# Do You Really Know How a Train Stays On The Tracks?



## xrunner (Jul 29, 2011)

I thought I knew, until I saw this video. What I thought I knew - was wrong.


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## tjcruiser (Jan 10, 2010)

Two thumbs up!


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## NIMT (Jan 6, 2011)

Excellent post xrunner!


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## Xnats (Dec 5, 2010)

That was pretty cool.


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## tjcruiser (Jan 10, 2010)

How come none of my college professors ever taught while sitting in a wingback chair like that?!? Cushy job!


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## gunrunnerjohn (Nov 10, 2010)

Interesting, the scary part is that it really makes sense.


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## cbarm (Apr 15, 2011)

C'mon guys....think about this a lil. It kinda makes sense what he is saying about the tapered wheel surface to the railhead, but wouldnt that only work for one radius of track??? If we were to go by what he is saying then that means that they should all derail when being yarded through a HO scale equivalent #4 switch, as opposed to a broad sweeping curve out in the desert.....explain that one....


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## Massey (Apr 16, 2011)

Simple, at least I think it is. There is going to be some slippage the taper can only take out so much of the differential of hte curve before the wheel has to slip a little. Rails wear, wheels wear and if they didnt slip there would be no wear. Also I have heard that curves have a slightly wider gauge when they are sharper to assist the tapers in getting to the right location to maximise the different radii of the wheel.

Massey


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## NIMT (Jan 6, 2011)

Yea what Massey said!:thumbsup:
cbarm, why do you think they have to go so slow threw a Up scale #4 turnout and that is also what the numerous guard rails are for!
Take a HO turnout and remove all the guard rails on all the areas, points, and frogs and watch how quickly and how often your train will derail!
Can you say super incline, that is another way to assist in the steering of the cars trucks.
Did you also know that large modern diesels have steerable trucks under them to assist in switch transitions, and curves!


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## T-Man (May 16, 2008)

cbarm said:


> C'mon guys....think about this a lil. It kinda makes sense what he is saying about the tapered wheel surface to the railhead, but wouldnt that only work for one radius of track??? If we were to go by what he is saying then that means that they should all derail when being yarded through a HO scale equivalent #4 switch, as opposed to a broad sweeping curve out in the desert.....explain that one....


Two things he left out. With a taper the radius changes so the difference between hi an low depends on the force exerted during the curve.
Also only a few wheels are doing this during a curve not the whole train. Overall there is a harmonic motion of side to side while the train takes the curve.
Does that help?

The designing engineers get a thumbs up for that one.:thumbsup:


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## gunrunnerjohn (Nov 10, 2010)

And just think, they figured this out over 100 years ago.


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## T-Man (May 16, 2008)

Isn't there a magnetic suspended train in Japan. Let your forces do the adjusting. ( Let you fingers do the walking).


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## gunrunnerjohn (Nov 10, 2010)

I think that magnetic train in Japan has had some issues, so maybe that's not a good example.


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## cbarm (Apr 15, 2011)

Well OK, I see what you guys are getting at but what would cause "truck walk" in a broad curve if these wheels are tracking the rails like the vid proclaims? I ride trains everyday and we get it all the time even after the Sperry car has just been over it and no slows have been added to a TGBO. I do realize that a sharper turnout must be used at a slower speed, but I dont believe that the guard rails do much for a slow speed switch. We have several sharp turnouts in our yard and they do not have guard rails, but our yard track speed is 10 mph.


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## gunrunnerjohn (Nov 10, 2010)

Nothing is perfect, and the wheels and the track have variances.


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## Reckers (Oct 11, 2009)

That guy is Richard "Dick" Feynman---he was absolutely brilliant. He worked on the Manhattan Project and was a very common-sense type of engineer. He was on the committee that investigated the space shuttle blowing up coming off the pad. When the shuttle manufacturers insisted the o-rings would maintain their flexibility in the sub-zero temperatures associated with the liquified-gas fuel, he asked them to bring a smaller o-ring to the hearings, made of the same material. They did and as the hearing progressed, he dropped the sample into his iced water. After a few minutes, he fished it out, held it up and attempted to stretch it: it snapped. A simple test that sat all the BS aside.


