Why were AA units (or ABA, ABBA, etc) usually run back to back?

[FJ and G]

Is it because:

1. The locos didn't need to be turned around

2. The crew could walk from one unit to the next

I realize that with more than 2 A units were run all sorts of ways.

[tree68]

The correct answer (assuming that the engines didn't just happen to be facing that way when they were coupled together) is 1.

There being a door in the nose of any E or F unit I've seen, getting between units could happen no matter which way the units were facing. Wouldn't be fun, but it could happen.

[railroad65]

When they were first introduced, they were draw bar connected for union reasons (crew size). So the best thing if two "A"'s were connected was for them to be butt to butt.

[TomDiehl]

Yes.

In the early days, the A-B-B-A set was considered a single locomotive and was usually drawbar connected with the cabs facing out for the reason that they didn't need to be turned. Once they got past the operating considerations or union agreements of one loco = 1 crew, they were coupled the current way. The operating department now determines how to face the engines for each train, taking such things as turning facilities, route, , etc. into consideration for each train.

[Anonymous]

CGW had to run A-units back to back because they ordered them without MU cables on the front of the A units. So theirs couldn't be run AAB, for example.

[Anonymous]

I think yet another reason is the railroad probably thought they looked better that way.

[BaltACD]

QUOTE: Originally posted by dirtyd79

I think yet another reason is the railroad probably thought they looked better that way.

Railroads don't think about looks when it comes to moving tonnage.

[David_Telesha]

QUOTE: Originally posted by BaltACD

QUOTE: Originally posted by dirtyd79

I think yet another reason is the railroad probably thought they looked better that way.

Railroads don't think about looks when it comes to moving tonnage.

They used to...

The New Haven also had to run AA back to back with some of their engines (DL109s) because of the lack of MU cables in the nose, though 2 units recieved them - one had the nose completely rebuilt.

The NH's FA-1's routinely ran ABBA or ABA, even ABB, and AA. I think there is one pic of a ABBBA set!!!!!!!!!

[CSSHEGEWISCH]

Drawbar connections between two cabs was quite rare. The only drawbar connections of which I'm aware were between a cab and a booster on FT's and between the cow and the calf on TR sets. BRC ran TR sets with drawbars until they were retired around 2000 or 2001.

[Anonymous]

I knew that they were back to back just to avoid turning them on turntables. My question has to do with numbering- on some of the Southern railroad E units I have seen, the numbers are followed by an "A" (meaning lead unit?), a "B" (meaning trail unit?) and sometimes a "T".... what is that all about?

Erik

[samfp1943]

QUOTE: Originally posted by David_Telesha

QUOTE: Originally posted by BaltACD

QUOTE: Originally posted by dirtyd79

I think yet another reason is the railroad probably thought they looked better that way.

Railroads don't think about looks when it comes to moving tonnage.

They used to...

The New Haven also had to run AA back to back with some of their engines (DL109s) because of the lack of MU cables in the nose, though 2 units recieved them - one had the nose completely rebuilt.

The NH's FA-1's routinely ran ABBA or ABA, even ABB, and AA. I think there is one pic of a ABBBA set!!!!!!!!!

Another reason the earlier E units A's were not put nose to nose, might have been because some of those units had a pretty extreme rake to their noses, and to jump that gap[ with a unit set moving or sitting] would require some luck and athletic prowes, not to mention an extremely dangerous area to be leaping around in.
Sam

[Paul Milenkovic]

So why is Amtrak running their P42's both units nose first? They lose the advantage of not having to turn them? Is it if they have to cut off a locomotive enroute that they don't have to turn the second locomotive?

[Anonymous]

QUOTE: Originally posted by Paul Milenkovic

So why is Amtrak running their P42's both units nose first? They lose the advantage of not having to turn them? Is it if they have to cut off a locomotive enroute that they don't have to turn the second locomotive?

Amtrak didn't start that practice with the P42s. They have always tried to do it on long runs so if the lead engine failed, the second engine was pointed the right way and could drag the train to the next maintenance point.

Old Timer

[CSSHEGEWISCH]

QUOTE: Originally posted by Paul Milenkovic

So why is Amtrak running their P42's both units nose first? They lose the advantage of not having to turn them? Is it if they have to cut off a locomotive enroute that they don't have to turn the second locomotive?

ATSF used the same practice with its F's and F/FP45's prior to May 1, 1971 for the same reason mentioned above (in case of engine failure). SCL ran its E's the same way on its Florida streamliners to facilitate the splits at Jacksonville, Ocala, etc.

[tree68]

QUOTE: Originally posted by erikthered

My question has to do with numbering- on some of the Southern railroad E units I have seen, the numbers are followed by an "A" (meaning lead unit?), a "B" (meaning trail unit?) and sometimes a "T".... what is that all about?
Erik

Part of it goes back to what was mentioned about the engines running as sets. Santa Fe had a similar practice. It made a lot of sense when the engines were actually run as sets, but got a little funky when they broke them up. I know I've read about the logic involved in one or the other of the railroads numbering schemes, but I can't remember the details.

[zardoz]

QUOTE: Originally posted by Old Timer

QUOTE: Originally posted by Paul Milenkovic

So why is Amtrak running their P42's both units nose first? They lose the advantage of not having to turn them? Is it if they have to cut off a locomotive enroute that they don't have to turn the second locomotive?

Amtrak didn't start that practice with the P42s. They have always tried to do it on long runs so if the lead engine failed, the second engine was pointed the right way and could drag the train to the next maintenance point.

Old Timer

Or if the lead unit was damaged in a collision.

My question, since I retired before the desktop contropls became widely used, is: do the railroads consider the control stand configuration when assigning units today? I'd sure hate to have to operate a train with my lead loco facing backwards; it was bad enough with the old control stand, it must really suck operating reversed with the desktop controls.

[jimrice4449]

One specific example of AABB operation was SP #51/52 between LA and Bakersield. The lead unit was a helper for the Tehachapi grades and was added or taken off at Bakersfield so the second A unit became the road engine.

[edbenton]

Another thing if you ever noticed on the Santa Fe F-units the passenger train could have been 2 cars long yet it always had a B unit on it. The reason is no Santa Fe F-units had a steam heat unit in them. The space for that was taken by a large water tank for the B-units boiler. That way they did not have to stop all the time for water for the Steam heat units. They also ran steam ejection A/C so even in the summer you would see steam coming out from teh heater pipes on the back.

[gmstm]

Based on my experience on the Southern in 1962 with a single EMD F-3/7A unit (F-3 upgraded to F-7 standards) there were no controls to operate the back-up sanders. EMD designed the F's to operate in AA, ABA or ABBA combinations. This failing was brought home when we were pushing the weedspray train around a wye at Siler City (?)
in North Carolina. We had sprayed going downgrade on one leg. When we tried to reverse , the just sat and spun the wheels! After much head scratching, the brakeman suggested connecting the control hoses for the nonexistant trailing units to the hoses that would operate the sanders if our unit had been the traiing unit. At last we could go home!

[Anonymous]

What is a drawbar conection? Was it very common to run ABB or AB providing an even more streamlined look?

[Anonymous]

A drawbar is a solid bar that replaces the couplers between two semi-permanantly attached units. As others have mentioned, they were used in TR units, between the controlling switcher and the booster (or B-unit).

You can see them now in 3-unit 53' stacker sets (not the articulated units, but 3-unit sets). You can also see drawbars on triple-53 TOFC units, where a pair of TOFC cars carry 3 53' trailers, with one straddling the two cars.