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

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Posted by K. P. Harrier on Sunday, July 20, 2008 7:42 AM

Update As of Saturday Morning, July 19, 2008:

This Saturday westbound (leftward) ballast train between CP WALKER and CP CAJON is coming out from underneath State Highway 138.  Four photos herein were taken from up on the east (right) approach to this bridge

The train is moving very slowly while unloading ballast.

The last car's truck has a bar of some sort ahead of it smoothing the ballast at railhead level.

Four SD40-2's are leading the originally heavy train.  BNSF started unloading cars right behind the power, and continued until gradually the last car of the train was emptied.

The work train ran out of ballast near the midway point between CP WALKER and CP CAJON.

Where the 2.2% (photo top) and 3% (bottom) lines split just railroad east of CP CAJON (toward the left), many, many ties were found to have been offloaded from the tie train cars, and apparently will, in this vicinity, be manually positioned in the track laying process.

Is the yellow object spending a quiet weekend at CAJON a rail cutting device?

----------------------------------------------------------------------------------------------------------------------------------- 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 CShaveRR on Sunday, July 20, 2008 3:13 PM

The "bar" looks like nothing more than a crosstie chained to the car.  Was that the only car that had one?  If so, the remainder of the loads would have had to run a bit of a risk going over ballast above the rail.  I've seen the tie method used before, but only on small jobs where there was only one car involved--or one at a time.

UP's newest ballast cars have wedge-shaped steel plows inboard of the trucks; I presume they're mechanically or electrically lowered to help distribute the ballast when needed.

Carl

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Posted by Paul_D_North_Jr on Monday, July 21, 2008 11:42 AM

Probably not - these days, "rail cutting devices" = rail saws are usually circular saws with abrasive blades powered by chain-saw type engines.  For one example, see:

http://www.encentris.com/GEISMAR-TRACK-MACHINERY-METAL,i260259213483,c31481.html

Before that, Racine made one that was a gas-engine (Briggs & Stratton) powered hacksaw, with a huge saw frame - maybe 12" high x 24" long - that weighed about 200 lbs.

Actually, what you have here is 2 yellow objects - not just 1.  If you click on and enlarge the photo and then look closely, you'll see that these are 2 similar machines, stored side-by-side next to each other, facing opposite directions - note the high yellow handles (like a bicycle's) at one end facing outward, and the dark square object (the engine) at the other.  They look very similar to a Geismar / Modern Track Machinery tie borer or tie drill to me, but could also be a couple of other things - a better / closer photo would be needed for me to positively ID it.

Hope this is helpful.

- Paul North.

 K. P. Harrier wrote:

Update As of Saturday Morning, July 19, 2008:

[Portions of previous message deleted - PDN.

Is the yellow object spending a quiet weekend at CAJON a rail cutting device?

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Posted by rdamon on Monday, July 21, 2008 2:09 PM

Thanks for all the updates K.P.!!!!

Here is another shot of the tools....

http://railpictures.net/viewphoto.php?id=243440&nseq=48

 

Robert

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Posted by Paul_D_North_Jr on Monday, July 21, 2008 2:48 PM

Robert - Thanks for the link !  It is indeed a better view of the machines - but I barely see them - instead, I'm mainly seeing the BNSF train in the middle of the image leaning into the super-elevated curve . . .

As to the machines - I now doubt if they are tie borers or drills - I can't see the "pump handle" that should be between the "bicycle handles" and that is used to drive the drill bit downwards - kind of like the lever or wheel on a drill press.  Also, as this photo makes clear - what for would a tie borer - almost exclusively used on wooden ties and timbers - be needed on a track with concrete ties ?  Then again, a possible answer is in the background right of this image - note the wood ties, which on a bridge usually have a lot of things that need to be drilled - but here, it is a ballast-deck bridge, so none of that "stuff" is applicable.  So the mystery continues . . . I'll see if I can do some more research and identify them better (for the 2 or 3 of us that might really be interested).

- Paul North.

 rdamon wrote:

Thanks for all the updates K.P.!!!!

Here is another shot of the tools....

http://railpictures.net/viewphoto.php?id=243440&nseq=48

 

Robert

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Posted by K. P. Harrier on Tuesday, July 22, 2008 10:04 AM

Update as of July 21, 2208:

Remember this photo of July 11?

