Class J's - trackworthiness? UP set up?

[nw-modeling-list at nwhs.org]

It would be interesting to see how UP sets up their track since they operate both steam and diesel more often than any other modern freight hauling rr. Not having drawings in front of me, I'm guessing that the Big Boy's rigid wheel base is approximate to the J's.
Charlie Long

-----Original Message-----

>From: nw-modeling-list at nwhs.org

>Sent: Oct 2, 2006 9:00 AM

>To: 'N and W Modeling List' <nw-modeling-list at nwhs.org>

>Subject: RE: Class J's - trackworthiness?

>

>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

>