WM No. 138T
Name: WM No.138T
Railroad of Record: Western Maryland Railway
Type of Locomotive: Slug, rebuilt from cut down ALCO S-1, 660 hp switcher
Manufactured by: American Locomotive Company
Date Built: 1941
Date Rebuilt: 1962
When a diesel locomotive runs at low speeds, the engine and generator produce more power than the traction motors can use. For heavy duty switching services, railroads needed to add more traction motors.
Railroads would take a locomotive and pair it with a "slug." A slug was a set of trucks and traction motors under a heavy ballasted frame. Essentially slugs were electric locomotives that took their power from the other locomotive. Slugs were often built from trucks, motors and frames taken from other locomotives.
The WM No. 138T was originally built in 1941 as an ALCO switcher and was converted into a slug in 1962. In 1967, the No. 138T received a new set of trucks from a Baldwin switcher that had just retired. The No. 138T worked in the Western Maryland's yard in Hagerstown. It was paired with the BL-2 No. 81. The No. 138T was retired to the B&O Railroad Museum in 1987.
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