Portal:Trains/Selected article/Week 22, 2007

The ALCO DL-109 is one of six models of A1A-A1A diesel locomotives built to haul passenger trains by the American Locomotive Company (ALCO) between December 1939 and April 1945. They were of a cab unit design, and both cab-equipped lead A units DL-103b, DL-105, DL-107, DL-109 and cabless booster B units DL-108, DL-110 models were built. The units were styled by the industrial designer Otto Kuhler, who incorporated the trademark 3-piece windshield design. A total of 74 cab units and 4 cabless booster units were built. The different models were sequentially offered and all developed 2,000 hp (1,500 kW). The differences between the cab units DL-105, DL-107, DL-109 and between the booster units DL-108 and DL-110 were minor. The first unit built to ALCO Specification DL-103b, the Chicago, Rock Island and Pacific Railroad #624, was 4 ft 5 in (1.3 m) longer than the other cab units. The DL-103b had the two radiator sections positioned together at the end of the carbody, while all other units had a split radiator arrangement with one placed at the back of the unit and one situated in the middle. The DL-103b was built with twin straight-6-cylinder ALCO 538T diesel engines as prime movers; all other DLs in this series were built with the newer twin straight-6-cylinder ALCO 539T diesel engines. The DL-103b also had all-electric driven accessories, while the later models had belt-driven accessories.