Document ID: chunk:federal_register_of_legislation:F2021C00476:body:0:p51
Version: federal_register_of_legislation:F2021C00476
Segment Type: other
Provision Reference: 
Character Range: 141765–145107

on the high-adhesion surface

ki                                         k - value determined on axle i for a vehicle with a category 3 anti-lock system

kL                                         k - value determined on the low-adhesion surface

klock                                      value of adhesion for 100 per cent slip

kM                                         k - factor of the power-driven vehicle

kpeak                                      maximum value of the curve "adhesion versus slip"

kr                                         k - factor of one rear axle

P                                          mass of individual vehicle (kg)

R                                          ratio of kpeak to klock

t                                          time interval (s)

tm                                         mean value of  t

tmin                                       minimum value of  t

z                                          braking rate

zAL                                        braking rate z of the vehicle with the anti-lock system operative

zm                                         mean braking rate

zmax                                       maximum value of  z

zMALS                                      zAL of the power-driven vehicle on a "split surface"

Annex 6 - Appendix 2

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 brakes.

         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 formulae in Annex 5 to this Regulation.

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

         1.1.7.  Then,