A walk through a Southern Pacific Rotary Snowplow

    I had the opportunity to explore a pair of Southern Pacific Rotary Snowplows recently.  Of course the digital camera was handy...  The following is a few photographs and an explanation of how the controls work and the purpose of some of the strange and wonderful things found inside of these unique and magnificent machines.  Since few people have the opportunity to "go through" one of these unusual machines, I decided to put this page together so anyone can have a look around...
    Most of the photos were taken in SPMW 208,  in Truckee, CA.  This machine is a Leslie Rotary Plow, originally built in 1927, and constantly modified by SP to make it suitable for the unique snow conditions on the "Hill" between Roseville, CA and Sparks, NV.

     This is SPMW Rotary 208.   The plow proper is normally powered by an EMD F7B locomotive that has had it's traction motors removed, which is known as a "Snail".  Large cables run between the Snail and the plow.  The power is delivered to four standard locomotive traction motors geared to the shaft that turns the rotary blade wheel.  The wheel is reversible, so that the snow can be blown to either side of the track.
      SPMW 208 was built by ALCO (Brooks) in September 1927, c/n 67429  as SP 707.  It later was renumbered to SP 712, then SP 7208 and finally to SPMW 208.
     These machines were originally powered by steam, generated by a locomotive type boiler within the car body.  Over the years, SP extensively rebuilt these machines several times, making them unique and especially suited to moving the "Sierra Cement" snow found on the Donner Pass Line.  SPMW 208 was converted to electric power in 1970.
SPMW 208 and Snail SPMW 8211 are operable and are now preserved at the Western Pacific Railroad Museum in Portola, CA.
     I recently had an opportunity to be aboard this plow while it was in operation.  When the wheel is turning at 110 RPM, IT GETS YOUR ATTENTION!  We at the Western Pacific Railroad Museum are now praying for lots of snow so we can REALLY try it out...
      Normally, the rotary plows are placed on either end of a consist, which would consist of a plow, snail, three or four locomotives that provide tractive power, a snail and a rotary facing in the opposite direction.  This was done so that the set would not be "trapped" in case of a slide or additional snowfall behind it, and the set did not need to be turned.
     The entire operation was controlled from here.  There are controls for the rotary wheel, both speed and direction, as well as the locomotive consist providing the tractive effort.  Note the 26L brake system, which is of the same type used by modern locomotives.
     It would have been MOST interesting to have seen the same area when these were steam powered.
These plows are equipped with a Vapor-Clarkson steam generator of the same type as used in Diesel passenger locomotive before the advent of Head End Power.  The steam comes in handy for heat, cleaning ice out of the wheel and blowing the steam whistle.
Below are two more views of the control area.  On the vertical panel are the air brake gauges, wheel tachometer, an ammeter for the motors that turn the wheel and various other auxiliary controls.

In the overhead panel are found the air horn and steam whistle valves, as well as the bell valve.  There is also a reading light.
This is the back wall of the operating cab.  The entire interior of the cab is wood, of course painted "Seafoam Green", by E. C. Judd in Roseville.
The black panel hold the isolation switch and various other controls.
The wheel tachometer (below) looks for all the world like an old Barco locomotive speedometer which has been modified slightly...
Here are two of the four traction motors that power the wheel.  There are two shafts that run lengthwise, with two motors geared to each shaft.  The two shafts are geared to the main wheel shaft forward.  The motors are standard off-the-shelf EMD traction motors, making parts supply a little easier.
Below are the cables that run to the "snail" unit when the plow is in service.  Now THIS is  a set of jumper cables!

This plow hasn't been in service for many years, but except for a layer of dust, she appears quite serviceable. 
Neither of these machines are equipped with the fold out "wings" like the plows in Roseville, leading us to believe that these are "emergency back-up units.  These plows are limited to plowing their own width only...

Overhead, there is a water tank, carrying feed water for the steam generator.  It is located inside the car body to avoid freezing.

Obviously, they thought of EVERYTHING!  Note the steam line labeled "Antenna Defroster".
I know from experience that radio antennas don't work well when covered with ice...
Side view of SPMW 208.  Note the steam generator exhaust stack at the right rear corner of the car body. 
Close up of the unique Fox type truck, with "slight" modification.  These are the original type of truck that these machines had when new, but not with roller bearings...
Note also that the trucks have no springs and are well chained to the car body.  Rotaries tend to derail a lot...
Other info here is the weight of the plow, 248920 lb.., about the same as an F unit or GP9.  Note the paint date.  Painted 25 years ago and looks it...
According to the paperwork found inside (and LEFT there) the rotaries are considered to be locomotives.  This makes sense, as they have all the controls found in a locomotive and are in fact just a "Cab Car" with a VERY large snow blower mounted on the front.
SOME Cab Car!

