BS-6102-16-1997.pdf
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 6102 : Part 16 : 1997 ICS 43.150 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Cycles Part 16. Specification for replacement brake-blocks Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 12:17:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6102 : Part 16 : 1997 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 October 1997 BSI 1997 The following BSI references relate to the work on this standard: Committee reference GME/25 Draft for comment 96/709018 DC ISBN 0 580 28612 6 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 GME/25, Cycles, upon which the following bodies were represented: Association of Consulting Scientists Association of Cycle Traders Bicycle Association of Great Britain British Cycling Federation British Retail Consortium British Rubber Manufacturers' Association Ltd. Consumer Policy Committee of BSI Cyclists' Touring Club Department of Transport Institute of Trading Standards Administration Royal Society for the Prevention of Accidents Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 12:17:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6102 : Part 16 : 1997 BSI 1997i Contents Page Committees responsibleInside front cover Forewordii Specification Introduction1 1Scope1 2References1 3Definitions1 4Instructions to be supplied with brake-blocks2 5Marking2 6Performance tests2 Annexes A(informative) Method of determining the radius of gyration of the flywheel6 B(informative) Method of calculating kinetic energy for the machine test6 Table 1Forces to be applied between each brake-block and the rim5 Figures 1Typical arrangement of a road-wheel connected to a flywheel by a mechanical drive3 2Arrangement of water nozzles4 A.1 Bifilar pendulum method of determining the radius of gyration6 A.2 Trifilar pendulum method of determining the radius of gyration6 List of referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 12:17:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii BSI 1997 BS 6102 : Part 16 : 1997 Foreword This Part of BS 6102 has been prepared by Technical Committee GME/25, and forms part of a series of documents which relate to pedal-cycles. Whilst for many years there have been stringent requirements specified in BS 6102 : Part 1 for complete bicycles to be tested to ensure satisfactory stopping distances under both dry and wet conditions, there have been no requirements for replacement brake-blocks to meet similar performance standards. This specification is intended to overcome the previous deficiency with simple, rapid and realistic laboratory tests although road-tests on complete bicycles are also permitted. Instructions and identification markings for brake-blocks are also included. Tests for durability or fade characteristics have not been specified. Attention is drawn to the following statutory regulations relevant to bicycles: The Electrically Assisted Pedal Cycles Regulations 1983 (SI No. 1168) 1; The Pedal Cycles (Construction and Use) Regulations 1983 (SI No. 1176) 2; The Pedal Cycles (Safety) Regulations 1984 (SI No. 1057) 3; The Road Vehicle Lighting Regulations 1989 (SI No. 2280) 4. 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 to 8, an inside back cover and a back cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 12:17:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 19971 BS 6102 : Part 16 : 1997 Specification Introduction The aim of this Part of BS 6102 is to ensure that replacement brake-blocks which operate on the rims of bicycles have satisfactory frictional characteristics and will, when fitted to a bicycle, give stopping distances not greater than those specified for complete bicycles in ISO 4210. Tests may be conducted on bicycles in accordance with 2.2.5 of ISO 4210 but, in order to expedite results and to minimize test costs, a type of test machine has been specified in broad terms. The machine incorporates an easily changeable road-wheel so that appropriate types of rim can be employed. Also, the test arrangements provide for tests to be conducted realistically under wet or dry conditions by bringing to rest the wheel which is coupled to a source of rotational kinetic energy. Instructions to be supplied with brake-blocks and markings for brake-blocks are also specified. 1 Scope This Part of BS 6102 specifies performance requirements for replacement brake-blocks intended for use only on the rims of bicycles intended for use on public roads, and on which the saddle can be adjusted to provide a saddle height of 635 mm or more. It does not apply to brakes intended for specialized types of bicycle such as tradesmen's delivery bicycles, tandems, toy bicycles and bicycles designed and equipped for use in sanctioned competitive events. 