1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 7641:2012Road vehicles Trailers up to 3,5 t Calculation of the mechanical strength of steel drawbarsBS ISO 7641:2012 BRITISH STANDARDNational forewordThis British Standard
2、 is the UK implementation of ISO 7641:2012. It supersedes BS AU 210-1:1987, which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee AUE/8, Undergear for caravans and light trailers.A list of organizations represented on this committee can be obtained on reques
3、t to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2012. Published by BSI Standards Limited 2012.ISBN 978 0 580 57878 6 ICS 43.040.70 Compliance with a Britis
4、h Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 December 2012.Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 7641:2012 ISO 2012Road vehicles Trailers up to 3,5
5、 t Calculation of the mechanical strength of steel drawbarsVhicules routiers Remorques jusqu 3,5 t Calcul de la rsistance mcanique des timons en acierINTERNATIONAL STANDARDISO7641First edition2012-11-15Reference numberISO 7641:2012(E)BS ISO 7641:2012ISO 7641:2012(E)ii ISO 2012 All rights reservedCOP
6、YRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below
7、 or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 7641:2012ISO 7641:2012(E) ISO 2012 All rights reserved iiiContents PageForeword iv
8、1 Scope . 12 Normative references 13 Terms, definitions and symbols 13.1 Terms and definitions . 13.2 Symbols . 24 Requirements 34.1 Maximum of the vertical static force “S” . 34.2 Material and weldability of the drawbars . 34.3 Strength calculation 3Annex A (informative) Examples of configurations
9、7Bibliography .14BS ISO 7641:2012ISO 7641:2012(E)ForewordISO (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 m
10、ember 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
11、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 ado
12、pted 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 pate
13、nt 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 7641-1:19
14、83, which has been technically revised.iv ISO 2012 All rights reservedBS ISO 7641:2012INTERNATIONAL STANDARD ISO 7641:2012(E)Road vehicles Trailers up to 3,5 t Calculation of the mechanical strength of steel drawbars1 ScopeThis International Standard gives a simplified procedure for the calculation
15、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 b
16、ending.2 Normative referencesThe 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
17、 amendments) applies.UNECE, Consolidated Resolution on the Construction of Vehicles (R.E.3)3 Terms, definitions and symbols3.1 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1.1mechanical coupling devicemechanical coupling componentpart fixed to t
18、he frame, to self-carrying parts of the bodywork and to the chassis of the tractor and the trailers, used to couple the vehiclesNOTE 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
19、 horizontal forces in the driving direction or the lateral direction. Vertical supporting forces are also transmitted.3.1.2drawbarseparate 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
20、at the vehicle chassis, adapted to couple with the tractor with help of drawbar eyes, coupling heads of similar devicesNOTE 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.
21、 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.3.1.3chassis partpart of the frame and the bodywork of the trailer, that participate in connecting the bodywork and its load to the axle ISO 2012 All rights r
22、eserved 1BS ISO 7641:2012ISO 7641:2012(E)3.1.4simple drawbardrawbar (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
23、than one component, adjustable in heightNOTE 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
24、 the whole construction can be avoided.3.1.5centre-axle trailertrailer 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 loadedNOTE The vertical force imposed
25、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 Symbolse 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
26、the trailer frame (see Figure 1)exdistance, in metres, from the horizontal axis of the coupling device (coupling ball centre) to the drawbar neutral fibre at the cross section corresponding to the maximum strain rate (see Figure 1)lxdistance, in metres, from the vertical axis of the coupling device
27、to the drawbar section corresponding to the maximum strain rate (see Figure 1)l distance, in metres, from the vertical axis of the coupling device to the first fixing point to the trailer frame (see Figure 1)P maximum manufacturers total mass of the trailer, in kg as defined by the trailer manufactu
28、rer, in consideration of technical elements such as materials strength, braking ability, etc.Dltvalue, in newtons, determined by calculation, corresponding to the longitudinal forces occurring between towing vehicle and trailer:Dlt=gPP+3200032000k coefficient for a drawbar with l 2,5 m to be determi
29、ned as follows:k = 1,25 (0,1 x l) with kmin= 0,6S vertical static force applied to the coupling deviceAn example of these symbols of distance can be illustrated as shown in Figure 1.2 ISO 2012 All rights reservedBS ISO 7641:2012ISO 7641:2012(E)Figure 1 Drawbar sketchKey1 Neutral fibre2 e3 ex4 lx5 l4
30、 Requirements4.1 Maximum of the vertical static force “S”The maximum vertical static force “S” on the coupling head shall not exceed the limits set on the Figure 3. If the vertical static force “S” is superior to the limits set on the Figure 3, the validation of the drawbar should be carried out by
31、means of dynamic tests.4.2 Material and weldability of the drawbarsFor welded drawbars, only those grades of steel which contain not more than 0,25 % carbon and the weldability of which is guaranteed by the steel manufacturer shall be used.The welding process requirements given by the manufacturer s
