Class J's - trackworthiness?

[nw-modeling-list at nwhs.org]

Mike:  No, the "basic question" is not really meaningful.

 

Balancing locomotive reciprocating/rotating masses cannot be done exactly by
mathematical means.  Even with computers, only an iterative solution is
possible (iterative = run the numbers and see what comes out).  A computer
run with a finite element approximation of the stiffness of all of the
related components- dynamic FEA- is possible, but would be an absolute
'bear' to set up as many assumption and many bits of information about
system response need to be known beforehand.  Basically, a couple of
specialist PhD's and a couple of pots-fulls of engineering test data would
need to be known to set up the problem today.  A super computer might be
needed to get the answer out in a decent time, too.

 

Assuming that the engineering staff could set up the problem using the above
model, the 'right' answer is still only applicable for a single speed.
Running slower or faster would take the J out of balance.  In addition,
there are sub-multiples and multiples of the various natural and running
frequencies of the systems and each of the components that will influence
the resulting amplitudes of the dynamic forces.  One runs the empirical
model with different conditions, looks at all of the results and then
decides how to specify the track in a way to work over most of the operating
conditions and sets speed limits for those spots where the compromise answer
won't work. 

 

In the 1930's-1940's balancing was an art and was done with empirical
formulas (empirical= making equations that simulate observed real
performance) that were developed over years of steam locomotive development.
These practices were published but were not followed by the N&W design
staff.  They felt they had a better method.  As the J did run up to 110 mph
(+?) on the PRR on test with 70" drivers, it is clear that the N&W staff had
it near right or was lucky (or both!). 

 

The MoW guys had to take the performance of the entire locomotive fleet and
the probable trains and come up with a compromise for the configuration of
the track that would allow useful and profitable motion of trains.

 

The N&W 'system" then is a number of assumptions, engineering
approximations, and 'fudges' concerning, loco's, trains and track.

 

So, is the J more or less sensitive to track conditions than the average
4-8-4?  If we put a J on the Sante Fe, a heads-up railroad concerning fast
running, what do we use as a measurement of 'better' or 'less better'
performance.  More or less derailments, more or less broken rail, more or
less track maintenance, more or less locomotive maintenance? 

 

Well, you'd really have to borrow some Sante Fe 4-8-4's and run them on the
N&W.    BUT, the two have different driver diameters and different valve
action and cut-off's.  So they aren't really comparable.  If I had to write
a comparative report to N&W management, I'd have to put in a lot of ''buts
and however's".  

 

This illustrates one of the real hassles of engineering, comparing two or
more complex systems that were created using empirical engineering with
numerous connected assumptions is very, very difficult.  Even with computer
modeling today, this is very, very difficult and very expensive.  After some
expensive failures, the Pentagon still gets prototype aircraft built and a
competitive fly-off made before choosing one to proceed with.  

 

The best answer is to look at the railroad's operating ratio to compare its
gross income to the operating expenses necessary to transport all of the
goods needed to generate the income.  It is probably the best lumped
parameter to give an estimate of performance.  The N&W's operating ratios
were good!

 

Another way is to have some engineering or physics background and see that
"picky' is a pretty vague term.  Looking at balancing, one can estimate that
if a loco has balancing problems, it will cause high dynamic loading on the
locomotive running gear and/or the rail.  From what we know or hear today,
the J didn't break rail and didn't cause high rail wear (that has been
reported in a report we know off), didn't have any "gross" speed
restrictions to force operations to slower speeds.  They didn't seem to have
much problem with rods or pins or lubrication.  Most of the know J wrecks
were caused by tip-overs on curves or cross- overs where the engineer
exceeded the speed limit (as far as it could be determined at the time).
And these wrecks were at higher speeds- not 35mph!

 

Dynamic forces can spread rail, but generally these forces will break rail
or bend it over through the web before affecting the rail, spike and tie
system.  Doesn't seem to have occurred all that often with J's.  

 

Kinda seems like we can say that J's probably weren't picky.

 

We have a number of preserved records on wrecks or incidents with Class J's,
what about the K-2's?  How did they perform?  I have never seen anything
about these.  

 

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: Tuesday, October 03, 2006 7:17 AM
To: N and W Modeling List
Subject: Re: Class J's - trackworthiness?

 

Wow, sort of a heated discussion.  I was surprised to see the comment on
Wikipedia, and that is why I asked it here.  It is a fact that the J's
drivers and counterbalance system were pushing the envelope of technology
and material for the time. So it isn't really a stretch to think there could
be some truth to the comment.  But, Gary is right, that track standards were
different then.  Noticeably so.  But the basic question remains, were the
J's pickier about track-work than other steamers?  Did they have lateral
movement in the drivers?  Did other N&W engines, like the Y's, have it?
Y3's or Y6b's?  I'm guessing that didn't exist in the early 1900's when the
Y's were coming into being.  

It's funny... even our models have lateral movement in the drivers to help
with trackwork. 

Mike Rector

nw-modeling-list at nwhs.org wrote:

All,

 

You should know what wikipedia is.  Wikipedia is basically a web blog.  The
content is all from users.  You can edit the entries.  If there are errors
of fact a person can go in and change the entry.  There is also a disccusion
board feature for each entry were editors discuss the content of that
article.  So if someone has time to work on the article they should. 

 

It is okay to challenge,

 

John Rhodes

 

On 10/2/06, nw-modeling-list at nwhs.org <nw-modeling-list at nwhs.org
<mailto:nw-modeling-list at nwhs.org> > wrote: 

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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