2 References 2.1 Normative references This Part of BS 6102 incorporates, by dated or undated reference, provisions from other publications. These normative references are made at the appropriate places in the text and the cited publications are listed on the inside back cover. For dated references, only the edition cited applies: any subsequent amendments to or revisions of the cited publication apply to this Part of BS 6102 only when incorporated in the reference by amendment or revision. For undated references, the latest edition of the cited publication applies, together with any amendments. 2.2 Informative references This Part of BS 6102 refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions. 3 Definitions For the purposes of this Part of BS 6102 the definitions given in BS 6102 : Part 1 apply, together with the following. 3.1 brake-block Block of frictional material which contacts and rubs on the rim during braking. 3.2 brake-block holder Shoe which contains the brake-block and provides a means of attachment to the brake-arm. 3.3 integral brake-block/holder Unit in which the brake-block and holder are combined. 3.4 braking distance Distance travelled in bringing a bicycle to rest from the moment of application of the brakes in a road test. 3.5 equivalent linear braking distance Linear distance travelled by the surface of the flywheel in the tests specified in clause 6. 3.6 brake-block application force Force acting between the brake-block and the rim of the road-wheel. 3.7 rim Outer, circular part of the wheel which carries the tyre and upon which the brake-blocks act. 3.8 test operation Single braking test including deceleration from the test speed and recording of the braking distance. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 12:17:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 2 BSI 1997 BS 6102 : Part 16 : 1997 1) Marking BS 6102 : Part 16 : 1997 on or in relation to a product represents a manufacturer's declaration of conformity, i.e. a claim by or on behalf of the manufacturer that the product meets the requirements of the standard. The accuracy of the claim is solely the claimant's responsibility. Such a declaration is not to be confused with third party certification, which may also be desirable. 2) A European Standard is in preparation which covers surface finishes and which will supersede BS 1224 : 1970. 4 Instructions to be supplied with brake-blocks Each pack of brake-blocks, assemblies of brake-blocks and holders, or integral brake-blocks/holders shall be provided with instructions containing information on: a) the recommended type of rim and, in particular, the rim material; b) the method of fitting the blocks or holders; c) the method of cleaning; d) a recommendation that reference should be made to the cycle manufacturer's handbook for the recommended type of brake-block and for maintenance of brakes; e) a declaration that the blocks conform to BS 6102 : Part 161); f) the name of the UK manufacturer, UK distributor, or the UK retailer; g) an advisory note to the user: Wet weather impairs traction for both the cyclist and other vehicles sharing the road. The risk of accident increases in wet conditions. Riding with worn brake-blocks is dangerous. Check brake-blocks regularly.' 5 Marking Each brake-block, brake-block and holder assembly, or integral brake-block/holder shall be marked with the manufacturer's name and the type of rim for which the block is intended, e.g. STEEL', ALLOY', and such marking shall be visible when the brake-block is fitted to the bicycle. NOTE. It is considered that there is not sufficient space to mark the BS number on each block or holder. 6 Performance tests 6.1 Alternative methods of test Performance tests under both dry and wet conditions shall be carried out on either a bicycle, in accordance with 6.3, or a special test machine, in accordance with 6.4. NOTE. The test machine is the preferred method. 6.2 Brake-blocks and rims 6.2.1 General In whichever test method is used, both the profile and the material of the wheel rim shall be appropriate to the design and marking of the brake-blocks. 6.2.2 Steel rims When testing brake-blocks intended for use with steel rims, a chromium-plated, steel rim shall be used. This rim shall have a section and size similar to that for which the brake-block under test is designed to be used on and a surface finish conforming to clause 4 of BS 1224 : 19702). The rim shall be free from any significant discontinuity at the joint. After repeated use, the rim shall be replaced before the chromium surface is worn through at any point on the braking surface. 