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Cajon Pass Triple-Tracking Updates (Plus Barstow-Daggett)

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Posted by K. P. Harrier on Saturday, September 27, 2008 8:25 AM

As of Friday, September 26, 2008:

Exciting Things

This contributor traversed Cajon Pass twice Friday.

About 6:30 A.M., the typical was found, i.e., scattered track equipment here and there on the new Track 2 between CP WALKER and CP CAJON.  As usual, the new cantilever signal structure adjacent State Route 138 between the above control points had Track 1's signals operational, but Track 2's signals turned away.

By 5:30 P.M., however, track equipment was congregated railroad west of CP CAJON, on the "Dead Track."

The area had been and was being well watered

The signals alongside S.R. 138 were ALL now facing forward and active.

Conclusions: 

Operationally, it is unknown if the new Track 2 between CP WALKER and CP CAJON has been released for service or not, but it could very well have been.  With track equipment now off the above main and gathered railroad west of CP CAJON, the great track realigning ‘around the curve from CP CAJON' could very well take place this coming Monday.  Time will tell ...

Track identifications in above photo:

Foreground, from left to right:  Track 3; the dead track (future Track 2, the old "South Track" of years ago); and Track 2 (the future Track 1, the old "North Track")

Background, from left to right:  Tracks 3, 2, and 1 (presently nearing the end of construction)

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by passengerfan on Thursday, September 25, 2008 10:09 AM
 CSSHEGEWISCH wrote:
 JSGreen wrote:
 Paul_D_North_Jr wrote:

- The upper photo just invites a "Submit your funniest caption for this photo !" contest, doesn't it ?

My submission: A RR as designed by congress...

Remember that Congress was elected by US!

What fools we be at times.

Thx KP it doesn't look like it will be long now before their is triple track fully in place.

Al - in - Stockton

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Posted by CSSHEGEWISCH on Thursday, September 25, 2008 8:59 AM
 JSGreen wrote:
 Paul_D_North_Jr wrote:

- The upper photo just invites a "Submit your funniest caption for this photo !" contest, doesn't it ?

My submission: A RR as designed by congress...

Remember that Congress was elected by US!

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by K. P. Harrier on Thursday, September 25, 2008 8:51 AM

As of Wednesday, September 24, 2008:

Westbound of CP CAJON:  The realignment

Since yesterday's report, NO new work on the three-track realignment appears to have been done

Perhaps such realignments are accomplished on Mondays and/or Tuesdays when the least amount of traffic would be disrupted.  On the triple-tracking project, generally, at least one track is always open for traffic during realignments

Eastbound of CP CAJON

Work continued between CP CAJON and CP WALKER into late afternoon, and much equipment and personnel was used. 

Tractors were shuttling ballast from a pile where the 2.2% and 3% lines split to locations near Sullivan's Curve and the Mormon Rocks.  To get to their destinations, a long, circuitous dirt road route was taken. The tracks on the lower right loop around to where the tractor and dust are at

Sometimes dust was everywhere!

Ballast has become high in some spots.  The yet to be put in service Track 2 is the middle track.  (Westbound, photo left; eastbound, right)

But, a few hundred feet away, almost to CP CAJON, notice how the same track here lowers from right to left, and needs another dropping of ballast underneath it 

BNSF Railway (and its predecessor, AT&SF, i.e., the Santa Fe) has long desired an additional 2.2% track over Cajon Pass to overcome the often bottleneck conditions there caused by the limitations of the 3% line.  With work on the four- to five-mile CAJON to WALKER section nearing completion, the dream is on the verge of finally becoming a reality!  Train movements will then be so much more fluid on the pass.  Afterwards, it shouldn't take long to put the final touches on the six- to seven-mile CP KEENBROOK to CP CAJON section (very top realignment photo)

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by JSGreen on Wednesday, September 24, 2008 7:11 PM
 Paul_D_North_Jr wrote:

- The upper photo just invites a "Submit your funniest caption for this photo !" contest, doesn't it ?

My submission: A RR as designed by congress...

