TANZANIA STANDARD MEDC 9 (3861) P 2

Transcription

1 TANZANIA STANDARD MEDC 9 (3861) 2 DRAFT TANZANIA STANDARD MEDC 9 (3861) 2 MOTORCYCLE AND SCOOTER TYRES - SECIFICATION TANZANIA BUREAU OF STANDARDS 1

2 0. Foreword The motorcycle and scooter tyres are currently very useful on running motorcycle in our country, in this regard the need of putting forward the right specifications to harmonize the performance is of paramount importance. The standard is set to provide safe operational performance for motorcycle and scooter tyres and to place sufficient information on the tyres to permit their proper selection and use. In the preparation of this draft standard, the assistance derived from the relevant publications of the International Organization for Standardization and the Bureau of Indian Standards. 1. SCOE 1.1 This draft standard prescribes the requirements and methods of sampling and test for motorcycle and scooter tyres. 1.2 erformance of on road requirement of the tyres is not covered in this draft standard. 2. REFERENCES For the purpose of this draft standard the following reference shall apply TZS 4: Rounding off numerical values ISO 37: Methods of testing vulcanized rubber - Determination of tensile stressstrain properties. ISO 24153: Random sampling and randomization procedures ISO : Definitions of some terms used in the tyre industry art 1: neumatic tyres. MEDC 9 (3642) - Motorcycle tyres and rims (Code-designated series) -- art 1: Tyres MEDC 9 (3643) - Motorcycle tyres and rims (Code-designated series) -- art 2: Tyre load ratings ISO : Motorcycle tyres and rims (Code-designated series) -- art 3: Rims ISO : Motorcycle tyres and rims (Code-designated series) Diameter codes 4 to 12 part 1 - Tyres ISO : Motorcycle tyres and rims (Code-designated series) Diameter codes 4 to 12 part 2s - Rims ISO :2004 Motorcycle and rims (metric series) art 1 Design guides 2

3 ISO :1983 Motorcycle and rims (metric series) art 2 Tyres dimension and load carrying capacities ISO :1983 Motorcycle and rims (metric series) art 3 Range of approved rim contour 3. DEFINITIONS For the purpose of this draft standard, the definitions given in ISO 4223 part 1, shall apply. 4. REQUIREMENTS 4.1 Tyre size designation The tyre size designation for motor cycle and scooter tyres shall be as given in ISO 5751 and ISO Dimensions The dimensions and profiles of tyres shall be compatible with appropriate rims When measured in accordance with the method described in Annex A, the overall width and overall diameter shall comply with ISO 6054 and ISO Load ratings The load carrying capacities and speed categories of tyres shall be as given in ISO Tyre endurance When tested in accordance with the method described in Annex B, the tyre, when cut and examined shall show no evidence of broken cords, separation of tread, ply, cord or bead or cracking of the tread or sidewall rubber exposing the cord fabric 4.5 Tyre strength When tested in accordance with the method described in Annex C the tyre shall comply with the static breaking energy requirements given in Table 1. 3

4 TABLE 1 - Requirement for static breaking energy SI No. (1) Tyre size designation (2) Speed category (3) Maximum speed Km/h (4) Test inflation pressure kpa (5) Requirement for static breaking energy, Nm, min Nylon (6) Rayon (7) i) ii) As in ISO 5751 and ISO 6054 a)standard load b) Extra load As in ISO 5751 and ISO 6054 a)standard load L L b) Extra load High speed performance When tested in accordance with the method described in Annex D, the Tyre, when cut and examined shall show no evidence of broken cords, separation of tread, ply, cord or bead or cracking of the tread or sidewall rubber exposing the cord fabric. 4.7 Skid depth When measured in accordance with the method described in Annex E, the skid depth shall comply with the values given in Table 2. 4

5 Table 2 Requirement for skid depth S/ No. Nominal section width, in Speed category Maximum speed, km/h Requirement for skid depth, mm, min. (1) (2) (3) (4) (5) i) ii) iii) iv) v) and Above L L L hysical properties of tread and sidewall rubber When tested in accordance with the method given in column 5 of Table 3, the tread and sidewall rubber shall comply with the requirements given in columns 3 and 4. Table 3 Requirement for tread and sidewall rubber S/N o. (1) Characteristic (2) Requirements Tread rubber (3) Sidewall rubber (4) Method of test (5) i) Tensile strength, Ma, min ISO 37 ii) Elongation at break, per cent, min ISO Life span of the tyre Tyre covered under this standard shall have shelf life of not more than five year since manufacturing date. 5

