BS-AU-267-1998.pdf

| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD AUTOMOBILE SERIES BS AU 267:1998 ICS 43.040.70; 43.100 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Code of practice for Breakaway cables and secondary couplings Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:11:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI This British Standard, having been prepared under the direction of the Engineering Sector Board, was published under the authority of the Standards Board and comes into effect on 15 November 1998 BSI 1998 The following BSI references relate to the work on this standard: Committee reference AUE/8 Draft for comment 96/715576 DC ISBN 0 580 28203 1 BS AU 267:1998 Amendments issued since publication Amd. No.DateText affected Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee AUE/8, Undergear for caravans and trailers, upon which the following bodies were represented: Caravan Club Department of the Environment, Transport and the Regions National Caravan Council Limited National Trailer and Towing Association Ltd. Society of Motor Manufacturers and Traders Limited Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:11:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS AU 267:1998 BSI 1998i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Terms and definitions1 3Application1 4Design1 5Attachment1 6General2 7Trailer documentation2 Figure 1 ÐDirection of test load application2 Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:11:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii BSI 1998 BS AU 267:1998 Foreword This British Standard has been prepared by Technical Committee AUE/8. As a code of practice, this British Standard takes the form of guidance and recommendations. It should not be quoted as if it were a specification and particular care should be taken to ensure that claims of compliance are not misleading. EEC Directive 71/320/EEC, Braking requirements and EEC Regulation No. 13, requires the fitting of a breakaway cable or secondary coupling on all trailers up to a maximum gross weight of 3500 kg. It is now also a requirement of the Construction and Use Regulations that such a device is positively attached to a towing vehicle. A British Standard does not purport to include all 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 1 and 2, an inside back cover and a back cover. Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:11:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 19981 BS AU 267:1998 1 Scope This code of practice provides recommendations for breakaway cables and secondary couplings, and their attachment points, for light trailers or caravans up to a mass of 3 500 kg. It applies to trailers which do not have brakes or have overrun or inertia type braking systems only. 2 Terms and definitions 2.1 breakaway cable cable between the towing vehicle and the trailer including its fitments which, in the event of separation of the main coupling, activates the braking mechanism of the trailer 2.2 secondary coupling coupling device between the trailer and towing vehicle which, upon separation of the main coupling, ensures that the two vehicles remain connected, prevents the nose of the drawbar touching the ground and provides residual steering for the trailer 2.3 attachment point fitting (e.g. closed hole, loop or eyelet) provided for the attachment of a breakaway cable or secondary coupling to the towing vehicle 2.4 coupling device, usually made in two parts, which connects the trailer to the towing vehicle NOTEIt allows for movement, in all axes, of the two vehicles and withstands the applied static and dynamic loads during loading and operation. Typical examples are a coupling head and towball or towing eye and jaw. 3 Application Trailers with a mass of up to 3 500 kg should be fitted with either a breakaway cable or a secondary coupling. Trailers without brakes should have a maximum mass of 750 kg and should be fitted with a secondary coupling. It is recommended that trailers with brakes should be fitted with a breakaway cable. 4 Design 4.1 Breakaway cable The breakaway cable should be capable of applying a sufficient load to the braking system operating mechanism to hold the trailer on at least 18 % gradient at its maximum permissible trailer mass. Upon operation of the breakaway cable, the trailer should be brought to a halt without causing damage to the braking system components as a result of the application of too great an operating force. The breakaway cable should part after application of the trailer brakes either by reason of its ultimate strength or by means of a weak link inserted for this purpose. The cable should be provided with a device capable of permitting attachment to the attachment point and withstanding the applied loads without failure unless it provides the stress limit feature. The breakaway cable should have sufficient length to enable attachment to be made with the vehicle in any normal towing position without risk of inadvertent brake application or coming into contact with the ground. In order to ensure the compatibility of the breakaway cable with the braking system only the trailer manufacturer's original equipment cable or equivalent should be used. 4.2 Secondary couplings Secondary couplings used for the retention of trailers in the event of main coupling separation should be designed to have an ultimate tensile strength of equivalent to at least twice the maximum permissible mass of the trailer. 5 Attachment 5.1 General The breakaway cable or secondary coupling should be attached to the towbar in accordance with 5.2 or 5.3. NOTEThe preferred method is by direct attachment, see 5.2. 5.2 Direct attachment The sprung hook or clip on the end of the breakaway cable or secondary coupling should be attached directly to, or through, an attachment point on the towing vehicle. 5.3 Looped over attachment The breakaway cable or secondary coupling should be fixed by forming a loop with the hook or clip on the end of the cable which is fixed back on to the cable to form a loop. The loop should then be secured around the towing ball on the vehicle. 5.4 Removable towing devices When the towing device fitted to the towing vehicle is removable without the use of special tools, then the secondary coupling or breakaway cable should be attached directly to an attachment point, which should not be on, or part of, the detachable component(s). 5.5 Location Attachment points for the breakaway cable or secondary coupling should be positioned so that the normal articulation and braking action of the trailer is not impaired. Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:11:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 2 BSI 1998 BS AU 267:1998 Where possible, the breakaway cable or secondary coupling attachment point(s) should not be more than 100 mm from a vertical plane passing through the longitudinal centre line of the vehicle. If this is not possible, then it is essential that two attachment points are provided, equidistant from the vehicle centre line and no more than 250 mm from the vehicle centre line. The breakaway cable or secondary coupling attachment point(s) should be positioned as far rearward and as high as possible and practicable. 5.6 Physical characteristics When the breakaway cable or secondary coupling is attached directly to the towbar, the attachment loop, hole, eyelet or similar should be sufficiently large to allow a rigid sphere of at least 10 mm diameter to pass freely through it. 5.7 Strength The breakaway cable or secondary coupling attachment point should be able to withstand a static load of 2D for 10 s, applied along a line passing through the centre of the attachment point on a plane parallel to the longitudinal centre line of the vehicle and inclined downwards to the rear at 15° (see Figure 1), without detachment or incurring a distortion of deformation that could affect the safe operation of the breakaway cable or secondary coupling (where D is defined in EC Directive 94/20 and limited to a maximum trailer mass of 1500 kg). Figure 1 ± Direction of test load application 6 General 6.1 Breakaway cables The breakaway cable should pass through a lug, guide or similar fitting on the trailer, to ensure that, regardless of the relative angles of the trailer and towing vehicle at the time of separation of the main coupling, there is a direct, in line, pull applied to the brake linkage of the trailer. 6.2 Brake mechanism protection If necessary a skid, or other suitable means of protection should be provided to ensure that the brake operating mechanism does not foul the ground in the event of separation of the main coupling. 7 Trailer documentation Clear instructions and diagrams showing the attachment of the breakaway cable or secondary coupling should be included in the trailer handbook. The trailer handbook should also specify details of the rating and dimensions for spare breakaway cables and secondary couplings. The secondary coupling or breakaway cable attachment point(s) should be identified on the documentation supplied for the towbar installation and operation. The trailer documentation should indicate that direct attachment is the preferred method of attachment but if the cable is to be looped around the towing ball then it is essential that the user ensures that it is secure and will operate correctly. Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:11:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI blank Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:11:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BSI Ð British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions British Standards are updated by amendment or revision. Users of British Standards should make sure that they possess the latest amendments or editions. 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