mudchicken Pandrol Clips, D-E Clips and the like act as heavy springs.
Pandrol Clips, D-E Clips and the like act as heavy springs.
That's what I suspected, thanks for confirming that. Makes me wonder if there were some process for minor re-shaping to bring back the "as-new" spring pressure, thought it's probably cheaper to melt them down and start over than doing a thorough enough job looking for defects.
Pandrol Clips, D-E Clips and the like act as heavy springs. They do lose some of their spring tension after cycling through expansion/contraction cycles along with wear on the contact face (clip and web) along with how they connect at the plate. Takes a little longer, but the rail will "run" as the friction lessens.
MC, you've piqued my curiosity. What are the circumstances that would lead to replacement of the Pandrol clips? Does the wear out process involve wear (as in material being removed) or the clip not retaining shape?
As for track shifting under contraction, I remember seeing the curves on the loop line at OERM in Perris shift inwards on early summer evenings as pointed out by Paul Hammond.
It does not take much for rail to react.
Bigger question for this exercise is the tonnage history of the rail in-service, how well is the rail anchored and how effective are the anchors?
ie- what condition is your track in? Temperature swings are usually felt first where the track condition is worst. Keeping track sufficiently anchored with effective OTM remains a constant headache. Now we are seeing an increase in worn out Pandrol Clips, DE Clips etc that is adding to the "fun" as they were supposed to help cut down the number of anchors required...
Given that the rail shrinks in cold weather, kinks aren't really an issue.
Pull-aparts and broken rails are.
The bolts in a joint may be sheared as the rails shorten up in the cold. That's when you see the "fire snakes" come out, to heat the rail so the bolts can be replaced.
The shrinkage may also reveal a flaw in the rail, causing a break. That's usually going to involve replacing a chunk of rail, probably welding a new one in place.
I've never heard of track re-aligning due to cold (ie, stringlining), but that may be simply because I've never heard of it. I would opine that such an event would tend to indicate that the roadbed (ballast) isn't as robust as it should be.
All of this is why rail (particularly CWR) is ideally laid at a neutral temperature.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Cold makes things shrink and rail will be in tension in cold weather. If there are imperfections, it can break. But it is strong and can take a lot of tension. If it breaks, signals will detect. Unlike heat kinks where the signals don't. Dark territory used to be jointed rail where there was some play to allow rail to open a joint a small amount.
Does rail kink, misalign or break in cold weather and if so how long a sustained cold period for it to occur
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