1、BRITISH STANDARDBS 7961:2004Specification for a device for measuring the static vertical mass (noseweight) at the coupling point of a towed vehicleICS 17.060; 43.040.70; 43.100g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g
2、3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58Confirmed December 2009BS 7961:2004This British Standard was published under the authority of the Standards Policy and Strategy Committee on 27 January 2004 BSI 27 January 2004The following BSI references relate to the work
3、on this British Standard:Committee reference AUE/8Draft for comment 00/704997 DC ISBN 0 580 43114 2Committees responsible for this British StandardThe preparation of this British Standard was entrusted to Technical Committee AUE/8, Undergear for caravans and light trailers, upon which the following
4、bodies were represented:Camping and Caravanning Club LimitedCaravan ClubConsumer Policy Committee of BSIDfT Central Transport GroupNational Caravan Council LimitedNational Trailer and Towing Association LimitedSociety of Motor Manufacturers and Traders LimitedTrailer and Towing Advisory ServiceAmend
5、ments issued since publicationAmd. No. Date CommentsBS 7961:2004 BSI 27 January 2004iContentsPageCommittees responsible Inside front coverForeword ii1Scope 12Terms and definitons 13 The noseweight gauge 14 Test for the determination of durability 45 Test for the determination of overload 46 Test for
6、 the determination of accuracy 5Bibliography 7Figure 1 Coupling 3BS 7961:2004ii BSI 27 January 2004ForewordThis British Standard has been prepared by AUE/8, Undergear for caravans and light trailers.This publication does not purport to include all the necessary provisions of a contract. Users are re
7、sponsible for its correct application.Compliance with a British Standard does not of itself confer immunity from legal obligations.Summary of pagesThis document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 7 and a back cover.The BSI copyright notice displayed in this do
8、cument indicates when the document was last issued.BS 7961:2004 BSI 27 January 200411 ScopeThis British Standard specifies requirements for devices intended to measure the static vertical mass of towed vehicles. Such devices are commonly known as “noseweight gauges”.This British Standard only applie
9、s to all towed vehicles up to 3 500 kg maximum technical permissible laden mass.NOTE Normally such towed vehicles are fitted with a 50 mm ball coupling device but the manufacturer of a noseweight gauge may also specify its suitability for use with other coupling devices.2 Terms and definitionsFor th
10、e purposes of this British Standard, the following terms and definitions apply.2.1 ball coupling systemmechanical coupling system designed to connect towing vehicles and towed vehicles by means of a coupling ball2.2 coupling headmechanical device on the drawbar or overrun device of towed vehicles fo
11、r connection to a coupling ball2.3 noseweightstatic vertical mass (“S” value in kg) exerted on the towing vehicle by the towed vehicle at the coupling pointNOTE Static vertical mass is commonly referred to as the S value in the UK and Europe. See Directive 94/20/EEC 1 and UNECE Regulation No. 55 2 f
12、or further information.2.4 towing vehiclemechanically propelled vehicle used for towing a towed vehicle2.5 towed vehiclevehicle without any means of self-propulsion to be towed by a towing vehicle (e.g. caravan, horse-box, etc.)3 The noseweight gauge 3.1 RangeThe noseweight gauge shall be capable of
13、 measuring from 20 kg to at least 100 kg.The noseweight gauge shall be capable of measuring in increments not greater than 5 kg and in the case of an analogue device the minimum scale separation for a 5 kg increment shall not be less than 5 mm. NOTE The scale and marked numerical values should be cl
14、ear and easy to read.BS 7961:20042 BSI 27 January 20043.2 PerformanceNOTE The same noseweight gauge should be used in performing each of the following three tests. If the noseweight gauge fails at any stage, then no further testing should be carried out.3.2.1 DurabilityWhen tested in accordance with
15、 Clause 4, the noseweight gauge shall be able to complete 1 000 test cycles and continue to meet the accuracy requirements of 3.2.3.3.2.2 Overload testingAfter being tested in accordance with Clause 4, the noseweight gauge shall be able to withstand twice the maximum load specified by the device man
16、ufacturer, for a period of 30 s, without permanent damage when tested in accordance with Clause 5. After removal of the load, the noseweight gauge shall show no deformation.3.2.3 AccuracyHaving undergone the tests described in Clause 4 and Clause 5, the noseweight gauge shall be accurate to within 5
17、 kg or 10 % of the specified mass, whichever is least.3.3 Operating height rangeThe operating height range of the noseweight gauge shall be as specified in the manufacturers user instructions.3.4 FinishAll surfaces of the noseweight gauge shall be smooth and free from any burrs or sharp edges that c
18、ould cause injury.3.5 MarkingsAll noseweight gauges shall be permanently and legibly marked with the following information:a) the weight range, kg to kg;b) the operating height range mm to mm to the centre of rotation of the coupling device in relation to the ground see Figure 1a) and Figure 1b);c)
19、the number and date of this British Standard, i.e. BS 7961:2004;d) the manufacturers name or trade mark;e) reference to the user instructions (see 3.6).3.6 User instructionsEach noseweight gauge shall be supplied with user instructions that shall contain at least the following information:a) detaile
20、d instructions for use;b) recommendations for safe operation of the device;c) recommendations for maintenance, storage and re-calibration.The instructions shall include the following statement:“When assessing/adjusting the noseweight of the towed vehicle, the limiting noseweights that individual com
21、ponents are able to sustain should be taken into account as well as those that the towed vehicle can sustain. The following components should all have limits of noseweight specified by the manufacturer, and any other limiting factors should also be considered in the assessment/adjustment of the nose
