PRR Railroad-1936 Track chart

[jk71062]

Here is a stupid question. I have a 1936 Pennsylvania Railroad Track Chart which is from the engineering dept.
It shows basic track layout in one column, percent of grades in the second, and the third shows curvature. They show the curvature as a straight line broken by semi circles listing degrees such as 3*, 6*, 6*30' etc. Also I am assuming the semi circles position to the straight line, either right or left tells the direction. Is there a formula to convert the above info to radius?
Thanks
John

 

[tincan]

Arc Definition.....R = 5729.58/D
Chord Definition...R = 50/Sin(D/2)
for a 3* curve R(arc) = 1909.86'
R(Chord) = 1919.08'

R = radius
D = degree of curve

 

[OldPaperMaker]

You might want to be careful here. Most railroad curves are Transition Spiral Curves.The formulas noted in tincan's post are for Circular Curves.
I fished out an old copy of "Route Surveying and Design", Fourth Edition by Thomas F. Hickerson. Chaper 6, pages 147 to page 189 will tell you more than you ever wanted to know about Transition Sprials. The formulas and notation of variables are to long for my poor keyboarding skills to endure.

 

[jk71062]

Thank You

 

[jheidt2543]

There are a lot of surveying, route location and civil engineering books that would have information on railway curves. However, the one I like, because it has some good historical information too, may be hard to find (you might try powells.com or bookfinder.com).

"Railroad Curves and Earthwork", by C. Frank Allen

My copy is the 7th edition, printed in 1931. It is full of charts, tables and graphs from the days before hand held calculators and computers. The first copyrighted edition was 1889, so there is also a lot of historical information in this little book too. It is 290 pages, but shirt pocket size - so it was originally meant for field use too.

Oldpapermaker is right, besides simple circular curves, compound curves, reversed curves, turnouts cicular and spiral, and spiral curves were all used. They all had their specific uses and calculation requirements. But, if you use the old KISS priciple and stick with simple circular curves, using the formulas tincan noted, you can't get in too much trouble.

Hope this is some help!