Railroad Curve Help

[40 CHAINS]

Hello fellow surveyors,

I need some expert help with deciphering the attached Railroad right of way map. I don't have a lot of experience working along railroads or looking at these maps and need to see if I can recreate the center of the right of way. See attached snippet from the map. I'm mostly interested in the highlighted notations and how to apply these in recreating the curve. From what I can gather this is not a spiral but I could be wrong.
Any help is appreciated.
Thank you

Chris

[mpallamary]

Heading out of town. Will try to get to if I can. Please note it is an ATSF Railroad line.

[Steve Martin]

T-1 means a Taper Curve (a simplified spiral) per #1 in the SP Taper Curve Table

The fellow that presented the CLSA Railroad seminar said that right of ways were acquired on the central curve radius. I believe that was true before a certain date as I have seen changing radii on Right of way for the SD&AE railroad.

Search this forum for a discussion on this. It seems like we have been over this ground before.

[dharri]

When the first railroads were constructed in the late 1800’s, they utilized tangents and simple circular curves. As the speed of the trains increased around the start of the twentieth century, it became necessary to transition the trains from the tangent section of the track to the central circular curve and out again. Prior to around 1930, this transition was accomplished with a series of “taper” curves. Taper curves are a number of compound curves that transition the train into the central circular curve and out of the central circular curve. Taper curves are compound curves, not spiral curves. Each railroad had their own unique set of taper curves contained in a book of tables.

I had difficulty reading the map excerpt so my numbers may not be correct.

1008+84.3 BC T1
This appears to indicate station 1008+84.3 beginning of curve to taper curve number 1 from the book of tables.

1010+54.7 CC 4° RT
This appears to indicate station 1010.547 compound curve for 4 degrees to the right. This information appears to relate to taper curve number 1.

TC 46° 50 3/4°
This appears to indicate a tangent curve with a degree of curvature of 46 degrees through a central of 50 ¾ degrees.

10?0+53.7 CC T1
This appears to indicate station 10?0+53.7 compound curve to taper curve number 1 from the book of tables.

1022+64.3 EC
This appears to indicate station 1022+64.3 end of curve.

It is very difficult to retrace the taper curves without the book of tables used to lay them out originally. It is my understanding that if the AT&SF taper curve tables are available, they would be in Chicago.

Typically the number of taper curve segments going into the main curve will be the same as coming out of the main curve. Typically the taper curve segments will have the same chord length ( many times 30’, 33’ or 50’) with a radius that decreases or increases depending upon whether you are going into the main curve or coming out of the main curve.

[E_Page]

I went to a RR survey seminar a few years back called Railroad Surveying 101 (or something like that). The speaker had been with one of the railroad companies his entire career and had a lot of knowledge.

According to him, although the centerlines were on spirals, as is the example you show in the OP, the RW curves were not spiral. I'd have to look it up in the manual he provided (it's at home), but if I recall correctly, the circular curve for the RW was offset from the central centerline curve (the circular part between the entering and exiting spirals).

Google Books has several old railroad alignment books. The one I've always used is by Lee Perkins. The speaker at RR 101 said that each RR company had slightly different definitions or layout methods for their spirals, but Perkins' methods and values work for the RRs in N CA. I just looked up the radius for a 4 degree curve. It's 1432.69'.

[40 CHAINS]

Thank you all for your insight.

Chris

[Dave Lindell]

50/sin2°=1432.68542

[mpallamary]

Good luck.

[mpallamary]

Not all railroads used the same formulas. As this is ATSF, they have their own formula as I recall.

[mpallamary]

I used to use the offset method when laying these out back in the 1970s.

It has been awhile.

https://www.xyht.com/professional-surve ... e-offsets/

[mpallamary]

See:

https://books.google.com/books?id=-lsyA ... ve&f=false

[mpallamary]

http://cc4w.net/spiral/SpiralTraining.pdf

[mpallamary]

This might help.

https://www.youtube.com/watch?reload=9&v=CCpi0eNks94

[Proud7191]

Evan, I think you are thinking of Charlie Tucker. He is truly a specialist in r/r. Just google the name. Funny story, I too took his class and before entering the class I formed a stereotype in my head. Levis, suspenders, work boots....When I entered the room there was a nicer old lady at the front of the class appearing to set up for class. I thought how wrong I am, Charlie is a woman.....about then, Mr. Tucker walked in to set up and the older lady was actually leaving. He matched my vision to a T. :) Good day! Jp

[E_Page]

That's the guy. One thing that sticks in my memory is that those who do it wrong, such as using spirals to lay out RW "should be shot!"

The way he said it, I was never quite sure if he was serious.

[Edward M Reading]

Evan, I think you are thinking of Charlie Tucker. He is truly a specialist in r/r. Just google the name. Funny story, I too took his class and before entering the class I formed a stereotype in my head. Levis, suspenders, work boots....When I entered the room there was a nicer old lady at the front of the class appearing to set up for class. I thought how wrong I am, Charlie is a woman.....about then, Mr. Tucker walked in to set up and the older lady was actually leaving. He matched my vision to a T. :) Good day! Jp

So, it wasn't Charlie from Top Gun?

[Steve Martin]

Attached is a rather poor copy of a portion of the old SPRR taper curve table as an FYI.

A Taper #1 would change 30 arc minutes in degree of curvature based upon 30' chord lengths.


Have you found a deed for the Right of Way? As others have mentioned, right of way could very likely be a simple curve based upon the total delta.

[Brian Christensen]

If any one needs a better copy of the SP taper tables, hit me up. Too big to attach here.
I found, somewhere on this forum, a slick little graphical exhibit of how to use the taper tables and how to put the R/W in with simple curves prepared by Michael Stanton. I have that as well.

[JoshPLS]

I also attended the CLSA Railroad 101 seminar. I still have the electronic files provided.

Click the link below to download the zip. I hope this helps you out.
https://cswst2.sharefile.com/d-sd4bf4c011104f4a9