BRITISH STANDARD AUTOMOBILE SERIES BS AU 210 1 1987 Drawbars for caravans and light trailers — Part 1 Method for calculation of the mechanical strength of steel drawbars UDC [629 11 – 43 + 728 76] 629[.]
Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 57: 54 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BRITISH STANDARD AUTOMOBILE SERIES Drawbars for caravans and light trailers — Part : Method for calculation of the mechanical strength of steel drawbars UDC [629.11 – 43 + 728.76] :629.11.013.1 BS AU 21 0-1 :1 987 Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 57: 54 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 21 0-1 :1 987 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Automobile Standards Committee (AUE/- ) to Technical Committee AUE/8, upon which the following bodies were represented: Association of Trailer Manufacturers British Compressed Air Society Caravan Club Chief and Assistant Chief Fire Officers’ Association Consumer Standards Advisory Committee of BSI Department of Trade and Industry (Vehicle Division) Department of Transport (Highways) National Caravan Council Limited Society of Motor Manufacturers and Traders Limited This British Standard, having been prepared under the direction of the Automobile Standards Committee, was published under the authority of the Board of BSI and comes into effect on Amendments issued since publication 30 January 987 © BSI 02- 2000 The following BSI references relate to the work on this standard: Committee reference AUE/8 Draft for comment 82/78643 DC ISBN 80 660 Amd No Date of issue Comments Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 57: 54 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 21 0-1 :1 987 Contents Page Committees responsib le Foreword ii Scope Field of application References Symbols and definitions Resistance calculation Figure — D rawbar sketch Figure — Permissible stress Pub lications referred to © BSI 02 - 000 Inside front cover Inside back cover i Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 57: 54 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 21 0-1 :1 987 Foreword This Part of BS AU 21 has been prepared under the direction of the Automobile Standards Committee and is based on ISO 7641 - : 983 “Road vehicles — Caravans and light trailers — Calculation of the mechanical strength of the drawbar — Part 1: Steel drawbars ”, published by the International Organization for Standardization (ISO) It differs from the International Standard in two respects Firstly, the ISO document refers to ISO/TR 41 in relation to the limits on the vertical static loads on the coupling head, whereas in this standard reference to ISO/TR 41 has been deleted and values of 245 N to 735 N have been substituted Secondly, ISO 7641 - refers to ISO 7641 - 2: this reference has been changed to BS AU 21 0- For ease of reproduction, the ISO text has been used Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following The comma has been used as a decimal marker In British Standards it is current practice to use a full point on the baseline as the decimal marker The Technical Committee has reviewed the provisions of ISO 1 76 and ISO 7237, to which reference is made in the text, and has decided that they are acceptable for use in conj unction with this standard A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages to 4, an inside back cover and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated This will be indicated in the amendment table on the inside front cover ii © BSI 02- 2000 Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 57: 54 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 21 0-1 :1 987 Scope This Part of BS AU 210 gives a simplified procedure for the calculation of the mechanical strength of drawbars for caravans and light trailers1) where the vertical static force on the coupling head is not less than 245 N or greater than 735 N Field of application Calculations shown in this Part of BS AU 210 apply only to steel drawbars, of welded and other than welded construction For welded drawbars, only those types of steel which contain not more than 0,22 % carbon and the weldability of which is guaranteed by the manufacturer shall be used The welding procedure requirements given by the manufacturer shall be met (preheating, for example) NOTE Drawbars made from other materials will be dealt with in BS AU 210-2 2) References The titles of the publications referred to in this Part of BS AU 210 are listed on the inside back cover Symbols and definitions Figure — Drawbar sketch is the distance, in metres, from the vertical axis of the coupling device to the first fixing point on the trailer frame; lx is the distance, in metres, from the vertical axis of the coupling device to the drawbar section corresponding to the maximum strain rate; e is the distance, in metres, from the horizontal axis of the coupling device to the drawbar neutral fibre at the first fixing point on the trailer frame; ex is the distance, in metres, from the horizontal axis of the coupling device to the drawbar neutral fibre at the cross section corresponding to the maximum strain rate; P is the maximum manufacturer’s total mass, in kilogrammes (see ISO 7237); D is the value, in newtons, determined by calculation for the longitudinal forces occurring between tractor vehicle and trailer: 22 000 × P D = g × 22 000 + P k is the coefficient for a drawbar longer than 2,5 m to be determined as follows: k = 1,25 – 0,1 l with kmin = 0,6 l 1) Categories 01 and 02 as in ECE/UNO classification 2) At stage of draft © BSI 02-2000 Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 57: 54 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU -1 : 987 Resistance calculation l of the drawbar taking into account distances l the maximum bending moment occurs when l = l and e = e The calculation shall be carried out over the whole length and e x x