Flat wheels

[junior yardmaster]

I watch the Rochelle, IL videocamera site almost every day, and am constantly amazed at all the "flat wheels" on many of the cars as they pass by the camera, which as you know also supplies sound.  It seems to me that rolling efficency could be vastly improved by maintenance of the cars.  Or, would it be more expensive to fix the flat wheels?   Junior Yardmaster

[oltmannd]

I'm not so sure there's any measurable energy penalty for flat wheels.  The big problem is the impact the rail.

There are a couple of ways to find problematic defects.  One is the traditional way where car inspectors visually look for and measure flat spots.  Not all flat spots are condemnable.  

The other is WILD detectors which measure the impact of the flat spots (and equally dangerous, but silent, out of round conditions) by using strain gauge equipped sections of track.

In either case, the problem has to reach a threshold before a RR can change a wheelset and bill the car owner.  Negotiating changes to the thresholds are often time conuming and difficult because of the cost impact to the car owners.  The AAR is the place where the agreed upon standards are maintained and enforced.

[oltmannd]

The other consideration for flat and out of round wheels would be prevention.  It's likely that an ancillary benefit of ECP might be wheel slip/slide prevention.  

[Norm48327]

Are you sure it is flat wheels you are hearing or is it the sound of wheels pounding the diamond?

[Deggesty]

Norm48327

Are you sure it is flat wheels you are hearing or is it the sound of wheels pounding the diamond?

 

What I have heard, many times, is the rhymthic clump of the wheels dropping into the gap in the frogs and, as Norm says, "pounding the diamond." This continues for the full length of the train. If the sound were from a flat wheel, it would be heard only occasionally instead of continuously as a train moves across the diamond. 

[CShaveRR]

Flat wheels and frog-pounding make different sounds, and are not likely to be confused with each other.  If the o.p. says he heard flat wheels, he's probably correct.

As Don says, there has to be a threshhold before they're condemnable and billable.  Also, consider that some of these cars with flat spots may not have had them when the train left the point of last inspection.

I have long suspected (and by "long" I mean decades) that one seems to hear a lot more flat wheels these days than in the good old days because their sound used to be drowned out by the omnipresent clickety-clack over the scores of joints within hearing range.

[junior yardmaster]

CShaveRR

Flat wheels and frog-pounding make different sounds, and are not likely to be confused with each other.  If the o.p. says he heard flat wheels, he's probably correct.

As Don says, there has to be a threshhold before they're condemnable and billable.  Also, consider that some of these cars with flat spots may not have had them when the train left the point of last inspection.

I have long suspected (and by "long" I mean decades) that one seems to hear a lot more flat wheels these days than in the good old days because their sound used to be drowned out by the omnipresent clickety-clack over the scores of joints within hearing range.

 

[tree68]

A "rule of thumb" I've heard regarding flat spots is this - if you can hear one from more than seven cars away, it's a problem.  Less than that and it's OK, more or less.  Obviously, any defect is an issue, it's when it becomes a problem...

There are specific guidelines for dealing with flat spots, depending on size.  From NORAC:  Less than 2.5" - normal speed (save other defects).  Up to 4" - 10 MPH.  Over 4" - Stop and stay until it's determined the car can make it to the next place it can be set out.

If my math is correct, a 2.5" flat spot is about 2% of the total tread of a 36" wheel.  Noisy, but not much of a problem.

 

[Paul_D_North_Jr]

Back in the late 1970's or so CN did a study of the effect of flat wheels on the track structure, which was published in either Railway Track & Structures magazine or the Proceedings of the American Railway Engineering Association (AREA, predecessor to AREMA).  In particular, the purpose of the study was to measure and determine the costs of the track damage caused by flat wheels, whether or not the flat spot was bad enough to require replacement or 'truing' of the wheel.  The study included both wood and concrete ties, as I recall. 

The study concluded that the costs of the track damage greatly exceeded the costs of replacing/ truing the wheels.  The administrative / institutional problem was that the track damage came out of the Engineering / MOW Department's budget, whereas the costs of fixing the wheels came out of the Mechanical Department's budget.  Although a 'holistic' approach could be taken to minimize the overall aggregate or total costs by some combination of less wheel replacement costs and less track damage costs, evidently those 2 departments of most railroads couldn't agree on a method to make even that internal adjustment and reconciliation.

