BRITISH STANDARD AUTOMOBILE SERIES BS AU 25 1964 Supersedes S M M T Standard No 51 Specification for Towing hook for use between trailers of 5–14 tons gross weight and towing vehicle UDC 629 11 013 5[.]
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 : 52: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BRITISH STANDARD AUTOMOBILE SERIES BS AU 25:1964 Sup ers edes S M M T Standard No Specification for Towing hook for use between trailers of 5–14 tons gross weight and towing vehicle UD C 62 1 : 62 1 81 51 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 : 52: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 25:1964 This Britis h S tandard, having b een ap p roved b y the Automob ile I ndus try S tandards C ommittee and endors ed b y the C hairman of the E ngineering D ivis ional C ouncil, was p ub lis hed under the authority of the General Amendments issued since publication C ouncil of the I ns titution on June 64 © BS I - 0 The following BS I reference relates to the work on this s tandard: C om mittee reference AUE /- ISBN 580 34548 Amd No D ate C omments 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 : 52: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 25:1964 Contents Page Foreword © BS I - 00 ii S cop e Materials D imens ions D es ign Mounting Marking Figure — Towing hook, indicating s afety catch Figure — Towing hook 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 : 52: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU : 964 Fore word This British Standard, which is published under the authority of the Automobile Industry Standards Committee of the BSI, is based upon data- sheet SMMT 51 : 957 of the Society of Motor Manufacturers and Traders Ltd The requirements of this standard, which relate only to vehicles used on the public highways, are intended to ensure the maximum degree of interchangeability between commercial and Government department and Services standards The material specifications are for the minimum qualities acceptable, and not exclude the use of other materials provided that these are at least equal in quality so that road safety is not impaired This standard should be used in conj unction with BS AU 29 1) The hook has been designed to accommodate a drawbar eye of in internal diameter and ; in stock, or in internal diameter and C in stock The standard applies to connections to trailers of – tons gross weight The specification for a towing hook for connections to trailers of – 35 tons gross weight is given in BS AU 27 BS AU 24 NOTE 3) 2) , and for trailers of – tons gross weight in If it is required to convert the figures in this standard from British units into metric units it Conversion factors and tables, be used Attention is drawn to BS 2856, Precise conversion of inch and metric sizes on engineering drawings is recommended that the conversion factors and tables contained in BS 350, 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 C omp liance with a British S tand ard d oe s no t of itse lf confe r immunity from le gal ob ligatio ns S ummary of p age s This document comprises a front cover, an inside front cover, pages i and ii, pages to 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 BS AU 29, “Drawbar eyes and forecarriage pins for connection between trailers of – 35 tons gross weight and towing vehicle” 2) BS AU 27, “ Towing hook for use between trailers of – 35 tons gross weight and towing vehicle ” 3) BS AU 24, “Towing connections for trailers of – tons gross weight ” 1) 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 : 52: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 25:1964 Scope Mounting This British Standard specifies the basic The hook shall be mounted with four bolts, C in dimensions and quality of materials for a towing diameter, at in hook and its mounting, for use in connections interchangeable in mounting with certain × in centres This renders it between a towing vehicle and a trailer of – tons Government department and Services standard gross weight hooks The gross weights refer to gross laden train weights Bolts and nuts shall comply with: where more than one trailer is drawn i) BS 083, Materials ii) BS 768, The hook shall be made from a material of quality not less than BS 970 En 5(N) or 4) threaded UNF, code symbol R5) The nuts shall be secured either by peening the end of the bolt or by fitting a positive locking device such as a safe locking nut or a slotted nut and split pin Dimensions Marking Dimensions shall be as shown in Figure and Figure NOTE threaded BSF, code symbol R, The following wording, in clear lettering B in high, raised or impressed, shall be marked on each towing The dimensions specified are based upon a forged hook, and have been calculated on the basis of the total yield strength hook: being equal to two thirds of the gross weight being towed It is “TO TOW TONS GROSS” on one side, and on necessary that any other parts not covered by this standard, the other side “BS AU 25” connecting the coupling to, the towing vehicle shall have a similar strength Design An efficient safety catch, preferably of the automatic or semi- automatic type, shall be provided as indicated in Figure to prevent accidental detachment of the drawbar from the hook The hook shall be so designed that a bar 23 32 in diameter, when held vertically, may be passed freely between the inside faces of the hook with the catch held back to clear (see Figure ) 4) 5) BS 083, “Precision BS 768, “Unified © BSI 02- 2000 hexagon bolts, screws and nuts” precision hexagon bolts, screws and nuts (UNC and UNF thread-normal series)” 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 : 52: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI All dimensions are in inches BS AU :1 964 Figure — Towing hook, indicating safe ty catch © BSI 02 - 000 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 : 52: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI All dimensions are in inches © BSI 02 - 000 Figure — Towing hook BS AU 25:1964 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 : 52: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 25:1964 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 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