32、hall be followed (preheating, for example).4.3 Strength calculation4.3.1 GeneralitiesThe calculation shall be carried out over the whole length l of the drawbar taking into account distances lxand exin order to determine the maximum strain rate. The strain rate shall be checked at the position where
33、 the maximum bending moment occurs when l = lxand e = ex.4.3.2 Calculation of the maximum bending moment for drawbars with e/l 2,5 m1) for braked trailers: Mf= 0,36 P g k lx2) for non-braked trailers: Mf= 0,24 P g k lx4.3.3 Calculation of the maximum bending moment, expressed in Newton metres, for d
34、rawbars with e/l 0,15 and ex/ lx 0,15The calculation of the maximum bending moment for drawbars with e/l 0,15 and ex/lx 0,15, expressed in Newton metres, shall be as shown below. Only bending is considered for the calculation. Three bending moments, Mf,MfDand MfRshall be calculated; the largest valu
35、e of the three shall be used for the calculation of the maximum admissible stress (Mfmax).a) Drawbars with l 2,5 m1) for braked trailers:Mf= 0,36 PglxMfD= 0,8 DexMfP= 0,75 (Mf+ MfD) 2) for non-braked trailers:Mf= 0,24 PglxMfD= 1,0 DexMfP= 0,75 (Mf+ MfD) b) Drawbars with l 2,5 m1) for braked trailers
36、:Mf= 0,36 PgklxMfD= 0,8 DexMfP= 0,75 (Mf+ MfD) 2) for non-braked trailers:Mf= 0,24 PgklxMfD= 1,0 DexMfP= 0,75 (Mf+ MfD) 4 ISO 2012 All rights reservedBS ISO 7641:2012ISO 7641:2012(E)4.3.4 Calculation of the permissible stressStress rates calculated for the whole length of the drawbar shall not excee
37、d the allowed stress c: = MIVfwhereIVis the section modulus of drawbar cross-section corresponding to the maximum bending moment.a) Drawbars manufactured other than by welding:0,6 Bmin cc 0,65 s4.3.5 Mechanical resistance of chassis partsIt is the responsibility of the trailer manufacturer to design
38、 and build the chassis parts so that they can withstand the effects of all the forces transmitted by the drawbar when the trailer is in use.The permissible stress ccan be illustrated as shown in Figure 2.Figure 2 Permissible stress ISO 2012 All rights reserved 5BS ISO 7641:2012ISO 7641:2012(E)The ma
39、ximum of the vertical static force “S” with the trailer Gross Vehicle Weight (GVW) can be illustrated as shown in Figure 3.KeyS static load (kg)GVW trailer Gross Vehicle Weight (kg) upper limit - lower limitFigure 3 Limits of the static force on the coupling as a function of trailer GVW for calculat
40、ion purpose6 ISO 2012 All rights reservedBS ISO 7641:2012ISO 7641:2012(E)Annex A (informative) Examples of configurationsIn all the examples following in this annex, calculation is needed for the front section of the frames where there are no separate drawbars under trailer manufacturers responsibil
41、ity.Key1 coupling head2 drawbar3 chassis NOTE Drawbar is a separate technical unit. Devices for height adjustments can be provided.Figure A.1 Drawbar as a separate technical unitKey1 drawbar eye2 chassis NOTE Integral chassis-drawbar manufactured by bending, cutting in and welding. Trailer manufactu
42、rers responsibility.Figure A.2 Integral chassis-drawbar ISO 2012 All rights reserved 7BS ISO 7641:2012ISO 7641:2012(E)Key1 coupling head2 chassis NOTE Drawbar is part of the frame; only the coupling head is a separate technical unit. Trailer manufacturers responsibility.Figure A.3 Drawbar as part of
43、 the frameKey1 coupling head2 drawbar3 chassis NOTE Drawbar is a separate technical unit from the beginning to the end.Figure A.4 Drawbar as a separate technical unit from beginning to end8 ISO 2012 All rights reservedBS ISO 7641:2012ISO 7641:2012(E)Key1 coupling head2 chassis NOTE Centre tube is pa
44、rt of the chassis. Trailer manufacturers responsibility.Figure A.5 Centre tube as part of the chassisKey1 drawbar eye2 drawbar3 chassis NOTE V-shaped drawbar, bolted or welded to the ladder-frame (separate technical unit).Figure A.6 V-shaped drawbar bolted or welded to the ladder-frame ISO 2012 All
45、rights reserved 9BS ISO 7641:2012ISO 7641:2012(E)Key1 coupling head2 drawbar3 chassis NOTE 1 Drawbar with two arms in v-position, approximately in the direction of the pulling force of the trailer. The drawbar is part of the frame; the coupling head and 2 arms in V-position are a separate technical
46、unit. Trailer manufacturers responsibility.NOTE 2 In this example, calculation is needed for the front section of the frame under trailer manufacturers responsibility.Figure A.7 Drawbar with two arms in V-position10 ISO 2012 All rights reservedBS ISO 7641:2012ISO 7641:2012(E)Key1 coupling head2 draw
47、bar3 chassis NOTE Drawbar with two straight arms (separate technical unit).Figure A.8 Drawbar with two straight arms ISO 2012 All rights reserved 11BS ISO 7641:2012ISO 7641:2012(E)Key1 coupling head2 drawbar3 length l (distance, in metres, from the vertical axis of the coupling device to the first f
48、ixing point to the trailer frame)4 height e (distance, in metres, from the horizontal axis of the coupling device to the first fixing point to the trailer frame) NOTE Tube design drawbar (separate technical unit).Figure A.9 Tube design drawbar12 ISO 2012 All rights reservedBS ISO 7641:2012ISO 7641:2
49、012(E)Key1 drawbar eye2 drawbar3 length l (distance, in metres, from the vertical axis of the coupling device to the first fixing point to the trailer frame)4 height e (distance, in metres, from the horizontal axis of the coupling device to the first fixing point to the trailer frame)5 maximum angle NOTE Multi-components drawbar, adjustable in height (separate technical unit).Figure A.10 Multi-components drawbar adjustable in height ISO 2012 All rights reserve
