Cow–calf

In rail transport, a cow–calf (also cow and calf, or in the UK master and slave) is a set of diesel switcher locomotives.

The two are coupled together (either with regular couplers or a semi-permanent drawbar) and equipped with multiple unit train control so that both locomotives can be operated from the single cab.

Like the early EMD FT locomotives, cow–calf sets were typically built as mated pairs, with the cow and calf sharing a number.

Cow–calf sets were made obsolete by the development of road switcher locomotives, which could handle both mainline trains and switching duties.

[3] The Belt Railway of Chicago was the final holdout, continuing to operate TR2 and TR4 sets into the 1980s and 1990s.

[5][3] EMD's TR (transfer) series were the largest group of cow–calf locomotives built.

Three sets were created by British Rail in 1965 by permanently coupling pairs of Class 08 0-6-0DE locomotives dating from 1959 and 1962, the cabs and controls being removed from the calves.

Four 0-4-0DE locomotives built by Brush Traction between 1954 and 1957 had their cabs removed and control gear moved into metal cabinets as slaves.