22、weight of the towed vehicle:a) towing vehicle;b) vehicle mounted towing device (tow bar);c) towed vehicle mounted towing device (coupling assembly);d) towed vehicle drawbar assembly;e) towed vehicle.”BS 7961:2004 BSI 27 January 20043Key1 is the vehicle2 is the center of rotation3 is the range of ope
23、rating height from the centre of rotation to the grounda) Coupling ballKey1 is the vehicle2 is the center of rotation3 is the towed vehicle drawbar4 is the range of operating height from the centre of rotation to the groundb) Coupling jaw and eyeFigure 1 Coupling1231324BS 7961:20044 BSI 27 January 2
24、0044 Test for the determination of durability4.1 PrincipleThe noseweight is operated in cycles from an S value of zero to the maximum specified for the noseweight gauge under test and back again to an S value of zero. The gauges ability to successfully complete a given number of test cycles is taken
25、 as a measure of its durability.4.2 Apparatus4.2.1 test rig, with a suitable means of force application so that it is not subjected to any additional forces or moments apart from an S value commensurate with the maximum specified for the noseweight gauge under test.4.2.2 noseweight gauge.4.3 Initial
26、 inspection of the noseweight gaugePrior to the start of the test check the noseweight gauge for any deformation.4.4 ProcedureSet up the test rig to apply the specified test forces to the noseweight gauge. Perform the load/unload cycle from an S value of zero to the maximum specified for the nosewei
27、ght gauge under test and back again to an S value of zero. Repeat the load/unload cycle at a frequency of not greater than 1 Hz until a minimum of 1 000 cycles have been completed.4.5 Final inspection of the noseweight gaugeCheck the noseweight for any deformation. If there is no obvious deformation
28、, undertake the overload test described in Clause 5.4.6 Expression of resultsRecord the number of test cycles completed without failure. If 1 000 or more test cycles have been successfully completed, record a “PASS”. If less than 1 000 test cycles have been completed, record a“FAIL”.4.7 Test reportT
29、he test report shall include the following:a) reference to this British standard, i.e. BS 7961:2004;b) the test result recorded in accordance with 4.6;c) the date of the test;d) where the test took place.5 Test for the determination of overload5.1 PrincipleFollowing testing in accordance with Clause
30、 4, the noseweight gauge is loaded to twice the maximum specified S value for the noseweight under test for a measured time and inspected for signs of deformation and damage. The gauges ability to successfully complete a given number of test cycles without deformation is taken as a measure of its du
31、rability.BS 7961:2004 BSI 27 January 200455.2 Apparatus5.2.1 test rig, with a suitable means of force application so that it is not subjected to any additional forces or moments apart from an S value commensurate with the maximum specified for the noseweight gauge under test.5.2.2 noseweight gauge.5
32、.3 Initial inspection of the noseweight gaugePrior to the start of the test, check the noseweight gauge for any deformation. If there is any deformation, do not proceed with the test.5.4 ProcedureSet up the test rig to apply the test force to the noseweight gauge. Maintain twice the maximum specifie
33、d S value for the noseweight under test for a period of 30 s and then release. 5.5 Final inspection of the noseweight gaugeCheck the noseweight for any deformation. If there is no obvious deformation, undertake the accuracy test described in Clause 6.5.6 Expression of resultsRecord any visible chang
34、es shown between the initial and final inspections of the noseweight gauge. If there is no obvious deformation, record a “PASS”. If there is obvious deformation, record a “FAIL”.5.7 Test reportThe test report shall include:a) reference to this British Standard, i.e. BS 7961:2004;b) the result of the
35、 test in accordance with 5.6;c) the date of the test;d) where the test took place.6 Test for the determination of accuracy6.1 PrincipleAfter the noseweight gauge has been successfully tested in accordance with the tests described in Clause 4 and Clause 5, test forces of one-third, two-thirds and the
36、 maximum specified S value for the noseweight gauge under test are applied and the results indicated by the noseweight gauge are analysed for conformance with 3.2.3.6.2 Apparatus6.2.1 test rig, with a suitable means of force application so that it is not subjected to any additional forces or moments
37、 apart from an S value commensurate with the maximum specified for the noseweight gauge under test.6.2.2 noseweight gauge.6.3 Initial inspection of the noseweight gaugePrior to the start of the test, check the noseweight gauge for any deformation. If there is any deformation, do not proceed with the
38、 test.6.4 ProcedureApply each force to the noseweight gauge. Note the reading of each force.BS 7961:20046 BSI 27 January 20046.5 Final inspection of the noseweight gaugeCheck the noseweight for any deformation.6.6 Expression of resultsRecord the weight of each test force and the reading taken from t
39、he noseweight gauge. Calculate the variance between each applied force and the indicated reading taken from the noseweight gauge.6.7 Test reportThe test report shall include:a) reference to this British Standard, i.e. BS 7961:2004;b) the result of the test in accordance with 6.4;c) the date of the t
40、est;d) where the test took place.BS 7961:2004 BSI 27 January 20047Bibliography 1 Directive 94/20/EC of the European Parliament and of the Council of 30 May 1994 relating to the mechanical coupling devices of motor vehicles and their trailers and their attachment to those vehicles. Official Journal L
41、 195, 29/07/1994, p. 00010060.2 UNECE (Economic Commission for Europe of the United Nations) Regulation No. 55, Agreement Concerning the Adoption of Uniform Conditions of Approval and Reciprocal Recognition of Approval for Motor Vehicle Equipment and Parts. Geneva, 20 March 1958.BS 7961:2004BSI389 C
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