Railroad Civil Engineering

This post cover some of the very basic information on laying out a railroad track.  It goes along with the other informational posts which preceded it.

Curves, Parabolas and Tangents:

When working on an outline of the key historic points I read the story of the granting of Landmark Status to the Denver and Rio Grande San Juan Extension – now the Cumbres and Toltec Scenic Railroad. That outline includes the 18 points of historic interest and the 4 historic sites and it also encompasses the American Society of Civil Engineers designation of the railroad as a Civil Engineering Historic Landmark.

The goal of the outline was the reduction of various aspects to bullet points serving as memory jogs for the numerous sections. A partial listing of sections is: Pre-history, Rio Grande Railroad History, Civil Engineering, Bridges and Trestles, Life Zones, Flora and Fauna, Section Houses and so forth.
 
The first step, for me, is reading the understandable information on this subject that is pertinent to the Cumbres and Toltec. This involves engineering reports of trestles and historic citations. These basic facts are initially condensed into written form and from that an outline is prepared.

This reduces many, many pages of writing and exhibits to several pages of very simple and understandable yet brief summary of key points, a working outline. The working outline is further reduced to bullet points that serve as reminders during a presentation but, that is still too long as the goal is a reduction to a single page. Remember this is not a lecture on engineering it is a dynamic description at a very rudimentary level which evolves with the journey and is but a small part of the overall presentation.

The final document was reduced from a draft outline of four pages to a single page. The easiest way to do that is a series of simple drawings of both Bridges and Trestles but also track alignments. The
Bridges and Trestles examples have been reduced to 5 simple drawings on an A5 sheet of paper.

The simple picture at the top of this post represents several basic principles in railroad civil engineering and helps a non-engineer, me, explain some very basic information. It was inserted and printed on an A5 sheet of paper and merged into the complete presentation. I didn’t get it down to one page but have finally reduced it to two sheets of paper. The overall presentation now rests at 10 double sided sheets of A5. That’s enough for the work I have ahead and I have a true Civil Engineer in the house, a simple call away, if I get bogged down. It is said “A picture is worth a thousand words”, and this is certainly the case for me in this instance.

Ruling Grade:

Now that we have the engineering notions well in hand a little conversation regarding the grade is in order.

The Cumbres & Toltec westbound is 64 miles long from Antonito, Colorado to its terminus in Chama, New Mexico. Over the 51 miles from Antonito to Cumbres Pass the railroad climbs about 2,200 feet. The grade is relatively steady and it climbs at 1.42% which from our previous discussion is about 75’ climb per mile. But that does not compute correctly because the 2,200 foot climb divided by 51 miles gives a climb of about 43’ per mile so what gives?, a "Ruling Grade."

No railroad can be built with a completely consistent grade but for each section of a given journey the steepest, “heaviest”, grade in that section of track is called the “Ruling Grade.” This means the section of track in question, Antonito to Cumbres, has one, or more, places with grades as heavy as, but not exceeding, 1.42%. A typical locomotive on the Cumbres & Toltec can haul over 30 loaded freight cars over this 51 mile section of track. If more cars are added an additional locomotive will be required. In any event the maximum number of cars is dictated by the “ruling grade.”

On the eastbound journey out of Chama, New Mexico the Ruling Grade is 4.0%. The section from Chama to Cumbres is a designated “Helper District.” This is because the same locomotive that pulled over 30 loaded freight cars from Antonito to Cumbres can only pull 12 cars from Chama to Cumbres. To pull more requires a second locomotive, a “Helper.” Trains of this type can have two locomotives on the front which is “double heading” or one cut in further down in the consist, say 10 or 12 cars behind the lead locomotive with another 10 or 12 behind the second locomotive, in such cases the second locomotive is called “a helper.”

Even today on modern railroads you see very long coal trains running with multiple locomotives on the head end and another locomotive or so at the rear or somewhere in the middle to handle the load.