6.2.3 Aluminium-alloy rims When testing brake-blocks intended for use on aluminium-alloy rims, an anodized, aluminium-alloy rim shall be used. This rim shall have a section and size similar to that for which the brake-block under test is designed to be used on and a smooth surface finish. The rim shall be free from any significant discontinuity at the joint. After repeated use, the rim shall be replaced before the anodized layer is worn through at any point on the braking surface. 6.2.4 Rims with special profiles or of special materials If brake-blocks are intended for use on a rim with a special profile and/or made of a material other than steel or aluminium-alloy, a rim of that profile and material, in new condition, shall be used. 6.3 Test on a bicycle Brake-blocks shall fulfil the acceptance criteria in 2.2.5.1 and 2.2.5.2 of ISO 4210 : 1996. 6.4 Test on a machine 6.4.1 Brake-block performance When tested by the method described in 6.4.6 brake-blocks shall meet the acceptance criteria specified in 6.4.11. 6.4.2 Type of machine The machine shall be in accordance with figure 1. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 12:17:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 19973 BS 6102 : Part 16 : 1997 Cycle road-wheel Positive drive Flywheel Water nozzles Brake-block application mechanism Figure 1. Typical arrangement of a road-wheel connected to a flywheel by a mechanical drive 6.4.3 Equipment and instrumentation The machine shall be equipped with: a) a free-running, revolving, motor-driven flywheel connected to a cycle road-wheel and driving that wheel at a specified speed; b) an instrument capable of indicating the surface velocity of the road-wheel tyre to ± 2 %; c) a means of applying a controlled force to press the test brake-blocks against the rim of the road-wheel; d) an instrument for indicating the force which presses the brake-block against the rim; e) a system for disconnecting the drive from the flywheel or the power from the motor at the moment the braking force is applied; f) an instrument capable of measuring the braking distance to within ± 1 %; g) a water spray system to provide wetting of the braking surface of the road-wheel rim, consisting of a water reservoir connected by tubing to a pair of nozzles positioned in advance of the brake-blocks as shown in figure 2. Each nozzle shall provide a flow of water of not less than 4 ml/s. Distilled water at ambient temperature shall be used. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 12:17:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 4 BSI 1997 BS 6102 : Part 16 : 1997 50 mm Water nozzle Tee-piece Tee-piece Water nozzle Water nozzle Brake block Road-wheel rim Brake-block load applicator Direction of wheel rotation Figure 2. Arrangement of water nozzles Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 12:17:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 19975 BS 6102 : Part 16 : 1997 6.4.4 Accuracy requirements The accuracies of the various test parameters shall be as follows. a) The speeds of the cycle-wheel shall be within ± 2 % of the equivalent road-speeds. b) The inertia of the flywheel including any part of the motor-driven system remaining connected to the flywheel during braking shall be accurate to within ± 2 % of its nominal value. NOTE. See annex A for a method of measuring the radius of gyration of the flywheel. c) The radial run-out (concentricity) and the lateral run-out (squareness) of the test cycle-wheel shall conform to the tolerances specified in 2.6 of ISO 4210 : 1996. d) The braking distance shall be measured to an accuracy within ± 1 % of its nominal value. 6.4.5 Brake-block/rim clearance Each brake-block shall be adjusted so that with no force applied, it clears the revolving rim of the road-wheel by not less than 1 mm and not more than 2 mm. 6.4.6 Method of test 6.4.6.1 Dry conditions Accelerate the road-wheel by means of the flywheel until it attains a surface velocity equal to the magnitude of the velocity specified in 2.2.5.1 of ISO 4210 : 1996. Then disconnect the drive to the flywheel or the power to the motor (see 6.4.3e) but leave the road-wheel connected to the flywheel. Apply the force specified in 6.4.9 to the brake-blocks immediately, and bring the flywheel/road-wheel combination smoothly and progressively to rest. Record the equivalent linear braking distance. 6.4.6.2 Wet conditions Carry out the method specified in 6.4.6.1, except for accelerating the road-wheel by means of the flywheel until it attains a surface velocity equal to the magnitude of the velocity specified in 2.2.5.2 of ISO 4210 : 1996. At this point activate the water spray system (see 6.4.3g), commencing not less than 25 m and terminating no
