1、raising standards worldwide NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI Standards Publication BS ISO 7641:2012 Road vehicles Trailers up to 3,5 t Calculation of the mechanical strength of steel drawbarsBS ISO 7641:2012 BRITISH STANDARD National foreword This British St
2、andard 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 It supersedes BS AU 210-1:1987, which is withdrawn.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 o
3、n request 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 wit
4、h a British 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 publication Date T e x t a f f e c t e dBS ISO 7641:2012 ISO 2012 Road vehicles Trai
5、lers up to 3,5 t Calculation of the mechanical strength of steel drawbars Vhicules routiers Remorques jusqu 3,5 t Calcul de la rsistance mcanique des timons en acier INTERNATIONAL STANDARD ISO 7641 First edition 2012-11-15 Reference number ISO 7641:2012(E)BS ISO 7641:2012ISO 7641:2012(E)ii ISO 2012
6、All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2012 All 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
7、ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandBS ISO 7641:2012ISO 7641:2012(E) ISO 2012 All rights reser
8、ved iii Contents Page Foreword iv 1 Scope . 1 2 Normative references 1 3 T erms, definitions and s ymbols 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 Anne
9、x A (informative) Ex amples of c onfigur ations 7 Bibliogr aph y .14BS ISO 7641:2012ISO 7641:2012(E) 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
10、 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 w
11、ork. 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 Int
12、ernational 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
13、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 fi
14、rst edition of ISO 7641 cancels and replaces ISO 7641-1:1983, which has been technically revised.iv ISO 2012 All rights reservedBS ISO 7641:2012INTERNATIONAL ST ANDARD ISO 7641:2012(E) Road vehicles Trailers up to 3,5 t Calculation of the mechanical strength of steel drawbars 1 Scope This Internatio
15、nal 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
16、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 referenc
17、es, the latest edition of the referenced document (including any amendments) applies. UNECE, Consolidated Resolution on the Construction of Vehicles (R.E.3) 3 T erms, d efinitions and s ymbols 3.1 T erms and definiti ons For the purposes of this document, the following terms and definitions apply. 3
18、.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
19、 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 con
20、trol 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 d
21、rawbars). 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, tha
22、t participate in connecting the bodywork and its load to the axle ISO 2012 All rights reserved 1BS ISO 7641:2012ISO 7641:2012(E) 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 o
23、f 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
24、 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
25、 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 S ymbols e distance, in metres, from the horizontal axis of th
26、e coupling device (coupling ball centre) to the drawbar neutral fibre at the first fixing point to the trailer frame (see Figure 1) e x distance, 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 m
27、aximum strain rate (see Figure 1) l x distance, in metres, from the vertical axis of the coupling device 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
28、(see Figure 1) P maximum manufacturers total mass of the trailer, in kg as defined by the trailer manufacturer, in consideration of technical elements such as materials strength, braking ability, etc. D lt value, in newtons, determined by calculation, corresponding to the longitudinal forces occurri
29、ng between towing vehicle and trailer: D lt = k coefficient for a drawbar with l 2,5 m to be determined as follows: k = 1,25 (0,1 x l) with k min= 0,6 S vertical static force applied to the coupling device An example of these symbols of distance can be illustrated as shown in Figure 1.2 ISO 2012 All
30、 rights reservedBS ISO 7641:2012ISO 7641:2012(E) Figure 1 Drawbar sketch Key 1 Neutral fibre 2 e 3 e x 4 l x 5 l 4 Requirements 4.1 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 sta
31、tic force “S” is superior to the limits set on the Figure 3, the validation of the drawbar should be carried out by means of dynamic tests. 4.2 Mat erial and w eldability of the dr a w bars For welded drawbars, only those grades of steel which contain not more than 0,25 % carbon and the weldability
