| Nickel Plate Road RS11 855 at Calumet City, Illinois on June 13, 1965, Kodachrome by Chuck Zeiler. This locomotive was built in February 1959 (c/n 83019) on Order S-3305 for 14 units, classed ARS-18c on the NKP. It was retired May 1, 1974. The NKP purchased a total of 35 RS-11's in three orders, none of which had dynamic brakes. The RS-11 introduced the Model 251 diesel prime mover in 1956, which addressed several problems with the earlier Model 244 diesel, most notably was crankshaft failure. The crankshaft bearing surfaces were increased in width, resulting in a longer engine block for the 251. Alco reverted to the wet block design, testing had revealed that the Model 244 dry block introduced differential thermally-induced block expansion (the block expanded unevenly when hot), which caused mis-alignment along the crankshaft axis, contributing to crankshaft failure. The turbocharger was a water-cooled Alco design which incorporated an aftercooler to provide cooler combustion air. Cooler air is denser, thus more air could be introduced into each cylinder, improving combustion efficiency. In addition, Alco re-engined two Baldwin AS-16 road switchers for the NKP with 1800 hp 251B diesels. Note how Alco had to cast the poling pockets into the frame behind the steps. |