BRITISH STANDARD AUTOMOBILE SERIES BS AU 150b 1984 (Superseding the first revision (1973) of BS AU 150) Specification for Automotive V belts and pulleys UDC 629 113 01 621 85 052 42 BS AU 150b 1984 Th[.]
BRITISH STANDARD AUTOMOBILE SERIES BS AU 0b:1 984 (Superseding the first revision (1 973) of BS AU 150) Specification for Automotive V-belts and pulleys UD C 62 1 : 62 85 42 BS AU 150b:1984 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Mechanical Engineering Standards Committee (MEE/- ) and the Automobile Standards Committee (AUE/- ) to Technical Committee MEE/76 upon which the following bodies were represented: Agricultural Engineers’ Association British Gear Manufacturers’ Association British Rubber Manufacturers’ Association National Coal Board Society of Motor Manufacturers and Traders Limited Coopted members This British Standard, having been prepared under the direction of the Automobile Standards Committee and the Mechanical Engineering Standards Committee, was published under the authority of the Board of BSI and comes into effect on 30 April 984 © BSI 02- 2000 Amendments issued since publication First published 966 First revision July 973 Second revision April 984 The following BSI references relate to the work on this standard: Committee reference MEE/76 Draft for comment 81 /80008 DC ISBN 580 13834 Amd No Date of issue Comments BS AU 150b:1984 Contents Page Committees responsib le Inside front cover Foreword iii Section General 1.1 Scope 1.2 D efinitions Section Belts D esignation 2 C ross section dimensions 2 E ffective length 2 Tolerances on nominal belt length Matched set tolerance Variation of belt cross section Variation of b elt ride- out Mean value of ride- out Belt test life E lectrical resistance 1 Resistance to ozone 2 Resistance to oil Hardness of rubb er core Resistance to low temperature 5 Resistance to high temperature Marking Section Pulleys D esign and construction D imensions 3 D esignation Surface of grooves C ast iron pulleys Axial and radial run- out Appendix A Information to be supplied b y the purchaser Appendix B Recommended nominal belt lengths Appendix C D etermination of b elt test life Appendix D D etermination of electrical resistance of belts 12 Appendix E D etermination of b elt resistance to ozone 13 Appendix F D etermination of belt resistance to oil 13 Appendix G D etermination of belt resistance to low temperature 14 Appendix H D etermination of b elt resistance to high temperature 14 Appendix J Measurement of run- out of pulleys 14 Appendix K Guidance and calculations for drive design 14 Figure — E ffective line differential Figure — Groove cross section of measuring fixture pulley Figure — Mean value f of b elt ride- out on measuring pulley Figure — Belt cross section Figure — Groove cross section of production pulley © BSI 02 - 000 Figure — Layout of measuring fixture Figure — Layout of test machine 11 Figure — Apparatus for measuring the electrical resistance of belts 13 Figure — Arrangement for radial run- out measurement 14 i BS AU 150b:1984 Page Figure — Arrangement for axial run- out measurement 14 Figure 1 — Layout of drive 16 Tab le — Nominal dimensions of b elt cross section Tab le — D imensions and characteristics of measuring fixture pulleys Tab le — Belt measuring force Tab le — D imensions and characteristics of pulleys Table — Recommended nominal b elt lengths for AV groove section Table — Recommended nominal b elt lengths for AV groove section Tab le — D imensions and characteristics of test pulleys 10 Table — Sequence of calculation 15 Tab le — Service factors for driven auxiliaries 17 Tab le — Arc of contact factor K Tab le 1 — Centrifugal tension factor Publications referred to ii K 17 17 Inside back cover © BSI 02 - 000 BS AU b : 984 Fore word This revision of this British Standard was prepared under the direction of the Automobile Standards Committee and the Mechanical Engineering Standards Committee The obj ect is to provide standard dimensions, quality control test procedures and design data for automotive V- belts and their corresponding pulleys, based on practical experience of both manufacturers and users This revision supersedes the 973 edition which is withdrawn In this standard requirements for the pulley groove profile are specified but requirements for the fit of the belt in the groove are only specified for the purposes of length measurement and accurate speed ratio determination Nominal dimensions of belts are specified solely for information for users and no requirements are given for belt performance This standard