Apparently the machinery was only track maintenance equipment (unrelated to the triple tracking) and working westward on the Cajon Subdivision.  It returned and went past CP CAJON eastbound (photos right) yesterday, and worked up the 3% line towards CP SUMMIT.

Outside of the above, no discernable substantive activity was observed in Cajon Pass.

Some Questions Belatedly Answered ...

blhanel (7-7):

About "Hill 582" being assessable to the public ...

I have NOT been roaming around deep into the M.P. 58 area for 20 years, so I am unable to say if it is currently open to the public or not.

One of these days ... I hoped to do a thorough investigation of public access, trespass, and property boundary issues relative to Cajon Pass railfaning.  After such, I might have something more enlightening to share.

It is known, however, that much of the Cajon Pass land is under Federal jurisdiction, and to that fact even the traversing railroads recognize and yield to.

Modelcar (7-10):

About un-ballasted, new track lowering on each side of a grade crossing ...

An over 200-ton locomotive could theoretically snap or bend the rails in sudden, unsupported drops.  BNSF seems to lay ballast down on each side of a grade crossing to support the briefly sloping new rails.

Modelcar (7-12):

About trespass and my safety while documenting photographically Cajon's triple-tracking ...

 Modelcar wrote:

Recently, K P has recorded lots of the latest building process for us too.  I have no idea where he is when doing his photo work, and as an adult I hope he is using good judgment.  Enjoying his photos too.

All the photos are believed to have been taken from public property, including property which comes under Federal jurisdiction and open to the public.

I breathe safety.  In 1962, as a kid, I heard on the radio that new automobiles were going to soon then start being equipped with seatbelts.  I immediately saw the value in them.  In 1965, as a teenager, when my parents purchased and took deliver of a new car, I rejoiced that it came with those seatbelts.  At the dealership, when I was going to take my first ride in the new car, of my own initiative I pulled the seatbelt around myself and buckled it ... Years later, thousands and thousands of people entrusted their very lives into my care and judgments ... Need I say more?

Cajon Pass's Swarthout Canyon Road, while several signs said it would be closed at a certain time, was in fact actually open.  Many photos were taken at that time.  The next day, the road WAS closed ONLY at the grade crossing, and I respected that closure.

The picture that I've painted herein for you, Modelcar, is that I've tried to use good judgment.  But, I'll let you decide if I have or not.

Thanks.

CShaveRR (7-20):

About the bar smoothing out ballast ...

That last car was the only car I saw with something ahead of the rear truck's wheels, with that something lowering ballast to railhead level.

At the time, I was amazed to see ballast being laid and then steel wheels traversing over (or through) what was just laid.

The issue you posted about may explain WHY the ballast cars started to be unloaded right behind the power.  The lightest cars would always be ahead of the ballast pouring out of a railcar, while the heavy, loaded cars would have the shear weight force to deal with any ballast that might be on the railheads.

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 Modelcar on Tuesday, July 22, 2008 2:23 PM

....K P: 

Always enjoy and appreciate your update info and photos for us.

My comments of safety back in the posts you mentioned was simply a comment {supporting you and your info gathering}, and was a response to someone else that had kinda complained a bit of you tresspassing to get  photos, etc......Nothing else.

Quentin

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Posted by K. P. Harrier on Tuesday, July 22, 2008 3:41 PM
 Modelcar wrote:

....K P: 

Always enjoy and appreciate your update info and photos for us.

My comments of safety back in the posts you mentioned was simply a comment {supporting you and your info gathering}, and was a response to someone else that had kinda complained a bit of you tresspassing to get  photos, etc......Nothing else.

 

I know.  I appreciate all your kind words.   It is difficult to sound cheery after being up half the night taking care of loose ends.  When I do such dumb things, sometimes I simply don't know better until my body is falling asleep and it can't continue ... Ha, ha.  Anyway, take care.

