ISO 7641:2012
(Main)Road vehicles - Trailers up to 3,5 t - Calculation of the mechanical strength of steel drawbars
Road vehicles - Trailers up to 3,5 t - Calculation of the mechanical strength of steel drawbars
ISO 7641:2012 gives a simplified procedure for the calculation of the mechanical strength of steel drawbars, whether there are welds or not, for centre-axle trailers Categories O1 and O2 as specified in the UNECE, Consolidated Resolution on the Construction of Vehicles (R.E.3). Consequently, it only applies to simple constructions that enable a calculation in bending.
Véhicules routiers — Remorques jusqu'à 3,5 t — Calcul de la résistance mécanique des timons en acier
General Information
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Overview
ISO 7641:2012 - Road vehicles: Trailers up to 3,5 t - Calculation of the mechanical strength of steel drawbars - provides a simplified, calculation-based procedure for assessing the mechanical strength of steel drawbars used on centre‑axle trailers (Categories O1 and O2 per UNECE R.E.3). The standard applies to simple drawbar constructions that can be evaluated by bending calculations and covers both welded and non‑welded steel drawbars for trailers with a maximum mass up to 3.5 t.
Keywords: ISO 7641, drawbar calculation, trailers up to 3.5 t, steel drawbars, UNECE R.E.3, mechanical strength
Key topics and technical requirements
- Scope and applicability: Simplified bending calculations for simple drawbar geometries (single tube, two arms, V‑shaped, adjustable, etc.). Centre‑axle trailer focus; dynamic tests required if static force limits are exceeded.
- Definitions & symbols: Distances (l, e, ex), trailer mass P, longitudinal force D, static vertical force S - used to locate maximum bending moments and compute stresses.
- Maximum static vertical force (S): Limits on S as a function of trailer GVW are specified; exceeding those limits requires dynamic validation rather than calculation alone.
- Material and weldability: For welded drawbars, steel grades must contain ≤ 0.25% carbon and have guaranteed weldability; welding procedures (preheating, etc.) per manufacturer’s instructions must be followed.
- Bending moment calculations:
- Provided formulae for maximum bending moment M for braked and non‑braked trailers, with different coefficients for l ≤ 2.5 m and l > 2.5 m (including a k coefficient for long drawbars).
- Special treatment when e/l > 0.15: calculate multiple moments (Mf, MD, MP) and use the largest.
- Permissible stress:
- Stress σ = M / W with section modulus W.
- Allowed stress ranges differ for welded versus non‑welded drawbars (expressed relative to yield σs and ultimate σc).
- Chassis interface: Trailer manufacturer must ensure chassis parts can withstand forces transmitted by the drawbar.
Practical applications - who uses ISO 7641
- Trailer designers and structural engineers performing strength checks on steel drawbars.
- Component manufacturers (drawbars, coupling heads, drawbar eyes) preparing technical dossiers.
- Compliance and homologation specialists assessing conformity with UNECE R.E.3 for O1/O2 trailers.
- Test laboratories deciding when calculation suffices vs. when dynamic testing is required.
- Procurement and quality teams specifying material/welding requirements for drawbar production.
Related standards
- UNECE Consolidated Resolution on the Construction of Vehicles (R.E.3) - referenced normative regulation.
- ISO 1176 - masses vocabulary (bibliography reference in ISO 7641).
Frequently Asked Questions
ISO 7641:2012 is a standard published by the International Organization for Standardization (ISO). Its full title is "Road vehicles - Trailers up to 3,5 t - Calculation of the mechanical strength of steel drawbars". This standard covers: ISO 7641:2012 gives a simplified procedure for the calculation of the mechanical strength of steel drawbars, whether there are welds or not, for centre-axle trailers Categories O1 and O2 as specified in the UNECE, Consolidated Resolution on the Construction of Vehicles (R.E.3). Consequently, it only applies to simple constructions that enable a calculation in bending.
ISO 7641:2012 gives a simplified procedure for the calculation of the mechanical strength of steel drawbars, whether there are welds or not, for centre-axle trailers Categories O1 and O2 as specified in the UNECE, Consolidated Resolution on the Construction of Vehicles (R.E.3). Consequently, it only applies to simple constructions that enable a calculation in bending.