From: http://www.tsb.gc.ca/eng/rapports-reports/rail/2014/r14w0041/r14w0041.pdf

"Wheel impacts and broken rails

Rail steel is known to have reduced fracture toughness and ductility at low temperatures, particularly if a rail defect, which can act as a stress riser, is present. It is also generally recognized that wheels producing high-impact loads may cause damage to equipment (axles and journals) and track infrastructure. Canadian National Railway (CN) had previously analyzed wheel-impact and broken-wheel data from 1992 to 1995. The analysis established a causal link between high wheel impact loads and broken rails.

The TSB has investigated at least 5 occurrences caused by broken rails resulting from high wheel impacts (Appendix A)."

See also: https://www.ihha.net/sites/default/files/document_0.pdf (pgs. 91 - 100)

http://railtec.illinois.edu/CEE/Crossties/Deliverables/2013_JRC_Van%20Dyk_et_al.pdf - QUANTIFYING SHARED CORRIDOR WHEEL LOADING VARIATION USING WHEEL IMPACT LOAD DETECTORS

- Paul North.         

[oltmannd]

CShaveRR

Flat wheels and frog-pounding make different sounds, and are not likely to be confused with each other.  If the o.p. says he heard flat wheels, he's probably correct.

As Don says, there has to be a threshhold before they're condemnable and billable.  Also, consider that some of these cars with flat spots may not have had them when the train left the point of last inspection.

I have long suspected (and by "long" I mean decades) that one seems to hear a lot more flat wheels these days than in the good old days because their sound used to be drowned out by the omnipresent clickety-clack over the scores of joints within hearing range.

 

I think another factor is the empty braking ratio has increased as the car construction has gotten lighter and loads have gotten heavier.  Empty cars are more likely to slide when brakes are applied.

[oltmannd]

Paul_D_North_Jr

Back in the late 1970's or so CN did a study of the effect of flat wheels on the track structure, which was published in either Railway Track & Structures magazine or the Proceedings of the American Railway Engineering Association (AREA, predecessor to AREMA).  In particular, the purpose of the study was to measure and determine the costs of the track damage caused by flat wheels, whether or not the flat spot was bad enough to require replacement or 'truing' of the wheel.  The study included both wood and concrete ties, as I recall. 

The study concluded that the costs of the track damage greatly exceeded the costs of replacing/ truing the wheels.  The administrative / institutional problem was that the track damage came out of the Engineering / MOW Department's budget, whereas the costs of fixing the wheels came out of the Mechanical Department's budget.  Although a 'holistic' approach could be taken to minimize the overall aggregate or total costs by some combination of less wheel replacement costs and less track damage costs, evidently those 2 departments of most railroads couldn't agree on a method to make even that internal adjustment and reconciliation.

From: http://www.tsb.gc.ca/eng/rapports-reports/rail/2014/r14w0041/r14w0041.pdf

"Wheel impacts and broken rails

Rail steel is known to have reduced fracture toughness and ductility at low temperatures, particularly if a rail defect, which can act as a stress riser, is present. It is also generally recognized that wheels producing high-impact loads may cause damage to equipment (axles and journals) and track infrastructure. Canadian National Railway (CN) had previously analyzed wheel-impact and broken-wheel data from 1992 to 1995. The analysis established a causal link between high wheel impact loads and broken rails.

The TSB has investigated at least 5 occurrences caused by broken rails resulting from high wheel impacts (Appendix A)."

See also: https://www.ihha.net/sites/default/files/document_0.pdf (pgs. 91 - 100)

http://railtec.illinois.edu/CEE/Crossties/Deliverables/2013_JRC_Van%20Dyk_et_al.pdf - QUANTIFYING SHARED CORRIDOR WHEEL LOADING VARIATION USING WHEEL IMPACT LOAD DETECTORS

- Paul North.         

 

In the late 70s, Amtrak wanted to keep high impact wheels on Conrail freights off their new concrete ties.  Conrail installed their first WILD at Mill Creek PA to try to catch them and have them set out at Enola.  After sufficient work was done to show that it really was a good idea to fix high impact wheels, it took about a decade to get the AAR rule changed to allow billing.

[Paul_D_North_Jr]

From oltmannd above: "After sufficient work was done to show that it really was a good idea to fix high impact wheels, . . . ".  

  "On this point a page of history is worth a volume of logic." - Justice Oliver Wendell Holmes, Jr., of the U.S. Supreme Court (back in the 1920's or 30's). 

