center locomotives

[Anonymous]

I live in Pittsburg Kansas and I've noticed that a lot of coal trains are powered by two locomotives up front followed by two in the middle. I've also noticed that the loco's are almost always mixed pairs, one EMD(sd70mac) and one GE(dash9 or newer ac). Why use loco's in the middle and why not pair the same types of loco's? These trains are BNSF and KCS. What types of problems or advantages do mixed locomotives present?

[BR60103]

The reson for putting locos in the middle of the train is to reduce strain on the couplings so that they can make the trains longer. There may also be some advantages in using the air brakes.
I don't know the locos that are being used. Is one class always in front? That might mean that one class has had the controls installed and the other is being contolled by it. (It may not even have to be in front to do the job.)
David

[Anonymous]

I understand the easing of strain on the couplings. What I want to know is how handling the train is different. How are the center locos controlled? Does spreading the locos offer greater traction? What are other advantages and pitfalls? I believe it is always Ge followed by an EMD on the trains I see.

[Anonymous]

Ronald
to answer your question. Units in middle and end are controlled by a electronics package called distributed power. Lead unit is equipped with controls that allow engineer to control other units by remote control. Mid and end train helpers can be setup for independent control or to mimic the lead unit. Two units in the middle are MUed together. So one of the units in the middle takes the command from the other unit that is running off of remote control from the lead unit on point. I think most of all having units distributed throughout the train gives the crew better train control in addition to not breaking couplers. Hope that helps!