is technically equivalent to ISO 2790: 974 and ISO 5287: 978, published by the International Organization for Standardization (ISO), but, whereas ISO 2790 uses the “pitch” width of the belt system this standard uses the “effective width” of the pulley system 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 o mp liance with a British S tandard doe s not o f itse lf confe r immunity fro m le gal ob ligations S ummary o f p age s This document comprises a front cover, an inside front cover, pages i to iv, pages to 8, 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 © BSI 02- 2000 iii iv blank BS AU b: 984 Section General NOTE The effective line differential is used to obtain pitch diameters from the effective diameters and hence calculate the speed ratio S cope 2.7 This British Standard specifies the nominal cross section dimensions for V- belts and the design and construction of the corresponding pulleys used for driving the auxiliaries of automotive power units and their derivatives V-b e lt an endless flexible belt having a cross section that approximates to a regular trapezium On a cross section of a straight sided belt, the trapezium is outlined by the base, sides and top of the belt The Recommended nominal belt lengths are given in intersection of the extended profiles of the base, Appendix B Appendix K gives guidance on the sides and top occurs when the corners are cut short calculations for drive design or rounded This standard does not specify requirements for belt performance NOTE 2.8 V-b e lt drive The titles of the publications referred to in this standard are listed on the inside back cover a drive comprising one or more belts mounted on V- grooved pulleys The profiles of the belts and the pulley grooves are such that the belts only come into D efinitions For the purposes of this British Standard the following definitions apply contact with the sides of the pulley grooves and not with the base of the grooves 2.9 2.1 spe e d ratio V-groove d p ulle y a pulley with one or more grooves around the circumference The grooves have profiles of a truncated, non- truncated or rounded “V” that is symmetrical to the pulley axis the ratio of the number of revolutions of the pulleys, calculated from the ratio of the pitch diameters of the pulleys 2.1 top width, 2.2 e ffe ctive width, W W the larger width of the trapezium outlined on a cross e a groove width dimension characterizing the groove section (see Figure 5) profile It is a defined value not subj ect to tolerance 2.1 (see Figure ) he ight, NOTE the height of the trapezium outlined on a cross For all belt measuring pulleys, the effective width coincides with the actual top width of the groove within the specified tolerances e ffe ctive diame ter, d e the diameter of the pulley at the effective width of the pulley groove (see Figure and Figure 6) angle , A the included angle obtained by extending the side of the belt (see Figure 5) 2.1 2.4 pitch diameter the effective diameter corrected for the effective line differential NOTE section (see Figure 5) 2.1 2.3 T This calculation makes no allowance for slip and creep effective length, L e the length of a line circumscribing a belt at the effective diameter of the measuring pulleys 2.1 ride -out 2.5 pitch width, W p the width of the belt at its neutral axis (see Figure ) the distance from the top of the belt to the effective width level of the pulley 2.1 2.6 groove angle , effe ctive line diffe rential the radial displacement between the levels of the effective width of the pulley and the pitch width of the belt (see Figure ) NOTE a the included angle obtained by extending the sides of the pulley grooves (see Figure and Figure 6) NOTE For any given belt section the pulley groove angle will have a value dependent on the effective diameter of the pulley When the effective line differential is zero, the pitch width of the belt and the effective width of the pulley are coincident © BSI 02- 2000 BS AU b :1 984 Method of me asure me nt 2.1 effe ctive circumfe rence , C e 2.3.2.1 Measuring fixture The measuring fixture the circumference of a circle with a diameter equal shall consist of two pulleys with dimensions as to the effective diameter shown in Table and layout as shown in Figure 2, with a groove section as shown in Figure 3, and with one pulley centre fixed The other pulley shall be Section Belts moveable in a plane at right angles to the axes of the pulleys and in a line with the grooves of the pulleys D esignation Belts shall be designated by the groove profile in which they are intended