 

----------------------------------------------------------------------------------------------------------------------------------- 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 Paul_D_North_Jr on Tuesday, July 22, 2008 4:49 PM

OK, K.P. and Robert, I think I've figured out what these "yellow objects" are, as I originally thought several posts ago:

They're most likely Geismar either AP21 or AP11 Rail-Mounted Clip Applicators & Extractors, for the e-clip and Fastclip, respectively, although it appears that the AP-21 can be fitted with different workheads for other designs/ makes of rail clips.  For a better illustration and a little more info, see the brochure / catalog page of Torrent Trackside (apparently a British track equipment rental outfit) at:

http://www.torrent.co.uk/equipment/pdf/tt_p21.pdf

Hope this is informative.  K.P., thanks again for your diligence in posting photos and responding to inquiries - again, it's most interesting, esp. for those of us that understand this but can't get out there easily to see this unique and massive project.  Please continue taking the photos - safely, safely of course ! (sounds like "Nicely-Nicely Johnson" in the musical play Guys and Dolls, if you know what I mean), and posting them for the rest of us to see as well.

- Paul North.

 K. P. Harrier wrote:

Update As of Saturday Morning, July 19, 2008:

[This portion of previous post omitted - PDN.]

Is the yellow object spending a quiet weekend at CAJON a rail cutting device?

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Posted by corwinda on Tuesday, July 22, 2008 5:32 PM
 K. P. Harrier wrote:
The issue you posted about may explain WHY the ballast cars started to be unloaded right behind the power.  The lightest cars would always be ahead of the ballast pouring out of a railcar, while the heavy, loaded cars would have the shear weight force to deal with any ballast that might be on the railheads.

K.P.

 I suspect unloading from front to rear is explained much more simply. When one car runs out they can start the next at that exact spot without having to back up. My 2 cents [2c]

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Posted by rdamon on Wednesday, July 23, 2008 5:46 PM

Thanks Paul!! I bet I can sure show up my neighbor with the new leaf blower if I pulled one of those out of the garage. Thank you for being so diligent in your research, I am sure there is some sort of support group for our type!!

 K.P. – As a former Hesperia resident I appreciate your trip back to the old turf where things like trees did not impede rail fanning!!

Robert

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Posted by CShaveRR on Wednesday, July 23, 2008 6:59 PM

Thanks, K.P., for your thoughtfulness in updating and answering everyone's questions.

Chad Thomas took my wife and me to Hill 582 in March 2007; there didn't appear to be any trespassing issues at that time, and we were far from the only fans in the area.

Now, as to the mystery tool, I still think it's a rail saw.  I've seen versions that are clamped to the rail being cut, and move back and forth while cutting using supports to keep the cut accurate.

Carl

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Posted by chad thomas on Wednesday, July 23, 2008 7:56 PM
 CShaveRR wrote:

Thanks, K.P., for your thoughtfulness in updating and answering everyone's questions.

Chad Thomas took my wife and me to Hill 582 in March 2007; there didn't appear to be any trespassing issues at that time, and we were far from the only fans in the area.

Now, as to the mystery tool, I still think it's a rail saw.  I've seen versions that are clamped to the rail being cut, and move back and forth while cutting using supports to keep the cut accurate.

Carl, Before I left the area in Sept. (and dureing the construction) I did get run off twice. Both times it was the same guy, a BNSF security guard, and both times I was absolutely not on BNSF property. This guy was obviously new and was a clueless idiot. The first time I was leaveing anyway and just said OK se ya. But the second time I asked him what his authority was and where the boundrys were and a couple other questions that he didn't know the answers to, actually he just plain gave me a line of BS. Well I was passing through anyway and decide to keep on moveing. I decided if I ran into this guy again I would stand my ground, but I ended up moveing away anyway so it never came to that. Also dureing severe fire danger they shut down that area also, too many idiots blow it for the rest uf us.

 

KP add my thanks for posting, sience I am not in the area anymore I really appriciate your contributions !!!! Thumbs Up [tup] Cool [8D]

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Posted by MadMike on Wednesday, July 23, 2008 8:12 PM
 Warren Smith wrote:

Brian:

Quentin is right - the telephoto effect shortens the actual length of that siding.  It is used when the helper DPU's disconnect at Summit and switch themselves over. They can either connect to the rear of a westbound for additional dynamic braking, or run down to Devore by themselves.