...I may have a one track mind, but at least it's not Narrow (gauge) Wink.....
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Posted by Paul_D_North_Jr on Wednesday, September 24, 2008 9:49 AM

Hey K.P. -

First, thanks once again for your efforts in following this, taking the photos, and posting them with the comprehensive comments so frequently.  It really is a lot of fun to watch this great project move along, and I know that it takes quite a bit of time.  I'm not aware of any other similar resource available to the railfan community, so we're all indebted to you for this opportunity to participate vicariously, as it were.

With regard to your latest pair of photos:

- Jeez, that's nice looking track !

- In the lower photo, notice the off-tracked track machine (sorry, can't quite tell what it is) on the right side of Track 2 - it's sitting on the ballast "wing" just beyond the shoulder.

- The upper photo nicely shows the start of the track "cuts and throws".  Will you be able to get out there again, as each step of that process occurs and build a portfolio of the sequencing of that ?  It sure would be interesting. 

- The upper photo just invites a "Submit your funniest caption for this photo !" contest, doesn't it ?

Thanks again.  Looking forward to more of the same in the future.

- Paul North.

"This Fascinating Railroad Business" (title of 1943 book by Robert Selph Henry of the AAR)
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Posted by K. P. Harrier on Wednesday, September 24, 2008 9:05 AM

Update as of 6:00 P.M. Tuesday, September 23, 2008:

West of CP CAJON, Track 3 has been completely realigned, and is now in service

East of CP CAJON, the new Track 2 is still out of service, but progress is coming along nicely.  From left to right, Tracks 1, 2, and 3

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by anb740 on Sunday, September 21, 2008 7:27 PM
 Clutch Cargo wrote:

Why are there no bullet holes in that "No target shooting sign" ?

If that sign were located down here in south GA. redneck country, you wouldn't even be able to read the sign for all of the bullet holes!  Laugh [(-D] Laugh [(-D] Laugh [(-D] (same goes for the "no off road vehicle signs....although those would be shot first, and then run over by four-wheelers!)

Joe H. (Milepost S256.0; NS Griffin District)

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Posted by Clutch Cargo on Sunday, September 21, 2008 9:35 AM

Why are there no bullet holes in that "No target shooting sign" ?

 

Kurt 

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Posted by Modelcar on Saturday, September 20, 2008 12:26 PM

......Enjoyed the update....K P.

Quentin

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Posted by K. P. Harrier on Saturday, September 20, 2008 10:18 AM

Update as of Friday, September 19, 2008:

Railroad east of CP CAJON:  This section's new rails and ties are in place now.  It shouldn't be long until trains are traversing the new Track 2 between CP CAJON and CP WALKER

Looking westbound

Check this wiring out!  Small white painted rail area indicates this new track is 141 pound rail

The dirt road's barricades have been removed.  Cajon Blvd. has long ended at a loose cul-de-sac with a dirt road going down to and crossing the tracks

A Word of Caution for Visitors!

There are reports that the roadway area above is now off limits to non-railroad employees and contractors.  People walking down to the tracks are now even chased away, though the longstanding posted signs seem to contradict what security forces are doing

The dirt road grade crossing was once popularly used by hikers, hunters, motorcyclists, and other dirt roaders

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by K. P. Harrier on Wednesday, September 17, 2008 9:02 AM

Update as of Tuesday, September 16, 2008:

The CP CAJON area:

The popular dirt road at the end of Cajon Blvd. is now barricaded.

