Cow and Calf (Railroad)

I've already described mother/slug units. Those are two permanently attached units where one unit doesn't have a prime mover, alternator, radiator, etc. That equipment is replaced with either concrete or steel to provide weight. A slug has just powered trucks, a frame and dead weight. Two permanently attached units where both are powered are called cow and calf. The cow has the cab and the calf does not have a cab because it is always controlled by the cow. A unit without a cab that can be MUed with other units is a B-unit. A B-unit is intended for road service (intercity trains). A calf is like a slug in that it is normally used for yard or transfer service.

Notice in John's photo that 515 still has exhaust stacks even though it does not have a cab.

John David Larson posted
Sure wish that I had chased the cow/calf set of Belt Railway more than I did during the ten years I lived in Chicago (1991-2001). But, I did get them on this day near Hayford Crossing in 1993.

I now understand why John was so excited to see a calf. Of all the yard/transfer "helper" units I have seen photos of, all of them have been slugs except for this one.

But then a few days later I see the other belt railroad used them.

John David Larson posted
Fond memories, this is a shot from not long after I moved to suburban Chicago in 1991 when I was discovering the remarkable Harbor Belt line through La Grange Park.
I could not believe my eyes - trains like this one, or Chessie, Seaboard, CP Rail, CNW, GT, CSX, CN, Soo Line, Wisconsin Central, NS, SP, UP, and others rolling through these nice little neighborhoods - with the BN "racetrack" main just a short hop away as well (you can see the BN overpass in the distance here).
Mark Bilecki Sr. Yea, I remember it all, the Harbor had the oldest motive power on the planet.
Rodger Horton They were also the the railroad to completely turn to diesel. IHB was the servicing railroad to EMD at LaGrange.

Steven J. Brown postedHerd of IHB cows!

Nine Indiana Harbor Belt units make a power move in IHB's Blue Island Yard at School Street in Riverdale, IL - June 5, 1977.

[But I don't see any calves.]

It seems "calf" was a term for an EMD switcher B-unit and any EMD switcher with a cab was a cow, comments on a posting of a C&EI locomotive:
Mitch Markovitz Yes. A "Cow." For those out there not aware, an SW with a cab was referred to as a "Cow." A cab-less SW was referred to as a "Calf."
Gail Hubartt We called those ‘B units’ or ‘cabless units’. Where I came from, the slugs were used in yard switching and cabless units were used on the road.
Mitch Markovitz The Cow-calf names are only used in connection with EMD "SW" class engines. So you're correct. Cows and calfs were not on all railroads, and were gone a long time ago.

David Daruszka commented on a posting
How about Cow and Calves?

David Daruszka commented on a posting
 It seems to be unique to the C&O.

Donny Albertson posted
Would this be considered an A-B-A set of switchers? IDK but I shot it at Franklin Park on 23MAR1989. Does the IHB still use switchers?
[I suspect it is a calf instead of a B-unit.]
Craig Cloud What you photographed here is gone, NW2's I mean. SW1500's still in use along with newer Gensets and SD20's from NRE along with GP38-2' and SD40-2'S rebuilt (I believe) into SD38-2's. Been a great while traveling over to IL from Porter.

Bill Molony posted
Illinois Central EMD TR #9204A&B switch engine.Kenny Hearn Cow and calf
[I wonder which yard has that coaling tower.]

Bob Lalich Flickr, Aug 1984

Info about CGW, SP, and UP cow+calf units