Calling Coal Dragger

[26 Inf]

A guy I know asked me if I believed the earth was round or flat. Being clever I answered neither, it is a sphere.

His evidence was that rail track rails aren't arched - I hope he was just being a smartass.

Anyways, that got me to thinking, how do the railroads start a grade - is it just a minor deflection at each joint or something else?

What about continuous rail?

Thanks!

[SomeOtherGuy]

If you want to be pedantic and difficult, the Earth is actually an oblate spheroid.

https://gisgeography.com/ellipsoid-oblate-spheroid-earth/

Not that I would ever be difficult.

Not Coal Dragger but the acceptable slopes for railroad tracks are very minor, no more than a few %, and steel track is more flexible than you might think in the lengths they use. I suspect the joints are just standard 90/90 degree joints and the flexibility of the track accommodates the minor slope. Guess I'll find out if I'm right as others post.

[Coal Dragger]

A guy I know asked me if I believed the earth was round or flat. Being clever I answered neither, it is a sphere.

His evidence was that rail track rails aren't arched - I hope he was just being a smartass.

Anyways, that got me to thinking, how do the railroads start a grade - is it just a minor deflection at each joint or something else?

What about continuous rail?

Thanks!

The rail is actually quite flexible, the rail will deflect when locomotives and cars pass over, and that deflection takes place in the strongest most rigid cross section of the rail (vertical), the higher the speed or tonnage (or both) the more the rail will deflect under the wheels passing over. You can watch it in real time.

So with that understanding it should come as no surprise that the horizontal cross section is even more flexible, easily conforming to the curves typically in place on most any main line, siding, yard, or industrial tracks you can find. As for grades anything much over 1% is pretty much considered mountain grade, while not that steep by automobile standards it’s plenty steep when you’re operating at less than 1hp/ton. Again the elevation changes even in undulating terrain are never severe enough to not be easily accommodated by the flexibility of the rail.

Also keep in mind ribbon rail (continuous rail) comes off in 1/4 mile long sections, they are usually laid out months to a year in advance to “season” and let the steel acclimate to the temperature changes in the area it will be installed. They want it to contract, and expand for a few months at a minimum so it is stress relieved for the area. So they pull it off the specialized unit train and lay it on the right of way next to the tracks, on the ballast. Not being secured to any ties they conform to the larger contours of the ground like a noodle.

This is a long winded way to explain to you that your friend is correct that the rail is not made with an arch in it, but incorrect in his reasoning because the rail is not rigid enough to stay perfectly strait without support underneath it that is also perfectly strait and level. The rail bends, by design. Your friend is not good at critical thinking, or logic.

[26 Inf]

Your friend is not good at critical thinking, or logic.

Thanks for that explanation.

I've actually been on the locomotive simulator that, I believe, BNSF has at Olathe/Overland Park, Kansas.

Quite an experience to watch the engineer keep the train dead on speed as the train went up and down the steepest grades on the line with the simulator jarring as the train following bumped into slack on the downgrade and took out slack on the upgrade.

My use-of-force simulators paled by comparison.

My acquaintance, we aren't to friend status yet, was just being obtuse, he's actually very bright, retired LAFD and DSS Farsi translator.

[Coal Dragger]

Ah arguing for arguments sake. Sounds like my kind of a-hole!

[AKDoug]

I'll tell you that the most difficult class I took when I was still training to be a land surveyor was Geodetic Computations. Not only is the world an oblate spheroid, it also has spots that are higher and lower than the average that end up being anomalies in the WGS84 datum for navigation.

[morbidbattlecry]

A guy I know asked me if I believed the earth was round or flat. Being clever I answered neither, it is a sphere.

His evidence was that rail track rails aren't arched - I hope he was just being a smartass.

Anyways, that got me to thinking, how do the railroads start a grade - is it just a minor deflection at each joint or something else?

What about continuous rail?

Thanks!

Think of a series of straight lines that on average equal a curve. Over short lengths you can pretend the earth is flat at longer length you have to account for curvature.