to be run as AV or AV and by their nominal effective length The pulleys shall be fully rotatable and a means of applying a measuring force shall be provided 2.3.2.2 Pro cedure Mount the belt on the measuring fixture (2 ) and position in the grooves under C ross section dimensions The nominal cross section dimensions and the nominal included angle shall be as given in Table General NOTE any measurements, so that the measuring force F is equally divided between the two strands of the belt Determine the effective length E ffective length L e (in mm) of the belt from the following equation: The effective length shall be measured in accordance with the forces given in Table Rotate the pulleys at least twice to seat the belt properly, before making 2.3.2 No requirements are specified for effective length: these should be specified by the purchaser [see Appendix A a) ] L e = 2C + C e where C is the centre distance of the measuring pulleys (see Figure 2) (in mm) ; C e is the effective circumference of one measuring pulley (see Table 2) (in mm) Figure — E ffe ctive line differe ntial © BSI 02- 2000 BS AU 50b:1 984 Table — Nominal dimensions of belt cross section Belt designation Top width AV 10 AV 13 10 13 W Height mm 10 T mm Included angle A mm 40 40 NOTE The nominal cross section dimensions are in accordance with those given in ISO 2790 NOTE This figure is diagrammatic only Figure — Layout of measuring fixture Table — Dimensions and characteristics of measuring fixture pulleys Belt designation AV 10 AV 13 Diameter of Distance between Effective Effective Effective Groove Groove balls/rollers for external tangent width diameter circumference angle depth checking pulley plane of groove balls/rollers We mm 9.7 12.7 De mm 95.5 ± 0.2 300 95.5 ± 0.2 300 a Ce mm AV 10 AV 13 Measuring force F 270 270 N 2.4 Tolerances on nominal belt length The tolerance on nominal belt length shall be ± 0.6 % or ± mm, whichever is the greater NOTE Appendix B gives a range of recommended nominal belt lengths 2.5 Matched set tolerance mm 36 ± 0.2 11.0 36 ± 0.2 13.5 Table — Belt measuring force Belt designation degrees p d mm ± 0.01 12 ± 0.01 Ke mm 103.77 ± 0.05 107.25 ± 0.05 2.6 Variation of belt cross section The variation of the belt cross section shall be such that, when the belt is rotated slowly for at least one complete revolution of length on the measuring fixture described in 2.3.2.1 , the pulley centre distance shall not vary by more than 1.0 mm 2.7 Variation of belt ride-out Except for variations due to fabric splices or brand identifications, the variation in the belt ride-out shall be not more than 1.0 mm when the belt is rotated slowly for at least one complete revolution of length on the measuring fixture described in 2.3.2.1 NOTE Variations due to fabric splices or brand identifications In order to avoid an uneven distribution of load, should be ignored belts used on a multi-belt drive shall be length matched The maximum variation in length within 2.8 Mean value of ride-out a matched set shall be 0.2 % or mm, whichever is The mean value f of the ride-out (see Figure 4) for the greater the belts given in Table and Table shall not exceed 1.6 ± 0.8 mm © BSI 02-2000 BS AU 0b:1 984 Figure — Groove cross section of measuring fixture pulley 2.9 Belt test life Belt test life shall be determined in accordance with Appendix C NOTE Appendix C determines the belt test life only No requirements are specified for service behaviour and life: this should be specified by the purchaser [see Appendix A b) ] 2.1 Electrical resistance For new, complete, endless and anti- static belts the electrical resistance (in 7), when determined in accordance with Appendix D, shall be not greater than the following: L × 10 I where L Figure — Mean value f of belt ride-out on measuring pulley I T A NOTE is the dry distance between electrodes (in mm); is the sum of the lengths of the two sloping sides of the belt (in mm) = T sec (A/2) is the height; is the included angle (see Figure 5) For general information on electrical resistance of conductive and anti- static products made from flexible polymeric material see BS 2050 © BSI 02- 2000 BS AU b :1 984 Tab le — D ime nsions and characte ristics of p ulle ys Pulle y de signation E ffe ctive W width Groove angle re late d to da e ffe ctive diame te r e mm e Groove C e ntre to d e p th ce ntre of D iame te r o f b e low groove s, me asuring effe ctive minimum b alls/rolle rs line distance p 4° 36° 38° mm mm mm mm e mm D istance fro m e ffe ctive diame te r to the e xte rnal tange nt of b alls/rolle rs, at X