Document ID: chunk:federal_register_of_legislation:F2021C00434:body:0:p44
Version: federal_register_of_legislation:F2021C00434
Segment Type: other
Provision Reference: 
Character Range: 127174–130048

the discretion of the type approval authority, be checked under the influence of a failure in any individual unit by applying corresponding output signals to electrical units or mechanical elements in order to simulate the effects of internal faults within the unit.

         4.1.2.1.              The verification results shall correspond with the documented summary of the failure analysis, to a level of overall effect such that the safety concept and execution are confirmed as being adequate.

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Appendix 2 - Attachment 5

         The following is a modified form of Appendix 2 to Annex 6 of UNECE Regulation No. 13-H– UNIFORM PROVISIONS CONCERNING THE APPROVAL OF PASSENGER CARS WITH REGARD TO BRAKING, incorporating supplement 7 and corrigendum to supplement 7 of the 00 series of amendments.

UTILIZATION OF ADHESION

         1.  METHOD OF MEASUREMENT

         1.1.  Determination of the coefficient of adhesion (k)

         1.1.1.  The coefficient of adhesion (k) shall be determined as the quotient of the maximum braking forces without locking the wheels and the corresponding dynamic load on the axle being braked.

         1.1.2.  The brakes shall be applied on only one axle of the vehicle under test, at an initial speed of 50 km/h.  The braking forces shall be distributed between the wheels of the axle to reach maximum performance.  The anti-lock system shall be disconnected, or inoperative, between 40 km/h and 20 km/h.

         1.1.3.  A number of tests at increments of line pressure shall be carried out to determine the maximum braking rate of the vehicle (zmax).  During each test, a constant input force shall be maintained and the braking rate will be determined by reference to the time taken (t) for the speed to reduce from 40 km/h to 20 km/h using the formula:

                  zmax is the maximum value of z; t is in seconds.

         1.1.3.1.  Wheel lock may occur below 20 km/h.

         1.1.3.2.  Starting from the minimum measured value of t, called tmin , then select three values of t comprised within tmin and 1.05 tmin and calculate their arithmetical mean value tm ,

           then calculate:

           If it is demonstrated that for practical reasons the three values defined above cannot be obtained, then the minimum time tmin may be utilized.  However, the requirements of paragraph 1.3. shall still apply.

         1.1.4.  The braking forces shall be calculated from the measured braking rate and the rolling resistance of the unbraked axle which is equal to 0.015 and 0.010 of the static axle load for a driven axle and a non-driven axle, respectively.

         1.1.5.  The dynamic load on the axle shall be that given by the denominator in the formulae shown in paragraph 1.1.8. below;

         1.1.6.  The value of k shall be rounded to three decimal places.

         1.1.7.  Then, the test will be