Under the

Whyte notation The 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 twenti ...

for the classification of

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 ...

s, 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 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 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 independently of the main frame. Articulation allows the operation of locomotives that would otherwise be too large to ...

; 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'', Cr ...

: 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'', Cr ...

)
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 bec ...

: 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 (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. George R. Henderson was granted US Patent 1,100,563 for a

quadruplex locomotive A multiplex locomotive is a steam locomotive that Divided drive (locomotive), divides the driving force on its wheels by using multiple pairs of cylinders to drive multiple driving wheel set groups. Such a locomotive will necessarily articulated lo ...

, in June 1914. The patent was assigned to the Baldwin Locomotive Company. 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 steam engine, 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 ...

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 A train (from Old French , from Latin">-4; we might wonder whether there's a point at which it's appropriate to talk of the beginnings of French, that is, when it wa ... , from Latin , "to pull, to draw") is a series of connected vehicles th ...

'' August 1951 The Quadruplex was to comprise three

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 ...

engines of 8

s 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 Invention, invent, design, build, maintain and test machines, complex systems, structures, gadgets and materials. They aim to fulfill functional objectives and requirements while ...

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

fireman A firefighter (or fire fighter or fireman) is a first responder trained in specific emergency response such as firefighting, primarily to control and extinguish fires and respond to emergencies such as hazardous material incidents, medical in ...

’s cab (23) behind the firebox (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 cone (geometry), cones connected by an air pipe through which Speech communication, speech can be transmitted over an extended distance. Use of pipes was suggested by Francis Bacon in the '' ...

*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 ...

(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 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 locomotive A jointed-boiler locomotive was a variant of the Mallet articulated locomotive, in which a flexible coupling was introduced midway along the length of the boiler casing, which allowed the boiler to bend laterally when the locomotive was on curved tr ...

s 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