ISO 7641:2012 is classified under the following ICS (International Classification for Standards) categories: 43.040.70 - Couplings. The ICS classification helps identify the subject area and facilitates finding related standards.
ISO 7641:2012 has the following relationships with other standards: It is inter standard links to ISO 7641-1:1983. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
You can purchase ISO 7641:2012 directly from iTeh Standards. The document is available in PDF format and is delivered instantly after payment. Add the standard to your cart and complete the secure checkout process. iTeh Standards is an authorized distributor of ISO standards.
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 7641
First edition
2012-11-15
Road vehicles — Trailers up to 3,5 t —
Calculation of the mechanical strength
of steel drawbars
Véhicules routiers — Remorques jusqu’à 3,5 t — Calcul de la
résistance mécanique des timons en acier
Reference number
©
ISO 2012
© ISO 2012
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ii © ISO 2012 – All rights reserved
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions . 1
3.2 Symbols . 2
4 Requirements . 3
4.1 Maximum of the vertical static force “S” . 3
4.2 Material and weldability of the drawbars . 3
4.3 Strength calculation . 3
Annex A (informative) Examples of configurations . 7
Bibliography .14
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 7641 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 4, Exterior
fittings of car/trailer-caravan combinations.
This first edition of ISO 7641 cancels and replaces ISO 7641-1:1983, which has been technically revised.
iv © ISO 2012 – All rights reserved
INTERNATIONAL STANDARD ISO 7641:2012(E)
Road vehicles — Trailers up to 3,5 t — Calculation of the
mechanical strength of steel drawbars
1 Scope
This International Standard gives a simplified procedure for the calculation of the mechanical strength
of steel drawbars, whether there are welds or not, for centre-axle trailers Categories O1 and O2 as
specified in the UNECE, Consolidated Resolution on the Construction of Vehicles (R.E.3). Consequently, it
only applies to simple constructions that enable a calculation in bending.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
UNECE, Consolidated Resolution on the Construction of Vehicles (R.E.3)
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
mechanical coupling device
mechanical coupling component
part fixed to the frame, to self-carrying parts of the bodywork and to the chassis of the tractor and the
trailers, used to couple the vehicles
NOTE 1 This includes parts used to attach the coupling device or the components to the vehicle or to actuate
the coupling device.
NOTE 2 Mechanical coupling devices transmit horizontal forces in the driving direction or the lateral direction.
Vertical supporting forces are also transmitted.
3.1.2
drawbar
separate technical unit attached to the frame of the trailer with or without inertia control devices and
comparable equipment parts at the front of the towed vehicles or at the vehicle chassis, adapted to couple
with the tractor with help of drawbar eyes, coupling heads of similar devices
NOTE 1 They are fixed in the vertical direction; they are able to receive vertical forces (rigid drawbars). Rigid
drawbars can be fixed completely rigid or by means of a suspension. Drawbars can be composed of more than one
component. They can be adjustable in height.
NOTE 2 Examples of configurations are shown in Annex A.
3.1.3
chassis part
part of the frame and the bodywork of the trailer, that participate in connecting the bodywork and its
load to the axle
3.1.4
simple drawbar
drawbar (3.1.2) composed of either
— two straight arms with open or closed profile with constant or decreasing cross section, or
— a single profile made of a closed constant or decreasing cross section, in which case it can be
composed of more than one component, adjustable in height
NOTE 1 Fundamentally there can be mounted inertia control devices or the coupling head/drawbar-eye to
the drawbars.
NOTE 2 In the case of simple drawbars, the mechanical resistance can be calculated with sufficient security, so
that a dynamic resistance test of the whole construction can be avoided.
3.1.5
centre-axle trailer
trailer having a drawbar (3.1.2) which cannot move in a vertical plane independent of the trailer and
having an axle or axles positioned close to the centre of gravity of the trailer, when uniformly loaded
NOTE The vertical force imposed on the coupling of the towing vehicle cannot exceed 10 per cent of the
maximum mass of the trailer, or 1 000 kg, whichever is the lesser.
