BRITISH STANDARD AUTOMOBILE SERIES BS AU 50 1 2 3 1993 ISO 9948 1992 Tyres and wheels — Part 1 Tyres — Section 2 Commercial vehicle tyres — Subsection 2 3 Method of measuring rolling resistance UDC [6[.]
BRITISH STANDARD AUTOMOBILE SERIES BS AU 50-1 2.3:1 993 ISO 9948:1 992 Tyres and wheels — Part : Tyres — Section 2: Commercial vehicle tyres — Subsection 2.3 Method of measuring rolling resistance UD C [62 1 / ] 5 : 45 83 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy BS AU 0-1 2.3:1 993 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Automobile Standards Policy Committee (AUE/- ) to Technical Committee AUE/4, upon which the following bodies were represented: Agricultural Engineers’ Association Automobile Association British Industrial Truck Association British Pressure Gauge Manufacturers’ Association British Rubber Manufacturers’ Association Bus and Coach Council Department of Transport Freight Transport Association Institute of Road Transport Engineers (Inc) Motor Cycle Industry’s Association of Great Britain Ltd Motor Industry Research Association National Tyre Distributors’ Association Retread Manufacturers’ Association Road Haulage Association Ltd Society of Motor Manufacturers and Traders Ltd This British Standard, having been prepared under the direction of the Automobile Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on Amendments issued since publication May 993 © BSI 2- 999 The following BSI references relate to the work on this standard: Committee reference AUE/4 Draft for comment 91 /71 575 DC ISBN 80 21 747 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy Amd No Date Comments BS AU 0-1 2.3:1 993 Contents Page Committees responsible Inside front cover National foreword ii Scope Definitions Test methods Test equipment Test conditions Test procedure Data interpretation Data analysis Annex A (normative) Test equipment tolerances Annex B (informative) Optional test conditions Annex C (informative) Measurement methods of moment of inertia for drum and tyre assembly — Deceleration method Figure — Free- body diagram of tyre/drum system, assuming © BSI 2- 999 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy no bearing and windage losses Figure C — Arrangement Figure C — Spring method Figure C — Bifilar pendulum (rope) method Table B i BS AU 0-1 2.3:1 993 National foreword This Subsection of this Part of BS AU 50 has been prepared under the direction of the Automobile Standards Policy Committee It is identical with ISO 9948: 992 Truck and b us tyres — Metho ds o f m easuring rolling resistance, published by the International Organization for Standardization (ISO) Other Parts of this standard are as follows: — Part 2: Wheels and rim s; — Part 3: Valv es; — Part 4: Rim p rofiles and dim ensions 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 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 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 ii Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy © BSI 2- 999 BS AU -1 : 993 2.5 S cope This International Standard specifies methods for parasitic loss measuring rolling resistance, under controlled loss of energy (or energy consumed) per unit laboratory conditions, for new pneumatic tyres distance excluding tyre losses, and attributable to designed primarily for use on trucks and buses The aerodynamic loss, bearing friction and other sources relationship between values obtained and the fuel of systematic loss which may be inherent in the economy of the vehicle is undetermined, and such measurement values are not intended to be used to indicate levels 2.6 of performance or quality skim re ading This International Standard applies to all truck and type of parasitic loss measurement, in which the bus tyres tyre is kept rolling, without slippage, while reducing It enables comparisons to be made between the the tyre load to a level at which energy loss within rolling resistance of new tyres when they are the tyre itself is virtually zero free- rolling straight ahead, in a position perpendicular to the drum outer surface, and in steady- state conditions In measuring tyre rolling resistance, it is necessary to measure small forces in the presence of much larger forces It is, therefore, essential that 2.7 machine reading type of parasitic loss measurement, involving losses of the test machine, exclusive of losses in the rotating spindle which carries the tyre and rim