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## T-Man (May 16, 2008)

cbarm said:


> Well OK, I see what you guys are getting at but what would cause "truck walk" in a broad curve if these wheels are tracking the rails like the vid proclaims? I ride trains everyday and we get it all the time even after the Sperry car has just been over it and no slows have been added to a TGBO. I do realize that a sharper turnout must be used at a slower speed, but I dont believe that the guard rails do much for a slow speed switch. We have several sharp turnouts in our yard and they do not have guard rails, but our yard track speed is 10 mph.


I can't define truck walk. 
You left me at the station on this one.


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## Reckers (Oct 11, 2009)

...and without a ticket. *L*


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## tankist (Jun 11, 2009)

well, yes. i really knew that 
when i first asked grandpa demonstrated by rolling a tappered glass on the table (memories...)



cbarm said:


> C'mon guys....think about this a lil. It kinda makes sense what he is saying about the tapered wheel surface to the railhead, but wouldnt that only work for one radius of track???


nope. just like continuously variable transmission in car has infinite ratios. for harder turn the outer wheel climbs more presenting even larger radius to rail. at the same time the inner wheel that slipped a bit in presented less radius. for even harder turn the wheel clims even more ... all the way till it meets the flange












Massey said:


> Simple, at least I think it is. There is going to be some slippage the taper can only take out so much of the differential of the curve before the wheel has to slip a little.


 the wheel can take all the difference - trains don't turn on a dime. in ideal engineering world , when all the calculated curvature and super-elevation is built to the T, where all the wheel-pairs are cut to correct geometry and not worn slipage not going to occur and flange not going to touch. but in reality we have wear and imperfections so stuff does slip despite being designed not to : )


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## sstlaure (Oct 12, 2010)

Reckers said:


> That guy is Richard "Dick" Feynman---he was absolutely brilliant. He worked on the Manhattan Project and was a very common-sense type of engineer. He was on the committee that investigated the space shuttle blowing up coming off the pad. When the shuttle manufacturers insisted the o-rings would maintain their flexibility in the sub-zero temperatures associated with the liquified-gas fuel, he asked them to bring a smaller o-ring to the hearings, made of the same material. They did and as the hearing progressed, he dropped the sample into his iced water. After a few minutes, he fished it out, held it up and attempted to stretch it: it snapped. A simple test that sat all the BS aside.


Actually.....all of the engineers at Morton Thiokol predicted the o-ring failure in their design documentation if the temperature for launch was below a certain threshold. The engineers advised not to launch due to the outside temperature, but the team was pressured to make the launch happen. I've personally seen the DFMEA (Design Failure Mode Effects Analysis) documentation on the rocket boosters where this catastrophic failure was accurately predicted. The engineers warnings were ignored and the launch proceeded.


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## Massey (Apr 16, 2011)

Engineer warnings were ignored once again when Columbia re-entered the atmosphere a few years ago. The engineers warned that the foam strike could have caused catistrophic damage to the heat shield and well it did. There was equipment on board to check the wing but the management thought it was going to be "too dangerous" to attempt. How much more dangerous could it have been compaired to a basketball sized hole in the leading edge of the wing in a place that takes the most stress from heat.

Why is it that the smartest people in the room are the last ones management listens to?

14 Astronauts have lost thier lives for this very reason, and who knows how many other professions as well.

Massey


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## tjcruiser (Jan 10, 2010)

Massey, etc.

I'll continue with this sidebar just a bit ... here's a fascinating real-life near-disaster story ...

The Citicorp building in NYC was designed by with world's brightest engineers, and was the showpiece headquarters one of the world's largest banks. Some time after the building's grand debut, an inquisitive question from a young college student brought the engineers to the shocking conclusion that the building was structually flawed ... big time. In a mad scramble, the skelton of the building had to be significantly reinforced as a 100-year storm bore down on NYC with potential catastrophic effects.

