Question: Information: - 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 together with side rods (also known as coupling rods); normally one pair is directly driven by the main rod (or connecting rod) which is connected to the end of the piston rod; power is transmitted to the others through the side rods. - Under the Whyte notation for the classification of steam locomotives , a 2 - 8 - 8 - 8 - 4 has two leading wheels , three sets of eight driving wheels , and four trailing wheels . Other equivalent classifications are : UIC classification : 1DDD2 ( also known as German classification and Italian classification ) French classification : 140 +040 +042 Turkish classification : 45 +44 +46 Swiss classification : 4/5 +4/4 +4/6 The equivalent UIC classification is to be refined to ( 1 'D ) D ( D2 ' ) for these engines . Only one 2 - 8 - 8 - 8 - 4 was ever built , a Mallet - type for the Virginian Railway in 1916 . Built by Baldwin Locomotive Works , it became the only example of their class XA , so named due to the experimental nature of the locomotive . Like the same railroad 's large articulated electrics and the Erie Railroad 2 - 8 - 8 - 8 - 2s , it was nicknamed '' Triplex '' . An overview of Triplex engineering is given at Triplex ( locomotive ) . The XA was unable to sustain a speed greater than five miles an hour , since the six cylinders could easily consume more steam than the boiler could produce . The tender had a four - wheel truck at the rear to help guide the locomotive into curves when drifting back downhill after pushing a train over the hill . The XA was sent back to Baldwin in 1920 and was rebuilt as two locomotives , a 2 - 8 - 8 - 0 and a 2 - 8 - 2 . Unlike their progenitor which lasted only a few years in service , these two locomotives remained in service until 1953 . - 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, a booster engine was mounted on the trailing truck to provide extra tractive effort when starting a heavy train and at low speeds on gradients. - Frederick Methvan Whyte (March 2, 1865 1941) was a mechanical engineer of Dutch background who worked for the New York Central in the United States. He is most widely known as the person who developed Whyte notation to describe the different wheel arrangements of steam locomotives in 1900. - The Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte, and came into use in the early twentieth century following a December 1900 editorial in "American Engineer and Railroad Journal". The notation counts the number of leading wheels, then the number of driving wheels, and finally the number of trailing wheels, groups of numbers being separated by dashes. Other classification schemes, like UIC classification and the French, Turkish and Swiss systems for steam locomotives, count axles rather than wheels. - In rail transport, a wheel arrangement or wheel configuration is a system of classifying the way in which wheels are distributed under a locomotive. Several notations exist to describe the wheel assemblies of a locomotive by type, position, and connections, with the adopted notations varying by country. Within a given country, different notations may also be employed for different kinds of locomotives, such as steam, electric, and diesel powered. - A steam locomotive is a railway locomotive that produces its pulling power through a steam engine. These locomotives are fueled by burning combustible materialusually coal/coke, wood, or oilto produce steam in a boiler. The steam moves reciprocating pistons which are mechanically connected to the locomotive's main wheels (drivers). Both fuel and water supplies are carried with the locomotive, either on the locomotive itself or in wagons (tenders) pulled behind. The first steam locomotive, made by Richard Trevithick, first operated on 21 February 1804, three years after the road locomotive he made in 1801. The first practical steam locomotive was built in 1812-13 by John Blenkinsop. What entity does '2-8-8-8-4' has the relation 'subclass of' with?
Answer:
articulated locomotive