The new Track 2 is coming together quickly now

The short section of Track 2 is in various stages of being laid

Track 3's realignment is clearly seen in this eastward view

A westward perspective

All east facing signals of CP CAJON are now operational

All the west facing signals are also now active and facing forward

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by K. P. Harrier on Sunday, September 14, 2008 9:57 AM

Update as of Saturday, September 13, 2008:

An east to west report

Railroad west of CP WALKER (around M.P. 60.0X) looking east toward the double-crossovers

Looking westbound:  New Track 2 (left) is now highly raised with ballast and well manicured

Immediately west of the State Route 138 overpass looking railroad east

From CP WALKER the refining work of the new Track 2 (right) abruptly ends in the vicinity of M.P. 64.0X (near M.P. 62.0 on the just out of view Track 3 on the photo bottom) just west of CP CAJON.  Ties have been laid out in preparation for closing the gap between here and CP CAJON (toward photo left)

Light gray ballast (in contrast to the present pink hued ballast) has been spread out in preparation for Track 3 being alignment shifted

After Track 3 (nearest on the right) is alignment shifted (to the nearest track on the left), the track next to the tamping equipment will be dragged over to follow adjacent Track 1's alignment on the far right and meet up with the fourth photo's abruptly ended track

The future Track 3 (lowest track) at CP CAJON is quickly coming together

Looking eastbound at CP CAJON:  After removal of the old signals and control boxes, the third track has been laid between signals, and extends railroad westward on the lower photo left

View looks westbound.  This is the location of the future great realignment shifts.  If one looks closely (chick on the photo to enlarge) the track on the far left starts to curve into the distant Track 3 but abruptly ends.  The future Track 1 is on the far distant right.  Daring graffitists must have used ladders and consumed much time in their efforts on the lower right

Looking railroad east from the Swarthout Canyon Road grade crossing at M.P. 64.6

Looking westbound:  The new track here (between CP CAJON and CP KEENBROOK) is not as refined as that between CP WALKER and CP CAJON.  As evident in this photo, much straightening and leveling still awaits this new section of track

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by K. P. Harrier on Tuesday, September 9, 2008 4:41 PM

As of Monday, September 13, 2008:

Various track work was noted between CP WALKER and CP CAJON.

In this view, equipment was working between signals at the new CP CAJON on the newly laid Track 3

Railroad west of CP CAJON new track still has NOT been laid the half mile or so to where the future major realignment shifts will take place.  Neither east of CP CAJON has the quarter mile section of the new Track 2 been laid to meet up with Track 2 from CP WALKER in the east.  Scattered track work was taking place on the new Track 2 from CP WALKDER and CP CAJON

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by K. P. Harrier on Friday, September 5, 2008 10:49 AM

Update as of 4 P.M. Thursday, September 4, 2008

Three-Tracks Come to CP CAJON

Between signals, i.e. between the west and east ends of the interlocking, the new Track 3 has been laid and ballast dropped onto it.

The west end of CP CAJON:  Track laying has stopped just railroad west (left) of the signals

This ballast is dumped and immediately spread

Many workers are working on this newly placed crossover.  For months this crossover's turnouts had remained uninstalled because of old signal boxes in the way

The ties and rails lower as they come off the short creek bridge, and will need a second dumping of ballast to bring the rails up to a uniformly level

Project trucks are still busily going every which way.  It is like watching a bunch of ants at an ant hole.  CP CAJON is adjacent to freeway on and off ramps.  The steep Track 3 from the distant background (center) is STILL aligned to Track 2 (middle track on left).  The east signal structure is in the middle background

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by Nataraj on Friday, September 5, 2008 12:46 AM
thanks for the great pictures! Its been fun following the construction
Nataraj -- Southern Pacific RULES!!! ------------------------------------------------------------------------------------------------------------- The GS-4 was the most beautiful steam engine that ever touched the rails.
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Posted by blue streak 1 on Wednesday, August 27, 2008 12:13 PM
PAUL:  Great work. I don't know if you would have time but a complete track diagram with all crossovers shown might help those who go there. I know if I could go it would help but I'm not able for at least a couple years. Keep up the good work!
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Posted by Modelcar on Wednesday, August 27, 2008 11:25 AM

....Enjoying the updates from K P.  Thanks.

Quentin

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Posted by K. P. Harrier on Wednesday, August 27, 2008 8:59 AM

Update as of Tuesday, 5:00 P.M., August 26, 2008:

CP CAJON was pretty much cleaned-up from all the activity Monday, with scattered pieces of equipment here and there.