equipment and instrumentation of appropriate 2.8 accuracy be used mome nt of ine rtia (see Annex C) D efinitions For the purposes of this International Standard, the Test methods following definitions apply The following alternative measurement methods 2.1 are given in this International Standard The choice rolling resistance, F of an individual method is left to the tester For each r loss of energy (or energy consumed) per unit of distance NOTE method, the test measurements shall be converted to a rolling resistance force acting at the tyre/drum interface The SI unit conventionally used for the rolling resistance is the newton metre per metre (N·m/m) This is equivalent to the drag force in newtons (N) 2.2 rolling resistance coe fficie nt, C r a) Force method: the reaction force at the tyre spindle b) Torque method: the torque input to the test drum ratio of the rolling resistance, in newtons, to the load c) Power method: the power input to the test on the tyre, in newtons This quantity is drum dimensionless and is derived as follows: d) Deceleration method: the deceleration of the C r = rolling resistance test load test drum and tyre assembly Test equipment 2.3 cappe d inflation process of inflating the tyre and allowing the D rum spe cifications 4.1 Diameter inflation pressure to build up, as the tyre is warmed The test dynamometer shall have a cylindrical up while running flywheel (drum) with a diameter of between , m 2.4 regulate d inflation process of inflating the tyre to the required pressure independent of its temperature, and maintaining and m inclusive It should be noted that the results are different; see for drum diameter correction for comparisons, if necessary 4.1 Surface this inflation pressure while the tyre runs under The surface of the drum shall be smooth steel or load This is most commonly done by using a textured, and shall be kept clean For the textured regulated pressure source attached to the tyre drum surface, see B through a rotating union (See Annex B ) © BSI 2- 999 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy BS AU -1 : 993 4.1 Width Test inflation p ressure The width of the drum test surface shall exceed the The inflation pressure shall be the inflation width or the test tyre tread pressure, specified by the tyre manufacturer concerned, corresponding to the maximum single tyre load capacity The inflation pressure shall be The tyre shall be mounted on a test rim, as specified capped with the accuracy specified in in Annex A When the deceleration method is selected, the following requirements apply: Measurement of these parameters shall be a) for duration, %t, the time increments shall not sufficiently accurate and precise to provide the exceed 0,5 s; required test data The specific and respective b) any variation of the test drum velocity shall not values are shown in Annex A exceed km/h Te st rim A D uration and velocity Load, alignme nt, control and instrume ntation accuracies The rmal e nvironme nt Reference conditions O ptional conditions the sensitivities of load, inflation or velocity The reference ambient temperature, as measured If are desired, the additional information given on the rotational axis or the tyre, m away from the in Annex B should be consulted plane touching the nearest tyre sidewall, shall be 25 °C Alternative conditions The test procedure steps described below are to be If the reference temperature cannot be obtained, the followed in the sequence given rolling resistance measurement shall be corrected to standard temperature conditions in accordance To ensure repeatability of measurements, an initial with break-in and cooling period is required prior to the Drum surface temperature start or the test Such a break-in should be carried Care should be taken to ensure that the out on a vehicle or on a test drum of at least 1,7 m in temperature of the test drum surface is diameter approximately the same as the ambient temperature at the beginning of the test Place the inflated tyre in the thermal environment of the test location for the time necessary to achieve thermal equilibrium which is generally reached The test consists of a measurement of rolling after h resistance in which the tyre is inflated and the inflation pressure allowed to build up (i.e., “capped air”) After thermal conditioning, the inflation pressure shall be adjusted to the test pressure and verified 10 after the adjustment