Rotary Snowplow: Workhouse of Donner Pass

Work on the railroad does to stop for weekends or holidays. And it certainly does not stop for inclement weather.

Some of the deepest snow can be found on the western slope of the Sierra Nevada Mountains and at the summit of Donner Pass. This was the same pass that turned away members of the doomed Donner Party in the Winter of 1846. This pass would not defeat the Southern Pacific Railroad from crossing the pass.

To keep the pass open the railroad, when spreaders and flangers failed, SP used their most powerful snow fighting weapon, the rotary snowplow.

The rotary plow was invented by a dentist in Toronto, Canada in 1869. The plow consists of a circular sent of blades that spins. The rotary plow is not self-propelled but is pushed by a locomotive or most likely locomotives. As the spinning blade cuts through the snow drift, the engineer can control which side of the track the chute, behind the blade assembly, throws the snow. Left or right.

Not much has changed with the design of rotary plows save for powering the prime mover. All early rotaries where powered by steam but they were later converted to diesel or electric power. In fact, most of the current fleet of rotary plows, used by Union Pacific, where built in the 1920s or 30s although they have been retrofitted and rebuilt since then.

The current rotaries still use a steam generator to help prevent some of the moving parts from icing up and seizing.

Most railroads use flanger or spreader plows but these plows meet their match when trying to push heavy snow from tracks. This is where the rotary plow has the distinct advantage. It does not need to be pushed by force, instead the rotating blades cut through snow like a hot knife through butter. And the rotary can throw snow away from the track.

The downside to rotary plows is that they are expensive to maintain. And depending on snowfall, the plows may not be put into service every snow season. It may be even ten years before the rotary is called into action. The plows are also labor intensive to operate with an average crew size of 12. The standard consist of a Southern Pacific rotary train would consist of two rotary plows (one on each each so they can remove snow in both directions), a B Unit for each rotary to supply electrical power and air pressure, and two or three locomotives.

As a result, most railroads have gotten rid of their rotaries and many have been donated to serve as static displays. Three former Southern Pacific plows are on display. One in Roseville, Truckee, and Sacramento, at the California Railroad Museum.

A very interesting sign at the Union Pacific (formerly Southern Pacific) rail yard in Roseville. I wonder if before this sign was installed, the Roseville Police got many calls about runaway locomotives!

What’s interesting about the rotary plow on static display at Roseville (SPMW 7221) is that it is near the tracks at the Union Pacific rail yard. The rotary was donated to the City of Roseville by Union Pacific in 2014. This is fitting because Roseville is where Union Pacific’s rotary plow fleet is based. As I looked down the tracks toward the rail yard, I noticed, on the far side where two rotaries.

Roseville has been a major division point on the Southern Pacific railroad. At it’s height, during the age of stream, the Roseville yard contained two roundhouses. Roundhouse No. 1 was a 32-stall roundhouse and Roundhouse No. 2 was specially built to house the larger Mallets (4-8-8-2) know as cab forwards. The turntable was large enough to turn these massive locomotives. These locomotive were reversed so the crew rode in the front and the exhaust behind them. This was to avoid asphyxiation in the long snow sheds over Donner Summit.

Union Pacific is one of the few Class I railroads that keeps a rotary fleet and they have the biggest fleet in America with six plows.

Two of Union Pacific’s six active rotary snowplows SPMW # 222 and 207.

The winter of 2017 was the third snowiest winter in recorded history on Donner Pass. The Union Pacific rotaries where put into use to clear the 13 feet deep snow to keep the line open between Roseville and Truckee.

Here is footage of rotaries at work at Donner Pass in February 2017. Credit to Jake Miille Photography.

Head on view of SPMW 207 at the Roseville rail yard. This provides a view of the circular, rotating blade that cuts through snow. Number 207 awaits the call to head up towards Donner Pass to clear the line of snow. Number 207 was built in 1926 and has since been upgraded. The “SPMW” stands for “South Pacific Maintenance of Way”.

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