Document ID: chunk:federal_register_of_legislation:F2010C00150:front:0:p33
Version: federal_register_of_legislation:F2010C00150
Segment Type: other
Provision Reference: 
Character Range: 89138–92068

velocity of each wheel

(4) Brake torque at each wheel

         (5) Hydraulic line pressure in each brake circuit, including transducers on at least one front wheel and one rear wheel downstream of any operative proportioning or pressure limiting valve(s)

(6) Vehicle deceleration.

         (h) Sample  rate:  All  data  acquisition  and  recording  equipment  shall  support  a minimum sample rate of 40Hz on all channels .

         (i) Determination of front versus rear brake pressure: Determine the front versus rear brake pressure relationship over the entire range of line pressures. unless the vehicle has a variable brake proportioning system, this determination is made by static tests. If the vehicle has a variable brake proportioning system, dynamic tests are run with the vehicle both laden and unladen. Fifteen snubs from 50km/h are made for each of the two load conditions, using the same initial conditions specified in this appendix.

4. DATA REDUCTION

         (a) The data from each brake application prescribed in paragraph 3. (e) above is filtered using a five-point, on-centre moving average for each data channel.

         (b) For each brake application prescribed in paragraph 3. (e) above, determine the slope (brake factor) and pressure axis intercept (brake hold-off pressure) of the linear least squares equation best describing the measured torque output at each braked wheel as a function of measured line pressure applied at the same wheel. Only torque output values obtained from, data collected when the vehicle deceleration is within the range of 0.15g to 0.80g are used in the regression analysis.

         (c) Average the results of paragraph (b) above to calculate the average brake factor and brake hold-off pressure for all brake applications for the front axle.

         (d) Average the results of paragraph (b) above to calculate average brake factor and brake hold-off pressure for all brake applications for the rear axle.

         (e) Using the relationship between front and rear brake pressure determined in paragraph 3. (i) above and the dynamic tyre rolling radius, calculate the braking force at each axle as a function of front brake line pressure.

         (f) Calculate the braking rate of the vehicle as a function of the front brake line pressure using the following equation:

          where z =braking rate at a given front brake line pressure

         T1 , T2=braking forces at the front and rear axles respectively, corresponding to the same front brake line pressure

    P=vehicle mass

         (g) Calculate the adhesion utilized at each axle as a function of braking rate using the following formulae:

    The symbols are defined in paragraph 2. of this annex.

         (h) Plot f1 and f2 as a function of z, for both laden and unladen load conditions. These are the adhesion utilisation curves for the vehicle, which must satisfy the requirements in