FT "AA" sets versus "AB"

After testing the 103, ATSF management desired self-sufficiency for all units. EMC discovered the biggest challenge was in locating a standard coupler at the end of the A unit as the trucks were positioned virtually flush against the rear. The standard FT A-B drawbar was mounted above wheel height, providing ample clearance; however, in order to guarantee compatability with established standards, the thicker coupler shaft required more generous clearances. An ingenious arrangement was created whereby a coupler with an "S" shaped shank was installed. The shape of the shank enabled it to clear the traction motors so as not to interfere with the mechanical workings of all parts of the running gear. As a result of this modification for ATSF, you'll see pictures of the road's FT units in configurations not seen on most others.

I hope this helps.

Bob

Whenever I run two-engine combinations (note, I did not use the L-word) of F or E units, I much prefer AA to AB, even if the AA was not prototypical.  I don't really know the reason, although I think CNJ3676's explanation is the answer to why: I have heard that story in much those details before and it sound right. 

Regardless, as a kid, maybe five or six, I recall being very intrigued that the trains we took all had a loco pointing backwards as well as forwards.  Wrongly, I figured it was so an extra engineer could sit and watch the train behind to make sure all was okay.  I do not recall if I ever actually same an AA unit on either the ATSF or D&RG (the two RRs I rode alot as a kid) of it they were always ABA, ABBA, etc.  But whatever the reason and whether prototypical or not, an A unit looking back is just something I always do on my layout.  Always.  No AB, ABB or ABBB configurations, ever: only AA, ABA, ABBA.

I have to admit, I with Lee, I like the A-A, A-B-A, or A-B-B-A combos, and I don't have any A-B combos, they just look "incomplete" to me.

Funny, when I was a kid I had just the opposite view - an AB unit formed an integrated, streamlined whole with the passenger train behind it, while a trailing A unit interrupted the line. Now I usually run ABA or ABBA units, because it's prototypical or that's the way the engines come out of the box - but I still like the more flowing look of an AB(BBB) set with a passenger train behind. 

Although I like both combos, A-A and A-B, or the other variations thereof (A-A, A-B-A, A-B-B-A), I prefer the look of an A-B combination best.  I can't really explain why, but it just looks more aesthetically pleasing to me.

I read some where....ATSF passenger F series locomotives always had a "B" unit in consist because the steam generator was located there in. The "A" unit did not have a steam generator! BUT...I can not back this up, only a recall of memory.

Rick.

That's correct Rick.  Only the B units had steam generators.  The reason was that since all ATSF F units had dynamic drakes there wasn't sufficient water capacity in the A units for the steam generator.

Stuart

CentralFan

I would bet it is safe to say that at some point on "The System", it happened, AA F's and FA's happened, for one reason or another.

Rick.

I know I've seen enough real trains with A-A units to say they're prototypical in some circles.

I will have to side in terms of personal appeal with the ABBA combination. It is the best look for me.

This would be a good poll question.

New York Central's FT units remained in their semi-permanently coupled A-B configurations.

Bob