A and AE

[NW Modeling List]

Eric,

I have not personally heard or read anything to indicate the A was a
slippery beast. Both the A and Y6's factor of adhesion is less than 4, but
neither was considered uncontrollable. Part of that could also be the crews
being very well trained on their monsters, part of it the design and
execution of the locomotive as well. Some have suggested due to the A and
Y's low adhesion and not being slippery vs. the Pennsy T-1 having a high
FoA and being slippery that the rule of 4 might be more of a guideline, and
not set in stone.

I have heard of A's running fast (time) freights or merchandise trains
stopping at the bottom of the Blue Ridge and having a very hard time
getting the train moving again without pusher help, but not having a
problem moving these heavy trains at a good clip unassisted. Fast freights
on the N&W were run on a passenger train like schedule, and were usually
around 5,200 tons, needing very high speeds and power on the head end to
blast up most grades unassisted. The A was rated at 13,000 tons of slow or
'drag' freight Not sure if that helps answer the question or not. I also
have not heard of the H-8/AE being slippery either. I have heard they were
fairly easy locomotives to run. The H-8/AE was rated at 5,000 tons for
freight at 50mph, and they struggled to pull the 10,000 tons at slow speeds
that the C&O wanted them to pull in drag opperations (where they spent most
of their time). From the tonnage alone, it shows how the A bested the H-8
until 60mph, at which point the H-8 becomes the better locomotive.

The A and the H-8/AE were really two different animals. The A came first,
and the C&O asked Lima for a locomotive to best the A. They got the H-8
from Lima, but Lima did not fully understand what the A was meant for. The
A was a locomotive who could scream along at 70 mph+, but did her best work
at 30-40 mph. Right at coal drag top speeds, since this is what the N&W
needed/wanted. The C&O wanted a locomotive just like the A, and frankly the
H-8/AE did not deliver. Lima misunderstood the A, and assumed it was a high
speed freight locomotive like the Challengers. The H-8 makes its power at
high speed, just like the Bigboy and Challenger. However, in coal drag
service, this power is a waste, because it can not be reached (the H-8 and
AE both were used as drag locomotives). The H-8 was most successful hauling
heavy troop trains at high speeds during WWII (a role she was really
designed for) The C&O loved the H-8, the Virginian did not seem to like the
AE as much, shown by the very short lives they lived.

 As far as coal goes, all 3 locomotives ran on West Virginian Bituminous
coal, and would have been very similar in quality.

Some more people here will know more than myself, I am sure. Both were good
locomotives, just one was not used for what it was designed for.

Jon

On Wed, Feb 11, 2015 at 5:55 PM, NW Modeling List <nw-modeling-list at nwhs.org
> wrote:

>  I have been ruminating on a comment made in this forum several weeks ago
> to the effect that the N&W A was a superior engine to the VGN AE or C&O
> H-8, because the A produced more tractive effort with far less weight (and
> implied stress) on the track, despite the fact that it was an 8 year older
> design.
>
>
>
> The claim of higher tractive effort for the A surprised me, but is
> theoretically accurate based on boiler pressure (300 psi for the A vs 260
> for the AE and H-8), cylinder bore (24” for the A vs 22.5 for the AE and
> H-8), stroke (30” for the A vs 33” for the AE and H-8), and driver
> diameters (70” for the A vs 67” for the AE and H-8).  The net result is a
> theoretical tractive effort of 114,000 pounds for the A vs 110,000 for the
> AE and H-8.  Despite the larger drivers and shorter stroke, the A achieves
> its higher theoretical tractive effort through its larger cylinder bore and
> higher boiler pressure.
>
>
>
> But an (equally theoretical) analysis indicates that the A’s factor of
> adhesion was 3.44 (indicating a propensity to slip pretty easily), whereas
> the AE was 4.49 (indicating a VERY “planted” locomotive), and if the weight
> rumors of the H-8 were true, its (theoretical) factor of adhesion would
> have been a bit higher than even the AE.
>
>
>
> Both classes were designed to run at 70mph, but the design philosophies to
> do so were different.  The longer AE stroke and smaller diameters would
> have resulted in ~15% higher piston speed at any given speed, but the same
> dimensional differences would have resulted in ~15% lower static load on
> the main and side rods for a given tractive effort.  This and the ~18%
> smaller piston mass would have allowed ligher main and side rod mass and
> potentially easier dynamic balancing—thereby allowing the AE and H-8 to
> achieve the 70 mph design speed, even with 4.5% higher driver rpm than the
> A.
>
>
>
> I think it’s undisputed that the AE / H-8 design produced nearly 40% more
> horsepower than the A.
>
>
>
> So here are the questions I’m driving to:
>
>
>
> Did the A slip on starting?  Were the AE and H-8 notoriously sure-footed
> on starting?  Could either type start markedly heavier trains than the
> other under similar consitions?
>
>
>
> Could the A run any train at 50mph that it could start?
>
>
>
> Could the AG start any train it could run at 50mph?
>
>
>
> Did N&W and VGN operate the A and the AE over similar profiles at any
> given time (e.g., Narrows to Roanoke, or Roanoke to Norfolk)?  Did they use
> coal of approximately the same grade on these runs?  Did one deliver more
> ton-miles per hour, over similar profiles, with approximately equivalent
> quality coal?
>
>
>
> -Eric Bott
>
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