32、of which is guaranteed by the steel manufacturer shall be used. The welding process requirements given by the manufacturer shall be followed (preheating, for example). 4.3 Strength calculation 4.3.1 Generalities The calculation shall be carried out over the whole length l of the drawbar taking into
33、account distances l xand e xin order to determine the maximum strain rate. The strain rate shall be checked at the position where the maximum bending moment occurs when l = l xand e = e x . 4.3.2 Calculation of the maximum bending moment for drawbars with e/l 0,15 and e x /l x 0,15 The calculation o
34、f the maximum bending moment for drawbars with e/l 0,15 and e x /l x 0,15, expressed in Newton metres, shall be as shown below. Only bending is considered for the calculation. a) Drawbars with l 2,5 m 1) for braked trailers: M f= 0,36 P g l x ISO 2012 All rights reserved 3BS ISO 7641:2012ISO 7641:20
35、12(E) 2) for non-braked trailers: M f= 0,24 P g l x b) Drawbars with l 2,5 m 1) for braked trailers: M f= 0,36 P g k l x 2) for non-braked trailers: M f= 0,24 P g k l x 4.3.3 Calculation of the maximum bending moment, expressed in Newton metres, for drawbars with e/l 0,15 and e x/ l x 0,15 The calcu
36、lation of the maximum bending moment for drawbars with e/l 0,15 and e x /l x 0,15, expressed in Newton metres, shall be as shown below. Only bending is considered for the calculation. Three bending moments, M f,M fDand M fRshall be calculated; the largest value of the three shall be used for the cal
37、culation of the maximum admissible stress (M fmax ). a) Drawbars with l 2,5 m 1) for braked trailers: M f= 0,36 Pgl xM fD= 0,8 De xM fP= 0,75 (M f+ M fD ) 2) for non-braked trailers: M f= 0,24 Pgl xM fD= 1,0 De xM fP= 0,75 (M f+ M fD ) b) Drawbars with l 2,5 m 1) for braked trailers: M f= 0,36 Pgkl
38、xM fD= 0,8 De xM fP= 0,75 (M f+ M fD ) 2) for non-braked trailers: M f= 0,24 Pgkl xM fD= 1,0 De xM fP= 0,75 (M f+ M fD ) 4 ISO 2012 All rights reservedBS ISO 7641:2012ISO 7641:2012(E) 4.3.4 Calculation of the permissible stress Stress rates calculated for the whole length of the drawbar shall not ex
39、ceed the allowed stress c : = where is the section modulus of drawbar cross-section corresponding to the maximum bending moment. a) Drawbars manufactured other than by welding: 0,6 Bmin c c 0,65 s4.3.5 Mechanical resistance of chassis parts It is the responsibility of the trailer manufacturer to des
40、ign 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)
41、The maximum of the vertical static force “S” with the trailer Gross Vehicle Weight (GVW) can be illustrated as shown in Figure 3. Key S static load (kg) GVW trailer Gross Vehicle Weight (kg) upper limit - lower limit Figure 3 Limits of the static force on the coupling as a function of trailer GVW fo
42、r calculation purpose6 ISO 2012 All rights reservedBS ISO 7641:2012ISO 7641:2012(E) Annex A (informative) Ex amples of c onfigur ations In 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 manufactur
43、ers responsibility. Key 1 coupling head 2 drawbar 3 chassis NOTE Drawbar is a separate technical unit. Devices for height adjustments can be provided. Figure A.1 Drawbar as a separate technical unit Key 1 drawbar eye 2 chassis NOTE Integral chassis-drawbar manufactured by bending, cutting in and wel
44、ding. Trailer manufacturers responsibility. Figure A.2 Integral chassis-drawbar ISO 2012 All rights reserved 7BS ISO 7641:2012ISO 7641:2012(E) Key 1 coupling head 2 chassis NOTE Drawbar is part of the frame; only the coupling head is a separate technical unit. Trailer manufacturers responsibility. F
45、igure A.3 Drawbar as part of the frame Key 1 coupling head 2 drawbar 3 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) Key 1 coupling h
46、ead 2 chassis NOTE Centre tube is part of the chassis. Trailer manufacturers responsibility. Figure A.5 Centre tube as part of the chassis Key 1 drawbar eye 2 drawbar 3 chassis NOTE V-shaped drawbar, bolted or welded to the ladder-frame (separate technical unit). Figure A.6 V-shaped drawbar bolted o
47、r welded to the ladder-frame ISO 2012 All rights reserved 9BS ISO 7641:2012ISO 7641:2012(E) Key 1 coupling head 2 drawbar 3 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
48、2 arms in V-position are a separate technical 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 7
49、641:2012ISO 7641:2012(E) Key 1 coupling head 2 drawbar 3 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) Key 1 coupling head 2 drawbar 3 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, f
