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Questions About Curved Track Installations? We’ve Got Answers

MAY 25, 2021 PUBLISHED BY HKLINGEL
RailWorks

By Matt Violin, Sr. Director of Sales & Marketing at NARSTCO

Let’s face it – since the onset of the pandemic and community lockdowns, we’ve all spent a great deal of time at home, and a great deal of time shopping online. That robust demand is spurring demand and interest in shipping by rail, meaning shippers are adding new rail service or expanding their existing infrastructure. While adding to or upgrading existing infrastructure may seem overwhelming, there are many resources available to rail-served facilities looking to upgrade.

Every track, every customer, and every network are unique. And not all track is a perfectly straight line. The addition of lead tracks or sections of curved track may be a part of an upgrade project. Different materials, including steel ties and turnouts, offer a great deal of operational benefits. But like any projects, there are unique elements to take into consideration, like ballast, rail gauge, and tie spacing, among others, but proper planning and project execution can help the process move along smoothly.

Ballast: When designing curved track, a quality ballast section and size is necessary to achieve optimal performance. Larger ballast, such as AREMA 3, 4 or 4A, helps improve track stability in relation to surface and line. 

In conjunction with the use of NARSTCO steel ties, the larger ballast is compacted with a mechanical tamper to fill the underside of tie, cribs, and shoulder. When tamping steel tie track, appropriate adjustments must be made on the tamper to raise the tamping tool insertion depth and to tamp the center of tie. NARSTCO’s steel tie design with spaded ends increases lateral stability and holds line more than alternative tie products. With both spaded tie ends interacting with the ballast shoulder and ballast compacted under the tie, there is superior hold achieved. Ensuring ballast is correctly compacted and regulated to the top of tie or just above is a key to properly constructed steel tie track.

Rail gauge: Many railroads and standards specify the rail gauge required for curved sections of track and when constructing higher degree curved track the gauge is typically opened up to reduce the amount of rail friction and wear. 

For example, some railroads specify the rail gauge to be set at 57 inches for curves between 17-20 degrees. NARSTCO’s manufacturing process allows for the rail seat holes to be adjusted to match the various rail and gauge requirements on each project.  

Another feature that is typically overlooked is the ease of transposing rails with steel ties, if that is ever required over the life of track. The removal of four e clips per tie and moving rail is extremely easy and quick. Steel ties do not require re-gauging on curves as required with wood ties. Wide gauge on curves with wood ties are a result of wood deterioration around spikes causing hole elongation, plate cutting and spike pull-ups. Therefore, the outcome of using steel ties is longer lasting rail and better performing track

Tie spacing: Another area that is commonly specified on curved track projects is the adjustment of standard tie spacing (i.e. 24 inch tie centers for steel ties). As with rail gauge, many railroads and project specs require the ties to be spaced more closely together in curves to help increase lateral resistance and hold. 

For example, NARSTCO standards recommend that steel ties located in curves over 12 degrees are spaced at 20-inch centers.  Depending on the type of track application and operation a couple tie models can be considered. In high degree curved sections of track with elevated speeds and heavy tonnage a deeper spade tie may be necessary. NARSTCO’s ‘H’ model ties with increased spade depth are ideal. For slower speed, lower tonnage curved sections of track NARSTCO’s ‘M’ model ties are typically used. 

Regardless of the type of tie being used proper track maintenance and inspections is a must.  With NARSTCO steel tie track, ballast inspection holes should be a part of any inspection program to ensure ballast is properly compacted under the tie.

Please reach out to NARSTCO at 972-775-5560 with any questions or inquiries.