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Dallas rail heat problems

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  • Member since
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  • From: Georgia USA SW of Atlanta
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Dallas rail heat problems
Posted by blue streak 1 on Saturday, July 23, 2022 7:47 PM

RT&S  reports Dallas Dart light rail temps are reaching 150 F.  Report says CAT is sagging as well.  Brings up question constant tension CAT?  If constant tension was it so hot that the weights hit the ground or some stop on poles?  It may be a repeat of the problems Portland, Oregon had with their light rail when it got so hot last year.

Temps on rails in Dallas hit 150, forcing DART trains to slow down - Railway Track and Structures (rtands.com)

Have to wonder how the freight carriers around there are doing.

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Posted by CSSHEGEWISCH on Sunday, July 24, 2022 9:49 AM

I'm not surprised at the catenary but I would think that rail kinks would also be a major issue.

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 BaltACD on Sunday, July 24, 2022 6:58 PM

CSSHEGEWISCH
I'm not surprised at the catenary but I would think that rail kinks would also be a major issue.

I know nothing about the Dallas light rail operation.

Just speculating from afar, I suspect the highway grade crossing as well as whatever signal system they are running is keeping the segments of welded rail short enough that all the insulated joints that are requried for both crossing protection and signal system effectively prevent their welded rail generating sun kinks as the insulated joint give the rail a place to move when hot.  On the Class 1 carriers the segments of welded rail can approach three miles in length before coming upon a set of insulated joints.

Back in the days of jointed rail, having the rail run because of heat extremes was virtually unheard of.  There were rail joints every 39 feet and those joints could easily attenuate heat expansion of small fractions of a inch per rail length.  I have a MofW Rail Expansion Chart - a 1000 foot segment of rail is expected to expand 3 1/8 inches for a 40 degree increase in temperature.  5280 feet to the mile, three miles to a signal block -  15840 fee - equals 49.5 inches of expansion - over 4 feet - 4 feet of ENERGY that the entirety of the track structure is attempting to hold in place.  It only takes the slightest of failure to any one element of the track structure and you have a sun kink.

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Posted by Gramp on Sunday, July 24, 2022 11:32 PM

Would it make sense to incorporate at least some joints into the track structure to relieve the build up of expansion when temps get too high?

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Posted by azrail on Monday, July 25, 2022 2:38 PM

We have light rail in Phoenix and have no problems with sun kinks (or service delays) even with 110+ weather.

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Posted by Electroliner 1935 on Monday, July 25, 2022 9:07 PM

Most current insulated joints are epoxy glued and tightly bolted and have NO movement of the rails unlike the older fiber non-glued insulated joints of old. The glued joints are prefabricated and welded (thermite) into the long rails and can not relieve the stress. 

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Posted by BaltACD on Tuesday, July 26, 2022 12:45 PM

Electroliner 1935
Most current insulated joints are epoxy glued and tightly bolted and have NO movement of the rails unlike the older fiber non-glued insulated joints of old. The glued joints are prefabricated and welded (thermite) into the long rails and can not relieve the stress. 

The new insulated joints, when installed, have no movement.  After enduring multiple heat/freeze/thaw cycles by they hundreds and thousands they do develop movement.

Never too old to have a happy childhood!

              

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