A second type of electric used by the Milwaukee Road was the now-famed “bi-polars,” Class EP-2. Unique in both appearance and design, the five bi-polars were passenger locomotives with a long record of outstanding service.

They were gearless electric locomotives, meaning that the armature of the motor was also the driving axle. When current was introduced and the magnetic field forced the armature to turn, it turned the wheels directly, not through gears as was the case in other types of electrics.

Long, low, and multi-wheeled, the bi-polars were once called “centipedes on rails.” They were built by General Electric-Alco and were delivered in 1919 and 1920.

The unique appearance of these locomotives made them the star performers of the railroad’s electric passenger fleet. The low curved hoods of the massive bi-polars showed up on almost all of the railroad’s transcontinental passenger advertisements from the 1920s into the 1950s.

Designed to run at 70 m.p.h. and capable of up to 4,120 horsepower, a single unit could handle a whole train over any grade on the line with smooth, silent, smokeless power.

The simple but rugged bi-polars gave years of almost trouble-free service in the Cascades. A railroad policy change ended their use on the Olympian Hiawatha in 1956, and eventually they were put in storage at the railroad’s Deer Lodge, Mont., shops. An attempt to convert the units to freight service was unsuccessful, and as a result, in the early 1960s, four of the units were scrapped. The fifth was donated to the National Museum of Transport in St. Louis, Mo., in 1961.

Probably the most famous exploit of a Milwaukee Road bi-polar was a “tug-of-war” held at Erie, Pa., in 1920.

Fresh off the production line, No. 10251 was coupled nose to nose with two modern steam engines at the General Electric plant. Actually it was to be a pushing rather than a pulling contest since drawbars of the time would not have been able to withstand the tremendous stress.

From a standstill, the throttles of the steam engines were opened first and the bi-polar was pushed slowly backwards down the track. Then the electric began to draw power. Simultaneously, the throttle of the electric was opened further and the steam engine throttles were advanced to their last notch. With a tremendous effort, the steam engines smoked and pushed and strained, but they came to a complete halt. As the controller of the bi-polar was advanced still further, the steam engines, with drive wheels still churning, were pushed backwards.

In a similar test of regenerative braking, the two steam engines pushed the electric until regenerative braking was switched on. As regeneration was turned to full power, the pushing locomotives slowed down. With throttles wide open, the steam engines could scarcely budge the electric which, besides winning the contest, was returning electricity to the overhead trolley wire.

Similar tests were later held on Milwaukee Road track in the west, with the bi-polars emerging victorious each time.



The Bi-Polars


- photograph

- specifications





























"Tug-of-wars" were

actually pushing contests...


The steam engines,  drive wheels churning, were pushed backwards!










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Last Updated: March 03, 2009