d mm groove angle e 34° 6° mm mm 9.0 ± 0.01 4.03 4.14 ± 0.08 ± 0.08 8° mm 4.24 ± 0.08 AV 10 9.7 56 to 70 70 to 180 180 11.0 12.0 + 0.3 – 0.0 AV 13 12.7 70 to 90 80 to 180 180 13.5 5.87 5.99 15.0 + 0.3 12.0 ± 0.01 5.75 – 0.0 ± 0.08 ± 0.08 ± 0.08 a The effective diameter for a particular section is dependent on the belt construction used The purchaser should request the manufacturer to supply this information The values given are recommended values If different angles of a pulley are required, the groove flanks should hinge about the effective line Figure — Groove cross section of p roduction pulley © BSI 02-2000 BS AU 50b:1 984 3.4 Surface of grooves The s urface finis h of grooves s hall b e not more than m R a when determined b y the method 3.6 Axial and radial run-out When meas ured in accordance with Ap p endix J the axial run- out of a machined p ulley on its shaft s hall des crib ed in BS 1 4- The groove surface of s teel not exceed 00 mm p er millimetre of p ulley p ulleys s hall have a hardnes s of not les s diameter or mm, whichever is the greater than H B when tested in accordance with BS 40- 3.5 Cast iron pulleys C ast iron used for p ulleys shall b e clos e- grained and free from p oros ity Machined p ulleys s hall have no b lowholes in the groove © BS I - 00 The axial run- out of a p res sed, s p lit or unmachined p ulley on its shaft shall not exceed mm When meas ured in accordance with Ap p endix J the radial run- out of the p ulley on its s haft s hall not exceed mm The diameter of the b alls or rollers used shall b e not less than thos e given in Tab le BS AU b : 984 Ap p e ndix A Information to b e App e ndix B Recomme nde d nominal sup p lied b y the p urchaser b e lt le ngths The following particulars cover essential details to Tab le — Re co mme nde d nominal b e lt le ngths be given to the belt manufacturer by a purchaser so that an enquiry or order may be fully understood: a) effective belt length required (see for AV groo ve se ction E ffe cti ve le ngth E ffe ctive le ngth ); Pre ferre d No n p re fe rre d Pre fe rre d mm mm mm No n p re fe rre d b) service behaviour and life and requirements for belt test life (see ); c) whether the belt is to be marked with the purchaser’s part number (see ); d) allowance for percentage change in volume for determination of resistance to oil (see ); e) hardness required by the purchaser (see ); f) whether pulleys are required to be balanced g) dimensioned drawing of the application, power 075 638 1 00 088 113 650 663 1 25 688 1 50 71 1 75 738 200 1 38 675 1 63 700 requirements, speeds and adj ustable take- ups required for the belt (see Appendix K) 61 625 (see note to section 3); 1 88 725 21 750 763 225 788 250 81 275 838 300 238 775 263 800 288 825 31 850 863 325 888 350 91 375 938 400 338 875 363 900 388 925 41 950 963 425 988 450 01 475 038 500 438 975 463 000 488 025 050 mm 063 600 51 © BSI 02- 2000 BS AU b : 984 Tab le — Re comme nd e d no minal b e lt le ngths for AV groo ve se ction E ffe ctive le ngth Ap p endix C D e te rmination of b e lt te st life E ffe cti ve le ngth C Introduction Pre ferre d No n p re fe rre d Pre fe rre d No n p re fe rre d mm mm mm mm 775 788 800 813 825 838 850 863 875 888 900 913 925 938 950 963 975 000 025 050 075 100 125 150 175 200 225 250 275 988 013 038 063 088 113 138 163 188 213 238 263 288 © BSI 02-2000 300 325 350 375 400 425 450 475 500 525 550 575 600 625 650 675 700 725 750 775 800 313 338 363 388 413 438 463 488 513 538 563 588 613 638 663 688 713 738 763 788 This test determines belt test life for the purpose of quality control product verification and comparative testing It is generally in accordance with the test given in ISO 5287 Since the introduction of V-type belts on automotive drives, automotive engine and belt manufacturers have employed laboratory and field tests for product development, source approval and quality verification It is generally agreed that the test given in ISO 5287 and in this appendix is the best that has been developed, but this does not imply that other testing, such as field testing, should be circumvented C Princip le To determine the belt test life in hours by fatigue testing under specified conditions on a three-pulley test machine C Ap p aratus as shown diagrammatically in Figure 7, consisting of the following a) A driving pulley and suitable driving unit b) A driven pulley to which a suitable absorption unit is connected c) An idler pulley and arrangement through which tension can be supplied to the belt d) A means of determining belt slip to an accuracy