Document ID: chunk:federal_register_of_legislation:F2010C00150:front:0:p40
Version: federal_register_of_legislation:F2010C00150
Segment Type: other
Provision Reference: 
Character Range: 107402–110223

the low-adhesion surface

klock       value of adhesion for 100% 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 50km/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 40km/h and 20km/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 40km/h to 20km/h using the formula:

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

1.1.3.1. Wheel lock may occur below 20km/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, the test will be repeated for the other axle(s) as defined in paragraphs 1.1.1. to 1.1.6. above.

         1.1.8. For example, in the case of a two-axle rear-wheel drive vehicle, with the front axle (1) being braked,