Cow-calf

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For the production of beef cattle, see
cow-calf operation. For the rocks in Yorkshire, England, see Ilkley Moor
.

EMD TR1 diesel locomotive with two units—cow and calf

In

cab; a calf is not. 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.[1]

Cows are analogous to

B unit (powered locomotives without a cab) road locomotives. The cow and calf are both equipped with prime movers for propulsion. Like the early EMD FT locomotives, the cow-calf sets were typically built as mated pairs, with the cow (or cabbed unit) and calf (or cabless unit) sharing a number. However this was not always the case, as over time many of the sets were broken up and couplers added to aid with versatility. 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.

Most cow-calf sets were built by

road switcher
locomotives, which could handle both mainline trains and switching duties.

Distinctions between cow-calf, B units, and slugs

This locomotive and slug of the Iowa Interstate Railroad resemble a cow-calf set, but the slug has no engines of its own; this allows it to be cut down for better visibility.
These EMD FP9 locomotives also resemble a cow and calf, but the B unit is designed for mainline speeds, and to be detachable and operate with any other locomotive.

Cow-calf sets are similar to

B units (powered booster locomotives which do not have cabs).[2] They differ from both in that a B unit is designed to operate with any other locomotives, while cow-calf sets are meant to be semi-permanently coupled to each other with a drawbar and operated together, though some cow-calf sets used standard couplers instead.[2]

A slug is semi-permanently paired with a cabbed unit, but does not have its own engine. At low speeds, many diesel-electric locomotives generate more electrical current than can be used by their motors. Slugs use this excess current to power their traction motors. In contrast, all units in a cow-calf set have their own engines.[2]

History

Design and nomenclature

In a cow-calf set, the cow referred to the locomotive equipped with a cab, while calves lacked a cab.[3] Cow-calf sets with two calves are known as "herds"; the only example of these were two TR3 series sets ordered by the Chesapeake and Ohio Railway.[1][4] The cow, calf, and herd designations were nicknames.[4]

Cow-calf locomotives were designed for both transferring railroad cars between nearby classification yards in urban areas, and for switching within yards. They were built with an emphasis on tractive effort, with top speed of lesser importance.[1]

Production and operations

A Belt Railway of Chicago cow-calf set in 1985

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, chiefly its TR (transfer) series.[1] In addition to the transfer duties they were designed for, cow-calf sets were also used in hump yards to send cuts of cars over the hump for classification.[5]

The

road switcher locomotives.[3] The Belt Railway of Chicago was the final holdout, continuing to operate TR2 and TR4 sets into the 1980s and 1990s.[5][3]

List of cow-calf models

EMD TR4
British Rail Class 13

TR series

EMD's TR (transfer) series were the largest group of cow-calf locomotives built. Produced in seven models, eighty were built between 1940 and 1953, along with two additional calves.[1][4]

  • EMD TR
  • EMD TR1
  • EMD TR2
  • EMD TR3
  • EMD TR4
  • EMD TR5
  • EMD TR6

Other cow-calf models

The American Locomotive Company (ALCO) built two cow-calf sets, derived from the ALCO S-6 and designated SSB-9.[7]

Baldwin Locomotive Works produced nine cow-calf versions of the Baldwin S-8. Both ALCO and Baldwin's cow-calf sets all went to customer Oliver Mining.[7]

Cow-calf locomotives in the United Kingdom are generally referred to as 'master and slave' locomotives. Three sets were created by

DE locomotives built by Brush Traction between 1954 and 1957 had their cabs removed and control gear moved into a metal cabinet as slaves. Five similar locomotives were equipped to work as masters. The conversions were done in 1971 and they were taken out of service in 1986.[10][11]

See also

References

  1. ^
    OCLC 38738930
    .
  2. ^ a b c Lustig, David (April 1, 2011). "Difference between a cabless booster, a slug, and a calf". Trains. Retrieved November 12, 2022.
  3. ^
    ISBN 978-0-395-70112-6
    .
  4. ^
    OCLC 34531120
    .
  5. ^
    ISBN 978-0-7603-4603-7
    .
  6. ^ Kelso Depot Historic Structure Report: Mojave National Preserve, California : an Oasis for Railroaders in the Mojave. U.S. Department of the Interior, National Park Service. 1998. p. 111.
  7. ^
    ISBN 978-0-89024-761-7
    .
  8. ISBN 0-86093-108-0
    .
  9. ^ Marsden, Colin J. (2018). "Locomotive Directory". Modern Locomotives Illustrated. No. 230. p. 43.
  10. ^ Smith, Keith (1999). Supplement to the West Somerset Railway Stockbook (5th ed.). Bishops Lydeard: West Somerset Railway Association. p. 9.
  11. ISBN 0-901096-44-X
    .
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