Have a read ... I'm an engineer, and this real-life narrative has always reminded me that we engineers had better do our homework thoroughly ...

http://www.duke.edu/~hpgavin/ce131/citicorp1.htm

TJ


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## Reckers (Oct 11, 2009)

Massey said:


> Engineer warnings were ignored once again when Columbia re-entered the atmosphere a few years ago. The engineers warned that the foam strike could have caused catistrophic damage to the heat shield and well it did. There was equipment on board to check the wing but the management thought it was going to be "too dangerous" to attempt. How much more dangerous could it have been compaired to a basketball sized hole in the leading edge of the wing in a place that takes the most stress from heat.
> 
> *Why is it that the smartest people in the room are the last ones management listens to?*
> 14 Astronauts have lost thier lives for this very reason, and who knows how many other professions as well.
> ...


I might be able to answer that question, Massey, from experience.

I work for a trucking company that's owned by GE. The role of president of the company is filled by someone hand-picked by GE for the job. Essentially, they take a fast-track management person and give him the job. He usually arrives knowing nothing about transportation, but his own set of skills and experience. The concept is that we teach him about transportation and he brings his past experience to the table and contributes what he can. Since he's running the place, it's a balancing act: he makes changes he thinks are necessary or beneficial, and we "advise" him when we think he's about to step in it. He stays for 2-3 years, and then we get another one. You can argue the benefits of it, but it does give GE a number of people who are highly qualified in transportation as they climb the ladder.

Now---the answer I have to offer. Take a really bright kid. Let him grow up knowing he's always smarter, in school, than everyone else in the class. He gets used to the idea that he always comes to the right answer faster than anyone else: a subconcious self-perception of omniscience. Now, let a large company court and hire him as he graduates with an engineering degree, MBA, you name it. Move him up the ladder faster than his peers because he's identified as a fast-tracker. The self-perception solidifies and he has a hard time even considering the opinions of others---he's been right all of his life. Add a big ego, put him in charge and you have a recipe for disaster. My last boss was like that, and only some very tactful "advice" verging on argument kept his thing out of the wringer. Sometimes, people eventually get tired of it and say, "The hell with it: he's so perfect, let's let him find the landmines on his own."


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## gunrunnerjohn (Nov 10, 2010)

I've twice been in the unenviable position of going into a company as a consultant and blasting guys like Reckers describes out the door. Of course, it involved proving beyond a shadow of a doubt that they were full of the brown stuff and what they were doing made no sense. Naturally, the other people that liked these guys weren't happy to see me come, and even happier to see me go! 

The worst one was a guy that had spent several million dollars on a flawed premise for a semiconductor fabrication machine. When I announced the king had no clothes, there was dead silence in the room! He had designed around a flawed idea of how the basic servo loop would function, and he refused to see the error in his ways. We actually had to build a prototype to prove that it didn't work!


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## eljefe (Jun 11, 2011)

Reckers said:


> He was on the committee that investigated the space shuttle blowing up coming off the pad. When the shuttle manufacturers insisted the o-rings would maintain their flexibility in the sub-zero temperatures associated with the liquified-gas fuel, he asked them to bring a smaller o-ring to the hearings, made of the same material. They did and as the hearing progressed, he dropped the sample into his iced water.  After a few minutes, he fished it out, held it up and attempted to stretch it: it snapped. A simple test that sat all the BS aside.


Actually, his example was flawed. If what he demonstrated was correct, the Shuttle would have been destroyed at the moment of SRB ignition and blown up on the launch pad. In actuality, the o-rings warm up because they're right next to rocket fuel burning at thousands of degrees. This is why they quickly sealed and the rocket boosters worked for a full minute of flight. What really doomed the Shuttle was wind shear, the strongest ever experienced on a Shuttle flight. This shear flexed the vehicle enough that the o-ring seal was broken and a flame shot out from the booster hitting directly on the external fuel tank. If that flame had been pointed any other direction, the Shuttle would have survived.

It was a combination of factors that caused the disaster, and Feynman's simple explanation caused a lot of them to be overlooked. Columbia was also destroyed because of wind shear, the second worst ever experienced on a Shuttle flight, but the significance of winds during launch went under-appreciated when people bought Fenyman's oversimplified explanation.


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## Massey (Apr 16, 2011)

This is long but a subject I taken a lot of time to study in both cases.


Wind shear did not destroy Columbia. The Columbia vehicle was hit by foam shedding from the tank. This has been recorded on every flight before and after and it was also not the first time that tiles were damaged. This time however the damage was caused by the strike of a piece of foam on one of the most delicate areas of the vehicle's body, the leading edge of the wing. The Carbon Carbon panels are extremely strong compaired to their weight but they are also brittle. This is noted in design documents.

