Never quite understood this.

[traisessive1]

This goes for any train...2 engines plus.
I see road freights that are back to back, nose to back, and nose to nose ( long hood forward) ....
ow to the tracktion motors on the trailing units operate when the lead unit is going forward and the others would half to be in reverse?

how does this work, its not like the others are in reverse and the lead in forward ... how does tht work?

[Anonymous]

Might be a certain way to connect the locos? May also have something to do with the computer systems that are integrated into modern locomotives.

[traisessive1]

mmm true...

[ironhorseman]

Hmmm, that is puzzling. How do "reversed" locos know which way is forward? But remember the early diesels didn't have computers. I also understand the diesels work the same in forward or reverse but how is done automatically? How was it done on 1st generation locos? It's probably done the same way today right? So they can work with older locos when put together.

[traisessive1]

I want to know!!!!!!

[Jackflash]

Ok, heres how it works,, think of two control wires, one for foward and one for
reverse, they go to the MU receptical at each end of the locomotive (I think they
are pin 8 and pin 9) , lets say they are, OK, lets call foward #8 and reverse
#9 at the front of the engine but at the rear of the locomotive they will be reversed, 8 will be reverse and 9 will be foward, now, the jumper cable
that goes between coupled locomotives also has these wires reversed,
heres a little something you can do to see this... You draw 4 locomotives
on a piece of paper (nothing fancy) now draw two lines from the front to the
back of each engine, but before your pencil gets to the back cross the wires (make an X
with them) dont do it at the front, just the back, mark one of the wires "F"
and the other one "R", you can draw your locos in any position, back to back
front to back, nose to nose, ect ect. now draw a X between each engine, this
will repesent the crossed jumper cable, now using your pencil follow the
foward line and you'll see when ever it grts to a loco thats running in reverse
it will be on the "R" line, when ever it comes back to a loco running foward
it will be on the "F" wire, this folks, is how its done. Jackflash

[daveklepper]

Same principle holds for mu rail cars, diesel railcars, electric mu cars for subway, interuruban, and commuter service, and electric locomotives. Dave Klepper

[kenneo]

You will notice in Jackflash's illustration, where the units are elephant style, nose to tail, the front wires stay lined up and the wires in all other arrangements cross to "change polarity" (the electrical term).

[traisessive1]

thank you, that helps a lot