3.2 Symbols
e distance, in metres, from the horizontal axis of the coupling device (coupling ball
centre) to the drawbar neutral fibre at the first fixing point to the trailer frame (see
Figure 1)
e distance, in metres, from the horizontal axis of the coupling device (coupling ball
x
centre) to the drawbar neutral fibre at the cross section corresponding to the
maximum strain rate (see Figure 1)
l distance, in metres, from the vertical axis of the c
...
ISO 7641:2012は、鋼製ドローバーの機械的強度を計算するための簡略化された手順を提供する標準です。この標準は、UNECEの「車両の構造に関する統合決議（R.E.3）」で指定されたセンターアクスルトレーラーのカテゴリO1およびO2に適用されます。対象とする範囲は、溶接の有無にかかわらず、シンプルな構造で曲げの計算を可能にするものに限定されています。このため、ISO 7641:2012は、設計者やエンジニアにとって重要なリソースとなっており、標準化されたアプローチを提供することで、トレーラーの安全性と信頼性を確保する助けとなります。 この標準の強みには、簡易性がありながらも必要な計算を正確に行うための手法を示している点があります。特に、シンプルな構造のトレーラーに対する計算を効率よく実施できるため、製造業者が迅速に適合性を評価できるようになります。さらに、ISO 7641:2012は、国際的に認められた標準であるため、異なる地域や市場での相互運用性を高める上でも意義深い存在です。 このドキュメントは、鋼製ドローバーの設計に関連する技術者や製造業者にとって不可欠なガイドラインとなっており、トレーラーのメカニカルストレングスに関する計算手法を標準化することで、業界全体の品質を向上させる役割を果たしています。ISO 7641:2012は、実務における関連性が高く、効率的な設計プロセスを促進する重要な基準です。
La norme ISO 7641:2012 fournit une procédure simplifiée pour le calcul de la résistance mécanique des timons en acier pour les remorques à essieu central des catégories O1 et O2, selon la résolution consolidée de l'UNECE concernant la construction des véhicules (R.E.3). Cette norme revêt une grande importance dans le domaine des véhicules routiers, car elle est axée spécifiquement sur les remorques pesant jusqu'à 3,5 tonnes, garantissant ainsi une application ciblée aux constructions simples susceptibles de permettre un calcul en flexion. Un des principaux atouts de la norme ISO 7641:2012 est sa capacité à traiter les constructions avec ou sans soudures, offrant ainsi une flexibilité qui est essentielle pour les fabricants et les ingénieurs qui conçoivent des remorques. La méthodologie simplifiée qui est proposée dans cette norme permet une meilleure compréhension et facilité d'application, ce qui est crucial pour assurer la conformité et la sécurité des remorques sur la route. En termes de pertinence, ISO 7641:2012 répond aux exigences actuelles en matière de sécurité et de performance des remorques en fournissant des directives claires pour le calcul de la résistance des timons. Cela contribue non seulement à la durabilité des remorques, mais également à la protection des usagers de la route. La norme s'intègre donc parfaitement dans le cadre des normes internationales visant à améliorer la sécurité des véhicules routiers tout en soutenant l'innovation dans le secteur. En somme, ISO 7641:2012 se distingue par son approche pragmatique et spécialisée, ce qui en fait un outil précieux pour les professionnels de l'industrie des remorques.
