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.