6 5. MARKING The tyres shall be marked legibly and indelibly with the following on both sidewalls (a) Tyre size designation as given in ISO 6054 (b) Load carrying capacity and speed symbol as given in ISO 4249 (c) Name of the manufacturer and/or registered trade mark including the country or origin, and (d) Batch or code number and. (e) Manufacturing date 6. SAMLING 6.1 Lot In any consignment all the tyres of the same size and type and belonging to one batch of manufacture or supply shall constitute a lot. 6.2 Scale of sampling Samples shall be tested from each lot for ascertaining its conformity to the requirements of this specification The number of tyres to be selected from a lot shall be in accordance with Table 4. Table 4 Scale of sampling Number of tyres in the lot (1) Number of tyres to be selected (2) Up to to Over

7 6.2.3 Tyres shall be selected at random. 6.3 Number of tests Each tyre selected as in clause shall be inspected for marking (clause 5) and dimensional requirements (clause 4.2) The sample selected as in clause shall be divided into subsamples of equal size. The tyres in one subsample so obtained shall be tested separately for tyre endurance (clause 4.4), the tyres of another subsample shall be tested separately for tyre strength (clause 4) and the tyres in the remaining subsample shall be tested separate for high speed performance (clause 4.6) One tyre shall be selected from the lot and tested for to requirements given in clause 4.7 and clause METHODS OF TEST Tests shall be carried out as prescribed in Annexes A to E of this draft standard. 8. CRITERIA FOR CONFORMITY A lot shall be declared as conforming to the requirements of this draft standard if the following conditions are satisfied. 8.1 Each tyre examined as in clause satisfies the relevant requirements. 8.2 The tyres tested as in clause satisfy the relevant requirements. 8.3 The tyre tested as in clause satisfies the relevant requirements. 7

8 A.1 reparation and conditioning ANNEX A MEASUREMENT OF DIMENSIONS Mount the tyre, on the specified rim and inflate to the pressure recommended for the maximum load for the size and type. Allow the tyre to remain in this condition for a minimum of 24 hours at room temperature. Check the inflation pressure and readjust if necessary, to the original value. A.2 rocedure A.2,1 Overall width Caliper the mounted tyre (see A. 1) at six points, spaced approximately equidistant from each other all around the circumference Measure the linear distance between the outermost positions over the twoside walls. Calculate the arithmetic mean of the six readings to the nearest millimeter NOTE All measurements should be taken over the maximum width to include any elevation due to protective ribs, bars, engraved sidewall markings or decorations A.2.2 Overall diameter Measure the outside circumference of the mounted tyre (see A.1) at the outermost surface of the tread, which is normally at a position along the circumferential centerline of the tread region Calculate the overall diameter as follows:- D o = C/π where, Do is the overall diameter in millimetres; and C is the circumference of tyre tread in millimetres. 8

9 ANNEX B DETERMINATION OF TYRE ENDURANCE B.l AARATUS Apparatus as shown in Figure 1, with a flat, smooth-faced steel drum(test wheel) having diameter of 1710 mm with a tolerance of +1 percent and a surface width more than the tread width of the loaded tyre. B.2 reparation and conditioning Figure 1 Apparatus for tyre endurance test Mount the tyre after ensuring that it exhibits no visual evidence of tread, sidewall, ply, cord or bead separation, broken cord or cracking, on a test rim of appropriate size and inflate to the appropriate pressure MEDC 9 (3643) (clause 6). Condition the tyre/rim-wheel assembly at room temperature for a minimum period of 3 hours. Readjust the tyre pressure to the original inflation pressure immediately before the test B.3 rocedure B.3.1 ress the mounted tyre (see B.2) against the test wheel. Run the tyre at each of the test load specified in Table 5 for the corresponding duration at the relevant speed. NOTE At the end of each run recorded the inflation pressure. Record the first reading of the inflation pressure 3 hours after the start of the test. If the subsequent readings of the inflation pressure fall below the first reading, rectify the cause of the pressure drop and adjust to the fist value while the tyre is at the running temperature. No corrective action is necessary if there is a normal rise in the inflation pressure. Record the inflation pressure immediately after completion of the test. 9