was made Test speed for load index 122 and above The value shall be obtained at a drum speed The tyre shall be run at constant test velocity until of 80 km/h for tyres with speed symbols K to M inclusive and at 60 km/h for speed symbols F to J reaching a stabilized steady-state value of rolling resistance Recommendations for warm-up periods inclusive are given in Annex B Test speeds for load index 121 and below The values shall be obtained at drum speeds The following shall be measured and recorded of 80 km/h, and if required, 120 km/h (see Figure 1): a) test velocity, Un; The standard test load shall be computed from 85 % b) load on the tyre normal to the drum surface, of the maximum single load capacity of the tyre Lm ; and shall be kept within the tolerance specified c) test inflation pressure: in Annex A 1) initial, as defined in , 2) final, for capped inflation; 4.4.1 Test procedure 4.4.2 Break-in 4.4.3 Thermal conditioning Test conditions Pressure adj ustme nt Te st spe eds 5.1 Warm-up 5.1 Me asure me nt and re cording Test load Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy © BSI 12-1999 BS AU -1 : 993 T , the F , the input power, V × A, or d) the driving torque on the drive shaft, tyre spindle force, t t the deceleration of the test drum/tyre/wheel %Ê/%t, depending on the method; ); r (see ; f) ambient temperature, t g) test drum radius, R; assembly, e) distance, L amb h) test method chosen; i) test rim (designation and material) 6 Me asure ment of p arasitic losse s Determine parasitic losses by a procedure given in 6 , 6 6 or 6 Skim reading a) Reduce the load to maintain the tyre at the test velocity without slippage to, for example, 50 N b) Record the spindle force, F p input torque, T , or p the power, whichever applies c) Record the load on the tyre normal to the drum surface, 6 L p Machine reading a) Remove the tyre from the test drum surface U , record the input torque, T , the power, or the test drum deceleration, b) At the test velocity, n p whichever applies 6 Deceleration method Figure — Fre e -b ody diagram of tyre /drum system, assuming no b e aring and windage a) Remove the tyre from the test drum surface b) Record the deceleration of the test %Ê /%t, and that of the unloaded tyre, %Ê /%t drum, o po losse s Parasitic losses Calculate the parasitic losses, F , in newtons, as p D ata interpretation Sub traction of p arasitic losse s The parasitic losses shall be subtracted as shown in , 7.1 or Skim reading Subtract the skim reading from the test measurement 7.1 Machine reading Subtract the machine reading from the test where I is the test drum inertia in rotation, in D R Ê kilogram metres squared; is the test drum surface radius, in metres; vo %t is the test drum angular velocity, without tyre, in radians per second; o is the time increment chosen for the measurement of the parasitic losses measurement without tyre, in seconds; I T R Ê is the tyre and wheel inertia in rotation, in kilogram metres squared; r is the tyre rolling radius, in metres; po is the tyre angular velocity, unloaded tyre, in radians per second © BSI 2- 999 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy BS AU 0-1 2.3:1 993 Ê 7.2 Rolling resistance calculation The net values of driving torque, spindle force, F , expressed in newtons, using the Force method The rolling resistance, R M F t method is the distance from the tyre axis to the drum L R Data analysis outer surface under steady- state conditions, 8.1 Rolling resistance coefficient in metres; The rolling resistance coefficient, is the test drum radius, in metres dividing the rolling resistance by the load on the Torque method 7.2.2 The rolling distance, F , in newtons, is calculated Cr r T R F L where T R is the input torque, in newton metres; is the test drum radius, in metres Power method 7.2.3 The rolling resistance, = r F , in newtons, is calculated r drive, in amperes; is the test drum velocity, in kilometres per hour Deceleration method The rolling resistance, is the test load, in newtons are unavoidable (only temperatures not less than 20 ° C nor more than 30 ° C are acceptable) , r25 is the electric current drawn by the machine 7.2.4 m 8.2 Temperature correction F machine drive, in volts; n is the rolling resistance, in newtons; F r25 is the rolling resistance at 25 ° C, in newtons: is the electrical potential applied to the U r using the following equation, where where A m then