[Pacific5th]

like anything else rail can bend. Go to a train track and watch closely as a train passes over it. You will see it bend up and down as the axels go over it. When we transition from flat to a grade its almost like a ramp.

[FromMyColdDeadHand]

I was in Italy at a train station and my buddy decided to put a coin on the tracks to flatten it. The train was at a walking pace and I was surprised that the train actually seemed to lift as it crushed the coin. The engineer was there, half out the window and as the engine clunked over the coin he shot us a crusty look.

[nightchief]

Railroad transitions from level track to a grade are done in the subgrade using spiral easements. This is also how track goes from a tangent to a curve. Its gradual and infinite from the point where the curvature (horizontal or vertical) starts transitioning to tangent or to level track. I am not a math person when it comes to building railroads, so the mathematics involved in calculating the spiral easement is not something I can provide a formula for.

[FromMyColdDeadHand]

Railroad transitions from level track to a grade are done in the subgrade using spiral easements. This is also how track goes from a tangent to a curve. Its gradual and infinite from the point where the curvature (horizontal or vertical) starts transitioning to tangent or to level track. I am not a math person when it comes to building railroads, so the mathematics involved in calculating the spiral easement is not something I can provide a formula for.

Spiral Easement (Wikipedia)

A track transition curve, or spiral easement, is a mathematically-calculated curve on a section of highway, or railroad track, in which a straight section changes into a curve. It is designed to prevent sudden changes in lateral (or centripetal) acceleration. In plane (viewed from above), the start of the transition of the horizontal curve is at infinite radius, and at the end of the transition, it has the same radius as the curve itself and so forms a very broad spiral. At the same time, in the vertical plane, the outside of the curve is gradually raised until the correct degree of bank is reached.

If such an easement were not applied, the lateral acceleration of a rail vehicle would change abruptly at one point (the tangent point where the straight track meets the curve), with undesirable results. With a road vehicle, the driver naturally applies the steering alteration in a gradual manner, and the curve is designed to permit that by using the same principle.

Interesting. Learn something new everyday.

[Coal Dragger]

The vertical change in the outside of the spiral easement also has to be adjusted for the average speed through the curve. Too high and slower moving trains risk toppling over to the inside, and too low a vertical adjustment could result in the wheel flanges climbing the ball of the rail on a fast moving train and launching off the outside rail. The normal answer is to err on the side of accommodating slower moving trains, that may also have heavy cars with high centers of gravity, and design the spiral easement for a slower speed.

This is one reason why we don’t have the easy ability to have high speed passenger service in this country. Passenger trains mostly share track with freight trains, and the track geometry that is optimal for freight means the passenger trains are forced to operate well below their potential.

[pinzgauer]

Model railroaders have the math the real railroads used. I used it on the curves for one layout. Then used an elipse string trick for some others.

[Diamondback]

Pinz, freelance or prototype? I collected model trains around the turn of the millennium, but never laid track because I couldn't muster everything required for the kind of high-speed passenger-train running (NYC 20th Century Limited--full-length, close-coupled 17-car streamliners at 90-100 scale mph) I wanted to do modeling the mainline where my family worked on it before WWII.

Dragger, if you can't comment about this I understand, but a month or so ago I saw a unit train of coal headed north out of Port of Tacoma, thought of you and wondered where it might be heading since that's not something we usually see around Puget Sound with our local reliance on hydropower.

[Coal Dragger]

No idea man. A quick search shows only one coal fired plant in Washington State at Centralia.

[nightchief]

but a month or so ago I saw a unit train of coal headed north out of Port of Tacoma,.

Some coal goes to Canada for export to the far east.

[Pacific5th]

Pinz, freelance or prototype? I collected model trains around the turn of the millennium, but never laid track because I couldn't muster everything required for the kind of high-speed passenger-train running (NYC 20th Century Limited--full-length, close-coupled 17-car streamliners at 90-100 scale mph) I wanted to do modeling the mainline where my family worked on it before WWII.

Dragger, if you can't comment about this I understand, but a month or so ago I saw a unit train of coal headed north out of Port of Tacoma, thought of you and wondered where it might be heading since that's not something we usually see around Puget Sound with our local reliance on hydropower.