The rotaries were even equipped with Automatic Train Stop when that system was in place on "The Hill".  The ATS was installed  there around 1910 between Colfax and Truckee and was removed in the late sixties.  The reason for this installation was that  the visibility gets pretty bad during a blizzard.  I would imagine visibility is even worse out of one of these...  Note the "spinner windows" that show up in several of the pictures.
In case you can't read the card, the dates are all in 1967.
The "Business" end.  The wheel can rotate in either direction, while the blades automatically position themselves to the proper angle.  The coupler and the bar that holds it in place are removed during operation and hung under the side of the carbody.
     Now here's an interesting little mystery.  What was an SP Rotary doing on the Western Pacific in Keddie, on January 15, 1971.  Did WP get rid of their Rotaries a little too soon and have to borrow one from SP???

     If the Union Pacific Railroad plays it smart, these "old girls" will be around for quite a while...  They don't need the Rotaries every year, but every now and then, Mother Nature "ups the ante" and then these MAGNIFICENT machines earn their keep.
The following is copied off of a notice posted in the cab of one of the plows.
I have a picture of it, but it's really hard to read.
OPERATING INSTRUCTIONS FOR ELECTRIFIED 
ROTARY SNOW PLOWS, POWER AND PUSHER UNITS

When making out Forms CS-2326, "Engineer's Work Report", refer to each unit number.
Operating cab on Plow is equipped with two centrally located hostler type controllers:
one controls speed and direction of Plow rotary Fan, and the other controls speed and direc-
tion of Pusher units.
Control panel maintains all necessary switches and warning lights for Operation of Plow,
Power unit, and Pusher units.  All are labeled and are self-explanatory.
Amperage gauge registers output of main generator in Power unit which is protected by 
two overload relays, OLR 1 and OLR 2.  When output of main generator in Power unit regi-
sters 800 amperes, OLR 1 will reduce Power unit to "IDLE".  OLR 2 functions when Power unit output reaches 1200 Amperes, reducing Power unit to "IDLE".
Maximum rotation speed of rotary fan is 150 RPM.  Recommended operating speed range is 90-120 RPM.  An indicator, coupled to a tachometer generator indicates speed of rotary fan and will return Power unit to "IDLE" if rotation speed reaches 150 RPM.  Normal rotation speed control is recovered by returning plow throttle to "IDLE".  Should this occur, Pusher throttle should also be returned to "IDLE" and air brakes applied to prevent fouling of snow chute and blades.
Hump control is provided to aid in controlling rotation speed.  Advancing lever from "OFF" to "FULL APPLICATION" raises rotation speed.
Power unit throttle has a stop between No. 1 throttle and "OFF" positions.  To open throttle, depress lever to raise  stop.  Move power throttle to desired position.  For normal operation, throttle should be between No. 1 position and No. 8 position, as required.  DO NOT RETURN THROTTLE TO "OFF" POSITION UNLESS OPERATING CONDITIONS MAKE IT NECESSARY.
Plow is equipped with WABCO #26 brake equipment. (except SPMW 210, see next paragraph)  There is no Rotair valve.  When operating from plow, place cut off cock (double heading cock) located on automatic brake valve in "FREIGHT" position and brake pipe valve, located in cabinet under brake valve in "OPEN" position.  The MU-2A valve, located under cut off cock (double heading cock) must be  in "LEAD OR DEAD" position.  To move both these valves, push in and turn operating handle.  Trailing "A" unit is handled in usual manner as prescribed in Air Brake Rule 2-A.
To change ends, place Pusher throttle in "IDLE", reverser in "NEUTRAL" and remove handle.  Make full service reduction with automatic brake valve.  Move independent brake valve handle to "FULL" application position, close double heading cock, move cutoff cock to cutoff position, move MU-2A valve to "TRAIL 24" position. (arrow pointing downward)  Return both brake valves to "HANDLE OFF" position.  If plow is to remain idling, open generator field circuits.
SPMW 210 ONLY is equipped with WABCO SA-2 brake valve and all brake components.  Brake valve cutoff cock is located in cabinet under brake valve and brake pipe cutoff cock is located outside beneath cab floor in ATS compartment on right side of plow.
 

There.  Now we know how to run an SP Rotary.

Updates, such as accurate dates of construction, rebuilding, etc. will be made as I get the information.
This page IS under construction.
For more information, I recommend finding a copy of "SNOWPLOW, Clearing Mountain Rails",
by Gerald M. Best.


There is an "unmodified" steam powered rotary plow on display at the Northwest Railway Museum at Snoqualimie, WA
Their page about this plow is Here

Further information on rotary snowplows can be found via the links below.

Wikipedia Rotary Snowplows

The Rotary Snowplow, A Canadian Invention

Rotary Snowplow List by Andrew Toppan

Page created September 16, 2000
Last modified November 28, 2006

If you have any questions or comments about this page, feel free to e-mail me.

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