply the rear two engines. Working pressure of the boiler would be 215 psi (15 bar). *A turbine-driven extractor fan (26) within 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 e ...

(25) was intended to maintain a constant draft through the flues of both boilers. This was because Henderson had calculated that a conventional

blast pipe The blastpipe is part of the exhaust system of a steam locomotive that discharges exhaust steam from the cylinders into the smokebox beneath the chimney in order to increase the draught through the fire. History The primacy of discovery of ...

using steam exhausted from the low-pressure cylinders would have been inadequate to provide a sufficient draft until the locomotive was in motion. By the time the patent was granted, the experience of the existing triplexes and jointed-boiler locomotives had shown the shortcomings of these designs, and the quadruplex did not proceed to construction.

References

{{Whyte types Articulated locomotives Steam locomotives of the United States