Procedural point: Compare and contrast the learned, scientific, and well-researched and analyzed discussion on this subject in the references I linked to above, with the speculation (nicest word I can use) in another thread here about "sloshing" in the oil tank cars causing rails to break.  (Note for those who don't know: A "kip" is shorthand for "KIloPound" = 1,000 lbs.; hence 100,000 lbs. = 100 kips.)  Some of the values and thresholds in those references - like individual wheel impacts above 140 kips (about 2x the normal static load) are enough to require stopping the train and setting out the offending car ASAP - are quite informative.  Compared to that, anyone with knowledge and/ or experience in the physics/ dynamics of railcars should recognize that the repetitive insistence on the sloshing theories is BoguS. 

- Paul North. 

[Anonymous]

I'm not suprised that there are so many flat-spotted wheels out there. Many crews sadly do not check for severe flatness in the first place.

A Strasburg RR employee once told me of a friend of his who woked for another railroad. He called to say that he had found a wedge of a freight car wheel! Much like a piece of pie. More to the suprise of both, a car came into the Strasburg yard a couple of days later, with a chunk missing, much like a pie. The two met up, and yes, it was a match!

Imagine how far that incomplete wheel went, banging along the rails unnoticed...

[Euclid]

Paul_D_North_Jr

  Compared to that, anyone with knowledge and/ or experience in the physics/ dynamics of railcars should recognize that the repetitive insistence on the sloshing theories is BoguS. 

It was the FRA that introduced the theory. 

There are two sides to the argument.  One side suggests the possibilty without proving it.  The other side insists that the theory is impossible and they don't prove that.  Which side is the least credible?

[zugmann]

S. Connor

Imagine how far that incomplete wheel went, banging along the rails unnoticed...

Probably between there and the last WILD?

[BaltACD]

[schlimm]

Paul_D_North_Jr

Compared to that, anyone with knowledge and/ or experience in the physics/ dynamics of railcars should recognize that the repetitive insistence on the sloshing theories is BoguS.  - Paul North. 

http://www.illinoisgreens.org/SpeedandSloshing.html  FRA and former head of NTSB are ignorant?

  http://ieeexplore.ieee.org/xpl/login.jsp?reload=true&tp=&arnumber=5367190&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5367190     Not so simple

http://web.itu.edu.tr/~mscelebi/documents/ocn_serdar.pdf  Liquids sloshing are far more complex than one would imagine.

 

[traisessive1]

Yeah guys, there is something wrong with your train. I think I heard a round wheel. 

You might think that's a joke, but, it really isn't. I'm sure there are more flat wheels out there than there are round ones. 

[tree68]

traisessive1

Yeah guys, there is something wrong with your train. I think I heard a round wheel. 

You might think that's a joke, but, it really isn't. I'm sure there are more flat wheels out there than there are round ones. 

 

I'm not sure that's actually the case, but it'd be hard to remember the last time I saw a freight train go by that didn't have at least one flat wheel...

[traisessive1]

Well around here it certainly is. 

[Wizlish]

schlimm

Paul_D_North_Jr

Compared to that, anyone with knowledge and/ or experience in the physics/ dynamics of railcars should recognize that the repetitive insistence on the sloshing theories is BoguS.  - Paul North. 

 

http://ieeexplore.ieee.org/xpl/login.jsp?reload=true&tp=&arnumber=5367190&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5367190    

Not so simple

Especially when you are dealing with almost completely-filled tank cars where the 'hydrodynamic drag' (by definition from moving fluid) would be limited to the volume of fluid that actually moves.  Did you actually read Mr. Zhang's paper, or look at the assumptions?

Since many of the posters here won't be able to read papers from IEEE, here are the references from the paper, for anyone who wants to check some of the physics involved:

