90R Rail Dimensions and Specifications

The 90R rail profile is a specific standard, primarily defined by British Standards (BS), that serves a crucial role in various railway applications. Understanding the precise 90r rail dimensions is essential for engineers, procurement managers, and maintenance crews to ensure track compatibility, safety, and longevity. This rail section, weighing approximately 90 pounds per yard (or about 45 kg per meter), is classified as a heavy rail, suitable for mainlines, sidings, and industrial tracks that handle moderate traffic and axle loads. This technical guide explores the exact specifications of the 90R rail profile and the types of rail clips designed to fasten it securely.

Detailed Breakdown of 90R Rail Dimensions

The 90R rail profile, specified under standard BS11:1985, has a set of exact measurements that dictate its performance and application. These dimensions determine the rail’s strength, stability, and interaction with wheel flanges. The “R” in its designation typically signifies a flat-bottom rail design, which provides a wide, stable base for securing to sleepers. A thorough understanding of these metrics is the first step in proper track design and construction involving this profile.

Below is a comprehensive table outlining the key 90r rail dimensions in both metric and imperial units for clarity and ease of use in different engineering contexts.

Specification Table for BS 90R Rail

The head width of 66.67 mm provides a substantial contact surface for train wheels, distributing the load and reducing wear. The overall height of 142.88 mm gives the rail significant vertical stiffness, preventing it from bending excessively under the weight of a train. This is crucial for maintaining a smooth and safe running surface.

The base width of 127 mm (5 inches) creates a large, stable footprint on the sleeper. This wide base is critical for distributing the load over a greater area and preventing the rail from tilting or rotating under lateral forces, especially on curves. The web thickness connects the head and the base, providing shear strength and structural integrity. At nearly 14 mm, the 90R’s web is robust enough to handle the dynamic stresses of railway traffic.

Finally, the material composition is a critical aspect of its specification. 90R rail is typically manufactured from high-carbon steel grades like 900A or 1100, which are heat-treated to achieve a balance of hardness (for wear resistance) and ductility (to prevent brittle fracture).

Compatible Rail Clips for 90R Rail

Securing the 90R rail to the sleeper requires a reliable fastening system, and rail clips are the central component of this assembly. The primary function of a rail clip is to exert a constant clamping force, or “toe load,” on the rail’s base. This force prevents the rail from moving longitudinally (a phenomenon known as rail creep) and maintains the correct track gauge. The fastening system must also be resilient enough to absorb vibrations and thermal expansion and contraction of the rail.

Given its use in mainline and industrial settings, 90R rail is compatible with several types of robust fastening systems.

Elastic Rail Clips (E-Type Clips)

E-type clips are one of the most common and effective fasteners for flat-bottom rails like the 90R. Made from high-quality spring steel, these clips are designed to be driven into a shoulder that is cast into a concrete sleeper or attached to a baseplate on a wooden sleeper. Their unique shape allows them to flex upon installation, creating a consistent and lasting clamping force on the rail foot.

For a 90 lb rail, medium-duty E-type clips are typically used. These clips provide sufficient toe load to secure the rail against the dynamic forces of moderate-tonnage traffic without being over-specified, which would add unnecessary cost.

Specifications for Compatible E-Type Clips:

• Material: Forged Spring Steel (e.g., 60Si2MnA)
• Diameter: Typically 18 mm or 20 mm for this rail weight class.
• Hardness: 44-48 HRC, ensuring long-term elasticity and resistance to deformation.
• Fatigue Life: Engineered to withstand millions of load cycles without failure.
• Toe Load: A 20 mm E-type clip (like an E2001 or E2007) can provide a toe load of approximately 1100-1400 kgf, which is more than adequate for securing 90R rail.

Bolted Rail Clips (Tee and Crane Clips)

In some applications, particularly in industrial yards, crane ways, or sections with jointed track, bolted clips are preferred. These one-piece or two-piece clips are fastened using track bolts or hook bolts that pass through the sleeper or a steel baseplate. While they may not offer the same level of elasticity as an E-clip, they provide a very strong and rigid fastening.

The “Rail Clip 103,” for example, is a common type of bolted clip designed for use with rails in the 55 lb to 100 lb range, making it a perfect fit for the 90R profile. These clips can be either bolted down or welded to a steel structure, offering versatility in installation. They are forged from steel and feature an oval hole to accommodate a standard track bolt.

Specifications for Compatible Bolted Clips:

• Material: Forged Steel
• Installation: Secured with hook bolts or T-bolts. Some variants are weldable.
• Application: Ideal for jointed track, turnouts, and industrial settings where high rigidity is needed.
• Compatibility: Designed to fit the foot geometry of ASCE and BS rail profiles, including 90R.
• Weight: A typical clip for this rail size weighs around 0.75 lbs (0.34 kg).

The choice between an elastic fastening system and a more rigid bolted system depends on the specific requirements of the track. For continuous welded rail (CWR) on mainlines, elastic clips are almost always the superior choice due to their ability to manage thermal stresses and absorb vibration. For sidings, yards, and jointed track, the simplicity and strength of bolted clips can be a practical and cost-effective solution.