Between CP CAJON and CP WALKER, particularly around the State Route 138 overpasses, seemingly westward equipment was parked on Track 2 with the new track behind it (eastward of it) quite manicured.

Follow-up to Monday's Report

After Monday's MORNING visit previously posted about, a second visit was made in the AFTERNOON ...

Is this a brief, super hot rail welding job?  The as yet unpaired new crossover turnout is just right of the flames

In the morning, a crossover existed here, but no more.  With the old signal boxes now out of the way, new grading for the third track is taking place

A tractor scoops-up "light gray" ballast at the railroad west end of CAJON.  "Pink" ballast is also present on far left of the pile

The tractor is now carrying the ballast to the railroad east end of CAJON

The removed old turnout

A straight-on view of the railroad west end of CAJON ... With the crossover on the lower left now half removed, CP CAJON is on its way to being Burlingtonized.  BNSF's distant predecessor Burlington Route (CB&Q) of years ago was famous for its Chicago-Kansas City line's triple-track, with control points having FOUR crossovers.  That line, however, is NOT hindered by the restrictions of a 3% grade for one track like Cajon Pass is.  (In the far BACKGROUND, from left to right, are Tracks 1 and 2 [2.2%], plus the future realigned Track 3 [3%]).  In this poster's opinion, BNSF, after a few years of dispatcher fluidity complaints and perhaps feeling it has NOT fully got its money's worth on the triple-tracking at CP CAJON, will probably restore the fifth crossover.  In the far background, a couple of remote helpers assist an eastbound up the 2.2% Track 1.

Equipment reported in the morning as being on the far side is now, in the afternoon, on the Cajon Blvd near side

Tractors shown earlier had dropped their loads on future Track 3

Close up view

A memo to Paul North:

You are absolutely right in your August 25 post about the below equipment NOT being a tie laying machine!  I don't know what I was thinking.  Thanks for the correction and setting the record straight!

K.P.

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by passengerfan on Monday, August 25, 2008 3:59 PM

Thanks KP for the latest photos and thanks also to Paul for an explanation of the critters. It definitely looks like someting big is going to be taking place on Cajon before the long weekend.

Al - in - Stockton

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Posted by Paul_D_North_Jr on Monday, August 25, 2008 3:48 PM
 K. P. Harrier wrote:

Update as of 7:00 A.M., Monday, August 25, 2008:  Something Is Brewing!

Equipment is still being assembled and travels by, as the eastbound facing manned tie laying machine warms up in the background

The above is a track tamper - probably a Jackson Torsion-Beam type, though I'm not in that business enough anymore to be conversant with the specific model.  Note the gray tamping tools hanging down, about 5 feet in front (to the right) of the rear wheel (to the left).  The aluminum buggy (and same color wheels) that carries the projection lights - used for grade/ elevation/ raising (and sometimes alignment) reference - is still attached to the front (right end) in the "travel mode", with the yellow spacer bars and supporting wheels stored in the folded position - note the two very small yellow wheels above and to the right of the front main wheel.  The "shadowboards" that restrict the light's path are in the middle-top of this machine - one is the horizontal black shape with the horizontal slit in it near the top of the tamper, almost directly above the tamping tools.  The light receiver is hard to see - it should be behind (to the left of) the shadowboard, at about its height.  It would be great to get a photo of this critter in it's stretched-out operating condition, and - is it too much to dare hope for ? - a video clip showing it going through its cycle of move-forward, clamp-the-rails, raise-to-grade, tamp-with-several-insertions, release-the-rails, and repeat, all of which should not take more than 20 to 30 seconds, typically.  Anybody able to do that ?  I don';t think one exists yet on the Interenet (at least not that I can find).

The above is a ballast regulator.  Note the center plow on the "front" (right end), the wing plows folded up against the side in the middle, and the sweeping broom at the rear (left end).

