Cow-calf
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In North American railroading, a cow-calf (also cow and calf) locomotive is a set of switcher-type diesel locomotives. The set usually is a pair; some 3-unit sets (with two calves) were built, but this was rare. A cow is equipped with a driving cab; a calf is not. The two are coupled together (either with regular couplers or a semi-permanent drawbar) and are connected with MU cables and brake lines so that both locomotive units can be operated from a single cab.
Cows are analogous to A units and calves to B unit road locomotives. Unlike them, cow-calf sets were almost always permanently attached. Each unit in a cow-calf set was powered.
Most cow-calf sets were built between the 1930s and the 1950s. They were built by several different makers, although General Motors' Electro-Motive Division built far more than the others.
The cow-calf concept was adopted on Queensland 2ft gauge sugar cane railways with two locomotives being coupled permanently in multiple-unit mode with the cab of one removed. This was utilised by Isis Mill (1980-1993) and by Mackay Sugar (2005).
The concept was also used in the United Kingdom by British Rail to produce the unique Class 13 locomotives, composed of two Class 08 locomotives. British terminology is Master-and-Slave Unit.
Cow-calf locomotives can be distinguished from the sometimes very similar looking slug and slug mother sets by the fact that both cows and calves are independently powered, while slugs are engineless, and dependent on power from their "mother" units.
[edit] List of cow-calf models
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This list is incomplete; you can help by expanding it.
- EMD TR
- EMD TR1
- EMD TR2
- EMD TR3
- EMD TR4
- EMD TR5
- EMD TR6
- ALCO SSB-9
- Baldwin S-8
- British Rail Class 13
- Russian TGEM10