a correction for temperature shall be made V× A U 3, n V Fr L = If measurements at temperatures other than 25 ° C with the equation F r where = r C , is calculated by tyre: with the equation F is as defined in 7.1 measure the moments of inertia for the deceleration is the tyre spindle force, in newtons; t P is the tyre aerodynamic torque; Annex C gives guidelines and practical examples to L where F r is the tyre rolling radius, in metres; AP r F = F [1 + (r /R) ] r kilogram metres squared; r F , in newtons, is calculated with the equation is the tyre and wheel inertia in rotation, in T r appropriate method, as shown in 7.2.1 to 7.2.4 7.2.1 tyre, in radians per second; I power or deceleration are to be converted to rolling resistance, is the test drum angular velocity, loaded v F , in newtons, is calculated r with the equation = F [1 + K(t r amb – 25)] where F t r amb K is the rolling resistance, in newtons; is the ambient temperature, in degrees Celsius; is equal to 0, 006 for truck and bus tyres with load index 22 and above, 0, 01 for truck and bus tyres with load index 21 and lower where I is the test drum inertia in rotation, in D R %t kilogram metres squared; is the test drum surface radius, in metres; v is the time increment chosen for the measurement, in seconds; Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy © BSI 2- 999 BS AU 0-1 2.3:1 993 8.3 Drum diameter correction Test res ults ob tained from different drum diameters may b e comp ared b y us ing the following theoretical formula: F Ò KF 02 r0 with where R R r F T r0 F r0 is the radius of drum , in metres ; is the radius of drum , in metres ; is the nominal tyre radius , in metres ; is the rolling res is tance value measured on drum , in newtons ; is the rolling res is tance value measured on drum , in newtons © BS I - 99 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy BS AU 50-1 2.3:1 993 Annex A (normative) Test equipment tolerances A.4 Control accuracy A.4.1 General accuracy Exclusive of perturbations induced by the tyre and rim non-uniformities, the test equipment shall be The limits specified in this annex are necessary in capable of checking the test variables within the order to achieve suitable levels of repeatable test following limits: results, which can also be correlated among various — tyre loading: ± 20 N test laboratories These tolerances are not meant to — inflation pressure: ± kPa represent a complete set of engineering — surface velocity: specifications for test equipment: instead, they should serve as guidelines for achieving reliable test ± 0,2 km/h for the power, torque and results deceleration methods, A.2 Test rims ± 0,5 km/h for the force method; A.2.1 Width — time: ± 0,02 s The test rim width shall be equal to the — angular velocity: ± 0,2 % standardized measuring rim If this is not available, A.4.2 Optional compensation for load/spindle then the next wider rim may be chosen It should be force interaction and load misalignment noted that a change in rim width will result in NOTE This compensation applies for the force method only different test results Compensation of both load/spindle force interaction A.2.2 Runout (“crosstalk”) and load misalignment may be Runout shall meet the following criteria: accomplished either by recording the spindle force for both forward and reverse tyre rotation or by — maximum radial runout: 0,5 mm dynamic machine calibration If spindle force is — maximum lateral runout: 0,5 mm recorded for forward and reverse directions (at each A.3 Alignment test condition), compensation is achieved by Angle deviations are critical to the test results subtracting the “reverse” value from the “forward” value and dividing the result by two If dynamic A.3.1 Load application machine calibration is intended, the compensation The direction of tyre loading application shall be terms may be easily incorporated in the data kept normal to the test surface and shall pass reduction through the wheel centre within — mrad for the force and deceleration methods; A.5 Instrumentation accuracy The instrumentation used for readout and recording — mrad for the torque and power methods of test data shall be accurate within the tolerances A.3.2 Tyre alignment stated below: A.3.2.1 Camber angle — tyre load: ± 10 N The plane of the tyre shall be normal to the test — inflation pressure: ± kPa surface within mrad for all methods — spindle force: ± 0,5 N A.3.2.2 