A rail travel capable roadway vehicle waits on the sidelines

Oh wow - great catch !  This is the rarely seen in the wild "Holland Mobile Rail Welder" !  Contained within that truck is an engine, generator, and all the gear to make electric flash-butt welds between rails at any location in the field.  There's a I-beam and trolley-type hanger near the roof that the welding head hangs from, and which extends out the back and can be moved to weld in either rail.  It's ideal for turnout installation and new track closure projects such as this one - much faster and better quality welds than the usual "thermit"-type welds commonly used in such circumstances.

 Yep - with this assemblage of equipment "SOMETHING'S DEFINITELY BREWING !"  Thanks much again for sharing these photos.  Hope you get to see and take more photos of the completion of this project.

- Paul North.

"This Fascinating Railroad Business" (title of 1943 book by Robert Selph Henry of the AAR)
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Posted by K. P. Harrier on Monday, August 25, 2008 12:20 PM

Update as of 7:00 A.M., Monday, August 25, 2008:  Something Is Brewing!

A good size assemblage of personnel and equipment has taken place at CAJON.  A double-stack heads eastbound (rightward) as Amtrak #3 heads westbound to Los Angeles (leftward).

The area of the old main CP CAJON signal control box has been cleared, and the final two new switches still wait to be positioned

The old CP CAJON signals and electrical boxes have been gathered together

Old signal bases are piled-up, and now have pink markings on them

Equipment is still being assembled and travels by, as the eastbound facing manned tie laying machine warms up in the background

The new alignment for Track 2 is now clearly marked with stakes

A rail travel capable roadway vehicle waits on the sidelines

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by chad thomas on Tuesday, August 19, 2008 5:54 PM

Al, I can say CP Walker to CP Summit is in service. This was taken aug 2
from Hill 582 of a meet on the new track (new #1) and the old (new #2).

 

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Posted by passengerfan on Tuesday, August 19, 2008 10:25 AM

K P

Your tireless efforts on keeping the rest of us updated on the Sunset route and Cajon Pass are nothing short of magnificent.

Any indication when the Cajon Pass triple tracking will be completed?

From the looks of things it doesn't look like it will be to long before trains are operating on the new track. I still marvel at how fast they daylighted the tunnels and removed all of that rock. Do you know if they reused all of that rock on sight or hauled it away. I see it looks like the new ballast going in is all crushed granite and limestone mixed. Makes for good drainage but is quite expensive. That would probably have had to be hauled in from Arizona is my guess.

Now we just need to find someone in New Mexico to keep us up to date with the double tracking through Abo Canyon. That will give the old Santa Fe a fast double track mainline between the Los Angeles Basin and Chicago.

Thanks once again KP.

Al - in - Stockton  

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Posted by Modelcar on Monday, August 18, 2008 9:54 PM

.....Good update photos K P....I like to bring up the photos and click on them to make them full screen and especially the strait track and the great panoramic view behind it all is almost like being there.

Enjoy seeing down the distance on that beautiful tangent track...!

Quentin

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Posted by K. P. Harrier on Monday, August 18, 2008 7:40 PM

As of Monday, August 18, 2008:  The New CP CAJON Is Up and Running

Extensive testing took place for hours during the cutover to the new control point signals at CAJON.

As testing winded down, the old signal at the railroad west end was taken down, battery boxes removed, plus an electrical box all were loaded onto a trailer.

Priority was given to removing items obstructing the laying of the third track

The east end signal was found to have already been relocated to a collecting area

The east end signals

Surveyors were out staking out the alignment for the future Track 3

An east end overview

The old signal and items previously at the west end were transported to the collecting area at the east end of CAJON

----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.

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Posted by CNW 6000 on Tuesday, August 5, 2008 3:50 PM
 Paul_D_North_Jr wrote:
 CNW 6000 wrote:

Question: Why are concrete ties lower in the center than the sides?

Because they don't need to be - and we want them to be thinner, so they're not at as much risk of cracking/ breaking.