As to laying the prefab sections of rail and crossties on the ground. I'll pay closer attention next time a crew gang sets it up, but I think the equipment that grabs the rails, paddles the ballast and aligns itself to the forward sensor can do all that without damaging the track.  I'm sure Mudchicken or some specialist workers can address this more clearly ...

Warren

  Rails will be installed, then a tamper will come, align and level track to desired specs. Then ballast regulator will come in and dress the track up and make it look all Pretty!
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Posted by Paul_D_North_Jr on Thursday, July 24, 2008 5:24 PM

 CShaveRR wrote:

Now, as to the mystery tool, I still think it's a rail saw.  I've seen versions that are clamped to the rail being cut, and move back and forth while cutting using supports to keep the cut accurate.

Carl -

Did the rail saws that you've seen look like any of these ?

1.)  Arsco cart-mounted Rail Saw (image from H.T. Kegs Ltd., Kamloops, B.C., Canada - since it's not in ".jpg" format, it doesn't seem to show up as an insert below, so here's the link instead):

http://www.nvo.com/firekegs/pictures/view_alone.nhtml?profile=pictures&UID=10071

2.)  Reciprocating gas-powered hacksaw-type rail saw (image from the Isle of Wright Steam Railway Newsletter for 2003, entry for 5th January 2003):

3.)  Abrasive wheel rail saw, hydraulically powered - note the clamp to the rails and the swivel points at the "elbows" so that it can move and swing back and forth but still remains confined to a plane perpendicular to the rail (image from Railtech Australia Limited):

- Paul North.

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Posted by K. P. Harrier on Friday, July 25, 2008 7:44 AM

Where Is the Missing Crossover Switch?

It has been theorized that the mysterious ‘missing switch' of CP CAJON could come from a POSSIBLE near future track realignments at CP MARTINEZ ...

This is the site of the missing RIGHT handed CROSSOVER turnout at CP CAJON (foreground left, where Track 3 is yet unlaid):

The below picture is of CP MARTINEZ.  Note the old, as yet un-replaced, intermediate bidirectional target signals on the mast on the far foreground right.  It contrasts to the newer absolute tri-lights on the background left cantilever structure (and the dual tri-lights signal right of the telephone pole) governing a photo-unseen RIGHT handed turnout (Click on photo to enlarge):

Now ... Looking east at the WEST signals at CP SUMMIT ... West of SUMMIT (left foreground), the Tracks are (from left to right) 1, 2, and 3.  That is very simple and straight forward.

However ...East of CP SUMMIT, from background left to right, there is Martinez Siding, Tracks 1 and 2.

So, at CP SUMMIT, Track 1 in the west meetings Martinez Siding in the east, Track 2 in the west meets Track 1 in the east, and Track 3 in the west meets Track 2 in the east.  Is that tricky or what?

If BNSF realigned CP MARTINEZ, from west to east, Track 1 would meet Track 1, Track 2 would meet Track 2, and Track 3 would turn into Track 2 through a LEFT handed turnout.  And, at CP SUMMIT, Tracks 1, 2, and 3 in the west would meet Tracks 1, 2, and 3 in the east.

IF, and that is IF, that kind of possible realignment does in fact transpire, that sure would solve BNSF's track designation confusion at CP SUMMIT!  Also, if the RIGHT handed switch presently in place at CP MARTINEZ is in fact destined for CP CAJON, the transplanting of the turnout would solve the caper of the missing RIGHT handed switch!

Anybody know for sure?

----------------------------------------------------------------------------------------------------------------------------------- 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 rdamon on Saturday, July 26, 2008 3:14 PM

Interesting idea K.P. 

I would imagine that they have plans to extend the 3rd Main past the Martinez siding to Lugo and beyond. If that is the plan it probably makes sense to keep the alignment the way it is at Martinez as it looks like the ROW is prepped on the west side of the tracks past the switch.

Here is a good shot of the area.

http://www.railpictures.net/viewphoto.php?id=243436&nseq=15

Keep the photos coming!!!

Thanks

Robert

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Posted by Modelcar on Saturday, July 26, 2008 3:35 PM

.....That's an intetesting photo Robert.

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Posted by KBCpresident on Saturday, July 26, 2008 5:05 PM
I hope I'm not intruding here...Shy [8)] But I thought that BNSF was planning on abandoning the pass for some reason. But I really shouldn't be talking, since I can't remember where I heard that.

