What determines the set up of engines on any given train? I’m grasping the horsepower per ton ratio, but the more pics I look at the more different combinations I see. Forward A/reverseA, ForwardA/ForwardA, standard ABA, ABBB, 2forward, one reverse, 1forward/2reverse, on and on and on. I’m sure there’s a method to the madness, but I sure don’t know it!
Also (I hate to admit) What kind of transmission set up do they have that I assume allows them equal power forward or reverse?
The individual unit doesn’t “care” which direction it is facing, but the crew cares about which direction the lead unit faces.
So in a lot of cases it is probably just the way they happened to be facing. Why turn the units if it is not necessary?
If a loco consist is to be kept together it is most convient to have an “A” at each end facing in opposite directions. This was the “standard” in the earlier days.
One reason to purposely put two “A” facing the same direction in a train is avoid having to turn one if they are scheduled to take separate trains further down the line.
The diesel engine powers a generator which sends electric to motors on the axles. THe electric motors do the work. Electric motors obviously can easily give equal power both directions.