After close examanation of a photo on UP’s tripple track mainline I noticed that the concreat ties don’t have spikes to hold the plates witch in turn hold the rail in place. how does this work? it almost looked like some sort of clipping device. Any answers?[%-)]
Yes. Spring clips.
Said spring clips hold the rail to plates which are, in turn, bolted to the ties.
If you’re declipping by hand and catch a Pandrol pig tail clip in the shin it hurts like a motha…[banghead] Those things definitely leave a mark.
The towers that hold the clips are cemented right into the tie. They are inserted into the tie when the concrete is poured in the plant. The rail sits on top of a plastic pad (Which are wearing out way too fast) and then the clips are applied to hold the rail in place on top of the pad. The good thing for guys like me is that the short lifespan of the pads has created the reason for pad gangs whose sole purpose is too replace the worn out pads. Concrete ties supporting coal trains means more jobs for us because the pads can’t stand up to the pounding they take.
Pandrol makes these spring clips and their website has excellent and clear photos. There are several types.
http://www.pandrolusa.com/jointbar.shtml
Dave Nelson
Might as well add the D-E Clip to that list. Almost as common as pandrols anymore.
http://www.pindad.com/prodgul800.php?varkdnews=TCPKDE&bahasa=2
From our Austrailian friends/buds who invented them.
My question about concrete ties is this: how are the ties secured into the ballast?
My limited understanding of track structures has me believing that wood ties are held in place by the penetration of the spiky points of the ballast rocks underneath; if this is true, then how does the ballast ‘grab’ the concrete tie?
Wood ties - a little penetration, but no so much - only 1/4 to 1/2 inch typically, and then only some of the ballast rocks will do that - most will lie flat.
Instead - and for concrete ties, too - on the tie bottom it’s the weight of the tie + rails above, plus the coefficient of friction there against horizontal motion, plus maybe any “interlock” as you mentioned. As against sinking or settlement, it’s the spread-out of the load over the greater area of the bottom of the tie.
On the sides and ends, it’s the pressure of the ballast stone, from the dead weight of it, plus the effects of compaction by the track tampers and shoulder ballast compactors, again times the coefficient of friction there. In this instance, note that the resistance to horizontal motion is not just the "passive pressure’, which is roughly the weight and pressure that the ballast stone imposes against the sides of the ties - not a huge amount for only 7 to 12 inches deep, as you might imagine. Instead, it’s the “active pressure”, which is the amount of force that it would take to shove the tie back through and along the ballast stone. Again, as you might imagine, that’s a lot harder to do, and it is - a typical rough or crude approximation is about 3 times as much as the “passive pressure” described above.
Hope this is responsive. For more info, you’d need a soils mechanics or engineering course, or at least a detailed seminar on this kind of thing.
- Paul North.
That’s obviously a question for Dirty Feathers, but…
I’ve always been under the impression that it was the interaction of the ballast with itself. If we relied on the ballast gripping the ties, then steel ties would never work.
That’s not to say that some of that doesn’t occur.
Who ever said steel ties did work? For static or low-speed loads on tangent industrial track – and where maintaining surface and line does not matter – they do OK. For heavy loads, curves, high speeds, and places where surface and line matter, they do not. (Note – I’m not talking about the use of steel ties out-of-face for gauge control, only steel ties as in-face installations, which is what matters.)
RWM
The term in the industry is “resilient fastener” – as opposed to “cut spike” used for wood ties.
As our muddy friends pigfarmer and mudchicken described, there are steel fastening points sometimes called “shoulders” cast-in to the concrete tie on both sides of both rails. These automatically gauge the rail (the rail base fits in-between the shoulders) and provide a point for the resilient fastener to attach to the tie. The fastener presses downward onto the top of the rail base, pressing it against the tie. A plastic pad goes inbetween the tie and the rail to protect the tie from erosion during load/unload cycles, and additionally helps us woebegone train-control people with reducing current leakage between the rails. Simple e-clip fasteners (the original Pandrol clip) were originally used; they’re applied by driving one leg of the clip into a horizontal hole in the shoulder either by machine or by sledgehammer. The other leg of the e-clip presses downward on the rail using spring tension in the e-clip to make this work. In other words, the e-clip is manufactured from a special, heat-treated steel that resists being deflected, and the installation of the e-clip is deflecting it. They’re called e-clips because they are made out of a steel rod about 3/4’ in diameter and about 8" long that is bent into what looks sort of like the shape of a lower-case letter e.
E-clips are still used for new industrial track, but for high-tonnage applications the industry has largely transit
Some of the newest concrete tie designs have scalloped sides to help resist sideways movement. This helps lock the tie into the ballast section, assuming the ballast is of the right type to act as if it was a solid material, which requires high angularity, high hardness, large size, and very little fouling by fines. Fines act like a lubricant to help the ballast stones slide across each other.
RWM
At some point, the ballast has to interact with the ties, regardless of the tie material, and that point/ plane was the focus of my comment. Elsewhere in the structure, you’re right - it’s pretty much the interlocking & interaction of the ballast.
Also, this discussion really depends on the direction of the motion or force that’s being resisted. The initial question about the concrete ties was, “How the are the ties secured into the ballast?” and, “My limited understanding of track structures has me believing that wood ties are held in place by the penetration of the spiky points of the ballast rocks underneath; if this is true, then how does the ballast ‘grab’ the concrete tie?”
That question could relate to either (1) the vertical pressure of the tie into the ballast (hence the “penetration”); (2) the horizontal or lateral sliding of the tie to the side, as in a shift in alignment; or (3) a horizontal or longitudinal sliding of the tie, as in the track “running” downgrade or with the traffic, or being pushed by CWR (Continuous Welded Rail) heating or cooling forces, etc.
Considering each in order:
(1) The resistance to vertical pressure is pretty obvious.
(2) The resistance to lateral / alignment displacement is generally a combination of the friction on the bottom of the tie (a lot), the friction and resistance from the ballast along the sides of the ties (moderate), and the resistance from the ballast at the end of the tie (somewhat lower, although these days tha
…and now you begin to see why railroaders get frustrated with dumb highway people and gyppo contractors trying to put round river run gravel in the track structure. (it’s not hard enough either)
Man, you must have really had - or are still having ? - bad experience(s) with that. But I know what you mean.
Likely, the main thing they know or understand is that it’s a lot less $$$. They never had to maintain it afterwards.
- Paul North.
In the last two years:
Colorado (twice - there is a piece of track in Grand Junction served by UP that handles gasoline tank cars just south of I-70 that has to be seen to be believed)
Illinois (once)
Missouri (once)
Iowa (once)
Kansas (once)
Might as well have built the tracks on ball bearings![banghead][banghead][banghead]
Yep - 'nuff said. You have had a slew of bad experiences. Too bad.
“Upon this point, a page of history is worth a volume of [il]logic.” - U.S. Supreme Court Justice Oliver Wendell Holmes, Jr.
- Paul North.
Round rock is no fun when you’re throwing plates either, especially when you’re working on a fill. Toss a plate and it slides right down the ballast and all the way down the embankment. Then you have to walk/slide down the rock and drag the stinking plate back up the hill. Repeat that process over and over and it gets a little tiring.