Cross Tracks and Rail Clip Specifications

Understanding the intricate components of a railway system is essential for ensuring its safety, reliability, and longevity. The foundational elements, such as the rails that form the cross tracks and the clips that secure them, are governed by precise engineering standards. These specifications dictate everything from the dimensions and weight of the rail to the design and function of the fastening systems. A comprehensive grasp of these details is not just for engineers but for anyone involved in the procurement, installation, and maintenance of railway infrastructure. This detailed guide explores the critical specifications for various rail sections and the essential role of rail clips in maintaining the integrity of the track structure.

Rail Specifications for Cross Tracks

The American Society of Civil Engineers (ASCE) and the American Railway Engineering and Maintenance-of-Way Association (AREMA) have established standards that define the physical characteristics of rails. These specifications ensure uniformity and interchangeability, which are vital for a vast and interconnected network. Rail is categorized by its weight per yard (e.g., 115-lb rail means it weighs 115 pounds for every three feet of length). Heavier rails are typically used on mainline tracks with high traffic volume and heavy loads, while lighter rails are suitable for industrial sidings, yards, or light-traffic lines.

The profile of a rail—comprising the head, web, and base—is meticulously designed to withstand immense forces. The head provides the contact surface for the train wheels, the web gives the rail its vertical strength, and the base distributes the load to the tie plates and crossties. The dimensions of these components are critical for proper performance and compatibility with other track materials like joint bars and rail clips. The following table provides a comprehensive overview of rail dimensions for various ASCE sections, which are commonly used in building cross tracks across North America.

ASCE Rail Section Dimensions

This table outlines key dimensional data for a wide range of ASCE rail sections. These specifications are crucial for planning, construction, and maintenance activities.

Note: Dimensions are standard and may have slight variations based on manufacturer and wear.

Choosing the correct rail section is a balance between performance requirements and economic considerations. Mainline cross tracks that handle heavy axle loads and high-speed trains demand robust sections like 136-lb or 141-lb CWR (Continuous Welded Rail). In contrast, a yard track or industrial spur might function perfectly with 85-lb or 90-lb jointed rail. Using an oversized rail for a low-demand application results in unnecessary material and installation costs. Conversely, using an undersized rail can lead to premature wear, increased maintenance, and potential safety hazards.

Rail Clips in Track Stability

Once the appropriate rail is selected, it must be securely fastened to the crossties. This is where rail clips and other fastening components come into play. Rail clips are integral parts of the fastening system that hold the rail to the tie plate, preventing both lateral and longitudinal movement. Their function is essential for maintaining proper track gauge, reducing rail stress, and ensuring the overall stability of the track structure.

An effective fastening system must provide:

• Clamping Force: Sufficient pressure to hold the rail firmly against the tie plate.
• Longitudinal Restraint: Resistance against the rail moving lengthwise due to thermal expansion/contraction and train dynamics.
• Gauge Control: Maintaining the precise distance between the two rails.
• Elasticity: The ability to absorb vibrations and impacts from passing trains, reducing wear on all track components.

Rail clips are not a one-size-fits-all solution. Their design is specific to the type of rail, tie plate, and crosstie (wood, concrete, or steel) being used.

Types of Rail Clips

The evolution of railway technology has led to a variety of rail clip designs, each with specific advantages.

1. Cut Spikes: While not a “clip” in the modern sense, the traditional cut spike is the simplest form of rail fastening for wood ties. Driven through holes in the tie plate, they hold the rail in place by the shear strength of the spike. This system offers limited clamping force and longitudinal restraint, making it more suitable for lower-speed, lighter-tonnage tracks.
2. Screw Spikes: Offering greater holding power than cut spikes, screw spikes are threaded into pre-drilled holes in wood ties. They provide better resistance to vertical pull-out and are often used in high-wear areas like curves and turnouts.
3. Elastic Clips: These are the standard for modern railway systems, especially those with concrete ties. Elastic clips, such as the Pandrol ‘e-Clip’ or the Vossloh clip, are designed to be driven into a shoulder cast into the concrete tie or bolted onto the tie plate. They exert a constant, spring-like clamping force on the rail base. This elasticity allows the rail to move vertically under load without losing its secure fastening, which dampens vibration and reduces component fatigue. There are numerous models of elastic clips, each providing a different toe load (the downward force exerted on the rail foot) to suit various track conditions.
4. Specialty Crane Rail Clips: For industrial applications involving overhead cranes or gantry systems, specialized crane rail clips are used. These are often weldable or bolted clips designed to handle the unique side-thrust and heavy, slow-moving loads characteristic of crane operations. Examples include models like the #103, #106, #62, and #114 clips, which are designed to fasten the base of a crane or tee rail directly to a steel girder or concrete foundation.

Installation and Maintenance of Rail Clips

Proper installation is paramount to the performance of any rail clip. An improperly installed clip can lead to loose rail, gauge widening, and excessive wear.

• For Elastic Clips: Installation is typically done with a hydraulic or manual tool that pushes the clip into its housing. It’s critical to ensure the clip is fully seated and that the insulators, if used, are correctly positioned. During inspections, maintenance crews look for broken, loose, or missing clips. A missing clip in a section of CWR can create a potential weak point, increasing the risk of a track buckle in hot weather.
• For Spike Systems: Spikes should be driven vertically and square, with the head making firm contact with the rail base without over-driving, which can damage the wood tie. Over time, spikes can work themselves loose due to the vibration of passing trains. Regular inspection and re-driving or replacement of “high” spikes are standard maintenance procedures.
• Torque Requirements: For bolted clip systems and screw spikes, adhering to the manufacturer’s specified torque is essential. Over-tightening can damage the bolt or the clip, while under-tightening results in insufficient clamping force. Torque should be checked periodically as part of the track maintenance schedule.

The integrity of cross tracks depends on the synergy between the rail and its fastening system. While the rail provides the running surface, the rail clips are the unsung heroes that hold everything together. They manage the immense dynamic forces generated by multi-ton trains, accommodate thermal expansion, and maintain the precise geometry of the track. By adhering to established specifications for both rails and their corresponding clips, railways can build and maintain a safe, efficient, and durable network for generations to come.

Frequently Asked Questions (FAQs)

1. What are rail clips used for?
   Rail clips are essential fasteners used to secure the rail to the tie plate and crosstie. They prevent lateral and longitudinal movement, maintain track gauge, and provide the clamping force needed to create a stable track structure.
2. What is the difference between 115-lb and 136-lb rail?
   The number refers to the weight of the rail in pounds per yard. A 136-lb rail is heavier and has a larger cross-sectional area than a 115-lb rail, making it stronger and more suitable for high-tonnage mainline tracks.
3. Why are elastic clips preferred on modern railways?
   Elastic clips provide a constant, spring-like clamping force that holds the rail securely while allowing for slight vertical movement. This elasticity absorbs vibrations, reduces wear on components, and is critical for the performance of concrete ties and CWR.
4. How often should rail clips be inspected?
   Rail clips and fastenings are inspected as part of regular track inspections. The frequency depends on factors like track class, tonnage, and environmental conditions, but they are typically checked multiple times per year by maintenance crews.
5. Can you use different types of clips on the same track?
   Generally, it is best practice to use a consistent fastening system within a track segment. Mixing types, such as cut spikes and elastic clips, can create inconsistencies in track stiffness and restraint, potentially leading to maintenance issues.