A, AA,AB or ABA?

Also would depend if you had a mountain type terrain to go over how many engines might be needed, you may need a helper engine for a large mountain.

Not all railroads had the same operating guidelines for the number of passenger cars, mostly the number of tons being transported. Pullman style cars verses heavyweight or vista dome passenger cars would have differant requirements.

The EMD website lists some of their engines and horsepower ratings, like the GP-39-2 or the SD-70-MAC.

ABA combo's are not used that much, more like two Genesis or FP45's.

Lee F.

An AA configuration would be used when a train couldn't be turned at the end of its' run but a run around siding was available. You could just cut the power and run around the train hook back up, do a brake test and head back to where you came from using the second a as the head power.

Ron

The amount of power assigned to any given train is dependent on the terrain to be covered and the speed required. A drag freight train in flat country might be dispatched with only 1 horsepower per ton, maybe even a little less. A fast passenger train going over the Rockies might need 8 to 10 HP/Ton. 

Some of the early E's and F's were coupled together back-to-back via a drawbar as opposed to a regular coupler. That didn't last long, because the railroads soon realized that a problem with ONE of the units took BOTH of them out of service.

An AA configuration would be used when a train couldn't be turned at the end of its' run but a run around siding was available. You could just cut the power and run around the train hook back up, do a brake test and head back to where you came from using the second a as the head power.

The Reading did this with their FP7s on the Cursader. They even went so far as to have an observation car at each end of the train.

Chris

LVHR

Other than horsepower or availability, another consideration was the capacity of the steam generating equipment and water-carrying capability. Some F units, particularly with dynamic brakes, had relatively small water capacity so they relied on a mating unit (A or B) for additional water storage.  FP7's were created to solve this problem.

GN is an example. The GN had a few dual-purpose A-A sets with steam generator in one unit and water tank in the other. So, both were always needed together on a passenger train, regardless of its length.  (These units generally saw service on secondary trains or short runs only; the gearing wasn't fast enough for transcon service.)

Some railroads thought they needed 6K hp for ALL trains.  so they bought ABBA F units.  But they found out many trains only needed 4.5K HP.  So they bought single F units, and broke up the ABBA sets into ABA sets.

Thanks everyone, I have a 6 car Milwaukee Road streamline consist. I'm going to pull it with F7 AA. I think an ABA would be overkill and I like the AA combo. Any votes for AB?

I like the looks of ABBA.  My Alaska and L&N both with 8 pass.cars look good to me. I go by more is better.  This on the NJ Hi-railers layout. 

Where did you get your track supports?

Chris,

A note about the 'original Reading Crusader' train, it was pulled by a 4-6-2 Pacific steam engine and not an FP7, in later years they could have used an FP7, not sure. The FP7 may have been used on the King Coal passenger trains to the Poconoes, or Scranton PA area.

You are correct about an observation car at each end, so that all they had to do was turn the engine around at a Y to hook-up to the other end of the train.

Lee F.

I have in F3's:

A:  Preamble Express (MPC)

AA:  2353 ATSF

AB:  2245 Texas Special

ABA:  Amtrak (MPC)

AA and ABA LOOK better!

Copy that:  There's hardly a better railroading sight, IMHO! 

As  I remember, The Pennsylvania Railroads first big order for the F3's were as ABBA sets. But the railroad quickly realized these 6000 HP sets were overkill for most freight assignments and most were then reduced to ABA, 4500 HP,  for work on the curve. There are plently of old movies of Enola yard action with ABA sets of EMD and Alco diesels on the point.

You ain't seen nuthin' unless you've seen the Chicago Great Western trundling through Bellwood with 6 F-units in A-B-B-B-B-A configuration on the point.

Rusty

The Western Pacific ran their leg of the California Zephyr with F3 A-B-B sets and later with FP7 A F7 B-B or some combination of the A-B-B consist.  Occasionally they ran an A-B-A consist.  Towards the end they really goofed up the looks of the CZ with a U30B and steam car.

Greg

JDA I Emailed you some info.

Paul..I don't think ABA would be an over kill.. think it would look neat!! aways seen A,B units pulling freight cars and ABA units pulling  passenger cars looked great!

