A&B Units

[jjlamkin]

This might be a stupied question, but
Why is the "B" unit always running backwards. I have also noticed this sometimes with just regular locomotives too??

[jjlamkin]

Ooops stupied = stupid !!

[Anonymous]

Forward or backwards makes no difference the locomotive will run the same. The only reason the lead unit is forward is so the cab will be to the front and the crew can see.

gwl
http://photosbygreg.20m.com

[trainsrus1]

If you are talking about "F" units, ie, "F7" or "F9", the second unit might also be a "A" unit. "B" units are cabless and can run in any direction. In a consist of ABA the two A units would be tail to tail with the B unit between them to avoid turning the power at the end of a run for the return trip.

[BR60103]

The front of B units is arbitrary. I just read where one road put an F on one end of the freght units and the other end of the passeneger units. (Can you tell them apart by where the big fan is on the roof?)
I note that some railroads have their A units all pointing forward on the train and some mix them up.
--David

[Anonymous]

the burlington route used to run the passenger A units elephant style. sometimes four at a time. tim.

[trainsrus1]

F3's have the bigger fans on the cab end of the A units. F7 fans are the same size. The fans on both the 3's and the 7's have the same posistions for both A & B units. I guess that would mean that a B unit does have a front end. In passenger service, the B unit provided the head end power for the rest on the train. Not all A units could.

[DTomajko]

On NS,it is very common to have the final trailing unit in a consist to face opposite the lead engine to avoid turning the consist at the end of a trip,as stated in an earlier reply.On the Pittsburgh Division,(former CR),the lead engine must also be equipped with cab-signals, hence,the newer NS GE Dash 9's and ex-Conrail power dominate most trains on the former CR. Another innovation by NS on the Pittsburgh Division is two engines facing away from each other,(or opposite ends of the train).This is done so that trailing or facing turnouts can be worked without running around the train. DT,Pa.

[filmteknik]

I have this feeling that the original poster does not understand or mean B unit in the sense the rest of us do in terms of a cabless unit since indeed, how would you know which end is the front of a B unit. There is indeed an official and legal front end but it's not something someone would overtly notice if, say, a pair of F-something or E-something A & B unit passed by.

So I premume they simply mean two A units coupled back to back in which case as others have said it's simply so the pair can be (later) used on a train going back the other way without need to turn them. Ditto a hood unit consist which the poster refers to as "regular locomotives". Front unit needs to face forward obviously and if the last unit faces backwards the consist is ready to be used on subsequent train going the other way. Additional units, if any, in between can face either way.

And all of them move in the correct direction when the engineer's controller indicates forward or reverse (forward requiring backwards motion for the units facing backwards) by way of a very simple trick in the way the control lines and MU jumpers are wired!