Slip angle — torque input: ± 0,5 N·m The plane of the tyre shall be parallel to the — distance: ± mm direction of the test surface motion within mrad — electrical power: ± 10 W for all methods — temperature: ± 0,2 °C — surface velocity: ± 0,1 km/h (for all methods) — time: ± 0,01 s — angular velocity: ± 0,1 % A.1 Purpose Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy © BSI 12-1999 BS AU 50-1 2.3:1 993 A.6 Test surface roughness The roughness, measured laterally, of the smooth steel drum surface shall have a maximum centre- line average height value of 6, 4m Annex C (informative) Measurement methods of moment of inertia for drum and tyre assembly — Deceleration method A.7 Tyre spindle bearing friction When using the machine reading as a method for C.1 Limitation determining the parasitic losses, tyre spindle The methods presented here should be considered bearing friction should be regularly verified as being only as guidelines or practical examples of methods sufficiently small as to be considered negligible used to measure moments of inertia by the (e g , a coastdown from 80 km/h to km/h in not deceleration method to achieve reliable test results less than with a freely rotating tyre) C.2 Test drum inertia Annex B (informative) Optional test conditions C.2.1 Measurement method C.2.1 Equipment needed The arrangement shown in Figure C requires, in addition to the drum and its angular encoder: B.1 Purpose The rolling resistance of a tyre will vary with — a lightweight pulley mounted on low- friction velocity, load and inflation pressure, as well as other bearings; factors Depending upon the circumstances of — a weight of known mass, particular tyre applications, it can be useful to to 00 kg; determine the effect of these tyre- related parameters for the individual tyre to be tested If such information is desired, the options indicated — suitable wire rope and attachments C.2.1 Experimental arrangement in B.2 and B.3 are recommended Unless otherwise See Figure C noted, all aspects of the standard test conditions C.2.1 apply m , in the range 50 kg Theory Application of laws or mechanics to the system B.2 Speed sensitivity shown in Figure C leads to the following equation: A warm- up period of at least 90 for capped pressure conditions, and at least 30 for regulated pressure conditions is required B.3 Load and inflation sensitivity If load and inflation sensitivity is required, test in accordance with Table B , in a sequence which results in steadily decreasing values of rolling resistance For most tyres, the sequence shown accomplishes this obj ective A warm- up period of at least 90 for the first data point and at least 30 for each successive data point is required In cases where a textured drum surface is used instead of a smooth steel surface, this fact shall be noted in the test report The surface texture shall 4m deep (80 grit) Table B.1 Tyre load as a percentage Inflation pressure as a of maximum load percentage of rated pressure 00 00 is the pulley inertia, in kilogram metres P squared; r R I is the pulley radius, in metres; is the drum radius, in metres; is the drum inertia, in kilogram metres D squared; is the friction torque of drum bearings, in newton metres; g %Ê %t is the earth’s gravity equal to 9, 81 m/s ; D/ NOTE neglected is the angular acceleration or deceleration of the drum, in radians per second squared The friction torque of pulley bearings, c, can be 95 regulated 70 regulated 50 20 regulated 25 70 regulated © BSI 2- 999 is the mass, in kilograms; 00 capped 75 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy m I C B.4 Textured surface then be 80 where BS AU 0-1 2.3:1 993 Theory C.3.1 Equation of free movement of pendulum, if Ú is the angle from equilibrium: I Ú + KÚ = d2 d t Natural oscillation period, T: where Ú is the angle of oscillation, in radians; t I is the torsion pendulum inertia, in kilogram K is the spring constant is the period of time, in seconds; square metres; C.3.1 Figure C — Arrangement C.2.1 Method Method Measurement of oscillation periods, with the tyre assembly, m, is released, the angular When the mass, acceleration is measured through the angular T and without, tyre assembly inertia, I T = K T encoder fitted to the drum axle (and otherwise used ; ( – T I: T , call be used to give the o T ) Bifilar pendulum (rope) method to measure drum decelerations) C.3.2 The friction torque, Tyre inertia can