10 Table 5 Test loads and speeds Tyre size designation Speed category Maximum speed, km/h Test Inflation ressure, Kpa Test Speed Km/h Load Kg Stage 1 Stage 2 Stage 3 Duration h Load Kg Duration h Load Kg Duration h (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) As in ISO 6054 L As in MEDC 9 (3643) 48 As in MEDC 9 (3643) 7 Increase By 8 per cent 16 Increase By 8 per cent 24 As in MEDC 9 (3643) 64 As in MEDC 9 (3643) 4 Increase By 8 per cent 6 Increase By 8 per cent 24 B.3.2 on completion of the test cut and examine across section of the tyre for broken cord, separation of tread, ply, cord or bead or cracking of the tread or sidewall rubber exposing the cord fabric 10

11 ANNEX C DETERMINATION OF TYRE STRENGTH (LUNGER TEST) C.1. AARATUS Apparatus as shown in Figure 2, consisting of a cylindrical steel plunger with a hemispherical end (8 ± 0.2 mm in diameter) and a device to force this plunger into the tyre at the specified rate of travel. Figure 2 Apparatus for tyre strength test C.2 reparation and conditioning Mount the tyre, inflate and condition as in B. 2 C.3 rocedure Force the plunger rod into the tyre tread of the mounted tyre/rim wheel assembly, perpendicularly over a tread element at the centre of the tread or as near as possible to it avoiding penetration into tread groove at a rate of travel of the plunger 50 ± 3 mm per minute until the tyre breaks. Measure the force and penetration at break a points nearly equally spaced around the tyre circumference, necessary after repairing broken points and re-inflation. If the plunger is stopped by the rim (bottoming of the plunger again the rim) at all 5 11

12 points, the tyre is deemed to have passed the test regardless of the energy value. C.4 Calculation Static Breaking Energy, Nm = F x x 10 3 Where, 2 F is the arithmatic mean force at break in Newton and is the arithmatic mean of penetration at break or bottoming milimetre 12

13 ANNEX D DETERMINATION OF HIGH SEED ERFORMANCE D1 Apparatus As given in B.1 D.2 reparation and Conditioning As given in B.2. D.3 rocedure D.3.1 ress the mounted tyre against the test wheel with the force specified in Column 4 of Table 6. Run the tyre for the breaking period given in Table 6. Allow to cool to room temperature for period of not less than 2 hours. Adjust the inflation pressure to initial value. Run the tyre successively at the speeds given in columns 9, 11 and 13 of Table 6 for the relevant periods given therein. 13

14 Table 6 Test loads and speeds Tyre size designa tion Speed Category Test Inflation ressure Kpa Load Kg Maximum Speed, Km/h Breaking in period Stage 1 Stage 2 Stage 3 Duration h Speed, Km/h Duration h Speed, Km/h Duration h Speed, Km/h Duration h Speed, Km/h (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) As in ISO 6054 L As in MEDC 9 (3643) 90% of the load given in MEDC 9 (3643) /2 90 1/ / /2 1/ /2 140 D.3.2 On collection of the test, allow the tyre to cool at room temperature for about one hour. Cut and examine for broken cord separation of tread, ply, cord or bead or cracking of the tread sidewall rubber exposing the cord fabric. 14

15 ANNEX E MEASUREMENT OF SKID DETH E.1 rocedure Mount and condition the tyre as in A.I. For circumferentially groove, types, measure to the nearest 0.01 mm the depth of the tread groove nearest to or on the tread centerline of the tyre at six points equally spaced around the tyre outside circumference. (see Figure 3). For tyres with tread having cross grooves only and no circumferential grooves, measure the depth of the tread groove just outside the point of intersection of radius above the groove base and that through the tip end of the cross grooves blending into the base of the grooves (see Figure 4) Do not take into account any subsidiary shallow grooves at or beyond the cross grooves towards the centerline of the tyre tread. Figure 3 - Skid depth for circumferentially grooved types Figure 4 - Skid depth for cross grooved types 15