Rotary snowplow

A rotary snowplow is a piece of railroad snow removal equipment with a large circular set of blades on its front end that rotate to cut through the snow on the track ahead of it. The precursor to the rotary snowplow was the wedge snowplow.

The rotary was invented by Toronto, Ontario, Canada dentist J.W. Elliot in 1869. He never built a working model or prototype, although he wanted to. Orange Jull of Orangeville, Ontario, expanded on Elliot's design, building working models he tested with sand. During the winter of 1883–1884, Jull contracted with the Leslie Brothers of Toronto to build a full-size prototype that proved successful. Jull later sold his design rights to Leslie Brothers, who formed the Rotary Steam Shovel Manufacturing Company in Paterson, New Jersey. Leslie Brothers contracted with Cooke Locomotive & Machine Works in Paterson to do the actual construction.

Another inventor is said to be Col. Lewis P. Campbell. He is listed in US patent 1848554 (filed in 1929).

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 easily be 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 increasing prevalence of diesel locomotives, multiple-unit train 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 created 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 was able to return to its starting location even if the snow covered the tracks it had just passed over. Such a train would also be able to clear multiple track mainlines efficiently as it could make a pass in one direction on one track, 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 train; 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.

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