The term railroad size is a core concept in railway engineering, defining the specific dimensions and weight of a rail profile. This specification is critical, as it dictates a track’s load-bearing capacity, durability, and overall safety. Choosing the correct railroad size requires a careful analysis of factors like axle loads, traffic density, and operational speeds. This guide provides an in-depth exploration of railroad size classifications and the essential clips used to secure them, forming the backbone of a stable and reliable railway system.
Railroad Size
A railroad’s size is primarily classified by its weight per unit of length—pounds per yard (lbs/yd) in North America or kilograms per meter (kg/m) elsewhere. This weight directly reflects the rail’s cross-sectional area and its ability to withstand immense vertical and lateral forces from passing trains. Key dimensions defining a railroad size include its height, the width of its base (or foot), the width of its head, and the thickness of its central web.
Heavier rails offer greater stiffness and resistance to wear, making them ideal for main lines with high traffic volumes and heavy axle loads. Lighter rails are typically used for industrial tracks, branch lines, or yard applications where the operational demands are less severe. The appropriate railroad size ensures that tracks can safely handle their intended traffic over a long service life.
North American Railroad Size Standards (ASCE/AREA)
In the United States and Canada, rail profiles are standardized by the American Society of Civil Engineers (ASCE) and the American Railway Engineering and Maintenance-of-Way Association (AREA). These standards cover a broad spectrum of sizes, from light industrial rails to heavy-duty profiles for Class I freight lines.
Table 1: Common North American Railroad Size Specifications
|
Rail Type |
Nominal Weight (lbs/yd) |
Height (inches) |
Base Width (inches) |
Head Width (inches) |
|
ASCE 60 |
60 |
4.25 |
4.25 |
2.38 |
|
ASCE 85 |
85 |
5.19 |
5.19 |
2.56 |
|
90 RA |
90 |
5.63 |
5.13 |
2.56 |
|
115 RE |
115 |
6.63 |
5.50 |
2.72 |
|
132 RE |
132 |
7.13 |
6.00 |
3.00 |
|
136 RE |
136 |
7.31 |
6.00 |
2.94 |
The designation, such as “136 RE,” not only signifies the weight but also a specific geometry designed for modern heavy-haul environments. The taller profile and thicker web provide the strength needed to manage constant, heavy loads.
European Railroad Size Standards (EN 13674)
In Europe and many other regions, rail profiles adhere to the EN 13674 standard. Rails are designated by their mass in kg/m, such as 60E1 (also known as UIC60). These profiles are optimized for use with concrete sleepers and are the standard for high-speed networks.
Table 2: European Railroad Size Dimensions
|
Rail Profile |
Nominal Weight (kg/m) |
Height (mm) |
Base Width (mm) |
Head Width (mm) |
|
49E1 (S49) |
49.39 |
149 |
125 |
67 |
|
54E1 (UIC54) |
54.77 |
159 |
140 |
70 |
|
60E1 (UIC60) |
60.21 |
172 |
150 |
72 |
The 60E1 profile’s mass and height provide the rigidity required to maintain precise track geometry at speeds over 300 km/h, making it a cornerstone of modern high-speed rail.
Railroad Clips
While the railroad size determines a track’s strength, rail clips are the fasteners that hold the system together. These elastic components apply a consistent clamping force, known as toe load, to the rail’s foot. This force is essential for preventing longitudinal slippage from thermal expansion and braking forces, and for maintaining the correct track gauge against lateral pressures.
Choosing the right clip is just as important as selecting the right rail. The clip must be compatible with the specific railroad size, sleeper type, and the operational demands of the line to prevent loose rails and potential derailments.
Types of Rail Clips and Their Applications
Different railway applications demand different fastening solutions. The design of a rail clip is tailored to provide the right balance of clamping force, elasticity, and ease of maintenance for its intended environment.
1. E-Type Clips
The E-clip is one of the most widely used rail fasteners in the world. Its simple but effective design makes it suitable for a variety of applications. It is driven into a cast-in shoulder on a concrete sleeper or into a baseplate on a wooden sleeper, where its spring action provides the clamping force.
- Best for: Conventional freight, passenger transit, and many heavy-haul lines.
- Compatible with: Most standard railroad size profiles.
2. SKL Tension Clips
Common in European systems and on high-speed lines, SKL clips are part of a fastening system that includes a screw spike and a plastic dowel set into the sleeper. The screw tensions the clip, allowing for precise control over the clamping force.
- Best for: High-speed rail and heavy mixed-traffic lines requiring excellent vibration absorption.
- Features: High fatigue strength and consistent performance under dynamic loads.
3. Nabla Clips
The Nabla fastening system uses a blade-like clip that is tensioned by a bolt. It provides strong clamping force and is effective at preventing rail rollover, particularly on sharp curves.
- Best for: Tracks with significant lateral forces, such as in metro systems or on tightly curved lines.
4. Fastclips
Developed by Pandrol, the Fastclip system is a pre-assembled fastener that is mechanically driven into place. Its design simplifies installation and maintenance, significantly reducing track possession times.
- Best for: High-density lines where quick installation and replacement are critical, including high-speed and heavy-haul applications.
Railroad Size and Clips for the Job
The choice of railroad size and its accompanying clips is an engineering decision based on a thorough assessment of the track’s future use.
- Heavy-Haul Freight: Lines that transport heavy commodities like iron ore or coal require the most robust tracks. A heavy railroad size, such as 136 RE or greater, is necessary to support axle loads that can exceed 35 metric tons. The clips must provide an exceptionally high toe load to prevent any rail movement.
- High-Speed Passenger: For high-speed lines, ride quality and track stability are paramount. A heavy railroad size like 60E1 (UIC60) is used to ensure rigidity and a smooth running surface. The fastening system must dampen vibrations to protect the track structure and minimize noise.
- Mixed Traffic and Conventional Lines: Most railways carry a mix of passenger and freight trains. A versatile railroad size like 115 RE or 54E1 offers a good balance of strength and cost-effectiveness. E-clips are a common and reliable choice for these applications.
Ultimately, the integrity of a railway depends on the synergy between its components. An appropriately selected railroad size provides the necessary strength, while the correct clips ensure that the rails remain securely in place, delivering a safe and reliable path for every train.
FAQs
What is the standard weight of a railroad size?
There is no single standard weight. Common mainline sizes range from 115 to 141 lbs/yd (approximately 57 to 70 kg/m). The appropriate weight depends on the traffic type, axle load, and speed requirements of the railway line.
What materials are used in rail clips?
Rail clips are typically forged from high-strength spring steel alloys like 60Si2MnA or 60Si2CrA. These materials provide the necessary elasticity and fatigue resistance to withstand millions of loading cycles without losing their clamping force.
How do railroad clips maintain track stability?
Clips exert a continuous downward pressure on the rail foot, pinning it to the sleeper. This clamping force creates frictional resistance that prevents the rail from moving either longitudinally or laterally, ensuring the track structure remains stable and safe.
What are the tolerances for railroad sizes?
Tolerances for railroad sizes are very strict, especially for high-speed lines. For example, a high-speed rail profile may have a height tolerance of just ±0.5 mm and a maximum flatness deviation of 0.3 mm over a short distance to ensure a smooth ride.
Which clip is best for heavy-haul railways?
For heavy-haul applications, robust clips with a very high clamping force and excellent fatigue resistance are required. Models like the E2009, Deenik clip, and certain SKL variants (e.g., SKL 75) are specifically designed to handle the extreme stresses of high axle loads.
