UIC classification
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The UIC classification is a comprehensive system for describing the wheel arrangement of locomotives and also trams. It is the system generally used in much of the world, but it was not widely used in the United Kingdom, other than partially on the Southern Railway under chief engineer Oliver Bulleid, or in the United States; a simplified form (AAR wheel arrangement) is used in both countries 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.
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. For example a Pacific-class steam locomotive, denoted 4-6-2 in Whyte notation, has a UIC designation of 2-C-1. On some locomotives non-driving axles are mounted on steerable bogies; this is sometimes indicated via the use of apostrophes in UIC notation, as 2-C1'.
- Plus sign ("+")
- Indicates an articulated locomotive.
- Brackets
- 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)D-2 or (more commonly) 2-D+D-2 in UIC notation. Garratt-type locomotives are indicated by bracketing or placing plus signs between all individual units. Mechanically-separated permanently-coupled units are indicated using only a "+" (plus) sign.
- Lower-case "o"
- On many electric and diesel-electric locomotives, axles are individually driven by electric motors — this is indicated by suffixing the driving wheel letter with a lower-case "o".
- 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
- t: Tank locomotive
and sometimes followed by a number, indicating the number of cylinders in a steam locomotive.
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] A1-1A
"A1-1A" means there are two bogies or wheel assemblies under the unit. Each truck has one powered and one idler (non-driven) axle, the latter 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).
[edit] A1A-A1A
"A1A-A1A" means there are two bogies or wheel assemblies under the unit. Each bogie has one powered axle, one idler 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).
[edit] 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.
[edit] 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 idler axle, and one more powered axle. All powered axles are individually driven (i.e., via traction motors).
[edit] 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, where it is denoted as Bo'Bo'.
[edit] Bo+Bo
"Bo+Bo" means there are two bogies or wheel assemblies under the unit, either mounted to an articulated frame or set beneath two mechanically-separate permanently-coupled units. Each truck has two separately-driven, powered axles (i.e., via traction motors). This arrangement can also be found on some articulated trams, most notably the high floor "kurzgelenkwagens" on tramways in some parts of Europe, and the ADtranz low floor tram of the 1990s.
[edit] Bo-Bo-Bo
"Bo-Bo-Bo" means there are identical bogies or wheel assemblies under the unit. Each truck has two individually-driven powered axles (i.e., via traction motors). A simlar wheel arrangement, Bo'2'Bo can be found on six axle articulated trams with Jacobs bogies, the 2 denotes an unpowered two axle bogie.
[edit] Bo-Bo-Bo-Bo
"Bo-Bo-Bo-Bo" means there are identical bogies or wheel assemblies under the unit. Each truck has two individually-driven powered axles (i.e., via traction motors). A simlar wheel arrangement, Bo'2'Bo'Bo can be found on eight axle articulated trams with Jacobs bogies.
[edit] Bo-Bo+Bo-Bo
"Bo-Bo+Bo-Bo" means there are identical bogies or wheel assemblies under the unit. The bogies are arranged in pairs and are either mounted to an articulated frame or set beneath two mechanically-separate permanently-coupled units. Each truck has two individually-driven powered axles (i.e., via traction motors).
[edit] 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.
[edit] 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).
[edit] Co-Bo
"Co-Bo" means there are two bogies or wheel assemblies under the unit. Each truck has separately-driven, powered axles (i.e., via traction motors). The "Co" truck under one end of the unit has three powered axles, while the "Bo" truck under the other end has two powered axles.
[edit] Do-Do
"Do-Do" means there are two identical bogies, or wheel assemblies under the unit. Each truck has four separately-driven, powered axles (i.e., via traction motors).
[edit] 1-B-B-1
"1-B-B-1" means there is one leading idler (non-driven) axle, two center-mounted bogies with two powered axles each connected by driving rods or gears, followed one trailing idler axle.
[edit] 1-Bo+Do+Do+Bo+1
"1-Bo+Do+Do+Bo+1" means there is one leading idler (non-driven) axle, one bogie with two powered axles, and one bogie with four powered axles mounted to the leading end unit; a center unit that shares the four-axle bogie with the leading end unit, along with another four-axle bogie that is shared with the trailing end unit; and a trailing end unit with a wheel arrangement that mirrors that of the leading unit. This arrangement (or similar configurations) is typical of that found on permanently-coupled passenger trainsets.