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Posted by KBCpresident on Saturday, July 26, 2008 5:06 PM
I hope I'm not intruding here...Shy [8)] But I thought that BNSF was planning on abandoning the pass for some reason. But I really shouldn't be talking, since I can't remember where I heard that.

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Posted by K. P. Harrier on Tuesday, July 29, 2008 7:44 AM

Update as of Monday, July 28, 2008:

The Missing Turnout Found!

Do you remember this CP CAJON missing switch location?

Apparently toward the end of last week the missing crossover switch was finally moved on site and installed (lower left)

A close-up view ...

The switch's motor.  The presently easy to see orange wiring piping will probably be below or at ballast level after the track is raised with ballast

Someone at BNSF went out of their way to mark this spot.  There appears to be an orange cover cap in the center

A long line of concrete ties are now stacked up at Cajon ...

... And laid out single-height also

Eating Crow

Ironically, last week it was suggested that the missing switch could possibly come from CP MARTINEZ (photo upper center left).  Yesterday, this contributor visited the site overlooking CP MARTINEZ where last week's linked photo was taken.  Looking eastbound at BNSF Railway's Transcon to Chicago, the turnout there is STILL in place and operational while the missing CP CAJON switch is missing no more as shown above.  For those unfamiliar with the area, the track in the foreground is Union Pacific's Palmdale Cutoff northward (left) to Tehachapi, Sacramento, Portland, and Seattle, which line here now splits away from paralleling the BNSF through the Pass.

The above photo location is easy to find and access.  The site has a noisy, crackling, high voltage, high-tension power line passing through with a large metal support tower there.

A westward view from that lookout:  The BNSF line between CP MARTINEZ and CP SUMMIT (direction lower left to upper middle right).  The steeper track on the far right is Martinez Spur (used as the mainline up until 1972).  It has parked on it a rare ex-Santa Fe center cupola caboose.

----------------------------------------------------------------------------------------------------------------------------------- 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, July 29, 2008 10:42 AM

Great update, thanks again KP.

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

Dan

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Posted by Anonymous on Tuesday, July 29, 2008 11:50 AM

 KBCpresident wrote:
I hope I'm not intruding here...Shy [8)] But I thought that BNSF was planning on abandoning the pass for some reason. But I really shouldn't be talking, since I can't remember where I heard that.

Nope. You're thinking of BNSF's Raton Pass. BNSF sold that to the state of New Mexico for their RailRunner commuter service. Cajon Pass is a very much used BNSF line, as it's on the Transcon which is the main BNSF Chicago-LA route.

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Posted by Modelcar on Tuesday, July 29, 2008 2:38 PM

....Thanks for continuing update K P.

Quentin

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Posted by KBCpresident on Tuesday, July 29, 2008 11:51 PM
 TrainManTy wrote:

 KBCpresident wrote:
I hope I'm not intruding here...Shy [8)] But I thought that BNSF was planning on abandoning the pass for some reason. But I really shouldn't be talking, since I can't remember where I heard that.

Nope. You're thinking of BNSF's Raton Pass. BNSF sold that to the state of New Mexico for their RailRunner commuter service. Cajon Pass is a very much used BNSF line, as it's on the Transcon which is the main BNSF Chicago-LA route.

Got it!Smile [:)]

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Posted by K. P. Harrier on Sunday, August 3, 2008 9:50 PM

As of Sunday, August 3, 2008:

Work crews were working this weekend.

A first layer of ballast was found to have been laid between CP KEENBRROK and CP CAJON.  View looking westbound from Swarthout Canyon Road

ALL three tracks at the Swarthout Canyon Road grade crossing, though wired, have NO insulated joints for the crossing gates there.  From top to bottom: Tracks 1, 2, and 3.  The new Track 1 only has an initial layer of ballast, hence, is presently lower than the rest and barely visible

From the CP WALKER to CP CAJON, the new track now has an additional layer of ballast.

From CP KEENBROOK eastward and CP WALKER westward, work seems to be headed for a convergence at 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 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.

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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 ...

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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
    December 2005
  • From: MP 175.1 CN Neenah Sub
  • 4,917 posts
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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