Overview
ISO 7140:1985 establishes a standardized laboratory measurement method to determine the dynamic performance of cross-country skis. Specifically, it focuses on measuring the residual camber height and length as a function of applied load, a process commonly known as the flattening test. This method is essential to understand how skis behave under load, influencing performance aspects such as glide and kick during skiing. It applies to cross-country skis that are 130 cm and longer.
The standard was developed by ISO Technical Committee ISO/TC 83, which specializes in sports and recreational equipment. It aims to provide accurate, repeatable test procedures and parameters valuable for ski manufacturers, testers, and technically informed consumers.
Key Topics
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Dynamic Performance Measurement
The standard specifies how to quantify two critical parameters under load:
- Residual Camber Height (hRF): The vertical distance between the ski’s running surface and a flat horizontal surface when a load is applied. This reflects how much the ski flattens.
- Residual Camber Length (IRF): The length of the ski’s running surface that remains off the flat surface under load.
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Contact Load (FC):
This load measurement quantifies the minimal force needed to bring the ski’s center into contact with the snow. It directly affects ski friction characteristics during gliding and kicking.
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Standard Camber Length (IRs):
Represents the length of the ski base not touching the snow at a defined standard load, associated with average skier weight, influencing grip on various snow conditions.
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Equipment and Procedure
- Uses a flat beam surface with strict flatness tolerance (0.1 mm) for testing.
- Loading devices exert perpendicular force at a defined point located 8 cm behind the binding mounting point.
- Precision instruments like dial indicators (accuracy ±0.05 mm) and feeler gauges are used for measurements.
- Tests are conducted under controlled climatic conditions (23°C/50% RH and -10°C for testing temperature).
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Data Evaluation and Presentation
The results are typically plotted graphically:
- Residual camber height vs. load on semi-logarithmic scales.
- Residual camber length vs. load on linear scales.
This graphical approach assists in extracting parameters such as contact load and standard residual camber length.
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Applicability
Applies to adult and junior skis with nominal lengths from 130 cm to over 220 cm. Different test loads are defined depending on ski length.
Applications
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Ski Manufacturing:
Allows ski producers to characterize ski stiffness and dynamic response with precision, aiding in designing skis optimized for specific skier weights and snow conditions.
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Quality Control:
Enables laboratories and manufacturers to ensure ski production consistency by quantifying camber properties and mechanical behavior under load.
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Product Selection and Consumer Guidance:
Though primarily designed for specialists, simplified parameter extraction supports consumers and retailers in choosing skis matching skill levels, weight, and usage conditions.
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Research and Development:
Provides a scientifically validated method for testing innovations in ski design, materials, and construction techniques.
Related Standards
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ISO 6283: Skis - Terms and Definitions
Defines vocabulary and terminology related to ski equipment used in conjunction with ISO 7140.
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ISO 554: Standard Atmospheres for Conditioning and/or Testing
Specifies environmental conditions required to assure reproducibility and comparability of physical tests such as the flattening test.
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Other standards on cross-country ski bindings and materials may complement the understanding of ski performance in applied contexts.
Keywords: ISO 7140, cross-country skis, dynamic performance, residual camber height, residual camber length, flattening test, contact load, standard camber length, ski testing, laboratory measurement, sports equipment standards, ski stiffness testing.