in order to determine maximum strain rate The strain rate shall be checked at the position where x x C alculation of the maximum b ending moment, expre sse d in ne wton me tres, for the drawb ar with e/l < 0, and e /l x x < 0, Only flexure is taken into account for the calculation D rawb ars of length ,5 m or less: — for braked trailers: M = 0, 36 P g l f x — for unbraked trailers: M = 0, 24 P g l f x D rawb ars of length greater than ,5 m: — for braked trailers: M = 0, 36 P g k l f x — for unbraked trailers: M = 0, 24 P g k l f x C alculation of the maximum b ending mome nt, e xpre ssed in newton metre s, for drawb ars with e/l > 0, and e /l x x > 0, Only flexure is taken into account for the calculation Three bending moments, M, M f fD and M fR shall be calculated; the largest value of the three shall be used M for the calculation of the maximum admissible stress ( fmax) D rawb ars of le ngth ,5 m or le ss: — for braked trailers: M = 0, 36 P g l M = 0, D e M = 0, 75 (M + M f fD fR x x fD ) f — for unbraked trailers: M = 0, 24 P g l M = 1,0 D e M = 0, 75 (M + M f fD fR x x fD ) f D rawb ars of le ngth gre ate r than ,5 m: — for braked trailers: M = 0, 36 P g k l M = 0, D e M = 0, 75 (M + M f fD fR x x fD ) f — for unbraked trailers: M = 0, 24 P g k l M = 1,0 D e M = 0, 75 (M + M f fD fR x x f fD ) © BSI 02- 2000 Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 57: 54 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 21 0-1 :1 987 Permissible stress S tres s rates Ö Ö calculated for the whole length of the drawb ar s hall not exceed the allowed stres s Ö c : M I V f = where I V is the section modulus of drawb ar - cros s - s ection corresp onding to the maximum b ending moment 5.3.1 Drawbars fabricated by means other than welding: 0, Ö B WÖ u c 0, Ö s where Ö Ö Ö c is the p ermis sib le stres s , in newtons p er s quare millimetre; is the ultimate tens ile stres s, in newtons p er square millimetre; B s is the yield stress , in newtons p er s quare millimetre 3.2 Welded drawbars: , 45 Ö B WÖ u c , 65 Ö s Figure — Permissible stress © BS I - 00 Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 57: 54 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI blank Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 57: 54 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 21 0-1 :1 987 Publications referred to BS AU 0, Draw b ars , BS AU 0- , than steel 3) ISO 1 76, Ro ad vehicles — Weights — Vocab ulary ISO /TR 41 4, ISO 72 37, 3) 4) carav ans and light trailers Metho d fo r calculation of the m echanical s trength o f draw b ars m ade from m aterials other Road v ehicles — Carav ans and light trailers — Static load o n b all coup lings Ro ad vehicles — Mass es and dim ensio ns of carav ans — Term s and definitions At stage of draft Referred to in the foreword only © BSI 02 - 000 4) Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 57: 54 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 21 0-1 :1 987 BSI — British Standards Institution BS I is the indep endent national b ody res p ons ib le for p rep aring Britis h S tandards It p res ents the UK view on s tandards in E urop e and at the international level It is incorp orated b y Royal C harter Revisions Britis h S tandards are up dated b y amendment or revis ion Us ers of Britis h S tandards should make s ure that they p oss es s the latest amendments or editions It is the constant aim of BS I to imp rove the quality of our p roducts and services We would b e grateful if anyone finding an inaccuracy or amb iguity while us ing this Britis h S tandard would inform the S ecretary of the technical committee res p ons ib le, the identity of which can b e found on the inside front cover Tel: 02 89 96 90 00 Fax: 02 89 96 40 BS I offers memb ers an individual up dating s ervice called PLUS which ens ures that s ub s crib ers automatically receive the lates t editions of s tandards Buying standards O rders for all BS I, international and foreign s tandards p ub lications s hould b e addres s ed to C us tomer S ervices Tel: 899 00 Fax: 899 7001 In res p ons e to orders for international standards , it is BS I p olicy to sup p ly the BS I imp lementation of thos e that have b een p ub lis hed as Britis h S tandards, unless otherwis e requested Information on standards BS I p rovides a wide range of information on national, E urop ean and international standards through its Lib rary and its Technical H elp to E xp orters S ervice Various BS I electronic information s ervices are also availab le which give details on all its p roducts and s ervices C ontact the Information C entre Tel: 02 89 96 71 1 Fax: 02 89 96 048 S ub s crib ing memb ers of BS I are kep t up to date with s tandards develop ments and receive sub s tantial discounts on the p urchase p rice of s tandards For details of thes e and other b enefits contact Memb ership Adminis tration Tel: 02 89 96 70 02 Fax: 02 89 96 00 Copyright C op yright s ub s is ts in all BS I p ub lications BS I als o holds the cop yright, in the UK, of the p ub lications of the international s tandardization b odies E xcep t as p ermitted under the C op yright, D es igns and Patents Act 988 no extract may b e rep roduced, s tored in a retrieval s ystem or transmitted in any form or b y any means – electronic, p hotocop ying, recording or otherwis e – without p rior written p ermis s ion from BS I This does not p reclude the free us e, in the cours e of imp lementing the standard, of necess ary details such as s ymb ols, and size, typ e or grade designations If thes e details are to b e used for any other p urp os e than imp lementation then the p rior written p ermiss ion of BS I must b e ob tained If p ermis sion is granted, the terms may include royalty p ayments or a licensing agreement D etails and advice can b e ob tained from the C op yright Manager BS I 89 C his wick H igh Road London W4 4AL Tel: 02 89 96 70