Rotary Snowplow - Operation

Operation

Wedge snowplows were the traditional mechanized method of clearing snow from railroad tracks. These pushed snow off the tracks, deflecting it to the side. Deeper drifts cannot be easily cleared by this method; there is simply too much snow to be moved. For this purpose, the rotary snowplow was devised.

When snow is too deep, the railroads call on their rotary. The plow is not self-propelled, so one or more locomotives are coupled behind it to push the plow along the line. An engine within the plow's carbody rotates the large circular assembly at the front of the plow. The blades on this wheel cut through the snow and force it through a channel just behind the disk to an output chute above the blade assembly.

The chute can be adjusted to throw the snow to either the left or the right side of the tracks. An operator sits in a cab just above and behind the blade assembly to control the speed of the blades and the direction of output from the chute. With the advent of dieselization, MU controls have been added to the cabs, so that the pushing locomotives can be controlled from the plow.

In areas of particularly deep snowfall, such as California's Donner Pass, railroads sometimes would create a train consisting of a rotary snowplow at each end (with the blade ends pointing away from each other), and two or three locomotives coupled between them. With a plow on each end, the train would be able to get itself back to its starting location even if the snow covered the tracks it had just passed over. Such a train would also be able to efficiently clear multiple track mainlines as it could make a pass in one direction on one track and then reverse direction and clear the next track. This practice became standard for the Southern Pacific Railroad on Donner Pass following the January 1952 stranding of the City of San Francisco; during attempts to clear the avalanches that had trapped the train, two rotary plows were themselves trapped by avalanches, and the crew of a third was killed when their plow was hit by an avalanche.

Rotary snowplows are expensive due to their high maintenance costs, which the railroad incurs regardless of whether they are needed in a given year. As a result, most railroads have eliminated their rotaries, preferring to use a variety of types of fixed-blade plows that have significantly lower maintenance costs, in conjunction with bulldozers, which can be used year-round on maintenance-of-way projects. In addition, because rotaries leave an open-cut in the snowbank that fixed-blade plows cannot push snow past, once rotaries have been used, they must be used for all further significant snowfalls until the snowbank has melted. Since rotaries, which need some form of fuel to power the blades, also cost more to operate than fixed-blade plows, they are now generally considered to be a "weapon of last resort" for the railroads that own them; they are only used when snow is too deep or heavy for fixed-blade plows.

The few remaining rotary plows are either owned by museum railroads, or are kept in reserve for areas with poor road access and routine severe snowfall conditions; the largest remaining fleet of rotaries consists of Union Pacific Railroad's six ex-Southern Pacific plows reserved for Donner Pass.