[edit] 1-C-1
"1-C-1" means there is one leading idler (non-driven) axle, one center-mounted bogie with three powered axles connected by driving rods or gears, followed one trailing idler axle.
[edit] 1-Co-Co-1
"1-Co-Co-1" means there is one leading idler (non-driven) axle, two center-mounted bogies with three separately-driven, powered axles (i.e., via traction motors), followed one trailing idler axle.
[edit] 1-D
"1-D" means there is one leading idler (non-driven) axle followed by one bogie with four powered axles connected by driving rods or gears.
[edit] 1-D-1
"1-D-1" means there is one leading idler (non-driven) axle, one center-mounted bogie with four powered axles connected by driving rods or gears, followed by one trailing idler axle.
[edit] 1-Do-1
"1-Do-1" means there is one leading idler (non-driven) axle, one center-mounted bogie with four separately-driven, powered axles (i.e., via traction motors), followed by one trailing idler axle.
[edit] 1-E-1
"1-E-1" means there is one leading idler (non-driven) axle, one center-mounted bogie with five powered axles connected by driving rods or gears, followed by one trailing idler axle.
[edit] 2-B-B-2
"2-B-B-2" means there is one leading idler bogie with two non-driven axles, two center-mounted bogies with three powered axles each connected by driving rods or gears, followed by one trailing idler bogie with two non-driven axles.
[edit] 2-B+B-2
"2-B+B-2" means there is one leading idler bogie with two non-driven axles, two center-mounted bogies with three powered axles each connected by driving rods or gears, followed by one trailing idler bogie with two non-driven axles. The bogies are arranged in pairs and are either mounted to an articulated frame or set beneath two mechanically-separate, permanently-coupled units. Each truck has two separately-driven, powered axles (i.e., via traction motors).
[edit] 2-Bo-Bo-2
"2-Bo-Bo-2" means there is one leading idler bogie with two non-driven axles, two center-mounted bogies with three separately-driven, powered axles each (i.e., via traction motors), followed by one trailing idler bogie with two non-driven axles.
[edit] 2-C
"2-C" means there is one leading idler bogie with two non-driven axles, followed by one bogie with three powered axles connected by driving rods or gears.
[edit] 2-Co-1
"2-Co-1" means there is one leading idler bogie with two non-driven axles, once center-mounted bogie with three separately-driven, powered axles (i.e., via traction motors), followed by one trailing idler axle.
[edit] 2-Co-2
"2-Co-2" means there is one leading idler bogie with two non-driven axles, one center-mounted bogie with three separately-driven, powered axles (i.e., via traction motors), followed by one trailing idler bogie with two non-driven axles.
[edit] 2-D-1
"2-D-1" means there is one leading idler bogie with two non-driven axles, one center-mounted bogie with four powered axles connected by driving rods or gears, followed by one trailing idler axle.
[edit] 2-D-1+1-D-2
"2-D-1+1-D-2" means there is one leading idler bogie with two non-driven axles, two center-mounted bogies with three powered axles each connected by driving rods or gears, followed by one trailing idler axle, mounted to an articulated frame or permanently-coupled to another mechanically-separate unit with an identical assembly mounted in the reverse (mirror) position. The axles on each powered bogie are connected by driving rods or gears.
[edit] 2-Do-1
"2-Do-1" means there is one leading idler bogie with two non-driven axles, one center-mounted bogie with four separately-driven, powered axles (i.e., via traction motors), followed by one trailing idler axle.
[edit] 2-Do-2
"2-Do-2" means there is one leading idler bogie with two non-driven axles, one center-mounted bogie with four separately-driven, powered axles (i.e., via traction motors), followed by one trailing idler bogie with two non-driven axles.
[edit] 2-Do-Do-2
"2-Do-Do-2" means there is one leading idler bogie with two non-driven axles, two center-mounted bogies with four separately-driven, powered axles each (i.e., via traction motors), followed by one trailing idler bogie with two non-driven axles.
[edit] References
- Hollingsworth, Brian and Arthur F. Cook (1987). The Great Book of Trains. Portland House, New York, NY. ISBN 0-517-64515-7.