This is a very good question, and is deserving of a more through response than I have time for right now.  As a brief outline, though, and mostly for "monobloc" = 1-piece concrete ties:

 1.)  The design philospohy for almost all ties - even wood ones - is that the load from each rail is supported by the end of the tie that is outboard, and the first 15" to 21" inside the that rail only.  Perhaps surprisingly, having the middle of the tie provide support to the rail loads is to be avoided - that tends to break them.  Accordingly, many specifications for tamping the ties/ track expressly restrict the extent of the tamping to within the above limits.  (The long switch timbers in turnouts / switches and other special trackwork such as crossing frogs are an exception, as well as grade crossings - all of these are often tamped off for their full length.)  Further, if you've ever seen - or the next time you do see - a track tamper, note that there are no "toolheads" for the middle of the track - typically, in each "row" of tamping tools (for 1 edge or face of a tie) there are 2 tools for the outside of each rail, and only either 1 or 2 for the inside of each rail.  Nevertheless, a condition called "center-bound track" sometimes occurs, such as in muddy track (and other) conditions, where the track has settled so much that a significant portion of the load is being carried by the middle of the tie.  The result is that the tie breaks upwards - kind of like snapping a matchstick between your fingers - and a segment of track with a lot of center-bound broken ties looks much the same ! (a sad sight for the Roadmaster or Track Supervisor, though)

2.)  So, the middle of the concrete tie doesn't have to be - and isn't wanted to be - as thick as the ends, because it's not supporting as much weight as the ends.  While that's been tried in the past, I believe the consensus and experience is that the thinner middle designs perform better / longer within as much cracking and breaking.  Also, this is one of those situations in structural engineering where more is not always better - making the middle portion thicker or with the same uniform depth as with the ends gives the tie more strength, and thereby also gives it the ability to carry more of the load - and so it will, making it vulnerable to the center-bound condition described above.  Another (simplified) way of looking at this is that the load will follow where the structural shape leads the load to go.  So, the ends are thicker (kind of chunky) because that's where the load is being - and wanted to be - carried. 

In comparison, if you've ever seen the type of concrete tie commonly used in Europe (and maybe some places here in the US - I haven't though), their "form follows the function" a little more closely.  Typically, they are 2 large blocks of concrete ("dual-bloc" or "twin-bloc" ? - can't remember the proper term right now), connected by a comparatively thin pipe or piece of other structural steel shape of some kind.  The blocks of concrete carry the load from the rail into the roadbed - the connecting piece of pipe merely keeps the concrete blocks the proper distance apart to maintain correct gauge, it is obviously too thin to carry much weight into the roadbed.  Here in the US, it is simpler to just make the concrete tie a 1-piece casting of the same material, instead of the 3 pieces needed for the twin-bloc designs.

3.)  Finally, the rail-to-tie fastener system typically has to have a fairly long embedment distance for its "tail" or "root" into the concrete tie to provide enough pull-out resistance strength against the rail uplift forces, which leads to a thicker tie under the rail area where those fasteners are installed.

Hope this is informative and responsive to your inquiry.  If you want to know more, search around for some on-line manufacturer's literature or professional or government studies or reports (like AREMA [formerly AREA], Federal Railway Admin. or Transportation Research Board), etc.

- Paul North.

Exactly what I was looking for and in sufficient depth for my purposes.  Thanks a bunch.

Dan

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Posted by Paul_D_North_Jr on Tuesday, August 5, 2008 2:54 PM
 CNW 6000 wrote:

Question: Why are concrete ties lower in the center than the sides?

Because they don't need to be - and we want them to be thinner, so they're not at as much risk of cracking/ breaking.

