UIC classification
From Wikipedia, the free encyclopedia
The UIC classification[1] is a comprehensive system for describing the wheel arrangement of locomotives, multiple units and trams. It is the system generally used in much of the world. The UK uses a related system, but it was not widely used prior to nationalisation other than partially on the Southern Railway under chief engineer Oliver Bulleid. The United States use a simplified form (AAR wheel arrangement) for modern locomotives.
It is a more versatile system than Whyte notation, making fewer assumptions about locomotive layout. In the latter notation, some locomotives are impossible to classify; UIC classification handles them easily. The UIC classification is also much more suited to diesel and electric locomotives.
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[edit] Structure
Whereas the Whyte notation counts wheels, the UIC notation counts pairs of wheels (called "wheelsets" or informally "axles").
- Upper-case letters
- Designate a number of consecutive driving axles, starting at A for a single axle. C thus indicates three consecutive pairs of driving wheels.
- Numbers
- Designate consecutive non-driving axles, starting with 1 for a single axle.
- Lower-case "o"
- On many electric and diesel-electric locomotives, axles are individually driven by electric traction motors — this is indicated by suffixing the driving wheel letter with a lower-case "o".
- Prime sign " ′ "
- Indicates that the axles are mounted on a steerable bogie.
- Plus sign "+"
- Indicates that the locomotive or multiple unit consists of permanently coupled and mechanically separated individual vehicles.
- Brackets
- Can be used to group letters and numbers describing the same bogie. For example, (A1A) indicates a three axle bogie with the outer two axles driven. When brackets are used a prime is not needed to indicate a bogie. Mallet locomotives can be indicated by bracketing the front power unit — for example, the Union Pacific Big Boy — denoted 4-8-8-4 in Whyte notation, is designated (2′D)D2′ in UIC notation.
Garratt-type locomotives are indicated by bracketing or placing plus signs between all individual units.
- Other Suffixes
- The designation can also have additional suffixes, denoting other features of the locomotive:
- h: Superheated Steam (German: Heißdampf)
- n: Saturated Steam (German: Naßdampf)
- v: Compound (German: Verbund)
- Turb: Turbine
- number: number of cylinders
- t: Tank locomotive
- G: Freight train purpose (German: Güterzug - freight train). Also used to indicate shunting locomotives
- P: Passenger train purpose (German: Personenzug - passenger train)
- S: Fast train purpose (German: Schnellzug - fast train)
The most common wheel arrangements in modern locomotives are Bo′Bo′ or Co′Co′, while steam locomotives and other older units can have many different wheel arrangements.
[edit] Examples
- (A1A)(A1A)
- "(A1A)(A1A) " means there are two bogies or wheel assemblies under the unit. Each bogie has one powered axle, one idle axle, and one more powered axle, an arrangement intended to provide better load distribution and thereby reduce the wheel load on the track. All powered axles are individually driven (i.e., via traction motors).
- BB
- "BB" means that there are four powered axles all mounted in the locomotive's frame. They are driven in pairs; i.e. each pair of axles is connected by driving rods or gears. Compare with "D" below.
- B′B′
- "B′B′ " means there are two bogies or wheel assemblies under the unit. Each truck has two powered axles, connected by driving rods or gears. Three-quarters of all modern locomotives (as well as the power cars of self-propelled trains) are configured in either this or the "Bo′-Bo′" arrangement.
- Bo′(A1A)
- "Bo′(A1A) " means there are two trucks or wheel assemblies. The "Bo′" truck is under one end of the unit, and has two powered axles, while the "(A1A)" truck is under the other end of the unit, and has one powered axle, one idle axle, and one more powered axle. All powered axles are individually driven (i.e., via traction motors).
- Bo′Bo′
- "Bo′Bo′ " means there are two bogies or wheel assemblies under the unit. Each truck has two individually-driven powered axles (i.e., via traction motors). Three-quarters of all modern locomotives (as well as the power cars of self-propelled trains) are configured in either this or the "B′B′" arrangement. Many types of tram use this arrangement. See also: Bo-Bo.
- C′C′
- "C′C′ " means there are two bogies or wheel assemblies under the unit. Each truck has three powered axles, connected by driving rods or gears.
- Co′Co′
- "Co′Co′ " means there are two bogies or wheel assemblies under the unit. Each truck has three individually-driven, powered axles (i.e., via traction motors). See also: Co-Co.
- D
- "D" means that there are four powered axles, connected by driving rods or gears, all mounted in the locomotive's frame.
- 1′D1′
- "1′D1′ " means that there is one leading idle (non-driven) axle mounted in a bogie, four driven axles mounted in the frame and connected by driving rods or gears, followed one trailing idle axle mounted in a bogie.
- 2′D1′h3S
- Two front leading axles grouped in a bogie, four driving axles, one rear leading axle in a bogie, simple steam expansion, superheated steam, three-cylinder machine, fast train purpose.
- 1′E1′h2Gt
- One front leading axle in a bogie, five driving axles, 1 rear leading axle, simple steam expansion, superheated steam, two-cylinder machine, freight trains purpose, tank-engine.
- 1′Dn4vP
- One front leading axle in a bogie, four driving axles, saturated steam, four-cylinder machine, compound (double steam expansion), passenger train purpose
[edit] References
[edit] See also
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