A train gap, more commonly referred to as a rail gap, is a small space intentionally left between two adjacent sections of railway track during installation. This gap is crucial for the safe operation and longevity of the railway line.
Understanding Rail Gaps
Based on industry practices and the provided reference:
A small gap is left between two subsequent rails while installing. The rails expand on account of thermal expansion due to increased temperature in summer.
This highlights the primary reason for the existence of these gaps.
Why are Rail Gaps Necessary?
The main purpose of leaving a gap between rails is to accommodate thermal expansion and contraction.
- Thermal Expansion: Railway tracks are typically made of steel. Like most materials, steel expands when heated and contracts when cooled. During hot summer months, the temperature of the rails can rise significantly due to the ambient temperature and direct sunlight.
- Preventing Buckling: If no gap or insufficient gap is left, the expanding rails have nowhere to go. This causes immense pressure to build up, leading to the tracks pushing against each other and potentially buckling or deforming significantly. This buckling is a major safety hazard and can cause derailments.
- Thermal Contraction: Conversely, in cold weather, the rails contract. The gaps allow for this contraction without putting excessive stress on the fasteners or potentially pulling the rail apart.
The Role of Temperature
The size of the gap left between rails is often calculated based on the expected temperature range of the location. Engineers determine the appropriate gap size to ensure the rails can expand and contract freely within that range.
Evolution of Rail Technology
While traditional jointed tracks with visible gaps are still used in some areas, modern railway lines often utilize Continuous Welded Rail (CWR). In CWR, rail sections are welded together to form very long segments, sometimes miles long.
- Continuous Welded Rail: In CWR, the problem of expansion is handled differently. The rails are typically installed and welded at a specific "stress-free" temperature. At temperatures above or below this, significant forces (compression in heat, tension in cold) build up within the rail. However, the track structure (ballast, sleepers, fasteners) is designed to resist these forces, preventing buckling or pulling apart, reducing or eliminating the need for small gaps along the main track length.
In conclusion, a train gap (or rail gap) is a vital feature in traditional jointed railway tracks, serving as a necessary buffer for thermal expansion and contraction to prevent dangerous track deformation.
