Why difference in ride? (Track quality)

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Robert Gift

former OL presenter
In the late 1950s my father took me on a business trip from Pittsburgh to St. Louis.

The difference in ride from one railroad's track to another was quite noticeable.
Was it a difference in track laying, or justhathe track we.re later riding on was heavily used by freightrains and beaten to death?

Thank you.
 

Ballard Beaver

ballard beaver
not sure how to answer the above question, but related to this i have my own question. i have been watching freights for a while now and occasionally while watching from above (on overpass or pedestrian bridge) i see cars shaking violently from side-to-side (laterally). im not talking about rocking or swaying, im talking about lateral shifting-shaking. usually i see it when the train is going fast. obviously the wheel flanges are sufficient to keep the car from derailing but i cant imagine this is an "efficient" movement. why does this happen? does it only happen on empty cars? or only happen on cars that are far back on the train away from the lead units? not sure anyone will know what i am talking about, i dont think you would notice it watching from the ground.i wonder if it is due to the tracks, or the car, or both.
 

Robert Gift

former OL presenter
Does thatrack have depressions or pounded areas which aggravate harmonic movement at certain speeds?
Would be nice to video this and show the railroad and us.
I would either increase or decrease the train'speed to get it out of that harmonic resonation.
 
Does thatrack have depressions or pounded areas which aggravate harmonic movement at certain speeds?
Would be nice to video this and show the railroad and us.
I would either increase or decrease the train'speed to get it out of that harmonic resonation.
Increasing the train's speed would make it worse and could possibly cause a derailment. Harmonic rock occurs in jointed track because, by their nature, joints cause a low spot. Joints are also staggered, so that staggered series of low joints causes the train to rock. The by the book solution is to lower the track speed to class 1 (supposedly harmonic rock doesn't occur at low speeds) or to raise the joints.

A thing called 'warp' also exists that can cause a train to rock, although it's not exactly the same thing. Again, it's a track geometry problem, and can be resolved by surfacing.
 

Robert Gift

former OL presenter
Increasing the train's speed would make it worse and could possibly cause a derailment. Harmonic rock occurs in jointed track because, by their nature, joints cause a low spot. Joints are also staggered, so that staggered series of low joints causes the train to rock. The by the book solution is to lower the track speed to class 1 (supposedly harmonic rock doesn't occur at low speeds) or to raise the joints.

A thing called 'warp' also exists that can cause a train to rock, although it's not exactly the same thing. Again, it's a track geometry problem, and can be resolved by surfacing.
If you move above or below that speed which causing such rocking, it can be lessened. You are no longer at that ideal harmonic frequency where movement coincides with the pressures which bear down on the same parts of the rail as previous trains traveling at the same speeds.
It can even occur at slow speeds matching the rocking movement.
 
If you move above or below that speed which causing such rocking, it can be lessened. You are no longer at that ideal harmonic frequency where movement coincides with the pressures which bear down on the same parts of the rail as previous trains traveling at the same speeds.
It can even occur at slow speeds matching the rocking movement.
What I was taught in FRA Track Safety Standards class directly contradicts that, but okay.
 

Robert Gift

former OL presenter
Slower is safer than faster.

What I was taught in FRA Track Safety Standards class directly contradicts that, but okay.
Of course, go by what they say.
They know better.

What is "warping"? Whole track has higher and lower areas not caused by joints - such as in welded rail?
Thank you.
 

litz

Trainman
Typically and traditionally, around 15mph is one of those magic points where rocking can get really bad on jointed rail.

The one time we ever took the BRSR equipment faster (on a combined trip w/the TVRM around the "Eye" of the Hook and Eye) it smoothed right out when we got above 15mph.

On our track, at 15, it can be pretty pronounced, and we have to do trackwork every year (or two) to keep it as minimal as possible.
 

UP Scott

Active Member
Not being an expert on anything, (ex is a former has been and a spert is a drip under pressure :rolleyes:) by definition, a harmonic is a multiple of a primary frequency. (maybe not Webster’s version, but close :) ) I'm guessing that the length of a car or distance between the trucks and the rail joints at 15 MPH or so, is the sweet spot for rocking and creates a rocking of some frequency "X". So in theory, at 2X the speed, say 30 MPH, that rocking may occur again, but at about half the rate and so on. What may really keep it from getting bad at higher speeds, is the ability of the car to rock that fast since the mass of the car helps attenuate or dampen the motion. Just my thoughts and they can and have been wrong before, so use at your own risk… :cool:
 
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Ed Sand

General Idiot
What you originally describe is just bad track on one road and better track on another.

Lateral shaking like the Beaver describes sounds to me more like a truck or equipment problem rather than a track issue. This is different than harmonic rocking.

Harmonic rocking of certain equipment types, such as bulkhead or center beam flats, does have a peak speed at which the harmonics can cause derailments. My memory is deeply unreliable, but I seem to remember 22 or 23mph being the highest risk factor speed.
 

Beverlyhelper

beverlyhelper
Everybody do the harmonic rock!

What you originally describe is just bad track on one road and better track on another.

Lateral shaking like the Beaver describes sounds to me more like a truck or equipment problem rather than a track issue. This is different than harmonic rocking.

Harmonic rocking of certain equipment types, such as bulkhead or center beam flats, does have a peak speed at which the harmonics can cause derailments. My memory is deeply unreliable, but I seem to remember 22 or 23mph being the highest risk factor speed.
Back in the 80's on the UP, 18mph-23mph was the range we had to stay out of with bulkhead or center beam empty cars to avoid harmonic rocking. I remember climbing up the Deschutes Canyon on the UP local with a bunch of empty bulkheads and keeping a sharp eye on them. We usually had two GP40's. If our train was heavy, 15mph was our limit all the way to the top. If we had a light load, we'd zip up at 25-30mph.
 

trainstuffguy

Canadian Member
rapid shaking

not sure if the if this is the same as what the OP is talking about but I have seen this violent shaking. In my case its usually just one car shaking in a long train traveling rather fast say 40-50MPH on good CWR track. the shaking is rapid perhaps a freqency of one side to the other and back per second (1hz ish). its not really a rocking motion as its sometimes more violent lower on the car than at the top I have seen this many times here on the CN Kingston Sub at the Cobourg station in Ontario. This busy track is shared freight and passenger with 60 and 100MPH limits respective in that area. Kind of scary if you ask me. its got to be hard on the knuckles and rail.
 

LoganTrackdog

New Member
What you guys are talking about is called "hunting". When flanges and wheels get worn out, the wheels have some slop in them. The trucks will "hunt" from side to side on the track. If you ever pace trains on a highway at 55-60 mph, you can actually see the trucks shifting from side to side, and shaking the daylights out of the car. We have seen it many, many times on the UP main between Woodbine and Dow City, Iowa. Makes you wonder how they stay on at all. One thing to note. We seem to see it more on concrete ties that wood ties. IDK, maybe that has nothing to do with it.

In this youtube vid, you can see a car doing this action.
http://www.youtube.com/watch?v=n-EfKFxGJc4

Google railroad wheel hunting for all the details.
 

Ballard Beaver

ballard beaver
What you guys are talking about is called "hunting".

In this youtube vid, you can see a car doing this action.
yes this is exactly what i was talking about in my post above. thanks for explaining! now, is this something that will get corrected soon? does it have any consequences?
 




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