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The Nabla clip is a specialized elastic railway fastening component, named for its distinctive nabla shape. It is primarily used to secure steel rails to concrete or wooden sleepers, providing dynamic stability through a controlled clamping force.
Key Features
Key Features
Elasticity & Damping: Designed to effectively absorb and disperse vibrations and shock forces from passing trains, preventing track loosening.
Dynamic Toe Load: When the fastening nut is torqued, the blade-like shape of the clip generates a stable "toe load" on the rail foot.
Durability: High-quality alloy spring steel (e.g., 60Si2MnA or 60Si2CrA). High-performance variants are tested for up to 200 million load cycles.
Corrosion Resistance: Red painting or zinc plating to withstand harsh environments like coastal areas or mines.
System Components
System Components
A complete Nabla fastening system generally includes:
Nabla Clip (Blade): The primary elastic element.
Screw Spike/Anchor Screw: Secures the assembly into the sleeper; often requires a torque of 250–400 Nm to reach the required toe load.
Insulator: Made of reinforced nylon (PA66) to provide electrical insulation and lateral stability.
Rail Pad: A resilient rubber or plastic cushion placed between the rail and sleeper to reduce noise and wear.
Spring Washer & Nut: Used to maintain tension on the screw spike.
Common Applications
Common Applications
High-Speed Rail: Widely used on French TGV lines and Chinese high-speed networks (e.g., Wuhan–Guangzhou) due to its reliability at speeds exceeding 300 km/h.
Urban Transit: Favored for Trams, Metros, and Light Rail (LRT) for its noise reduction and easy maintenance (e.g., Nabla Evolution system).
Heavy-Haul & Freight: Extensively applied in ore transport railways in North Africa (Algeria, Morocco) and South Africa because of its high lateral force absorption.
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