of ± % C Dynam ic three- p ulley test m achine, NOTE This can be determined, for example, by electronic digital counting or by calibrating the instrument used for measuring belt slip and checking periodically by electronic digital counting The test machine shall be of such a robust design that it will meet the following requirements 1) The general layout of the pulleys relative to each other shall be as shown in Figure A belt shall be run-in for under dead-weight conditions and dial indicators shall then be positioned, as shown in Figure 7, on the pulley flange furthest away from the bearing in each case 2) For AV 10 belts a tension of 490 N shall be applied at the idler pulley and a tension of 590 N for AV 13 belts The minimum idler pulley diameter (see note to Table 7) and the corresponding groove angle (see Table 7) shall be used for the respective cross sections 3) The maximum deflection for each pulley irrespective of belt section used shall be 0.25 mm BS AU b : 984 4) The power absorption unit shall be capable of maintaining the test load to within ± 0.1 kW for the duration of the test and shall be capable of calibration, e.g by dead weights In order that tension can be satisfactorily applied to the belt and so as to allow for belt stretch the idler pulley and its bearing assembly shall be free to slide, as and when necessary, in its support bracket along the line of application of the tensioning force, as shown in Figure 5) In order to accommodate different lengths of belts, the relevant driving pulley and/or the relevant driven pulley and the position of the idler pulley and/or its support bracket shall be adjustable so that the test layout of the three pulleys is attainable for each belt length 6) The line of action of the tensioning force shall bisect the belt layout angle at the idler pulley (see Figure 7), shall pass through the axis centre of the idler pulley and shall lie in the plane through the centre of the groove of the idler pulley The pulleys shall be made from a direct-hardening steel equivalent to steel 708M40, as specified in BS 970-1, and the pulley groove shall have a surface condition such that the surface condition shall not vary by more than 0.8 4m a, when determined in accordance with BS 1134-1 C.3.2 Test p ulleys R NOTE For appropriate dimensions and characteristics for belts and pulleys see Table and Table respectively C Te st conditions For each test, the general layout of the pulleys relative to each other shall be as shown in Figure 7, the centre distance (in mm) between the driving and driven pulleys being within ± mm of the value determined by the following equation: 2.414 = – 0.785 (3 + ) – ( – ) where is the centre distance between the driving and driven pulleys (in mm); is the effective length of the belt measured in accordance with (in mm); is the diameter of both the driving and driven pulleys (in mm); is the diameter of the idler pulley (in mm) The test speed, i.e the rotational speed of the driving pulley, shall be 900 r/min ± % for AV 10 belts and 700 r/min ± % for AV 13 belts The test load (in N) applied to the idler pulley shall be such that = where is the test load (in N); = 60 N/kW; is the transmitted power (in kW) C.4.2 Layout o f p ulleys C L D d D d C L 2.3.2 D d C.4.3 Test sp eed C.4.4 Tes t load N Kx N K x NOTE The recommended power for this test is 8.2 kW for AV 10 belts and 10.0 kW for AV 13 belts The ambient temperature of the test house shall be between 18 °C and 32 °C and the mean ambient temperature for the duration of the test shall be given with the result of the test The atmosphere in the vicinity of the test drive shall be free of draughts resulting from sources other than the test machine itself C.4.1 Test hous e Tab le — D ime nsions and characte ristics o f te st p ulle ys Pu lle y d e signatio n E ffe cti ve Gro o ve angle o f E ffe ctive Gro o ve E ffe cti ve Mi ni mu m Mi ni mu m d i ame te r o f d ri ving/d ri ve n di ame te r o f angle o f wi d th o f gro o ve cu rve rad i u s d ri vi ng/d rive n p u lle ys i d le r p ulle y i d le r p u lle y p ulle y d e p th o f sid e s at to p p u lle ys D e mm µ degrees AV 10 121 ± 0.2 36 ± 0.5 AV 13 127 ± 0.2 36 ± 0.5 e o f gro o ve gro o ve W d e mm 56 63 ± 0.5 76 70 76 ± 0.2 89 a degrees 34 34 ± 0.5 36 34 34 ± 0.5 34 mm p R mm mm 9.7 11.0 0.8 12.7 13.75 0.8 NOTE These dimensions and characteristics are appropriate for the sizes of belts given in Table NOTE The diameter of the idler pulley should be agreed between the manufacturer and the purchaser and will be dependent upon the conditions