Once in a blue moon I get this posted in a timely manner...but not this blue moon. I'll try to add to the fun later. Perhaps some Pictures from Day out with Thomas last weekend.
Saw this in Louisiana a few weeks ago. UP calls them a CCRCL (Control Car Remote Control Locomotive). I believe they are old SP B30-7s. They are just a trailer with remote control radio stands and MU connections. I have seen flat cars with the same setup.
See here: http://utahrails.net/up-diesel-roster/upy-ccrcl.php That's a lot of dead weight for an R/C sled!
I'm not certain, but I think they might be kaolin clay cars. There're no placards on the cars, so a harmless commodity like clay is likely.
I've always thought of that commodity being a hopper type shipment. They must have found a way to liquify for easy loading and unloading.
Yes, Kaolin is shipped as a slurry to large volume customers. We should add a few of these neat kaolin tankers to our fleets! This is from Atlas in N Scale. I worked in the paper industry for many years and we used kaolin clay as a filler and sheet brightener until we later substituted calcium carbonate.
Possibly protection from the "slosh factor". During emergency brake application, the momentum of the slurry might overtake the locomotives depending on how quickly the train was stopping. The box cars would provide safety by crushing and absorbing the momentum of the cars before they hit the locomotives. This technique is used with many heavy loads. KCS did this with a hopper when they delivered a 300 Ton transformer to Mississippi Power after Hurricane Katrina.
One of my favorite images taken by Jack DeLano when he rode the Santa Fe from Chicago to Los Angeles and back during WWII. The 5000 (nick named Madam Queen) is on a siding in New Mexico waiting for another train to pass. His photos are all on file at the Library of Congress web site. They are raw TIFF images with ragged edges and dust but still very high resolution. I like to down load them and clean them up in Photo Shop.
Noticed that too. Other pictures I've taken of this train over the years sometimes have the kaolin cars directly behind the power. I have a friend who works with things like this and I'll ask.