The Baldwin DS-4-4-660 was meant to replace the company's earlier VO660 design. The two models were very similar offering the same horsepower and wheel arrangement with the biggest difference being the prime mover, which was changed in the DS-4-4-660. Interestingly, while the Baldwin Locomotive Works' own prime mover proved to be a troublesome design in its larger road switchers and main line diesel locomotives the engine actually worked quite well in its small switchers, like the DS-4-4-660 and DS-4-4-1000. The company built three switchers with its own prime mover, including the DS-4-4-750 although this last model was not nearly as successful as its predecessors. As you can also see Baldwin changed its model designations when it began using its own diesel engine, which will be explained in more detail below.
Today, at least three DS-4-4-660s are known to be preserved; Morrisey Femie & Michel #1 at the Western Pacific Railroad Museum, Sloss-Sheffield Steel #30 at the Sloss Furnace Museum, and Chesapeake Western #662 at the Virginia Museum of Transportation.
The Baldwin DS-4-4-660 debuted in 1946, right after the builder canceled its VO660 line. Using a model 606 NA prime mover developed specifically by Baldwin (although the engine could not have been built without the help of subsidiary the I.P. Morris & De La Vergne company purchased in 1931) the DS-4-4-660 featured the standard four-axle, B-B truck setup. As with almost all of its diesel models, Baldwin contracted with Westinghouse to supply it for the locomotives' internal components such as traction motors, generators and air equipment (brakes and compressors). Additionally, the DS-4-4-660 offered tractive effort ratings virtually the same to the earlier VO660; 49,625 pounds starting and 34,000 pounds continuous.
After Baldwin began manufacturing its own prime mover it reclassified its diesel models according to their type (such as road switcher, switcher, transfer, etc.) total axles, powered axles, and finally horsepower. So, in the case of the DS-4-4-660 model the DR referred to Diesel Road unit; the first number, 4, was the designation of four overall axles; the second number, 4, was the designation of four powered traction motors; and 660 stood for the horsepower rating. As the company began to release future designs they shortened the classification system although because they also changed the designation for the same model-type it made things even more confusing. For instance, in the case of the road switcher they used terms such as "DR", "DRS", and "RF".
Once again this "updated" version of the original VO660 sold relatively well, at least for a Baldwin product, with railroads as more than 130 were built through May of 1949. Overall, one could find Baldwin DS-4-4-660s around the country operating on a number of Class I railroads from the Pennsylvania and [original] Norfolk Southern in the east to the Wabash and Chicago & North Western in the Midwest. The model would probably have sold better but with Baldwin already offering the more powerful DS-4-4-1000 design most railroads preferred it instead.
The quality Baldwin offered in its DS-4-4-660 helped it sell as many units as it did, along with its ability to pull just about anything. At 46 feet in length, the same size as its earlier counterpart, also made it an attractive locomotive for industries with companies like Armco Steel, American Cyanamid, Morrissy Fernie & Michel, and others purchasing at least one. Production on the locomotive ended in May, 1949 as the model was replaced by the slightly more powerful DS-4-4-750. For more information about the DS-4-4-660 please refer to the chart above, which offers a complete production roster of the model.