Overview
ISO 12357-2:2007 - "Commercial road vehicles - Drawbar couplings and eyes for rigid drawbars - Part 2: Strength tests for special applications" - defines test conditions and strength requirements for drawbar couplings and corresponding drawbar eyes used on rigid drawbar trailers and vehicle transport combinations. It applies when the trailer’s vertical static load (S-value) exceeds 10% of its design mass and/or is between 1 000 kg and 2 000 kg, and when technical masses exceed 3.5 t for vehicle transport combinations. The standard sets out static and dynamic test procedures, load calculations and acceptance criteria to ensure safe coupling performance under realistic towing conditions.
Key Topics and Requirements
- Scope and applicability
- Targets rigid drawbar trailers and special vehicle-transport combinations where vertical loading exceeds specified thresholds.
- Terminology and values
- Defines S-value (vertical static load), D-value (comparative longitudinal force) and V-value (comparative vertical force) and the calculation methods used to derive them.
- Load calculations
- Provides formulae for calculating D-value and V-value based on towing and trailer masses, drawbar geometry (x, L), and suspension-dependent acceleration factor (air vs other suspension).
- Dynamic testing
- Specifies dynamic test loads applied at the coupling point: horizontal sinusoidal loads (zero mean, amplitude proportional to D) and vertical sinusoidal loads (mean proportional to S, amplitude proportional to V). Vertical and horizontal components are applied asynchronously (frequency difference 1–3 %) to generate realistic multi-directional forces.
- Frequency limitations: selected test frequency shall not exceed 25 Hz and must avoid system natural frequencies.
- Cycle requirements: the standard defines the number of dynamic cycles for steel and requires agreement for other materials.
- Static testing
- Closure and locking devices must withstand a static opening force (0.25·D for most couplings; 0.1·D for cylindrical pins) without opening or damage.
- Acceptance criteria
- No permanent deformation, fractures, cracks or closure failures are permitted after testing.
Applications and Users
ISO 12357-2:2007 is used by:
- Coupling and drawbar manufacturers for product design verification and type approval.
- Test laboratories performing static and dynamic strength tests on coupling equipment.
- Vehicle OEMs and trailer builders to specify compliant towing interfaces for heavy rigid drawbar trailers and vehicle transporters.
- Regulatory bodies and certification agencies for conformity assessment and safety audits.
- Fleet operators and specifiers seeking durable, interchangeably safe couplings for heavy-duty towing.
Keywords: ISO 12357-2:2007, drawbar couplings, drawbar eyes, rigid drawbars, strength tests, dynamic tests, D-value, V-value, S-value, commercial road vehicles.
Related Standards
- ISO 12357-1 - Strength tests for general cargo centre-axle trailers
- ISO 1102 - 50 mm drawbar eye - Interchangeability
- ISO 3584 - Drawbar couplings - Interchangeability
- ISO 1176, UNECE R55-01 and EU Directive 94/20/EC - referenced for terminology and regulatory context