That coal goes to Roberts Bank near Vancouver BC. Its exported to Asia from there. We run several of them a day and have for many years. I’m surprised it’s the first one you have seen. They come out of Montana and into Spokane. From there I get the pleasure of taking them to Pasco where they go down the river to Vancouver and then back north to Canada. We also have coal trains that go to a power plant in Centralia. The empty trains run back east over Stevens or Stampede Pass. We also hand over some to the UP in Spokane that they take to Boardman OR.

[26 Inf]

A lot of railroaders on this forum.

[Outlander Systems]

NAD83 (2011) masterrace.


I'll tell you that the most difficult class I took when I was still training to be a land surveyor was Geodetic Computations. Not only is the world an oblate spheroid, it also has spots that are higher and lower than the average that end up being anomalies in the WGS84 datum for navigation.

[AKDoug]

NAD83 (2011) masterrace.

Not in my wheelhouse anymore. I found that I made more money in my current business using different math :D

[1_click_off]

Is mainline rail a standard rating throughout the country? I want to say 110 or 115lbs? A place I worked at had 90lbs from what I remember. Was told this is the weight over a 3’ span? Maintenance said they were ok with every third cross tie being good. Man did we have a lot of derailments until they reworked the yard. One year we needed to put loads in the empty yard. That was a disaster. Got a lot of new rail and ties that year!

Was also told most derailments happen 14-19mph because that match’s the natural fq of the cars swaying with the typical splice lengths.

Have some tribal learning for operating an engine, but that is about all. That was 20 years ago. I still remember opening up the cabinet and throwing that knife switch to juice it up for a start. Anyone know if the above tidbits are close to accurate?

[Pacific5th]

Is mainline rail a standard rating throughout the country? I want to say 110 or 115lbs? A place I worked at had 90lbs from what I remember. Was told this is the weight over a 3’ span? Maintenance said they were ok with every third cross tie being good. Man did we have a lot of derailments until they reworked the yard. One year we needed to put loads in the empty yard. That was a disaster. Got a lot of new rail and ties that year!

Was also told most derailments happen 14-19mph because that match’s the natural fq of the cars swaying with the typical splice lengths.

Have some tribal learning for operating an engine, but that is about all. That was 20 years ago. I still remember opening up the cabinet and throwing that knife switch to juice it up for a start. Anyone know if the above tidbits are close to accurate?

Mainline rail is 132-140lbs now. The industry standard is like 286k cars now and you have to have heavy rail if you want to do that every day with multiple trains. Hell the average grain train I run is 15,000 tons coal trains are pushing 20,000 tons. Where I work we run 30-50 trains a day. They have lighter rail on branch’s and yard tracks though. I know of some 85lbs rail from the late 1890’s still in use in some obscure service and industry tracks.

13-21mph or something like that is bad on jointed rail. The cars will rock side to side and can derail at those speeds. We have instructions that state if your on jointed rail and can’t do above 21mph then you have to stay below 13mph. Most heavy main line track is continuous welded rail though and it’s not a issue.

The knife switch is the main power switch, kill it and you have no battery power. So yes it has to be on for the locomotive to function in any way.

[pinzgauer]

Pinz, freelance or prototype?

I'm rusty on the terminology, but I used the more appropriately scale flex track. I forget the exact math, but I want to say it was decreasing squares.

The interesting thing is I could not get it to match any ellipse. So it's something unique. It makes sense for a railroad engineer to use the approach they do because they're not making loops that need to look optically similar. But the official railroad approach is a pain to make matching curves on a small layout. (Think 4 by 8 flat top)

A properly radiused curve is a thing of beauty and is more noticeable in model railroads than full size. Then again I believe all full size curves are radiused, so we don't have a comparison. Well, maybe not the short loop tracks at the local railroad museum.

[jpmuscle]

NAD83 (2011) masterrace.

NERD

Somewhat related but Horseshoe Curve in Altoona, PA is a pretty cool engineering structure to behold.

https://en.m.wikipedia.org/wiki/Horseshoe_Curve_(Pennsylvania)

I’m trying to the pics I took when I was there last.


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