Class J's - trackworthiness?

[nw-modeling-list at nwhs.org]

Far be it from me to challenge the accuracy and conciseness of Wikpedia and
any information available on the internet.........

 

In general in the steam days, tracks were configured for higher train speeds
due to the passenger trains present.  Once the late 1950's came passenger
trains were not run at the fast schedules previously.  A consequence of
diesels was that the track could be re-elevated to suit the slower 'freight'
type train speeds most common.  The shorter truck wheel base and the smaller
diameter of the wheels, 40" inches mostly, meant that climbing the rail was
less possible than a 70" or 80" driver on a steam locomotive.

 

Of course, the N&W used a compromised gauge and elevation to give the best
passenger train speed and practical freight 'ride' conditions at slower
speeds.

 

The dynamic 'pounding" of the steam drivers, no completely accurate
balancing being possible, tends to push the rail and bed out of 'spec.'
which meant that section crews were constantly adjusting the rail.  Smooth
passenger ride was important too also forcing more maintenance.  Of course
jointed rail needs constant re-tightening.

 

In general, steam locomotives perform better, that is maintain a higher
tractive effort with rail that is close to optimum, than with poor track.
This affects the gross ton mile performance of all engines and trains and
that is direct operating cost.

 

Changing over to a diesel fleet means that the MoW engineering can and has
to adjust the rail to suit the operating characteristics of diesels.  With
the drop-off of passenger traffic the upper end speeds are lower so track
elevation was decreased from steam days.  Rail gauge limits could be changed
(more or wider tolerances) as the longer frames of steam locomotives with
the drivers were gone.  But, these lateral stiffness issues had been handled
with blind drivers (no flanges) or lateral motion devices (axles shifting
side to side a little).  However these measures were more for tight
curvature than mainline running.  The reduced cost of track maintenance was
one of the advantages of going to diesels.

 

So the short story is that rail/track and the locomotive and the train is a
SYSTEM that has to be optimized through a number of engineering compromises
to keep the tractive effort high, keep the cars on the rail and keep
maintenance costs reasonable.  Running an excursion 611 on track optimized
for freight-only diesels means that the J is running on non-optimum
conditions.  

 

"Picky" is an oversimplification and implies something "bad" when 'not
designed for modern track conditions' would be more accurate.  Driving your
Toyota Corolla at 200 mph will introduce into the system a whole series of
aerodynamic effects that the car design cannot handle.  Does this make the
car 'picky'?

 

Track engineering is a field of its own.  It was in the steam days and it
still is today.

 

Gary Rolih

Cincinnati 

 

  _____  

From: nw-modeling-list-bounces at nwhs.org
[mailto:nw-modeling-list-bounces at nwhs.org] On Behalf Of
nw-modeling-list at nwhs.org
Sent: Sunday, October 01, 2006 12:53 PM
To: nw-modeling-list at nwhs.org
Subject: Re: Class J's - trackworthiness?

 

I'll take a shot at your question.  I read that N & W main line trackage was
re-gauged after the steam era ended.  This would have reduced the spread on
curves, no longer needed to suit the effective wheelbase of main line steam,
such as the J.  The accidents cited in the story took place in the 80's and
90's; suggesting that the J's might not have been 'picky'; but that they
were operating under 'borderline' conditions which did not exist 40 years
earlier.

 

Jerry Crosson

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