Locomotive – What does ‘Bo-Bo’ or ‘Co-Co’ mean?

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Locomotive – What does ‘Bo-Bo’ or ‘Co-Co’ mean?

June 20, 2019, 2:11 PM

Diesel and electric locos’ wheel arrangements are described using a system where the axles of a loco are counted, with powered axles being described using letters and the unpowered axles (if any) indicated by digits. A set of two independently powered axles on a bogie is indicated by ‘Bo’, and a set of three independently powered axles on a bogie is indicated by ‘Co’.

Hence, a loco with two bogies, each having two separately powered axles is classified ‘Bo-Bo’; with three such bogies it would be ‘Bo-Bo-Bo’; with two bogies each with three powered axles it would be ‘Co-Co’. Sometimes locos have some leading or trailing unpowered axles too, so for instance a loco with two bogies, each having three powered axles and one unpowered one is indicated ‘1-Co-Co-1’. The ‘o’ in the powered axle description is left off to indicate that the axles are not independent, but coupled mechanically – the same motor drives all axles in the bogie (‘B-B’ instead of ‘Bo-Bo’).

ये भी पढ़े – स्त्रीरोग: पीरियड से जुड़ी वो बीमारी जिसके बारे में खुद औरतों को नहीं पता होता

A single powered axle on a bogie is indicated by ‘A’ a set of 4 powered axles is indicated ‘D’ or ‘Do’; there don’t appear to be any locos in India using such arrangements, but outside India arrangements such as ‘A1A-A1A’, ‘1-D-1’, etc. have been used. A ‘+’’ may be used to separate trucks of articulated locos. Multiple unit locos are shown by parenthesizing the unit specifications and prefixing a number corresponding to the number of units, e.g., 2(1-D-1) for a 2-unit loco, each unit having one unpowered leading axle, one unpowered trailing axle, and a 4 coupled powered axles.

A primarily European variation is to use apostrophes to mark each bogie instead of using hyphens to separate them. So, “Co‘Co” is the same as “Co-Co”.

Source – IFRCA.org

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