of use envisaged for the belt 10 © BSI 02-2000 BS AU b : 984 Turn the drive manually for several revolutions of C Proce dure C.5.1 Prep aration After mounting the belt on the pulleys, apply the test load (C ) to the belt and, the belt and note the maximum limits of travel of the idler pulley on the dial indicator leaving the idler pulley support bracket free to move Immediately lock the idler pulley support bracket in in its slide, bring the drive up to the test the position midway between the two limits of speed (C ) and apply the test load to the driven travel pulley as quickly as possible Run the drive under these conditions for ± s, not including starting and stopping time Stop the machine and leave it to stand for NOTE 45 ° is recommended for the initial test layout and this may change slightly with re- tensioning during the course of the test NOTE It is essential that the misalignment of the belt, when mounted on the test machine, is not more than ± 25 ° in relation to the plane through the centre of each pulley groove NOTE This figure is diagrammatic only Figure — Layout of te st machine © BSI 02- 2000 11 BS AU b : 984 Restart the machine, bring the drive up comprising a conducting to the test speed ( ), apply the test load ( ) liquid consisting of the following: to the driven pulley and measure the slip between the driving and the driven pulleys Run the drive a) anhydrous polyethylene glycol of continuously under these conditions until either the relative molecular mass 600 800 belt fails or the additional slip exceeds %, when b) water 200 determined as follows: c) soft soap in accordance with BS 1913 o – f × 100 = -d) potassium chloride 10 o preferably made of where brass, 25 mm wide, constructed with a V-groove and with an included angle appropriate to the belt under p test Metal contacts shall be clean (see Figure 8) o = q of B.P grade r f = C Test D Liq uid electrodes, C.4.3 C.4.4 Ratio g i i g i D Metal contacts, N i N D Dry fuller’s earth N i D Cotton w oo l p ad s N is the initial speed of the driven shaft; is the initial speed of the driving shaft; q r is the final speed of the driven shaft; s is the final speed of the driving shaft If the additional belt slip reaches % before belt failure, stop the machine and let it stand for at least 20 Unlock the idler pulley support bracket, apply the test load to the belt, turn the drive manually two or three times, re-lock the idler support bracket and repeat the test described in Repeat this re-tensioning procedure whenever the additional slip exceeds % until the belt fails Record the number of running hours under test to belt failure, the number of belt re-tensions, the diameter of the idler pulley and the mean ambient temperature during the test p N N N N C Re- tensioning C.5.2 C Records D Distilled w ater D Me chanical cond itioning After being strained under the conditions specified in , maintain the belt in the unstrained state at a temperature between 15 °C and 25 °C for a period of not less than 24 h 2.3.2 D Pre p aratio n fo r te st After mechanical conditioning as described in , store the belt for not less than h at a temperature of 20 ± °C in air with a relative humidity of less than 70 % Clean the surfaces which are to be used in the test with the dry fuller’s earth ( ) using a clean pad of cotton wool ( ) and take care to avoid straining the belt After all traces of powder have been cleaned away, wipe the surfaces over with a cotton wool pad moistened with distilled water ( ) and rub dry with a clean cloth D.4 D.3.4 D.3.5 D.3.6 Ap p endix D D e termination of D Proce d ure e le ctrical resistance of b elts D Prep aration o f liq uid electro des and contacts After the preparation of the belt for test in accordance with , apply the liquid ) to two areas of the belt, each To determine the electrical resistance of belts using electrodes ( extending 25 mm along the length of the belt, and an insulation tester under specified limits of across the full width of the surfaces which make humidity and temperature contact with the pulley groove and located so that the dry distance between them is 100 ± mm The test shall be carried out on new, complete Keep the electrode area completely wet until the end endless belts of the test Apply the clean metal contacts ( ) to the wetted having a nominal areas of the belt so that only the driving surfaces of open-circuit voltage of 500 d.c or any suitable the belt are in contact Apply a force of N/mm to instrument known to give comparable results The top width of the belt to press it into the V-groove