be obtained by the period time of C, of drum bearings can also be measured, provided that the rope can be separated twisted oscillation of a tyre hanging from two steel from the drum once mass, ropes of exactly the same length (see Figure C 3) m , has given sufficient momentum to the drum, for the subsequent drum deceleration is directly related to %Ê I % t D D dec = C by: C C.3.2.1 Theory The tyre inertia, I , in kilograms metres squared, is T determined by where the values are as defined in C 2.1 C.2.2 Determination method The drum inertia is estimated by calculation The drum inertia, I , in kilogram metres squared, is D determined by the summation of the inertia of each drum part (flange, disc, reinforced rib): I D = I +I +I f d f is the drum flange inertia; d is the drum disc inertia; r is the reinforced rib inertia; all values being expressed in kilogram metres squared W a h is the oscillation period, in seconds; is the tyre and wheel weight, in newtons; is the distance between point A and B, in metres; is the distance between points C and D, in metres; is the vertical distance between lines AB and CD, in metres C.3.2.2 Method The time period, E, or the twisted oscillation of a tyre is measured, and tyre inertia can be calculated from C.3 Tyre assembly inertia C.3.1 E b r where I I I where the equation given in C.3.2.1 Spring method C.3.1 Equipment needed Torsion pendulum of inertia K (see Figure C 2) Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy I and spring constant © BSI 2- 999 BS AU 50-1 2.3:1 993 Figure C.2 — Spring method Figure C.3 — Bifilar pendulum (rope) method © BSI - 999 Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy BS AU 0-1 2.3:1 993 ISO 9948:1 992 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 make s ure that they p oss es s the latest amendments or editions It is the constant aim of BS I to imp rove the quality of our p roducts and services We would b e grateful if anyone finding an inaccuracy or amb iguity while us ing this Britis h S tandard would inform the S ecretary of the technical committee res p ons ib le, the identity of which can b e found on the inside front cover Tel: 02 89 96 90 00 Fax: 02 89 96 40 BS I offers memb ers an individual up dating s ervice called PLUS which ens ures that s ub s crib ers automatically receive the lates t editions of s tandards Buying standards O rders for all BS I, international and foreign s tandards p ub lications s hould b e addres s ed to C us tomer S ervices Tel: 899 00 Fax: 899 7001 In res p ons e to orders for international standards , it is BS I p olicy to sup p ly the BS I imp lementation of thos e that have b een p ub lis hed as Britis h S tandards, unless otherwis e requested Information on standards BS I p rovides a wide range of information on national, E urop ean and international standards through its Lib rary and its Technical H elp to E xp orters S ervice Various BS I electronic information s ervices are also availab le which give details on all its p roducts and s ervices C ontact the Information C entre Tel: 02 89 96 71 1 Fax: 02 89 96 048 S ub s crib ing memb ers of BS I are kep t up to date with s tandards develop ments and receive sub s tantial discounts on the p urchase p rice of s tandards For details of thes e and other b enefits contact Memb ership Adminis tration Tel: 02 89 96 70 02 Fax: 02 89 96 00 Copyright C op yright s ub s is ts in all BS I p ub lications BS I als o holds the cop yright, in the UK, of the p ub lications of the international s tandardization b odies E xcep t as p ermitted under the C op yright, D es igns and Patents Act 988 no extract may b e rep roduced, s tored in a retrieval s ystem or transmitted in any form or b y any means – electronic, p hotocop ying, recording or otherwis e – without p rior written p ermis s ion from BS I This does not p reclude the free us e, in the cours e of imp lementing the standard, of necess ary details such as s ymb ols, and size, typ e or grade designations If thes e details are to b e used for any other p urp os e than imp lementation then the p rior written p ermiss ion of BS I must b e ob tained If p ermis sion is granted, the terms may include royalty p ayments or a licensing agreement D etails and advice can b e ob tained from the C op yright Manager BS I 89 C his wick H igh Road London W4 4AL Reprodu ced by I H S u n d er l i cen se wi th BSI - U n trol l ed Copy Tel: 02 89 96 70