Die Norm ISO 7641:2012 behandelt die mechanische Festigkeit von Stahl-Zugdeichseln bei Straßenfahrzeugen, insbesondere für Anhänger mit einem Gewicht von bis zu 3,5 t, Kategorien O1 und O2. Die Norm bietet ein vereinfachtes Verfahren zur Berechnung der mechanischen Festigkeit dieser Zugdeichseln, unabhängig davon, ob Schweißnähte vorhanden sind oder nicht. Ein wesentlicher Stärke der ISO 7641:2012 liegt in ihrer klaren Fokussierung auf einfache Konstruktionen, die eine Biegeberechnung ermöglichen. Dies fördert die Benutzerfreundlichkeit und die Anwendbarkeit der Norm für Hersteller von Anhängern und Ingenieure, die sich mit der Konstruktion solcher Fahrzeuge beschäftigen. Durch die Vorgabe eines vereinfachten Berechnungsverfahrens wird der Prozess der Analyse der mechanischen Festigkeit effizienter und zugänglicher gestaltet, was potenziellen Zeit- und Kostenaufwand reduziert. Die Relevanz der Norm ist unbestreitbar, da sie den Anforderungen der UNECE, der Konsolidierten Resolution über die Konstruktion von Fahrzeugen (R.E.3), gerecht wird und somit eine internationale Grundlage für die Herstellung sicherer und zuverlässiger Anhänger schafft. Durch die Anwendung dieser Norm können Hersteller sicherstellen, dass ihre Produkte die notwendigen Sicherheitsstandards erfüllen und gleichzeitig die technischen Anforderungen berücksichtigen. Insgesamt trägt die ISO 7641:2012 dazu bei, die Konstruktion und Sicherheit von Straßenfahrzeugen zu optimieren, was sie zu einer unverzichtbaren Ressource für die Automobilindustrie macht.
ISO 7641:2012 표준은 도로 차량용 트레일러(3.5t 이하)의 강도 계산을 위한 간소화된 절차를 제공합니다. 이 표준은 UNECE의 차량 건설에 관한 통합 결의(R.E.3)에서 제시한 O1 및 O2 카테고리 중심 축 트레일러의 강도 계산에 적합하며, 용접 유무에 관계없이 강철 드로바의 기계적 강도를 평가하는 데 집중합니다. ISO 7641:2012의 주요 강점은 복잡한 계산 없이도 사용자가 쉽게 이해하고 적용할 수 있는 접근 방식을 제공한다는 점입니다. 이는 설계 엔지니어 및 차량 제조업체에게 유용한 도구가 됩니다. 특히 교통 상황이나 운영 환경이 다양한 조건에서 강도를 간단하게 계산할 수 있도록 도와줍니다. 또한, 이 표준은 단순한 구조물을 대상으로 하여 휘어짐 계산을 가능하게 함으로써 사용의 직관성을 증가시키며, 강철 드로바의 기계적 강도 평가에 필요한 기초 데이터를 제공합니다. 따라서 표준은 트레일러 설계와 관련하여 중요한 지침을 제공하며, 모든 이해관계자에게 신뢰할 수 있는 방법론을 제시합니다. ISO 7641:2012는 현재 도로 차량 산업에서의 강도 평가의 필수 표준으로 자리 잡고 있으며, 엔지니어링 분야에 큰 영향을 미치고 있습니다. 이 표준은 간단하면서도 효율적으로 활용될 수 있는 시스템을 마련하여, 사용자가 기능적이고 안전한 트레일러를 설계할 수 있도록 지원합니다.
ISO 7641:2012 serves a critical function in the realm of road vehicle safety, specifically focusing on the mechanical strength of steel drawbars in trailers up to 3.5 t. The standard provides a streamlined approach for calculating this strength, taking into account the presence or absence of welds. This is particularly relevant for center-axle trailers categorized under O1 and O2, as outlined in the UNECE’s Consolidated Resolution on the Construction of Vehicles (R.E.3). One of the significant strengths of ISO 7641:2012 is its emphasis on simplified procedures, allowing manufacturers and engineers to assess the structural integrity of drawbars in a more accessible manner. By concentrating on simple constructions that facilitate bending calculations, the standard ensures that users can apply the guidelines efficiently without sacrificing accuracy. This balance between simplicity and reliability makes ISO 7641:2012 a vital tool in the vehicle manufacturing process, ultimately contributing to enhanced safety on the roads. Moreover, the standard's relevance cannot be overstated, as it directly addresses the mechanical strength requirements for steel drawbars, an essential component in trailer design. By establishing clear parameters for evaluation, ISO 7641:2012 aids in the development of safer vehicles that meet industry regulations and performance benchmarks. Thus, it stands out as an indispensable reference for professionals in the automotive sector, ensuring that trailer safety and reliability remain paramount considerations in engineering design practices.
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