Design
In 1917, following the tremendous success of the 1915 electrification of the Mountain Division, the Milwaukee Road decided to proceed with electrifying the Coast Division. As part of this project it ordered five new electric locomotives from General Electric for $200,000 apiece. Their design was radically different from the boxcab locomotives previously provided by GE for the initial electrification of the Mountain Division two years earlier. The Milwaukee Road was the only railroad to order this design of locomotive from GE.
The most remarkable mechanical improvement was arguably the traction motors used on the new locomotives. They were known as bipolar motors because each of the locomotive's 12 motors had only two field poles, mounted directly to the locomotive frame beside the axle. The motor armature was mounted directly on the axle providing an entirely gearless design. This design was almost entirely noiseless as it eliminated not only gear tooth growl but also the whine of higher-RPM electric motors typically used in standard nose-mounted applications. The EP-2s were not the first electric locomotives to use bipolar motors, which had first been designed by Asa F. Batchelder for the New York Central S-motors over a decade earlier, but at the time they were the largest.
The layout of the bipolars was unusual as well. The locomotive carbody consisted of three sections. A small center section contained a boiler for heating passenger cars, while the larger end sections contained the locomotive's electrical equipment and operator cabs in distinctive round-topped hoods. The locomotive's frame was split into four sections, hinged at the joints, with the two middle sections attached to the end sections of the locomotive body. There were twelve sets of driving wheels, plus a single idler axle at each end, for a 1B+D+D+B1 wheel arrangement. All buffering forces were transmitted through the locomotive frame.
The bipolars were designed to be able to pull any Milwaukee Road passenger train singly, and were originally delivered without multiple unit controls. GE claimed a top speed of 90 mph (145 km/h) for the locomotives but the Milwaukee Road rated them at 70 mph (115 km/h). They were rated at 3,180 continuous horsepower (2.37 MW) with a continuous tractive effort of 42,000 lbf (190 kN) and a starting tractive effort of 116,000 lbf (520 kN).
Read more about this topic: Milwaukee Road Class EP-2
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