to test instrument shall be sufficiently accurate to ensure adequate electrical contact (see Figure 8) determine resistance to within % and shall not dissipate more than W in the belt under test D Princip le D.5 D.3.2 D Te st p ie ce s D Ap p aratus D.3.3 D Ins ulation tes ter, 12 © BSI 02-2000 BS AU b : 984 Figure — Ap p aratus for me asuring the e le ctrical re sistance of b e lts Ensure that the surfaces of the belt not deform during the application of the contacts or during the test After mechanical conditioning and preparation, apply the liquid electrodes and metal contacts, as described in , to the belt In no case shall the voltage applied to the belt be less than 40 V D 6.2 Tes t D.6.1 NOTE Non compliance with the maximum limit of resistance specification in can be established only at the specified upper limits of temperature and humidity (see ) Compliance can be verified at any permissible testing temperature and humidity at which the resistance is below the specified limit 2.1 Ap p endix E D e te rmination of b elt re sistance to oz one Secure a test piece taken from a belt, without being masked, around a 50 mm diameter mandrel so that maximum strain occurs in the outer fibres of the belt Age the test piece for 24 h at 20 ± 20° Expose the test piece to an ozone concentration of 0.0025 % / (2 500 p.p.m.) at 38 ± °C for 40 h in a test cabinet in accordance with BS 903-A43 V V D.5 D Numb e r of te sts At least five tests shall be made on different areas of the belt, spaced so that the tests will be representative of the whole belt No individual test result shall be greater than that specified in 2.1 © BSI 02-2000 Ap p e ndix F D e te rmination of b elt re sistance to oil Follow the procedure for the volumetric method described in BS 903-A16 using oil no for the test liquid Immerse the test piece for 72 h at 70 ± 10 °C Record the percentage change in volume 13 BS AU 0b:1 984 Appendix G Determination of belt resistance to low temperature Age a belt in its natural shape for 24 h at – 30 ± 20 °C While still at – 30 °C bend the belt in the same direction as the natural curvature in stages around a pulley of the same dimensions as the minimum effective diameter idler pulley given in Table The belt shall flex easily Allow the belt to return to room temperature and flex the same belt backwards around a 75 mm diameter mandrel Appendix H Determination of belt resistance to high temperature Age a belt in its natural shape for 70 h at 100 ± °C Allow the belt to return to room temperature and flex the belt backwards around a 75 mm diameter mandrel Appendix J Measurement of run-out of Figure — Arrangement for axial run-out measurement Appendix K Guidance and calculations for drive design K.1 Arrangement and geometry of drive of reverse acting idler pulleys Where practicable, the component having the smallest should be located on the slack side of Measure the axial and radial run-out separately as the drivepulley to avoid concentrating the greatest the total indicator reading of the movement of a ball bending tension and the tightside tension a at the or roller of diameter not less than that given in same pulley Table Profile mount the indicator arm under spring pressure to follow the groove as the pulley is It is also desirable to locate the weakest component on the slack side of the drive It is essential that rotated (see Figure and Figure 10) outside acting idlers should not be located on the tightside of the drive The geometry of the drive should avoid a small arc of contact of the belt on any heavily loaded pulley Elastic mountings should be avoided pulleys T K.2 Pulley alignment It is essential to align pulleys accurately so that the belt is within 0.5° misalignment to prevent groove jumping if “flutter” occurs on sudden acceleration or deceleration of down-shifting K.3 Sequence of calculation amplified The sequence of calculation is given in Table and is further amplified as follows a) Identify pulleys from the layout given in Figure 11 Pulleys are numbered from crank and/or driving pulley opposite to the direction of rotation b) This is taken from purchaser information and should be corrected for the service factor where appropriate (see Table 9) c) The effective diameters of the pulleys may be used for an initial assessment of speed ratio (within % of the true ratio) For an accurate assessment of the ratio, the effective diameter has to be corrected by the effective line differential (see 2.6) Pulleys Po w er W Figure — Arrangement for radial run-out measurement Pulley diam eter d 14 © BSI 02-2000