1. M. Isaacson, C.S. Ryu. Earthquake-Induced Sloshing in Vertical Container of Arbitrary Section. Journal of Engineering Mechanics ASCE, 1998, 124(2): 158-166. (Pubitemid 28184622) 
2. M. Isaacson, C.S. Ryu. Directional Effects of Earthquake-induced Sloshing in Rectangular Tanks. Canadian Journal of Civil Engineering, 1998, 25(2): 376-382  
3. H.F. Bauer, W. Eidel. Non-Linear Hydroelastic Vibrations In Rectangular Containers. Journal of Sound and Vibrations, 1988, 125(1): 93-114. 
4. H.F. Bauer, W. Eidel. Liquid Oscillations in a Prolate Spherical Container.
5. P.G. Young. An analytical model to predict the response of fluidfilled shells to impact-a model for blunt head impacts. Journal of Sound and Vibration , 2003, 267: 1107-1126.
6. G.L. Kuiper, A.V. Metrikine, J.A. Battjes. A new time-domain drag description and its influence on the dynamic behaviour of a cantilever pipe conveying fluid. Journal of Fluids and Structures, 2007, 23: 429-444
7. Nipa A. Mody and Michael R. King. Platelet adhesive dynamics. Part I: Characterization of platelet hydrodynamic collisions and wall effects. Biophysical Journal Volume95 September 2008: 2539-2555
8. Hermann G. Matthies, Rainer Niekamp, Jan Steindorf. Algorithms for strong coupling procedures. Compute methods applied mechanics and engineering, 2006, 195: 2028-2049:

http://web.itu.edu.tr/~mscelebi/documents/ocn_serdar.pdf  Liquids sloshing are far more complex than one would imagine.

For only partially filled, rectangular-cross-section tank cars.   Which the people PDN was talking about, "anyone with knowledge and/ or experience in the physics/ dynamics of railcars", will recognize as being atypical of loaded North American HHFT consists, in very important physical ways.  Perhaps you will be so kind as to demonstrate, with proper mathematics, how to apply the methods in the two papers you cite to cylindrical tank cars filled to normal loading volume?

As an interesting added note, the two Turkish naval-architecture guys observe this, which I suspect Euclid may find interesting if he hasn't yet downloaded and read the paper:

Sloshing is not a gentle phenomenon even at very small amplitude excitations. The fluid motion can become very non-linear, surface slopes can approach infinity and the fluid may encounter the tank top in ... enclosed tanks.

The key question would appear to be whether there could be small resonant excitation in the carbody motion that would excite the comparatively small region in the tank where there can be harmonically-excited fluid motion into 'sufficient' complex motion to produce substantial impact/momentum force (or perhaps drag force?) on a meaningful percentage of the car structure.

[schlimm]

If you want to do so, go ahead.  I posted the study because sloshing is not so simple as to be dismissed with the sneaky, pejorative comment PDN made.   Perhaps in more cylindrical tanks no sloshing takes place.  I really do not know.   It's probably a moot point in regard to tank cars anyway.  

Due to the drop in oil prices, oil companies have cut back the exploration side greatly.  Several smaller exploration companies are gone.  Shell has earlier abandoned exploration in the Arctic and the tar sands.  Chevron's refining side is doing well but other components not so cutting 6-7,000 jobs, many in Houston.  Since the downturn worldwide, ~200,000 jobs lost. Most oil 'experts' (I realize that on this forum, outside expert opinions are often not accepted) see the price of oil remaining in the $40-50 range for several years, due to lower demand. Of course that is speculation, but informed speculation.   I wonder when we will start seeing reports of oil tank cars parked in storage?

[Euclid]

schlimm

If you want to do so, go ahead.  I posted the study because sloshing is not so simple as to be dismissed with the sneaky, pejorative comment PDN made.  

 

As I mentioned above, nobody is insisting that it is absolutely true the tank car load shifting is causing or has ever caused a derailment.  If anyone were insisting that is true, it would be incumbent upon them to prove it. 

What is being insisted on with an almost religious intolerance, however, is that derailments cannot be caused by this means.  For this assertion, it is reasonable for the agnostics to demand proof, and yet none is provided.

[schlimm]

Euclid

 

schlimm

If you want to do so, go ahead.  I posted the study because sloshing is not so simple as to be dismissed with the sneaky, pejorative comment PDN made.  

 

 

 

As I mentioned above, nobody is insisting that it is absolutely true the tank car load shifting is causing or has ever caused a derailment.  If anyone were insisting that is true, it would be incumbent upon them to prove it. 

What is being insisted on with an almost religious intolerance, however, is that derailments cannot be caused by this means.  For this assertion, it is reasonable for the agnostics to demand proof, and yet none is provided.

 

True.  And the rather lame attempt at a vulgarity disguised as a simple word of dismissive derision is sad.  "the repetitive insistence on the sloshing theories is BoguS "  [his caps, my bold] Why not just have the guts to say it? 

[wanswheel]

This post went to Hell, Michigan.