This is a very good question, and is deserving of a more through response than I have time for right now.  As a brief outline, though, and mostly for "monobloc" = 1-piece concrete ties:

 1.)  The design philospohy for almost all ties - even wood ones - is that the load from each rail is supported by the end of the tie that is outboard, and the first 15" to 21" inside the that rail only.  Perhaps surprisingly, having the middle of the tie provide support to the rail loads is to be avoided - that tends to break them.  Accordingly, many specifications for tamping the ties/ track expressly restrict the extent of the tamping to within the above limits.  (The long switch timbers in turnouts / switches and other special trackwork such as crossing frogs are an exception, as well as grade crossings - all of these are often tamped off for their full length.)  Further, if you've ever seen - or the next time you do see - a track tamper, note that there are no "toolheads" for the middle of the track - typically, in each "row" of tamping tools (for 1 edge or face of a tie) there are 2 tools for the outside of each rail, and only either 1 or 2 for the inside of each rail.  Nevertheless, a condition called "center-bound track" sometimes occurs, such as in muddy track (and other) conditions, where the track has settled so much that a significant portion of the load is being carried by the middle of the tie.  The result is that the tie breaks upwards - kind of like snapping a matchstick between your fingers - and a segment of track with a lot of center-bound broken ties looks much the same ! (a sad sight for the Roadmaster or Track Supervisor, though)

2.)  So, the middle of the concrete tie doesn't have to be - and isn't wanted to be - as thick as the ends, because it's not supporting as much weight as the ends.  While that's been tried in the past, I believe the consensus and experience is that the thinner middle designs perform better / longer within as much cracking and breaking.  Also, this is one of those situations in structural engineering where more is not always better - making the middle portion thicker or with the same uniform depth as with the ends gives the tie more strength, and thereby also gives it the ability to carry more of the load - and so it will, making it vulnerable to the center-bound condition described above.  Another (simplified) way of looking at this is that the load will follow where the structural shape leads the load to go.  So, the ends are thicker (kind of chunky) because that's where the load is being - and wanted to be - carried. 

In comparison, if you've ever seen the type of concrete tie commonly used in Europe (and maybe some places here in the US - I haven't though), their "form follows the function" a little more closely.  Typically, they are 2 large blocks of concrete ("dual-bloc" or "twin-bloc" ? - can't remember the proper term right now), connected by a comparatively thin pipe or piece of other structural steel shape of some kind.  The blocks of concrete carry the load from the rail into the roadbed - the connecting piece of pipe merely keeps the concrete blocks the proper distance apart to maintain correct gauge, it is obviously too thin to carry much weight into the roadbed.  Here in the US, it is simpler to just make the concrete tie a 1-piece casting of the same material, instead of the 3 pieces needed for the twin-bloc designs.

3.)  Finally, the rail-to-tie fastener system typically has to have a fairly long embedment distance for its "tail" or "root" into the concrete tie to provide enough pull-out resistance strength against the rail uplift forces, which leads to a thicker tie under the rail area where those fasteners are installed.

Hope this is informative and responsive to your inquiry.  If you want to know more, search around for some on-line manufacturer's literature or professional or government studies or reports (like AREMA [formerly AREA], Federal Railway Admin. or Transportation Research Board), etc.

- Paul North.

"This Fascinating Railroad Business" (title of 1943 book by Robert Selph Henry of the AAR)
  • Member since
    May 2007
  • 64 posts
Posted by Warren Smith on Monday, August 4, 2008 5:13 PM
 Modelcar wrote:

...Boy, up close....one can see that really is heavy rail...!  It sure does make it difficult for me to see "how" they get new {or old}, rail as smooth and tangent as the in service rail in the first photo.  And of course I realize machines do most of it now...but how was it accomplished decades ago......?  Suppose by many strong backs and pry bars and someone's eye sighting down the ROW.

Quentin:

In a word: SURVEYORS (ask Mudchicken)Big Smile [:D]

Not the back-breaking "fine-tuning" part, but the set of offset alignment stakes every 25 feet ...

Warren

  • Member since
    February 2002
  • From: Muncie, Indiana...Orig. from Pennsylvania
  • 13,456 posts
Posted by Modelcar on Monday, August 4, 2008 6:36 AM

...Boy, up close....one can see that really is heavy rail...!  It sure does make it difficult for me to see "how" they get new {or old}, rail as smooth and tangent as the in service rail in the first photo.  And of course I realize machines do most of it now...but how was it accomplished decades ago......?  Suppose by many strong backs and pry bars and someone's eye sighting down the ROW.

Quentin

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