Santa Fe’s Raton Pass Model Railroad: Unexpected Realism Part 1: Tonnage Rating of Locomotives

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The BNSF uses 6.2 horsepower per ton for calculating horsepower requirements on Tehachapi Pass in California. Tehachapi Pass has a ruling grade of 2.52%. Raton Pass has a ruling grade of 3.25%.

We have learned by experience operating trains up the grade on the layout that a typical HO scale diesel locomotive can only pull about 6ea. freight cars up the grade unassisted if the freight cars have been weighted to NMRA standards.

We wondered if the BNSF horsepower formula would be accurate on the model railroad as well. The switch lists used for our operating sessions provides the weight of every car used on the layout. We totaled up the prototype tonnage figures of every car on the layout and divided that figure by the number of cars to get an average weight in tons per car. The average weight came out to 59.1 tons per car.

Then we took the total horsepower of every diesel engine used on the layout and got an average horsepower rating for locomotives used on the layout. The average horsepower of locomotives used on the layout is 2,725.

Next, we took the 2.52% ruling grade figure from Tehachapi and divided it by 3.25 (Raton Pass) to get the difference in grade between Tehachapi and Raton. Raton Pass is 22.46 % steeper than Tehachapi. Multiplying Tehachapi’s horsepower rating of 6.2 by 22.46 percent gives us 7.59 for the horsepower rating for Raton Pass.

The average prototypical weight for 6ea. freight cars used on the layout (59.1 tons x 6) equals 354.6 tons. Therefore, to find the horsepower needed for six freight cars we multiplied 354.6 x 7.59, which gives us 2,691 horsepower, or one locomotive having an average horsepower of 2725.

Summary:

  1. Average prototypical weight of freight car used on layout – 59.1 tons
  2. Raton Pass is 22.46% steeper than Tehachapi Pass. (2.52 divided by 3.25)
  3. Horsepower rating of Raton Pass is 7.59 tons per horsepower.
  4. Six freight cars at 59.1 tons each equal 354.6 tons. (59.1 x 354.6 = 2,691 HP)
  5. 2,691 HP is within one-percent of our average horsepower rating of 2,725.
  6. Diesel locomotives used for mainline trains on Santa Fe’s Raton Pass Model Railroad.

GP30 – 2,250 HP

GP35 – 2,500 HP

GP38 –  2,000 HP

SD40-2 3,000 HP

SD45     3,600 HP

C30-7    3,000 HP

16,350 HP divided by 6 = 2,725 average HP per locomotive.

It was quite remarkable to learn that the ability of HO scale locomotives to pull freight cars up the 3% grade on the layout, matched the calculations used by the real railroad within one-percent. It will be interesting to see if the same holds true for steam locomotives used on the layout.

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The tortuous grades on Santa Fe’s Raton Pass Model Railroad are 3% just like the prototype. Raton Pass has the steepest ruling grade in the United States for a Class-One railroad. When the pass was acquired by Santa Fe in 1878 it immediately set the standard for locomotive development for the AT&SF. The high horsepower and tractive effort required to conquer the pass greatly influenced the unique development of locomotive technology on the AT&SF because no other railroad had to deal with 3% grades.

Hey! While you’re here why don’t you consider giving us a helping hand? 

Ways to Donate:

  1. GoFundMe Campaign for Colorado & Southern Coach 535.

Colorado & Southern Coach 535 an important piece of history from the early 20th Century that is worthy of restoration and preservaton.  It was built by the American Car & Foundry Company in 1905 Company for the Colorado & Southern Railway. We must get it inside to do a complete restoration to original condition and to protect the car from the elements.”

To donate to Colorado & Southern Coach 535 – click here.

  1. Santa Fe’s Raton Pass Model Railroad.

The Santa Fe’s Raton Pass Model Railroad is about much more than merely having fun with scale trains. The model railroad provides the Society with a testing and proving ground for the donated model railroad equipment in the Dean Collection and other collections we may acquire in the future.

To donate to Santa Fe’s Raton Pass Model Railroad – click here.

  1. Become a Member.

You can become a member of the Railroad Artifact Preservation Society for only $20.00 a year. Join the hundreds of RAPS members around the world.

To Purchase a RAPS Membership – click here.

  1. Visit our Store.

The Raps Store has many items not found elsewhere for the railroad enthusiast. Check out our unique books, videos, caps and other items.

To Visit the RAPS Store – click here.

The RAPS is a 501C3 Non-Profit Corporation.

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