[Euclid]

Wanswheel,

Your above post is excellent information for the tank car sloshing discussion, but it has nothing to do with flat wheels, which is the topic of this thread.  I suggest moving this post to the thread titled:  “Oil Trains Cause Track Defects?”

[Paul_D_North_Jr]

schlimm

Euclid

 

schlimm

If you want to do so, go ahead.  I posted the study because sloshing is not so simple as to be dismissed with the sneaky, pejorative comment PDN made.  

As I mentioned above, nobody is insisting that it is absolutely true the tank car load shifting is causing or has ever caused a derailment.  If anyone were insisting that is true, it would be incumbent upon them to prove it. 

What is being insisted on with an almost religious intolerance, however, is that derailments cannot be caused by this means.  For this assertion, it is reasonable for the agnostics to demand proof, and yet none is provided.

True.  And the rather lame attempt at a vulgarity disguised as a simple word of dismissive derision is sad.  "the repetitive insistence on the sloshing theories is BoguS "  [his caps, my bold] Why not just have the guts to say it? 

Only because it's against the Forum's rules.  And a couple of pretty smart guys - both MIT engineering graduates - would also use that same euphemism on their NPR radio program. 

You point out that the fluid dynamics of "sloshing" is complex.  I agree.  The complexity is not only in the analysis, but in the subject of it.  The motion would be extremely turbulent to produce anything near the effects claimed or speculated, which would likewise greatly dissipate any such forces.  Any purported analysis of that complex motion will be mere circular reasoning, reflecting the input assumptions. 

- Paul North.      

[Paul_D_North_Jr]

traisessive1

Yeah guys, there is something wrong with your train. I think I heard a round wheel. 

You might think that's a joke, but, it really isn't. I'm sure there are more flat wheels out there than there are round ones. 

When I used to eat lunch next the local NS tracks, it was notable that multi-level/ auto-rack trains had very few flat wheels, in comparison to almost any other type (which all seemed to be roughly the same).  The only reason I can think of is that because they tended to run as "unit trains" - i.e., all empty or loaded between the same points on any particular trip - and are fairly lightly loaded even then - their braking characteristics are more uniform, so there's less variation that would cause one wheel to slide while the others didn't.

- Paul North. 

[Paul_D_North_Jr]

Euclid

[snipped - PDN] . . . What is being insisted on with an almost religious intolerance, however, is that derailments cannot be caused by this means.  For this assertion, it is reasonable for the agnostics to demand proof, and yet none is provided. 

Fine - here it is - yet again.  It's mainly based on the posts and reports above that from any one single flat wheel, the load had to reach the range of 140 kips (70 tons) from that single wheel - the equivalent of half of an entire car's weight or 4 wheel's worth (even a little more if it was less than a 286K car) - before that flat wheel would break a rail. 

For that magnitude of weight to be concentrated even on one truck = 4 wheels at the end of a car would require an impact-caused longitudinal deceleration (or acceleration) of about 2-1/2 times the force of gravity: 1/2 the weight of the car, times the truck centers of the car (say 50 ft.), divided by the height of the center of the tank cylinder (say, 10 ft.) [summation of the rotational moments = 0]. 

Further, to then reach that cited 140K force on any 1 wheel - to quadruple it from the above state - would require a further impact of 4 g's.  So a total deceleration of about 10 g's would be required.  That's not encountered anyplace on earth short of a NASA rocket or a high-differential-speed vehicle collision airplane crash, etc.) - not even earthquakes reach that amount of acceleration in any direction.  Railcar lading impacts - of solid objects - usually max out at 3 to 4 g's.  Impact loads on steel bridges are only 1.7 times the static loads, or 1.7 g's. 

Until someone can show me where railcar impacts can reach 2 to 3 times the max. typical - 10 g's in other than a derailment or collision already underway - or about 6 times the generally accepted static load - I'll remain a skeptic.

Further I sayeth not.

- Paul North. 

[schlimm]

Say all you want, blind us with your equations, the fact is that other sources more expert than you say something else.  Denial runs deep: what doesn't damage rails?  Some have said cold weather doesn't cause damage or heavy unit trains or sloshing of liquid contents or other unbalanced characteristics of tank cars or flat wheels (obviously it is an accumulation of being struck by not uncommon flat wheels, especially heavy trains).   But they must be right and the TSB, etc. are obviously wrong.  Meanwhile, rails get damaged to the point of failure leading to derailments.