Electric locomotives 3,355 hp heavy-freight electric loco of 1933 There were initially few electric locomotives with this wheel arrangement, as they are usually lighter than diesel-electrics of similar power and so could manage a similar axle loading with a simpler Bo-Bo arrangement. Some of the few early examples were the French
CC 7100 of 1949 and the
British Railways EM2 of 1953. 25 kV electric As high-speed electric locomotives in the 1980s began to achieve powers in the 6,000 hp range, new Co-Co designs appeared, as more axles were needed to distribute this high power. The
BR class 92 was a predominantly freight locomotive of this arrangement for the
Channel Tunnel, although the passenger
Eurotunnel Class 9 instead use a
Bo-Bo-Bo arrangement. This provides the same number of axles for traction, although with shorter bogie wheelbases and so gives a smoother ride.
C-C In C-C (Commonwealth) or C′C′ (UIC) arrangements, the axles of each bogie are coupled together. This may be for either a
diesel-hydraulic transmission with a mechanical
drive shaft to the bogie and
final drives to each axle. Otherwise a
monomotor bogie with a single traction motor. These are used for both electrics and diesel-electrics.
Co+Co of 1947, showing the Co+Co arrangement of the bogies with the drawgear below the body frame Co+Co is the code for a similar wheel arrangement but with an articulated connection between the bogies. The buffer and
drawbar forces are taken between the bogies rather than through the frame. These were mostly popular in South Africa.
1Co-Co1 1Co-Co1 The 1Co-Co1 wheel arrangement is an alternative to the Co-Co arrangement which has been used where it was desired to reduce axle load. Each 'Co' bogie has an additional non-powered axle in an integral
pony truck to spread the load. As the pony truck is articulated within the bogie, the arrangement is (1′Co)(Co1′) in
UIC notation. This rare arrangement was used primarily in Britain with the development of the
Bollen bogie; on the
Southern Railways' first three prototype mainline diesel-electric designs,
10201–10203, and then on production vehicles in British Rail's
Class 40 and "Peaks" (BR classes
44,
45, and
46).
1Co+Co1 in 1938
1Co+Co1, like Co+Co, is an articulated variant where the drawbar forces are taken between the bogies rather than through the frame. These were used in South Africa, for lighter loadings on the lightly laid . A number of Japanese electrics from the 1930s, also on Cape gauge, such as the
EF10 also used this arrangement.
2Co-Co2 The
New Zealand DF class were built in the mid-1950s by English Electric in Britain, as the first diesels for the
New Zealand railways. They were derived from the earlier English Electric 1Co-Co1 bogie design, but to provide increased flexibility for the long wheelbase bogie they used a four-wheeled bogie with more side play, rather than a pony truck. ==See also==