A friend in England sent this link to what looks like two Southern Pacific plows under steam.

http://www.shastarails.com/photos/pbu.a ... /2011&pg=2

Both of these were converted to electric power in the 50s. What are we looking at?

Anyone else want to explain? The blades are electric powered, but the units need steam for some other functions and they still have a whistle. The steam comes from common steam generators, such as those from train heating.

Steam is used to heat piping that might freeze up as well as to flood the cutting wheel in case it also gets stopped by icing up. The steam pipes are placed next to vulnerable fuel pipes, for example. The retired rotary at the National Museum of Transportation near St Louis has these features.

As Ron said, all of the key parts have steam tracer lines to prevent freezing. Wing hinges, windows, chute, blade, etc... and of course, they kept the whistles. Even the rebuilt SP plows got brand new steam generators.

BN family plows never seemed to use this feature.

Thanks for your help. I thought it was something of that nature but didn't want to pass along my uniformed guesses.

Hi John T,

While at the Trainfest 99 in Sacramento California , I met "the bear of/on the hill " ,Mr. Jim Mahon. I don't remember if he was an MTM (roadmaster) or higher , but he was in charge of keeping SP/UP Donner Pass passable 24/7 .
His one story relates to your inquiry about the SP rotaries . Donner Pass receives heavy wet sticky snow . To deal with it the SP's rotary's blades and chute had to be heated so nothing would freeze to them thus flinging off the sticky snow without over taxing the machinery . When they were converted to electric ,they still needed a steam supply to keep the blades and chute from clogging .Thats why they still have steam generators today.
After the "merger" Jim said ,the UP wanted to side line the SP's rotaries and brought up their newest one to show the SP guys how to really "railroad" ." It burned right up and they took it away" . The SP units are still operating .