Columbia was a unique shuttle. No other shuttle had the same computer systems on board. Columbia was the fist shuttle as therefore was equiped with sensors throughout the body that monitored things like torsional stress impact, and temp. These sensors were not installed in the other shuttles since the tests for Columbia proved that minimal heating and stresses were ever recorded. Also the majority of the temp sensors were located in the same wing that was hit but the impact sensors were located in the other wing, so the foam strike was not recorded by the ship's sensors. Not that it would have done much good the data from that computer was not available to the ground or crew, it was only available after the data was pulled off the computer after the vehicle is processed. 
Data from the wing sensors was able to track the thermal breach through the leading edge (at the same place the launch video showed the foam strike) and as it went through the wing. Ground and crew were able to see the failure of the wing tire pressure but had no time to come to a conclusion about what was happening, nor could they do anything about it at that time. The fatal blow to the shuttle was when a fuel tank located in the wing ruptured tearing the wing off the shuttle and there fore causing the craft to burn up as it passed through the most stressful phase of re-entry.

This information is from the CAIB documents that NASA posted online after the investigation was complete. This document is very dry and hard to read for those who do not understand Avionics data. I have read the document cover to cover, in part due to curiosity and in part because in the Navy I repaired Avionics equipment. 

The wind shear for Challenger was not a mitigating factor but yes it did cause the vehicle to break up, in a way. The O-ring was bad, it was documented on the recovery paperwork but since O-rings have still sealed being cracked worse it was decided to use it again. The others that were worse were used in warmer temps than this one was. At launch the motion of the SRB at the joint that failed was 10% greater than had ever been recorded, and this allowed some gasses to bypass the o-ring. This small breach appeared to reseal itself after the motion of the booster joing subsided. As the fuel burned it was able to burn through the o-ring at the same place that the initial breach occured durring the launch. This allowed high pressure ionized gasses to burn through the o-ring, the booster casing and eventually burn through the strut holding the booster to the tank. When the strut failed the booster rolled over creating a massive yaw contition that destroyed the shuttle. The tank failed a few hundredths of a second later. There was no "explosion" per se, the O2 and liquid Hydrogen decompressed before burning and did not generate enough pressure to cause a destructive burn. The shuttle pitching 20° at Mach 6 was the cause of the destruction. 

So yes it was wind shear if you consider the shuttle being forced sideways at mach 6. 

Massey


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## eljefe (Jun 11, 2011)

I think I was a little unclear in my post. The wind shear I refer to for Columbia was encountered during launch and caused the bipod foam to separate in the first place. This was the initial cause of the vehicle's ultimate demise.

As for Challenger, winds were a major factor in the disaster (both before and after launch) that has never been fully appreciated. Read more here:

http://www.aerospaceweb.org/question/investigations/q0122.shtml


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## Massey (Apr 16, 2011)

That was an interesting link about the space programs for both the US and USSR. 

In all the reports I have read that is the first one that ties the wind shear into the blowby of the booster. It says in the article that if the blowby was going any other direction other than against the tank and strut that the shuttle would have made orbit... I dont know how it could have being that the shuttle's computers were already reading a loss of pressure in the right SRB and the SME's were changing their gimbal location to counter the loss of thrust from the leak in the SRB. Just as the tank started to breach the shuttle started the emergency shutdown of one of the SMEs and would have initiated shut down of the other 2 and also emergency abort. Unfortunatly the tank's failure happened before the ship's computer could comprehend the full extent of the failure. 

I remember the CAIB report did have the meterological information in there but the conclusion was that a combination of factors were the cause of the foam shedding, not just the wind shear, but the wind shear was mentioned both before and after the foam strike. The report stated issues such as vibrations, improper handling of the tank, foam density and a few other factors also played the part of the loss. This area of the tank has lost foam many times before and even lost foam on the next flight of the shuttle, striking the underbelly and that send the astronauts out to test the new tile repair stuffs they carried on board.

Truth be told, space flight is dangerous any way you look at it. If given the chance to ride a rocket or shuttle into space I would do so in a minute with out hesitation.

Massey


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