Conrail's SD38's were purchased expressly for hump service by the Penn Central in 1970. They are still performing that function for Conrail. Many of these engines serve as "mother units" to Motor Trailers, commonly referred to as "slugs". A slug is a locomotive frame weighted by tons of concrete, with traction motors but no diesel engine. Power for the traction motors is supplied by the mother unit's prime mover. This arrangement provides the adhesion needed to push mile long strings of cars over a classification yard's hump at a steady walking speed
Conrail's MT-6 slugs were constructed from retired American Locomotive Company (ALCO) six-axle road switchers (RSD-12's and RSD-15's) in 1978 and 1979 at the Juniata Shops in Altoona, Pa. All MT-6's, have had their original ALCO tri-mount trucks replaced with EMD trucks salvaged from retired SD's.
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SD38 6925 and MT-6 1119 drag a long string of cars though Allentown yard in the summer of 1981. Note the caboose coupled to 6925. |
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MT-6 slug 1119 and SD38 6925 pause at the top of the Allentown Hump on March 31,1983. Note the Alco tri-mount trucks under 1119. |
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SD38 6935 and MT-6 1124 humping cars in the Allentown yard. June 1993. |
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With the consolidation of engine facilites, hump units must be transported to be serviced. SD38 6926 and MT-6 1125 en route to the Enola Diesel House at CP Capitol in Harrisburg, Pa. on March 28,1997 |