How about three GG1's hauling a 125 car freight at 50 mph 

Close second!

Rusty

It was possible to fit a steam generator into an F-7A unit, but there was very little room for water. In a B unit, you had the area where the cab would have been on an A unit to put the generator and a large water supply. Most railroads only had steam generators in the B-units of the Fs. So you'd normally not see an F7A by itself, or two units back to back on a passenger train (except maybe a commuter train). A-B, A-B-A, A-B-B-A, or A-B-B would be more common.

I believe the Milwaukee did have some FP-7s, so two of them back to back might be doable??

Thanks all of you. It makes sense about the lack of space in an A unit.

Rusty

That was funny

Some RR's had water storage and/or steam generation in baggage cars.  I'm thinking NP, the Q, and UP here.

Lee,

You are 100% correct: the Crusader used shrouded Pacifics in the beginning. In fact, the tender had an extension piece at the top to maintain the streamlining effect over the first car (the wrong way facing observation). I'm not aware of any other railroad that did this.

After the RDG dieselized, they switched to pairs of FP7As. These had sufficient length to accomodate the necessary steam generators and water supply.

Chris

LVHR

ABBA?  No!!!  Do you realize years of therapy and I can't get that silly tune out of my head.

Take it easy, Fernando. Don't let this be your Waterloo.

Oh mamma mia....here we go again.

The second "B" is reversed in the band name!

In the steam to diesel transition era (when all the cab and booster units were actually purchased) you could see how a railroad provide different horsepower per ton for different purposes.  Maximum speed for streamlined cars was usually higher than for heavyweight cars.  Therefore, true streamliners operated at higher actual track speed than secondary trains.  Also, the secondary trains made more stops and their schedules were accordingly padded.  So, if the streamliner had to run at 79 MPH (or higher on some railroads) wherever there was enough straight track, it didn't matter if the secondary train lugged down to 60 on an occasional hill.

Higher horsepower translates to higher speed.  So, the schedule of the train and the maximum speed for the equipment and track were the determining factors for horsepower per ton requirement.  Minimum continuous speed of the diesel-electric locomotive units added a third factor in heavy grade territory (2% and greater), especially when EMD E units were the locomotives.

When I was in college there were many occasions when I used rail service to get between Raleigh and Jacksonville. This was during the Seaboard Coastline years. The train that best suited my traveling times was the Silver Star. They used E-units with usually three (3) A units connected elephant style.

Now here is a consist for ya!

BN GP38AC 2124
BN E-9A 9923
BN E-9A 9924
BN E-9A 9900
BN E-9A 9916
BN E-9A 9914
BN E-9A 9925
BN E-9A 9901
BN E-9A 9921
BN E-9A 9904
BN E-9A 9922
BN E-9A 9917
BN E-9A 9912
BN E-9A 9910
BN E-9A 9903
BN E-9A 9918
BN E-9A 9915
BN E-9A 9913

It would only be a consist if all the locomotives were MU'd together.  It's simply a non-revenue move of dead locomotives.

And, in case anyone's wondering, they're all facing the same direction because the locomotives all faced west in BN/Metra service.

Rusty

Like Dom, I have a few different configurations:

AA:

• MTH ALCo PAs
• WBB & Lionel ALCo FAs

AB:

• Lionel ALCo PA/PB
• MTH Baldwin Sharks
• Lionel EMD FTs & F3s

ABA:

• MTH EMD F3s

I do have a few spare FT-As, but since they didn't run alone, I don't.

There's a great shot in Greenfrog's NYC Odyssey of an ABBBA set of ALCo FAs.

Thanks,

Mario

Oh, I do have Alco PA/B:  ABA.  Did not mention because this was mostly about EMD's.

When diesels first arrived, there were labor issues over the difference between double heading verses MU.  Some roads got F units ABBA deawbar connected so it was clear that only one crew was required for the consist.

When diesels first arrived, there were labor issues over the difference between double heading verses MU.  Some roads got F units ABBA deawbar connected so it was clear that only one crew was required for the consist.

Good.  Nobody here is using the L***u* word!